[nsp] BGP tweaking possibility

[Tony Tauber]

On Wed, 16 Jul 2003, Gerald wrote:

> > Very true.  There's no mechanism to cut traffic up by volume.  The
> > best you'll be able to do is trial and error unless you get into
> > some kinky netflow stuff.  Even then, you're making a config based
> > on some statistics, not causing the router to make a decision
> > based on load.
>
> That's kind of the automated version of what we are currently doing.
> MRTG + modifying route prefs & prepends.

Just to clarify, what I was talking about was not automated.
It's possible with Netflow to pull out info about traffic flows
broken down by AS number.  You still have to decide what config might
get you what you want through local-pref and prepends to pack the
traffic "chunks" to achieve the desired effect.

> > You might do better to take both transit and non-transit routes
> > and depreference the transit ones so they're only used in case of
> > a failure of the preferred path.
>
> My understanding of that is if one of the ISP's changes their
> network slightly after I put that in place, that could throw off my
> fine tuning.  I'm hoping to make it an internal router decision
> based on bandwidth.

That's right.  I don't know of a way on Cisco (which is not to say
there isn't one) to make a decision based on bandwidth.

> I've had 2 good suggestions off list so far. One is a commercial
> solution (ick) ...and the other I don't fully understand yet so I
> have to go do more Cisco reading. The recurring cisco wording from
> the other suggestion on and off list is to use "Policies" to do what
> I want. /me grabs Cisco dictionaries/URLs to read up on what
> policies will do.

My understanding of the RouteScience and Sockeye boxes is that they
can affect the traffic outbound from you to your provider(s) by
adjusting the routes they hear on the basis of some criteria and
perhaps bandwidth is one of them.  If the other suggestion is BGP
policy propagation, from the use I'm familiar with, it doesn't do what
you want.

> Anyone actually done this that could e-mail me off or on list?
>
> > You could act on the communities on routes that you're hearing
> > from others, which would affect outbound traffic.  Some providers
> > will act on communities you send to them in order to change the
> > preference of a route relatively up or down somewhat which will
> > affect inbound traffic.
>
> Like AS-Prepends? Already doing that and not getting the results I
> want yet.

Right, but instead of you prepending all the advertisements, they can
prepend to selected providers to give more granular control.

Tony