1、 Standard ECMA-336 International June 2002 Standardizing Information and Communication Systems Private Integrated Services Network (PISN) - Mapping Functions for the Tunnelling of QSIG through IP Networks Phone: +41 22 849.60.00 - Fax: +41 22 849.60.01 - URL: http:/www.ecma.ch - Internet: helpdeskec
2、ma.ch . Standard ECMA-336 International June 2002 Standardizing Information and Communication Systems Private Integrated Services Network (PISN) - Mapping Functions for the Tunnelling of QSIG through IP Networks (Mapping/IP-QSIG) Phone: +41 22 849.60.00 - Fax: +41 22 849.60.01 - URL: http:/www.ecma.
3、ch - Internet: helpdeskecma.ch IW Ecma-336.doc 01-07-02 16,29 . Brief History This Standard is one of a series of ECMA standards defining mapping functions in exchanges of Private Integrated Services Networks required for the utilization of intervening network scenarios. The series uses the ISDN con
4、cepts as developed by ITU-T (formerly CCITT) and is also within the framework of standards for open systems interconnection as defined by ISO/IEC. It has been produced under ETSI work item DTS/ECMA-00234. This Standard is based upon the practical experience of ECMA member companies and the results o
5、f their active and continuous participation in the work of ISO/IEC JTC1, ITU-T, ETSI and other international and national standardization bodies. It represents a pragmatic and widely based consensus. This Standard has been adopted by the ECMA General Assembly of June 2002. . - i - Table of contents
6、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 Calling PINX 2 4.2.2 Called PINX 2 4.2.3 Channel 2 4.2.4 Resource Control Information 2 4.2.5 Inter-PINX Connection (IPC) 2 4.2.6 QPKT 2 5 List of acronyms 2 6 Introduction 3 6.1 Referen
7、ce configuration 3 6.2 Specific scenarios 3 7 Capabilities at the Q reference point 4 8 Capabilities at the C reference point 4 8.1 TCP connection 4 8.2 UDP streams 5 9 Mapping functions 5 9.1 Mapping the DQ-channel 5 9.2 Mapping a UQ-channel 5 10 IPC control functions 5 10.1 Procedure for UQ-channe
8、l establishment 6 10.2 Procedure for UQ-channel clearing 6 Annex A - Implementation Conformance Statement (ICS) Proforma 7 Annex B - Message syntax for Resource Control Information 13 1 Scope This Standard specifies functions for using a packet network that uses the Internet Protocol (IP) as its net
9、work layer protocol and UDP and TCP as its transport layer protocols, 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 signalling protocol directly over the T
10、ransmission Control Protocol (TCP) and inter-PINX user information (e.g., voice) over the Real-time Transport Protocol (RTP), RTP being carried over the User Datagram Protocol (UDP). The inter-PINX signalling protocol is assumed to be QSIG, as specified in ECMA-143, ECMA-165 and other standards. The
11、 Standard provides for two types of interconnection: - on-demand, where a separate TCP connection for QSIG is established at the start of each call and cleared down at the end of that call; and - semi-permanent, where a single TCP connection with an indefinite lifetime carries QSIG on behalf of many
12、 single calls. This Standard is applicable to PINXs that can be interconnected to form a PISN using QSIG as the inter-PINX signalling protocol. 2 Conformance In order to conform to this Standard, a PINX shall satisfy the requirements identified in the Implementation Conformance Statement (ICS) profo
13、rma in annex A. 3 References The following standards contain provisions which, through reference in this text, constitute provision 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
14、most recent editions of the standards indicated below. ECMA-133 Private Integrated Services Network (PISN) - Reference Configuration for PISN Exchanges (PINX) (International Standard ISO/IEC 11579-1) ECMA-142 Private Integrated Services Network (PISN) - Circuit Mode 64kbit/s Bearer Services - Servic
15、e Description, Functional Capabilities and Information Flows (International Standard ISO/IEC 11574) ECMA-143 Private Integrated Services Network (PISN) - Circuit Mode Bearer Services - Inter-Exchange Signalling Procedures and Protocol (International Standard ISO/IEC 11572) ECMA-165 Private Integrate
16、d Services Network (PISN) - Generic Functional Protocol for the Support of Supplementary Services - Inter-Exchange Signalling Procedures and Protocol (International Standard ISO/IEC 11582) ITU-T Rec. I.112 Vocabulary of terms for ISDNs (1993) ITU-T Rec. I.210 Principles of telecommunication services
17、 supported by an ISDN and the means to describe them (1993) IETF RFC 760 Internet Protocol IETF RFC 761 Transmission Control Protocol IETF RFC 768 User Datagram Protocol IETF RFC 1889 RTP: a transport protocol for real-time applications IETF RFC 2126 ISO Transport Service on top of the TCP (ITOT) -
18、2 - 4 Definitions For the purposes of this Standard the following definitions apply. 4.1 External definitions This Standard uses the following terms defined in other documents: - - - - - IVN (ECMA-133) PINX (ECMA-133) PISN (ECMA-133) Service (ITU-T Rec. I.112) Signalling (ITU-T Rec. I.112) 4.2 Other
19、 definitions 4.2.1 Calling PINX In the context of a call or call-independent signalling connection across an IPL, the PINX that transmits the QSIG SETUP message. 4.2.2 Called PINX In the context of a call or call-independent signalling connection across an IPL, the PINX that receives the QSIG SETUP
20、message. 4.2.3 Channel A means of bi-directional transmission of user or signalling information between two points. 4.2.3.1 DQ-Channel A channel used to convey call control information between the Q reference points of two peer PINXs. 4.2.3.2 UQ-Channel A channel used to convey user information betw
21、een the Q reference points of two peer PINXs. 4.2.4 Resource Control Information Information exchanged between peer PINXs for the purpose of establishing UDP streams 4.2.5 Inter-PINX Connection (IPC) A connection provided by an IVN between two C reference points used to transport inter-PINX informat
22、ion from the PISN control plane and/or the PISN user plane. 4.2.6 QPKT A packet format defined within this Standard for conveying QSIG message and RCI (Resource Control Information). 5 List of acronyms IP Internet Protocol IPC Inter-PINX connection IPL Inter-PINX Link IVN InterVening Network PINX Pr
23、ivate Integrated services Network eXchange PISN Private Integrated Services Network QSIG Signalling information flows at the Q reference point RCI Resource Control Information RTCP Realtime Transport Control Protocol RTP Realtime Transport Protocol - 3 - TCP Transmission Control Protocol UDP User Da
24、tagram 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 with a peer PINX. This communication is known as an Inter-PINX Link (IP
25、L) 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 CallControlfunctionsDQ-channelUQ-channelUQ-channelQ referencepointSwitch
26、ingand 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 PINX interfaces to the IVN at the C reference point. The IVN provides con
27、nections, 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 reference point. 6.2 Specific scenarios This Standard specifies mapping
28、 functions for use when the IVN is an IP-based network that is used to provide the following types of IPC: - a TCP connection for carrying signalling information and Resource Control Information; and - a pair of UDP streams, one stream in each direction, for carrying user information over RTP. A sin
29、gle IPL requires a single TCP connection, for support of the DQ-channel, and one pair of UDP streams per UQ-channel. In addition to carrying the QSIG protocol, the TCP connection is also required to carry resource control information for establishing the UDP streams. This Standard supports two types
30、 of interconnection between peer PINXs: - On-demand, where a single TCP connection for QSIG and a pair of UDP streams for user information are established at the start of each call and cleared down at the end of that call; - Semi-permanent, where a single TCP connection with an indefinite lifetime c
31、arries QSIG on behalf of many calls. In the semi-permanent case, the TCP connection can support zero, one or more than one call at the same time. A pair of UDP streams for user information is established at the start of each call and cleared down at the end of that call. Figure 2 illustrates these c
32、oncepts. - 4 - PINX IVN (IP network)Switchingand CallControlfunctionsDQ-channelUQ-channelUQ-channelQ referencepointQ referencepointSwitchingand CallControlfunctionsInter-PINX linkPINXMappingfunctionsC referencepointDQ-channelUQ-channelUQ-channelMappingfunctionsC referencepointInter-PINX connectionsT
33、CP connectionPair of UDP streamsPair of UDP streamsFigure 2 IPC concept (Semi-permanent) 7 Capabilities at the Q reference point For each instance of the Q reference point: one signalling channel (DQ) for carrying the inter-PINX Layer 3 signalling protocol, and zero, one or more user channels (UQ) s
34、hall be provided. NOTE In the special case of an on-demand interconnection used only for a call independent signalling connection, no UQ-channels are provided. For a UQ-channel the following bearer capability shall be provided: transfer mode: circuit mode; information transfer rate: 64 kbit/s; infor
35、mation transfer capability: speech or 3,1 kHz audio; user information layer 1 protocol: G.711 A or law. Other bearer capabilities are outside the scope of this Standard. For a DQ-channel the following bearer capability shall be provided: transfer mode: packet mode; information transfer rate: impleme
36、ntation-dependent; information transfer capability: unrestricted digital information. The functions to map DQ- and UQ-channels to an inter-PINX connection (IPC) at the C reference point are described in clause 9. 8 Capabilities at the C reference point The PINX mapping functions shall meet the follo
37、wing requirements. 8.1 TCP connection A PINX shall support a packet network interface suitable for communication according to IETF RFC 761. The protocol stack used in this Standard is described as figure 3 below. QSIG RCI QPKT TPKT TCP IP Figure 3 Protocol stack for Mapping/IP-QSIG - 5 - The RCI pro
38、vides information required to establish the media path(s). A TPKT is a packet format as defined in IETF RFC 2126. It is used to delimit individual messages (PDUs) within the TCP stream, which itself provides a continuous stream of octets without explicit boundaries. A TPKT consists of a one octet ve
39、rsion number field, followed by a one octet reserved field, followed by a two octet length field, followed by the actual data. The version number field shall contain the value “3”, the reserved field shall contain the value “0”. The length field shall contain the length of the entire packet includin
40、g the version number, the reserved and the length fields as a 16-bit big-endian word. A QPKT is a packet format as defined in figure 4 below. A QPKT consists of a two octet length field, followed by a single QSIG message, followed by RCI. The first octet of the QSIG message shall be the octet immedi
41、ately following the QPKT length field, the last octet shall be the octet immediately preceding the RCI. The length field indicates the length of the QSIG message and therefore indicates the start of the RCI. RCI QSIG message len.Figure 4 QPKT structure of Mapping/IP-QSIG NOTE In most circumstances,
42、the RCI field is omitted. The DQ-channel shall be mapped to the well-known TCP port (4029) or to a dynamically assigned port. RCI shall be in accordance with annex B. 8.2 UDP streams The UQ-channel shall be mapped to a received UDP stream and a transmitted UDP stream, each carrying RTP packets. The
43、received UDP stream shall be received at a local IP address and port as indicated in transmitted RCI and the transmitted UDP stream shall be transmitted to a remote IP address and port as indicated in received RCI. NOTE If required, PINXs can use RTCP as defined in IETF RFC 1889 to monitor the quali
44、ty of RTP carried over UDP streams. 9 Mapping functions 9.1 Mapping the DQ-channel For transmission, a complete QSIG message and RCI shall be embedded in a QPKT packet within a TPKT packet as defined in clause 8.1. The segmentation and reassembly procedures of ECMA-143 shall not be used. The RCI imp
45、licitly refers to the call to which the QSIG message relates. It shall be included in the first forward and first backward message of each call, and shall not be included in subsequent messages. In addition, RCI shall not be included with call-independent messages. 9.2 Mapping a UQ-channel Each UQ-c
46、hannel shall be mapped to a pair of unidirectional UDP streams with suitable transport capabilities defined by the RCI. The mapping function is responsible for proper packetization, de-packetization, transcoding etc. of media data. 10 IPC control functions To establish the IPC for the DQ-channel, th
47、e PINX initiating the TCP connection needs to know the IP address of the other PINX. The means for determining the IP address is outside the scope of this Standard. For the on-demand scenario, the calling PINX shall establish a TCP connection for the DQ-channel following the procedure specified in I
48、ETF RFC 761 whenever a call or call-independent signalling connection is to be established and shall clear down the TCP connection when the call or call-independent signalling connection has been cleared. - 6 - For the semi-permanent scenario, when a call or call independent signalling connection is
49、 to be established, if a DQ-channel (TCP connection) exists between the peer-PINXs, the calling PINX shall use that DQ-channel. If no DQ-channel exists between the peer PINXs, the calling PINX shall establish a TCP connection for the DQ-channel following the procedure specified in IETF RFC 761. It is an implementation matter when to clear the TCP connection, except that it shall not to be cleared while still being used for a call or call independent signalling connection. For either scenario, UQ-channel establishment and clear down shall be in accordance with
