Re: [Idr] WG Last Call on Extened Message Support

[<[e-mail]>]

Randy,

Thank you for the update.
-29 looks go to me but I still have the following comments:

§4

"treat as withdraw' (see [RFC7606]) a BGP attribue/NLRI pair which is too large to be sent to a peer which does not support BGP Extended Messages.

It's not clear to me whether the specification means sending the withdraw on all BGP sessions or only on the BGP sessions which do not support BGP Extended Message.
I can live with both choices but have a preference for the latter. I'd like the behavior be clarified in the specification.
In my understanding:
- For this draft, sending the withdraw only on the sessions not supporting BGP Extended Message would be enough, and would avoid disruption if someone enable a new BGP session not supporting BGP Extended Message
- RFC7606 is dealing with BGP update being received, hence does a withdrawn on all BGP sessions (including in the Loc-RIB of the speaker)

Hence there is a possible mismatch that people could try to interpret resulting in different behaviors.

-----
§6
OLD:
 For all messages except the OPEN
   message, if the receiver has advertised the capability to receive
   Extended Messages, this document raises that limit to 65535.

NEW:
 For all messages except the OPEN
   message, if the receiver has sent and advertised the BGP Extended Message Capability, this document raises that limit to 65535.
---
§3
OLD: A BGP speaker
   MAY send Extended Messages to its peer only if it has fully exchanged
   the Extended Message Capability with that peer.
   
   
I think me mean   
NEW: A BGP speaker MUST NOT send Extended Messages to its peer if it has not fully exchanged
   the Extended Message Capability with that peer.
---
1 feedback FYI,
In §5, you have changed
from OLD:
 A speaker
   MAY implement a more liberal policy and accept Extended Messages,
   even from a peer to which it has not advertised the capability, in
   the interest of preserving the BGP session if at all possible.

to NEW:
 A speaker
   SHOULD NOT implement a more liberal policy accepting BGP Extended
   Messages.
   
But section 8 still says:
   "Section 5 allowed a receiver to accept an Extended Message even
   though it had not advertised the capability.  This slippery slope
   could lead to sloppy implementations sending Extended Messages when
   the receiver is not prepared to deal with them, e.g. to peer groups.
   At best, this will result in errors; at worst, buffer overflows."
   
Strictly speaking, this is still correct, but significantly changing §5 without changing §8 might also be an oversight.   

Typo
:s/BGP attribue/BGP attribute

Thank you,
--Bruno

-----Original Message-----
From: Randy Bush [mailto:[e-mail]] 
Sent: Sunday, March 10, 2019 10:17 PM
To: DECRAENE Bruno TGI/OLN
Cc: Susan Hares; Interminable Discussion Room
Subject: Re: [Idr] WG Last Call on Extened Message Support

i found your and susan's extended messages rather hard to follow and
therefore hard to apply to the once simple draft.  i have done what i
could.  simple comments, without quoting so much that it is impossible
to decode, appreciated.

randy

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