Ryuji, After viewing your slides from the presentation you did overnight (sorry I couldn't be on the call) I went back and re-read the draft-matushima-stateless-uplane-vepc-02 draft. I am still confused about a number of things:
You show in Figure 4, step 15 a Route Update (is this a BGP UPDATE?) going from the EPC-E to the core network RTR, containing a Destination of UE-prefix and a Next-Hop of EPC-E address. However, in Section 3.4, you describe the RTR as knowing only the PDN prefix, which is the same for all EPC-E, and the use of "hot-potato" routing to deliver the packets to the nearest EPC-E no matter the UE destination IP address. Which one is it? Are the UE prefixes advertised into the core or not? Assuming for now that the UE prefixes are not advertised into the core, but only the PDN prefixes are advertised, then that means that every EPC-E must know about every UE session, including the eNB F-TEID for every UE in the network, correct? That's because any one of them at any time could receive a packet for the UE from the core. This doesn't seem scalable to me. You seem to attempt to address this issue in Section 4.1 when you talk about multiple "sets" of EPC-E devices, each one dedicated to a given geographic region. It seems to me that each "set" of EPC-E could cover no more than the scope covered by a single SGW today, because they each have the same amount of state as an SGW. Essentially you have described how to build a replicated SGW with failover to different nodes based on the re-convergence of BGP after a failure (presumably you could get the core network to react to the closure of a BGP TCP session). So I think this addresses the problem of fault-tolerance that has been identified with the tunnel-based solutions, but not really the scalability bottleneck problem. In fact, if you consider mobility from one "set" to another, if you want to keep the UE's IP address, you would need to broadcast the same set of PDN prefixes from all sets of EPC-E. In fact this would mean that all EPC-E throughout the network, even if they are in different "sets", need to be prepared to handle packets for any UE and so they ALL would need the eNB F-TEIDs for ALL UEs. Please tell me where I have made a mistake. -- Peter J. McCann Huawei Technologies (USA) [email protected] +1 908 541 3563 Rm. C-0105, 400 Crossings Blvd. (2nd floor), Bridgewater, NJ 08807-2863 USA _______________________________________________ dmm mailing list [email protected] https://www.ietf.org/mailman/listinfo/dmm
