Re: [Idr] Vendor Defaults (was Re: Review of draft-ietf-large-community-06.txt)

"Jakob Heitz (jheitz)" <jheitz@cisco.com> Sun, 06 November 2016 23:25 UTC

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From: "Jakob Heitz (jheitz)" <jheitz@cisco.com>
To: "idr@ietf.org" <idr@ietf.org>
Thread-Topic: [Idr] Vendor Defaults (was Re: Review of draft-ietf-large-community-06.txt)
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Date: Sun, 6 Nov 2016 23:25:27 +0000
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Subject: Re: [Idr] Vendor Defaults (was Re: Review of draft-ietf-large-community-06.txt)
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The question:
Should Large Communities be transmitted across EBGP by default?

Note: there is a knob to change the default, so the discussion is how to act with the knob unconfigured.

Arguments to block:
1. Principle of least surprise: Do same as 1997.
2. Accidental leakage of internally used communities will cause unintended routing.

Arguments to pass:
1. Legacy code will pass it, because the attribute is transitive. Upgrade to LC aware code should do the same by default.
2. It is convenient to pass a community through your first level transit to fix a problem further upstream. A default block frustrates this effort.

The problem of accidental leakage is greater with 1997 communities, because many ISPs use private ASNs. This is as problem if a community intended for a distant ISP is interpreted by a near ISP when they use the same private ASN. This problem SHOULD disappear with Large Communities, because the need to use private ASNs no longer exists.

I would like to hear other arguments and gauge support for each case.

Thanks,
Jakob.