[c-nsp] BGP convergence in VRF vs. global routing table on7600router

[Oliver Boehmer (oboehmer)]

Christian Bering <> wrote on Friday, October 19, 2007 2:31 PM:

>> From: Oliver Boehmer (oboehmer) [mailto:oboehmer at cisco.com]
> 
> Hi Oliver,
> 
>> Can you pls describe which "convergence" you are referring? Time it
>> takes after bringing up the session until every other PE has
>> the routes?
>> Or the table version on the CE and the receiving PE is the same?
> 
> Time it takes for PE1's CPU to fall back to normal utilisation and all
> destinations reachable again after PE2 loses an upstream provider.
> 
> Given that PE1 is a "normal" PE terminating customers and PE2 a border
> router-like PE terminating an upstream provider.
> 
>> If you talk about a distant PE receiving the full table from the RR
>> via iBGP, the overhead will likely depend on the RD setup. I assume
>> you use a common RD for the "internet" VRF on all your PEs, right?
> 
> Correct.

Ok. So PE1 will receive many withdraws and/or updates and needs to
change the path from PE3 to PE2? Or will the next-hop stay the same?
With the same RD configured on all the PEs, we don't need to copy the
path while importing, so I guess it boils down to going through the
import policy, updating the routing table and SW/HW forwarding (we will
need to change the label stack we'll push onto the packet). 
 
> And the RRs (7301s) take very little time to converge. After a minute
> or so, the BGP process has fallen to normal levels. The CPUs in
> SUP720s aren't overly fast - I am aware of that.

.. and the RRs don't need to change any routing/forwarding entries, this
is control-plane only.

Did you compare the convergence in a VRF to a convergence in an MPLS
environment in the global table? I.e. did you label-switch the BGP
packets in the global table, or used IP only?

	oli