[e2e] [tcpm] Question on RFC6298, Managing the RTO Timer and additional lost pakets in Recovery state

Michael Welzl michawe at ifi.uio.no
Thu Mar 3 06:54:02 PST 2016

> On 03 Mar 2016, at 15:31, Mark Allman <mallman at icir.org> wrote:
>> It says quote “(5.3) When an ACK is received that acknowledges new
>> data, restart the retransmission timer so that it will expire after
>> RTO seconds (for the current value of RTO).”
>> What is the definition of new data ?. The strict interpretation is
>> when SND.UNA advances, but it can also be that the highest SACKed
>> sequence number increases. The former case it is more likely that
>> RTO happens. 
> Seems like something we should have nailed down in the spec at some
> point after SACK became widely prevalent.  Alas.
> I think "new data" can be interpreted as "cumulative ACK advances".

This "new data" stuff is also all over RFC 5681. I remember being confused by it long ago, exactly with the same two possible interpretations that Ingemar writes below.
Back then I assumed that it must be me; I'm glad to see that I'm not the only one who got confused by this.

But maybe, in the occurrences in RFC 5681, it really was only me? Some of them are definitely clear, but maybe not all.


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