Re:[isp-bgp] TE practices when peered to two big upstreams?

["Lloyd, Michael \(Mike\)" <drmike@...>]

Fair warning: I'm a vendor, but I will try to answer the questions as
asked, not pitch.

> From: joshua sahala <jejs+bgp@...>
[...] 
> the question that i 
> have is why do people want to see a totally even (or as close to it as

> possible) distribution of traffic on their links,

Well, I can say that in the last 5 years of making route optimizers,
I've seldom seen that as a request.  It does come up on rare occasions,
but usually when someone has very limited capacity (eg: a pair of T1's),
and they want an even balance because it minimizes the possibility that
any link will flat-top with a sudden change in load.  For most BGP
users, this isn't necessary because they can afford enough burstable
capacity for any surges that may come along.

> in my network, i like stability and predictability...'routing magic'
> boxen tend to make things much less stable and predictable (but then 
> the traffic graphs have a nice flat-line)

Even distributions are rare, as I say, but there are a fair number of
users of route optimization who want flat lines.  Specifically, they
want to see a flat line on a link when it reaches a 95th %ile billing
threshold, and then send any excess load someplace else, because it
saves money to do so.  Clearly, this is hard-to-impossible to achieve
manually, but it's something an automatic system can do.  Whether it
should be done I'm happy to leave as a matter of opinion.

Mike Lloyd
ex-CTO, RouteScience (now part of Avaya)





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