Re: [dcp] sequence numbers on resend

> 
> My first instincts are:
> 
> (1) DCCP-Responses are never retransmitted. If a Response is lost, the side
> that initiated the connection will retransmit the Request eventually.

correlary: t3 needs to be very large. This could lead to some pretty
big tables of timers not associated with real sessions.

> 
> (2) I'm not sure it matters, in practice, whether retransmitted Requests
> have new sequence numbers. Therefore, for consistency, I would choose that
> they would.

I'd argue against it for a few reasons:

  1] the above - using the same ISN would let you use the same
  connection and not have orphaned timers.

  2] (rvcd_ackn == local_isn) has to match on each side to complete
  the handshake.. extending that to (rcvd_ackn is_in
  list_of_local_isns) is an implementation hassle - requiring state
  maintenance for each resend.

  3] least surprise - in TCP a retransmit is a RE-transmit, the same
  TCP level data is simply sent again. this way you only have to worry
  about dups not which one is "right". 

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