Date: Sat, 13 Nov 1999 15:31:23 +0100 (CET) From: Luigi Rizzo <luigi@info.iet.unipi.it> To: aron@cs.rice.edu (Mohit Aron) Cc: freebsd-net@FreeBSD.ORG, wollman@FreeBSD.ORG, jlemon@FreeBSD.ORG, julian@FreeBSD.ORG, bright@wintelcom.net Subject: Re: FreeBSD networking problems Message-ID: <199911131431.PAA12855@info.iet.unipi.it> In-Reply-To: <199911121642.KAA29642@cs.rice.edu> from Mohit Aron at "Nov 12, 1999 10:42: 7 am"
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> > i think the two of us already discussed this. I don't think this is a > > particularly good idea, especially: > > Well, 50 is too small. I needed 1000 for my WAN experiments, but the number what you are saying is "i can blast packets to the interface faster than it can drain them". Which means that you are causing _congestion_ on the local interface rather than somewhere in the middle of the net (and, your burst of 1000 packets might as well go to your next-hop router where you probably won't have as much queue space for your flows). You don't solve the problem by raising the queue to 1000, because in one year your gigahertz processor will need a queue of 2000, and so on. You solve the problem by noticing that you are pumping data too fast (ip_output fails, so you do know) and pacing the output appropriately. > As you said, the 833 packets need to be stored somewhere and you're also > right that the place is the socket buffer queue. But TCP can be bursty > during its operating specially when it gets big ACKs (or closely spaced ACKs so, fix TCP, the problem is there, not elsewhere (possible fix, not terribly complex: on overflow don't cut the window as done now, just schedule a call to the output loop after 1/HZ seconds). cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) http://www.iet.unipi.it/~luigi/ngc99/ ==== First International Workshop on Networked Group Communication ==== -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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