[j-nsp] iBGP convergence time

[Pekka Savola]

On Fri, 2 Feb 2007, Richard A Steenbergen wrote:
> On Thu, Feb 01, 2007 at 09:07:05AM +0100, Gniewko wrote:
>> It takes about 3 minutes for m7i_2 to receive 200k of prefixes. But, as
>> soon as I change AS to my public number (both sides of course) have to
>> wait almost 20 minutes. During this long period, CPU on m7i_2 is quite
>> busy.
>> Could You please give me a hint what could be the source of this
>> behaviour?
>
> You know I haven't had any free time to run real tests or anything, but I
> noticed a significant increase in BGP convergence time when upgrading from
> JUNOS 7.2/7.3 (and I think some 7.4) to 7.6. When you make a policy
> change, the routes take several minutes (from 2 to 7) to install. If you
> do a show route you can see the new routes sitting in + and the old routes
> sitting in - for minutes, RPD is spinning its heels at 100% cpu, and the
> packets continue to forward over the old path while it is processing.
...
> scientific testing all the new code seems to be significantly slower. At
> first I had blames this on a particularly nasty build of 7.6 with other
> bugs, but the other day I upgraded a similarly loaded box to 8.1 and
> noticed the same issues. Anyone else seeing the same thing? Short of
> someone slipping in some for(;;) screw_customer(); code to motivate RE
> upgrades I can't explain it. :)

A week or so ago I noticed something similar on 7.5SR, on T320 
router(s).  The routes were also sitting in "+" in the order of 3-5 
minutes for 200K routes (inbound eBGP + 5 iBGP peers).  I recall that 
earlier similar changes have been almost instantaneous.

I didn't look at the CPU usage level then.  In RRD graphs there is a 
CPU spike, but it might well be from during the actual route 
processing and advertising as well.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings