Re: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages

"Enke Chen (enkechen)" <enkechen@cisco.com> Wed, 31 July 2019 21:50 UTC

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From: "Enke Chen (enkechen)" <enkechen@cisco.com>
To: Jeffrey Haas <jhaas@pfrc.org>, Alvaro Retana <aretana.ietf@gmail.com>
CC: "idr@ietf. org" <idr@ietf.org>, "draft-ietf-idr-bgp-extended-messages@ietf.org" <draft-ietf-idr-bgp-extended-messages@ietf.org>, Susan Hares <shares@ndzh.com>, "idr-chairs@ietf.org" <idr-chairs@ietf.org>, "Enke Chen (enkechen)" <enkechen@cisco.com>
Thread-Topic: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages
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Date: Wed, 31 Jul 2019 21:50:08 +0000
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References: <CAMMESsyvuU8_dBOeoOXPBt=-HwoF0eHvYgm5d8CgF-4o_oiP=g@mail.gmail.com> <20190731211602.GA31271@pfrc.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/idr/hypTmrddc3DhMduj-U8kQnEScDA>
Subject: Re: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages
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Hi, Jeff:

>>  Note that RFC 6793 (4-byte ASes) require bi-directional advertisement.

No, this statement is not correct. It is fundamental (in transition) for a BGP  speaker
to be able to talk to both NEW speakers (that have advertised the capability), and OLD
speakers (that have not advertised the capability).  Different encodings are used in the
UPDATE message depending on whether the 4-byte AS capability is received from a
neighbor.

Thanks.  -- Enke

-----Original Message-----
From: Idr <idr-bounces@ietf.org>; on behalf of Jeffrey Haas <jhaas@pfrc.org>;
Date: Wednesday, July 31, 2019 at 2:16 PM
To: Alvaro Retana <aretana.ietf@gmail.com>;
Cc: "idr@ietf. org" <idr@ietf.org>;, "draft-ietf-idr-bgp-extended-messages@ietf.org"; <draft-ietf-idr-bgp-extended-messages@ietf.org>;, Susan Hares <shares@ndzh.com>;, "idr-chairs@ietf.org"; <idr-chairs@ietf.org>;
Subject: Re: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages

    On Wed, Jul 31, 2019 at 01:06:04PM -0700, Alvaro Retana wrote:
    > During the IESG Evaluation, Sue pointed out that we removed the piece of
    > text below:
    > 
    > Just to let you know that the text below:
    > 
    > “A peer which does not advertise this capability MUST NOT send BGP
    >    Extended Messages, and BGP Extended Messages MUST NOT be sent to it.”
    > 
    > was added due to comments on the IDR WG list from reviewers and operators.
    > 
    > Given that Extended Messages is a very important extension to BGP, and even
    > though I didn’t see objections in the thread mentioned above, I want to
    > confirm one more time that the current text is ok with the WG. 
    
    I am fine with the current text, although my opinion is nuanced.
    
    By requiring bi-directional advertisement of the capability, UPDATEs sent
    from one can have NOTIFICATIONs of similar size.  This avoids some ugly edge
    conditions that would result from uni-directional advertisement of the
    capability.
    
    The converse argument, which I'm not supporting, is that uni-directional
    advertisement intentionally lets peers opt-out of receiving extended
    messages, even it understands them.
    
    Let the bi-directional requirement stand.
    
    Note that RFC 6793 (4-byte ASes) require bi-directional advertisement.
    
    -- Jeff
    
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