[quagga-dev 5968] route cache and slow convergence time on linux
fdolcini at sysnetsistemi.it
Fri Sep 26 16:50:18 BST 2008
I am running ospfd/quagga 0.99.10 on linux (custom embedded 2.4.20x, but
I think 2.6 would be the same) and doing some preliminary analysis on
network convergence time.
My current test network is a 4 router loop
Multipath routing is on, with --enable-multipath=4.
When I break the link between R4 and R1, the time to recover the
comunication from H1 to R2 is a little more then 3 seconds (measured
using a ping -i 0.1), 1 second is the minimum I can achieve to detect
the link failure (ip ospf dead-interval minimal ..., link-detect is
slower for my specific network interfaces), the other 2 second seems
related to the default value of /proc/sys/net/ipv4/route/min_delay
(minimum delay before the route cache is updated or flushed), setting
this to zero seems to solve this slow convergence issue.
Now the questions:
- Is there any known issue setting this value to zero? the only
reference I found is this thread on LKML:
- Is it possible to achieve sub 2 seconds convergence time using linux
and quagga/ospf apart from modifying the min_delay? I am sure that I am
not the first person that try to have this kind of performance ...
I don't think that multipath routing is causing the issue but I can test
without it, of course.
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