Re: [bess] A minor contradiction between RFC 9135 and RFC 9136?

[Alexander Vainshtein <[e-mail]>]

Hi all,
A gentle reminder...

Regards,
Sasha

From: Alexander Vainshtein
Sent: Sunday, November 19, 2023 2:22 PM
To: Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]>; [e-mail]; Ali Sajassi (sajassi) <sajassi=[e-mail]>; John E Drake <jdrake=[e-mail]>; [e-mail]; [e-mail]; [e-mail]
Subject: FW: A minor contradiction between RFC 9135 and RFC 9136?

Hi all,
The email expansions for the authors of RFC 9135 and RFC 9136 do not work anymore.
Therefore, I forward my email to you individually.

Regards,
Sasha

From: Alexander Vainshtein
Sent: Sunday, November 19, 2023 2:08 PM
To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Cc: [e-mail]<mailto:[e-mail]>
Subject: A minor contradiction between RFC 9135 and RFC 9136?
Importance: High

Hi all,
I see what looks to me as a contradiction between Section 9.1.1 of RFC 9315<https://datatracker.ietf.org/doc/html/rfc9135#section-9.1.1> and Section 4.4.1 of RFC 9136<https://datatracker.ietf.org/doc/html/rfc9136#section-4.4.1>:


1.       The former:

a.       Defines a Symmetric IRB as an interface connecting an IP-VRF to an EVPN Broadcast Domain (a MAC-VRF or a specific BBD within a MAC-VRF that implements VLAN-Aware service interface)

b.       Describes an IP Prefix (EVPN Type 5, a.k.a. RT-5) route advertised for the subnet of a Symmetric EVPN IRB and states that RD in the NLRI of this route is the RD of IP-VRF that contains that the IRB in question

2.       The latter describes the Interface-less IP-VRF to IP-VRF model:

a.       To the best of my understanding, this model deals with just Symmetric IRBs

b.       The RFC states that the NVE/DGW will, for each of its prefixes, advertise an RT-5 with RD in its NLRI as defined in RFC 7432<https://www.rfc-editor.org/rfc/rfc7432.html>. Since RFC 7432 does not refer to IP-VRFs at all, this strongly suggests to me that it means RD of a MAC-VRF .

The following diagram shows why this difference may be meaningful:

[cid:image001.png@01DA2B65.E342FB80]
In this diagram PE-1, PE-2 and PE-3 can only exchange L2VPN/EVPN routes but not VPN-IP routes.
Suppose that IP-VRF in PE-1 and PE-2 are configured with a static route to SN-. In this case:

-          PE-1 and PE-2 can advertise RT-5 for SN-1 using either RDs of IP-VRFs or RDs of MAC-VRF

-          If RT-5 uses RDs of containing IP-VRF, bi-directional connectivity between devices in SN-1 and SN-2 can be established

-          If RT-5 uses RDs of MAC-VRF in its NLRI, PE-3 cannot advertise RT-5 for SN-2 because there is no MAC-VRF in this PE.


What, if anything,  do I miss?

Your timely feedback would be highly appreciated.

Regards, and lots of thanks in advance,
Sasha

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