rfc2885.txt

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RFC 2885                    Megaco Protocol                  August 2000


        E.12.1 Properties..........................................153
        E.12.2 Events..............................................153
        E.12.3 Signals.............................................153
        E.12.4 Statistics..........................................153
        E.12.5 Procedures..........................................154
   E.13 TDM Circuit Package........................................154
        E.13.1 Properties..........................................155
        E.13.2 Events..............................................155
        E.13.3 Signals.............................................155
        E.13.4 Statistics..........................................156
        E.13.5 Procedures..........................................156
   APPENDIX A EXAMPLE CALL FLOWS (INFORMATIVE).....................157
   A.1 Residential Gateway to Residential Gateway Call.............157
        A.1.1 Programming Residential GW Analog Line Terminations for
        Idle Behavior..............................................157
        A.1.2 Collecting Originator Digits and Initiating Termination
        ...........................................................159
   Authors' Addresses..............................................168
   Full Copyright Statement........................................170

1. SCOPE

   This document defines the protocol used between elements of a
   physically decomposed multimedia gateway.  There are no functional
   differences from a system view between a decomposed gateway, with
   distributed sub-components potentially on more than one physical
   device, and a monolithic gateway such as described in H.246. This
   recommendation does not define how gateways, multipoint control units
   or integrated voice response units (IVRs) work.  Instead it creates a
   general framework that is suitable for these applications.  Packet
   network interfaces may include IP, ATM or possibly others.  The
   interfaces will support a variety of SCN signalling systems,
   including tone signalling, ISDN, ISUP, QSIG, and GSM.  National
   variants of these signalling systems will be supported where
   applicable.

   The protocol definition in this document is common text with ITU-T
   Recommendation H.248.  It meets the requirements documented in RFC
   2805.

2. REFERENCES

2.1 Normative references

   ITU-T Recommendation H.225.0 (1998): "Call Signalling Protocols and
   Media Stream Packetization for Packet Based Multimedia Communications
   Systems".




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   ITU-T Recommendation H.235 (02/98): "Security and encryption for
   H-Series (H.323 and other H.245-based) multimedia terminals".

   ITU-T Recommendation H.245 (1998): "Control Protocol for Multimedia
   Communication".

   ITU-T Recommendation H.323 (1998): "Packet Based Multimedia
   Communication Systems".

   ITU-T Recommendation I.363.1 (08/96), "B-ISDN ATM Adaptation Layer
   specification: Type 1 AAL".

   ITU-T Recommendation I.363.2 (09/97), "B-ISDN ATM Adaptation Layer
   specification: Type 2 AAL".

   ITU-T Recommendation I.363.5 (08/96), "B-ISDN ATM Adaptation Layer
   specification: Type 5 AAL".

   ITU-T Recommendation I.366.1 (06/98), "Segmentation and Reassembly
   Service Specific Convergence Sublayer for the AAL type 2".

   ITU-T Recommendation I.366.2 (02/99), "AAL type 2 service specific
   convergence sublayer for trunking".

   ITU-T Recommendation I.371 (08/96), "Traffic control and congestion
   control in B-ISDN".

   ITU-T Recommendation Q.763 (09/97), "Signalling System No. 7 - ISDN
   user part formats and codes".

   ITU-T Recommendation Q.765, "Signalling System No. 7 - Application
   transport mechanism".

   ITU-T Recommendation Q.931 (05/98): "Digital Subscriber Signalling
   System No.  1 (DSS 1) - ISDN User-Network Interface Layer 3
   Specification for Basic Call Control".

   ITU-T Recommendation Q.2630.1 (1999), "AAL Type 2 Signalling Protocol
   (Capability Set 1)".

   ITU-T Recommendation Q.2931 (10/95), "Broadband Integrated Services
   Digital Network (B-ISDN) - Digital Subscriber Signalling System No.
   2 (DSS 2) - User-Network Interface (UNI) - Layer 3 specification for
   basic call/connection control".

   ITU-T Recommendation Q.2941.1 (09/97), "Digital Subscriber Signalling
   System No. 2 - Generic Identifier Transport".




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   ITU-T Recommendation Q.2961 (10/95), "Broadband integrated services
   digital network (B-ISDN) - Digital subscriber signalling system no.2
   (DSS 2) - additional traffic parameters".

   ITU-T Recommendation Q.2961.2 (06/97), "Digital subscriber signalling
   system No. 2 - Additional traffic parameters: Support of ATM transfer
   capability in the broadband bearer capability information element."

   ITU-T Recommendation X.213 (11/1995), "Information technology - Open
   System Interconnection - Network service definition plus Amendment 1
   (08/1997), Addition of the Internet protocol address format
   identifier".

   ITU-T Recommendation V.76 (08/96), "Generic multiplexer using V.42
   LAPM-based procedures".

   ITU-T Recommendation X.680 (1997): "Information technology-Abstract
   Syntax Notation One (ASN.1): Specification of basic notation".

   ITU-T Recommendation H.246 (1998), "Interworking of H-series
   multimedia terminals with H-series multimedia terminals and
   voice/voiceband terminals on GSTN and ISDN".

   Rose, M. and D. Cass, "ISO Transport Service on top of the TCP,
   Version 3", RFC 1006, May 1987.

   Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications:
   ABNF", RFC 2234, November 1997.

   Handley, M. and  V. Jacobson, "SDP: Session Description Protocol",
   RFC 2327, April 1998.

   Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402,
   November 1998.

   Kent, S. and R. Atkinson, "IP Encapsulating Security Payload (ESP)",
   RFC 2406, November 1998.

2.2 Informative references

   ITU-T Recommendation E.180/Q.35 (1998): "Technical characteristics of
   tones for the telephone service".

   CCITT Recommendation G.711 (1988), "Pulse Code Modulation (PCM) of
   voice frequencies".

   ITU-T Recommendation H.221 (05/99),"Frame structure for a 64 to 1920
   kbit/s channel in audiovisual teleservices".



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   ITU-T Recommendation H.223 (1996), "Multiplexing protocol for low bit
   rate multimedia communication".

   ITU-T Recommendation Q.724 (1988): "Signalling procedures".

   Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980.

   Postel, J., "Internet protocol", STD 5, RFC 791, September 1981.

   Postel, J., "TRANSMISSION CONTROL PROTOCOL", STD 7, RFC 793,
   September 1981.

   Simpson, W., "The Point-to-Point Protocol", STD 51, RFC 1661, July
   1994.

   Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A
   Transport Protocol for Real-Time Applications", RFC 1889, January
   1996.

   Schulzrinne, H., "RTP Profile for Audio and Video Conferences with
   Minimal Control", RFC 1890, January 1996.

   Kent, S. and R. Atkinson, "Security Architecture for the Internet
   Protocol", RFC 2401, November 1998.

   Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
   Specification", RFC 2460, December 1998.

   Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg, "SIP:
   Session Initiation Protocol", RFC 2543, March 1999.

   Greene, N., Ramalho, M. and B. Rosen, "Media Gateway control protocol
   architecture and requirements", RFC 2805, April 1999.

3. DEFINITIONS

   Access Gateway: A type of gateway that provides a User to Network
   Interface (UNI) such as ISDN.

   Descriptor: A syntactic element of the protocol that groups related
   properties.  For instance, the properties of a media flow on the MG
   can be set by the MGC by including the appropriate descriptor in a
   command.

   Media Gateway (MG): The media gateway converts media provided in one
   type of network to the format required in another type of network.
   For example, a MG could terminate bearer channels from a switched
   circuit network (e.g., DS0s) and media streams from a packet network



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   (e.g., RTP streams in an IP network).  This gateway may be capable of
   processing audio, video and T.120 alone or in any combination, and
   will be capable of full duplex media translations.  The MG may also
   play audio/video messages and performs other IVR functions, or may
   perform media conferencing.

   Media Gateway Controller (MGC): Controls the parts of the call state
   that pertain to connection control for media channels in a MG.

   Multipoint Control Unit (MCU): An entity that controls the setup and
   coordination of a multi-user conference that typically includes
   processing of audio, video and data.

   Residential Gateway: A gateway that interworks an analogue line to a
   packet network. A residential gateway typically contains one or two
   analogue lines and is located at the customer premises.

   SCN FAS Signalling Gateway: This function contains the SCN Signalling
   Interface that terminates SS7, ISDN or other signalling links where
   the call control channel and bearer channels are collocated in the
   same physical span.

   SCN NFAS Signalling Gateway: This function contains the SCN
   Signalling Interface that terminates SS7 or other signalling links
   where the call control channels are separated from bearer channels.

   Stream: Bidirectional media or control flow received/sent by a media
   gateway as part of a call or conference.

   Trunk: A communication channel between two switching systems such as
   a DS0 on a T1 or E1 line.

   Trunking Gateway: A gateway between SCN network and packet network
   that typically terminates a large number of digital circuits.

4. ABBREVIATIONS

   This recommendation defines the following terms.

   ATM          Asynchronous Transfer Mode
   BRI          Basic Rate Interface
   CAS          Channel Associated Signalling
   DTMF         Dual Tone Multi-Frequency
   FAS          Facility Associated Signalling
   GW           GateWay
   IANA         Internet Assigned Numbers Authority
   IP           Internet Protocol
   ISUP         ISDN User Part



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RFC 2885                    Megaco Protocol                  August 2000