[e2e] TCP sequence number reset

Detlef Bosau detlef.bosau at web.de
Sun Mar 27 07:46:01 PDT 2011

On 03/25/2011 07:14 AM, Kacheong Poon wrote:

> What is your reason that a TCP connection cannot be seen as the same
> as an SCTP association with 1 single stream?  And what is your
> reason that "reusing a stream" requires "resetting a stream"?

At least one reason is that a sequence number in TCP is never defined by 
the user but negotiated in the startup phase of the flow.
Particularly, refer e.g. to RFC 793, recently used sequence numbers must 
not be used for a certain period of time.

In my opinion, your problem is twofold.

First, you propose mechanisms, such as resetting a TCP sequence number 
by the user, without giving a clear reason for doing so. And please keep 
in mind, that in science, we must give valid reasons for taking a 
certain decision. Particularly this holds true for adding mechanisms to 

Second, and admittedly I'm not quite familiar with SCTP, so I don't know 
the API/user view for it, any kind of protocol design is strongly 
governed by the abstraction we wand to achieve and the behaviour, which 
is presented to the user. And particularly, TCP provides a user with an  
ordered and  reliable stream of octets. Particularly, there is no random 
access to this stream. In that respect, a TCP flow between two endpoints 
resembles an inter process pipe. From that point of view, there is 
absolutely no need for an application to deal with certain sequence numbers.


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