1、 International Telecommunication Union ITU-T H.248.56TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2007) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: Packages for virtual private network support ITU-T Reco
2、mmendation H.248.56 ITU-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 pro
3、cedures H.240H.259 Coding 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
4、 services H.360H.369 Supplementary 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 applic
5、ations and services H.520H.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
6、 TRIPLE-PLAY MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. H.248.56 (08/2007) i ITU-T Recommendation H.248.56 Gateway control protocol: Packages for virtual private network support Summary ITU
7、-T Recommendation H.248.56 defines H.248 packages for virtual private network (VPN) support and focuses on Ethernet-based virtual local area networks, representing a network-based layer 2 VPN type. Source ITU-T Recommendation H.248.56 was approved on 29 August 2007 by ITU-T Study Group 16 (2005-2008
8、) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.248.56 (08/2007) FOREWORD The International Telecommunication Union (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.
9、 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), which meets every four years, establishes the topics for
10、 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 ITU-Ts purview, the necessary standards are prepared o
11、n 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 Recommendation is voluntary. However, the Recommendation may cont
12、ain 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 “must“ and the negative equivalents are used to express
13、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 may involve the use of a claimed Intellectual Property
14、 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 this Recommendation, ITU had not received notice of int
15、ellectual 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 database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All r
16、ights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. H.248.56 (08/2007) iii CONTENTS Page 1 Scope 1 1.1 General . 1 1.2 NB layer 2 VPN 2 1.3 NB layer 3 VPN 2 2 References. 2 3 Definitions 3 3.1 Terms defined e
17、lsewhere 3 3.2 Terms defined in this Recommendation. 3 4 Abbreviations and acronyms 3 5 Conventions 4 6 VLAN package for Ethernet VLANs . 4 6.1 Properties 4 6.2 Events . 5 6.3 Signals 5 6.4 Statistics 5 6.5 Error Codes. 5 6.6 Procedures 5 Bibliography. 7 ITU-T Rec. H.248.56 (08/2007) 1 ITU-T Recomme
18、ndation H.248.56 Gateway control protocol: Packages for virtual private network support 1 Scope 1.1 General H.248 media gateways (MG) may be located at the boundary of virtual private networks (VPNs). At this connection point, H.248 ephemeral terminations would be involved in VPN services. In order
19、to bound the scope from a H.248 point of view, the separation in client/server VPNs is detailed in ITU-T Y.1314, ITU-T Y.1311: Client/server VPNs have a two-layer hierarchy in which a VPN server layer network is used to support one or more VPN client layer networks. ITU-T Y.1311 describes client/ser
20、ver VPNs in terms of VPN service types and VPN transport types, where the term VPN service type refers to the VPN client layer and the term VPN transport type refers to the VPN server layer. The different VPN service (client) and transport (server) types are classified in ITU-T Y.1311 as described b
21、elow in Table 1. Table 1 Y.1311 service types Service type Description Layer 1 Provides a physical layer service between customer sites belonging to the same VPN. Connections can be based on physical ports, optical wavelengths, SDH/SONET VCs, frequency channels, or timeslots. Layer 2 Provides a data
22、 link layer service between customer nodes belonging to the VPN. Forwarding of user data packets is based on information in the packets data link layer headers (e.g., DLCI, ATM VCI/VPI, or MAC addresses). Layer 3 Provides a network layer service between customer nodes belonging to the VPN. Forwardin
23、g of user data packets based on information in the layer 3 header (e.g., IPv4 or IPv6 destination address). In scope of H.248.56 are network-based VPNs (NB VPN) only, and only virtual transport networks because the H.248 MG is only involved in the network transport infrastructure. The types of VPNs
24、could be further limited to layer 2 and layer 3 VPNs (L2VPN, L3VPN) only. This is because the bearer connection endpoint behind H.248 ephemeral terminations is basically a bearer technology from layer 2/3. VPN support for H.248 physical terminations is in principle possible with H.248 (see, e.g., IT
25、U-T Rec. H.248.21), but out of scope of this Recommendation because e.g., there is not any explicit VPN-ID on bearer level. The edge of a VPN could be further distributed in customer edge (CE) and provider edge (PE) VPN network elements, see clause 5.2.1 of ITU-T Y.1311 (or ITU-T G.8011.2/Y.1307.2 f
26、or Ethernet-based VPNs). The H.248 MG may provide a “customer“ edge VPN function, but also a collapsed CE/PE VPN edge function. 2 ITU-T Rec. H.248.56 (08/2007) 1.2 NB layer 2 VPN 1.2.1 Ethernet VLAN This Recommendation supports Ethernet VLANs as NB layer 2 VPN type by the H.248 vlan package (see cla
27、use 6). Clause 6.3 of ITU-T Y.1314 provides an overview about Ethernet VLANs: IEEE 802.1Q defines the operation of virtual LAN (VLAN) bridges that permit the definition, operation and administration of virtual LAN topologies within a bridged LAN infrastructure. VLANs allow end-stations (here H.248 M
28、Gs) on multiple physical LAN segments to communicate as if they were connected to the same LAN segment. End users (here H.248 MGs) and hubs/switches can be moved to different VLANs by changing the VLAN configuration on the port/interface on the 802.1Q-compliant switching device that the end-station
29、or hub/switch connects to. Traffic separation for frames belonging to different VLANs across a shared infrastructure is achieved by inserting a tag with a VLAN identifier (VID) into each frame. A VID must be assigned for each VLAN (1 to 4096) and must be globally unique within the same physical infr
30、astructure. One of the drawbacks to this approach is that customers also use VLANs within their own network, which introduces VID allocation and limitation issues. To solve this problem, a second IEEE 802.1Q-tag can be appended to customer IEEE 802.1Q-tagged packets that enter the providers network
31、(Q-in-Q as defined in IEEE 802.1ad). This separates the providers VLAN space from the customers VLAN space and allows customers to use whatever VIDs they want. NOTE Another option is to use a MAC-in-MAC approach (as defined in IEEE 802.1ah), in which a provider appends a second Ethernet header to th
32、e customers packet. However, this option creates a client/server VPN rather than a peer-level VPN because the customers frame is encapsulated inside a provider frame. The tags property of the H.248 vlan package is a VPN-ID (called the VLAN identifier, VID; see clause 6.1.1) and is used to assign an
33、H.248 stream of an Ethernet-based ephemeral termination to a particular VLAN. 1.2.1.1 Ethernet VLAN with traffic management extension IEEE 802.1p is an extension of IEEE 802.1Q. IEEE 802.1Q specifies a tag that appends to an Ethernet MAC frame. The VLAN tag has two parts: The VLAN ID (12 bits) and p
34、rioritization (3 bits). The prioritization field was not defined and used in the 802.1Q VLAN standard. IEEE 802.1p defines this prioritization field. IEEE 802.1p establishes eight levels of priority. The H.248 vlan package addresses IEEE 802.1p and IEEE 802.1Q by dedicated properties, see clause 6.1
35、.1 and 6.1.2 respectively. 1.2.2 Other NB layer 2 VPNs For further study. 1.3 NB layer 3 VPN Support for NB L3 VPNs, e.g., like NB IP VPNs, is for further study. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute
36、 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 the Recomme
37、ndations and other references listed below. A list of the ITU-T Rec. H.248.56 (08/2007) 3 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 G.8011.2 I
38、TU-T Recommendation G.8011.2/Y.1307.2 (2005), Ethernet virtual private line service. ITU-T H.248.1 ITU-T Recommendation H.248.1 (2005), Gateway control protocol: Version 3. ITU-T Y.1311 ITU-T Recommendation Y.1311 (2002), Network-based VPNs Generic architecture and service requirements. ITU-T Y.1314
39、 ITU-T Recommendation Y.1314 (2005), Virtual private network functional decomposition. IEEE 802.1ad IEEE 802.1ad (2005), IEEE Standard for local and metropolitan area networks Virtual Bridged Local Area Networks Amendment 4: Provider Bridges. IEEE 802.1D IEEE 802.1D (2004), IEEE Standard for local a
40、nd metropolitan area networks Media Access Control (MAC) Bridges. IEEE 802.1p IEEE 802.1p (2004), LAN Layer 2 QoS/CoS Protocol For Traffic Prioritization (see clause “Introduction“ in IEEE 802.1Q on “Relationship between IEEE 802.1D and IEEE 802.1Q“). IEEE 802.1Q IEEE 802.1Q (2005), IEEE Standard fo
41、r local and metropolitan area networks Virtual bridged local area networks. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere. 3.1.1 NB layer 2 VPN: See clause 3.3 of ITU-T Y.1311. 3.1.2 NB layer 3 VPN: See clause 3.4 of ITU-T Y.1311. 3.1.3 NB I
42、P VPN: See clause 3.4.1 of ITU-T Y.1311. 3.1.4 virtual services network (VSN): See clause 3.5 of ITU-T Y.1311. 3.1.5 virtual transport network: See clause 3.6 of ITU-T Y.1311. 3.2 Terms defined in this Recommendation None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviat
43、ions and acronyms: CE Customer Edge EPL Ethernet Private Line ETH Ethernet MAC layer network LAN Local Area Network MAC Medium Access Control MG Media Gateway 4 ITU-T Rec. H.248.56 (08/2007) MGC Media Gateway Controller NB Network Based PE Provider Edge PPVPN Provider Provisioned Virtual Private Net
44、work TCI Tag Control Information VID VLAN Identifier VLAN Virtual Local Area Network VPN Virtual Private Network VPN-ID VPN Identifier VSN Virtual Service Network VTN Virtual Transport Network 5 Conventions None. 6 VLAN package for Ethernet VLANs Package name: VLAN package PackageID: vlan (0x0091) v
45、alue allocated by IANA. Description: This package enables up to two layer 2 VLAN tags (for “virtual LAN“ support in IEEE 802.1Q and, additionally, support of “provider VLAN“ based on “Q in Q“ VLAN stacking in IEEE 802.1ad) to be passed to the MG. It also allows a layer 2 priority value (according to
46、 IEEE 802.1p) to be applied to the given Ethernet-based ephemeral termination. Version: 1 Extends: None 6.1 Properties 6.1.1 VLAN tags Property name: VLAN tags PropertyID: tags (0x0001) Description: This property corresponds to one or two VLAN tags. Where two VLAN tags are included, tag stacking (.1
47、q in .1q) shall be implemented. The first tag in the Ethernet frame shall be set to the value of the first tag in the list. Each property list entry relates to a 12-bit VLAN identifier (VID). The VID is part of the IEEE 802.1Q tag control information (TCI) field. Type: Sublist of integer Possible va
48、lues: 0 to 4096 Default: None (see also clause 6.6.5). Defined in: Local control Characteristics: Read/write ITU-T Rec. H.248.56 (08/2007) 5 6.1.2 Ethernet priority Property name: Ethernet priority PropertyID: pri (0x0002) Description: This property identifies the priority of each VLAN tag. The firs
49、t priority corresponds to the first VLAN tag, the second priority corresponds to the second VLAN tag. Type: Sublist of integer Possible values: 0 to 7 Default: None (see also clause 6.6.5). Defined in: Local control Characteristics: Read/write 6.2 Events None. 6.3 Signals None. 6.4 Statistics None. 6.5 Error Codes None. 6.6 Procedures This package can be applied to ephemeral terminations where the MG is using an Ethernet encapsulation on the interface (compliant to I
