One document matched: draft-ietf-nsis-y1541-qosm-04.txt
Differences from draft-ietf-nsis-y1541-qosm-03.txt
IETF Internet Draft NSIS Working Group J. Ash
Internet Draft M. Dolly
Intended Status: Informational C. Dvorak
<draft-ietf-nsis-y1541-qosm-04.txt> A. Morton
Expiration Date: October 2007 P. Tarapore
AT&T
Y. El Mghazli
Alcatel-Lucent
April 2007
Y.1541-QOSM -- Y.1541 QoS Model
for Networks Using Y.1541 QoS Classes
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This draft describes a QoS-NSLP QoS model (QOSM) based on ITU-T
Recommendation Y.1541 QoS signaling requirements. Y.1541 specifies 8
standard QoS classes, and the Y.1541-QOSM extensions include
additional QSPEC parameters and QOSM processing guidelines.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Summary of ITU-T Recommendations Y.1541 & Signaling
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Y.1541 QoS Classes . . . . . . . . . . . . . . . . . . . . 3
2.2. Y.1541-QOSM Processing Requirements . . . . . . . . . . . 4
3. Additional QSPEC Parameters for Y.1541 QOSM . . . . . . . . . 5
3.1 Traffic Model (TMOD) Extension Parameter . . . . . . . . . 5
3.2 Restoration Priority Parameter . . . . . . . . . . . . . . 5
4. Y.1541-QOSM Processing Example . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . . 9
9. Informative References . . . . . . . . . . . . . . . . . . . . 9
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 9
Conventions Used in This Document
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].
1. Introduction
This draft describes a QoS model (QOSM) for NSIS QoS signaling
layer protocol (QoS-NSLP) application based on ITU-T Recommendation
Y.1541 QoS signaling requirements. Y.1541 currently specifies 8
standard QoS classes, and the Y.1541-QOSM extensions include
additional QSPEC parameters and QOSM processing guidelines. The
extensions are based on standardization work in the ITU-T on QoS
signaling requirements [Y.1541, TRQ-QoS-SIG, E.361].
[QoS-SIG] defines message types and control information for the
QoS-NSLP 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 [QSPEC] 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 [RFC2205,
RFC2210]. The QSPEC object contains the QoS parameters defined by
the QOSM. A QOSM provides a specific set of parameters to be carried
in the QSPEC. At each QoS NSIS element (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.
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2. Summary of ITU-T Recommendations Y.1541 & 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).
[TRQ-QoS-SIG] specifies the requirements for achieving 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.
2.1 Y.1541 QoS 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. Classes 0 and 1, which generally correspond
to the DiffServ EF PHB, support interactive real-time applications.
Classes 2, 3, and 4, which generally correspond to the DiffServ AFxy
PHB Group, support non-interactive applications. Class 5, which
generally corresponds to the DiffServ best-effort PHB, has all the
QoS parameters unspecified. Classes 6 and 7 provide support for
extremely loss-sensitive user applications, such as high quality
digital television, TDM circuit emulation, and high capacity
transfers using TCP. These classes serve as a basis for agreements
between end-users and service providers, and between service
providers. They support a wide range of traffic 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.1451 QoS class are summarized here:
Class 0: Real-time, highly interactive applications, sensitive to
jitter. Mean delay upper bound is 100 ms, delay variation is less
than 50 ms, and loss ratio is less than 10^-3. Application examples
include VoIP, Video Teleconference.
Class 1: Real-time, interactive applications, sensitive to jitter.
Mean delay upper bound is 400 ms, delay variation is less than 50 ms,
and loss ratio is less than 10^-3. Application examples include VoIP,
video teleconference.
Class 2: Highly interactive transaction data. Mean delay upper bound
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is 100 ms, delay variation is unspecified, and loss ratio is less
Than 10^-3. Application examples include signaling.
Class 3: Interactive transaction data. Mean delay upper bound is 400
ms, delay variation is unspecified, and loss ratio is less than
10^-3. Application examples include signaling.
Class 4: Low Loss Only applications. Mean delay upper bound is 1s,
delay variation is unspecified, and loss ratio is less than 10^-3.
Application examples include short transactions, bulk data, 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:
Mean delay <= 100 ms, delay variation <= 50 ms, loss ratio <= 10^-5.
Applications that are highly sensitive to loss, such as television
transport, high-capacity TCP transfers, and TDM circuit emulation.
Class 7:
Mean delay <= 400 ms, delay variation <= 50 ms, loss ratio <= 10^-5.
Applications that are highly sensitive to loss, such as television
transport, high-capacity TCP transfers, and TDM circuit emulation.
These classes enable 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.
2.2 Y.1541-QOSM Processing Requirements
[TRQ-QoS-SIG] provides the requirements for signaling information
regarding 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, a network needs to provide specific user plane
functionality at UNI and NNI interfaces. Dynamic network
provisioning at a UNI and/or NNI node allows the ability to
dynamically request a traffic contract for an IP flow 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.
It MUST be possible to derive the following service level parameters
as part of the process of requesting service:
a. Y.1541 QoS class
b. rate (r)
c. peak rate (p)
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d. bucket size (b)
e. peak bucket size (Bp)
f. maximum packet size (M)
g. DiffServ PHB class [RFC2475]
h. admission priority
i. restoration priority
All parameters except Bp, M, and restoration priority have already
been specified in [QSPEC]. These additional parameters are 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 already supported by [QoS-SIG] and
the functions are illustrated in Section 4.
3. Additional QSPEC Parameters for Y.1541 QOSM
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 unsigned integer.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peak Bucket Size [Bp] (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Packet Size [M] (32-bit unsigned integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
When the Bp term is represented as an IEEE floating point value, 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 zeroes. The maximum
packet size (M) is an unsigned integer.
3.2 Restoration Priority Parameter
Restoration priority is the urgency with which a service requires
successful restoration under failure conditions. Restoration
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rest. Priority| (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Restoration Priority:
3 priority values are listed here in the order of lowest priority to
highest priority:
0 - best effort
1 - normal
2 - high
Each restoration priority class has two parameters:
a. Time-to-Restore: 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
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, candidate restoration objectives are:
High Restoration Priority: Time-to-Restore <= 200 ms
Normal Restoration Priority: Time-to-Restore <= 2 s.
Best Effort Restoration Priority: Time-to-Restore = Unspecified
b. Extent of Restoration: 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 priority 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 SLA agreements developed between the
service provider and the customer.
4. Y.1541-QOSM 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 or parameters are required to enable the
Y.1541 QOSM.
As described in the example given in [QSPEC] (Section 4.4) and as
illustrated in Figure 1, the QoS NSIS initiator (QNI) initiates an
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end-to-end, inter-domain 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
extension parameter contains the optional, Y.1541-QOSM-specific
parameters Bp and M; restoration priority is also an optional,
Y.1541-QOSM-specific parameter.
As illustrated in Figure 1, the RESERVE message may cross multiple
domains supporting different QOSMs. In this illustration, the
initiator QSPEC arrives in an QoS NSLP RESERVE message at the ingress
node of the local-QOSM domain. As described in [QoS-SIG] and
[QSPEC], at the ingress edge node of the local-QOSM domain, the
end-to-end, inter-domain QoS-NSLP message may trigger the generation
of a local QSPEC, and the initiator QSPEC 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
[QSPEC], if any QNE cannot meet the requirements designated by the
initiator QSPEC to support an optional QSPEC parameter, with the M
bit set to zero for the parameter, for example, it cannot support the
accumulation of end-to-end delay with the <Path Latency> 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 [QoS-SIG]. For example, the
QNI sets <Desired QoS>, <Minimum QoS>, <Available QoS> objects to
include <Y.1541 QoS Class>, <Path Latency>, <Path Jitter>, <Path BER>
parameters. 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 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 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
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<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 achieve
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 1 Example of Y.1541-QOSM Operation
5. Security Considerations
The security considerations of [QoS-SIG] and [QSPEC] apply to this
Document. There are no new security considerations based on this
document.
6. IANA Considerations
This section defines the registries and initial codepoint assignments
for the QSPEC template, in accordance with BCP 26 RFC 2434 [RFC2434].
It also defines the procedural requirements to be followed by IANA in
allocating new codepoints.
This document specifies the following QSPEC parameters to be assigned
within the QSPEC Parameter ID registry created in [QSPEC]:
<TMOD Extension> parameter (Section 3.1)
<Restoration Priority> parameter (Section 3.2)
This specification creates the following registry with the structure
as defined below:
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Restoration Priority Parameter (8 bits):
The following values are allocated by this specification:
0-2: assigned as specified in Section 3.2:
Restoration Priority 0: best-effort priority
1: normal priority
2: high priority
The allocation policies for further values are as follows:
3-63: Standards Action
64-255: Reserved
7. Acknowledgements
The authors thank Attila Bader, Cornelia Kappler, and Sven Van
den Bosch for helpful comments and discussion.
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[QoS-SIG] Van den Bosch, S., et. al., "NSLP for Quality-of-Service
Signaling," work in progress.
[QSPEC], Ash, J., et. al., "QoS-NSLP QSPEC Template," work in
progress.
[TRQ-QoS-SIG] ITU-T Recommendation, "Signaling Requirements for
IP-QoS," January 2004.
[Y.1541] ITU-T Recommendation Y.1541, "Network Performance Objectives
for IP-Based Services," February 2006.
9. Informative References
[E.361] ITU-T Recommendation, "QoS Routing Support for Interworking
of QoS Service Classes Across Routing Technologies," May 2003.
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services," RFC 2210, September 1997.
[RFC2434] Narten, T., Alvestrand, H., "Guidelines for Writing an IANA
Considerations Section in RFCs," RFC 2434, October 1998.
[RFC2475] Blake, S., et. al., "An Architecture for Differentiated
Services", RFC 2475, December 1998.
10. Authors' Addresses
Jerry Ash
AT&T
Room MT D5-2A01
200 Laurel Avenue
Middletown, NJ 07748, USA
Phone: +1-(732)-420-4578
Email: gash@att.com
Martin Dolly
AT&T
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Room E3-3A14
200 S. Laurel Avenue
Middletown, NJ 07748
Phone: + 1 732 420-4574
E-mail: mdolly@att.com
Chuck Dvorak
AT&T
Room 2A37
180 Park Avenue, Building 2
Florham Park, NJ 07932
Phone: + 1 973-236-6700
E-mail: cdvorak@att.com
Yacine El Mghazli
Alcatel-Lucent
Route de Nozay
91460 Marcoussis cedex - FRANCE
Phone: +33 1 69 63 41 87
Email: yacine.el_mghazli@alcatel.fr
Al Morton
AT&T
Room D3-3C06
200 S. Laurel Avenue
Middletown, NJ 07748
Phone: + 1 732 420-1571
E-mail: acmorton@att.com
Percy Tarapore
AT&T
Room D1-33
200 S. Laurel Avenue
Middletown, NJ 07748
Phone: + 1 732 420-4172
E-mail: tarapore@.att.com
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