One document matched: draft-ietf-tsvwg-admitted-realtime-dscp-04.txt
Differences from draft-ietf-tsvwg-admitted-realtime-dscp-03.txt
Transport Working Group F. Baker
Internet-Draft J. Polk
Updates: 4542,4594 Cisco Systems
(if approved) M. Dolly
Intended status: Standards Track AT&T Labs
Expires: August 28, 2008 February 25, 2008
DSCPs for Capacity-Admitted Traffic
draft-ietf-tsvwg-admitted-realtime-dscp-04
Status of this Memo
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This Internet-Draft will expire on August 28, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document requests one Differentiated Services Code Point (DSCP)
from the Internet Assigned Numbers Authority (IANA) for real-time
traffic classes similar to voice conforming to the Expedited
Forwarding Per Hop Behavior, and admitted using a call admission
procedure involving authentication, authorization, and capacity
admission.
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It also recommends that certain classes of video traffic described in
RFC 4594 and which have similar requirements be changed to require
admission using a Call Admission Control (CAC) procedure involving
authentication, authorization, and capacity admission.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Problem . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Proposed Solution . . . . . . . . . . . . . . . . . . . . 7
2. Implementation of the Admitted Service Classes . . . . . . . . 7
2.1. Potential implementations of EF in this model . . . . . . 7
2.2. Capacity admission control . . . . . . . . . . . . . . . . 9
2.2.1. Capacity admission control by assumption . . . . . . . 10
2.2.2. Capacity admission control by call counting . . . . . 10
2.2.3. End-point capacity admission performed by probing
the network . . . . . . . . . . . . . . . . . . . . . 11
2.2.4. Centralized capacity admission control . . . . . . . . 11
2.2.5. Distributed capacity admission control . . . . . . . . 12
2.3. Prioritized capacity admission control . . . . . . . . . . 12
3. Recommendations on implementation of an Admitted Telephony
Service Class . . . . . . . . . . . . . . . . . . . . . . . . 13
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Normative References . . . . . . . . . . . . . . . . . . . 15
7.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 19
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1. Introduction
This document requests one Differentiated Services Code Point (DSCP)
from the Internet Assigned Numbers Authority (IANA) for a class of
real-time traffic. This class conforms to the Expedited Forwarding
[RFC3246] [RFC3247] Per Hop Behavior. It is also admitted using a
CAC procedure involving authentication, authorization, and capacity
admission. This differs from a real-time traffic class conforming to
the Expedited Forwarding Per Hop Behavior but not subject to capacity
admission or subject to very coarse capacity admission.
It also recommends that certain classes of video described in
[RFC4594] be treated as requiring capacity admission as well.
These applications have one or more potential congestion points
between the video distribution/conferencing bridge or gaming server
and the user(s), and reserving capacity for them is important to
application performance. All of these applications have low
tolerance to jitter (aka delay variation) and loss, as summarized in
Section 2, and most (except for multimedia conferencing) have
inelastic flow behavior from Figure 1 of [RFC4594]. Inelastic flow
behavior and low jitter/loss tolerance are the service
characteristics that define the need for admission control behavior.
One of the reasons behind this is the need for classes of traffic
that are handled under special policies, such as the non-preemptive
Emergency Telecommunication Service, the US Department of Defense's
Assured Service (which is similar to Multi-Level Precedence and
Preemption [ITU.MLPP.1990] procedure), or e-911, in addition to
normal routine calls that use call admission. It is possible to use
control plane protocols to generally restrict session admission such
that admitted traffic should receive the desired service, and the
policy (e.g. Routine, National Security or Emergency Preparedness
[NS/EP] communications, e-911, etc) need not be signaled in a DSCP.
However, service providers need to distinguish between special-policy
traffic and other classes, particularly the existing VoIP services
that perform no capacity admission or only very coarse capacity
admission and can exceed their allocated resources.
The requested DSCP applies to the Telephony Service Class described
in [RFC4594]. The video classes addressed include the
o interactive real-time traffic (CS4, used for Video conferencing
and Interactive gaming),
o broadcast TV (CS3) for use in a video on demand context, and
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o AF4 Multimedia conferencing (video conferencing).
Since the admitted video classes have not had the history of mixing
admitted and non-admitted traffic in the same Per-Hop Behavior (PHB)
as has occurred for EF, an additional DSCP code point is not
recommended. Instead, the recommended "best practice" is to perform
admission control for the above video classes.
Other video classes are not believed to be required by the targeted
services and to not have the current problem of confusion with
unadmitted traffic. Within an ISP and on inter-ISP links (i.e.
within networks whose internal paths are uniform at hundreds of
megabits or faster), one would expect all of this traffic to be
carried in the Real Time Traffic Class described in [RFC5127].
1.1. Definitions
The following terms and acronyms are used in this document.
PHB: A Per-Hop-Behavior (PHB) is the externally observable
forwarding behavior applied at a Differentiated Services compliant
node to a DS behavior aggregate [RFC2475]. It may be thought of
as a program configured on the interface of an Internet host or
router, specified drop probabilities, queuing priorities or rates,
and other handling characteristics for the traffic class.
DSCP: The Differentiated Services Code Point (DSCP), as defined in
[RFC2474], is a value which is encoded in the DS field, and which
each DS Node MUST use to select the PHB which is to be experienced
by each packet it forwards [RFC3260]. It is a 6-bit number
embedded into the 8-bit TOS field of an IPv4 datagram or the
Traffic Class field of an IPv6 datagram.
CAC: Call Admission Control includes concepts of authorization and
capacity admission. "Authorization" includes and procedure
identifies a user, verifies the authenticity of the
identification, and determines whether the user is authorized to
use the service. "Capacity Admission" refers to any procedure
that determines whether capacity exists supporting a session's
requirements under some policy.
In the Internet, these are separate functions, while in the PSTN
they and call routing are carried out together.
UNI: A User/Network Interface (UNI) is the interface (often a
physical link or its virtual equivalent) that connects two
entities that do not trust each other, and in which one (the user)
purchases connectivity services from the other (the network).
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Figure 1 shows two user networks connected by what appears to each
of them to be a single network ("The Internet", access to which is
provided by their service provider) that provides connectivity
services to other users.
UNIs tend to be the bottlenecks in the Internet, where users
purchase relatively low amounts of bandwidth for cost or service
reasons, and as a result are most subject to congestion issues and
therefore issues requiring traffic conditioning and service
prioritization.
NNI: A Network/Network Interface (NNI) is the interface (often a
physical link or its virtual equivalent) that connects two
entities that trust each other within limits, and in which the two
are seen as trading services for value. Figure 1 shows three
service networks that together provide the connectivity services
that we call "the Internet". They are different administrations
and are very probably in competition, but exchange contracts for
connectivity and capacity that enable them to offer specific
services to their customers.
NNIs may not be bottlenecks in the Internet if service providers
contractually agree to provision excess capacity at them, as they
commonly do. However, NNI performance may differ by ISP, and the
performance guarantee interval may range from a month to a much
shorter period. Furthermore, a peering point NNI may not have
contractual performance guarantees or may become overloaded under
certain conditions. They are also policy-controlled interfaces,
especially in BGP. As a result, they may require traffic
prioritization policy.
Queue: There are multiple ways to build a multi-queue scheduler.
Weighted Round Robin (WRR) literally builds multiple lists and
visits them in a specified order, while a calendar queue (often
used to implement Weighted Fair Queuing, or WFQ) builds a list for
each time interval and enqueues at most a stated amount of data in
each such list for transmission during that time interval. While
these differ dramatically in implementation, the external
difference in behavior is generally negligible when they are
properly configured. Consistent with the definitions used in the
Differentiated Services Architecture [RFC2475], these are treated
as equivalent in this document, and the lists of WRR and the
classes of a calendar queue will be referred to uniformly as
"queues".
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_.--------.
,-'' `--.
,-' `-.
,-------. ,',-------. `.
,' `. ,',' `. `.
/ User \ UNI / / Service \ \
( Network +-----+ Network ) `.
\ / ; \ / :
`. ,' ; `. .+ :
'-------' / '-------' \ NNI \
; \ :
; "The Internet" \ ,-------. :
; +' `. :
UNI: User/Network Interface / Service \ |
| ( Network ) |
NNI: Network/Network Interface \ / |
: +. ,' ;
: / '-------' ;
: / ;
,-------. \ ,-------. / NNI /
,' `. : ,' `+ ;
/ User \ UNI / Service \ ;
( Network +-----+ Network ) ,'
\ / \ \ / /
`. ,' `.`. ,' ,'
'-------' `.'-------' ,'
`-. ,-'
`--. _.-'
`--------''
Figure 1: UNI and NNI interfaces
1.2. Problem
In short, the Telephony Service Class described in [RFC4594] permits
the use of capacity admission in implementing the service, but
present implementations either provide no capacity admission services
or do so in a manner that depends on specific traffic engineering.
In the context of the Internet backbone, the two are essentially
equivalent; the edge network is depending on specific engineering by
the service provider that may not be present.
However, services are being requested of the network that would
specifically make use of capacity admission, and would distinguish
among users or the uses of available Voice-on-IP or Video-on-IP
capacity in various ways. Various agencies would like to provide
services as described in section 2.6 of [RFC4504] or in [RFC4190].
This requires the use of capacity admission to differentiate among
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users (which might be 911 call centers, other offices with
preferential service contracts, or individual users gaining access
with special credentials) to provide services to them that are not
afforded to non-capacity admitted customer-to-customer IP telephony
sessions.
1.3. Proposed Solution
The IETF is asked to differentiate, in the Telephony Service, between
sessions that are originated without capacity admission or using
traffic engineering and sessions that are originated using more
robust capacity admission procedures. Sessions of the first type use
a traffic class in which they compete without network-originated
control as described in Section 2.2.1 or Section 2.2.2, and in the
worst case lose traffic due to policing. Sessions of the second type
cooperate with network control, and may be given different levels of
preference depending on the policies that the network applies. In
order to provide this differentiation, the IETF requests that the
IANA assign a separate DSCP value to admitted sessions using the
Telephony service (see Section 4 ).
2. Implementation of the Admitted Service Classes
2.1. Potential implementations of EF in this model
There are at least two possible ways to implement the Expedited
Forwarding PHB in this model. They are to implement separate classes
as a set of
o Multiple data plane traffic classes, each consisting of a policer
and a queue, and the queues enjoying different priorities, or
o Multiple data plane traffic classes, each consisting of a policer
but feeding into a common queue or multiple queues at the same
priority.
We will explain the difference, and describe in what way they differ
in operation. The reason this is necessary is that there is current
confusion in the industry, including a widely reported test for NS/EP
services that implemented the policing model and described it as an
implementation of the multi-priority model, and discussion in other
environments of the intermixing of voice and video traffic at
relatively low bandwidths in the policing model.
The multi-priority model is shown in Figure 2. In this model,
traffic from each service class is placed into a separate priority
queue. If data is present in both queues, traffic from one of them
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will always be selected for transmission. This has the effect of
transferring jitter from the higher priority queue to the lower
priority queue, and reordering traffic in a way that gives the higher
priority traffic a smaller average queuing delay. Each queue must
have its own policer, however, to protect the network from errors and
attacks; if a traffic class thinks it is carrying a certain data rate
but an abuse sends significantly more, the effect of simple
prioritization would not preserve the lower priorities of traffic,
which could cause routing to fail or otherwise impact an SLA.
.
policers priorities |`.
EF ---------> <=> ----------||----+ `.
high| `.
EF2---------> <=> ----------||----+ .'-----------
. medium .'
rate queues |`. +-----+ .' Priority
AF1------>||----+ `. / low |' Scheduler
| `. /
AF2------>||----+ .'-+
| .'
CS0------>||----+ .' Rate Scheduler
|' (WFQ, WRR, etc)
Figure 2: Implementation as a data plane priority
The multi-policer model is shown in Figure 3. In this model, traffic
from each service class is policed according to its SLA requirements,
and then placed into a common priority queue. Unlike the multi-
priority model, the jitter experienced by the traffic classes in this
case is the same, as there is only one queue, but the sum of the
traffic in this higher priority queue experiences less average jitter
than the elastic traffic in the lower priority.
policers priorities .
EF ---------> <=> -------\ |`.
--||----+ `.
EF2---------> <=> -------/ high| `.
. | .'--------
rate queues |`. +-----+ .'
AF1------>||----+ `. / low | .' Priority
| `. / |' Scheduler
AF2------>||----+ .'-+
| .'
CS0------>||----+ .' Rate Scheduler
|' (WFQ, WRR, etc)
Figure 3: Implementation as a data plane policer
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The difference between the two operationally is, as stated, the
issues of loss due to policing and distribution of jitter.
If the two traffic classes are, for example, voice and video,
datagrams containing video data are relatively large (generally the
size of the path MTU) while datagrams containing voice are relatively
small, on the order of only 40 to 200 bytes, depending on the codec.
On lower speed links (less than 10 MBPS), the jitter introduced by
video to voice can be disruptive, while at higher speeds the jitter
is nominal compared to the jitter requirements of voice. At access
network speeds, therefore, [RFC4594] recommends separation of video
and voice into separate queues, while at optical speeds [RFC5127]
recommends that they use a common queue.
If, on the other hand, the two traffic classes are carrying the same
type of application with the same jitter requirements, then giving
one preference in this sense does not benefit the higher priority
traffic and may harm the lower priority traffic. In such a case,
using separate policers and a common queue is a superior approach.
2.2. Capacity admission control
There are five major ways that capacity admission is done or has been
proposed to be done in real-time applications:
o Capacity admission control by assumption,
o Capacity admission control by call counting,
o End-point capacity admission performed by probing the network,
o Centralized capacity admission control, and
o Distributed capacity admission control.
There is also a mechanism that has been proposed for enhancing the
probability of call completion in a preferential manner. This is not
capacity admission per se, since it never actually refuses a call
(although a session may be dropped by its user when the user finds
continuation untenable). The central notion is that when the
capacity available for a set of variable rate sessions has been
overbooked, traffic may be randomly dropped from lower precedence
sessions to allow a higher precedence session in. This has a number
of ramifications that make it inappropriate in the Internet. A key
issue is that it affects not a single session but a class of sessions
- all sessions of lower precedence than the protected session(s). A
video example will suffice for the present. Multimedia data streams
and sensor traffic often build on information in previous frames, and
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their content spans multiple datagrams in the same frame. The loss
of a datagram forces the codec into a recovery mode that reduces
image quality for at least one frame, and may cause the image to
freeze for multiple seconds. This is readily observed on television,
where screen artifacts are very visible. Scattered random datagram
loss results in all sessions in the class being impacted to some
degree. Hence, it is far more suitable to drop an entire session
(and therefore impact only one session) than to impact all sessions
in a class in a manner that consumes the available bandwidth but
delivers sub-SLA service to an entire class of sessions. It also
exposes the precedence level of each session in the clear.
2.2.1. Capacity admission control by assumption
The first approach is to ignore the matter entirely. If one assumes
that the capacity available to the application is uniformly far in
excess of its requirements, it is perhaps overhead that can be
ignored. This assumption is currently made in Internet VoIP
offerings such as Skype and Vonage; the end user is responsible to
place his service on a LAN connected to the Internet backbone by a
high speed broadband connection and use capable ISPs to deliver the
service. The only "authorization" verified is that the user pays his
bills; no capacity admission is considered because there is a clear
separation from the application service provider admitting the calls
and the access network provider admitting the traffic. The two have
no way of knowing about each other, except in the abstract sense.
2.2.2. Capacity admission control by call counting
The H.323 gatekeeper, originally specified in 1996, operates on the
model that the considerations of Section 2.2.1 generally apply, and
that it is therefore sufficient to count calls in order to ensure
that any bottlenecks in the network are never overloaded. Which
phone is calling which phone is configured information into the
Gatekeeper, ensuring it doesn't admit too many calls across a low
speed link. The area of influence of a Gatekeeper is called a Zone,
and limits how far away a Gatekeeper can influence calls. This is
because call counting doesn't scale when more than one server is
admitting flows across the same limited speed links. This approach
is consistent with the original design of H.323, which in 1996 was a
mechanism for connecting H.320 media gateways across a LAN. VoIP has
come a long way since then, however, and the engineering trade-offs
this approach requires in complex networks are unsatisfactory.
SIP provides the option to go down another path, to admit its servers
at layer 7, have no awareness of lower layer connectivity, resulting
in a divorce from infrastructure knowledge - save for [RFC3312],
which binds the two, but only at the endpoints.
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In short, if there is a bottleneck anywhere in the network that might
be used to connect two gatekeepers, SIP proxies that do not implement
or do not configure the use of [RFC3312], or other call management
systems, the amount of traffic between the two must be contained
below that bottleneck even if the normal path is of much higher
bandwidth. In addition, the multiplexing of traffic streams between
different pairs of gatekeepers over a common LAN infrastructure is
not handled by the application, and so must be managed in the
engineering of the network.
2.2.3. End-point capacity admission performed by probing the network
The IETF started looking into the use of Pre-Congestion Notification
mechanism to full fill the need of admission control for real-time
traffic. The main contribution of this work for admission control is
to allow the network to provide the network's pre-congestion
information using encoding of a field in the IP header. This network
pre-congestion information is then used for making admission control
decisions. With the decision influenced by this network pre-
congestion notification information and any applicable policy
information with possible user credentials and situational
information. The pre-congestion notification mechanism does not
limit the placement of the admission control decision point or the
signaling protocol used.
The overview of one of the current proposals is provided by
[I-D.chan-pcn-problem-statement]. With the pre-congestion
notification encoding described in [I-D.briscoe-tsvwg-cl-phb]. An
initial deployment model provided by
[I-D.briscoe-tsvwg-cl-architecture]. Another proposal is embodied in
[I-D.charny-pcn-single-marking]. Similar approaches have been
proposed in [I-D.morita-tsvwg-pps] and its related drafts, by Ivars
and Karlsson in their PBAC work, and many others.
2.2.4. Centralized capacity admission control
The concept of a Bandwidth Broker was first discussed in the research
world surrounding ESNET and Internet II in the late 1990's, and has
been discussed in the literature pertaining to the Differentiated
Services Architecture [RFC2475]. It is, in short, a central system
that performs a variety of services on behalf of clients of a network
including applying AAA services (as in [RFC2904] ) and authorizing
them to use specified capacity at specified times. Its strength is
that it is relatively simple, at least in concept, and can keep track
of simple book-keeping functions apart from network elements such as
routers. Its weakness is that it has no idea what the specific
routing of any stated data flow is, or its capacity apart from
services such as MPLS Traffic Engineering or engineering assumptions
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specified by the designers of a network. Obtaining that information
from the network via SNMP GET or other network management action can
impose a severe network overhead, and is obviously not real-time.
For scaling reasons, operational Bandwidth Brokers generally take on
a semi-distributed or fully distributed nature. They are implemented
on a per-point-of-presence basis, and in satellite networks might be
implemented in each terminal. At this point, they become difficult
to operationally distinguish from distributed capacity admission
services such as described in Section 2.2.5.
2.2.5. Distributed capacity admission control
The IETF developed the Integrated Services Model [RFC1633] and the
RSVP capacity admission protocol [RFC2205] in the early 1990's, and
then integrated it with the Differentiated Services Architecture in
[RFC2998]. Since then, the IETF has been working on a next
generation signaling protocol called NSIS [RFC4080] that can be used
for capacity admission protocol, and which is limited in scope to
considering unicast sessions. [RFC4542] looked at the issue of
providing preferential services in the Internet, and determined that
RSVP with its defined extensions could provide those services to
unicast and multicast sessions.
As with the Bandwidth Broker model, there are concerns regarding
scaling, mentioned in [RFC2208]. Present implementations that have
been measured have been found to not display the scaling concerns,
however, and in any event the use of RSVP Aggregation enables the
backbone to handle such sessions in a manner similar to an ATM
Virtual Path, bundling sessions together for capacity management
purposes.
2.3. Prioritized capacity admission control
Emergency Telecommunication Service, the US Department of Defense's
Assured Service, and e-911 each call for some form of prioritization
of some calls over others. Prioritization of the use of bandwidth is
fundamentally a matter of choices - at a point where one has multiple
choices, applying a policy that selects among them. In the PSTN,
GETS operates in favor of an authorized caller either by routing a
call that would otherwise be refused by a path unavailable to the
general public or by queuing the call until some existing call
completes and bandwidth becomes available. e-911 is similar, but the
policy is based on the called party, the emergency call center. MLPP
operates by preempting an existing call to make way for the new one.
In the Internet, routing is not performed on a per-call basis, so,
apart from interconnections to the PSTN, re-routing isn't an option.
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On the other hand, in the Internet there are more classes of traffic
than in the PSTN. In the PSTN, all calls are uses of circuits, while
in the Internet some bandwidth is always reserved for elastic
applications - at least, it must be available for routing, and there
is generally significant consideration of the web, instant messaging,
and other applications. In essence, any capacity admission policy
that differentiates between calls has the option of temporarily
borrowing bandwidth from the capacity reserved for elastic traffic by
accepting new sessions under some prioritized policy while refusing
sessions of lower priority because the threshold at that priority has
been reached.
For example, regardless of the type of capacity admission that is
used (apart from "no admission process"), one might admit prioritized
sessions using a higher bandwidth threshold than one admits lower
priority sessions.
If capacity admission as described in Section 2.2.2 is in use, the
thresholds must be set low enough that bandwidth would be available
anywhere in the network. This greatly limits the utility of such a
service due to the level of bandwidth waste that results.
If capacity admission as described in Section 2.2.3 is in use, then
multiple thresholds must be applied in marking the traffic, multiple
traffic marks must be applied, or there must be multiple ways to
interpret the result. In any event, this is only applicable in
domains in which the law of large numbers applies.
If capacity admission as described in Section 2.2.4 is in use,
thresholds can be applied related to a general policy or SLA, or
related to the network ingress and egress in use. It requires them
to maintain state regarding network traffic routing separate from the
network; to the extent that is variable, it requires direct
monitoring in the OSS.
If capacity admission as described in Section 2.2.5 is in use,
thresholds can be applied to the critical points of the path that the
traffic in question actually takes because one is asking the
equipment that the path traverses.
3. Recommendations on implementation of an Admitted Telephony Service
Class
It is the belief of the authors that either data plane PHB described
in Section 2.1, if coupled with adequate AAA and capacity admission
procedures as described in Section 2.2.5, are sufficient to provide
the services required for an Admitted Telephony service class and an
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Admitted Multimedia Conferencing Service Class. If preemption is
required, as described in section 2.3.5.2 of [RFC4542], this provides
the tools for carrying out the preemption. If preemption is not in
view, or in addition to preemptive services, the application of
different thresholds depending on call precedence has the effect of
improving the probability of call completion by admitting preferred
calls at a time that other calls are being refused. Routine and
priority traffic can be admitted using the same DSCP value, as the
choice of which calls are admitted is handled in the admission
procedure executed in the control plane, not the policing of the data
plane.
On the point of what protocols and procedures are required for
authentication, authorization, and capacity admission, we note that
clear standards do not at this time exist for bandwidth brokers, NSIS
has not at this time been finalized and in any event is limited to
unicast sessions, and that RSVP has been standardized and has the
relevant services. We therefore recommend the use of RSVP at the
UNI. Procedures at the NNI are business matters to be discussed
between the relevant networks, and are recommended but not required.
4. IANA Considerations
This note requests that IANA assign a DSCP value to a second EF
traffic class consistent with [RFC3246] and [RFC3247] in the
"Differentiated Services Field Codepoints" registry. It implements
the Telephony Service Class described in [RFC4594] at lower speeds
and is included in the Real Time Treatment Aggregate [RFC5127] at
higher speeds. The recommended value for the code point 101100,
paralleling the EF code point, which is 101110. The code point
should be referred to as VOICE-ADMIT.
This traffic class requires the use of capacity admission such as
RSVP services together with AAA services at the User/Network
Interface (UNI); the use of such services at the NNI is at the option
of the interconnected networks.
5. Security Considerations
A major requirement of this service is effective use of a signaling
protocol such as RSVP, with the capabilities to identify its user
either as an individual or as a member of some corporate entity, and
assert a policy such as "routine" or "priority".
This capability, one has to believe, will be abused by script kiddies
and others if the proof of identity is not adequately strong or if
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policies are written or implemented improperly by the carriers. This
goes without saying, but this section is here for it to be said...
6. Acknowledgements
Kwok Ho Chan offered some textual comments and rewrote Section 2.2.3.
Georgios Karagiannis offered additional comments on the same section.
The impetus for including Video in the discussion, which initially
only targeted voice, is from Dave McDysan, and text he suggested was
included. Dan Voce also commented.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
December 1998.
[RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
J., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, March 2002.
7.2. Informative References
[I-D.briscoe-tsvwg-cl-architecture]
Briscoe, B., "An edge-to-edge Deployment Model for Pre-
Congestion Notification: Admission Control over a
DiffServ Region", draft-briscoe-tsvwg-cl-architecture-04
(work in progress), October 2006.
[I-D.briscoe-tsvwg-cl-phb]
Briscoe, B., "Pre-Congestion Notification marking",
draft-briscoe-tsvwg-cl-phb-03 (work in progress),
October 2006.
[I-D.chan-pcn-problem-statement]
Chan, K., "Pre-Congestion Notification Problem Statement",
draft-chan-pcn-problem-statement-01 (work in progress),
October 2006.
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[I-D.charny-pcn-single-marking]
Charny, A., Zhang, X., Faucheur, F., and V. Liatsos, "Pre-
Congestion Notification Using Single Marking for Admission
and Termination", draft-charny-pcn-single-marking-03
(work in progress), November 2007.
[I-D.morita-tsvwg-pps]
Morita, N. and G. Karlsson, "Framework of Priority
Promotion Scheme", draft-morita-tsvwg-pps-01 (work in
progress), October 2003.
[ITU.MLPP.1990]
International Telecommunications Union, "Multilevel
Precedence and Preemption Service", ITU-T Recommendation
I.255.3, 1990.
[RFC1633] Braden, B., Clark, D., and S. Shenker, "Integrated
Services in the Internet Architecture: an Overview",
RFC 1633, June 1994.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2208] Mankin, A., Baker, F., Braden, B., Bradner, S., O'Dell,
M., Romanow, A., Weinrib, A., and L. Zhang, "Resource
ReSerVation Protocol (RSVP) Version 1 Applicability
Statement Some Guidelines on Deployment", RFC 2208,
September 1997.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, December 1998.
[RFC2904] Vollbrecht, J., Calhoun, P., Farrell, S., Gommans, L.,
Gross, G., de Bruijn, B., de Laat, C., Holdrege, M., and
D. Spence, "AAA Authorization Framework", RFC 2904,
August 2000.
[RFC2998] Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L.,
Speer, M., Braden, R., Davie, B., Wroclawski, J., and E.
Felstaine, "A Framework for Integrated Services Operation
over Diffserv Networks", RFC 2998, November 2000.
[RFC3247] Charny, A., Bennet, J., Benson, K., Boudec, J., Chiu, A.,
Courtney, W., Davari, S., Firoiu, V., Kalmanek, C., and K.
Ramakrishnan, "Supplemental Information for the New
Definition of the EF PHB (Expedited Forwarding Per-Hop
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Internet-Draft DSCPs for Capacity-Admitted Traffic February 2008
Behavior)", RFC 3247, March 2002.
[RFC3260] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, April 2002.
[RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg,
"Integration of Resource Management and Session Initiation
Protocol (SIP)", RFC 3312, October 2002.
[RFC4080] Hancock, R., Karagiannis, G., Loughney, J., and S. Van den
Bosch, "Next Steps in Signaling (NSIS): Framework",
RFC 4080, June 2005.
[RFC4190] Carlberg, K., Brown, I., and C. Beard, "Framework for
Supporting Emergency Telecommunications Service (ETS) in
IP Telephony", RFC 4190, November 2005.
[RFC4504] Sinnreich, H., Lass, S., and C. Stredicke, "SIP Telephony
Device Requirements and Configuration", RFC 4504,
May 2006.
[RFC4542] Baker, F. and J. Polk, "Implementing an Emergency
Telecommunications Service (ETS) for Real-Time Services in
the Internet Protocol Suite", RFC 4542, May 2006.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594,
August 2006.
[RFC5127] Chan, K., Babiarz, J., and F. Baker, "Aggregation of
DiffServ Service Classes", RFC 5127, February 2008.
Authors' Addresses
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Phone: +1-408-526-4257
Email: fred@cisco.com
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James Polk
Cisco Systems
Richardson, Texas 75082
USA
Phone: +1-817-271-3552
Email: jmpolk@cisco.com
Martin Dolly
AT&T Labs
Middletown Township, New Jersey 07748
USA
Phone: +1-732-420-4574
Email: mdolly@att.com
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