[j-nsp] load balancing between juniper routers for unequalcostpath

[Chris Kawchuk]

Hi Paul,

Agreed, however, with the load-balancing export mentioned earlier, JunOS
does per-flow balancing, hence, any particular session (such as a VoIP
call and a stream of UDP packets) will always use the same path; thus
they will still arrive in the same order at the destination router. =)

Different TCP or UDP sessions will indeed have ordering problems,
assuming you are trying to co-ordinate multiple "flows" for the same set
of services on different port numbers. However, each individual
TCP-connection and/or UDP flow will indeed take the same path by the
hashing algorithm. 

Good catch.!

- Chris.

 

-----Original Message-----
From: Paul Goyette 
Sent: Friday, November 09, 2007 11:29 AM
To: Chris Kawchuk; 'Hamid Ahmed'; 'Andy Lamontagne'
Cc: 'juniper-nsp'
Subject: RE: [j-nsp] load balancing between juniper routers for
unequalcostpath

> As both Chuck and Leigh have stated, you CAN use GRE tunnels to do 
> this, however, you will run into MTU size issues by doing this. You 
> will also need tunneling/Adaptive Services/MultiServices PICs (or ASM 
> cards if it's an M7i were dealing with) to do gre tunneling.
> 
> The far "cleaner" way here is to follow Andy's suggestions and build 2

> x RSVP signalled LSPs with strict routing options
> (EROs) so that they take different paths across your network, but 
> appear to be the same metric to OSPF, hence, they will load balance.

If the metrics reflect true costs and latency, then this could easily
result in packet sequencing problems.  The specific set of packets which
would experience problems will depend on what how set the load-balancing
hash-key fields.

Just pointing this out in case you care...  :)