Date: Fri, 23 Dec 1994 17:16:26 -0800 From: David Greenman <davidg@Root.COM> To: "Daniel Stephens (CSC)" <stephens@mabuse.cas.usf.edu> Cc: freebsd-questions@freebsd.org Subject: Re: PPP and SLIP are amazingly slow. Message-ID: <199412240116.RAA04677@corbin.Root.COM> In-Reply-To: Your message of "Fri, 23 Dec 94 20:44:31 PST." <Pine.BSD.3.91.941223203514.702B-100000@mabuse.cas.usf.edu>
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>I'm interested in knowing what other people are getting for ping times >using 64k ICMP packets between slip client/server machines. Mine are as >follows: > >PPP 230ms >SLIP 198ms > >This seems awfully slow between two DX2/66 machines with 14.4 modems. >Everything I can find to read never seems to touch on the speed aspect of >either of these two protocols, so these times may be perfectly normal, >but I don't believe so. Quick (very poor) math shows that this isn't >even 5,000 bps. Something seems strange here. The above times are a little on the slow side, but well within normal. The reason they are longer than what you expect is because with v.42bis, the BTLZ data compression takes a considerable amount of time. The exact amount of time this takes varies depending on the modem but is usually on the order of 100ms for that size of packet. There is additionally a delay that the modem intentionally inserts in an attempt to buffer up an entire LAPM packet. I think this is on the order of 10-20ms depending on the modem. -DG
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