[e2e] tcp retransmission packet size.

[Tianbo Kuang]

Thank you for all your answers.

--Tianbo

Dennis Rockwell wrote:

> On 26 Nov, Tianbo Kuang wrote:
>
> > I noticed in a captured trace that a TCP sender actually retransmitted a
> > bigger packet than the orignal one (after the ACK was dropped in the
> > network). My question is,
> > (1) Is this allowed by specification?
>
> Yes, and encouraged.  You're not retransmitting the segment
> (which is a transient entity), you're retransmitting
> starting with the lost bytes.  Any bytes that have been
> enqueued after the initial transmission will be included, up
> to the maximum segment size.
>
> > (2) If so, that means that a TCP receiver will always have to use the
> > duplicated packet as the useful data as it contains more information. Is
> > that true in the implementation?
>
> Yes.  The reassembly code puts together a sequence of bytes
> and trims away duplicates.  It doesn't matter which copy you
> delete, they're identical.
>
> Dennis