1、 International Telecommunication Union ITU-T Y.2171TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (09/2006) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Next Generation Networks Quality of Service and performance Admission control priority leve
2、ls in Next Generation Networks ITU-T Recommendation Y.2171 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 Network aspects Y.
3、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, access, networ
4、k 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 Frameworks and fu
5、nctional 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.2399 Network m
6、anagement 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. ITU-T Rec. Y.2171 (09/2006) i ITU-T Recommendation Y.2171 Admission control priority levels
7、in Next Generation Networks Summary This Recommendation proposes three levels for admission control priority for services seeking entry into Next Generation Networks. The admission control priority indicator is intended as a guidance in the development of appropriate signalling protocol extensions,
8、and in the development of the necessary priority enabling mechanisms. Source ITU-T Recommendation Y.2171 was approved on 13 September 2006 by ITU-T Study Group 13 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. Y.2171 (09/2006) FOREWORD The International Telecommunication Uni
9、on (ITU) is the United Nations specialized agency in the field of telecommunications. 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 s
10、tandardizing telecommunications 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 i
11、s covered by the procedure 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
12、 indicate both a telecommunication 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 ach
13、ieved when all of these 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. INTELLECTUA
14、L PROPERTY RIGHTS ITU draws 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
15、asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautio
16、ned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2006 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of IT
17、U. ITU-T Rec. Y.2171 (09/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations 2 5 Introduction and rationale. 2 6 Recommendation for admission control priority levels . 3 7 Implementation example of priority levels with RACF . 3 BIBLIOGRAPHY 4 ITU-T Rec. Y.2171 (09/2006)
18、 1 ITU-T Recommendation Y.2171 Admission control priority levels in Next Generation Networks 1 Scope According to ITU-T Rec. Y.1271 Y.1271, enhanced priority treatment is an essential requirement for the assured capabilities needed for emergency telecommunications. A critical component of enhanced p
19、riority treatment is admission control for telecommunications services seeking entry into a network particularly during emergency conditions when network resources may be depleted. Admission control in the NGN can be enabled by: 1) development of admission control priority levels based on the critic
20、ality of services seeking entry in NGNs; 2) development of necessary extensions in signalling protocols that can indicate the desired service priority levels at NGN interfaces; 3) development of admission control mechanisms that can recognize the signalled priority levels and undertake necessary act
21、ion. The scope of this Recommendation is limited to the development of priority levels for admission control. The purpose is to provide guidance for the subsequent development of the necessary signalling protocol extensions and the priority enabling mechanisms. Administrations may require operators
22、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, constitute provisions of this Recommend
23、ation. 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 the Recommendations and other references
24、 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. Y.1271 ITU-T Recommendation Y.1271 (2004), Framework(s) on network requiremen
25、ts and capabilities to support emergency telecommunications over evolving circuit-switched and packet-switched networks. Y.1541 ITU-T Recommendation Y.1541 (2006), Network performance objectives for IP-based services. Y.2111 ITU-T Recommendation Y.2111 (2006), Resource and admission control function
26、s in Next Generation Networks. 3 Definitions This Recommendation defines the following terms: 3.1 admission control: A set of actions/policies taken by the network at session set-up phase in order to accept or reject a service based on requested performance and priority criteria and the availability
27、 of necessary resources. 3.2 emergency telecommunications: An umbrella term for telecommunications of an “extraordinary nature“ under abnormal and potentially adverse network conditions. 2 ITU-T Rec. Y.2171 (09/2006) 4 Abbreviations This Recommendation uses the following abbreviations: CAC Connectio
28、n Admission Control CoS Class of Service ET Emergency Telecommunications IP Internet Protocol ISP Internet Service Provider LSP Label Switched Path MPLS Multi-Protocol Label Switching MPLS-TE MPLS Traffic Engineering NSIS Next Steps in Signalling PD-FE Policy Decision Functional Element PE-FE Policy
29、 Enforcement Functional Element RACF Resource and Admission Control Function SCF Service Control Function SIP Session Initiation Protocol SLA Service Level Agreement TRC-FE Transport Resource Control Functional Element VoIP Voice over IP VPN Virtual Private Network 5 Introduction and rationale NGNs
30、are expected to be truly “converged“. That is, all forms of telecommunications services will be handled by such networks control plane traffic (e.g., routing messages), emergency telecommunications, real-time voice and video services, data services, virtual private network (VPN) services, as well as
31、 traditional “best effort“ traffic. In such an environment, it is important to assign priority levels and establish rules for capacity reservation and admission such that critical services are recognized and accepted for call/session set-up and admission (or simply carried in the case of non-session
32、 oriented traffic) over other services in case of network overloads or failures. As services can be expected to traverse multiple network domains, setting admission control priority levels is an important step in the development of the necessary signalling protocol extensions as well as the mechanis
33、ms for enabling preferential admission treatment of critical services. It is critical for an NGN to recognize and admit higher priority services into the network, particularly under failure and/or congestion conditions. This can be referred to as a traditional form of connection admission control (C
34、AC) priority classification. The need for such priority levels is most critical under emergency conditions when networks may experience loss of resources and capacity coupled with surges of communications traffic as the impacted public seeks help (in the affected areas) or information about family a
35、nd friends. Priority levels can then be utilized by CAC functions to determine whether incoming calls or sessions can be admitted depending on the criticality of the service and the availability of a potentially reduced set of network resources. Note that the priority level recommendations proposed
36、in this Recommendation strictly relate to the relative importance of telecommunications services seeking admission into networks. They do not ITU-T Rec. Y.2171 (09/2006) 3 reflect implementation specific priority definitions. Further, these recommended levels are independent from the Y.1541 Y.1541 Q
37、oS classes. 6 Recommendation for admission control priority levels Three admission control priority levels are recommended for telecommunications services seeking entry into NGN: Priority level 1: Traffic with this priority level receives the highest assurance for admission to the network. This leve
38、l is reserved for emergency telecommunications over NGN. Priority level 2: Traffic with this priority level will not receive the same assurance for admission as that given to priority level 1 traffic, but will receive higher assurance for admission than that given to priority level 3 traffic. Exampl
39、es include real-time services (VoIP, video), VPN and data services. The selection of this priority level is expected to be determined by appropriate service level agreements (SLA) between network operators and customers for the desired service. Priority level 3: Traffic with this priority level rece
40、ives the least assurance for admission to the network. Examples include “traditional“ Internet service provider (ISP) services (email, web surfing). The selection of this priority level is expected to be determined by appropriate SLA agreements between network operators and customers for the desired
41、 service. Each network operator may adopt additional priority levels. The total number of admission control priority levels may be extended in the future. The choice of priority implementation mechanisms in the transport stratum is up to the network operator. 7 Implementation example of priority lev
42、els with RACF ITU-T Rec. Y.2111 Y.2111 defines the functional architecture for the resource and admission control function (RACF) for NGN. RACF is intended to serve as the arbitrator between the service control function (SCF) and the transport function in the NGN for QoS-related transport control in
43、 access and core networks. Arbitration decisions will be based on transport subscription information, SLAs, network policy rules, service priority, and transport resource status and utilization information. RACF is required to recognize and process the CAC priority levels as follows: Policy decision
44、 functional element (PD-FE) receives the CAC priority level (along with other relevant information) of the incoming session from the SCF and passes it to the transport resource control functional element (TRC-FE) and the policy enforcement functional element (PE-FE) over the Rt and Rw reference poin
45、ts respectively. TRC-FE determines resource availability to complete the incoming session that best meets the QoS requirements. In the event of depleted resources, the TRC-FE determines the order of session set-up/admission based on the CAC priority. PE-FE may recognize the priority and QoS attribut
46、es of the incoming session and map it to a pre-designated class of service (CoS) that best meets the session requirements. The CoS depends on the underlying transport stratum mechanisms. When the RACF operates below full capacity due to component failure and/or experienced overload, it is expected t
47、o process requests for priority level 1 sessions first and throttle those for priority level 3 and priority level 2 sessions as appropriate. 4 ITU-T Rec. Y.2171 (09/2006) BIBLIOGRAPHY Y.1291 ITU-T Recommendation Y.1291 (2004), An architectural framework for support of quality of service in packet ne
48、tworks. E.361 ITU-T Recommendation E.361 (2003), QoS routing support for interworking of QoS service classes across routing technologies. E.106 ITU-T Recommendation E.106 (2003), International Emergency Preference Scheme (IEPS) for disaster relief operations. Y.2201 Draft ITU-T Recommendation Y.2201
49、, NGN release 1 requirements (http:/www.itu.int/md/T05-SG13-R-0026/en). E.107 Draft ITU-T Recommendation E.107, Emergency Telecommunications Service (ETS) and interconnection framework for national implementations of ETS (http:/www.itu.int/md/T05-SG02-060503-TD-PLEN-0009/en). Q-series-Supp51 ITU-T Q Series Supplement 51 (2004), Signalling Requirements for IP-QoS. TR 0100003 ATIS Technical Report 0100003, User Plane Priority Levels in IP Networks and Services, November 2004. T1.TR.79*Committee T1 Technical Report T1.TR.
