Re: [rrg] procedural aggregation

William Herrin <bill@herrin.us> Wed, 12 March 2014 02:59 UTC

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From: William Herrin <bill@herrin.us>
Date: Tue, 11 Mar 2014 22:59:24 -0400
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Subject: Re: [rrg] procedural aggregation
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Hi Folks,

Here's another circumstance worth mentioning. This particular one is
an undesirable case that exists in BGP today. It would be better if it
didn't work. When I get to procedural aggregation, it'll be important
to consider whether my notions make this scenario worse.

You have three networks: A, B and C. A peers with B, B peers with C.

A-B-C

You have a customer, W. W buys transit service from A (gige) and B (T1).

A-B-C
| /
W

W announces 10.1.2.0/23 to B and announces 10.1.2.0/24 plus 10.1.3.0/24 to A.

Because W is a customer, B announces 10.1.2.0/23 to C but as soon as
the packet arrives at B from C, B sends it to A because of the more
specific route it heard from A.

This allows W to draw a gige of traffic through B even though he's
only paying for a T1.

Regards,
Bill Herrin


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William D. Herrin ................ herrin@dirtside.com  bill@herrin.us
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