[e2e] TCP sequence number reset

Joe Touch touch at isi.edu
Tue Oct 11 09:02:30 PDT 2011

Hi, Kristen,

On 10/10/2011 3:45 AM, Kristen Eisenberg wrote:
> Just want to get some opinion from the list members about an
> idea proposed in an IETF draft. The equivalent idea when
> applied to TCP is sequence number reset. The idea is that
> assuming an application can access TCP sequence number with
> each byte of data, an app is allowed to reset the TCP sequence
> number when it wants to. The sequence number is set to a number
> not acceptable (add 231) in the current connection. Note that
> there is no clear usage proposed in that draft nor any reason
> that it is needed, just a mechanism to do it. I want to see
> whether folks on this list think that it is a good or bad idea?
> And why?

There was a long thread on this topic on this list; check the archives 
starting March 24, 2011.

My view of the conclusion - bad idea. TCP has only one stateful 
handshake - during connection establishment. Resetting the numbers 
requires a stateful handshake in the middle of a connection, which TCP 
doesn't support. Adding a mechanism to do so is as much work as starting 
a new TCP connection, if not more.


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