RE: [PWE3] Proposed new 5.4.3 for arch draft

[neil.2.harrison at bt.com]

Stewart Bryant wrote 03 March 2004 04:34
> Thomas D. Nadeau wrote:
> 
> > 	Stewart,  you are aware that IP
> > employs ECMP as well, yes?  
> 
> Of course.
> 
> > Seems more
> > generic to just mention ECMP instead of
> > MPLS, or mention MPLS as an example.
> 
> But this is an MPLS specific problem we are addressing.
NH=> Don't want to labour this one but.....if you think about what you are saying here Stewart, this is yet another example of why MPLS is not the same as IP.
> 
> ECMP in an IP network works just fine (provided you
> ECMP per flow and not per packet).
NH=> I agree with Stewart here.  Load balancing is fine within a single layer network (any)....I believe its called TE ;-).  The problems occur when folks try and load balance over nested layered networks.  So if you start peeking inside the payload area of *any* layer network (I could apply this to SDH or OTNs in principle) to see what the clients are then you can expect problems.  This another consequence of mp2p LDP due to this just doing SPF routing.  Even our IP design teams wish ECMP did not exist in MPLS (esp when one considers all the fault-management problems it creates too).

As an aside, I think we ought to be looking for solutions that don't promulgate past errors of judgement....if we can find any of course.

regards, Neil
<snipped>

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