consistent policy != consistent announcements
djls at gate.net
Thu Mar 13 20:55:05 UTC 1997
Consider the case where a customer has two AS numbers and uses one
for his East Coast operations and one for his West Coast operations.
Since he only purchases transit, he can use his Internet connections to
back up his coast-to-coast link, which he normally prefers. Suppose he has
connections to a particular backbone on both coasts and wishes nearest
exit to be used.
At MAE-E, this backbone will prefer the East Coast AS to reach
his IPs. At MAE-W, this backbone will prefer the West Caost AS to reach
his IPs. The BGP advertisements this backbone will make to its peers will
be 'inconsistent' but also 'optimal'.
On Thu, 13 Mar 1997, Henry Kilmer wrote:
> Vince Fuller writes:
> >I can see why you present inconsistant routes to us but I'm not sure that I
> >understand why you'd prefer a customer prefix via a direct connection to them
> >at one point in your network but via a connection to another provider at a
> >different point in your network. That would seem internally inconsistant to
> >me. Is this deliberate behavior to do shortest-exit within your network toward
> >your customer?
> We have some customers that have specifically requested this sort of arrangement.
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