1、 International Telecommunication Union ITU-T H.248.52TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2008) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: QoS support packages Recommendation ITU-T H.248.52 ITU-
2、T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220H.229 Systems aspects H.230H.239 Communication procedures H.240H.259 Codin
3、g of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for audiovisual and multimedia services H.360H.369 Sup
4、plementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services H.510H.519 Mobile multimedia collaboration applications and services H.52
5、0H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559Mobile multimedia collaboration inter-working procedures H.560H.569 BROADBAND AND TRIPLE-PLAY MULTIMEDIA
6、SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 For further details, please refer to the list of ITU-T Recommendations.
7、Rec. ITU-T H.248.52 (06/2008) i Recommendation ITU-T H.248.52 Gateway control protocol: QoS support packages Summary Recommendation ITU-T H.248.52 provides H.248 packages for different quality of service (QoS) support mechanisms. The QoS class package may be used in various areas with relations to Q
8、oS, e.g., media gateway level admission control functions. The Differentiated Services package is specifically designed to support QoS marking for IPv4- or IPv6-based H.248 streams/terminations, but limited to the 6-bit DiffServ field within the IP header. The General IP Header QoS Octet package all
9、ows QoS marking and modification of the entire 8-bit field, related to QoS protocol control information elements in IPv4 and IPv6 packet headers. Amendment 1 (03/2009), which is integrated in this edition, defines a new version of the Differentiated Services package, which clarifies the procedures f
10、or copying DSCP values from ingress packets to egress ones. Source Recommendation ITU-T H.248.52 was approved on 13 June 2008 by ITU-T Study Group 16 (2005-2008) under the Recommendation ITU-T A.8 procedure. This edition includes the Amendment approved on 16 March 2009 by ITU-T Study Group 16 (2009-
11、2012) under the Recommendation ITU-T A-8 procedure. ii Rec. ITU-T H.248.52 (06/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Stan
12、dardization 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 telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), w
13、hich 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 procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within
14、 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 telecommunication administration and a recognized operating agency. Compliance with this Recommenda
15、tion 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 mandatory provisions are met. The words “shall“ or some other obligatory language such as “m
16、ust“ 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 draws attention to the possibility that the practice or implementation of this Recommendation
17、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 or others outside of the Recommendation development process. As of the date of approval of t
18、his Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent da
19、tabase at http:/www.itu.int/ITU-T/ipr/. ITU 2009 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 H.248.52 (06/2008) iii CONTENTS Page 1 Scope 1 1.1 Typical application of the QoS class package 1 1.2
20、Typical application of the Differentiated Services and General IP Header QoS Octet packages 2 1.3 Avoidance of interaction between the Differentiated Services and General IP Header QoS Octet packages. 2 2 References. 2 3 Terms and definitions . 3 3.1 Terms defined elsewhere 3 3.2 Terms defined in th
21、is Recommendation. 3 4 Abbreviations and acronyms 3 5 Conventions 4 6 QoS class package 4 6.1 Properties 4 6.2 Events . 4 6.3 Signals 5 6.4 Statistics 5 6.5 Error Codes. 5 6.6 Procedures 5 7 Differentiated Services package . 6 7.1 Properties 7 7.2 Events . 7 7.3 Signals 7 7.4 Statistics 8 7.5 Error
22、Codes. 8 7.6 Procedures 8 8 General IP Header QoS Octet package. 12 8.1 Properties 13 8.2 Events . 14 8.3 Signals 14 8.4 Statistics 14 8.5 Error codes 14 8.6 Procedures 14 Appendix I QoS class codepoint mapping on Y.1541 QoS classes 15 Appendix II Relation of QoS class package with differentiated se
23、rvices package. 16 Appendix III Relation of QoS class package with H.248 context attribute “priority“ 17 iv Rec. ITU-T H.248.52 (06/2008) Page Appendix IV Some examples for QoS marking with the H.248 differentiated services package . 18 IV.1 Introduction 18 IV.2 ToS marking . 18 IV.3 DSCP Marking .
24、18 IV.4 Remarks 20 Bibliography. 21 Rec. ITU-T H.248.52 (06/2008) 1 Recommendation ITU-T H.248.52 Gateway control protocol: QoS support packages 1 Scope This Recommendation provides H.248 packages for different quality of service (QoS) support mechanisms. The QoS class package (clause 6) defines a s
25、ingle property for signalling a QoS class codepoint. Such a codepoint may be correlated with a set of network performance parameters. Such parameters may be used in the area of transport resource management or admission control. The Differentiated Services package (clause 7) defines a property to co
26、ntrol the 6-bit differentiated services (DS) field of the IP header, as defined in IETF RFC 2474. The media gateway controller (MGC) can set the quality of service (QoS) for egress media flows without having to provision the media gateway (MG) with a default differentiated service code point (DSCP)
27、value. Thus both packages have a slightly different scope as described in the clauses below (see also Appendix II). The General IP Header QoS Octet package (clause 8) provides an extended capability, in comparison to the Differentiated Services package, in order to address the entire 8-bit field, an
28、d enable modification of individual bits. 1.1 Typical application of the QoS class package This package is only relevant for ephemeral terminations, i.e., packet-switched bearer technologies. Any packet-based bearer connection traverses a set of packet nodes in the network. Even within an MG, a bear
29、er may traverse a number of queuing points. To set up a bearer, generally resources must be reserved at each transport path/interface and/or MG-internally (see Note 1). The availability check, selection and allocation of resources are related to admission control (AC) functions (see Note 2), e.g., t
30、here could be admission control functions in an MG on the level of contexts (CoAC), terminations (TeAC) or even streams (StAC). NOTE 1 This may depend on how the network capacity and/or MG capacity is engineered, e.g., the MG external network interfaces may be “over-provisioned“, operated in a “best
31、 effort“ manner, or strict deterministic resource allocation schemes, etc. Similar resource management models may be applied internally to the MG. NOTE 2 The concept is very similar to the connection admission control (CAC) concept defined for B-ISDN/ATM b-ITU-T I.371. Any admission control function
32、 is motivated by QoS support and determines the admissibility of a new bearer (i.e., H.248 context, termination and/or stream; see Note 3) by checking the availability of various resources. Network performance parameters may be part of such an AC function and thus could be described by this package.
33、 NOTE 3 This may depend in particular on the H.248 connection model (e.g., IP-to-IP context), or single/multiple H.248 streams per termination, etc. It has to be noted that the area of admission control is just one possible application of the QoS class package. The diversity of potential application
34、s (see Note 4) is much broader due to the definition of the qos package property. The particular application should be defined in a profile specification. NOTE 4 Further applications are, e.g., support of path-coupled QoS signalling, or support of pushing/pulling QoS-specific policies, or even suppo
35、rt of QoS marking. 2 Rec. ITU-T H.248.52 (06/2008) 1.2 Typical application of the Differentiated Services and General IP Header QoS Octet packages “Packet marking“ (also known as “QoS marking“) is a QoS building block for support of quality of service in packet networks (see clause 8.4 of ITU-T Y.12
36、91). This function involves assigning a value to a designated IP header field in IP networks. QoS marking in IP domains is the primary scope of the ds and gih packages and includes marking of: IPv4 Type-of-Service (ToS) field (b-IETF RFC 1349); IPv4 Explicit Congestion Notification (ECN) field (b-IE
37、TF RFC 3168); IPv4 ToS together with ECN; IPv4 Differentiated Services (DS) field (IETF RFC 2474); IPv6 Traffic Class field (b-IETF RFC 2460); or IPv6 Differentiated Services (DS) field (IETF RFC 2474). The ds package is predestined for DS codepoint (DSCP) marking, but is also applicable for non-DS
38、IP domains. The function of QoS marking is illustrated by examples in Appendix IV. The ds package is furthermore applicable for controlling DS conditioning functions and per-hop behaviour (PHB). 1.3 Avoidance of interaction between the Differentiated Services and General IP Header QoS Octet packages
39、 The two properties ds/dscp and gih/iqo overlap at a common 6-bit field in the IP header. Any parallel application of both properties to the same H.248 stream may thus lead to contradictory semantics. It is therefore recommended to use only one property per stream, and not both. Where both will resu
40、lt in a conflict, error code #473 (“Conflicting property values“) is returned. Likewise, parallel application of the ds/tb and the gih/tm properties to the same H.248 stream may lead to contradictory semantics. It is also recommended to use only one of these two properties per stream, and not both.
41、Where both will result in a conflict, error code #473 “Conflicting property values“ is returned. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, t
42、he 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 listed below. A list of the current
43、ly 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 H.248.1 Recommendation ITU-T H.248.1 (2005), Gateway control protocol: Version 3. ITU-T H.248.15 Recommenda
44、tion ITU-T H.248.15 (2002), Gateway control protocol: SDP H.248 package attribute. ITU-T Y.1291 Recommendation ITU-T Y.1291 (2004), An architectural framework for support of Quality of Service in packet networks. IETF RFC 2474 IETF RFC 2474 (1998), Definition of the Differentiated Services Field (DS
45、 field) in the IPv4 and IPv6 Headers. Rec. ITU-T H.248.52 (06/2008) 3 3 Terms and definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 QoS class: QoS refers to a set of (network) performance parameters. Such a se
46、t could, for instance, constitute the traffic contract between the subscriber equipment and the network. Examples of such performance parameters include: packet loss ratio, packet transfer delay, and packet delay variation tolerance. The parameters are used to define distinct QoS classes. 4 Abbrevia
47、tions and acronyms This Recommendation uses the following abbreviations and acronyms: AC Admission Control ATM Asynchronous Transfer Mode BCAC Bearer Connection Admission Control BCP Bearer Control Protocol B-ISDN Broadband Integrated Services Digital Network CAC Connection Admission Control CES Cir
48、cuit Emulation Service CoAC Context Admission Control CoS Class of Service CU Currently Unused (DiffServ) DiffServ Differentiated Services DS Differentiated Services DSCP Differentiated Services Code Point ECN Explicit Congestion Notification ER Edge Router IP Internet Protocol IPDV Internet Protoco
49、l packet Delay Variation IPER Internet Protocol packet Error Ratio IPLR Internet Protocol packet Loss Ratio IPRR Internet Protocol packet Reordering Ratio IPTD Internet Protocol packet Transfer Delay MG Media Gateway MGC Media Gateway Controller MLPP Multi-Level Precedence and Preemption NGN Next Generation Network 4 Rec. ITU-T H.248.52 (06/2008) PHB Per-Hop Behaviour QoS Quality of Service RACF Resource and Admission Control Functions SDO Standards Development Organization SDP Session Description Protocol StAC Str
