FYI, re the effect of unnecessary drops on the net, Crovella's recent study
showed how the much vaunted "self-similarity" of traffic flows can actually
just result from TCPs becoming synchronized through common, dropping routers
-- the router drop policy/necessity coupled with individual TCPs, provide a
recurive algorithm analogous to those used to produce pretty fractal pictures.
No magic involved and everyone sharing the path slooooows waaaayyy dowwwwwwn.
Alex
PS: I can send a zipped (<200kB) copy of the paper if someone likes.
Phil Karn wrote:
>
> >Shouldn't we much rather promote the use of the ECN scheme instead?
>
> Probably.
>
> >Right, that's why ISP's should (and some do) configure their dial-up lines
> >to not allocate more than 3-4 packets per modem. For the same reason
> >wireless hosts which usually don't have to many flows active and sending at
> >the same time should also not have a much bigger interface buffer.
>
> I know this is a common practice, but it's always bothered me. I just
> don't like the notion of a node deliberately dropping a packet when it
> doesn't really have to. It means periodic packet drops and end-to-end
> retransmissions whenever the congestion window exceeds the buffer
> limit. These may not affect the throughput of the link in question,
> but it does affect the efficiency of the rest of the Internet. People
> complain about the added load of ICMP Source Quench messages, but
> surely the occasional small SQ message is a lot less overhead than the
> big data packet that has to be retransmitted because of an intentional drop
> at a bottleneck link.
>
> >That's how it also works in GSM. So you must also see the problems with VJ
> >header compression in IS-95. Is there a user configurable parameter to
> >change the max. number of retransmissions for the IS95-RLP like in GSM? An
>
> No. It's a fixed parameter. See my last message for an analysis of why it
> just doesn't make much difference to go larger.
>
> Some differences between CDMA and GSM: CDMA uses stronger FEC, and
> automatic power control. This tends to produce a sharp threshold
> effect: either the link works almost perfectly (e.g., 1-2% FER) or not
> at all (e.g., when no more transmitter power is available).
>
> Phil
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