Re: M2PA: Link alignment when proving omitted
"Brian F. G. Bidulock" <[email protected]>
| Newsgroups | gmane.ietf.sigtran |
|---|---|
| Organization | http://www.openss7.org/ |
| Message-ID | <[email protected]> |
Soni, Soni Goel wrote: (Fri, 29 Jun 2007 12:22:37) > Hi Brian, > > Your question: > OTOH, why is M2PA-1 sending LSA "in response to Out of Service"? > LSA is sent in response to "Start". Make M2PA-1 ignore LSOOS in > Not-Aligned state. > > Answer: M2PA-2 has not yet received start. M2PA-1 needs to restart Timer > T2 and resend LSA, otherwise T2 will expire at M2PA-1 causing link > failure. That is the point of T2: that it expire and cause alignment failure if LSA is not received before it expires. It should not be restarting T2 in response, nor resending LSA. It should ignore LS-OOS when received in No-Aligned state (no proving). > > Later when M2PA-2 receives start and sends LSA, M2PA-1 will respond with > only LSOOS. > > This is also as per following test case in > draft-bidulock-sigtran-m2pa-test-08.txt - > 3.1.2. Timer T2 > ___________________________________________________________________ > | | > | CPT: IOT: SP B SP A | > | VAT: PT IUT | > | | > | <----------------- OUT-OF-SERVICE | > | OUT-OF-SERVICE -----------------> | > | :start | > | <----------------- ALIGNMENT | > | (Note) OUT-OF-SERVICE -----------------> | > | <----------------- ALIGNMENT (Note) | And the note says that each side may send additional OUT-OF-SERVICE or ALIGNMENT messages, but neither are in response to each other. In particular RFC 4165/4.1.3: The Link Status Alignment message replaces the SIO message of MTP2. This message is sent to signal the beginning of the alignment procedure. The Link Status Alignment message SHOULD NOT be transmitted continuously. M2PA MAY send additional Link Status Alignment until it receives Link Status Alignment, Link Status Proving Normal, or Link Status Proving Emergency from the peer. Your diagram looks like it is being sent in response to each LSOOS and the then when the other end gets LSA it "responds" with LSOOS. That sounds like continuous to me. --brian > | ! | > | ! T2 5.0 <= T2 <= 150.0 | > | ! | > | <----------------- OUT-OF-SERVICE | > | !out of service(AERM) | > | | > |___________________________________________________________________| > > Thanks, > Soni > > -----Original Message----- > From: Brian F. G. Bidulock [mailto:[email protected]] > Sent: Friday, June 29, 2007 12:02 PM > To: Soni Goel > Cc: [email protected] > Subject: Re: [Sigtran] M2PA: Link alignment when proving omitted > > Soni, > > Soni Goel wrote: > (Fri, 29 Jun 2007 10:57:24) > > Hi, > > > > This is regarding the Link alignment when proving is omitted. > > As per message flow given below, link is not able to come in-service > > because M2PA-2 receives Link status Align after sending Link Status > > Ready. > > > > I would suggest M2PA-2 to resend Ready on receiving Align, while timer > > T1 is running. This is as per following statement in RFC 4165, Section > > 4.1.3 Link Alignment - > > "If the Link Status Ready message is sent, then M2PA MAY send > additional > > Link Status Ready messages while timer T1 is running." > > > > Please let me know your feedback. > > > > > > MTP3-1 M2PA-1 SCTP-1 SCTP-2 M2PA-2 MTP3-2 > > ---- ---- ---- ---- ---- ---- > > . . . . . . > > Start . . . . . > > ------------> . . . . > > . Associate . . . . > > . ------------> . . . > > . . . . . . > > . . (SCTP Association . . > > . . procedure) . . > > . . . . . . > > . Communication Up Communication Up . > > . <------------ ------------> . > > . . . . . . > > . Link Status Out of Service . . > > . ------------------------------------> . > > . . . . . . > > . Link Status Alignment . . . > > . ------------------------------------> . > > . . . . . . > > . Start timer T2 . . . > > . . . . . . > > . . Link Status Out of Service . > > . <------------------------------------ . > > . Link Status Alignment . . . > > . ------------------------------------> . > > . . Link Status Out of Service . > > . <------------------------------------ . > > . Link Status Alignment . . . > > . ------------------------------------> . > > . . Link Status Out of Service(2) . > > . <------------------------------------ . > > . . . . . Start > > . . . . <------------ > > . . . Link Status Alignment(2) . > > . <------------------------------------ . > > . . . . . . > > . Link Status Alignment(response to Out of Service(2)) . > > . ------------------------------------> . > > OTOH, why is M2PA-1 sending LSA "in response to Out of Service"? > LSA is sent in response to "Start". Make M2PA-1 ignore LSOOS in > Not-Aligned state. > > --brian > > > . . . . Start timer T1 > > . . . Link Status Ready(2) . > > . <------------------------------------ . > > . . . . . . > > . Stop timer T2 . . . > > . Link Status Alignment(response to Alignment(2)) . > > . ------------------------------------> . > > . . . . Link fails due to . > > . . . . Alignment received in. > > . . . . Ready state . > > . . . . . > > . . Link Status Out of Service . > > . <------------------------------------ . > > . . . . . . > > . . . . . . > > . Link inservice(received Ready(2)) . . > > . Link Status Ready(response to Ready(2)) . . > > . ------------------------------------> . > > . . . . . . > > . . . . . . > > . Link Failure (received Out of Service from M2PA-2) . > > . Link Status Out of Service . . > > . ------------------------------------> . > > . . . . . . > > . . . . . . > > > > Thanks, > > Soni > > > > _______________________________________________ > > Sigtran mailing list > > [email protected] > > https://www1.ietf.org/mailman/listinfo/sigtran > > -- > Brian F. G. Bidulock > [email protected] > http://www.openss7.org/ -- Brian F. G. Bidulock [email protected] http://www.openss7.org/