Re: [Idr] [GROW] Question about BGP Large Communities

Alvaro Retana <> Tue, 04 February 2020 19:09 UTC

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From: Alvaro Retana <>
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Date: Tue, 04 Feb 2020 11:09:01 -0800
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To: "Sriram, Kotikalapudi (Fed)" <>
Cc: "" <>, "" <>, "Jakob Heitz (jheitz)" <>, "" <>, John Heasly <>, "" <>, Job Snijders <>, Nick Hilliard <>
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Subject: Re: [Idr] [GROW] Question about BGP Large Communities
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On February 4, 2020 at 1:22:11 PM, Sriram, Kotikalapudi (Fed) wrote:

[Speaking as a WG participant.]



> Question:
> Can the draft simply make an IANA request for
> a Global Administrator ASN value for Route Leaks Protection (RLP) type
> and request that it be published in IANA registry
> as a "well-known Transitive Large Community"?


There is no IANA registry for Global Administrator because it is
simply a "four-octet namespace identifier...SHOULD be an ASN"
[rfc8092], but it doesn't have to be.

Skimming through draft-ietf-grow-route-leak-detection-mitigation, I
would say (personal opinion) that you have two options:

(1) Describe the Local Data Parts so that they are well-known when
used by any ASN (Global Administrator).  This has the disadvantage
that the values may collide with existing policies (?).

(2) Request IANA to assign an ASN for this application.  Take a look
at rfc7249/§2.1, which talks about the allocation of special-purpose
AS Numbers.  The advantage is obviously that collisions can be
avoided, but it seems to me that it may be too much (an ASN) for just
this application.

So...if an ASN is requested, it would be independent of Large Communities.

> it appears it is *assumed* that the Large Communities are transitive.

rfc8092 "defines the BGP Large Communities attribute as an optional
transitive path attribute".