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RE: Policy Routing

  • From: Przemyslaw Karwasiecki
  • Date: Sun Aug 26 01:35:21 2001


First: I agree with you at your main point 110% so my other
       comment is strictly technical in nature.

Second: Correct me if I am wrong, but I believe that if you send
        to company X full view over EBGP there is no technical
        reason to forward packets over different AS path.
        After all, you are advertising reachability via NEXT_HOP,
        which will be your border router.

Before you flame me, please let me reiterate that I agree with you
on the main point, that making a false/misleading AS_PATH advertisements
is bad. But I am just curious if it would work provided that you are
able to forward packets based on some 'coloring' scheme,
so please consider my comment more as a question then questioning :-)



-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of
John Fraizer
Sent: Sunday, August 26, 2001 12:57 AM
To: Jeff Cates
Cc: [email protected]
Subject: Re: Policy Routing

Replying to my own post with a bit more. (Forgive me!)

Rereading your post, one would believe that since "Company X" is a BGP
customer of yours, you're going to be sending them a full view.  Unless
there is a knob that I'm not familiar with, that means that you're going
to be sending them the _BEST_ routes that you see in your core and not
just those from "NSP A" to which you are proposing to policy-route all of
"Customer X's" traffic.  If this is indeed the case, I would think that
policy-routing the customers traffic destined for "prefix Y" via a
path other than the path listed in the NLRI you're sending "Customer X" on
their BGP feed is outright fraud.

Again, this is in the absence of full disclosure and it is my (non
esquire) opinion.

John Fraizer
EnterZone, Inc

On Sun, 26 Aug 2001, John Fraizer wrote:

> I would be very upset if I were "Company X" and I found out that you were
> policy-routing my traffic to the "cheap" connection vs the best
> connection.
> Is it just me or do others on the list believe that in the absence of full
> disclosure this would be shady at best?
> ---
> John Fraizer
> EnterZone, Inc
> On Sat, 25 Aug 2001, Jeff Cates wrote:
> >
> > Hello,
> >
> > I am a network engineer at a regional southeast USA
> > NSP. I am looking for some recommendations concerning
> > a scenario that has been presented to me.
> >
> > My company is attempting to obtain company X's
> > Internet transit traffic, which will be  BGP-4 peering
> > over either a T-3 or OC-3. Due to financial reasons,
> > my upper management has proposed that I route company
> > X's Internet traffic via a specific NSP that we peer
> > with, we'll call them NSP-A. Apparently, NSP-A has a
> > substantially cheaper rate than our other upstrem
> > providers and it is anticipated that this customer
> > will be sending a full T3 or OC-3's worth of traffic
> > to us.
> >
> > Redirecting inbound traffic to company X via NSP-A can
> > be accomplished very easily through use of AS path
> > prepending, however, coming up with a solution for
> > egress traffic from company X to NSP-A, via our AS,
> > has proven a bit more challenging :-).
> >
> > The only feasible solution that I've been able to come
> > up with is to stick customer X directly on the router
> > that peers with NSP-A and employ the use of policy
> > routing, which would enable me to set the next hop for
> > company X's traffic to the peering address on NSP-A.
> >
> > Our NSP-A peering router is a Cisco 12016, running IOS
> > 12.0(16)S2 and it has 256MB of DRAM.
> >
> > Additionally, it is configured with NetFlow and dCEF
> > switching.
> >
> > I've never employed policy routing in this type of
> > environment and I am concerned about the overhead that
> > it might place on the router or on the traffic
> > traversing the interface.
> >
> > I've also thought about MPLS TE, however, our core
> > backbone does not run MPLS and even if we did, I
> > believe I would still have to policy route the traffic
> > to NSP-A once the MPLS label was popped off the last
> > router in the path in transit to the NSP-A peering
> > router.
> >
> > Any ideas or comments would be greatly appreciated.
> >
> > Thanks in advance,
> >
> > Jeff
> >
> > [email protected]
> >
> >
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> >