Hi all authors of segment routing,
This is the second issue. In order for better understanding and discussion, I include MPLS WG in the discussion. I will propose one use case of LDP proxy egress: Inter-AS VPN Option C PE11--------ASBR11--------ASBR21-------PE21 | | | | | AS1 | | AS2 | | | | | PE12--------ASBR12--------ASBR22-------PE22 In this case, the label BGP(RFC3107) can advertise the label route for PE21 and PE22 from the ASBR in AS2 to the ASBR in AS1. Some carriers prefers to use label BGP to go on to advertise the label route to PE11 and PE12. But some carriers do not like full mesh BGP peers and three layer label for the traffic, they would redistribute the BGP routes to IGP at ASBR11/ASBR12 and depend on LDP to setup LDP LSP for the prefix PE21/PE22 in the AS1. For the use case if the SR is adopted, there may propose following challenges: 1. How to configure the SID/label for these proxy egress addresses? On both ASBR11 and ASBR22? If there more ASBRs, there will be more configuration work. Is it right? 2. According to seamless MPLS, there may be 10,000 node addresses. If take the assumption, it will be a great configuration work. 3. The label route on the ASBR can be dymamic changed. Is there the case that the more or less SID/Labels are configured? If my understanding is right, comparing with the simple case with actual egress, there will be more challenge for the proxy egress case for SR. In fact, there are more usecases of proxy egress: 1. C & C: Proxy egress for the VPN routes 2. Seamless MPLS: Proxy egress for the LDP DoD 3. Some usecases which needs LDP node and Non-LDP node coexists. I wonder if you have thought about the proxy egress scenarios and what is the possible solution? If the proxy egress cannot be supported, there will be more challenges: 1. LDP cannot be replaced by SR-BE path. In the above usecase, LDP Proxy Egress and SR actual egress may have to co-existed. It will be too complexed and SR is totally unnecessary. 2. TI-FRR for the proxy egress case cannot supported either. But this case can be supported by other FRR solutions. Hope to get your opinion on the progress egress for SR. Regards, Robin
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