[clue-tech] multihomed ISP and BGP

[Jim Ockers]

Hi CLUEbies,

I need a BGP clue I think.  Please considier the following quote regarding
a multihomed ISP:

"$ISP says that they have no preferred provider.  They say they are running 
BGP, but they don't use weighted preferential routing system, and have no 
plans to introduce one."

Is this the correct approach?  My concern is that if $ISP advertises their
IP addresses via BGP on backbones A B and C, how would a different network
(who is also peered with A B and C) choose which backbone to transit the
traffic through?

In particular I don't think I like asymmetric links, where the traffic goes
one way them->$ISP->A->$OURISP->us but the other way is us->$OURISP->B->$ISP->them.
Especially if B is a crappy network, which it might or might not be, I
have no way of knowing.  If the traffic came & went over backbone A then at
least we could get consistent round trip transit times, maybe.

Questions for the group:

1. Am I justified in preferring symmetric links over asymmetric links?  Why or
why not?

2. Is $ISP justified in not having any weighted preferential networking on
any of their connections?  Why or why not?

3. Is there any way to force symmetric links between two IP addresses that
are connected via multiple backbones?  Or is this just not possible?

I expect Nate might have an idea but I know there are lots of smart people
on this list including a ton of lurkers.  So, thanks a lot in advance for
the advice.

Jim

PS I miss having InterNAP service.  Wasn't my decision to terminate it.

-- 
Jim Ockers, P.Eng. (ockers at ockers.net)
Contact info: please see http://www.ockers.net/