> PC2: Let me try to give you an analogy. A external packet arrives to an ILA > network. The original IPv6 DA is translated as per ILA. What is the packet? > Is it an IP packet or is it an ILA packet? To me this is an ILA packet, > because if the source and destination UPFs are not ILA capable the overlay > does not work. > Pablo,
It is an IPv6 packet that has a destination address that is interpreted with ILA semantics and the destination node. The format of the packet is IPv6, the Ethertype is 0x86dd, and the packet is compliant with the IPv6 protocol standard. Every intermediate device in the path sees a plain IPv6 packet. The property that a packet with an ILA address is indistinguishable on the wire from other IPv6 packet is critical to ILA. > PC2: For this reason, I would not call the above SRv6 example IPinIP. It > needs SRv6 on the UPFs, hence calling it IPinIP does not reflect the > requirement of running SRv6 on the destination UPF -which in my opinion is > considerable to highlight-. It's still not clear to me exactly what the wire format is of SRv6 traditional mode is. 5.5 of draft-filsfils-spring-srv6-network-programming describes the encapsulation operation as: 1. push an IPv6 header with its own SRH (S3, S2; SL=2) 2. set outer IPv6 SA = T and outer IPv6 DA = S1 3. set outer payload length, traffic class and flow label ;; Ref1 4. update the Next-Header value ;; Ref1 5. decrement inner Hop Limit or TTL ;; Ref1 6. forward along the shortest path to S1 Step #4 is ambiguous. It doesn't indicate what the Next-Header value needs to be updated to. Also, it's not really clear which Next-Header field is being updated (there could be an inner value and an outer value). I infer that it is the Next-Header value in the outer IPv6 header and that it is set to either 0x04 or 0x29 if the inner packet is IPv4 or IPv6 respectively. Assuming that all other fields are set normally for IPv6, then the derived packet has the format of a simple IP-in-IPv6 encapsulation and that's that how it will be seen on the wire by intermediate nodes (which similar to case of ILA I think is a good property to have). Is my inference correct? Tom > > > > Tom > > > > _______________________________________________ dmm mailing list dmm@ietf.org https://www.ietf.org/mailman/listinfo/dmm
