[Bier] Re: Call for review for draft-ietf-bier-bfd

["Les Ginsberg (ginsberg)" <[e-mail]>]

Folks –

I apologize for the lateness of my comments – I don’t consistently track BIER WG. Some of what I say below would certainly have been more beneficial if provided earlier.
Nevertheless..

Regarding the proposal for new IGP Extensions for advertising BIER BFD information:

I am troubled at the idea of having the IGP advertise information which includes the BIER Bit-String representing the relevant BFR-IDs. This string (defined in RFC 8296) can potentially be up to 4K bits (512 bytes) long.
This is a lot of information for the IGPs to carry – and is particularly troublesome for IS-IS where it exceeds the carrying capacity of a single TLV (max 255 bytes).

As a more minor point, the presence of the RESERVED field is inappropriate for IS-IS. This is commonly done in OSPF to preserve 4 byte field alignment, but this is useless in IS-IS and only serves to bloat the TLV size unnecessarily.

In a larger context, the only previous use of the IGPs to advertise BFD discriminators that I am aware of was done in support of S-BFD (RFC 7883). To my knowledge, implementations have not made use of this extension – perhaps in part because assignment of discriminators based on information in an IGP database has not proved appealing – which calls into question why we should do this here.
NOTE: I am happy to hear feedback from others that RFC 7883 is in fact being used.

Finally, I ask whether any implementation of this draft – even as a POC – has been done? If so, what has been learned?
In general, I am concerned that in the absence of implementation experience we may be standardizing things prematurely.

Thanx for listening to my very late remarks.

    Les


From: [e-mail] <[e-mail]>
Sent: Tuesday, June 25, 2024 12:25 AM
To: [e-mail]; [e-mail]
Subject: [Bier] Call for review for draft-ietf-bier-bfd


Hi,

The draft-ietf-bier-bfd passed last call in BIER WG.

We'd like to get more review in BFD WG: https://datatracker.ietf.org/doc/draft-ietf-bier-bfd/

Comments and suggestion welcomed, please send your comments before 9th, July.



And please volunteer if you want to be the shepherd of this draft.

Thank you!

Best regards,

Sandy