Date: Mon, 31 May 1999 05:09:58 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: bmah@CA.Sandia.GOV Cc: dgilbert@velocet.ca, wollman@khavrinen.lcs.mit.edu, freebsd-net@FreeBSD.ORG Subject: Re: Linux and Solaris tcp beating FreeBSD 4:1 Message-ID: <199905310309.FAA18066@labinfo.iet.unipi.it> In-Reply-To: <199905310017.RAA14008@stennis.ca.sandia.gov> from "Bruce A. Mah" at May 30, 99 05:17:26 pm
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> If memory serves me right, Luigi Rizzo wrote: > > > If you have access to both sides of the adsl link, i think you might > > more effectively implement link-level retransmits (i am not sure, but > > it might be that ppp already does this). > > > > It could be a relatively simple project to implement within a > > FreeBSD-based router or bridge > > Some of my former colleagues at UC Berkeley did some rather nifty > work (IMHO) in this area. Although originally designed for use with > (lossy) wireless LANs, it sounds applicable in this environment: yes, i did have hari's work in mind when i wrote the msg, although this case is simpler in a sense, but also might need one to deal with UDP traffic as well. The trivial way to implement this is by encapsulating pkts, with the disadvantage that in some cases one might hit against the MTU of the path. As an alternative one could periodically (but frequently) send an extra pkt with the headher (or some checksum) of the transmitted pkt, and the receiver ought to reply with same info for received packets. very short timeouts (0.1s or so) should be used to recover missing link-acks, or missing packets. I remember long ago we had a pair of Wellfleet routers which could do local retransmission on the point-to-point link, i think much like error-correcting modems do these days (except that such modems operate only on the last-sent packet, whereas i guess you want a slightly larger window. 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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