Subject: Re: [bess] A doubt about draft-sajassi-bess-evpn-ip-aliasing-05

From: "Ali Sajassi (sajassi)" <[email-masked]>
Date: Thu, 17 Nov 2022 15:49:25 +0000

Hi Sasha,

EVPN based RFCs (7432 and 8365) define two types of multi-homing: All-Active and Single-Active. Both of these multi-homing mechanism relies on multi-homing PEs to control loop detection and prevention using DF election and split-horizon filtering.  draft-ietf-bess-evpn-l2gw-proto-02<https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-l2gw-proto-02> introduces a 3rd multi-homing mechanism called Single-Flow-Active for scenarios where loop detection and prevention are performed by CE devices (running L2GW protocols) and not PEs.

draft-sajassi-bess-evpn-ip-aliasing-05<https://datatracker.ietf.org/doc/html/draft-sajassi-bess-evpn-ip-aliasing-05> basically extends the baseline multi-homing mechanism of All-Active to L3 use cases mentioned in the draft (e.g., symmetric IRB). This draft is NOT intended for Single-Flow-Active multi-homing use case.  If single-flow-active multi-homing need to get extended to L3 use cases, then it can be covered in a follow-up single-flow-active draft.

Cheers,
Ali

From: Alexander Vainshtein <[email-masked]>
Date: Thursday, November 17, 2022 at 2:25 AM
To: [email-masked] <[email-masked]>
Cc: Luc André Burdet <[email-masked]>, [email-masked] <[email-masked]>, Nitsan Dolev <[email-masked]>, Alexander Ferdman <[email-masked]>, Ron Sdayoor <[email-masked]>, Dmitry Valdman <[email-masked]>
Subject: A doubt about draft-sajassi-bess-evpn-ip-aliasing-05
Hi,
I have doubts regarding applicability of the solution for L3 fast convergence defined in draft-sajassi-bess-evpn-ip-aliasing-05<https://datatracker.ietf.org/doc/html/draft-sajassi-bess-evpn-ip-aliasing-05> for the scenarios in which the MH ES in question operates in Single Flow-Active load-balancing mode as described in draft-ietf-bess-evpn-l2gw-proto-02<https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-l2gw-proto-02>.

These doubts are based on the fact that, in Single Flow-Active load-balancing mode, the Primary PE is defined by the Layer 2 Control Protocol (or its equivalent) for each specific host, while the EVPN IP Aliasing draft advertises Primary/Backup paths via P/B bits in the EVPN Layer 2 Extended Community attached to the IP A-D EVPN routes.

What, if anything, did I miss?

Your feedback would be highly appreciated.

Regards, and lots of thanks in advance,
Sasha

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