[e2e] TCP sequence number reset

Joe Touch touch at isi.edu
Thu Mar 24 22:15:16 PDT 2011

On 3/24/2011 10:02 PM, Kacheong Poon wrote:
> On 03/25/11 06:47 AM, Joe Touch wrote:
>>> The draft is draft-ietf-tsvwg-sctp-strrst-09.txt and I think
>>> the analogy to TCP is accurate.
>> SCTP includes the idea of individual streams, and the value of the
>> sequence number has a meaning within a stream. In the above draft, it's
>> used to allow a stream to be reused within an E2E association.
> If you check the draft carefully, it proposes a mechanism to reset
> the transmission sequence number (TSN) of an association. This
> is equivalent to resetting TCP sequence number. The stream
> sequence number (SSN) is per stream but TSN is per association.

The SCTP TSN is similar to TCP's sequence number, but due to the 
relationship to the SSNs they're not directly related. Resetting the TSN 
appears to be useful only in relation to resetting all the SSNs at once, 
since they are based on the TSN. The document lacks any direct rationale 
for TSN reset other than this, which is implied (this should be 
explicitly addressed, IMO).

There's no notion of separate streams in TCP, so there's no purpose in 
resetting TCP's sequence number, thus the analogy doesn't hold.


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