One document matched: draft-kappler-nsis-qosmodel-controlledload-02.txt
Differences from draft-kappler-nsis-qosmodel-controlledload-01.txt
Next Steps in Signaling C. Kappler
Internet-Draft Siemens AG
Expires: January 16, 2006 X. Fu
Univ. Goettingen
July 15, 2005
A QoS Model for Signaling IntServ Controlled-Load Service with NSIS
draft-kappler-nsis-qosmodel-controlledload-02
Status of this Memo
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This Internet-Draft will expire on January 16, 2006.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes a QoS Model to signal IntServ controlled load
service with QoS NSLP. QoS NSLP is QoS Model agnostic. All QoS
Model specific information is carried in an opaque object, the QSPEC.
This document hence specifies the QSPEC for controlled load service,
how the QSPEC must be processed in QoS NSLP nodes, and how QoS NSLP
messages must be used.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Signaling with QoS NSLP . . . . . . . . . . . . . . . . . . . 3
2.1 QoS NSLP . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 QSPEC . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 QoS Model . . . . . . . . . . . . . . . . . . . . . . . . 5
3. IntServ Controlled Load Service . . . . . . . . . . . . . . . 5
4. NSIS QoS Model for IntServ Controlled Load Service . . . . . . 6
4.1 Role of QNEs . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 QSPEC . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2.1 Controlled Load Service Requirements . . . . . . . . . 7
4.2.2 QOSM ID . . . . . . . . . . . . . . . . . . . . . . . 7
4.2.3 QSPEC Control Information . . . . . . . . . . . . . . 8
4.2.4 QoS Description . . . . . . . . . . . . . . . . . . . 8
4.3 Usage of QoS-NSLP Messages . . . . . . . . . . . . . . . . 9
5. Processing Rules in QNEs . . . . . . . . . . . . . . . . . . . 10
6. Interoperation with Controlled Load Service Specified in
RFC2211 . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1 Normative References . . . . . . . . . . . . . . . . . . . 14
9.2 Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 17
A. Appendix -- QSPEC Format for Controlled Load QOSM . . . . . . 17
B. Changes since 01 . . . . . . . . . . . . . . . . . . . . . . . 19
C. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . 20
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1. Introduction
The QoS NSIS Signaling Layer Protocol, QoS-NSLP [19] defines how to
signal for QoS reservations in the Internet. The protocol is not
bound to a specific mechanism for achieving QoS, such as IntServ or
DiffServ. Rather, the actual QoS information is carried opaquely in
the protocol in a separate object, the QSPEC [19]. A method for
achieving QoS a for a traffic flow is called QoS model. It is
expected that a number of QoS models will be developed for QoS-NSLP.
Examples are [6] and [7] and this draft.
The purpose of this document is to describe a QoS model for
controlled-load service of IntServ [5]. [10] specifies how to signal
for controlled-load service with RSVP. This document describes how
to signal for the same service with QoS-NSLP.
The controlled-load service is rather minimal both in terms of
information that is signaled - basically bandwidth in the form of a
token bucket - and in terms of prescribed realization of the service
in the network. It is therefore suited for a wide range of
realizations, such as reserving resources per-flow per-network node
[8], achieving QoS in appropriately engineered DiffServ networks with
admission control [16], or across IP tunnels or MPLS Label Switched
Paths (LSPs) with reserved bandwidths and admission control [14]
[17].
The document is structured as follows: It gives a brief overview of
QoS-NSLP and the QSPEC, and the content and features of a QoS model
as described in [19] and [4]. It then gives a brief overview of the
controlled-load service of IntServ. Subsequently, the actual QoS
model for controlled-load service is described.
2. Signaling with QoS NSLP
2.1 QoS NSLP
QoS NSLP [19] is an NSIS signaling layer protocol for signaling QoS
reservations in the Internet. Together with GIMPS [18], it provides
functionality similar to RSVP and extends it, e.g. by supporting both
sender-initiated and receiver-initiated reservations. QoS-NSLP
however does not support multicast. QoS NSLP establishes and
maintains reservation state in QoS-NSLP aware nodes, called QNEs,
along the path of a data flow. The number or frequency of QNEs is
not prescribed. The node initiating a reservation request is called
QNI, the node terminating the request is called QNR. QNI and QNR are
also QNEs, and are not necessarily the actual sender and receiver of
the data flow they are signaling for as they may also be proxying for
them.
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QoS-NSLP defines four message types, RESERVE, QUERY, RESPONSE and
NOTIFY. The message type identifies whether a message manipulates
state (e.g. RESERVE) or not (e.g. QUERY, RESPONSE). The RESERVE
message is used to create, refresh, modify or remove reservation
state in QNEs. The QUERY message is used to request information
about the data path without making a reservation. This functionality
can be used to 'probe' the path for certain characteristics. The
RESPONSE message is used to provide information about the results of
a previous RESERVE or QUERY message, e.g. confirmation of a
successful reservation, error, or for transferring results of a QUERY
back towards the querying node. The NOTIFY message is not important
in the context of this memo.
2.2 QSPEC
QoS NSLP carries QoS Model specific information encapsulated in an
opaque object, the QSPEC [4]. The QSPEC thus fulfills a similar
purpose as TSpec, RSpec and AdSpec in RSVP [9]. The QSPEC is not
interpreted by the QoS NSLP Processing unit on a QNE, but passed
as-is to the Resource Management Function RMF on the same node, where
it is interpreted.
The QSPEC is structured internally into QSPEC Control Information,
and QoS Description.
o QSPEC Control Information contains parameters that govern the
processing of the resource request in the RMF, e.g. information on
excess treatment.
o QoS Description is composed of QSPEC objects, namely QoS Desired,
QoS Available, QoS Reserved and Minimum QoS. A particular QoS
Description typically only contains a subset of these objects.
* QoS Desired contains parameters describing the QoS desired by a
QNI.
* QoS Available contains parameters describing the available
resources. In the controlled load service QOSM, this QSPEC
object is used to collect information on the available
bandwidth along a path.
* QoS Reserved describes the actual QoS reserved.
* Minimum QoS can be included by a QNI together with QoS Desired
to signal a range of QoS (between QoS Desired and Minimum QoS)
is acceptable.
The QSPEC template [4] defines a number of mandatory and optional
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QSPEC parameters. Mandatory parameters must be interpreted by each
QNE, whereas optional parameters can also be ignored. This ensures
some degree of interoperability between QoS Models while at the same
time providing extensibility and flexibility. In a given QoS Model,
new optional parameters may be defined.
The QSPEC usually carries a QoS Model identifier, which identifies
what QoS Model is being signaled about. This QoS Model defines what
parameters must be included in a given QSPEC. However, the QNI may
also include additional parameters, in order to give additional
information to QNEs that are not supporting this specific QoS Model.
2.3 QoS Model
A QoS-enabled domain supports a particular QoS model (QOSM), which is
a method to achieve QoS for a traffic flow, such as IntServ
Controlled Load or DiffServ [13]. QoS NSLP is independent of the
QOSM, just as RSVP [9] is independent of IntServ. A QOSM hence
incorporates QoS provisioning methods and a QoS architecture. It
however also defines how to use QoS NSLP. It therefore defines the
behavior of the resource management function (RMF), including inputs
and outputs, and how QSPEC information on traffic description,
resources required, resources available, and control information
required by the RMF is interpreted. A QOSM also specifies the QSPEC
parameters that describe the QoS and how resources will be managed by
the RMF.
3. IntServ Controlled Load Service
As specified in [5], the controlled-load service defined for IntServ
supports applications which are highly sensitive to overload
conditions, e.g. real-time applications. The controlled-load service
provides to an application approximately the end-to-end service of an
unloaded best-effort network. "Unloaded" thereby is used in the
sense of "not heavily loaded or congested" rather than in the sense
of "no other network traffic whatsoever".
The definition of controlled-load service is intentionally imprecise.
It implies a very high percentage of transmitted packets will be
successfully delivered to the end nodes. Furthermore, the transit
delay experienced by a very high percentage of the delivered packets
will not greatly exceed the minimum transmit delay experienced by any
successfully delivered packet. In other words, a short disruption of
the service is viewed as statistical effect which may occur in normal
operation. Events of longer duration are indicative of failure to
allocate sufficient resources to the controlled-load flow.
In order to ensure that the conditions on controlled-load service are
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met, clients requesting the service provide network elements on the
data path with an estimation of the data traffic they are going to
generate. When signaling with RSVP, the object carrying this
estimation is called TSpec. In return, the service ensures that in
each network element on the data path, resources adequate to process
traffic falling within this descriptive envelope will be available to
the client. This must be accomplished by admission control.
The controlled-load service is implemented per-flow in each network
element on the data-path. Thereby, a network element may be an
individual node such as a router. However, a network element can
also be a subnet, e.g. a DiffServ cloud within a larger IntServ
network [16]. In this case, the per-flow traffic description (e.g.
carried in the RSVP TSpec) together with the DiffServ Code Point
(carried e.g. in the DCLASS object [15] of RSVP) is used for
admission control into the DiffServ cloud. The DiffServ cloud must
ensure it provides controlled-load service. It is also possible to
operate controlled-load service over logical links such as IP tunnels
[14] or MPLS LSPs [17]. The per-flow traffic descriptor is in this
case used for admission control into the tunnel /LSP.
4. NSIS QoS Model for IntServ Controlled Load Service
According to [4], a QOSM SHOULD include the following information:
o Role of QNEs in this QOSM: E.g. location, frequency, statefulness
etc.
o QSPEC Definition: A QOSM SHOULD specify the QSPEC, including QSPEC
parameters. Furthermore it needs to explain how mandatory QSPEC
parameters not used in this QOSM are mapped onto parameters
defined therein.
o State Management: It describes how QSPEC info is treated and
interpreted in the RMF and QOSM specific processing. E.g.
admission control, scheduling, policy control, QoS parameter
accumulation (e.g. delay).
Operation and Sequence of Events, i.e. what QSPEC procedures to use
to signal the QOSM. Message Format and QSPEC objects to be carried
in RESERVE, QUERY RESPONSE and NOTIFY.
Subsequent sections treat these points one-by-one.
4.1 Role of QNEs
Controlled-load service network elements can be individual routers or
subnets. I.e. it is not necessary for each network node on the data
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path to interpret the signaling for the service. Rather, dedicated
nodes may interpret signaling information and take on responsibility
that the subnet they represent delivers adequate service. In fact,
this setting maps nicely onto QoS-NSLP - and the NSIS protocol suite
in general. In NSIS, QNEs are just required to be located on the
data path. However there are no prescriptions regarding their number
or frequency. Hence, in the controlled-load QoS model, there must be
(at least) one QNE acting on behalf of every network element. E.g.
all ingress routers to a DiffServ cloud could be QNEs, performing
admission control. If there is more than one QNE per network
element, they must be coordinated among themselves to ensure the
network element delivers controlled-load service. Controlled Load
QNEs are always stateful.
4.2 QSPEC
4.2.1 Controlled Load Service Requirements
The controlled-load service QOSM uses Token_Bucket parameters[4],
which consist of a token bucket specification plus a peak rate (p), a
minimum policed unit (m) and a maximum packet size (M) to describe a
data flow's required resources. The token bucket specification
includes a bucket rate r and a bucket depth b. The minimum policed
unit m is an integer measured in bytes. All IP datagrams of size
less than m are counted against the token bucket as being of size m.
For more details, including value ranges of the parameters see [10].
The controlled-load service has no required characterization
parameters the QNI needs to be informed about, i.e. current
measurement and monitoring information need not be exported by QNEs,
although individual implementations may do so if they wish.
When using RSVP to signal for controlled-load services, the PATH
message collects information on MTU and available bandwidth which is
used by the receiver to adapt the reservation parameters in the
RESERVE message [10][11]. It is hence related to the signaling for
Controlled Load rather than to the Controlled Load Service itself.
Indeed, While collecting path MTU can be useful for achieving QoS, it
is not considered to be part of QoS signaling or QOSMs [4] in NSIS;
rather, an independent path MTU discovery mechanism (e.g., [22])
during the flow setup phase is assumed to provide means to learn
about the path MTU. Available bandwidth may be collected if desired
and used for controlled load service QOSM.
4.2.2 QOSM ID
Later versions of this document will define a QOSM ID.
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4.2.3 QSPEC Control Information
QSPEC Control Information for controlled load service QOSM provides
information about QOSM support situation along the path followed by a
data flow. In addition, information on Excess Treatment (drop or
reshape) MAY be included.
In RSVP, when non-IntServ hops are discovered on the path, a flag is
raised. Additionally, the number of IntServ hops is counted. This
way a sender or receiver can determine whether end-to-end QoS could
be achieved. The QSPEC template defines a similar parameter, namely
the <NON QOSM Hop> flag. It is set to 1 if a QNE unaware of
Controlled Load Service is encountered on the path from the QNI to
the QNR. Discussions: per [4], <NON QOSM Hop> is just a flag;
counting the number of non QOSM hops is currently a function of QoS
NSLP.
Furthermore, Excess Treatment parameter MAY be included in the
control information. Current supported values are "reshape" or
"drop" and the default value (if the parameter is not included in the
Control Information) is "reshape". This parameter is used for a
controlled load service implementation to handle the received data
traffic belonging to a controlled load flow which is "non-conformant"
to the Token Bucket specification reserved. Traffic is considered
"non-conformant" when:
over time period T, the amount of data received exceeds rT+b; or
data rate of the traffic exceeds the peak rate p; or
data packet size is larger than M or the QNE's outgoing link MTU
4.2.4 QoS Description
QoS Description can be part or all of the following objects:
<QoS Desired> = <Token Bucket>
<QoS Available> = <Available Bandwidth>
<Minimum QoS> = <Token Bucket>
<QoS Reserved> = <Token Bucket>
Among them, at least <QoS Desired> and <QoS Reserved> MUST be
supported by all controlled load service QOSM implementations.
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<QoS Available> is required for receiver-initiated reservations, and
MAY be used in sender-initiated reservations. It is used for
gathering available bandwidth information along the path. This
information can be used by QNI (or QNR, for receiver-initiated
reservations) to make an appropriate reservation thereafter,
particularly to re-issue a failed reservation.
<Minimum QoS> is optional. It always travels together with <QoS
Desired>. It signifies that the QNI can accept a downgrade of
resources for particular parameters in the reservation, down to the
value of the respective parameter in <Minimum QoS>. For parameters
not appearing in <Minimum QoS>, it cannot accept a downgrade. For
controlled load service this means if <token bucket> is included, a
downgrade of all token bucket parameters is possible.
In all QSPEC objects additional parameters MAY be included, as
described in [4].
4.3 Usage of QoS-NSLP Messages
QoS-NSLP allows a variety of message sequences for reserving
resources ("QSPEC Procedures"). Particularly, sender-initiated,
receiver-initiated and bi-directional messages are possible. E.g.,
in sender-initiated reservations, a RESERVE is issued by the QNI. If
the reservation is successful, the QNR replies with a RESPONSE. If
the reservation fails, the QNE at which it failed sends a RESPONSE
(QoS NSLP is not quite clear on this).
The QSPEC template defines what QSPEC objects are carried in which of
these messages, and how they are translated from message-to-message.
For each of the message patterns defined in QoS NSLP, a variety of
QSPEC object usages is possible.
o in the simplest message sequence, sender-initiated reservations,
the RESERVE may carry just <QoS Desired> to indicate the exact QoS
it wants, and the corresponding RESPONSE carries solely <QoS
Reserved>. This implies either the exact resources described in
<QoS Desired> are reserved, or the reservation fails.
o A more advanced QNI would include, in addition to <QoS Desired>, a
<QoS Available> QSPEC object, or even a <Minimum QoS>. <QoS
Available> allows collecting path properties, e.g. currently
available bandwidth, and <Minimum QoS> signals that (and how much)
less resources than <QoS Desired> are acceptable. The RESPONSE
message carries <QoS Reserved>, and additionally copies the <QoS
Available> QSPEC Object from RESERVE. This information may be of
particular interest if a reservation failed. Note however, that
since the QNE failing the reservation sends the RESPONSE, no
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complete e2e information on e.g. bandwidth can be collected and
delivered to the QNI. Generally, it needs to be discussed what is
the most efficient way of providing feedback to the QNI for
sender-initiated reservations.
Note that the initial message triggering the signaling exchange fully
determines the sequencing of subsequent messages, and also determines
what QSPEC objects will be carried in them. That is, while the QNI
has freedom in choosing a particular messaging method, the resulting
method is also uniquely determined.
The controlled load service parameters can be signaled with any of
the message exchanges and QSPEC object combinations defined. Note,
in contrast, in RSVP only one type of message exchange is defined
(receiver-initiated reservations, and the equivalent of <Minimum QoS>
= 0>). However, this is a characteristic of RSVP rather than of the
controlled load service.
5. Processing Rules in QNEs
Admission Control:
For controlled-load service, QNEs are required to perform
admission control. All resources important to the operation of
the network element must be considered when admitting a request.
Common examples of such resources include link bandwidth, router
or switch port buffer space, and computational capacity of the
packet forwarding engine. It is not prescribed how a QNE
determines adequate resources are available. It is however
required that they make bandwidth greater than the token rate
available to the flow in certain situations in order to account
for fluctuations. E.g. statistical methods may be used to
determine how much bandwidth is necessary.
During the admission control, the controlled-load service Token
Bucket parameters MUST be met according to the following rule: a
Token Bucket A to be allocated for a flow MUST be "as good or
better than" or "greater than or equal to" Token Bucket B (which
is carried in the received QoS Description, e.g., QoS_Desired, or
Minimum_QoS if available), i.e.,:
the token bucket rate r for Token Bucket A is greater than or
equal to that of Token Bucket B, and
the token bucket depth b for Token Bucket A is greater than or
equal to that of Token Bucket B, and
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the peak rate p for Token Bucket A is greater than or equal to
that of Token Bucket B, and
the minimum policed unit m for Token Bucket A is less than or
equal to that of Token Bucket B, and
the maximum packet size M of Token Bucket A is greater than or
equal to that of Token Bucket B.
Remark: these rules come originally from rules for ordering token
buckets in [5].
There are no target values for other parameters, e.g. delay or
loss, other than providing a service closely equivalent to that
provided to best-effort traffic under lightly loaded conditions.
Although path MTU discovery is not necessarily part of the
controlled load service QOSM, controlled load service QOSM QNEs
must reject a service request (by returning an admission control
error) if the maximum packet size M signaled in <QoS Desired>,
resp. in <Minimum QoS> if available, is bigger than the MTU of the
segment of the path managed by this QNE.
Resource requests for new flows are accepted if capacity is
available. Reservation modifications are accepted if the new
<token bucket> is strictly smaller than the old one. Otherwise
they are treated like new reservations from an admission control
perspective.
Packet Scheduling and Excess Treatment:
A QNE MUST ensure the Token Bucket requirements for any individual
flow given at setup time are met locally. That is, traffic MUST
obey the rule that over all time periods, the amount of data sent
does not exceed rT+b. Packets smaller than m are counted as of
size m. A basic requirement for packet scheduling is that the QNE
MUST ensure the QoS requirements are met for traffic belonging to
flows whose traffic are all conformant.
In presence of arriving non-conformant traffic, the QNE MUST
behave as follows:
the QNE MUST continue to provide the contracted QoS for traffic
belonging to flows which are all conformant.
the QNE SHOULD prevent excess control load traffic from
unfailrly impacting the handling of arriving best-effort
traffic.
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While fulfiling the above two requirements, the QNE MUST
attempt to forward the excess traffic on a best-effort basis if
sufficient resources are available.
Several basic approaches are suggested in [5] and reused here,
although other alternatives should be possible, if available. A
simple approach is the priority mechanism, namely, to let the QNE
to process excess controlled-load traffic at a lower priority than
the elastic best-effort traffic, especially when the most
controlled-load traffic arises from non-rate-adaptive real-time
applications.
The second approach is that a QNE can maintain separate flow
classes (e.g., one for each non-conformant controlled-load
traffic, one for inelastic best-effort flows, and another from
elastic best-effort flows), where packet scheduling mechanisms
like Fair Queueing or Weight Fair Queueing can be used. One
implementation, for instance, could allocate each controlled-load
flow a 1/N "fair share" percentage of the available best effort
bandwidth for its excess traffic.
Finally, Random Early Detection (RED) queueing mechanism may be
used.
6. Interoperation with Controlled Load Service Specified in RFC2211
Controlled load service QOSM is intended to be consistent with the
RSVP/Controlled Load Service specified in [5], although the used
signaling protocols are QoS-NSLP and RSVP, respectively. This
section discusses the service and parameter mapping between them
needed for service mapping.
There are following possible parameter mappings:
CLS ADSpec => QoS Available (Available Bandwidth)
CLS Sender_TSpec + FlowSpec => Token Bucket(s) for QoS Desired
(+optionally Minimum QoS)
Note that under Controlled-load QOM, there is no MTU discovery as in
RSVP/CLS, where path MTU is a mandatory parameter. This could relief
the QNE from being overloaded with the orthogonal task of determining
path MTU.
The ADSpec to QoS Available mapping is probably the easiest, where
available bandwidth information along a path would be determined by
RSVP Path or QoS-NSLP Query messages.
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Other QoS parameters, such as RSVP Sender_TSpec and FlowSpec are
connected to the two-pass, receiver-initiated reservation procedure
and partially the support for multicast in RSVP. In receiver-
initiated reservations using QoS-NSLP, both TSpec and FlowSpec are
merged in a single RESERVE message, with the flexibility of choosing
between a QoS Desired and a Minimum QoS Token Bucket. The FlowSpec
is equivalent to QoS Desired (if Minimum QoS is not present) or a
Token Bucket between QoS Desired and Minimum QoS (if Minimum QoS is
present), reducing the need for another additional reservation
process if failing to satisfy the first FlowSpec. However, the
Sender_TSpec does not exist in QoS-NSLP Query messages.
7. Security Considerations
This Internet Draft raises no new security issues.
8. Conclusions
This document describes a QoS Model to signal IntServ controlled load
service with QoS NSLP. Up to now, it was only described how to
signal for IntServ controlled load service with RSVP. Since no
independent document exists that describes IntServ controlled load by
its own, i.e. without RSVP, it is sometimes difficult to determined
what features are specific to IntServ controlled load, and which
features are specific to RSVP:
Is it indeed vital for QNIs signaling for controlled load service
to be informed about the number of hops not implementing this
QOSM? Since the controlled load QOSM exclusivly relies on
mandatory parameters it can be expected that all QNEs can make
sense of the reservation, independent of whether they explicitly
implement controlled load service or not. Of more interest
appears the number of non-QoS-NSLP hops (which is collected in the
main message body of QoS NSLP rather than in the QSPEC).
The QoS NSLP QOSM for controlled load service allows a variety of
message exchanges all eventually resulting in a reservation, e.g.
sender-initiated, receiver-initiated and bidirectional signaling.
The controlled load service when signaled with RSVP was bound to
sender-initiated reservations.
When signaling with RSVP, it is not possible to define a range of
acceptable QoS. Also this seems to be a charcteristic of RSVP
rather than a feature of the controlled load service.
RSVP allows discovery of path MTU. Since independent mechanisms
area exist to this end, this feature has not been reproduced by
the Controlled Load QOSM (and QoS NSLP in general)
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An issue of general interest discovered here concerns feedback of
information in sender-initiated scenarios (In receiver-initiated
scenarios it does not occurr because path information is collected
before the RESERVE is issued). A QNI may include in <QoS Available>
several parameters, e.g. bandwidth, which it would like to measure
along the data path. If the reservation fails, e.g. because the
desired bandwidth was to large, the QNE failing the reservation
returns a RESPONSE, including the <QoS Available> QSPEC object with
accumulated information up to this point. The QNI can learn from
this why the reservation failed at this particular QNE. However it
cannot be sure a subsequent downgraded RESERVE will be more
successful. This is because there may be even more difficult
conditions (e.g. even less bandwidth) down the path. That is, in
sender-initiated scenarios it is not straightforward to receive
feedback from a failed reservation that allows to make a good guess
at what size of reservation would be more successful. Of course it
would be possible for the QNI to issue a QUERY first to find out
about a suitable value for, e.g. maximum packet size. However this
adds another round-trip time to the reservation, thereby obsoleting
one of the main benefits of sender-initiated reservations compared to
receiver-initiated ones.
Another issue is that <QoS Desired> may also include <QoS Class>. Is
it useful for Controlled Load Service QOSM?
In this draft, the feedback problem is solved by including a <Minimum
QoS> QSPEC object in sender-initated reservations. This gives some
flexibility as it implicitly says the QNI would also accept a
downgraded reservation, up to the value specified. When the maximum
packet size in <Minimum QoS> is set to a very small value
reservations are not going to fail because of the MTU problem. Note
however as currently specified in [19], the <Minimum QoS> QSPEC
object is not necessarily supported by all QNEs.
9. References
9.1 Normative References
[1] Brunner, M., "Requirements for Signaling Protocols", RFC 3726,
April 2004.
[2] Swale, R., Mart, P., Sijben, P., Brim, S., and M. Shore,
"Middlebox Communications (midcom) Protocol Requirements",
RFC 3304, August 2002.
[3] Chaskar, H., "Requirements of a Quality of Service (QoS)
Solution for Mobile IP", RFC 3583, September 2003.
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[4] Ash, J., "QoS-NSLP QSPEC Template", draft-ietf-nsis-qspec-05
(work in progress), July 2005.
[5] Wroclawski, J., "Specification of the Controlled-Load Network
Element Service", RFC 2211, September 1997.
9.2 Informative References
[6] Bader, A., "RMD-QOSM - The Resource Management in Diffserv QOS
Model", draft-ietf-nsis-rmd-03 (work in progress), July 2005.
[7] Ash, J., "Y.1541-QOSM -- Y.1541 QoS Model for Networks Using
Y.1541 QoS Classes", draft-ash-nsis-y1541-qosm-00 (work in
progress), May 2005.
[8] Braden, B., Clark, D., and S. Shenker, "Integrated Services in
the Internet Architecture: an Overview", RFC 1633, June 1994.
[9] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin,
"Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
Specification", RFC 2205, September 1997.
[10] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[11] Shenker, S. and J. Wroclawski, "General Characterization
Parameters for Integrated Service Network Elements", RFC 2215,
September 1997.
[12] Shenker, S. and J. Wroclawski, "Network Element Service
Specification Template", RFC 2216, September 1997.
[13] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W.
Weiss, "An Architecture for Differentiated Services", RFC 2475,
December 1998.
[14] Terzis, A., Krawczyk, J., Wroclawski, J., and L. Zhang, "RSVP
Operation Over IP Tunnels", RFC 2746, January 2000.
[15] Bernet, Y., "Format of the RSVP DCLASS Object", RFC 2996,
November 2000.
[16] 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.
[17] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label
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Internet-Draft Controlle-Load QOSM July 2005
Switching Architecture", RFC 3031, January 2001.
[18] Schulzrinne, H. and R. Hancock, "GIMPS: General Internet
Messaging Protocol for Signaling", draft-ietf-nsis-ntlp-06
(work in progress), May 2005.
[19] Bosch, S., Karagiannis, G., and A. McDonald, "NSLP for Quality-
of-Service signaling", draft-ietf-nsis-qos-nslp-06 (work in
progress), February 2005.
[20] Stiemerling, M., "NAT/Firewall NSIS Signaling Layer Protocol
(NSLP)", draft-ietf-nsis-nslp-natfw-06 (work in progress),
May 2005.
[21] "Path Computation Element (pce) Charter,
http://www.ietf.org/html.charters/pce-charter.html", 2005.
[22] "Path MTU Discovery (pmtud) Charter,
http://www.ietf.org/html.charters/pmtud-charter.html", 2005.
[23] "IP Flow Information Export (ipfix) Charter,
http://www.ietf.org/html.charters/ipfix-charter.html", 2005.
[24] 3GPP, "IP Multimedia Subsystem (IMS); Stage 2", 3GPP TS 23.228
5.13.0, January 2005.
[25] "NGN QoS Framework and Requirements", DTS/TISPAN-05009-NGN.
[26] Lee, S., "Applicability Statement of NSIS Protocols in Mobile
Environments",
draft-ietf-nsis-applicability-mobility-signaling-01 (work in
progress), February 2005.
[27] Herzog, S., Boyle, J., Cohen, R., Durham, D., Rajan, R., and A.
Sastry, "COPS usage for RSVP", RFC 2749, January 2000.
[28] Alfano, F., "Diameter Quality of Service Application",
draft-alfano-aaa-qosprot-02 (work in progress), February 2005.
[29] Farrel, A., "Path Computation Element (PCE) Architecture",
draft-ietf-pce-architecture-00 (work in progress), March 2005.
[30] Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture
for Describing Simple Network Management Protocol (SNMP)
Management Frameworks", STD 62, RFC 3411, December 2002.
[31] Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie, K.,
Herzog, S., Reichmeyer, F., Yavatkar, R., and A. Smith, "COPS
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Internet-Draft Controlle-Load QOSM July 2005
Usage for Policy Provisioning (COPS-PR)", RFC 3084, March 2001.
[32] Yang, L., Dantu, R., Anderson, T., and R. Gopal, "Forwarding
and Control Element Separation (ForCES) Framework", RFC 3746,
April 2004.
Authors' Addresses
Cornelia Kappler
Siemens AG
Siemensdamm 62
13627 Berlin
Germany
Email: cornelia.kappler@siemens.com
Xiaoming Fu
University of Goettingen
Institute for Informatics
Lotzestr. 16-18
Goettingen 37083
Germany
Email: fu@cs.uni-goettingen.de
Appendix A. Appendix -- QSPEC Format for Controlled Load QOSM
This section provides an example format for QSPEC used by controlled
load QOSM in a successful sender-initiated reservation. Other
scenarios can be easily derived by adapting to the QoS-NSLP signaling
procedure and used QoS specifications.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|QOSM_ID= TBD | QSPEC_Lenth = 64| NON QOSM Hop | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=0(ctrl) | Obj_Lenth = 4 | Excess treatm.| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=1(QoSDe)| Obj_Lenth = 24| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=2(QoSAv)| Obj_Lenth = 8 | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| available bandwidth (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=4(MiQoS)| Obj_Lenth = 24| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig. 1 An Example QSPEC for sender initiated reservation (RESERVE)
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|QOSM_ID= TBD | QSPEC_Lenth = 40| NON QOSM Hop | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=0(ctrl) | Obj_Lenth = 4 | Excess treatm.| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=3(QoSDe)| Obj_Lenth = 24| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Rate [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Bucket Size [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Data Rate [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Policed Unit [m] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size [M] (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Obj_ID=2(QoSAv)| Obj_Lenth = 8 | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| available bandwidth (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig. 2 An Example QSPEC for sender initiated reservation (RESPONSE)
Appendix B. Changes since 01
1. Clarifications about path MTU, scheduling/excess treatment and
QOSM Hops.
2. Added a section "Interoperation with RFC2211" and QSPEC format as
Appendix.
Appendix C. Acknowledgements
The author would like to thank Andrew McDonald for fruitful
discussions.
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