Questions about Internet Packet Losses

William Allen Simpson wsimpson at
Tue Jan 14 16:23:44 UTC 1997

Yes, Bakul, keeping a central RTT cache per destination is a good idea.
Most good stacks use it already.  I think it was recommended in Host
Requirements circa 1989.

Keeping a per destination cache of Path RTT, Path MTU, and a Quality
measurement was required in my initial IPng Neighbor Discovery design
several years ago, before that was destroyed in the rewrite by committee.

> From: Bakul Shah <bakul at>
> [Thinking aloud here...]
> Perhaps a part of the TCP congestion avoidance algorithm can be
> factored out in some sort of a `traffic central' module that tries
> to give you the best bandwidth/packet loss estimate it has for a
> given route provided you keep it updated with what you learn (i.e.
> TCP tells it when a packet is lost etc).  A new TCP connection can
> then immediately start off with a bigger window (and won't open the
> window too wide too quickly).  Multiple connections between two
> hosts can avoid what would be largely redundant estimate
> computation.  Even a UDP app. can try to benefit from this (such as
> for communication where bounded delay is more critical than packet
> loss).  Other `traffic conditions' input can also be fed into this
> module [perhaps as part of some future routing protocol].  Combining
> this `quality' of a route aspect into routing protocols may make
> sense in the long run....

WSimpson at
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BSimpson at
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