From owner-freebsd-isp Mon Oct 14 10:31:29 1996 Return-Path: owner-isp Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id KAA12752 for isp-outgoing; Mon, 14 Oct 1996 10:31:29 -0700 (PDT) Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id KAA12695 for ; Mon, 14 Oct 1996 10:29:58 -0700 (PDT) Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id SAA13998; Mon, 14 Oct 1996 18:03:35 +0100 From: Luigi Rizzo Message-Id: <199610141703.SAA13998@labinfo.iet.unipi.it> Subject: Re: Modem latencies (was Re: ppp over vty possible ? ) To: nate@mt.sri.com (Nate Williams) Date: Mon, 14 Oct 1996 18:03:35 +0100 (MET) Cc: isp@freebsd.org In-Reply-To: <199610141645.KAA00802@rocky.mt.sri.com> from "Nate Williams" at Oct 14, 96 10:45:01 am X-Mailer: ELM [version 2.4 PL23] Content-Type: text Sender: owner-isp@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > 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/ ====================================================================