Re: [Tsvwg] overlapping TCP segments during reassembly

Caitlin Bestler wrote:

> On Monday, August 25, 2003, at 08:56 PM, Murali Bashyam wrote:
>
> > Hi
> >
> > Is there any guidelines outlined by any TCP RFC's  for determining what
> > data in the sequence space to keep and what to drop during TCP out of
> > order packet reassembly when there are overlaps? The BSD code tries to
> > trim the incoming segment when there is an overlap with a previous
> > segment in sequence space, and trims the already queued segments when
> > there is an overlap with succeeding segments in sequence space. I was
> > curious abt the motivation behind this strategy.
> >
> > Murali
> >
>
> Certain things are implied:
>
> 1) overlaps indicate retransmissions.
>
> 2) multiple valid segments must all have the same value
>     for any given byte in the TCP stream, i.e. the
>     retransmit can only correct transmission errors
>     it cannot "fix" the data.
>
> 3) you can only deliver a given byte to the TCP consumer once.
>
> So, if you have a buffered but undelivered sequence, should
> you replace it with new content? Well, since you know the
> values are the same, why not optimize the copy by simply
> not performing it?

Right,  based on these assumptions, that was the policy i was leaning
towards, can i simply apply all the trimming  i need to do on the  incoming
segment and always honour the already buffered data? Would this end up
violating any delivery semantics?

Murali

>
>
> Caitlin Bestler - cait@asomi.com - http://asomi.com/
>
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