Multi-homed implementation and BGP convergence time

Seth Mattinen sethm at
Sat Sep 12 01:59:15 UTC 2009

Kevin Loch wrote:
> Seth Mattinen wrote:
>> Jay Hennigan wrote:
>>> "Tier 1", "tier 2" etc. are terms used primarily by salespeople, and
>>> don't have a lot to do with technical matters.
>> Sure it does. If you're multihoming it will increase your AS path length.
> There is no general correlation between AS path length and whether
> or not a network pays to exchange traffic.

That has nothing to do with what I was trying to say. When one mixes
shorter/longer paths, you will generally see most of your traffic come
in via the shorter path.

It's like if I were to multihome with the local cable co (who has Level3
as an upstream) with a connection to Level3 myself. It's not likely that
traffic inbound to me is going to choose the longer route unless the
shorter one is down, and it's pointless as a backup because a regional
outage affecting Level3 may kill the cable co's link to them as well.


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