[c-nsp] MPLS Load balancing Question

[Oliver Boehmer (oboehmer)]

Novice <mailto:vkasturi at gmail.com> wrote on Thursday, June 15, 2006
12:28 PM:

> Hi Oliver,
> 
> Thanks for your reply. Have 2 questions:
> 
>> 1.If you need symmetry, you can advertise the prefixes differently
>> into the vpnv4 clouds so remote PE's/RR prefer one over the other
>> (different med, local-pref, etc.).  
> 
> When u say this u mean we can have route-maps on the remote PE and
> have the incoming Local pref modified. With this we would need to
> mention the list of prefixes for which PE1 is preferred and
> prefixes with PE2 preference correct. If we use MED then do the
> same with route-maps on PE1 and PE2. Is my understanding correct ?

Yes, using MED or localpref..

>> 2. Asymmetric traffic should not be a major issue unless you run some
>> stateful firewalls close to CE1 and CE2.  
> With rgds to this wont
> the packet re-ordering and seq be an issue if there is some
> congestion in network at some stage. There are no firewalls.  

asymmetry and packet re-ordering are two different things. Asymmetry is
common in many networks and usually doesn't cause problems (except for
firewall and things), it doesn't matter if the return packets take a
msec or two longer to arrive than the packets in the other direction.
Re-ordering must be avoided wherever possible, but you are dealing with
this on a unidirectional basis, so all session from src -> dest must
take the same path to deliver it in sequence.

	oli