Date: Mon, 14 Oct 1996 18:03:35 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: nate@mt.sri.com (Nate Williams) Cc: isp@freebsd.org Subject: Re: Modem latencies (was Re: ppp over vty possible ? ) Message-ID: <199610141703.SAA13998@labinfo.iet.unipi.it> In-Reply-To: <199610141645.KAA00802@rocky.mt.sri.com> from "Nate Williams" at Oct 14, 96 10:45:01 am
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> PING trout.mt.sri.com (206.127.76.104): 56 data bytes > 64 bytes from 206.127.76.104: icmp_seq=0 ttl=255 time=156.701 ms > 64 bytes from 206.127.76.104: icmp_seq=1 ttl=255 time=150.206 ms > 64 bytes from 206.127.76.104: icmp_seq=2 ttl=255 time=132.611 ms > 64 bytes from 206.127.76.104: icmp_seq=3 ttl=255 time=124.156 ms ... > 64 bytes from 206.127.76.104: icmp_seq=7 ttl=255 time=120.429 ms > 64 bytes from 206.127.76.104: icmp_seq=8 ttl=255 time=120.162 ms Once overheads are included, this is approx 80 bytes --> 800 bits --> 27ms if sent as raw bits @28.8, plus 7ms to transfer to the modem @115.2K (assuming the modem is an external device). Even by summing up times the overhead is 156/2 - (27+7) = 44ms each way. This at the first packet; afterwards, compression becomes more effective and it looks like communication times goes down by 19ms each side. 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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