Subject: [Bier] [BIER] conflicting bier parameters advertisement

From: Senthil Dhanaraj <[email-masked]>
Date: Mon, 4 Jun 2018 13:49:37 +0000

Hi All,

There are many conflict scenario's (may be a result of provisioning errors) which are not addressed clearly.
Few examples and suggested behaviors below.
Kindly put forth your thoughts.

(1)
BFR-A ( RouterId: A, Prefix: P1, SD0 [bfrid=1, bsl256[label=x]] )
BFR-B ( RouterId: B, Prefix: P2, SD0 [bfrid=1, bsl256[label=y]] )

Two different routers advertising same bfr-id results in bfr-id conflict.
As per RFC 8279 section-5, BFR-A and BFR-B cannot act as BFERs and cannot receive any multicast packet.

I believe the BFR-A and BFR-B can continue to act as BFR's  (Not as BFERs but just as a BIER forwarding routers)  though it is not mentioned explicitly in the RFC 8279 ?

(2)
BFR-A ( RouterId: A, Prefix: P1, SD0 [bfrid=1, bsl256[label=x]] )
BFR-B ( RouterId: B, Prefix: P1, SD0 [bfrid=1, bsl256[label=x]] )

Two routers advertising same prefix could be a valid scenario in case of Inter-area prefix advertisement.
However in case of intra-area, above could be a provisioning error.
Whether BIER should,

-          Intra-area : Accept. Packet is forwarded based on the prefix-source who has best path from local router?

                        May result in packets delivered to different BFER's just like IP routing.

-          Inter-area : Accept. Packet is forwarded based on the prefix-source who has best path from local router ?

(3)
BFR-A ( RouterId: A, Prefix: P1, SD0 [bfrid=1, bsl256 [label=x]] )
BFR-B ( RouterId: B, Prefix: P1,  SD0 [bfrid=2, bsl256 [label=y]] )

Same as (2), but the bier parameters advertised are different.
Consider both BFR-A and BFR-B as non-bier capable (cannot act as BFER / BFR) ?
Or
Resolve the conflict by means of some algorithm ?

-          Lesser bfr-id wins.

-          If bfr-id is same or 0, but other parameters are different ??

Thanks,
Senthil Dhanaraj
Network Business Line

Huawei Technologies India Pvt. Ltd
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