[e2e] [tcpm] RTTM + timestamps

Detlef Bosau detlef.bosau at web.de
Sat Jul 30 04:43:02 PDT 2011

Just see this post.

On 01/17/2011 03:35 PM, Alexander Zimmermann wrote:
> Eh... With RFC1323, you take RTT samples when loss occurs.

You don't take anything, particularly no RTT samples, when loss occurs.

>>   However, solving the retransmission ambiguity problem -
> The problem is solved, isn't it? Eifel?

The timer ambiguity was originally solved by Karn & Partridge. To my 
understanding, this ambguity does not even occur when timestamps are 
used. Do you agree?

> And a citation form Sally Floyd to that topic:
> "Inferring congestion vs. corruption at the transport level. There are also papers that investigate
> algorithms for the transport end-nodes to infer that certain drops are from corruption rather than
> congestion, without explicit feedback from routers. My own view would be that the burden is on such
> approaches to show that they are not ignoring legitimate congestion indications from the network."
> eg: S.Biaz and N. Vaidya. Discriminating Congestion Losses from Wireless Losses Using Interarrival
> Times at the Receiver. IEEE Symposium on Application-Specific Systems and Software Engineering and
> Technology, Mar 1999.

There are lots of papers in that direction, however, I don't see a 
reasonable way to infer the true reason for a concrete packet loss on an 
end to end basis.

And that is a different story from RTT sampling.

>> However, the current specs in RFC1323 make that use impossible, thus a modified signaling (receiver behavior) is a necessity.
>> The first central aspect of the above mentioned points is to resolve the retransmission ambiguity
> Again, Eifel?

Again, I think, Eifel solves a different problem.

Eifel deals with dectecting spurious timeouts.

Detlef Bosau
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