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IETF RFC 5976
Y.1541-QOSM: Model for Networks Using Y.1541 Quality-of-Service Classes
Last modified on Wednesday, October 6th, 2010
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Internet Engineering Task Force (IETF) G. Ash
Request for Comments: 5976 A. Morton
Category: Experimental M. Dolly
ISSN: 2070-1721 P. Tarapore
C. Dvorak
AT&T Labs
Y. El Mghazli
Alcatel-Lucent
October 2010
Y.1541-QOSM: Model for Networks Using Y.1541 Quality-of-Service Classes
 Abstract
This document describes a QoS-NSLP Quality-of-Service model (QOSM)
based on ITU-T Recommendation Y.1541 Network QoS Classes and related
guidance on signaling. Y.1541 specifies 8 classes of Network
Performance objectives, and the Y.1541-QOSM extensions include
additional QSPEC parameters and QOSM processing guidelines.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 5976.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Ash, et al. Experimental PAGE 1 
RFC 5976 Y.1541 QOSM October 2010
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Summary of ITU-T Recommendations Y.1541 and Signaling
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Description of Y.1541 Classes . . . . . . . . . . . . . . 4
2.2. Y.1541-QOSM Processing Requirements . . . . . . . . . . . 6
3. Additional QSPEC Parameters for Y.1541 QOSM . . . . . . . . . 7
3.1. Traffic Model (TMOD) Extension Parameter . . . . . . . . . 7
3.2. Restoration Priority Parameter . . . . . . . . . . . . . . 8
4. Y.1541-QOSM Considerations and Processing Example . . . . . . 10
4.1. Deployment Considerations . . . . . . . . . . . . . . . . 10
4.2. Applicable QSPEC Procedures . . . . . . . . . . . . . . . 10
4.3. QNE Processing Rules . . . . . . . . . . . . . . . . . . . 10
4.4. Processing Example . . . . . . . . . . . . . . . . . . . . 10
4.5. Bit-Level QSPEC Example . . . . . . . . . . . . . . . . . 12
4.6. Preemption Behavior . . . . . . . . . . . . . . . . . . . 14
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5.1. Assignment of QSPEC Parameter IDs . . . . . . . . . . . . 14
5.2. Restoration Priority Parameter Registry . . . . . . . . . 14
5.2.1. Restoration Priority Field . . . . . . . . . . . . . . 14
5.2.2. Time to Restore Field . . . . . . . . . . . . . . . . 15
5.2.3. Extent of Restoration Field . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . . 17
Ash, et al. Experimental PAGE 2
RFC 5976 Y.1541 QOSM October 2010
1. Introduction
This document describes a QoS model (QOSM) for Next Steps in
Signaling (NSIS) QoS signaling layer protocol (QoS-NSLP) application
based on ITU-T Recommendation Y.1541 Network QoS Classes and related
guidance on signaling. [Y.1541] currently specifies 8 classes of
Network Performance objectives, and the Y.1541-QOSM extensions
include additional QSPEC [RFC 5975] parameters and QOSM processing
guidelines. The extensions are based on standardization work in the
ITU-T on QoS signaling requirements ([Y.1541] and [E.361]), and
guidance in [TRQ-QoS-SIG].
[RFC 5974] defines message types and control information for the QoS-
NSLP that are generic to all QOSMs. A QOSM is a defined mechanism
for achieving QoS as a whole. The specification of a QOSM includes a
description of its QSPEC parameter information, as well as how that
information should be treated or interpreted in the network. The
QSPEC [RFC 5975] contains a set of parameters and values describing
the requested resources. It is opaque to the QoS-NSLP and similar in
purpose to the TSpec, RSpec, and AdSpec specified in [RFC 2205] and
[RFC 2210]. A QOSM provides a specific set of parameters to be
carried in the QSPEC object. At each QoS NSIS Entity (QNE), the
QSPEC contents are interpreted by the resource management function
(RMF) for purposes of policy control and traffic control, including
admission control and configuration of the scheduler.
1.1. 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 [RFC 2119].
2. Summary of ITU-T Recommendations Y.1541 and Signaling Requirements
As stated above, [Y.1541] is a specification of standardized QoS
classes for IP networks (a summary of these classes is given below).
Section 7 of [TRQ-QoS-SIG] describes the signaling features needed to
achieve end-to-end QoS in IP networks, with Y.1541 QoS classes as a
basis. [Y.1541] recommends a flexible allocation of the end-to-end
performance objectives (e.g., delay) across networks, rather than a
fixed per-network allocation. NSIS protocols already address most of
the requirements; this document identifies additional QSPEC
parameters and processing requirements needed to support the Y.1541
QOSM.
Ash, et al. Experimental PAGE 3
RFC 5976 Y.1541 QOSM October 2010
2.1. Description of Y.1541 Classes
[Y.1541] proposes grouping services into QoS classes defined
according to the desired QoS performance objectives. These QoS
classes support a wide range of user applications. The classes group
objectives for one-way IP packet delay, IP packet delay variation, IP
packet loss ratio, etc., where the parameters themselves are defined
in [Y.1540].
Note that [Y.1541] is maintained by the ITU-T and subject to
occasional updates and revisions. The material in this section is
provided for information and to make this document easier to read.
In the event of any discrepancies, the normative definitions found in
[Y.1541] take precedence.
Classes 0 and 1 might be implemented using the Diffserv Expedited
Forwarding (EF) Per-Hop Behavior (PHB), and they support interactive
real-time applications [RFC 3246]. Classes 2, 3, and 4 might be
implemented using the Diffserv Assured Forwarding (AFxy) PHB Group,
and they support data transfer applications with various degrees of
interactivity [RFC 2597]. Class 5 generally corresponds to the
Diffserv Default PHB, and it has all the QoS parameters unspecified
consistent with a best-effort service[RFC 2474]. Classes 6 and 7
provide support for extremely loss-sensitive user applications, such
as high-quality digital television, Time Division Multiplexing (TDM)
circuit emulation, and high-capacity file transfers using TCP. These
classes are intended to serve as a basis for agreements between end-
users and service providers, and between service providers. They
support a wide range of user applications including point-to-point
telephony, data transfer, multimedia conferencing, and others. The
limited number of classes supports the requirement for feasible
implementation, particularly with respect to scale in global
networks.
The QoS classes apply to a packet flow, where [Y.1541] defines a
packet flow as the traffic associated with a given connection or
connectionless stream having the same source host, destination host,
class of service, and session identification. The characteristics of
each Y.1541 QoS class are summarized here:
Class 0:
Real-time, highly interactive applications, sensitive to jitter.
Mean delay <= 100 ms, delay variation <= 50 ms, and loss ratio <=
10^-3. Application examples include VoIP and video teleconference.
Ash, et al. Experimental PAGE 4
RFC 5976 Y.1541 QOSM October 2010
Class 1:
Real-time, interactive applications, sensitive to jitter. Mean delay
<= 400 ms, delay variation <= 50 ms, and loss ratio <= 10^-3.
Application examples include VoIP and video teleconference.
Class 2:
Highly interactive transaction data. Mean delay <= 100 ms, delay
variation is unspecified, loss ratio <= 10^-3. Application examples
include signaling.
Class 3:
Interactive transaction data. Mean delay <= 400 ms, delay variation
is unspecified, loss ratio <= 10^-3. Application examples include
signaling.
Class 4:
Low Loss Only applications. Mean delay <= 1 s, delay variation is
unspecified, loss ratio <= 10^-3. Application examples include short
transactions, bulk data, and video streaming.
Class 5:
Unspecified applications with unspecified mean delay, delay
variation, and loss ratio. Application examples include traditional
applications of default IP networks.
Class 6:
Applications that are highly sensitive to loss. Mean delay <= 100
ms, delay variation <= 50 ms, and loss ratio <= 10^-5. Application
examples include television transport, high-capacity TCP transfers,
and Time-Division Multiplexing (TDM) circuit emulation.
Class 7:
Applications that are highly sensitive to loss. Mean delay <= 400
ms, delay variation <= 50 ms, and loss ratio <= 10^-5. Application
examples include television transport, high-capacity TCP transfers,
and TDM circuit emulation.
These classes enable service level agreements (SLAs) to be defined
between customers and network service providers with respect to QoS
requirements. The service provider then needs to ensure that the
requirements are recognized and receive appropriate treatment across
network layers.
Work is in progress to specify methods for combining local values of
performance metrics to estimate the performance of the complete path.
See Section 8 of [Y.1541], [RFC 5835], and [COMPOSITION].
Ash, et al. Experimental PAGE 5
RFC 5976 Y.1541 QOSM October 2010
2.2. Y.1541-QOSM Processing Requirements
[TRQ-QoS-SIG] guides the specification of signaling information for
IP-based QoS at the interface between the user and the network (UNI)
and across interfaces between different networks (NNI). To meet
specific network performance requirements specified for the Y.1541
QoS classes [Y.1541] , a network needs to provide specific user-plane
functionality at the UNI and NNI. Dynamic network provisioning at a
UNI and/or NNI node allows a traffic contract for an IP flow to be
dynamically requested from a specific source node to one or more
destination nodes. In response to the request, the network
determines if resources are available to satisfy the request and
provision the network.
For implementations to claim compliance with this memo, it MUST be
possible to derive the following service-level parameters as part of
the process of requesting service:
a. Y.1541 QoS class, 32-bit integer, range: 0-7
b. rate (r), octets per second
c. peak rate (p), octets per second
d. bucket size (b), octets
e. maximum packet size (MPS), octets, IP header + IP payload
f. Diffserv PHB class [RFC 2475]
g. admission priority, 32-bit integer, range: 0-2
Compliant implementations MAY derive the following service-level
parameters as part of the service request process:
h. peak bucket size (Bp), octets, 32-bit floating point number in
single-precision IEEE floating point format [IEEE754]
i. restoration priority, multiple integer values defined in
Section 3 below
All parameters except Bp and restoration priority have already been
specified in [RFC 5975]. These additional parameters are defined as
o Bp, the size of the peak-rate bucket in a dual-token bucket
arrangement, essentially setting the maximum length of bursts in
the peak-rate stream. For example, see Annex B of [Y.1221]
Ash, et al. Experimental PAGE 6
RFC 5976 Y.1541 QOSM October 2010
o restoration priority, as defined in Section 3 of this memo
Their QSPEC Parameter format is specified in Section 3.
It MUST be possible to perform the following QoS-NSLP signaling
functions to meet Y.1541-QOSM requirements:
a. accumulate delay, delay variation, and loss ratio across the end-
to-end connection, which may span multiple domains.
b. enable negotiation of Y.1541 QoS class across domains.
c. enable negotiation of delay, delay variation, and loss ratio
across domains.
These signaling requirements are supported in [RFC 5974], and the
functions are illustrated in Section 4 of this memo.
3. Additional QSPEC Parameters for Y.1541 QOSM
The specifications in this section extend the QSPEC [RFC 5975].
3.1. Traffic Model (TMOD) Extension Parameter
The traffic model (TMOD) extension parameter is represented by one
floating point number in single-precision IEEE floating point format
and one 32-bit reserved field.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|E|N|r| 15 |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Bucket Size [Bp] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: TMOD Extension
The Peak Bucket Size term, Bp, is represented as an IEEE floating
point value [IEEE754] in units of octets. The sign bit MUST be zero
(all values MUST be non-negative). Exponents less than 127 (i.e., 0)
are prohibited. Exponents greater than 162 (i.e., positive 35) are
discouraged, except for specifying a peak rate of infinity. Infinity
is represented with an exponent of all ones (255), and a sign bit and
mantissa of all zeros.
Ash, et al. Experimental PAGE 7
RFC 5976 Y.1541 QOSM October 2010
The QSPEC parameter behavior for the TMOD extended parameter follows
that defined in Section 3.3.1 of [RFC 5975]. The new parameter (and
all traffic-related parameters) are specified independently from the
Y.1541 class parameter.
3.2. Restoration Priority Parameter
Restoration priority is the urgency with which a service requires
successful restoration under failure conditions. Restoration
priority is achieved by provisioning sufficient backup capacity, as
necessary, and allowing relative priority for access to available
bandwidth when there is contention for restoration bandwidth.
Restoration priority is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|E|N|r| 16 |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rest. Priority| TTR | EOR | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Restoration Priority Parameter
This parameter has three fields and a reserved area, as defined
below.
Restoration Priority Field (8-bit unsigned integer): 3 priority
values are listed here in the order of lowest priority to highest
priority:
0 - best effort
1 - normal
2 - high
These priority values are described in [Y.2172], where best-effort
priority is the same as Priority level 3, normal priority is
Priority level 2, and high priority is Priority level 1. There
are several ways to elaborate on restoration priority, and the two
current parameters are described below.
Time-to-Restore (TTR) Field (4-bit unsigned integer): Total amount
of time to restore traffic streams belonging to a given
restoration class impacted by the failure. This time period
depends on the technology deployed for restoration. A fast
recovery period of < 200 ms is based on current experience with
Ash, et al. Experimental PAGE 8
RFC 5976 Y.1541 QOSM October 2010
Synchronous Optical Network (SONET) rings and a slower recovery
period of 2 seconds is suggested in order to enable a voice call
to recover without being dropped. Accordingly, TTR restoration
suggested ranges are:
0 - Unspecified Time-to-Restore
1 - Best Time-to-Restore: <= 200 ms
2 - Normal Time-to-Restore <= 2 s
Extent of Restoration (EOR) Field (4-bit unsigned integer):
Percentage of traffic belonging to the restoration class that can
be restored. This percentage depends on the amount of spare
capacity engineered. All high-priority restoration traffic, for
example, may be "guaranteed" at 100% by the service provider.
Other classes may offer lesser chances for successful restoration.
The restoration extent for these lower priority classes depend on
SLAs developed between the service provider and the customer.
EOR values are assigned as follows:
0 - unspecified EOR
1 - high priority restored at 100%;
medium priority restored at 100%
2 - high priority restored at 100%;
medium priority restored at 80%
3 - high priority restored >= 80%;
medium priority restored >= 80%
4 - high priority restored >= 80%;
medium priority restored >= 60%
5 - high priority restored >= 60%;
medium priority restored >= 60%
Reserved: These 2 octets are reserved. The Reserved bits MAY be
designated for other uses in the future. Senders conforming to
this version of the Y.1541 QOSM SHALL set the Reserved bits to
zero. Receivers conforming to this version of the Y.1541 QOSM
SHALL ignore the Reserved bits.
Ash, et al. Experimental PAGE 9
RFC 5976 Y.1541 QOSM October 2010
4. Y.1541-QOSM Considerations and Processing Example
In this section, we illustrate the operation of the Y.1541 QOSM, and
show how current QoS-NSLP and QSPEC functionality is used. No new
processing capabilities are required to enable the Y.1541 QOSM
(excluding the two OPTIONAL new parameters specified in Section 3).
4.1. Deployment Considerations
[TRQ-QoS-SIG] emphasizes the deployment of Y.1541 QNEs at the borders
of supporting domains. There may be domain configurations where
interior QNEs are desirable, and the example below addresses this
possibility.
4.2. Applicable QSPEC Procedures
All procedures defined in Section 5.3 of [RFC 5975] are applicable to
this QOSM.
4.3. QNE Processing Rules
Section 7 of [TRQ-QoS-SIG] describes the information processing in
Y.1541 QNEs.
Section 8 of [Y.1541] defines the accumulation rules for individual
performance parameters (e.g., delay, jitter).
When a QoS NSIS initiator (QNI) specifies the Y.1541 QoS Class
number, <Y.1541 QoS Class>, it is a sufficient specification of
objectives for the <Path Latency>, <Path Jitter>, and <Path BER>
parameters. As described in Section 2, some Y.1541 Classes do not
set objectives for all the performance parameters above. For
example, Classes 2, 3, and 4 do not specify an objective for <Path
Jitter> (referred to as IP Packet Delay Variation). In the case that
the QoS Class leaves a parameter unspecified, then that parameter
need not be included in the accumulation processing.
4.4. Processing Example
As described in the example given in Section 3.4 of [RFC 5975] and as
illustrated in Figure 3, the QoS NSIS initiator (QNI) initiates an
end-to-end, interdomain QoS NSLP RESERVE message containing the
Initiator QSPEC. In the case of the Y.1541 QOSM, the Initiator QSPEC
specifies the <Y.1541 QOS Class>, <TMOD>, <TMOD Extension>,
<Admission Priority>, <Restoration Priority>, and perhaps other QSPEC
parameters for the flow. As described in Section 3, the TMOD
Ash, et al. Experimental PAGE 10
RFC 5976 Y.1541 QOSM October 2010
extension parameter contains the OPTIONAL Y.1541-QOSM-specific terms;
restoration priority is also an OPTIONAL Y.1541-QOSM-specific
parameter.
As Figure 3 below shows, the RESERVE message may cross multiple
domains supporting different QOSMs. In this illustration, the
Initiator QSPEC arrives in a QoS NSLP RESERVE message at the ingress
node of the local-QOSM domain. As described in [RFC 5974] and
[RFC 5975], at the ingress edge node of the local-QOSM domain, the
end-to-end, interdomain QoS-NSLP message may trigger the generation
of a Local QSPEC, and the Initiator QSPEC is encapsulated within the
messages signaled through the local domain. The Local QSPEC is used
for QoS processing in the local-QOSM domain, and the Initiator QSPEC
is used for QoS processing outside the local domain. As specified in
[RFC 5975], if any QNE cannot meet the requirements designated by the
Initiator QSPEC to support an optional QSPEC parameter (i.e., with
the M bit set to zero for the parameter), the QNE sets the N flag
(not supported flag) for the parameter to one. For example, if the
QNE cannot support the accumulation of end-to-end delay with the
<Path Latency> parameter, where the M flag for the <Path Latency>
parameter is set to zero denoting <Path Latency> as an optional
parameter, the QNE sets the N flag (not supported flag) for the <Path
Latency> parameter to one.
Also, the Y.1541-QOSM requires negotiation of the <Y.1541 QoS Class>
across domains. This negotiation can be done with the use of the
existing procedures already defined in [RFC 5974]. For example, the
QNI sets <Desired QoS>, <Minimum QoS>, and <Available QoS> objects to
include <Y.1541 QoS Class>, which specifies objectives for the <Path
Latency>, <Path Jitter>, and <Path BER> parameters. In the case that
the QoS Class leaves a parameter unspecified, then that parameter
need not be included in the accumulation processing. The QNE/domain
SHOULD set the Y.1541 class and cumulative parameters, e.g., <Path
Latency>, that can be achieved in the <QoS Available> object (but not
less than specified in <Minimum QoS>). This could include, for
example, setting the <Y.1541 QoS Class> to a lower class than
specified in <QoS Desired> (but not lower than specified in <Minimum
QoS>). If the <Available QoS> fails to satisfy one or more of the
<Minimum QoS> objectives, the QNE/domain notifies the QNI and the
reservation is aborted. Otherwise, the QoS NSIS Receiver (QNR)
notifies the QNI of the <QoS Available> for the reservation.
When the available <Y.1541 QoS Class> must be reduced from the
desired <Y.1541 QoS Class> (say, because the delay objective has been
exceeded), then there is an incentive to respond with an available
value for delay in the <Path Latency> parameter. If the available
<Path Latency> is 150 ms (still useful for many applications) and the
desired QoS is Class 0 (with its 100 ms objective), then the response
Ash, et al. Experimental PAGE 11
RFC 5976 Y.1541 QOSM October 2010
would be that Class 0 cannot be achieved, and Class 1 is available
(with its 400 ms objective). In addition, this QOSM allows the
response to include an available <Path Latency> = 150 ms, making
acceptance of the available <Y.1541 QoS Class> more likely. There
are many long paths where the propagation delay alone exceeds the
Y.1541 Class 0 objective, so this feature adds flexibility to commit
to exceed the Class 1 objective when possible.
This example illustrates Y.1541-QOSM negotiation of <Y.1541 QoS
Class> and cumulative parameter values that can be achieved end-to-
end. The example illustrates how the QNI can use the cumulative
values collected in <QoS Available> to decide if a lower <Y.1541 QoS
Class> than specified in <QoS Desired> is acceptable.
|------| |------| |------| |------|
| e2e |<->| e2e |<------------------------->| e2e |<->| e2e |
| QOSM | | QOSM | | QOSM | | QOSM |
| | |------| |-------| |-------| |------| | |
| NSLP | | NSLP |<->| NSLP |<->| NSLP |<->| NSLP | | NSLP |
|Y.1541| |local | |local | |local | |local | |Y.1541|
| QOSM | | QOSM | | QOSM | | QOSM | | QOSM | | QOSM |
|------| |------| |-------| |-------| |------| |------|
-----------------------------------------------------------------
|------| |------| |-------| |-------| |------| |------|
| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |
|------| |------| |-------| |-------| |------| |------|
QNI QNE QNE QNE QNE QNR
(End) (Ingress Edge) (Interior) (Interior) (Egress Edge) (End)
Figure 3: Example of Y.1541-QOSM Operation
4.5. Bit-Level QSPEC Example
This is an example where the QOS Desired specification contains the
TMOD-1 parameters and TMOD extended parameters defined in this
specification, as well as the Y.1541 Class parameter. The QOS
Available specification utilizes the Latency, Jitter, and Loss
parameters to enable accumulation of these parameters for easy
comparison with the objectives desired for the Y.1541 Class.
This example assumes that all the parameters MUST be supported by the
QNEs, so all M-flags have been set to 1.
Ash, et al. Experimental PAGE 12
RFC 5976 Y.1541 QOSM October 2010
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vers.|QType=I|QSPEC Proc.=0/1|0|R|R|R| Length = 23 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E|r|r|r| Type = 0 (QoS Des.) |r|r|r|r| Length = 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|0|r| ID = 1 <TMOD-1> |r|r|r|r| Length = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TMOD Rate-1 [r] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TMOD Size-1 [b] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Data Rate-1 [p] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Policed Unit-1 [m] (32-bit unsigned integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size [MPS] (32-bit unsigned integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 15 |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Bucket Size [Bp] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 14 |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Y.1541 QoS Cls.| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E|r|r|r| Type = 1 (QoS Avail) |r|r|r|r| Length = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 3 |r|r|r|r| 1 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Path Latency (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 4 |r|r|r|r| 4 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Path Jitter STAT1(variance) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Jitter STAT2(99.9%-ile) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Jitter STAT3(minimum Latency) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Jitter STAT4(Reserved) (32-bit integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 5 |r|r|r|r| 1 |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| Path Packet Loss Ratio (32-bit floating point) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|r| 14 |r|r|r|r| 1 |
Ash, et al. Experimental PAGE 13
RFC 5976 Y.1541 QOSM October 2010
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Y.1541 QoS Cls.| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: An Example QSPEC (Initiator)
where 32-bit floating point numbers are as specified in [IEEE754].
4.6. Preemption Behavior
The default QNI behavior of tearing down a preempted reservation is
followed in the Y.1541 QOSM. The restoration priority parameter
described above does not rely on preemption.
5. IANA Considerations
This section defines additional codepoint assignments in the QSPEC
Parameter ID registry and establishes one new registry for the
Restoration Priority Parameter (and assigns initial values), in
accordance with BCP 26 [RFC 5226]. It also defines the procedural
requirements to be followed by IANA in allocating new codepoints for
the new registry.
5.1. Assignment of QSPEC Parameter IDs
This document specifies the following QSPEC parameters, which have
been assigned in the QSPEC Parameter ID registry created in
[RFC 5975]:
<TMOD Extension> parameter (Section 3.1, ID=15)
<Restoration Priority> parameter (Section 3.2, ID=16)
5.2. Restoration Priority Parameter Registry
The Registry for Restoration Priority contains assignments for 3
fields in the 4-octet word and a Reserved section of the word.
This specification creates the following registry with the structure
as defined below.
5.2.1. Restoration Priority Field
The Restoration Priority Field is 8 bits in length.
The following values are allocated by this specification:
Ash, et al. Experimental PAGE 14
RFC 5976 Y.1541 QOSM October 2010
0-2: assigned as specified in Section 3.2:
0: best-effort priority
1: normal priority
2: high priority
Further values are as follows:
3-255: Unassigned
The registration procedure is Specification Required.
5.2.2. Time to Restore Field
The Time to Restore Field is 4 bits in length.
The following values are allocated by this specification:
0-2: assigned as specified in Section 3.2:
0 - Unspecified Time-to-Restore
1 - Best Time-to-Restore: <= 200 ms
2 - Normal Time-to-Restore <= 2 s
Further values are as follows:
3-15: Unassigned
The registration procedure is Specification Required.
5.2.3. Extent of Restoration Field
The Extent of Restoration (EOR) Field is 4 bits in length.
The following values are allocated by this specification:
0-5: assigned as specified in Section 3.2:
0 - unspecified EOR
1 - high priority restored at 100%;
medium priority restored at 100%
Ash, et al. Experimental PAGE 15
RFC 5976 Y.1541 QOSM October 2010
2 - high priority restored at 100%;
medium priority restored at 80%
3 - high priority restored >= 80%;
medium priority restored >= 80%
4 - high priority restored >= 80%;
medium priority restored >= 60%
5 - high priority restored >= 60%;
medium priority restored >= 60%
Further values are as follows:
6-15: Unassigned
The registration procedure is Specification Required.
6. Security Considerations
The security considerations of [RFC 5974] and [RFC 5975] apply to this
document.
The restoration priority parameter raises possibilities for theft-of-
service attacks because users could claim an emergency priority for
their flows without real need, thereby effectively preventing serious
emergency calls from getting through. Several options exist for
countering such attacks, for example:
- only some user groups (e.g., the police) are authorized to set the
emergency priority bit
- any user is authorized to employ the emergency priority bit for
particular destination addresses (e.g., police or fire
departments)
There are no other known security considerations based on this
document.
7. Acknowledgements
The authors thank Attila Bader, Cornelia Kappler, Sven Van den Bosch,
and Hannes Tschofenig for helpful comments and discussion.
Ash, et al. Experimental PAGE 16
RFC 5976 Y.1541 QOSM October 2010
8. References
8.1. Normative References
[IEEE754] ANSI/IEEE, "ANSI/IEEE 754-1985, IEEE Standard for
Binary Floating-Point Arithmetic", 1985.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 5974] Manner, J., Karagiannis, G., and A. McDonald, "NSIS
Signaling Layer Protocol (NSLP) for Quality-of-Service
Signaling", RFC 5974, October 2010.
[RFC 5975] Ash, G., Bader, A., Kappler, C., and D. Oran, "QSPEC
Template for the Quality-of-Service NSIS Signaling
Layer Protocol (NSLP)", RFC 5975, October 2010.
[Y.1221] ITU-T Recommendation Y.1221, "Traffic control and
congestion control in IP based networks", March 2002.
[Y.1540] ITU-T Recommendation Y.1540, "Internet protocol data
communication service - IP packet transfer and
availability performance parameters", December 2007.
[Y.1541] ITU-T Recommendation Y.1541, "Network Performance
Objectives for IP-Based Services", February 2006.
[Y.2172] ITU-T Recommendation Y.2172, "Service restoration
priority levels in Next Generation Networks", June
2007.
8.2. Informative References
[COMPOSITION] Morton, A. and E. Stephan, "Spatial Composition of
Metrics", Work in Progress, July 2010.
[E.361] ITU-T Recommendation E.361, "QoS Routing Support for
Interworking of QoS Service Classes Across Routing
Technologies", May 2003.
[RFC 2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC 2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
Ash, et al. Experimental PAGE 17
RFC 5976 Y.1541 QOSM October 2010
[RFC 2474] 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.
[RFC 2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang,
Z., and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, December 1998.
[RFC 2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
"Assured Forwarding PHB Group", RFC 2597, June 1999.
[RFC 3246] 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.
[RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26, RFC
5226, May 2008.
[RFC 5835] Morton, A. and S. Van den Berghe, "Framework for
Metric Composition", RFC 5835, April 2010.
[TRQ-QoS-SIG] ITU-T Supplement 51 to the Q-Series, "Signaling
Requirements for IP-QoS", January 2004.
Authors' Addresses
Gerald Ash
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
EMail: gash5107@yahoo.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
EMail: acmorton@att.com
URI: http://home.comcast.net/~acmacm/
Ash, et al. Experimental PAGE 18
RFC 5976 Y.1541 QOSM October 2010
Martin Dolly
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
EMail: mdolly@att.com
Percy Tarapore
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
EMail: tarapore@att.com
Chuck Dvorak
AT&T Labs
180 Park Ave Bldg 2
Florham Park, NJ 07932
USA
Phone: + 1 973-236-6700
EMail: cdvorak@att.com
Yacine El Mghazli
Alcatel-Lucent
Route de Nozay
Marcoussis cedex 91460
France
Phone: +33 1 69 63 41 87
EMail: yacine.el_mghazli@alcatel.fr
Ash, et al. Experimental PAGE 19
Y.1541-QOSM: Model for Networks Using Y.1541 Quality-of-Service Classes
RFC TOTAL SIZE: 42215 bytes
PUBLICATION DATE: Wednesday, October 6th, 2010
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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