[j-nsp] Strange latency when using traceroute. (Alex Campbell)

[BRIANT Alain]

Hi Stefen

If the J6350 is the only J series router you have in your network and the other ones are M series
or other vendors' then the problem is just regarding the way a Jseries (J2300, J4300, J6300, J4350, J6350) treats the ICMP packets.

I have already seen some low response time as well as variations in the answers directed to ip addresses owned by the Jserie router.
This is because the distribution of the routing process and the forwarding process owned by the same CPU (done on two different CPU on the M series).
Juniper has implemented this in the Jseries with very low priority to icmp answers directed to the router itself.
In fact you can see that the transit pings are forwaded very fast!

I also believe that this behavior can have been changed in the different releases.

regards
Alain



Message: 2
Date: Sun, 01 Jul 2007 01:05:11 -0400
From: Stephen Fulton <sf at lists.esoteric.ca>
Subject: [j-nsp] Strange latency when using traceroute.
To: juniper-nsp at puck.nether.net
Message-ID: <46873607.5050803 at lists.esoteric.ca>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi all,

I've noticed that when traceroute passes through our J6350 (using 
8.3R15), that the returned latency is considerably higher from the 
router.  Pinging the router or devices past it are fine, but this is one 
of those things I know I'll be asked about, and I haven't been able to 
figure out.  Here's the redacted output from a sample traceroute:

[sfulton at optics ~]$ traceroute 192.168.254.2
traceroute to 192.168.254.2 (192.168.254.2), 64 hops max, 40 byte packets
  1  router1 (192.168.110.74)  0.337 ms  0.143 ms  0.494 ms
  2  j6350 (192.168.98.65)  25.119 ms  28.051 ms  29.982 ms
  3  router3 (192.168.254.2)  1.079 ms  0.743 ms  0.962 ms
[sfulton at optics ~]$

Now there are filters protecting the routing engine, but I've removed 
all others for the purpose of testing.  CPU load is practically zero, 
and the J6350 is running OSPF and BGP.

Any ideas?

-- Stephen.