Re: [Idr] Mirja Kühlewind's No Objection on draft-ietf-idr-bgp-extended-messages-33: (with COMMENT)

"Susan Hares" <shares@ndzh.com> Wed, 31 July 2019 15:27 UTC

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From: Susan Hares <shares@ndzh.com>
To: 'Alvaro Retana' <aretana.ietf@gmail.com>, 'Mirja Kühlewind' <ietf@kuehlewind.net>, 'The IESG' <iesg@ietf.org>
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Date: Wed, 31 Jul 2019 11:27:48 -0400
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Subject: Re: [Idr] Mirja Kühlewind's No Objection on draft-ietf-idr-bgp-extended-messages-33: (with COMMENT)
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Alvaro and Randy: 

 

Thank you for starting this message thread this week.   As a professor, I’m in the midst of grading – so I’m online this week. 

 

The BGP peer receiving the message generates a  NOTIFICATION with a  Message Header Error and a subcode of “Bad message length”  (page 21, p. 30).  Please note the difference in the language.    This language tags the event directly to Event 21: BGPHeaderErr in the BGP FSM (p. 48).  
 

 

Text must be: 

New/

   If a BGP message with a Length greater than 4,096 octets is received

   by a BGP listener who has not advertised the Extended Message

   Capability, the listener will generate a NOTIFICATION with the Message Header error 

   and an Error subcode set to Bad Message Length ([RFC4271], Section 6.1).

/

 

Otherwise, it does not keep the consistency with the BGP FSM. 

 

Sue 

 

 

From: Alvaro Retana [mailto:aretana.ietf@gmail.com] 
Sent: Tuesday, July 30, 2019 3:01 PM
To: Susan Hares; Mirja Kühlewind; The IESG
Cc: idr-chairs@ietf.org; draft-ietf-idr-bgp-extended-messages@ietf.org; idr@ietf.org
Subject: RE: [Idr] Mirja Kühlewind's No Objection on draft-ietf-idr-bgp-extended-messages-33: (with COMMENT)

 

On July 30, 2019 at 12:22:13 PM, Susan Hares (shares@ndzh.com) wrote:

 

Sue:

 

Hi!

 

On #2, the Discussion from the WG (over long period of time) suggested that this exact statement was not clearly stated in RFC4271.   

 

This is the text that Mirja highlighted:

 

   If a BGP message with a Length greater than 4,096 octets is received

   by a BGP listener who has not advertised the Extended Message

   Capability, the listener MUST treat this as a malformed message, and

   MUST generate a NOTIFICATION with the Error Subcode set to Bad

   Message Length (see [RFC4271] Sec 6.1).

 

First of all, if a BGP router doesn't support Extended Messages it means it doesn't support this document...so we can't Normatively tell them what to do.

 

rfc4271/§6.1 (Message Header Error Handling) specifies what to do if, among other things, the length is greater than 4096...so that would be what the speaker who doesn't support this document would do.

 

NEW>

   If a BGP message with a Length greater than 4,096 octets is received

   by a BGP listener who has not advertised the Extended Message

   Capability, the listener will generate a NOTIFICATION with the Error 

   Subcode set to Bad Message Length ([RFC4271], Section 6.1).

 

 

Thanks!

 

Alvaro.