Thanks, see inline for additional remark.
/Eduard
________________________________
But if IPv4 only nodes(Egress/Ingress) are sitting behind RRs, then there can
be two scenarios as described in the draft
+------------------------+
| +----+ |
| | RR | |
| +/--\+ |
| / \ |
| +----+ +----+ |
| |PE-1| |PE-2| |
| +----+ +----+ |
| Egress Ingress |
+------------------------+
Figure 1: Route Reflector Topology Example
The following rules apply when reflecting routes between clients:
1. Both clients support the Dual Service Encoding Capability: The RR MUST
reflect the route without modification. It MUST preserve the MPLS Label and
SRv6 Service SID exactly as received.
2. Egress PE supports the capability; ingress PE does not: The RR MUST ensure
compatibility with the ingress PE. It SHALL reflect the route in a form
compliant with [RFC9252], which results in SRv6-only semantics. In practice,
this means the MPLS Label field SHOULD be set to the Implicit NULL label. If
the Ingress PE is IPV4 only neighbor, then RR will be changing the nexthop to
IPv4 address and will advertise the update with MPLS label only.
3. Ingress PE supports the capability; egress PE does not: The route received
by the RR is compliant with [RFC9252]. The RR MUST reflect the route without
modifying the MPLS Label field or SRv6 Service SID. If the Egress PE is IPv4
only neighbor, then it will not originate/advertise the VPN service prefix with
both MPLS label and SRV6 Sid in a single update, it will only send MPLS label
with Nexthop set to IPv4 address. RR will reflect the same to Ingress PE.
In all cases, the RR MUST NOT introduce ambiguity in the encoding and MUST
preserve correct forwarding semantics.
[EM] Regarding #2, to support this case, the IPv4 is configured in the RR as
part of some policy?
[EM] Would be good to elaborate more on the RR role / functionality for the
different use-cases (combinations of RR client) in the draft. The current text
(below e.g. for egress supporting / ingress not) does not cover all cases.
" Egress PE supports the capability, ingress PE does not: The RR MUST
ensure compatibility with the ingress PE. It SHALL reflect the route
in a form compliant with [RFC9252], which results in SRv6-only
semantics. In practice, this means the MPLS Label field SHOULD be
set to the Implicit NULL label. "
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