Customers announcing communities to SP of SP

Theodore Baschak theodore at
Mon Sep 19 20:28:50 UTC 2016

In a previous $dayjob at a different ASN I was customers of a large-ish
regional Canadian carrier (at 100M), and also of a small local guy (at 8M)
with only Cogent upstream. I would prepend out the local guy 3x, and then I
also tagged 174:3003 to have cogent prepend 3x more. This worked somewhat
OK to make up for the inbalance in speeds.

This type of use case is supported by, and works well with
draft-heitz-idr-large-community. As an operator of a 32-bit ASN I have no
ability to use communities with my ASN in them like 16-bit ASN operator
could, and I have expressed so on the IETF IDR list.

Theodore Baschak - AS395089 - Hextet Systems -

On Mon, Sep 19, 2016 at 11:00 AM, Jason Lixfeld <jason+nanog at>

> Hi,
> Consider the following scenario:
> - Customer A is a customer of SP A
> - SP A is a customer of SP B
> - SP B has a traffic engineering community implementation
> With regards to using BGP communities for TE:
> - Does SP A write their own community implementation that maps to (some
> portion of) the community implementation of SP B?
> - Does SP A write their own community implementation that has no mappings
> at all to the community implementation of SP B; any TE that is required to
> be pushed to SP B is done by some dialog and coordination between Customer
> A and SP A?
> - Does SP A allow Customer A to announce prefixes tagged with SP B’s
> communities[1][2]
> - Is this sort of thing really complicated today, but one of the goals of
> draft-heitz-idr-large-community?
> [1] Customer A has knowledge of SP A’s upstream SP B
> [2] This opens up a can of worms where SP A or SP B implements some
> communities prefixed with reserved ASes, so we’ll assume that SP A
> implements some method of allowing communities prefixed with ASes of SP A
> and SP B only.
> Thanks!

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