📄 draft-george-sigtran-m2peer-02.txt
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4.2 Message Transmission and ReceptionMessages are transmitted using the Data Request primitive from MTP3 toM2PA. The diagram shows the case where the Link is In Service. Themessage is passed from MTP3 of the source to MTP3 of the destination. MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- Message for transmission ------------> Send (Data Message) ------------> (SCTP sends message) Receive ------------> Received message ------------>4.3 Link Status IndicationIf SCTP sends a Communication Lost primitive to M2PA, M2PA notifiesMTP3 that the link is out of service. MTP3 responds in its usual way. MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- Communication Lost <------------ Out of Service <------------George, et al [Page 19] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20004.4 Link Status Message (Processor Outage)This example shows how M2PA responds to a local processor outage. M2PAsends a Link Status message to its peer. The peer M2PA notifies MTP3of the outage. MTP3 can then follow the processor outage procedures in[2]. MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- M2PA detects Local Processor Outage Link Status Processor Outage ------------> (SCTP sends message) Receive ------------> Remote Processor Outage ------------> Link Status Processor Outage Ended ------------> (SCTP sends message) Receive ------------> Remote Processor Outage Ceases ------------>George, et al [Page 20] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20004.5 Congestion Notification to Upper layerMTP3 expects notification of link congestion. In this example, it isassumed that SCTP notifies M2PA of congestion onset and abatement.If the congestion condition should continue long enough, MTP3 takesthe link out of service. In this case, it is possible to start thelink changeover procedure. MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- Implementation dependent indication of congestion onset <------------ Congestion Onset <------------ Implementation dependent indication of congestion abatement <------------ Congestion Abatement <------------George, et al [Page 21] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20004.6 Link DeactivationThe MTP3 can request that a SS7-IP link be taken out-of-service. M2PAuses the Abort message as shown below. MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- Stop ------------> Abort ------------> (SCTP performs its termination procedure) Communication Lost <------------ Out of Service <------------George, et al [Page 22] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20004.7 Link ChangeoverIn this example, MTP3 performs a changeover because the link went outof service. MTP3 selects a different link for retransmitting theunacknowledged messages.Note that in this example, the sequence numbers and messages requestedby MTP3 are sent from SCTP to M2PA in the Communication Lostprimitive. In general, the retrieval of sequence numbers and messagesis implementation-dependent.George, et al [Page 23] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 2000 MTP3 M2PA SCTP SCTP M2PA MTP3 ---- ---- ---- ---- ---- ---- Communication Lost <------------ Out of Service <------------ Retrieve BSN ------------> (M2PA locates first gap in received messages) Indicate BSN <------------ XCO (BSN) on another link ------------------------------------------------------------> Retrieve BSN <------------ Indicate BSN ------------> XCA (BSN) <------------------------------------------------------------ Retrieval Request and FSNC (FSNC = BSN from XCA message) ------------> (M2PA locates first gap in acknowledgements) Retrieved Message <------------ Retrieved Message <------------ Retrieval Complete <------------ Send messages on another link.George, et al [Page 24] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20005. SecuritySCN adaptation layers rely on SCTP to provide security. 6. IANA ConsiderationsThe SCTP (and UDP/TCP) Registered User Port Number Assignment for M2PAis TBD.The value assigned by IANA for the Payload Protocol Identifier in theSCTP Payload Data chunk is M2PA TBDThe SCTP Payload Protocol Identifier is included in each SCTP Datachunk, to indicate which protocol the SCTP is carrying. This PayloadProtocol Identifier is not directly used by SCTP but may be used bycertain network entities to identify the type of information beingcarried in a Data chunk.The User Adaptation peer may use the Payload Protocol Identifier as away of determining additional information about the data beingpresented to it by SCTP.7. AcknowledgementsThe authors would like to thank Ian Rytina for his valuable commentsand suggestions.George, et al [Page 25] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20008. References[1] ITU-T Recommendation Q.700, 'Introduction To ITU-T Signalling System No. 7 (SS7)'[2] ITU-T Recommendation Q.701-Q.705, 'Signalling System No. 7 (SS7) - Message Transfer Part (MTP)'[3] Bellcore GR-246-CORE 'Bell Communications Research Specification of Signaling System Number 7', Volume 1, December 1995[4] RFC 2719, Framework Architecture for Signaling Transport, October 1999[5] Stream Control Transmission Protocol, draft-ietf-sigtran-sctp-12.txt, July 12, 2000[6] SS7 MTP2-User Adaptation Layer, draft-ietf-sigtran-m2ua-00.txt, March 2000[7] ITU-T Recommendation Q.2210, 'Message transfer part level 3 functions and messages using the services of ITU-T Recommendation Q.2140'George, et al [Page 26] Internet Draft SS7 MTP2-User Peer-to-Peer Adaptation Layer July 20009. Author's AddressesTom George Tel: +1-972-519-3168Alcatel USA EMail: tom.george@usa.alcatel.com1000 Coit Road Plano, TX 75075 USARam Dantu, Ph.D. Tel: +1-972-234-6070 extension 211IPmobile EMail: rdantu@ipmobile.com1651 North Glenville, Suite 216Richardson, TX 75081USAMalleswar Kalla Tel: +1-973-829-5212Telcordia Technologies EMail: kalla@research.telcordia.comMCC 1J211R445 South StreetMorristown, NJ 07960USAHanns Juergen Schwarzbauer Tel: +49-89-722-24236SIEMENS AG HannsJuergen.Schwarzbauer@icn.siemens.deHofmannstr. 5181359 MunichGermanyGreg Sidebottom Tel: +1-613-763-7305Nortel Networks EMail: gregside@nortelnetworks.com3685 Richmond Rd,Nepean, Ontario Canada K2H5B7Ken Morneault Tel: +1-703-484-3323Cisco Systems Inc. EMail: kmorneau@cisco.com13615 Dulles Technology DriveHerndon, VA. 20171USAThis Internet Draft expires January 2001.George, et al [Page 27]⌨️ 快捷键说明
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