I've been doing some quantified analysis of the performance of a few PSTN modems, mainly because I have one that I think is doing something odd.
The modems in question are: A Global Express connected to a P120/64Mb B Swann Smart connected to a P120/64Mb C D-Link connected to a P120/64Mb D Dynalink (I think) connected to a Celeron 733/128Mb The test is to run several bursts of pings and assess the average response time. The ping command is: ping -n -c10 -i0.01 -s8 <target> This is sending a burst of 10 short ping packets in 1 second with no DNS resolution. The source of these pings is a Celeron 850/128Mb connected to an ADSL link. The results for normal icmp (type 17) packets are: A 155msec B 190msec C 155msec D 220msec I then looked at pinging the same modems but this time with the ping packets encapsulated in isakmp (type 50) packets. The results are somewhat startling: A 195msec +40msec B 240msec +50msec C 205msec +50msec D 450msec +230msec The really odd bit is that modem D is the one attached to the Celeron 850/128Mb. Similar tests for ADSL (Celeron 850/128Mb) to ADSL sites show around 55msec for the type 17 packets with about 15msec additional for the type 50 packets for the tunnelling component despite the fact that the targets vary between P166/48Mb, Celeron 500/128Mb and Celeron 850/256Mb. Can anyone explain why there could be such a variation in the differences between type 17 and type 50 packets where a PSTN modem is involved? Agreed that packet sizes will be different with type 50 being bigger, but is it that much material? -- Howard. LANNet Computing Associates - Your Linux people Contact detail at http://www.lannetlinux.com "We are either doing something, or we are not. 'Talking about' is a subset of 'not'." -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug
