Re: [Idr] draft-ietf-idr-ext-opt-param-06.txt - 2 Week WG LC (7/30 to 8/13/2019)

"Susan Hares" <> Wed, 31 July 2019 17:15 UTC

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From: Susan Hares <>
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Date: Wed, 31 Jul 2019 13:14:58 -0400
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Subject: Re: [Idr] draft-ietf-idr-ext-opt-param-06.txt - 2 Week WG LC (7/30 to 8/13/2019)
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Thank you for your normal detailed review.    I will let John and Enke
respond to you first before I comment. 




From: [] 
Sent: Wednesday, July 31, 2019 5:18 AM
To: Susan Hares;
Subject: RE: [Idr] draft-ietf-idr-ext-opt-param-06.txt - 2 Week WG LC (7/30
to 8/13/2019)


Hi Sue,


Fully support.

I'm also fine with the _current_ version of the document.


Nevertheless, I'll try some comments, possibly useless but at minimum to
show to the shepherd/AD that I've read and reviewed the doc. 


1.  Introduction


The Parameter Length field of individual Optional Parameters is similarly


I would rather remove 'similarly' or change it to 'also'. As although the
technical specification is crystal clear, I fear that the sentence could be
interpreted as the length field for individual optional parameters been
extended the same way (length 255, followed by extended length) while this
is not the case.



The (non-extended) length field is set to
   255, as is the subsequent octet that in the non-extended format would
   be the first Optional Parameter Type.  The subsequent two octets
   carry the actual length. 


This works so let it be so.

One could have argued that this encoding is borderline as per RFC 4271. May
be an encoding  more in line with 4271 could have been Type: 255, Length: 2,
Value: actual/extended length. (i.e. adding/keeping the 'length' field of
the Optional Parameter type 255). That would also have been more friendly
for protocol parser (e.g. wireshark) especially since there is a chance that
network operator get surprised the first time that the BGP session get
rejected and may want to have a look at the open message).

Note that I understand that my comment is way too late . and also a matter
of opinion.


   In the event that the length of Optional Parameters in the BGP OPEN
   message does not exceed 255, the encodings of the base BGP
   specification [ <> RFC4271] MUST be
used without alteration.


Could the document define the error handling if this MUST is not followed? I
believe any option (notification or silently ignore) works, but in general I
have a preference for error handling to be covered by the spec.

That may also be the opportunity to remove the following sentence "If the
value of this field is zero, no Optional Parameters are present (this would
never be expected to happen with the extended encoding, however). > which is
both not general enough (does not cover length 1-254) and appears in the
general specification/behavior while it's about error handling.


As of 2019, I feel that this extension may have been an opportunity to also
enable the use of BGP extended message length for the BGP OPEN message. (if
the "BGP Extended Message" capability was also exchanged.). Alternatively,
the burden of defining this could also been in
draft-ietf-idr-bgp-extended-messages. But probably too late for both
documents so let's move forward.







From: Idr [] On Behalf Of Susan Hares
Sent: Tuesday, July 30, 2019 6:06 PM
Subject: [Idr] draft-ietf-idr-ext-opt-param-06.txt - 2 Week WG LC (7/30 to


This begins a 2 week working group last call on
draft-ietf-idr-ext-opt-param-06.txt from 7/30 to 8/13/2019.  


You can access the draft at:


John and Enke - I am counting on you gather information on the 2
implementations and post this on the IDR Wiki during these 2 weeks. 


For the WG, consider if:


1)      The technology is ready for publication or if there are flaws that
prevent its publication, 

2)      Is this technology useful to BGP deployments? 

3)      Are there any minor editorial errors the authors should address
before publication. 



Cheerily, Sue Hares 




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