Subject: Re: [Tsvwg] [Sigtran] SCTP - Processing of Abort chunk, when bundled with other chunks

From: Randall Stewart <[email-masked]>
Date: Thu, 16 Sep 2004 05:36:41 -0400

Subhahini:

Comments in-line..

Subhashini wrote:
> Hi,
> 
> Please refer below the statements from three different sections of
> RFC 2960.
> 
> Section 6.10 says "An endpoint MUST process received chunks in their
> order in the packet".
> 
> Section 9.1 says "An endpoint MUST NOT respond to any received packet
> that contains an Abort chunk."
> 
> Section 3.3.7 says "Control chunks (except for INIT, INIT ACK and
> SHUTDOWN COMPLETE) MAY be bundled with an ABORT but they MUST be
> placed before the ABORT in the SCTP packet, or they will be ignored
> by the receiver."
> 
> 
> Sections 6.10 and 3.3.7 together convey that the chunks bundled
> before ABORT chunk should be processed as they are in the order.
> 
> Sections 9.1 and 3.3.7 are contradicting to each other.

No, this is not true... you DON'T have to respond to the chunk
even though you process it... you can either
do as you say.. do a whole pre-scan.. which most implementations
do NOT do..

Or.. more likely you will process things and send out responses
at the end of packet processing... so... in your example

-----
cooke-echo
-----
abort
------

1) I process the cookie-echo, prepare a cooke-ack and place
    it in my list of chunks that will be sent in my local sctp queue
    (note this DOES NOT send the chunk).
2) Process the abort, and destroy the TCB
3) Skip my output processing (i.e. bundling of the chunks
    for output) since my TCB was destroyed.

Soo... basically if you choose NOT to bundle chunks you will need
to do a pre-scan looking for an abort :-D

R

> 
> Suppose say, if Cookie Echo chunk is bundled with before Abort chunk
> in a packet, since the chunks should be processed in the order,
> Cookie Ack will be sent to the peer first and then the Abort chunk
> will be processed to abort the association. Is my understanding
> correct? Otherwise, do we need to scan whole packet for the presence
> of Abort chunk and then we need to decide to ignore the other chunks
> in the packet?
> 
> Please clarify.
> 
> thanks, Subhashini ...
> 
> 
> 
> 
> ------------------------------------------------------------------------
> 
> 
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