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SIMPLE WG A. Houri
Internet-Draft IBM
Intended status: Informational E. Aoki
Expires: August 28, 2008 AOL LLC
S. Parameswar
T. Rang
Microsoft Corporation
V. Singh
H. Schulzrinne
Columbia U.
February 25, 2008
Presence Interdomain Scaling Analysis for SIP/SIMPLE
draft-ietf-simple-interdomain-scaling-analysis-04.txt
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Copyright Notice
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Abstract
The document analyzes the traffic that is generated due to presence
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subscriptions between domains. It is shown that the amount of
traffic can be extremely big. In addition to the very large traffic
the document also analyzes the affects of a large presence system on
the memory footprint and the CPU load. Current approved and in work
optimizations to the SIP protocol are analyzed with the possible
impact on the load. Separate documents contain the requirements for
optimizations and suggestions for new optimizations.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Message Load . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Known Optimizations . . . . . . . . . . . . . . . . . . . 5
2.2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 6
2.3. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.1. Constants . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2. Initial Messages . . . . . . . . . . . . . . . . . . . 10
2.3.3. Steady State Messages . . . . . . . . . . . . . . . . 10
2.3.4. Termination Messages . . . . . . . . . . . . . . . . . 12
2.3.5. Bottom Line . . . . . . . . . . . . . . . . . . . . . 12
2.3.6. Rush Hour Calculations . . . . . . . . . . . . . . . . 13
2.4. No optimizations used . . . . . . . . . . . . . . . . . . 13
2.5. Dialog optimization used . . . . . . . . . . . . . . . . . 15
2.6. NOTIFY optimization used . . . . . . . . . . . . . . . . . 17
2.7. Dialog & NOTIFY optimizations used . . . . . . . . . . . . 19
2.8. Presence Federation Scenarios . . . . . . . . . . . . . . 21
2.8.1. Widely distributed inter-domain presence . . . . . . . 22
2.8.2. Associated inter-domain presence . . . . . . . . . . . 26
2.8.3. Very large network peering . . . . . . . . . . . . . . 27
2.8.4. Intra-domain peering . . . . . . . . . . . . . . . . . 31
2.9. Partial Notifications Optimization . . . . . . . . . . . . 36
2.10. Very Optimized SIP . . . . . . . . . . . . . . . . . . . . 38
3. State Management . . . . . . . . . . . . . . . . . . . . . . . 41
3.1. State Size Calculations . . . . . . . . . . . . . . . . . 41
3.1.1. Tiny System . . . . . . . . . . . . . . . . . . . . . 42
3.1.2. Medium System . . . . . . . . . . . . . . . . . . . . 42
3.1.3. Large System . . . . . . . . . . . . . . . . . . . . . 42
3.1.4. Very Large System . . . . . . . . . . . . . . . . . . 42
4. Processing complexities . . . . . . . . . . . . . . . . . . . 43
4.1. Aggregation . . . . . . . . . . . . . . . . . . . . . . . 44
4.2. Partial Publish and Notify . . . . . . . . . . . . . . . . 44
4.3. Filtering . . . . . . . . . . . . . . . . . . . . . . . . 44
4.4. Authorization . . . . . . . . . . . . . . . . . . . . . . 45
4.5. Resource List Service . . . . . . . . . . . . . . . . . . 45
5. Current Optimizations . . . . . . . . . . . . . . . . . . . . 46
6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 53
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8. Security Considerations . . . . . . . . . . . . . . . . . . . 54
9. Changes from Previous Versions . . . . . . . . . . . . . . . . 55
9.1. Changes in version 04 . . . . . . . . . . . . . . . . . . 55
9.2. Changes in version 03 . . . . . . . . . . . . . . . . . . 55
9.3. Changes in version 02 . . . . . . . . . . . . . . . . . . 55
9.4. Changes in version 01 . . . . . . . . . . . . . . . . . . 56
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 56
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 56
11.1. Normative References . . . . . . . . . . . . . . . . . . . 56
11.2. Informational References . . . . . . . . . . . . . . . . . 56
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 58
Intellectual Property and Copyright Statements . . . . . . . . . . 60
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1. Introduction
The document analyzes the SIP protocol for presence (AKA SIMPLE but
SIMPLE is not a different protocol then SIP but the name of the
working group). It analyses the traffic that is generated due to
presence subscriptions between domains. It is shown that the number
of messages and the amount of data can be extremely big. In addition
to the very large traffic the document also analysis the affects of a
large presence system on the memory footprint and the CPU load.
Current approved and in work optimizations to the SIP protocol are
analyzed with the possible impact on the load. Another document
provides requirements for optimizations [20] while other documents
contain suggestions for new optimizations: [21]. [23]
This document is intended to be drive work on possible solutions that
will make the deployment of a SIP based presence server less
challenging task. Deployment of highly scalable presence systems is
challenging by its nature and each protocol developers design their
own technique for optimizing their protocol. This document does not
try to compare between protocols and it is behind the scope of this
document.
The document discusses the following areas. In each area we try to
show the complexity and the load that the presence server has to
handle in order to provide its service.
o Messages load - By computing the number of messages that are
required for connecting presence systems the document shows that
the number of messages is very big and it is quite obvious that
some optimizations are needed. In addition we also show that the
bandwidth required is also very big.
o State management - Due to the nature of the service that the
presence server provides, the presence server has to manage a
relatively big and complex state and some computations are
provided in the document.
o Processing complexities - The presence server maintains many small
objects and has to do frequent operations on these objects. We
show that these operations and especially the optimizations that
are intended to save on the amount of data that is being sent
between watchers and presence servers, are not so simple and may
create a very heavy processing load on the presence server.
o Groups - Resource List Servers [11] optimize the number of
sessions that are created between the watchers and the presence
server. On the other hand, this optimization may create an
exponential size of subscription due to the unbearable ease of
subscribing to large groups.
The term presence domain or presence system appears in the document
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several time. By this term we refer to a SIP based presence server
that provides presence subscription and notification services to its
users. The system can be a system that is deployed in a small
enterprise or in a very large consumer network.
2. Message Load
Some optimizations are approved or are being defined for the SIP
presence protocol, but even with these optimizations a very large
number of messages & large bandwidth are needed in order to establish
federation between presence systems of large communities. Further
thinking is needed in order to make large deployment of presence
systems less resource demanding.
Note that even though this document talks about inter domain traffic,
the introduction of resource list servers (RLSs) [11] introduce very
similar traffic pattern in intra-domain and in inter-domain. See
detailed discussion on resource lists in Section 4.5.
2.1. Known Optimizations
The current optimizations that are approved or are approved as
working group items in the SIMPLE working group can be divided into
two categories:
o Dialogs saving optimization - Here we refer to optimizations as
the resource list RFC [11] or to the URI list subscriptions draft
[18]. These documents define ways to reduce the number of dialogs
that are required between the subscriber and the presence system.
Note that dialog optimization or RLS usage as it is used in
this document refers to the usage of a URI that represents a
list of a URI list between domains and not within the same
domain. An example is a user Alice in domain example.org that
subsides to URI of e.g. external-reps-list at example.com or
uses a URI list to subscribe at on her watch list in
example.com. Note also that when calculating the traffic that
is due to RLS within a domain the traffic between the RLS and
the presence agents should also be taken into account.
However, since in this document we are mostly dealing with
inter- domain traffic, the traffic between the RLS and the
presence agents was not taken into account.
o
Notification optimizations - Here we refer to the optimizations
that are suggested in the subnot-etags draft [19]. This draft
suggests ways to suppress the sending of unnecessary notifies when
for example a subscription is refreshed. There are other drafts
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that reduce the size of messages as partial notifications or
filtering but in this document we mostly care about the amount of
messages & bandwidth so the partial optimizations can help a bit
in the bandwidth but will not help in the number of messages.
In addition to the above optimizations another optimization could
have been considered but it is not taken into account in the
computations in this document. This optimization is the ability to
have some of the presence information received not by the SIP
protocol but by offline means as downloading some persistent presence
information directly from a web site or by some other offline means.
The calculations here are based on the assumption that all data is
carried in-bound of the protocol and no optimizations that enable
getting the presence information via out bound means are taken into
account. These optimizations may improve the number of messages and
number of bytes significantly but they are out of scope for this
document
2.2. Assumptions
In the document several assumptions are used regarding size of
messages, rate of presence change and more. It should be noted that
these assumptions are not directly based on rigorous statistics that
was done on actual SIP based deployments of presence systems but more
from some experience on other types of presence based systems.
The following numbers are given more as examples from real
deployments and they are not intended to be complete
In a large consumer network we have seen the following patterns:
o Approximately 110 users in the watch list in average.
o There are approximately 12 billion status changes a day (139k/
second) across the network. Of these, when a proprietary binary
protocol is used to convey the status changes the average of the
message is about 188 bytes. When SIP NOTIFY is used the average
is about 1228 bytes for the message.
o The average of logins/logouts in the system is about 2000 logins
per second and about 4000 logouts per second. When something
happens - either a promotion, contest, or a network hiccup that
causes many users to login and logout simultaneously, there are
about 20,000 logins per second.
o The peak of the instant messages sent is about 50,000 messages per
second.
In a deployment in enterprises we have seen the following patterns:
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o Averages watch list size was 200 users.
o About half of the registered users were online at peak time
o Status change per hour was 2 changes per hour.
o The average logins/logouts in the system was about 5 logins per
second with additional 15 logins/logouts during start/end of day
rush hours.
Even though the assumptions in this document are not based on
rigorous statistical data the target here is not to analyze specific
system but show that even with VERY moderate assumptions (which are
even less then the observations mentioned above), the number of
messages, the network bandwidth, the required state management and
the load on the CPU are very high. Real life systems should have a
much bigger scalability challenges. for example the presence state
change that we assumed (one presence state change per hour) is maybe
one of the most moderate assumptions that we have taken. Experience
from consumer networks show that the frequency here is much bigger
and especially with the younger generation that use more presence
attributes like mood etc.. In an environment where a user may have
several devices and other resources for presence information as
geographical location and calendar the frequency of presence state
changes will be much higher.
It is very hard to measure presence load since it is very much
dependent on the behavior of users and behavior of users differs a
lot. Some users will have a very small number of presentities in
their watch list while others may have hundreds if not thousands.
Some users will change their state a lot and have many sources of
presence information while others may have very small number of
changes during the day. In addition the "rush hour" calculations of
when the day starts and ends were not included yet in this document.
Rush hour differs between different enterprises and is still
different in the consumer presence systems. It is very hard if not
impossible to take into a static document all the possible
combinations.
Throughout the calculations certain number of users are assumed for
the different models. It does not mean that in actual deployments
all the users of the domain actually subscribed to presence documents
and/or publish their presence document. Observing actual deployments
shows that in the consumer market the number of users that use
presence services may be 10 percent or less of the registered users.
In the enterprise market numbers tend to be around 50 percent of the
actual enterprise registered users.
The same is correct for the number for of watched presentities per
watcher. if only some percent of the domain users are online at a
given time then this number should have been that percentage.
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However, trying to add this assumption to the calculations will make
the calculations more complex then they are since the affect of the
watched presentities that are not online will need to be taken into
account. This means that empty notify should be sent for those when
the subscription is created and there is no updates on them. In
order to make the computations less complex (they are complex enough
as they are), the number of the watched presentities that is used in
the calculations is the number of the federated presentities from the
watcher list that are online.
2.3. Analysis
The basic SIP subscription dialog involves the following message-
transfer:
o SUBSCRIBE/200
o Initial NOTIFY/200
o (j) NOTIFY/200 where 'j' is the number of presence changes seen by
the watcher
o (k) SUBSCRIBE/200 where 'k' is the number of subscription dialog
refresh periods
o SUBSCRIBE/200 with Expires = 0 to terminate the dialog
o NOTIFY/200 ending the dialog
An individual watcher will generate X number of SIP subscription
dialogs corresponding to the number of presentities it chooses to
watch. The amount of traffic generated is significantly affected by
several factors:
o Number of watchers connected to the system
o Number of presentities connected to the system
o Frequency of changes to presence information
This document contains several calculations that show the expected
message rate and bandwidth between presence domains. The following
sections explain the assumptions and methods behind the calculations.
2.3.1. Constants
The following are number of "constants" that we use in the
calculations. Some of the constants are used throughout the
calculation while other change between use cases
o (C01) Subscription lifetime (hours)- The assumed lifetime of a
subscription in hours. We assume 8 hours for all calculations.
o (C02) Presence state changes / hour - The average time that a
presentity changes his/hers status in one hour. We assumed 3
times per hour for most calculations. Note that for some users in
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consumer messaging systems, the actual number of changes is likely
to be much higher.
o (C03) Subscription refresh interval / hour - The duration of the
SUBSCRIBE session after which it needs to be refreshed. We
assumed that the duration is one hour.
o (C04) Total federated presentities per watcher - The number of
presentities that the watcher is watching. The number here
changes in this document according to the type of the specific
deployment.
o (C05) Number of dialogs to maintain per watcher - The number of
the SUBSCRIBE dialogs that are maintained per watcher. if a dialog
optimization is not assumed this number is equal to A04, otherwise
it is 1.
o (C06) Total number of watchers in the federated presence domains.
The number here is the number of all watchers in all the federated
domains.
o (C07) SUBSCRIBE message size in bytes. We assume 450 bytes in all
calculations. The size is based on a typical SUBSCIRBE taken from
RFCs.
o (C08) 200 OK for SUBSCRIBE message size in bytes. We assume 370
bytes in all calculations. The size is based on a typical 200 OK
taken from RFCs.
o (C09) NOTIFY message size not including the presence document.
The size of this message for a single presentity is assumed to be
500 bytes for the NOTIFY message itself (based on sizes from
examples in RFCs).
o (C10) 200 OK for NOTIFY message size in bytes. We assume 370
bytes in all calculations. The size is based on a typical 200 OK
taken from RFCs.
o (C11) Size of an average presence document. In the previous
version of this document we have used only the size of 3000 bytes
for a presence document. This number was calculated based on
examples of rich presence document in RFCs. Due to discussion in
the SIMPLE list where it was claimed that it may be too big and
due to the fact that we are talking here about federation between
communities where the rich presence document may be of less use,
we have done all the calculations with two sizes of presence
document. One size is the minimal size of the PIDF [6] document
which was taken to be 350 bytes based on examples from RFCs and
the other size is the 3000 bytes for rich presence document [7].
It should be noted that assuming 3000 bytes for presence document
is relatively modest if we take into account multiple devices and
location information.
o (C12) The size of NOTIFY when partial [14] notification is being
done. We have taken this size to be 200 bytes. The size is much
smaller then the example that is given in [14] but the example
given there assumes multiple changes in the presence document and
here we assume a single change.
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When dialog optimization [11] is used, an RLMI document is
being sent and that document contains the presence documents
for the users that are in the watch list. In previous version
of this document we have omitted the overhead of the RLMI
document. This "bug" was found by Victoria Beltran-Martinez
and is being fixed in this document by adding the constants
C13, C14 and C15 to the calculations
o
(C13) Item size per each contact in RLMI document, 160 bytes.
o (C14) The size of the multipart boundary (per each contact) in
RLMI notifications, 144 bytes.
o (C15) The size of the XML root node in RLMI document (once per
notification), 144 bytes.
2.3.2. Initial Messages
The following are the calculations for the messages in the initial
phase of the establishment of the subscriptions. The calculations
contain both number of messages and the number of bytes.
o (I01) Number of initial SUBSCRIBE messages per watcher = C05.
o (I02) Number of initial 200 OK messages for SUBSCRIBE messages per
watcher = C05.
o (I03) Number of initial NOTIFY messages per watcher = C05.
o (I04) Number of initial 200 OK messages for NOTIFY messages per
watcher = C05.
o (I05) Total number and bytes of initial SUBSCRIBE messages for all
watchers = Number - I01*C06, Bytes - I01*C06*C07.
o (I06) Total number and bytes of initial 200 OK for SUBSCRIBE
messages for all watchers = Number - I01*C06, Bytes - I01*C06*C08.
o (I07) Total number and bytes of initial NOTIFY messages for all
watchers = Number - I01*C06, The calculation for the number of
bytes is different when dialog optimization is used or not. When
dialog optimization is not applied the number of bytes will be
calculated by: (I01*C06*C09)+(I01*C06*C11) and when dialog
optimization is applied the number of bytes will be calculated by
(I01*C06*(C09+C14+C15))+(I01*C06*C04*(C11+C13+C14)).
o (I08) Total number and bytes of initial 200 OK for NOTIFY messages
for all watchers = Number - I04*C06, Bytes - I04*C06*C10.
o (I09) Total number and bytes of initial messages per day = Number
- numbers in I05+I06+I07+I08, Size -sizes in I05+I06+I07+I08.
2.3.3. Steady State Messages
Here we describe the calculations for the steady state messages.
Steady state is the time between the initial subscription and the
tear down of the subscription. It contains the notifies due to state
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change and the subscription refreshes.
o (S01) NOTIFY messages due to state change per watched presentity
per day (less 2 since the NOTIFY for initial and terminating state
is calculated in the initial and terminating calculations) =
(C02*C01-2).
o (S02) 200 (for NOTIFY due to state change) messages per watched
presentity per day (less 2 since the NOTIFY for initial and
terminating state is calculated in the initial and terminating
calculations) = (C02*C01-2).
o (S03) Total number and size of messages due to state change per
day = Number - (S01+S02)*C06*C04. The calculation for the number
of bytes is different when dialog optimization is used or not.
When dialog optimization is not applied the number of bytes will
be calculated by: (C06*C04)*((S01*(C09+C11))+(S02*C10)) and when
dialog optimization is applied the number of bytes will be
calculated by (C06*C04)*((S01*(C09+C11+C13+C14+C15))+(S02*C10)).
Note that for dialog optimization it is assumed that only a single
presentity is changed and partial state notification is used.
o (S04) Number of SUBSCRIBE messages for refreshes per watcher per
day = ((C01/C03)-1)*C05. One is subtracted since the termination
is calculated separately. for example if there are 8 hours in the
day and a refresh should occur every hour, there are 7 refreshes
during the day and not 8.
o (S05) Number of 200 OK messages for SUBSCRIBE messages for
refreshes per watcher per day = ((C01/C03)-1)*C05.
o (S06) Number of NOTIFY messages for refreshes per watcher per day
= ((C01/C03)-1)*C05. Since when NOTIFY optimization is used [19]
there is no need to send NOTIFY for refreshes, S06 will be zero
when NOTIFY optimizations is used.
o (S07) Number of 200 OK messages for NOTIFY messages for refreshes
per watcher per day = ((C01/C03)-1)*C05. Since when NOTIFY
optimization is used [19] there is no need to send NOTIFY for
refreshes, S07 will be zero when NOTIFY optimizations is used.
o (S08) Total number and size of messages due to SUBSCRIBE refreshes
per day = Number - (S04+S05+S06+S07)*C06. The number of bytes is
calculated by adding the SUBSCIRBE bytes (S04*C06*C07), the OK for
SUBSCRIBE bytes (S05*C06*C08), the NOTIFY bytes C06*(S06*(C09+
C11)) and the OK for NOTIFY (S07*C06*C10). Note that the formula
for the notify bytes is for the dialog optimization is not used
and when it used the formula will be: C06*(S06*((C09+C14+C15)+
(C04*(C11+C13+C14)))). Note that a full state should be given in
SUBSCRIBE refreshes in resource lists. See section 5.2 in [11].
The fact that the full state needs to be returned in a NOTIFY
response to refresh makes the NOTIFY optimization more efficient
in conjunction with the dialog optimization.
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o (S09) Total number and bytes of steady messages per day = Number -
numbers in S03+S08, Bytes - sizes in S03+S08.
2.3.4. Termination Messages
The following are the calculations for the messages in the
termination phase of the of the subscriptions. The calculations
contain both number of messages and the number of bytes.
o (T01) Number of terminating SUBSCRIBE messages per watcher = C05.
o (T02) Number of terminating 200 OK messages for SUBSCRIBE messages
per watcher = C05.
o (T03) Number of terminating NOTIFY messages per watcher = C05.
Since when NOTIFY optimization is used [19] there is no need to
send NOTIFY for terminations, T03 will be zero when NOTIFY
optimization is used.
o (T04) Number of terminating 200 OK messages for NOTIFY messages
per watcher = C05. Since when NOTIFY optimization is used [19]
there is no need to send NOTIFY for terminations, T04 will be zero
when NOTIFY optimization is used.
o (T05) Total number and bytes of terminating SUBSCRIBE messages for
all watchers = Number - T01*C06, Bytes - T01*C06*C07.
o (T06) Total number and bytes of terminating 200 OK for SUBSCRIBE
messages for all watchers = Number - T01*C06, Bytes - T01*C06*C08.
o (T07) Total number and bytes of terminating NOTIFY messages for
all watchers = Number - T01*C06, The number of bytes is calculated
to be: (T03*C06*(C09+C11) when dialog optimization is not used
and: (T03*C06*(C09+C11+C13+C14+C15) when dialog optimization is
used. Note that for dialog optimization it is assumed that only a
single presentity is changed and partial state notification is
used.
o (T08) Total number and bytes of terminating 200 OK for NOTIFY
messages for all watchers = Number - T04*C06, Bytes - T04*C06*C10.
o (T09) Total number and bytes of terminating messages per day =
Number - numbers in T05+T06+T07+T08, Size -sizes in T05+T06+T07+
T08.
2.3.5. Bottom Line
The following are the calculations of several totals that are based
on the above calculations.
o (B01) Total number of messages and bytes during the day = Messages
- Number of messages in I09+S09+T09, Bytes - Number of bytes in
I09+S09+T09.
o (B02) Total number of messages and bytes per second = Messages -
Number of messages in B01/(C01*3600) Bytes - Number of bytes in
B01/(C01*3600).
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o (B02) Total number of message and bytes per user per day =
Messages - number of messages in B01/C06 Bytes - Number of bytes
in B01/C06.
2.3.6. Rush Hour Calculations
With the way that the calculations are built, it is relatively easy
to see the affect of rush hours at the beginning and the end of the
day. for the beginning of the day we should look at the numbers of
"(I09) Total number and bytes of initial messages per day" and for
the end of the day we should look at the number of "(T09) Total
number and bytes of terminating messages per day". Taking these
numbers with some assumed percentage of the numbers of users that log
in at the same hour should give good indication for the rush hour
load.
2.4. No optimizations used
The following table uses some common presence characteristics to
demonstrate the effect these factors have on state and message rate
within a presence domain using base SIP protocols without any
proposed optimizations. In this example, there are two presence
domains with total of 40,000 federating users with an average of 4
contacts in the peer domain. Note that the main calculation is done
for a presence document size of 350 bytes which is the base PIDF [6]
document size but the bottom line calculation is also given for a
presence document size for rich presence [7] which is assumed to be
3000 bytes based on the examples given in the RFCs. This two folded
calculation is done for every use case in this document.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher................4
(C05) Number of dialogs to maintain per watcher...............4
(C06) Total number of watchers in domains................40,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................4
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............4
(I03) Initial NOTIFY msgs per watcher.........................4
(I04) Initial 200 OK msgs (NOTIFY) per watcher................4
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(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................72,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers....................136,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............640,000
Bytes for all watchers....................326,400,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers.............7,040,000
Bytes for all watchers..................4,294,400,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day................................28
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day................................28
(S06) Number of NOTIFY msgs for refreshes
per watcher per day................................28
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day................................28
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.....4,480,000
Bytes for all watchers per day..........2,284,800,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers............11,520,000
Bytes for all watchers..................6,579,200,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................4
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........4
(T03) Terminating NOTIFY msgs per watcher.....................4
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............4
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers.............. 160,000
Bytes for all watchers.....................72,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
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Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers....................136,000,000
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...............640,000
Bytes for all watchers....................326,400,000
** Bottom Line
(B01) Total of messages between domains..............12,800,000
Total of bytes between domains (PD=350).....7,232,000,000
Total of bytes between domains (PD=3000)...20,376,000,000
(B02) Total number of messages / second.. ..................444
Total of bytes per second (PD=350)................251,111
Total of bytes per second (PD=3000)...............707,500
(B03) Total number of by msgs per user/day......... ........320
Total number of bytes per user/day (PD=350).......180,800
Total number of bytes per user/day (PD=3000)......509,400
Figure 1: No optimizations used
2.5. Dialog optimization used
The same analysis provided above is repeated here with the assumption
that the dialog optimization is applied. Note that while the sign-in
(ramp up) and sign-out messages flows are positively affected, the
steady state rates are not.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher................4
(C05) Number of dialogs to maintain per watcher...............1
(C06) Total number of watchers in domains................40,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
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** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................1
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1
(I03) Initial NOTIFY msgs per watcher.........................1
(I04) Initial 200 OK msgs (NOTIFY) per watcher................1
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers................40,000
Bytes for all watchers....................136,160,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............160,000
Bytes for all watchers....................183,760,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers.............7,040,000
Bytes for all watchers..................5,871,360,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................7
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................7
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.....1,120,000
Bytes for all watchers per day..........1,286,320,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers.............8,160,000
Bytes for all watchers..................7,157,680,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................1
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1
(T03) Terminating NOTIFY msgs per watcher.....................1
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(T04) Terminating 200 OK msgs (NOTIFY) per watcher............1
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................51,920,000
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................99,520,000
** Bottom Line
(B01) Total of messages between domains...............8,480,000
Total of bytes between domains (PD=350).....7,440,960,000
Total of bytes between domains (PD=3000)...20,266,960,000
(B02) Total number of messages / second.....................294
Total of bytes per second (PD=350)................256,767
Total of bytes per second (PD=3000)...............702,114
(B03) Total number of by msgs per user/day..................212
Total number of bytes per user/day (PD=350).......186,024
Total number of bytes per user/day (PD=3000)......506,674
Figure 2: Dialog optimization used
2.6. NOTIFY optimization used
The initial analysis of analysis provided in Figure 1 is repeated
here with the assumption that the notify optimization is applied.
The optimization saves the need for NOTIFY upon refreshing a
SUBSCRIBE if there was no change since the last NOTIFY. It is
assumed here that there will be no NOTIFY message for a SUBSCRIBE
refreshes and terminations. As should be expected this optimization
affects the steady and termination state and does not affect the
initial state.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher................4
(C05) Number of dialogs to maintain per watcher...............4
(C06) Total number of watchers in domains................40,000
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(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................4
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............4
(I03) Initial NOTIFY msgs per watcher.........................4
(I04) Initial 200 OK msgs (NOTIFY) per watcher................4
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................72,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers....................136,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............640,000
Bytes for all watchers....................326,400,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers.............7,040,000
Bytes for all watchers..................4,294,400,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day................................28
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day................................28
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.....2,240,000
Bytes for all watchers per day............918,400,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers.............9,280,000
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Bytes for all watchers..................5,212,800,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................4
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........4
(T03) Terminating NOTIFY msgs per watcher.....................0
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers.............. 160,000
Bytes for all watchers.....................72,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............160,000
Bytes for all watchers.....................59,200,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...............320,000
Bytes for all watchers....................131,200,000
** Bottom Line
(B01) Total of messages between domains..............10,240,000
Total of bytes between domains (PD=350).....5,670,400,000
Total of bytes between domains (PD=3000)...15,422,400,000
(B02) Total number of messages / second.....................356
Total of bytes per second (PD=350)................196,889
Total of bytes per second (PD=3000)...............535,500
(B03) Total number of by msgs per user/day..................256
Total number of bytes per user/day (PD=350).......141,760
Total number of bytes per user/day (PD=3000)......385,560
Figure 3: NOTIFY optimization used
2.7. Dialog & NOTIFY optimizations used
Here both optimizations are combined. In all the subsequent use
cases we will show only the analysis with no optimizations and with
both optimizations combined.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher................4
(C05) Number of dialogs to maintain per watcher...............1
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(C06) Total number of watchers in domains................40,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................1
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1
(I03) Initial NOTIFY msgs per watcher.........................1
(I04) Initial 200 OK msgs (NOTIFY) per watcher................1
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers................40,000
Bytes for all watchers....................136,160,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............160,000
Bytes for all watchers....................183,760,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers.............7,040,000
Bytes for all watchers..................5,871,360,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
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Number of msgs for all watchers per day.......560,000
Bytes for all watchers per day............229,600,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers.............7,600,000
Bytes for all watchers..................6,100,960,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................1
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1
(T03) Terminating NOTIFY msgs per watcher.....................0
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers................80,000
Bytes for all watchers.....................32,800,000
** Bottom Line
(B01) Total of messages between domains...............7,840,000
Total of bytes between domains (PD=350).....6,317,520,000
Total of bytes between domains (PD=3000)...16,069,520,000
(B02) Total number of messages / second.....................272
Total of bytes per second (PD=350)................219,358
Total of bytes per second (PD=3000)...............557,769
(B03) Total number of by msgs per user/day..................196
Total number of bytes per user/day (PD=350).......157,938
Total number of bytes per user/day (PD=3000)......401,738
Figure 4: Dialog & NOTIFY optimizations used
2.8. Presence Federation Scenarios
While scalability issues exist in any large deployment, certain
characteristics make the deployment conducive to the existing
optimizations, and others have characteristics that do not.
Following is a list of federation scenarios that have varying usage
characteristics. For each, a message rate and bandwidth table is
provided reflecting typical changes message rates. Those
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characteristics can alter the overall effectiveness of existing
optimizations.
Note that the number of users used is not the number of the users in
the domains but the actual logged in users. As was mentioned before
not all the domain users will use the presence service at the same
time. The number used for number of watchers and number of watched
presentities are for online users.
2.8.1. Widely distributed inter-domain presence
In some environments presence federation may be very common, perhaps
even more common than intra-domain presence. An example of this type
of environment is a small ISV or public server. Users in that small
ISV are not likely to subscribe to the presence of other users in the
their server since they do not necessarily have any relationship with
each other aside from receiving service from the same provider. They
are much more likely to be subscribed to the presence of users in one
of the federated domains (whether in consumer domains, academic,
other ISVs, etc). Common characteristics of this deployment are:
o Federated subscriptions are the majority of subscription traffic
o Individual users are likely to subscribe to multiple users in any
one domain
o The intersection of users in the deployment watching the same
presentities is quite small (i.e., probability that watchers in
the domain subscribe to the same presentity is low)
To account for the extraordinarily high percentage of federation
traffic, the number of federated presentities is increased to 20.
The number of watchers in the domain could also be adjusted to
account for an expected larger community of users being peered with,
it is omitted here for simplification
The first table below provides the calculations without optimizations
the second table provides the calculations with optimization.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............20
(C05) Number of dialogs to maintain per watcher..............20
(C06) Total number of watchers in domains................40,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
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(C11) Size of an average presence document..................350
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher.....................20
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............20
(I03) Initial NOTIFY msgs per watcher........................20
(I04) Initial 200 OK msgs (NOTIFY) per watcher...............20
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................360,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................296,000,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................680,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................296,000,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers.............3,200,000
Bytes for all watchers..................1,632,000,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers............35,200,000
Bytes for all watchers.................21,472,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day...............................140
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day...............................140
(S06) Number of NOTIFY msgs for refreshes
per watcher per day...............................140
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day...............................140
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day....22,400,000
Bytes for all watchers per day.........11,424,000,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers............57,600,000
Bytes for all watchers.................32,896,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher.................20
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(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........20
(T03) Terminating NOTIFY msgs per watcher....................20
(T04) Terminating 200 OK msgs (NOTIFY) per watcher...........20
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................360,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................296,000,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................680,000,000
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............800,000
Bytes for all watchers....................296,000,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers.............3,200,000
Bytes for all watchers..................1,632,000,000
** Bottom Line
(B01) Total of messages between domains..............64,000,000
Total of bytes between domains (PD=350)....36,160,000,000
Total of bytes between domains (PD=3000)..101,880,000,000
(B02) Total number of messages / second...................2,222
Total of bytes per second (PD=350)..............1,255,556
Total of bytes per second (PD=3000).............3,537,500
(B03) Total number of by msgs per user/day................1,600
Total number of bytes per user/day (PD=350).......904,000
Total number of bytes per user/day (PD=3000).....,547,000
Figure 5: Widely distributed inter-domain with no optimizations
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............20
(C05) Number of dialogs to maintain per watcher...............1
(C06) Total number of watchers in domains................40,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
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** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................1
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1
(I03) Initial NOTIFY msgs per watcher.........................1
(I04) Initial 200 OK msgs (NOTIFY) per watcher................1
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers................40,000
Bytes for all watchers....................554,720,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............160,000
Bytes for all watchers....................602,320,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers............35,200,000
Bytes for all watchers.................29,356,800,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.......560,000
Bytes for all watchers per day............229,600,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers............35,760,000
Bytes for all watchers.................29,586,400,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................1
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1
(T03) Terminating NOTIFY msgs per watcher.....................0
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(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................18,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers................40,000
Bytes for all watchers.....................14,800,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers................80,000
Bytes for all watchers.....................32,800,000
** Bottom Line
(B01) Total of messages between domains..............36,000,000
Total of bytes between domains (PD=350)....30,221,520,000
Total of bytes between domains (PD=3000)...78,981,520,000
(B02) Total number of messages / second...................1,250
Total of bytes per second (PD=350)..............1,049,358
Total of bytes per second (PD=3000).............2,742,414
(B03) Total number of by msgs per user/day..................900
Total number of bytes per user/day (PD=350).......755,538
Total number of bytes per user/day (PD=3000)....1,974,538
Figure 6: Widely distributed inter-domain with optimizations
2.8.2. Associated inter-domain presence
In this type of environment, the domain is a collection of associated
users such as an enterprise. Here, federation is once again very
common. However, there is also a strong association between some
users in the deployment. These associations make it somewhat more
likely that users in that domain will be watchers of the same
presentity. This can occur because of business relationships (e.g.
two co-workers on a project federating with a partner company).
Common characteristics of this deployment are:
o Federated subscriptions are large minority or small majority of
subscription traffic
o Individual users are likely to subscribe to multiple users in any
one domain, especially their own
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o The intersection of users in the deployment watching the same
presentities increases
This federation type has traffic rates similar to the previous
examples but with different levels of association of the users.
2.8.3. Very large network peering
In this environment, two or more very large networks create a peering
relationship allowing their users to subscribe to presence in the
other domains. Where as the number of users in other deployment
types ranges from hundreds to several hundred thousand, these large
networks host up to hundreds of millions of users. Examples of these
networks are large wireless carriers and consumer IM networks.
Common characteristics of this deployment are:
o As users become accustomed to network boundaries disappearing,
federated subscriptions become as common as subscriptions within
the same domain
o Individual users are highly likely to want to see presence of
multiple presentities in the peer network
o The intersection of users in the deployment watching the same
presentities is very high (i.e., two or more users in network A
are extremely likely to be watching a same user in network B)
o Status changes increase greatly due to typical observed consumer
behavior
The first table below provides the calculations without optimizations
the second table provides the calculations with optimizations. Even
though the optimizations help a lot (almost cut the number of
messages by half), the numbers are still very high. Note also that
the bandwidth required is very high.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................6
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher..............10
(C06) Total number of watchers in domains............20,000,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
** Initial Messages
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(I01) Initial SUBSCRIBE msgs per watcher.....................10
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10
(I03) Initial NOTIFY msgs per watcher........................10
(I04) Initial 200 OK msgs (NOTIFY) per watcher...............10
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................90,000,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................74,000,000,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers................170,000,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................74,000,000,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...........800,000,000
Bytes for all watchers................408,000,000,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................46
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................46
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers........18,400,000,000
Bytes for all watchers.............11,224,000,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S06) Number of NOTIFY msgs for refreshes
per watcher per day................................70
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day................................70
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.5,600,000,000
Bytes for all watchers per day......2,856,000,000,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers........24,000,000,000
Bytes for all watchers.............14,080,000,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher.................10
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10
(T03) Terminating NOTIFY msgs per watcher....................10
(T04) Terminating 200 OK msgs (NOTIFY) per watcher...........10
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(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................90,000,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................74,000,000,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers................170,000,000,000
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................74,000,000,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...........800,000,000
Bytes for all watchers................408,000,000,000
** Bottom Line
(B01) Total of messages between domains..........25,600,000,000
Total of bytes bet. domains (PD=350)...14,896,000,000,000
Total of bytes bet. domains (PD=3000)..44,046,000,000,000
(B02) Total number of messages / second.................888,889
Total of bytes per second (PD=350)............517,222,222
Total of bytes per second (PD=3000).........1,529,375,000
(B03) Total number of by msgs per user/day................1,280
Total number of bytes per user/day (PD=350).......744,800
Total number of bytes per user/day (PD=3000)....2,202,300
Figure 7: Very large network peering with no optimizations
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................6
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher...............1
(C06) Total number of watchers in domains............20,000,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................1
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(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1
(I03) Initial NOTIFY msgs per watcher.........................1
(I04) Initial 200 OK msgs (NOTIFY) per watcher................1
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers............20,000,000
Bytes for all watchers..................9,000,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers............20,000,000
Bytes for all watchers..................7,400,000,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers............20,000,000
Bytes for all watchers................146,560,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers............20,000,000
Bytes for all watchers..................7,400,000,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers............80,000,000
Bytes for all watchers................170,360,000,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................46
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................46
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers........18,400,000,000
Bytes for all watchers.............15,345,600,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day...280,000,000
Bytes for all watchers per day........114,800,000,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers........18,680,000,000
Bytes for all watchers.............15,460,400,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................1
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1
(T03) Terminating NOTIFY msgs per watcher.....................0
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
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Number of msgs for all watchers............20,000,000
Bytes for all watchers..................9,000,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers............20,000,000
Bytes for all watchers..................7,400,000,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers............40,000,000
Bytes for all watchers.................16,400,000,000
** Bottom Line
(B01) Total of messages between domains..........18,800,000,000
Total of bytes bet. domains (PD=350)...15,647,160,000,000
Total of bytes bet. domains (PD=3000)..40,557,160,000,000
(B02) Total number of messages / second.................652,778
Total of bytes per second (PD=350)............543,304,167
Total of bytes per second (PD=3000).........1,408,234,722
(B03) Total number of by msgs per user/day..................940
Total number of bytes per user/day (PD=350).......782,358
Total number of bytes per user/day (PD=3000)....2,027,858
Figure 8: Very large network peering with optimizations
2.8.4. Intra-domain peering
Within a particular domain, multiple presence infrastructures are
deployed with users split between the two. This scenario is unique
in that federated messages do not pass outside the administrative
domain's network. The two infrastructures peer directly inside the
domain. A common example of this is an enterprise IT system with
multiple independent vendor presence solutions deployed (e.g., a
presence solution for desktop messaging deployed alongside a presence
solution for IP telephony).
Common characteristics of this deployment are
o The difference between subscriptions to presentities in one system
vs. the other are completely arbitrary. Any one presentity is as
likely to be homed on one infrastructure as the other.
o Active users are almost guaranteed of subscribing to many users in
the peer infrastructure.
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o The level of intersection of presentities is extremely high.
The first table below provides the calculations without optimizations
the second table provides the calculations with optimization. Even
though the relatively conservative numbers are used, the amount of
messages is still very high even though optimization may cut the
traffic by more then half
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher..............10
(C06) Total number of watchers in domains...............120,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher.....................10
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10
(I03) Initial NOTIFY msgs per watcher........................10
(I04) Initial 200 OK msgs (NOTIFY) per watcher...............10
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................540,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................444,000,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers..................1,020,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................444,000,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers.............4,800,000
Bytes for all watchers..................2,448,000,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
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Number of msgs for all watchers............52,800,000
Bytes for all watchers.................32,208,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S06) Number of NOTIFY msgs for refreshes
per watcher per day................................70
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day................................70
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day....33,600,000
Bytes for all watchers per day.........17,136,000,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers............86,400,000
Bytes for all watchers.................49,344,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher.................10
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10
(T03) Terminating NOTIFY msgs per watcher....................10
(T04) Terminating 200 OK msgs (NOTIFY) per watcher...........10
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................540,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................444,000,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers..................1,020,000,000
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.............1,200,000
Bytes for all watchers....................444,000,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers.............4,800,000
Bytes for all watchers..................2,448,000,000
** Bottom Line
(B01) Total of messages between domains..............96,000,000
Total of bytes between domains (PD=350)....54,240,000,000
Total of bytes between domains (PD=3000)..152,820,000,000
(B02) Total number of messages / second...................3,333
Total of bytes per second (PD=350)..............1,883,333
Total of bytes per second (PD=3000).............5,306,250
B(03 )Total number of by msgs per user/day..................800
Total number of bytes per user/day (PD=350).......452,000
Total number of bytes per user/day (PD=3000)....1,273,500
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Figure 9: Intra-domain peering with no optimizations
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................3
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher...............1
(C06) Total number of watchers in domains...............120,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher......................1
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1
(I03) Initial NOTIFY msgs per watcher.........................1
(I04) Initial 200 OK msgs (NOTIFY) per watcher................1
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................54,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................44,400,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers....................879,360,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................44,400,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...............480,000
Bytes for all watchers..................1,022,160,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................22
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................22
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers............52,800,000
Bytes for all watchers.................44,035,200,000
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(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................7
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.....1,680,000
Bytes for all watchers per day............688,800,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers............54,480,000
Bytes for all watchers.................44,724,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher..................1
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1
(T03) Terminating NOTIFY msgs per watcher.....................1
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............1
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................54,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................44,400,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers...............120,000
Bytes for all watchers.....................44,400,000
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...............240,000
Bytes for all watchers.....................98.400,000
** Bottom Line
(B01) Total of messages between domains..............55,200,000
Total of bytes between domains (PD=350)....45,844,560,000
Total of bytes between domains (PD=3000)..118,984,560,000
(B02) Total number of messages / second...................1,917
Total of bytes per second (PD=350)..............1,591,825
Total of bytes per second (PD=3000).............4,131,408
(B03) Total number of by msgs per user/day..................460
Total number of bytes per user/day (PD=350).......382,038
Total number of bytes per user/day (PD=3000)......991,538
Figure 10: Intra-domain peering with optimizations
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2.9. Partial Notifications Optimization
Draft [14] define a way for the watcher to request getting only what
was changed in the presence document. The following is a calculation
of the bandwidth that is saved in the very large peering network
case, when we add the partial notification optimization to the dialog
and NOTIFY optimization. It is assumed that except for the initial
NOTIFY all the other NOTIFY messages will be partial. It is also
assumed that only a single attribute in the presence document will be
changed each time, thus the size of the partial presence document is
assumed to be 200 bytes.
** Constants
(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................6
(C03) Subscription refresh interval / hour....................1
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher..............10
(C06) Total number of watchers in domains............20,000,000
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..................350
(C12) Size of an average partial presence document..........200
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher.....................10
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10
(I03) Initial NOTIFY msgs per watcher........................10
(I04) Initial 200 OK msgs (NOTIFY) per watcher...............10
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................90,000,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers..................74,00,000,000
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers................170,000,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers..................74,000,000,000
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...........800,000,000
Bytes for all watchers................408,000,000,000
** Steady State Messages
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(S01) NOTIFY msgs due to state change
per watched presentity per day.....................46
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day.....................46
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers........18,400,000,000
Bytes for all watchers..............9,844,000,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day................................70
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.2,800,000,000
Bytes for all watchers per day......1,148,000,000,000
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers........21,200,000,000
Bytes for all watchers.............10,992,000,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher.................10
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10
(T03) Terminating NOTIFY msgs per watcher.....................0
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................90,000,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................74,000,000,000
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...........400,000,000
Bytes for all watchers................164.000,000,000
** Bottom Line
(B01) Total of messages between domains..........22,400,000,000
Total of bytes bet. domains (PD=350)...11,564,000,000,000
Total of bytes bet. domains (PD=3000)..12,094,000,000,000
(B02) Total number of messages / second.................777,778
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Total of bytes per second (PD=350)............401,527,778
Total of bytes per second (PD=3000)...........419,930,556
(B03) Total number of by msgs per user/day................1,120
Total number of bytes per user/day (PD=350).......578,200
Total number of bytes per user/day (PD=3000)......604,700
Figure 11: Very large networks peering with NOTIFY and partial
optimizations
2.10. Very Optimized SIP
SIP is network agnostic protocol, therefore, the protocol carries
additional messages like 200 OK that would have been redundant in a
protocol that is TCP based only.
The following calculation assumes an imaginary TCP only based version
of SIP that optimizes the following:
o There is no 200 OK for each message. Since only TCP has to be
supported, there is not need to compensate for network issues.
o There is no refresh for subscriptions.
o There is no NOTIFY upon termination of SUBSCRIPTION
o The size of each message is smaller since there is no need for the
various headers that SIP uses for routing etc. So we need to
assume smaller message sizes while we will keep the size of the
presence document the same.
As notes above the calculations in this document do not assume
offline means of getting parts of the presence information.
Therefore, in addition to the above optimizations, the other
optimizations that were assumed in the document will be assumed here
also. These includes partial notifications and the dialog
optimizations. The NOTIFY optimization is not relevant here since
there are no refreshes of subscriptions.
The following is a calculation for the very large networks peering
scenario assuming the imaginary TCP only SIP. It is very interesting
to note that the dialog optimization does not reduce the number of
bytes when partial notification optimization is applied due to the
RLMI overhead.
Figure 12: Very large networks peering, TCP only SIP+Partial+Dialog
optimizations
** Constants
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(C01) Subscription lifetime (hours)...........................8
(C02) Presence state changes / hour...........................6
(C03) Subscription refresh interval / hour....................0
(C04) Total federated presentities per watcher...............10
(C05) Number of dialogs to maintain per watcher..............10
(C06) Total number of watchers in domains............20,000,000
(C07) SUBSCRIBE message size in bytes.......................150
(C08) 200 OK for SUBSCRIBE message size in bytes..............0
(C09) NOTIFY message size not including presence doc........150
(C10) 200 OK for NOTIFY message size in bytes.................0
(C11) Size of an average presence document..................350
(C12) Size of an average partial presence document..........200
** Initial Messages
(I01) Initial SUBSCRIBE msgs per watcher.....................10
(I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............0
(I03) Initial NOTIFY msgs per watcher........................10
(I04) Initial 200 OK msgs (NOTIFY) per watcher................0
(I05) Total number & bytes of initial SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................30,000,000,000
(I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(I07) Total number & bytes of initial NOTIFY msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers................100,000,000,000
(I08) Total number & bytes of initial 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(I09) Total number & bytes of initial messages per day
Number of msgs for all watchers...........400,000,000
Bytes for all watchers................130,000,000,000
** Steady State Messages
(S01) NOTIFY msgs due to state change
per watched presentity per day.....................46
(S02) 200 (for NOTIFY due to state change) msgs
per watched presentity per day......................0
(S03) Total number and size of msgs due to state change per day
Number of msgs for all watchers.........9,200,000,000
Bytes for all watchers..............3,220,000,000,000
(S04) Number of SUBSCRIBE msgs for refreshes
per watcher per day.................................0
(S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes
per watcher per day.................................0
(S06) Number of NOTIFY msgs for refreshes
per watcher per day.................................0
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(S07) Number of 200 OK msgs for NOTIFY msgs for refreshes
per watcher per day.................................0
(S08) Total number and size of msgs due to SUBSCRIBE refreshes
Number of msgs for all watchers per day.............0
Bytes for all watchers per day......................0
(S09) Total number & bytes of steady messages per day
Number of msgs for all watchers.........9,200,000,000
Bytes for all watchers..............3,220,000,000,000
** Termination Messages
(T01) Terminating SUBSCRIBE msgs per watcher.................10
(T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........0
(T03) Terminating NOTIFY msgs per watcher.....................0
(T04) Terminating 200 OK msgs (NOTIFY) per watcher............0
(T05) Total number & bytes of Terminating SUBSCRIBE msgs
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................30,000,000,000
(T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T07) Total number & bytes of terminating NOTIFY msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs
Number of msgs for all watchers.....................0
Bytes for all watchers..............................0
(T09) Total number & bytes of terminating messages per day
Number of msgs for all watchers...........200,000,000
Bytes for all watchers.................30,000,000,000
** Bottom Line
(B01) Total of messages between domains...........9,800,000,000
Total of bytes between domains (PD=350).3,380,000,000,000
Total of bytes bet. domains (PD=3000)...3,910,280,000,000
(B02) Total number of messages / second.................340,278
Total of bytes per second (PD=350)............117,361,111
Total of bytes per second (PD=3000)...........135,763,889
(B03) Total number of by msgs per user/day..................490
Total number of bytes per user/day (PD=350).......169,000
Total number of bytes per user/day (PD=3000)......195,500
Figure 13: Very large networks peering, TCP only SIP+Partial
optimizations
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3. State Management
In previous sections we have discussed the big amount of messages
that need to be sent to/from a presence server In this section the
state that needs to be maintained by a presence server will be
analyzed and shown to be far from trivial.
The presence server has two parallel tasks.
1. Maintain the state of the presentities to which watchers
subscribe.
2. Maintain the state of the subscriptions of watchers and provide
timely updates to the watchers.
For a single subscription from a single watcher on a presentity, the
presence server has to maintain the following state:
o Subscription state including all the parameters that are needed in
order to maintain the subscription as timers.
o Optional filtering information that was requested by the watcher.
This includes enough information that is needed for doing the
filtering. In addition additional information has to be
maintained if partial notification is being supported for the
subscription
o Optional rate management information as throttling
o Watcher information [4], [5] that is the result of the
subscription in order to enable watched presentities to see who is
watching them.
For each presentity that has been subscribed to in the presence
server, the presence server has to maintain the following state:
o A list of the subscriptions for the presentity. Note that this is
already taken care of from the size calculation point of view by
the subscription state above.
o Authorization information for the presentity.
For each presentity for which there was any publication and the
presentity has a state other then a default value, the presence
server has to maintain the current value of the presentity.
3.1. State Size Calculations
Lets assume the following sizes:
o Subscription size - 2K bytes. This includes watcher information
that need to be created by the presence server for each
subscription. This is for each subscription that is done by each
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watcher to each presentity that the watcher is watching. So if we
have 10K watchers we should have 10K of these.
o Subscribed to resource - 1K bytes (for privacy information and
other management info). This is for each presentity that is being
watched. No matter how many watchers are watching it. The
subscriptions themselves are already calculated in the previous
bullet.
o Resource with a state - 6K bytes. This is a moderate assumption
if we take into account the amount of data that is being put in a
presence document as multiple devices, calendar and geographical
information. This is for each presentity that has state other
then the default empty state. It does not matter if it is being
watched or not.
3.1.1. Tiny System
o 10K subscriptions = 19M bytes.
o 5K subscribed to presentities = 5M bytes.
o 10K presentities with state = 58M bytes.
Total is 82M bytes.
3.1.2. Medium System
o 100K subscriptions = 195M bytes.
o 50K subscribed to presentities = 49M bytes.
o 100K presentities with state = 586M bytes.
Total is 830M bytes.
3.1.3. Large System
o 6M subscriptions = 11,718M bytes.
o 3M subscribed to presentities = 2,929M bytes.
o 4M presentities with state = 23437M bytes.
Total is 38G bytes.
3.1.4. Very Large System
o 150M subscriptions = 292,969M bytes.
o 75M subscribed to presentities = 73,242M bytes.
o 100M presentities with state = 585,937M bytes.
Total is 952G bytes which is a very big number for a very dynamic
storage as needed by the presence server.
Although the numbers above may seem moderate enough for the sizes
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that the presence server is handling we should consider the
following:
o Dynamic state - Although the state may seem not so big for
databases even for the very large system, we need to remember that
this state is a very dynamic state. Subscriptions come and go all
the time, the status of presentities is being updated and so
forth. This means that the presence server has to manage its
state in a medium that is very dynamic and for such large sizes
this task is not trivial.
o Interlinked state - The subscriptions and the subscribed to
presentities are dependent on each other. There needs to be a
link from the presentity to the subscriptions and vice versa. See
Section 4.5 about the interlinkage that is created due to resource
lists.
o Moderate assumptions - The size assumptions that were made above
are quite moderate. As presence is becoming more a core
middleware functionality that holds a lot of data on the user. In
real-life the numbers above may be even higher and the presence
server can have additional overhead as managing the SIP sessions,
networking and more.
Although the calculations above do not show that there is a real
issue with state management of presence in medium systems or even in
big systems since it should be possible to divide the state between
different machines, the state size is still very big. A bigger issue
with the state is more when resource lists are involved and create an
interlinked state between many servers. In that case the division of
very big state to multiple servers becomes less trivial...
4. Processing complexities
The basic presence paradigm consists from a watcher and a presentity
to which the watcher watches. It sounds simple enough but there are
many additions and extensions that the presence server has to manage
that make the processing of the presence server very complex.
In this section we show that in addition to the large amount of
messages and the big state that the presence server has to handle, it
has also to handle quite intensive processing for aggregation,
partial notify and publish, filtering and privacy. This adds another
complexity to the presence server in the CPU front in addition to the
network and memory fronts that were described before.
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4.1. Aggregation
A presence document may contain multiple resources. These resources
can be devices of the presentity, information that is received form
external providers of presence information for the presentity as
geographical and calendar information and more.
The presence server needs to be able to get the updates from all the
resources and aggregate them correctly into a single presence
document. Although this is just "XML processing" task, the amount of
updates that the presence server may get, the need to keep the
presence document aligned with its schema and the need to notify the
users as soon as possible create a significant processing burden on
the presence server
4.2. Partial Publish and Notify
Drafts [14], [15] define a way for the watcher to request getting
only what was changed in the presence document and for the publisher
of presence information to publish only what was changed in the
presence document since the last publish. Although these
optimizations help in reducing the amount of the data that is sent
from/to the presence server, these optimizations create additional
processing burden on the presence server.
When a partial publish is arriving to the presence server, the
presence server has to be able to process the partial publish, change
only what is indicated in the partial publish while keeping the
presence document in a well formed shape according to the schema.
In partial notify the processing is even more complex since each
watcher needs to get the partial update based on the last update that
was received by that watcher. Therefore [14] specifies a versioning
mechanism that enables the watcher to get the updates based on the
previous state that it has seen. This versioning mechanism has to be
maintained by the presence server for each watcher that is subscribed
to a presentity and requires partial notify.
4.3. Filtering
Filtering as defined in RFCs [9], [10] enables a watcher to request
to be notified only when the presence document fulfills certain
conditions. Although this is a very convenient feature for watchers,
the burden that is put on the presence server is quite big. For each
change in the presence document, the presence server needs to compute
the filtering expressions which can be very complex, decide whether
and what to send to the watcher that have requested filtering.
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4.4. Authorization
Draft [16] defines presence authorization rules that can be used by
presentities to define who can see what from their presence
documents. The processing that the presence server has to do here is
very similar to filtering. When there is a change to any presence
document that has privacy defined for it, the presence server needs
to create different notification for different watchers according to
what is defined in the authorization rules.
4.5. Resource List Service
RFC [11] defines a way to subscribe on a single URI while that URI is
actually a list of resources that are being subscribed to by a single
subscription. Although this is quite useful mechanism and it
significantly saves on the number of sessions between the watcher and
the presence server (as we show in the calculations of messages),
this feature has the potential to make the scalability issue of
presence systems harder and more complex.
The reasons that resource lists may make the scalability problem of
the presence server even more complex are:
o Subscriptions and state - The resource list may contain reference
to many other presence servers in many other domains. This
requires the RLS to create subscriptions to other presence servers
and buffer the state of all presentities in order to be able to
provide the full state of the presentities in the list when
needed. So in the overall system, the subscriptions that were
saved between the watcher and the presence server are moved to the
backend system while state has been duplicated between the various
presence servers that serve the various presentities and the RLSs.
This issue could have been mitigated if there was a way for the
RLS to retrieve the presence information for many watchers while
adhering to privacy when sending the actual notifications to the
watchers.
o Interlinkage - The resource list subscription will reach one RLS
that will open it and send it to many presence servers and to
other RLSs (if there is a subgroup inside the list). This way a
complex linkage between the state of many components is created.
This linkage makes state management and other maintenance of a
presence systems quite complex.
o Big lists are easy - There are two types of groups that may be
used with this feature, private groups that are defined by/for
each watcher and public groups that are defined in the system and
can be used by any watcher. Although we should expect IT
administrators to take caution when creating public groups, this
may be not the case in real life. The connection between the size
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of the public group and the load on the presence server system may
not apparent to everyone. Furthermore many public groups that are
used in presence systems may have been created for other purposes
as email systems (where the size of the lists was not so
important) and are taken as they are to presence systems. So for
example we may very easily find that a public group that actually
covers all the users in the enterprise are used by many users in
the enterprise thus creating unbearable load on the presence
server. Note that this issue is not a protocol or design issue
but more a usage issue that may have a real impact on the presence
system.
o Stopping notifications - A watcher may accidentally subscribe to a
very big list and be overwhelmed by the amount of notifies that it
receives from the presence server. There is no current way to
stop this stream of notifies and even canceling the subscription
may take time until being affective.
The issues mentioned above are one example of an optimization that
helps in one part of the system but creates even bigger problems in
the overall system. There is a need to think about the problems
listed above but more then that there is a need to make sure that
when an optimization is introduced it does not create issues in other
places.
5. Current Optimizations
This section lists and discusses several optimizations that are
either already part of the SIP protocol or they have been suggested
in various drafts. Several other optimizations that have been
suggested but have not been discussed in any working group yet are
summarized in [21] and in [23]. Note that trials with batched
notifies optimization that is describes in [21], showed an
improvement of 117% in the whole throughput of presence traffic.
o Subnot-etags - Draft [19]. This draft suggests ways to suppress
the sending of unnecessary notifies when for example a
subscription is refreshed. This suggestion seems to be an
efficient optimization since it saves both the number of messages
sent and on the processing time of the presence server.
o Resource List Service - [11] enable creating a single subscription
session between the watcher and the presence server for
subscribing on a list of users. This saves the amount of sessions
that are created between watchers and presence servers. On the
other hand, this mechanism enables creating very large amount of
subscriptions in the presence server/RLS system thus enabling the
creation of a very large number of subscriptions between presence
servers and RLSs with relatively few clients especially if large
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public groups are used. It seems that in order to really optimize
in this area, the usage of large public groups should not be
considered as BCP and there should be a way for an RLS to create a
single subscription for multiple occurrences of the same resource
in resource lists. See consolidates subscriptions below.
o Partial notify/publish - Drafts [14], [15] define a way for the
subscriber to request getting only what was changed in the
presence document and for the publisher of presence information to
publish only what was changed in the presence document since the
last publish. Although these optimizations help in reducing the
amount of actual data that is sent from/to the presence server,
these optimizations create additional processing burden on the
presence server as was discussed above.
o Filtering as defined in RFCs [9], [10] enables a watcher to
request to be notified only when the presence document fulfills
certain conditions. Although this optimization enables saving on
the amount of messages that are sent from the presence server to
the watcher, this optimization puts more burden on the processing
time of the presence server as was discussed above.
o Throttling [22] defines a mechanism in which a watcher requires to
be updated only in certain intervals. Although this mechanism may
give some extra load on the processing time of the presence
server, that load is negligible and the reduction on the amount of
messages sent from the presence server to the watchers is
significant. This optimization is even more important with
resource lists where there can be many resources in the resource
lists and if the traffic of updates on resource list is not
regulated, the watcher may get very large amount of notifications.
o Presence specific sigcomp dictionary [17] defines a SIGCOMP [3]
dictionary for presence. This optimization will enable to reduce
the number of bytes that are transferred in presence systems by
compressing the textual SIP messages and using the specialized
presence dictionary the compression may be more significant then
just using SIGCOMP as is. Note that number of actual messages
will remain the same and a calculation of the amount of bytes that
will be saved may be useful here.
o Content Indirection [8] enables sending only the URI of the
presence document to the watcher thus offloading the presence
server from sending the presence document to the watcher. This
optimization may be useful in some cases especially where there is
a big number of users that get the same presence document.
6. Summary
Following is a summary of the various calculations. This is repeated
here in order to ease the understanding of the conclusions that are
listed below.
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The following table summarizes the various constants that are used in
ALL calculations.
(C01) Subscription lifetime (hours)...........................8
(C03) Subscription refresh interval / hour....................1
(C05) Number of dialogs to maintain per watcher = Number of
federated presentities when dialog optimization is
not used and to 1 when dialog optimization is used.
(C07) SUBSCRIBE message size in bytes.......................450
(C08) 200 OK for SUBSCRIBE message size in bytes............370
(C09) NOTIFY message size not including presence doc........500
(C10) 200 OK for NOTIFY message size in bytes...............370
(C11) Size of an average presence document..........350 or 3000
Calculations are done for both sizes
(C12) Size of an average partial presence document..........200
(C13) Additional data per document in RLMI..................160
(C14) Multiparty boundary in RLMI document..................144
(C15) XML root node in RLMI document........................144
Figure 14: Constants in ALL calculations
The following table summarizes the results of various optimization
factors for the basic use case.
C02 Presence state changes / hour.............................3
C04 Total federated presentities per watcher..................4
C06 Total # of watchers in the federated domains.........40,000
No optimizations are applied
(B01) Total of messages between domains..............12,800,000
Total of bytes between domains (PD=350).....7,232,000,000
Total of bytes between domains (PD=3000)...20,376,000,000
(B02) Total number of messages / second.. ..................444
Total of bytes per second (PD=350)................251,111
Total of bytes per second (PD=3000)...............707,500
(B03) Total number of by msgs per user/day......... ........320
Total number of bytes per user/day (PD=350).......180,800
Total number of bytes per user/day (PD=3000)......509,400
Dialog optimization is applied
(B01) Total of messages between domains...............8,480,000
Total of bytes between domains (PD=350).....7,440,960,000
Total of bytes between domains (PD=3000)...20,266,960,000
(B02) Total number of messages / second.....................294
Total of bytes per second (PD=350)................256,767
Total of bytes per second (PD=3000)...............702,114
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(B03) Total number of by msgs per user/day..................212
Total number of bytes per user/day (PD=350).......186,024
Total number of bytes per user/day (PD=3000)......506,674
Notify optimization is applied
(B01) Total of messages between domains..............10,240,000
Total of bytes between domains (PD=350).....5,670,400,000
Total of bytes between domains (PD=3000)...15,422,400,000
(B02) Total number of messages / second.....................356
Total of bytes per second (PD=350)................196,889
Total of bytes per second (PD=3000)...............535,500
(B03) Total number of by msgs per user/day..................256
Total number of bytes per user/day (PD=350).......141,760
Total number of bytes per user/day (PD=3000)......385,560
Dialog and notify optimizations are applied
(B01) Total of messages between domains...............7,840,000
Total of bytes between domains (PD=350).....6,317,520,000
Total of bytes between domains (PD=3000)...16,069,520,000
(B02) Total number of messages / second.....................272
Total of bytes per second (PD=350)................219,358
Total of bytes per second (PD=3000)...............557,769
(B03) Total number of by msgs per user/day..................196
Total number of bytes per user/day (PD=350).......157,938
Total number of bytes per user/day (PD=3000)......401,738
Figure 15: Basic use case
The following table summarizes the results of various optimization
factors for the widely distributed inter domain use case.
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C02 Presence state changes / hour.............................3
C04 Total federated presentities per watcher.................20
C06 Total # of watchers in the federated domains.........40,000
No optimizations are applied
(B01) Total of messages between domains..............64,000,000
Total of bytes between domains (PD=350)....36,160,000,000
Total of bytes between domains (PD=3000)..101,880,000,000
(B02) Total number of messages / second...................2,222
Total of bytes per second (PD=350)..............1,255,556
Total of bytes per second (PD=3000).............3,537,500
(B03) Total number of by msgs per user/day................1,600
Total number of bytes per user/day (PD=350).......904,000
Total number of bytes per user/day (PD=3000).....,547,000
Dialog and notify optimizations are applied
(B01) Total of messages between domains..............36,000,000
Total of bytes between domains (PD=350)....30,221,520,000
Total of bytes between domains (PD=3000)...78,981,520,000
(B02) Total number of messages / second...................1,250
Total of bytes per second (PD=350)..............1,049,358
Total of bytes per second (PD=3000).............2,742,414
(B03) Total number of by msgs per user/day..................900
Total number of bytes per user/day (PD=350).......755,538
Total number of bytes per user/day (PD=3000)....1,974,538
Figure 16: Widely distributed inter-domain
The following table summarizes the results of various optimization
factors for the intra-domain peering use case.
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C02 Presence state changes / hour.............................3
C04 Total federated presentities per watcher.................10
C06 Total # of watchers in the federated domains........120,000
No optimizations are applied
B01 Total of messages between domains................96,000,000
Total of bytes between domains (PD=350)........54,240,000,000
Total of bytes between domains (PD=3000)......152,820,000,000
B02 Total number of messages / second.....................3,333
Total of bytes per second (PD=350)..................1,883,333
Total of bytes per second (PD=3000).................5,306,250
B03 Total number of by msgs per user/day....................800
Total number of bytes per user/day (PD=350)...........452,000
Total number of bytes per user/day (PD=3000)........1,273,500
Dialog and notify optimizations are applied
B01 Total of messages between domains................55,200,000
Total of bytes between domains (PD=350)........45,827,280,000
Total of bytes between domains (PD=3000)......118,967,280,000
B02 Total number of messages / second.....................1,917
Total of bytes per second (PD=350)..................1,591,225
Total of bytes per second (PD=3000).................4,130,808
B03 Total number of by msgs per user/day....................460
Total number of bytes per user/day (PD=350)...........381,894
Total number of bytes per user/day (PD=3000)..........991,394
Figure 17: Inter-domain peering
The following table summarizes the results of various optimization
factors for the very large scale peering networks use case.
C02 Presence state changes / hour.............................6
C04 Total federated presentities per watcher.................10
C06 Total # of watchers in the federated domains.....20,000,000
No optimizations are applied
(B01) Total of messages between domains..........25,600,000,000
Total of bytes bet. domains (PD=350)...14,896,000,000,000
Total of bytes bet. domains (PD=3000)..44,046,000,000,000
(B02) Total number of messages / second.................888,889
Total of bytes per second (PD=350)............517,222,222
Total of bytes per second (PD=3000).........1,529,375,000
(B03) Total number of by msgs per user/day................1,280
Total number of bytes per user/day (PD=350).......744,800
Total number of bytes per user/day (PD=3000)....2,202,300
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Dialog and notify optimizations are applied
(B01) Total of messages between domains..........18,800,000,000
Total of bytes bet. domains (PD=350)...15,647,160,000,000
Total of bytes bet. domains (PD=3000)..40,557,160,000,000
(B02) Total number of messages / second.................652,778
Total of bytes per second (PD=350)............543,304,167
Total of bytes per second (PD=3000).........1,408,234,722
(B03) Total number of by msgs per user/day..................940
Total number of bytes per user/day (PD=350).......782,358
Total number of bytes per user/day (PD=3000)....2,027,858
Partial and notify optimizations are applied
(B01) Total of messages between domains..........22,400,000,000
Total of bytes bet. domains (PD=350)...11,564,000,000,000
Total of bytes bet. domains (PD=3000)..12,094,000,000,000
(B02) Total number of messages / second.................777,778
Total of bytes per second (PD=350)............401,527,778
Total of bytes per second (PD=3000)...........419,930,556
(B03) Total number of by msgs per user/day................1,120
Total number of bytes per user/day (PD=350).......578,200
Total number of bytes per user/day (PD=3000)......604,700
TCP only SIP+Partial+Dialog optimizations
(B01) Total of messages between domains...........9,269,000,000
Total of bytes between domains (PD=350).7,484,280,000,000
Total of bytes bet. domains (PD=3000)...8,014,280,000,000
(B02) Total number of messages / second.................321,528
Total of bytes per second (PD=350)............259,870,833
Total of bytes per second (PD=3000)...........278,273,611
(B03) Total number of by msgs per user/day..................463
Total number of bytes per user/day (PD=350).......374,214
Total number of bytes per user/day (PD=3000)......400,714
TCP only SIP+Partial optimizations
(B01) Total of messages between domains...........9,800,000,000
Total of bytes between domains (PD=350).3,380,000,000,000
Total of bytes bet. domains (PD=3000)...3,910,280,000,000
(B02) Total number of messages / second.................340,278
Total of bytes per second (PD=350)............117,361,111
Total of bytes per second (PD=3000)...........135,763,889
(B03) Total number of by msgs per user/day..................490
Total number of bytes per user/day (PD=350).......169,000
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Total number of bytes per user/day (PD=3000)......195,500
Figure 18: Very large scale peering networks
7. Conclusions
The following conclusions can be drawn from the above numbers:
o Due to the overhead of RLMI, the dialog optimization does not help
in reducing the number of bytes nor in the number of the messages.
It seems to be more important from the point of view of the
convenience of the user since it enables the user to manage his/
hers watch list on e.g. a web page.
o The notify optimization optimizes both the number of messages and
the number of bytes.
o Partial notification saves a lot in the number of bytes especially
when the presence document is a rich presence document which is
relatively big.
o Comparing to very optimized SIP protocol (imaginary TCP only SIP)
shows that the number of messages is less by about a half. The
number of bytes is also reduced by about a half.
o When looking at the numbers from the perspective of the number of
bytes that a user "consumes" per day the numbers may not look so
big. Nevertheless, we should remember that the overall affect on
the network may be quite big since the network will have to convey
dozens of Giga bytes per day for the modest use cases that are
described in this document for presence traffic only. Recalling
that presence is only an enabler for other media these numbers are
not so easy to handle.
The document analyzes the scalability of presence systems and of the
SIP based in particular. It is apparent that the scalability of
these systems is far from being trivial from several perspectives:
number of messages, network bandwidth, state management and CPU load.
As part of the analysis we have analyzed several optimizations and
showed the effect of these optimizations on the number of messages
and the number of bytes that are sent between the federating domains.
We have also computed the number of messages and bytes for a very
large scale peering network while assuming a protocol that has much
less overhead then SIP. Even in that protocol we got relatively high
numbers.
It is very possible that the issues that are described in this
document are inherent to presence systems in general and not specific
to the SIMPLE protocol. Organizations need to be prepared to invest
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a lot in network and hardware in order to create real big systems.
However, it is apparent that not all the possible optimizations were
done yet and further work is needed in the IETF in order to provide
better scalability
Nevertheless, we should remember that SIP was originally designed for
end to end session creation and number and size of messages are of
secondary importance for end to end session negotiation. For large
scale and especially for very large scale presence the number of
messages that are needed and the size of each message are of extreme
importance. It seems that we need to think about the problem in a
different way. We need to think about scalability as part of the
protocol design. The IETF tends not to think about actual
deployments when designing a protocol but in this case it seems that
if we do not think about scalability with the protocol design it will
be very hard to scale.
We should also consider whether using the same protocol between
clients and servers and between servers is a good choice with this
problem? It may be that in interdomain or even between servers in
the same domain (as between RLSs and presence servers) there is a
need to have a different protocol that will be very optimized for the
load and can assume some assumptions about the network (e.g. do not
use unreliable protocol as UDP but only TCP).
When servers is connecting to another server using current protocol,
there will be an extreme number of redundant messages due to the
overhead of supporting UDP and to the need to send multiple presence
documents for the same watched user due to privacy issue. A server
to server protocol will have to address these issues. Some initial
work to address these issues can be found in: [21], [23] and [24]
Another issue that is more concerning protocol design is whether
NOTIFY messages should not be considered as media as audio, video and
even text messaging are considered? The SUBSCRIBE can be extended to
do similar three way handshake as INVITE and negotiate where the
notify messages should go, rate and other parameters. This way the
load can be offloaded to a specialized NOTIFY "relays" thus not
loading the control path of SIP. One of the possible ideas (Marc
Willekens) is to use the SIP stack for the client/server NOTIFY but
make use of a more optimized and controllable protocol for the
server-to-server interface. Another possibility is to use the MSRP
[12], [13]protocol for the notifies.
8. Security Considerations
This document discusses scalability issues with the existing SIP/
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SIMPLE presence protocol and model. Therefore, there are no security
considerations to be considered for this document. However, a lot of
the possible optimizations that should emerge as a result of this
document will have security implications that will need to be solved.
9. Changes from Previous Versions
9.1. Changes in version 04
o Fixed mistake in the formula of I07 and S08 (RLMI was not
included). Affect on total number of bytes was very small.
o Fixed mistake in the text of the calculation of number of bytes
for S08 for non dialog optimization. No actual change in number
of bytes since the excel file calculations were done correctly.
o Removed general references throughout the text to "other
protocols". This was done in order to avoid the impression that
the document tries to compare SIP protocol with any other presence
base protocol.
o Several other editorial and clarification changes
9.2. Changes in version 03
o Added some input from real life deployments and input on a test
with batched notifies.
o Added Calculations of messages and bytes per user.
o Calculations are now done both for minimal size of presence
document and for an average size of rich presence document.
o Comparison with other protocol is now done using small, tiny and
rich presence document sizes.
o Removed dialog optimization with partial notification since it is
not relevant
o Fixed a few issues in calculations that were found by Victoria
Beltran-Martinez.
* Added overhead for RLMI for dialog optimizations (list
subscription). This calculation fix actually shows that dialog
optimization is not a real optimization from the point of view
of bytes and number of messages.
* When NOTIFY optimizations are applied no need for final NOTIFY
* The usage of RLS between domains was clarified.
o Significantly enhanced the conclusions section
o Several typo fixes
9.3. Changes in version 02
o Fixed a bug in the calculations. Thanks to Marc Willekens for
finding the bug.
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9.4. Changes in version 01
o Clarifications and corrections of the computation model and the
computations.
o Added several more computations to show the influence of different
optimizations.
o The requirements were moved to [20]
o The new suggestions for optimizations were moved to [21]
10. Acknowledgments
We would like to thank Jonathan Rosenberg, Ben Campbell, Markus
Isomaki Piotr Boni, David Viamonte, Aki Niemi and Peter-Saint Andre
for ideas and input. Special thanks to Marc Willekens and Victoria
Beltran-Martinez for finding issues in the calculations.
11. References
11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
11.2. Informational References
[2] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[3] Price, R., Bormann, C., Christoffersson, J., Hannu, H., Liu,
Z., and J. Rosenberg, "Signaling Compression (SigComp)",
RFC 3320, January 2003.
[4] Rosenberg, J., "A Watcher Information Event Template-Package
for the Session Initiation Protocol (SIP)", RFC 3857,
August 2004.
[5] Rosenberg, J., "An Extensible Markup Language (XML) Based
Format for Watcher Information", RFC 3858, August 2004.
[6] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and
J. Peterson, "Presence Information Data Format (PIDF)",
RFC 3863, August 2004.
[7] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
"RPID: Rich Presence Extensions to the Presence Information
Data Format (PIDF)", RFC 4480, July 2006.
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[8] Burger, E., "A Mechanism for Content Indirection in Session
Initiation Protocol (SIP) Messages", RFC 4483, May 2006.
[9] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
Requena, "Functional Description of Event Notification
Filtering", RFC 4660, September 2006.
[10] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
Requena, "An Extensible Markup Language (XML)-Based Format for
Event Notification Filtering", RFC 4661, September 2006.
[11] Roach, A., Campbell, B., and J. Rosenberg, "A Session
Initiation Protocol (SIP) Event Notification Extension for
Resource Lists", RFC 4662, August 2006.
[12] Campbell, B., Mahy, R., and C. Jennings, "The Message Session
Relay Protocol (MSRP)", RFC 4975, September 2007.
[13] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions for the
Message Sessions Relay Protocol (MSRP)", RFC 4976,
September 2007.
[14] Lonnfors, M., Costa-Requena, J., Leppanen, E., and H.
Khartabil, "Session Initiation Protocol (SIP) extension for
Partial Notification of Presence Information",
draft-ietf-simple-partial-notify-10 (work in progress),
January 2008.
[15] Niemi, A., Lonnfors, M., and E. Leppanen, "Publication of
Partial Presence Information",
draft-ietf-simple-partial-publish-07 (work in progress),
February 2008.
[16] Rosenberg, J., "Presence Authorization Rules",
draft-ietf-simple-presence-rules-10 (work in progress),
July 2007.
[17] Garcia-Martin, M., "The Presence-Specific Static Dictionary for
Signaling Compression (Sigcomp)",
draft-garcia-simple-presence-dictionary-06 (work in progress),
August 2007.
[18] Camarillo, G., "Subscriptions to Request-Contained Resource
Lists in the Session Initiation Protocol (SIP)",
draft-ietf-sipping-uri-list-subscribe-05 (work in progress),
May 2006.
[19] Niemi, A., "An Extension to Session Initiation Protocol (SIP)
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Events for Conditional Event Notification",
draft-ietf-sip-subnot-etags-01 (work in progress), August 2007.
[20] Houri, A., Parameswar, S., Aoki, E., Singh, V., and H.
Schulzrinne, "Scaling Requirements for Presence in SIP/SIMPLE",
draft-ietf-sipping-presence-scaling-requirements-00 (work in
progress), February 2008.
[21] Houri, A., "Scaling Optimizations for Presence in SIP/SIMPLE",
draft-houri-simple-interdomain-scaling-optimizations-00 (work
in progress), July 2007.
[22] Niemi, A., "Session Initiation Protocol (SIP) Event
Notification Extension for Notification Throttling",
draft-niemi-sipping-event-throttle-05 (work in progress),
March 2007.
[23] Rosenberg, J., Donovan, S., and K. McMurry, "Optimizing
Federated Presence with View Sharing",
draft-ietf-simple-view-sharing-00 (work in progress),
February 2008.
[24] Rosenberg, J., Houri, A., "Models for Intra-Domain Presence Federation",
draft-ietf-simple-intradomain-federation-00 (work in
progress), February 2008.
Authors' Addresses
Avshalom Houri
IBM
Science Park
Rehovot,
Israel
Email: avshalom@il.ibm.com
Edwin Aoki
AOL LLC
360 W. Caribbean Drive
Sunnyvale, CA 94089
USA
Email: aoki@aol.net
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Sriram Parameswar
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: Sriram.Parameswar@microsoft.com
Tim Rang
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
Email: timrang@microsoft.com
Vishal Singh
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Email: vs2140@cs.columbia.edu
URI: http://www.cs.columbia.edu/~vs2140
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu/~hgs
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