1、 ECMA-333 2ndEdition / December 2003 Private Integrated Services Network (PISN) - Mapping Functions for the Tunnelling of QSIG through H.323 Networks Standard ECMA-333 2ndEdition / December 2003 Private Integrated Services Network (PISN) - Mapping Functions for the Tunnelling of QSIG through H.323 N
2、etworks Ecma International Rue du Rhne 114 CH-1204 Geneva T/F: +41 22 849 6000/01 www.ecma-international.org IW Ecma-333.doc 06.01.2004 15:45 . Brief history This Standard is one of a series of Ecma standards defining mapping functions in exchanges of Private Integrated Services Networks required fo
3、r the utilization of intervening network scenarios. The series uses the ISDN concepts as developed by ITU-T (formerly CCITT) and is also within the framework of standards for open systems interconnection as defined by ISO. This particular Standard specifies mapping functions for the type of scenario
4、s where two or more PINXs are interconnected via on-demand connections using an H.323 packet network as the IVN. The Standard is based upon the practical experience of Ecma member companies and the results of their active and continuous participation in the work of ISO/IEC JTC1, ITU-T, ETSI and othe
5、r international and national standardization bodies. It represents a pragmatic and widely based consensus. The second edition is fully compatible with the first edition. It specifies one part of the procedures of the optional semi-permanent scenario in more detail The December 2003 General Assembly
6、adopted this, 2ndedition, of ECMA-333. Table of contents 1 Scope 1 2 Conformance 1 3 References 1 4 Definitions 2 4.1 External definitions 2 4.2 Other definitions 2 4.2.1 Call 2 4.2.2 Channel 2 4.2.3 Inter-PINX Connection (IPC) 2 4.2.4 Inter-PINX Link (IPL) 2 4.2.5 PINX roles 2 5 List of acronyms 3
7、6 Introduction 3 6.1 Reference configuration 3 6.2 Specific scenarios 4 6.3 Relationship with H.323 gateways 4 7 Capabilities at the Q reference point 5 8 Capabilities at the C reference point 5 9 Mapping functions 6 9.1 General requirements 6 9.2 Mapping of the DQ-channel 6 9.3 Mapping of the UQ-ch
8、annel(s) 6 9.3.1 On-demand scenario 6 9.3.2 Semi-permanent scenario 6 10 IPC control procedures 7 10.1 Protocol identification 7 10.2 Registration with gatekeeper 7 10.3 Systems without gatekeeper 7 10.4 H.323 call establishment 7 10.4.1 Call admission 7 10.4.2 Outgoing call establishment 8 - i - 10
9、.4.3 Incoming call establishment 8 10.5 Transfer of inter-PINX signalling information 8 10.6 H.323 call clearing 9 11 Scenario specific procedures 9 11.1 On-demand scenario 9 11.2 Semi-permanent scenario 9 Annex A - Implementation Conformance Statement (ICS) Proforma 13 Annex B - Examples of message
10、 sequences 21 - ii - 1 Scope This Standard specifies functions for using an H.323 packet network in order to interconnect two Private Integrated services Network eXchanges (PINXs) forming part of a Private Integrated Services Network (PISN). Interconnection is achieved by carrying the inter-PINX sig
11、nalling protocol over the H.323 call signalling channel, making use of the protocol tunnelling facilities of H.323, and inter-PINX user information (e.g., voice) over logical channels established through H.323. Each logical channel usually represents a unidirectional media stream conveyed by means o
12、f the Real-time Transport Protocol (RTP). The inter-PINX signalling protocol is assumed to be QSIG, as specified in ECMA-143, ECMA-165 and other standards. The Standard provides for an on-demand type of interconnection, where a separate H.323 call is established at the start of each PISN call and cl
13、eared down at the end of that call. A semi-permanent scenario where a single H.323 call with an indefinite lifetime carries QSIG on behalf of many PISN calls is described as an additional option. In the scenarios covered in this Standard, the PINXs participating in a call are not necessarily aware o
14、f the H.323 network providing the interconnection, and the features available are those of the QSIG network. This is different from a scenario where true interworking between QSIG and H.323 (i.e. QSIGH.323QSIG) is used to connect two PISNs or two parts of the same PISN. In this latter case all netwo
15、rks participate in a call on equal terms, and features are limited to those available in all networks and supported by the gateways. This latter scenario is outside the scope of this Standard. This Standard is applicable to PINXs that can be interconnected to form a PISN using QSIG as the inter-PINX
16、 signalling protocol. 2 Conformance In order to conform to this Standard, a PINX shall satisfy the requirements identified in the Implementation Conformance Statement (ICS) proforma in Annex A. 3 References The following standards contain provisions which, through reference in this text, constitute
17、provisions of this Standard. All standards are subject to revision, and parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. In the case of references to Ecma Standards that are aligned with
18、ISO/IEC International Standards, the number of the appropriate ISO/IEC International Standard is given in brackets after the Ecma reference. ECMA-133 Private Integrated Services Network (PISN) - Reference Configuration for PISN Exchanges (PINX) (International Standard ISO/IEC 11579-1) ECMA-143 Priva
19、te Integrated Services Network (PISN) - Circuit Mode Bearer Services - Inter-Exchange Signalling Procedures and Protocol (International Standard ISO/IEC 11572) ECMA-165 Private Integrated Services Network (PISN) - Generic Functional Protocol for the Support of Supplementary Services - Inter-Exchange
20、 Signalling Procedures and Protocol (International Standard ISO/IEC 11582) ITU-T Rec. H.225.0 Call signalling protocols and media stream packetization for packet based multimedia communications systems (2000 or later) ITU-T Rec. H.245 Control protocol for multimedia communication (2000 or later) ITU
21、-T Rec. H.323 Packet based multimedia communications systems (2000 or later) ITU-T H.323 Annex M.1 Tunnelling of signalling protocols (QSIG) in H.323 - 1 - 4 Definitions 4.1 External definitions For the purpose of this Standard the following definitions apply: Call independent signalling connection
22、(ECMA-165) C reference point (ECMA-133) Gatekeeper (ITU-T Rec. H.323) Gateway, Trunking Gateway (ITU-T Rec. H.323) Intervening network (ECMA-133) Logical channel (ITU-T Rec. H.323) Preceding PINX (ECMA-165) Private Integrated Services Network (ECMA-133) Private Integrated services Network eXchange (
23、ECMA-133) Q reference point (ECMA-133) Subsequent PINX (ECMA-165) 4.2 Other definitions 4.2.1 Call 4.2.1.1 H.323 call A call as defined in ITU-T Rec. H.323, i.e. a point-to-point communication between two H.323 endpoints. Here specifically a call in the H.323 network between two gateways. 4.2.1.2 PI
24、SN call A call as defined in ECMA-143 and ECMA-165. 4.2.1.3 Call segment A portion of a (PISN) call between two entities taking part in that call. The smallest segment is between adjacent entities, e.g. between two PINXs across one Inter-PINX link. 4.2.2 Channel A means of bi-directional transmissio
25、n of user or signalling information between two points. 4.2.2.1 DQ-Channel A channel used to convey call control information between the Q reference points of two peer PINXs. 4.2.2.2 UQ-Channel A channel used to convey user information between the Q reference points of two peer PINXs. 4.2.3 Inter-PI
26、NX Connection (IPC) A connection provided by an IVN between two C reference points used to transport inter-PINX information from the PISN control plane and/or the PISN user plane. 4.2.4 Inter-PINX Link (IPL) A link between the Q reference points of two PINXs, comprising the totality of signalling tr
27、ansfer and user information transfer means. 4.2.5 PINX roles 4.2.5.1 Initiating PINX The PINX that initiates an IPL establishment request. - 2 - 4.2.5.2 Accepting PINX The PINX that accepts an IPL establishment request. 5 List of acronyms GK Gatekeeper ICS Implementation Conformance Statement IP Int
28、ernet Protocol IPC Inter-PINX Connection IPL Inter-PINX Link IVN Intervening Network PINX Private Integrated services Network eXchange PISN Private Integrated Services Network QSIG Signalling system for the Q reference point RAS Registration, Admission and Status RTP / RTCP Real Time Protocol / Real
29、 Time Control Protocol TCP Transmission Control Protocol UDP User Datagram Protocol 6 Introduction 6.1 Reference configuration ECMA-133 defines a reference configuration for a PINX. Logically the switching and call control functions of a PINX communicate over an instance of the Q reference point wit
30、h a peer PINX. This communication is known as an Inter-PINX Link (IPL) and comprises a signalling channel, known as a DQ-channel, and one or more user information channels, each known as a UQ-channel; see Figure 1. One or more IPLs can be established between the same pair of PINXs. Switchingand Call
31、ControlfunctionsDQ-channelBQ-channelBQ-channelQ referencepointSwitchingand CallControlfunctionsInter-PINX linkPINX PINXQ referencepointFigure 1 - IPL concept There are many ways of implementing an IPL. In general, the IPL uses services of another network, known as an Intervening Network (IVN). A PIN
32、X interfaces to the IVN at the C reference point. The IVN provides connections, known as Inter-PINX Connections (IPCs) between the C reference points of the peer PINXs. Mapping functions within each PINX map the DQ-channel and the UQ-channels at the Q reference point onto one or more IPCs at the C r
33、eference point. - 3 - 6.2 Specific scenarios This Standard specifies mapping functions for use when the IVN is an H.323 packet network that is used to provide the following types of IPC: a signalling connection for carrying signalling information; and a pair of UDP streams, one stream in each direct
34、ion, for carrying user information over RTP. NOTE Other means of transporting user information can be used, e.g. T.38 fax without RTP, an ATM virtual channel, or a bi-directional TCP connection instead of UDP streams. See H.323 for more details. These cases are outside the scope of this Standard. A
35、single IPL requires a single signalling connection, for support of the DQ-channel, and one pair of UDP streams per UQ-channel. The main inter-PINX connection scenario described in this Standard is an on-demand connection scenario. This means that an IPL is established whenever a PISN call segment is
36、 to be set up between two PINXs and released when the PISN call ends. An optional semi-permanent scenario is also described, where multiple concurrent or consecutive PISN calls can use the same IPL. In both scenarios the signalling connection is established by means of an H.323 call, using the proto
37、col tunnelling facilities provided by H.225.0 and H.323 Annex M.1. The H.225.0 call signalling connection in conjunction with the tunnelling of the QSIG signalling is used to provide the DQ-channel. The pair of UDP streams used to provide an inter-PINX user connection (UQ-channel) is established as
38、H.323 logical channel(s). An IPL may have multiple UQ-channels. Figure 2 illustrates these concepts. PINX IVN (IP network usingH.323)Switchingand CallControlfunctionsDQ-channelBQ-channelBQ-channelQ referencepointQ referencepointSwitchingand CallControlfunctionsInter-PINX linkPINXMappingfunctionsC re
39、ferencepointDQ-channelBQ-channelBQ-channelMappingfunctionsC referencepointInter-PINX connectionsH225.0 callsignalling channelPair of UDP streamsPair of UDP streamsFigure 2 - H.323 as intervening network (IVN) IPCs in support of these scenarios can be established and released at any time under the co
40、ntrol of either PINX. In case of IPC failure, the H.323 network may reject a call establishment request or release an already established call. A single PINX can terminate a multiplicity of IPLs leading to the same and/or different peer PINXs. Each IPL comprises a single H.323 call. 6.3 Relationship
41、 with H.323 gateways Each PINX connected to another PINX via an H.323 network represents a trunking gateway in H.323 terms. The H.323 gateway functionality is part of the mapping functions of the PINX. No specific implementation is implied by this Standard. The gateway function may be fully integrat
42、ed or decomposed into several components (e.g. media gateway controller and media gateway), as explained in H.323. The tasks of the gateway include the handling of user data or media, e.g. packetization / de-packetization, and signalling interworking. The latter mainly enables QSIG to be tunnelled o
43、ver an H.323 call, as specified in more detail in subsequent clauses. - 4 - Figure 3 shows an example of the relationship between a PISN call and the underlying H.323 call which provides the inter-PINX link for one segment of the PISN call. H323 callPINX PINXPISN callsegmentPISN callsegmentPISN call
44、segmentPINX PINXSwitchingand CallControlfunctionsSwitchingand CallControlfunctionsH.323gatewayH.323gatewayFigure 3 - Example of the relationship between PISN call and H.323 call 7 Capabilities at the Q reference point For each instance of the Q reference point: one signalling channel (DQ) for carryi
45、ng the inter-PINX Layer 3 signalling protocol, and zero, one or more user channels (UQ) are provided. NOTE If the DQ-channel is used only to support QSIG call-independent signalling connections, no UQ-channels are required. For a UQ-channel the following bearer capability shall be provided: transfer
46、 mode: circuit mode; information transfer rate: 64 kbit/s; information transfer capability: speech or 3,1 kHz audio; user information layer 1 protocol: G.711 A or law. Other bearer capabilities may also be provided (e.g. 64 kbit/s unrestricted digital information, or transfer rates other than 64 kbi
47、t/s). For a DQ-channel the following bearer capability shall be provided: transfer mode: packet mode; information transfer rate: implementation-dependent; information transfer capability: unrestricted digital information. The functions to map DQ- and UQ-channels to an inter-PINX connection (IPC) at
48、the C reference point are described in Clause 9. 8 Capabilities at the C reference point A PINX shall support a packet network interface suitable for multimedia communication according to ITU-T recommendation H.323. The protocol stack shall conform to ITU-T recommendations H.323, H.225.0 and H.245 a
49、nd shall support protocol tunnelling according to H.323 Annex M.1. NOTE This means that the following protocols are used: H.225.0 RAS, if a gatekeeper is present, over UDP/IP; H.225.0 call control signalling, with embedded QSIG tunnel, over TCP/IP; H.245 within fastStart elements and/or embedded in H.225.0 call control or explicit over TCP/IP; RTP/RTCP over UDP/IP. The protocol tunnelling capability of the H.323 call signalling channel serves as the IPC for the DQ-channel. A pair of H.323 logical channels for media transport serves
