Hi Xuesong, Mach, Fan,

Some comments/questions on the proposal.

1. We don't need an additional "redundancy segment" for the replication 
semantics. Existing "replication segment" 
(draft-ietf-spring-sr-replication-segment) can be used as is, especially for 
the scenario where the original header already carries (FI, SN) information.
2. Even for the scenario where the (FI, SN) information needs to be added by 
the redundancy node, the existing "replication segment" can be enhanced to add 
the (FI, SN) information.
3. I wonder why (FI, SN) information is added as a TLV in the SRH. Would it be 
better to use DOH?

For #1, and #2, reusing/enhancing existing replication segment has the 
following benefits:

a. Reduce protocol/implementation work
b. Reduce the amount of state in the network (the same P2MP tunnel can be used 
for both multicast traffic and unicast redundancy)

b) can be achieved even with #2 (redundancy node needs to add (FI, SN) 
information): for SRv6, the semantics of adding (FI, SN) can be indicated by 
the arg part of the replication SID and for SR-MPLS it can be indicated by an 
additional label in front of the replication sid label. If using an addition 
label is a concern, then indeed a single label can be used to indicate both 
"add FI/SN information" and "replicate", but still the replication semantics 
can still be set up using the replication segment infrastructure.

For SR-MPLS, where would you put the (FI, SN) information? Seems that GDFH 
(draft-zzhang-intarea-generic-delivery-functions) is a good option and that can 
be used for SRv6 as well (anything in DOH that is actually independent of IP 
could be extracted out to GDFH).

Thanks.

Jeffrey

Juniper Business Use Only
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