Thomas:
It is possible to create an option that requires implementation support
extended messages upon receiving a notification. If the sequence is:
Open-(4097 bytes) -->
<-----notification (with indication message length is too long)
(sequence allowed RFC4271 current FSM)
The extended messages would know to back down to 4096 and negotiate forward.
This would not let your BGP speaker get stuck. It seems reasonable to make
the code take care of this problem rather than have a crisis in an
operator's day.
Open (< 4096) bytes) --->
Just let us know what you want.
Sue
-----Original Message-----
From: Thomas Mangin [mailto:[email protected]]
Sent: Tuesday, March 7, 2017 4:39 PM
To: [email protected]
Cc: Susan Hares
Subject: Re: [GROW] Do you want BGP to extend the message size for all BGP
messages or just UPDATES.
Hello Nick,
I can see one reason why it would become undesirable in the future:
If a then recent speaker, with support with this draft/RFC, and with a
yet-to be defined large number of capabilities, happened to generate an OPEN
message of 4097 bytes (to match its configuration), this OPEN would most
likely be seen as invalid by current implementations not supporting the
extension.
The excessive/invalid length when checking the OPEN message size will surely
caused the session to be terminated.
It would therefore prevent any session to come up (even if otherwise
everything is fine). Therefore should this size extension be applied, it
should be applied to all message types BUT the OPEN message. I think we are
currently not near needing 4096 bytes for OPEN (but the day will/may come).
ExaBGP would suffer from this issue as the check is currently performed on
ALL messages as currently specified including the OPEN.
So I would suggest to just change the wording to include all message type
but OPEN, and leave it as an exercise to the reader to write another draft
allowing to break capabilities over multiple messages.
Sincerely,
Thomas
> On 7 Mar 2017, at 21:08, Nick Hilliard <[email protected]> wrote:
>
> Susan Hares wrote:
>> This email is to make you aware of the discussion on the Extended
>> Messages draft (draft-ietf-idr-bgp-extended-messages-21). Do you
>> want the message size extended for all BGP messages or just UPDATE
>> messages? This probably is more important if you want to have a
>> larger size OPEN, ROUTE-REFESH, and UPDATES. The IDR co-chairs
>> value the operational input from GROW WG.
>
> I don't see any reason an extended message size should be limited to
> just UPDATEs. Enke's suggestion for handling the single anomalous case
> (OPEN) looks reasonable. I'd say, go for it!
>
> Nick
>
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