Subject: Re: [M2PA] A few questions regarding to changeover...

From: Tom George <[email-masked]>
Date: Fri, 12 Oct 2001 16:45:47 -0500

Patrick,

Comments below. 

tomG.

Patrick Lam wrote:
> 
> Hi:
> 
> I have the following questions:
> 
> 1.  On p.35 of draft-ietf-sigtran-m2pa-03.txt (4.2.6 Changeover), part
> (a) of what "M2PA shall retrieve from SCTP in order and deliver to MTP3:
> 
> (a) any transmitted User Data messages beginning with the first
> unacknowledged message with stream sequence number greater than FSNC."
> 
> i.  Should M2PA retrieve messages with sequence number greater than FSNC
> no matter whether the messages have been acknowledged or not?

Yes. The FSNC tells the last message received by the remote end's MTP3. 

> ii.  If not, what do we do with an  unacknowledged message with stream
> sequence number *smaller* than FSNC?

Do not deliver those messages to MTP3 for transmission on an alternate
link.

> iii.  Does "unacknowledged" mean "unacknowledged" from the remote SCTP
> or remote MTP3?

SCTP.

> 
> 2.  According to p.46 of draft-ietf-sigtran-m2pa-03.txt (the figure that
> depicts Link Change Over procedures), the M2PA has to "locates first gap
> in acknowledgements".  However, according to Sockets API Extensions for
> SCTP (draft-ietf-tsvwg-sctpsocket-01.txt), I can't find this piece
> information in any structs listed in the doc.
> 
> So how am I supposed to  "locates first gap in acknowledgements" from
> SCTP API?

You will not be able to do this with the Sockets API, as Brian B. also
pointed out.

> Thanks a lot in advance,
> Patrick.

-- 
* Tom George        972-519-3168         [email-masked]   *
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