Subject: Re: [Sigtran] M2PA Flush Buffers

From: "TOLGA ASVEREN" <[email-masked]>
Date: Tue, 4 Feb 2003 07:49:58 +0200

Tom,

4.2.4 says:
"The Flush Buffers and Continue commands allow M2PA to resume normal
operations (i.e., transmission of messages to SCTP and receiving
messages from SCTP) after a processor outage (local and/or remote)
ceases.

If M2PA receives a Flush Buffers command from MTP3, M2PA:

   (a) SHALL NOT transmit any messages to SCTP that are currently
       waiting to be transmitted to SCTP. These messages SHALL be
       discarded.

   (b) SHALL discard all messages currently waiting to be passed
       to MTP3."
So M2PA will stop sending messages to SCTP but continue to receive messages
from SCTP and will discard them(?) What about scenarios, where a SCTP
message, which needs to be discarded is ready to be delivered to M2PA
(because of SCTP retransmission) after Continue?

     Tolga

Tolga,

The interface between SCTP and its upper layer does not provide for a
way to flush the SCTP buffers. So the approach we took in M2PA was to
discard the messages waiting to be sent or received.

If you have some implementation-dependent means for flushing SCTP
buffers and you can use it to meet the M2PA requirements, then that
would be, well, an implementation matter.

tomG.

TOLGA ASVEREN wrote:
>
> Tom,
>
> I mean, during flushing, what to do with SCTP buffers?
>
>    Tolga
> --- Tom George <[email-masked]> wrote:
> > Tolga,
> >
> > I am not sure what you are asking. Could you be more
> > specific?
> >
> > tomG.
> >
> > TOLGA ASVEREN wrote:
> > >
> > > Tom,
> > > Is there also a decision about what to do while
> > flushing buffers?
> > >
> > >    Tolga

--
* Tom George       PB7-24001 (near B-21)      [email-masked]  *
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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Mon, 3 Feb 2003 23:40:46 -0700

Tolga,

Flush buffers is only used after recovery from local processor outage.
The SS7 peer should not be sending any messages and cannot expect
acknolwedgement for any messages that are outstanding when it receives
the remote processor outage indication.

Flush buffers is only performed on recovery from local processor outage
after MTP Level 3 T1 timeout or remote changeover (which normally takes
about a second or two).

Also, changeover orders have been sent to the other side before buffer
flushing occurs and the other side should have already placed the link
out of service.

So, in any case, the only messages are messages caught in local transmit
and retransmit buffers.  Any message which SCTP happens to send or receive
late will merely interfere with the new alignment process and will be
discarded anyway.

That is why I asked several times: what does it matter?  It doesn't.

--brian

TOLGA ASVEREN wrote:                           (Tue, 04 Feb 2003 07:49:58)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/