Re: M2PA BSN dis-ordering

Bibhuti,

Bibhuti Bhusan Tosh wrote:                                         (Fri, 26 May 2006 14:30:09)
> Thanks Brian
> 
>     For the details. But on my point of view the first DATA with FSN = 4 and 
> BSN =12 is valid one and endpoint B flushes all the packets upto FSN = 12 at 
> its side. So when it again receives a packet with FSN=5(correct) and 
> BSN=11(incorrect i.e. already flushed) then this packet will be ignored.

It needs to be processed because M2PA cannot negatively acknowledge the valid
FSN as would Q.703.

>     As per you both the packets are invalid? Or only last packet is invalid. 
> kindly clarify this.

Both packets are valid (they have a monotonically increasing FSN per RFC 4165
section 4.2.1), one simply contains an abnormal BSN.  See test case 3.8.10
and 3.8.11 in draft-bidulock-m2pa-test-06.txt.

--brian

> 
> Regards,
> Bibhuti Bhusan Tosh
> 
> ----- Original Message ----- 
> From: "Brian F. G. Bidulock" <[email protected]>
> To: "Bibhuti Bhusan Tosh" <[email protected]>
> Cc: <[email protected]>
> Sent: Friday, May 26, 2006 1:50 PM
> Subject: Re: [Sigtran] M2PA BSN dis-ordering
> 
> 
> > Bibhuti,
> >
> > If you are following Q.703, the handling is per that standard.  One
> > isolated abnormal BSN is ignored, but two consecutive abnormal BSNs
> > cause the link to be put out of service.  So at the end of your sequence
> > B sends FSN=14 BSN=4 and FSN=15 BSN=5, however, if another abnormal BSN
> > follows, OUT-OF-SERVICE is sent from B.
> >
> > You can see this in test cases 3.8.10 and 3.8.11 in
> > draft-bidulock-sigtran-m2pa-test-06.txt and in Q.781/Test 8.10 and
> > Q.781/Test 8.11.  T7 is not impacted by the abnormal BSN per the Q.703
> > SDLs because the abnormal BSN does not negatively or positively
> > acknowledge any message.
> >
> > But this is defined by SS7 MTP2 and not altered by M2PA: therefore, it
> > is of some advantage to learn how a traditional SS7 link works before
> > working with M2PA.
> >
> > --brian
> >
> > Bibhuti Bhusan Tosh wrote:             (Fri, 26 May 2006 11:09:32)
> >>
> >>    Hi All
> >>
> >>
> >>
> >>    Kindly  consider  the following call flow and suggest me for the valid
> >>    FSN and BSN values.
> >>
> >>
> >>
> >>      A    B
> >>    ---------------------------- ----------------------------
> >>
> >>
> >>
> >>    MTP3  M2PA  SCTP                   SCTP  M2PA  MTP3
> >>    ----  ----  ----                  ----  ----  ----
> >>
> >>
> >>
> >>    User Data FSN=1 BSN=10 . .
> >>         ------------------------------------> . .
> >>    User Data FSN=2 BSN=10 . .
> >>         ------------------------------------> . .
> >>    User Data FSN=3 BSN=10 . . . .
> >>         ------------------------------------> . .
> >>                                  User Data FSN=11 BSN=3 . .
> >>         <------------------------------------ . . . .
> >>                                  User Data FSN=12 BSN=3 . .
> >>         <------------------------------------ . . . .
> >>                                  User Data FSN=13 BSN=3 . .
> >>
> >>         <------------------------------------ . . . .
> >>    User Data FSN=4 BSN=12 . . . .
> >>         ------------------------------------> . . . .
> >>                                  User Data FSN=? BSN=? . .
> >>         <------------------------------------ . . . .
> >>    User Data FSN=5 BSN=11 . . . .
> >>         ------------------------------------> . . . .
> >>                                  User Data FSN=? BSN=? . .
> >>         <------------------------------------ . . . .
> >>
> >>        Is there any impact of T7 timer expiry?
> >>
> >>
> >>
> >>    Regards,
> >>
> >>    Bibhuti
> >
> >> _______________________________________________
> >> 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/