Date: Mon, 14 Oct 1996 11:02:47 -0400 From: exidor@nimbus.superior.net (Christopher Masto) To: luigi@labinfo.iet.unipi.it (Luigi Rizzo) Cc: exidor@nimbus.superior.net (Christopher Masto), question@freebsd.org, isp@freebsd.org Subject: Re: ppp over vty possible ? Message-ID: <199610141502.LAA19690@nimbus.superior.net> In-Reply-To: <199610141429.PAA13506@labinfo.iet.unipi.it>; from Luigi Rizzo on Oct 14, 1996 15:29:34 %2B0100 References: <199610141332.JAA16872@nimbus.superior.net> <199610141429.PAA13506@labinfo.iet.unipi.it>
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Luigi Rizzo writes: > > 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. There's a lot more overhead to send one character over a PPP connection compared to a terminal. If you're just in a term mode, you send the character and the remote side echos it back. If you're doing telnet, you've got it wrapped in TCP, IP, PPP, etc. TCP does reliable delivery so it has to be acknowledged, and I think maybe PPP does also? Only then do you get the echo, which has to go through the same process. If you haven't done so, you can turn off your modem's v.42bis compression and see if it helps. -- / Christopher Masto \ / Superior Net Services \ / Your vote counts \ | exidor@superior.net | | $24.95/month unlimited use | | Support free speech | \ Programmer/Tech / \ http://www.superior.net/ / \ HappyNet for all /
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