Hi Robert, Thank you for your comments. Please find my answers inline marked with Mengxiao>.
Thanks, Mengxiao Chen From: Robert Raszuk <[email protected]> Sent: Thursday, July 14, 2022 8:28 PM To: chenmengxiao (RD) <[email protected]> Cc: [email protected]; linchangwang (RD) <[email protected]>; lihao (02566, RD) <[email protected]> Subject: Re: [Lsr] FW: New Version Notification for draft-lin-lsr-srv6-service-sid-00.txt Hi, Thank you for publishing this document. I have few comments about it. #1 - While you are defining IGP extensions I think this document still belongs in BESS WG not in LSR WG. Mengxiao> The solutions proposed in BESS are all BGP enabled. In this document we are discussing the solution without BGP. So, I don't quite understand why it belongs in BESS. #2 - Injecting IPv4 sites to your IPv6 only IGP is IMO a terrible idea. BGP overlays are used to keep core IGPs stable and lean. Networks which do not want to run BGP in the core just use dual stack. Mengxiao> Dual stack is certainly a solution without BGP. However, there are some scenarios that the core network is newly built and the operator only wants to deploy IPv6. To interconnect IPv4 islands under those scenarios, we usually need to build ipv4 over ipv6 tunnels (for example, GRE-tunnel) between the edge routers of different islands. This work is usually done manually, and the number of tunnels may be large. Then, the edge routers establish IGP neighbors through those tunnels. With the advertisement of SRv6 End.DT4 SIDs in IGP, the interconnection of IPv4 islands can be automatic and efficient. Besides, this mechanism may be extended to IPv6 only networks. For example, in the campus network not deploying BGP, advertising SRv6 End.DT6 SIDs along with color in IGP may be used to provide SRv6 TE service for IPv6 sites. #3 However I do see value of general idea as expressed in this draft but only for deployment scenario where you DO NOT inject prefixes from sites to your IGP core and you use CSC (carrier's carrier) approach - still no BGP in IPv6 core. That means IPv4 sites exchange IPv4 reachability over the top and encapsulate packets to the other edge of IPv4 islands. Mengxiao> That is an interesting idea. As mentioned above, the traditional solution builds IPv4 over IPv6 tunnels through which the edge routers of different islands establish IGP neighbors. So, the tunnel-based solution is a kind of CSC approach. Do you mean we can use SRv6 Service SIDs somehow to improve the tunnel-based solution for IGP? Or, we just use SRv6 Service SIDs to build tunnels instead of GRE? So for #3 I would in fact state that this is not a bad idea. But not for #2 as currently written. Many thx, Robert. On Thu, Jul 14, 2022 at 1:58 PM Chenmengxiao <[email protected]<mailto:[email protected]>> wrote: Hi WG, We posted a new draft: draft-lin-lsr-srv6-service-sid-00. It's about advertising SRv6 service SID in IGP. For the IPv6 backbone networks not deploying BGP, for example, the campus network using IS-IS or OSPFv3, there may be requirements to interconnect IPv4 islands. SRv6 Service SIDs like End.DT4 may be used to realize such requirements. Similar with the BGP based L3 Service over SRv6, SRv6 Service SIDs like End.DT4 may be used to realize such requirements. This document extends IS-IS and OSPFv3 to advertise SRv6 Service SIDs along with prefixes. The receiving router creates forwarding entries associated with SID. In the IPv4 over IPv6 scenario, the IPv4 packets will be encapsulated in an outer IPv6 header with the destination address of SRv6 Service SID and forwarded according to the SID. When they are forwarded to the destination, the SID's owner decapsulates the outer IPv6 header and performs IPv4 table lookup to forward the inner IPv4 packet. Furthermore, it may be extended to support SRv6-TE Services in IGP. Any questions or comments are welcomed. Thanks, Mengxiao Chen -----Original Message----- From: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Sent: Monday, July 11, 2022 4:38 PM To: linchangwang (RD) <[email protected]<mailto:[email protected]>>; lihao (02566, RD) <[email protected]<mailto:[email protected]>>; chenmengxiao (RD) <[email protected]<mailto:[email protected]>> Subject: New Version Notification for draft-lin-lsr-srv6-service-sid-00.txt A new version of I-D, draft-lin-lsr-srv6-service-sid-00.txt has been successfully submitted by Mengxiao Chen and posted to the IETF repository. Name:draft-lin-lsr-srv6-service-sid Revision:00 Title:IS-IS and OSPFv3 Extensions to Advertise SRv6 Service SID Document date:2022-07-11 Group:Individual Submission Pages:9 URL: https://www.ietf.org/archive/id/draft-lin-lsr-srv6-service-sid-00.txt Status: https://datatracker.ietf.org/doc/draft-lin-lsr-srv6-service-sid/ Htmlized: https://datatracker.ietf.org/doc/html/draft-lin-lsr-srv6-service-sid Abstract: The IPv6 backbone networks only deploying IGP may be required to interconnect IPv4 islands. SRv6 Service SIDs like End.DT4 may be used to realize such requirements. This document extends IS-IS and OSPFv3 to advertise SRv6 Service SIDs. 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