Date: Wed, 18 Apr 2001 08:05:31 -0700 From: Adi <lists@lists.grot.org> To: freebsd-net@freebsd.org Subject: ICMP echo measurement discrepancy Message-ID: <20010418080531.A35252@mighty.grot.org>
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I have a SDSL 768K lightly loaded DSL circuit terminating on a Flowpoint 2200 SDSL router connected to an ethernet switch off of which I have 3 FreeBSD machines: <redback sms1000>---768K SDSL---<router>==[switch]===(FreeBSD machine) I also control the ISP end of the DSL circuit. Depending on the *line encapsulation of the SDSL circuit*, different programs running ICMP echo report different packet loss rates with otherwise the _exact_ same setup. If I run ping interactively on the command line, as in > ping -c 10 -n x where x is the ISP router interface or any other "remote" IP address from one of my FreeBSD machines, I see no packet loss, and it's been that way since the day the circuit was installed. To keep a historical measurement, I have a perl script that does the ping every 5 minutes and keeps it in an RRD much like mrtg. In the perl script I've used both a system call to fping or used Net::Ping. I currently prefer the latter, but the effects are the same. If the SDSL line encapsulation is set to PPP over ATM then I typically see no packet loss at all to a variety of sites and have measurements over 4-5 months to prove it. However, if I use fping or Net::Ping from a script, it reports packet loss quite "often" -- in fact fping seems to always report packet loss (I count the number of returned packets in it's case). The changes to the network are made over 1 hop away from any FreeBSD machines and the traffic levels have remained the same and ping interactively reports different results from 2 different programs run in the background...I'm befuddled. Any ideas (I could run ping in the background I suppose)? Thanks, Adi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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