[bess] Re: A controversy in draft-ietf-bess-rfc7432bis

["Ali Sajassi (sajassi)" <[e-mail]>]

Hi Sasha,

Thanks for bringing this to our attention. RFC7432bis already talks about two-bit field for redundancy mode and defines two values for it (All-Active and Single-Active). So, we will ensure that the term redundancy mode is used consistently throughout the document with values of All-Active or Single-Active Redundancy Mode.

Cheers,
Ali

From: Alexander Vainshtein <[e-mail]>
Date: Wednesday, July 10, 2024 at 5:41 AM
To: [e-mail] <[e-mail]>
Cc: [e-mail] <[e-mail]>
Subject: A controversy in draft-ietf-bess-rfc7432bis
Hi,
I think that I have found a controversy in the latest version of the 7432bis<https://datatracker.ietf.org/doc/html/draft-ietf-bess-rfc7432bis-09> draft.

Section 5 of the draft contains the following text:

If a bridged network does not connect to the PEs using a LAG, then only one of the links between the bridged network and the PEs must be the active link for a given <ES, EVI>. In this case, the set of Ethernet A-D per ES routes advertised by each PE MUST have the "Single-Active" bit in the flags of the ESI Label extended community set to 1.


Section 8.2.1 of the draft conatis the following text:
The ESI Label extended community MUST be included in the route. If All-Active redundancy mode is desired, then the "Single-Active" bit in the flags of the ESI Label extended community MUST be set to 0 and the MPLS label in that Extended Community MUST be set to a valid MPLS label value.
…
If Single-Active redundancy mode is desired, then the "Single-Active" bit in the flags of the ESI Label extended community MUST be set to 1 and the ESI label SHOULD be set to a valid MPLS label value.

Section 8.4 of the draft mentions “the "Single-Active" bit in the flags of the ESI Label extended community”.


Section 14.1.1 of the draft contains the following text (copied verbatim from the namesake section of RFC 7432<https://datatracker.ietf.org/doc/html/rfc7432>)

For a given ES, if a remote PE has imported the set of Ethernet A‑D per ES routes from at least one PE, where the "Single-Active" flag in the ESI Label extended community is set, then that remote PE MUST deduce that the ES is operating in Single-Active redundancy mode.

Similarly, Section 14.1.2 of the draft contains the following text:

For a given ES, if the remote PE has imported the set of Ethernet A-D per ES routes from one or more PEs and none of them have the "Single‑Active" flag in the ESI Label extended community set, then the remote PE MUST deduce that the ES is operating in All-Active redundancy mode.



The problem with all these (and, possibly, some other) fragments is that the “Single-Active bit” (or flag) in the Flags field of the ESI Label extended community that has been defined in RFC 7432 does not exist in the 7432bis draft. Instead, Section 7.5 of the dratf defines a two-bit RED subfield in the Flags field of the ESI Label Extended Community, and defines two (out of 4) possible values for this field. (Yet another value is defined in the Layer 2 EVPM Multi-Homing Mechanism for Layer 2 Protocol Gateways draft<https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-l2gw-proto-04>.)

Hopefully, these notes will be helpful.

Regards,
Sasha



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