Re: [Bgp-autoconf] bgp auto configuration -01 update after interim discussion

[Jeffrey Haas <[e-mail]>]

On Wed, Jun 23, 2021 at 03:52:49PM +0200, Robert Raszuk wrote:
> * Assume we did not reach mutually interesting AFs to establish session and
> we suppressed OPENs as you said. Now if I add a new AF on either side - do
> I need AD PDU or can I just try BGP OPEN as I already know the peer(s) ?

OPEN messages weren't suppressed.  BGP just decided the peer was
unacceptable.  Very much like when one side requires an AFI/SAFI to be
negotiated and it didn't see it.

Consider this example:

Time 1: The client opens a session to discovered peer and does not see 
VPNv4 Unicast in the OPEN message.  It closes the session without letting it
proceed to Established.

Time 2: The discovery message indicates the version number has changed.

Time 3: The client opens a session again.  This time, it notices that the
required VPNv4 Unicast is present and considers the session acceptable.  The
session is permitted to move to Established.

> Not related:
> 
> Just like in BGP perhaps we should also support passive AD side ? Say in
> leaf <--> spines or leaf <--> controller that can be perhaps useful
> optimization.

That's certainly permissible in the mechanism described.  Auto-discovery
doesn't remove the need for all configuration.

If both sides select passive mode, nothing will come up.

-- Jeff