Terje Mathisen <"terje.mathisen at tmsw.no"> writes:
>The end points needs at least bandwidth*latency buffers simply to keep
>the flow going, while routers in between should have very little buffer
>space, simply because that will allow the end points to discover the
>real channel capacity much sooner.
For traditional TCP (single flow), you need bandwidth*latency as
sockbuf at both ends plus the same at the bottleneck router. Some
of the new TCP congestion control systems can do with less, and
still fill the link if they are the only flow.
>You might claim that a little intermediate buffer space is a good thing,
>in that it can allow a short-term burst of packets to get through
>without having to discard other useful stuff, but only as long as most
>links have spare capacity most of the time.
There was some work a few years ago that suggested that you needed
about bandwidth*latency/sqrt(n) buffering at a link with n bottlenecked
TCP flows, in order to make sure that the flows could actually use
the link. There was also a suggestion that you could get away with
less, but that neemed to require a quite large n in practice.
David.
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