North American Network Operators Group
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Re: Can you explain why paths to same host diverge?

  • From: dorian
  • Date: Sat Feb 28 00:30:15 1998 
On Fri, Feb 27, 1998 at 08:52:08PM -0800, Mark Boolootian wrote:
> You ask:
> >I feel obligated to ask -- is there some reason you didn't
> >direct your query to Sprint, before asking NANOG? It really seems like
> >this is the kind of question they should be able to answer for you,
> >and diagnose the problem to some extent. I can't see a good reason to ask
> >here without asking the providers in question, first.
> 
> There were really two reasons I asked this question here.  First, it 
> seemed like an interesting operational issue that I hadn't ever seen
> beaten to death on NANOG.  Everyone is used to asymmetry between forward
> and reverse paths, but I don't think I'd ever seen a case of asymmetry
> in the forward path (at least, not while the network was stable).  Second,

Actually, this is alot more common than you'd think. Because of the lead
time in getting OC-Nc circuits installed (where N is whatever greater
than your carrier/transmissions folks are used to delivering) and
the difficulty in getting them, alots of folks put in multiple parallel
DS3s and such to tide them over.

To use such links effectively, many folks are turning to source/dest
hashing load balancing in DCEF.

-dorian