Re: [bess] Question regarding section 17.3 draft-ietf-bess-rfc7432bis

[Alexander Vainshtein <[e-mail]>]

Menachem and all,
As I see it, Section 17.3 of 7432bis<https://datatracker.ietf.org/doc/html/draft-ietf-bess-rfc7432bis-06#section-17.3> does not differ from Section 17.3 in RFC 7432<https://www.rfc-editor.org/rfc/rfc7432#section-17.3>.
Both documents only define reaction of the EVPN Control Plane to failure of a PE-CE link, and these definitions guarantee that remote PEs would stop sending "known unicast" traffic for customer MAC addresses that have been learned from the failed link to the affected PE.

If the failed link belonged to a multi-homed Ethernet Segment, fast recovery of affected traffic can be provided using the method defined in the EVPN Fast Reroute<https://datatracker.ietf.org/doc/html/draft-burdet-bess-evpn-fast-reroute-03> draft.


Regards,
Sasha

From: BESS <[e-mail]> On Behalf Of Menachem Dodge
Sent: Monday, January 9, 2023 10:22 AM
To: [e-mail]
Subject: [EXTERNAL] [bess] Question regarding section 17.3 draft-ietf-bess-rfc7432bis

Hello All,


In section 17.3 of the draft-ietf-bess-rfc7432bis PE-to-CE Network Failures the first paragraph states that:

"If the connectivity between the multihomed CE and one of the PEs to which it is attached fails, the PE MUST withdraw the set of Ethernet A-D per ES routes that had been previously advertised for that ES."

...

"When the MAC entry on the PE ages out, the PE MUST withdraw the MAC address from BGP."

The last paragraph of that section 17.3 states that:

When a PE receives a withdrawal of a particular Ethernet A-D route from an advertising PE, it SHOULD consider all the MAC/IP Advertisement routes that are learned from the same ESI as in the Ethernet A-D route from the advertising PE as having been withdrawn. This optimizes the network convergence times in the event of PE-to-CE failures.

Clarification

Please could you explain why the PE that has detected the network failure to its CE is retaining the MAC addresses until age-out time, and only then withdrawing the MAC/IP Advertisement routes; while all the remote PEs that receive the withdrawal of the Ethernet A-D route should be considering all the MAC/IP Advertisement routes received from that PE and learned from that ESI as having been withdrawn, without waiting for the withdrawal of the MAC/IP Advertisement routes. This seems to be inconsistent behavior.

Thank you kindly.

Best Regards,

Menachem Dodge
System Architect
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