Thanks, guys! -Simon
On Fri, Jul 11, 2008 at 1:12 AM, <[EMAIL PROTECTED]> wrote: > > Yes, that's standard across all the vendors. One of the things I do to > verify that there is no latency is to ping a destination on the other side > of the router at the same time and compare the latency. If it's something > external to the router the ping times will jump at the same time. If it is > just processor scheduling then only the ping to the router will jump. > > Happy Hunting, > > Keegan > > Mark Kamichoff <[EMAIL PROTECTED]> > Sent by: [EMAIL PROTECTED] > > 07/11/2008 01:07 AM > > To > CHEN Xu <[EMAIL PROTECTED]> > cc > juniper-nsp@puck.nether.net > Subject > Re: [j-nsp] sudden jump in ping response time > > > > > Hi Simon - > > On Thu, Jul 10, 2008 at 02:36:49PM -0400, CHEN Xu wrote: >> I am using multiple logical routers on a juniper router, they are >> connected through logical tunnels, or VLANs, or L2VPN, etc. >> >> When I ping from one logical router to another, I always see some >> glitch in ping response time, like this: >> >> 64 bytes from 1.1.2.1: icmp_seq=153 ttl=64 time=1.015 ms >> 64 bytes from 1.1.2.1: icmp_seq=154 ttl=64 time=1.018 ms >> 64 bytes from 1.1.2.1: icmp_seq=155 ttl=64 time=1.048 ms >> 64 bytes from 1.1.2.1: icmp_seq=156 ttl=64 time=0.988 ms >> 64 bytes from 1.1.2.1: icmp_seq=157 ttl=64 time=36.950 ms <---- >> 64 bytes from 1.1.2.1: icmp_seq=158 ttl=64 time=1.004 ms >> 64 bytes from 1.1.2.1: icmp_seq=159 ttl=64 time=1.005 ms >> 64 bytes from 1.1.2.1: icmp_seq=160 ttl=64 time=1.003 ms >> >> This almost always happens in all setups that I played with. Does >> anyone know what's going on and how to fix it? > > I believe this is par for the course in the JUNOS architecture with any > type of setup. ICMP echo replies (and other ICMP messages) are given > the absolute lowest priority, so anything in the control plane will take > priority. I can see this too on an almost completely idle J2320, via > MTR: > > Host Loss% Snt Last Avg Best Wrst StDev > 1. 2001:4830:122d:7::1 0.0% 6 0.7 0.6 0.5 0.7 0.1 > 2. 2001:4830:122d:19::2 0.0% 6 3.6 103.6 3.2 603.6 244.9 > 3. 2001:4830:122d:c::2 0.0% 6 4.4 6.3 4.3 12.4 3.4 > > The 2nd hop is the J2320. > > The JUNOS Enterprise Routing book discusses this briefly (pages 519-520) > in the CoS chapter, and even shows a PING example demonstrating the > large variance in response times, too. It then goes on to discuss how > RPM can perform the ICMP timestamp reply in hardware (or via the RT > thread on the J-series), for gathering more accurate performance > metrics. Depending on your needs, RPM may be something to consider > testing. > > Hope this helps. > > - Mark > > -- > Mark Kamichoff > [EMAIL PROTECTED] > http://prolixium.com/ > Rensselaer Polytechnic Institute, Class of 2004 > [attachment "signature.asc" deleted by Keegan Holley/SAS/SunGard] > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/juniper-nsp > _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp