Date: Mon, 14 Oct 1996 15:29:34 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: exidor@nimbus.superior.net (Christopher Masto) Cc: question@freebsd.org, isp@freebsd.org Subject: Re: ppp over vty possible ? Message-ID: <199610141429.PAA13506@labinfo.iet.unipi.it> In-Reply-To: <199610141332.JAA16872@nimbus.superior.net> from "Christopher Masto" at Oct 14, 96 09:32:14 am
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> Luigi Rizzo writes: > > When I use ppp from home (14.4 modem) with telnet (and possibly > > other apps, I haven't checked), the RTT is suspiciously close to > > 200 ms (within 10ms; I have a modified kernel which prints the > > current RTT and bandwidth on every connection). As you can imagine, > > typing this way is not the most pleasant thing in the world. > > That doesn't sound very suprising to me. I typically see 200-300ms > ping times over a modem running PPP. There's a lot of turnaround > latency in 14.4/28.8 modems. Can you give more details ? The same problem does not occur when I use a plain connection (e.g. using the "term" mode of ppp). Now, for sure it might be something in the modem, e.g. it sees a burst of bytes coming in and decides it is worth waiting for a sufficiently large block to attempt compression. But -- apart for this being a symptom of poor design in the modem -- what is intriguing me is the delay -- 200ms -- so close to what is a TCP_FASTTIMEOUT. 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/ ====================================================================
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