Date: Mon, 14 Oct 1996 17:50:22 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: dg@root.com Cc: nate@mt.sri.com, question@freebsd.org, isp@freebsd.org Subject: Re: Modem latencies (was Re: ppp over vty possible ? ) Message-ID: <199610141650.RAA13959@labinfo.iet.unipi.it> In-Reply-To: <199610141700.KAA21134@root.com> from "David Greenman" at Oct 14, 96 10:00:04 am
next in thread | previous in thread | raw e-mail | index | archive | help
> >I usually average around ~120ms, although I have seen it drop to 115ms > >at times. If I turned off modem compression I think I could get it down > >to 110ms. > > Use smaller ping packets. ping -s 8 <other side> Does it work ? I thought there is a minimum packet size to hold the sequence number and timestamp (perhaps 8 bytes suffice) and then there is also the IP overhead. I am not sure if the size specified in "ping" is the overall packet size, or just the IP payload. Finally, I did some tests myself. It looks like the delay comes from the modem, although I have been unable to reduce it disabling compression. You don't lose much because you can have compression in ppp. Haven't tried disabling error correction, but that is something I am not much willing to give up, actually, since there is no other way to get error correction. Btw, ping -s SIZE with compression enabled is likely to give you always the same value independently of SIZE, since the packet is probably filled with constant data and the compression algorithms probably send little more than the length of the packets. Luigi ==================================================================== Luigi Rizzo Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it Universita' di Pisa tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ ====================================================================
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199610141650.RAA13959>