[e2e] Spurious Timeouts in mobile wireless networks, was: Re: Retransmission Timouts revisited

[Francesco Vacirca]

> The "spurious timeout" problem often claimed in mobile wireless networks 
> thus should be basically a problem with extreme delay spikes.

This is correct: delay spikes that are not "seen" in the first and 
second order moments of rtt distributions and that are used for the RTO 
setting.

> 
> As to my understanding, we can exclude other problems, the only problem 
> with TCP in mobile wireless networks are unexpected, or unforeseeable 
> respectively, delay spikes or a sudden increase of delays.

Well, packet losses are the main problem... and they should be hidden to 
TCP with wireless link layer protocol and persistant retransmissions...


Spurious timeouts are a second (marginal) problem that in my opinion 
(and in my research) are not frequent events in a well engineered 
GPRS/UMTS network.

Francesco

> 
> This can be due to
> - scheduling (voice is priorized over data)
> - route change (I don´t know whether this is that important, because 
> much of this is micromobility)
> - changes in physical path properties.
>