Re: [Vyatta-users] latency tool
You could possibly use a sniffer and then generate a data stream and then look at the difference between timestamps that the sniffer tacked on each packet. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Thompson Sent: Friday, January 18, 2008 1:28 PM To: Dave Roberts Cc: vyatta-users@mailman.vyatta.com Subject: Re: [Vyatta-users] latency tool On Jan 17, 2008, at 7:15 AM, Dave Roberts wrote: I am looking for a tool that is able to measure the (one-way) latency or delay. From what i know ping or traceroute are only able to measure the RTT. There is no widely-used, standard tool that I know of. I'm sure there is some code you could snarf from somewhere, though. I think the reason that a standard tool doesn't exist is that the problem of latency testing essentially degenerates to one of clock synchronization between the source and the destination. If you do RTT measurements, the transmitter and receiver are the same box, so the clocks are automatically synchronized. If you do one-way testing, you need to get clock synchronization between the source and dest nodes. If you need highly accurate measurements, then you might need something like GPS to help you synchronize (as opposed to NTP, which is great for basic date/time stuff, but won't help you much with microsecond resolution timing). Once you have the clock synchronization issue nailed, the code to do the measurement is only about half a page of C on both the source and test: take a timestamp, transmit a UDP packet out, receive it sometime later, and take another timestamp. http://www.caida.org/workshops/isma/0312/slides/dveitch_bwest_probing.pdf http://www.cis.udel.edu/~mills/database/papers/history.pdf http://dast.nlanr.net/NPMT/ ... ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
Re: [Vyatta-users] latency tool
On Jan 17, 2008, at 7:15 AM, Dave Roberts wrote: I am looking for a tool that is able to measure the (one-way) latency or delay. From what i know ping or traceroute are only able to measure the RTT. There is no widely-used, standard tool that I know of. I’m sure there is some code you could snarf from somewhere, though. I think the reason that a standard tool doesn’t exist is that the problem of latency testing essentially degenerates to one of clock synchronization between the source and the destination. If you do RTT measurements, the transmitter and receiver are the same box, so the clocks are automatically synchronized. If you do one-way testing, you need to get clock synchronization between the source and dest nodes. If you need highly accurate measurements, then you might need something like GPS to help you synchronize (as opposed to NTP, which is great for basic date/time stuff, but won’t help you much with microsecond resolution timing). Once you have the clock synchronization issue nailed, the code to do the measurement is only about half a page of C on both the source and test: take a timestamp, transmit a UDP packet out, receive it sometime later, and take another timestamp. http://www.caida.org/workshops/isma/0312/slides/dveitch_bwest_probing.pdf http://www.cis.udel.edu/~mills/database/papers/history.pdf http://dast.nlanr.net/NPMT/ ... ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
Re: [Vyatta-users] latency tool
Hi Troopy, You want to look at netperf... http://www.netperf.org/ Cheers, Robert. Troopy . wrote: Hello, i have a question not directy related to Vyatta but more to networking. I am looking for a tool that is able to measure the (one-way) latency or delay. From what i know ping or traceroute are only able to measure the RTT. Thanks Troopy __ Désirez vous une adresse éléctronique @suisse.com? Visitez la Suisse virtuelle sur http://www.suisse.com ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
Re: [Vyatta-users] latency tool
If you aren't all that worried about microsecond accuracy, then NTP can be made reasonably accurate, somewhere around +/- 10ms if yoou use multiple clock sources. See http://www.ijs.si/time/ for more info. A latency measurement tool that might be useful is D-ITG from http://www.grid.unina.it/software/ITG/index.php Jonathon ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
[Vyatta-users] latency tool
I've used D-ITG also, great for simulation of VOIP/SIP traffic. One other tools that has a longer history Mgen/Drec. Just like ITG you will need sync clocks between sender ( mgen ) and receiver ( drec ). Both pkgs allows for creation by src/dst/port/ttl/pps/kbps/etc... Mgen was mainly used for multicast generation hence the name mGen, but it does support unicast flows also. Using udp you can easily obtain one-way latency results. Also you can watch how certain task effect latency. i.e copy tftp flash: on a cisco router will cause the latency to growth on very low end routers ;) or squezze a flash partition: btw, if your very strong in scripting both pkgs are easy to script for automation and controls. Hope this helps. ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
Re: [Vyatta-users] latency tool
Hello Dave, Ken, Jonathon Many many thanks for your answers Very interesting Thanks Troopy -- Original Message -- From: Ken Felix (C) [EMAIL PROTECTED] Date: Thu, 17 Jan 2008 18:24:17 -0500 I've used D-ITG also, great for simulation of VOIP/SIP traffic. One other tools that has a longer history Mgen/Drec. Just like ITG you will need sync clocks between sender ( mgen ) and receiver ( drec ). Both pkgs allows for creation by src/dst/port/ttl/pps/kbps/etc... Mgen was mainly used for multicast generation hence the name mGen, but it does support unicast flows also. Using udp you can easily obtain one-way latency results. Also you can watch how certain task effect latency. i.e copy tftp flash: on a cisco router will cause the latency to growth on very low end routers ;) or squezze a flash partition: btw, if your very strong in scripting both pkgs are easy to script for automation and controls. Hope this helps. __ Désirez vous une adresse éléctronique @suisse.com? Visitez la Suisse virtuelle sur http://www.suisse.com ___ Vyatta-users mailing list Vyatta-users@mailman.vyatta.com http://mailman.vyatta.com/mailman/listinfo/vyatta-users
