1、 International Telecommunication Union ITU-T Y.2121TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Next Generation Networks Quality of Service and performance Requirements for the support of
2、 flow-state-aware transport technology in NGN Recommendation ITU-T Y.2121 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Net
3、work aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture,
4、 access, network capabilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 NEXT GENERATION NETWORKS Fr
5、ameworks and functional architecture models Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y
6、.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T Y.2121 (01/2008) i Recommendation ITU-T Y.2121 Requirements for th
7、e support of flow-state-aware transport technology in NGN Summary Recommendation ITU-T Y.2121 specifies the requirements for the support of the flow-state-aware (FSA) transfer capability in a next generation network (NGN). The FSA transfer capability provides QoS controls that operate on a per-flow
8、basis, allowing flows to receive different treatment depending on signalled parameters. These parameters are requested using in-band signalling. The parameters contained in these signals are included in the “flow state“ maintained on each flow at each FSA node. Service options that may be selected i
9、nclude requested support of the highest available end-to-end (or FSA edge-to-edge) rate for data transfer. Another option is immediate transmission, wherein a flow may start or assume a new rate immediately on the understanding that the network is required to provide a guaranteed rate as soon as pos
10、sible. This is required to be provided when network resources permit. Yet another option is for a negotiated guaranteed rate. These services are targeted at access scenarios where media flows may result in temporary congestion and where best effort would not act selectively on the last few flows tha
11、t had contributed to the onset of congestion. These services may also be applied to flow aggregates, providing the possibility of highest available rate between the aggregation end-points or the option of supporting immediate aggregate rate changes that act in conjunction with per-flow controls. Sou
12、rce Recommendation ITU-T Y.2121 was approved on 25 January 2008 by ITU-T Study Group 13 (2005-2008) under the Recommendation ITU-T A.8 procedure. ii Rec. ITU-T Y.2121 (01/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommu
13、nications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommuni
14、cations on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedu
15、re laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecom
16、munication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these
17、mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU dr
18、aws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members
19、or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not repres
20、ent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T Y.2121 (01/200
21、8) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 3 5 Overview 4 6 Requirements 6 6.1 Dynamic provisioning requests from an FSA signalling edge function. 6 6.2 Network and FSA signalling edge function responses to flow-state-aware requests. 9 6.3 Signalling
22、requirements 10 6.4 Admission decision 14 6.5 General architectural requirements on the management of transport connections carrying flow-state-aware traffic and other traffic . 14 6.6 Security considerations and requirements 15 Annex A Dynamic provisioning requests from an FSA signalling edge funct
23、ion 16 A.1 Negotiations for a user-end-system without signalling capability . 16 A.2 Authorization 16 A.3 Service context . 17 Annex B Signalling requirements. 19 B.1 Second QoS structure attached. 19 B.2 Authorization information attached 19 B.3 Flow aggregation request . 19 B.4 FSA node operation
24、19 Appendix I Supplementary information on information exchanges via requests from an FSA signalling edge function and associated responses. 20 I.1 Flow identifier 20 I.2 In-band signalling negotiations 20 I.3 Preference indicator request . 21 I.4 Authentication 21 I.5 Priority of packet discard, in
25、cluding service context use of preference indicator values. 23 I.6 Congestion notification 23 Appendix II Supplementary information to signalling requirements . 24 II.1 Recognition of QoS signalling packets 24 II.2 Form of QoS information . 24 II.3 Performance requirements for requests and responses
26、. 24 II.4 Release of resources no longer required. 25 II.5 QoS signalling parameters 25 iv Rec. ITU-T Y.2121 (01/2008) Page II.6 Service contexts 25 II.7 Preference indicator 26 II.8 Delay priority 26 II.9 Burst tolerance 26 II.10 Flow identifier fields 26 Appendix III Illustrative QoS support for d
27、ifferent preference indicator values 28 III.1 Preference resolution for maximum rate (MRS) flows 28 III.2 Preference resolution for available rate (ARS) flows. 28 Appendix IV Supplementary information relating to requirements on the management of transport connections carrying flow-state-aware traff
28、ic and other traffic 29 IV.1 General architectural assumptions 29 IV.2 General issues on the management of access links shared by FSA and non-FSA traffic. 30 IV.3 Combined flow-level and aggregate flow-level FSA controls . 33 Appendix V Example implementation principles associated with FSA nodes. 38
29、 Appendix VI Out-of-band signalling with a central admission entity 40 Bibliography. 42 Rec. ITU-T Y.2121 (01/2008) 1 Recommendation ITU-T Y.2121 Requirements for the support of flow-state-aware transport technology in NGN 1 Scope This Recommendation provides flow-state-aware requirements in support
30、 of per-flow service options providing for edge-to-edge QoS and transport resource control (including resource reservation and admission control) in next generation networks (NGNs). The pertinent protocol specifications and measurement requirements will be described in separate Recommendations. Note
31、 that network management functionality is outside the scope of this Recommendation. Also out of scope are any edge functions at network domain boundaries needed for interworking QoS support between FSA and non-FSA networks. Similarly, out of scope are any edge functions at network domain boundaries
32、needed for interworking between two FSA networks, where one uses in-band signalling exclusively for all FSA service support, and the other uses out-of-band signalling for resource reservation and clear-down coupled with in-band signalling to establish the agreed flow state in the involved FSA nodes.
33、 Administrations may require operators and service providers to take into account national regulatory and national policy requirements in implementing this Recommendation. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text,
34、constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of t
35、he Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Y.1221 Recommendation ITU-T Y.12
36、21 (2002), Traffic control and congestion control in IP-based networks. ITU-T Y.2012 Recommendation ITU-T Y.2012 (2006), Functional requirements and architecture of the NGN release 1. ITU-T Y.2111 Recommendation ITU-T Y.2111 (2006), Resource and admission control functions in Next Generation Network
37、s. 3 Definitions This Recommendation defines the following terms: 3.1 aggregation end-point: An end-point within the network which attaches or deletes the common flow aggregate identifiers to ensure commencement/cessation of common routing and QoS treatment of packets. This end-point also initiates/
38、terminates in-band signalling to control flow state information retained for treatment of the flow aggregate. 3.2 available rate service (ARS): The name of one of the flow-state-aware (FSA) transport services. ARS is primarily for applications that can flexibly adapt to the current available capacit
39、y and can quickly adjust their sending rate as the available capacity changes. 3.3 flow: A unidirectional sequence of packets with the property that, along any given network link, a flow identifier has the same value for every packet. 2 Rec. ITU-T Y.2121 (01/2008) 3.4 flow aggregate: A hierarchical
40、flow construct that is associated with a group of flows. The carried flows may extend beyond the flow aggregate. Except for the end nodes, flow aggregate forwarders in general do not know that they are carrying flows within the flow aggregate. All packets belonging to a given flow aggregate are comm
41、only routed between aggregation end-points. 3.5 flow admission control: The determination, for authorized requests, of whether or not to accept a given flow. 3.6 flow identifier: A vector comprising the values of a number of elements taken from the IP, TCP/UDP header fields, encapsulation header, an
42、d label fields attached to a packet. The flow identifier for a flow within a single FSA network is unique. Clause II.10 describes some examples of suitable identifiers purely for information and as an aid to understanding. 3.7 flow state: A set of values stored per flow identifier at each flow-state
43、-aware node. This set of values determines controls applied on a per-flow basis, dealing with forwarding rate, delay and congestion recovery. 3.8 flow-state-aware node: A network node that is capable of maintaining flow state and applying per-flow QoS controls, based on recognizing flow identifier a
44、nd associated signals. 3.9 flow-state-aware signalling edge function: A function that provides the origin and/or termination of the flow-state-aware end-to-end signalling path, and participates in requests and responses on behalf of a user-end-system (UES) application or management action. It may be
45、 located, for example, in the UES or at a network edge node where it serves as the signalling end-point of multiple users and associated applications. Alternatively, it may be located at an aggregation end-point where it supports the signalling requirements of flow aggregates. Out of scope is a netw
46、ork domain edge function required for interworking QoS support between FSA and non-FSA networks. Similarly, out of scope is a network domain edge function that may be required when two FSA networks interwork, where one uses in-band signalling exclusively for all FSA service support, and the other us
47、es out-of-band signalling for resource reservation and clear-down coupled with in-band signalling to establish the agreed flow state in the involved FSA nodes. 3.10 guaranteed rate service (GRS): The name of one of the flow-state-aware (FSA) transport services. GRS is for applications that require g
48、uaranteed bandwidth for the duration of the flow. 3.11 in-band signalling: A mode of signalling where the signalling messages are within the flow of the data packets, and follow a path that is tied to the data packets. Signalling messages are routed only through nodes that are in the data path. 3.12
49、 maximum rate service (MRS): The name of one of the flow-state-aware (FSA) transport services. MRS is for applications that want packet loss characteristics to be sufficient for streamed services as soon as possible but are unwilling to wait or be rejected by network admission control if network resource for this target QoS is not available immediately. 3.13 out-of-band signalling: A mode of signalling where the signalling messages are not in the same flow of the data packets, and may follow a different path to the data packets and are rout
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