On 2012/02/07, at 17:53, Rémi Després wrote: > > Le 2012-02-07 à 17:35, Satoru Matsushima a écrit : > >> On 2012/02/07, at 16:46, Rémi Després wrote: >> >> --snip-- >> >>>>> >>>>>>>> I think that operators who already deploy such dual-stack network is >>>>>>>> supposed that they have address mapping table, >>>>>>> >>>>>>> I would rather suppose that ISPs that have added IPv6-prefix >>>>>>> delegation, say /56s, to an existing IPv4 network did it without mixing >>>>>>> their IPv6 plan with their IPv4 prefixes. >>>>>>> I am ready, however, to look seriously at individual cases where >>>>>>> choices were different. >>>>>> >>>>>> Basically provision MAP CE is based on its delegated IPv6 prefix in >>>>>> concept. It is opposed to your case but technically possible. >>>>> >>>>> >>>>>> Now I concern that it requires much complicated CE implementation. >>>>> >>>>> All what is required is that CEs set an address bit if hub&spoke topology >>>>> is required. >>>>> >>>> >>>> So how CE decide to set the bit, and when the CE figure it out? >>> >>> The CE knows it must set this bit if, and only if, it received at >>> initialization a Topology-variant parameter set to Hub&spoke (sec 4.1). >>> In this case, the CE sets bit 79 to 1 in IPv6 destination addresses of all >>> packets it sends. >>> >>> BTW, this bit should better, for clarity, be given a name, e.g. bit B >>> meaning To-BR bit (or whatever better idea one could propose). I plan to do >>> it in the next version. >>> >> >> So you mean that if the hub&spoke bit is set, a CE derives /112 IPv6 prefix >> as 4rd end point from IPv4 address which is already assigned. > > > If the CE is delegated a prefix shorter than /64, it isn't concerned with the > To-BR bit. > If it is delegated a /112, it finds its IPv4 address inom it. > It then must set the To-BR bit, in its outgoing IpV6 destinations, iff the > Topology variant is Hub&spoke. >
As you described in your draft, if a CE is delegated /112 IPv6 prefix, the CE automatically form itself for H&S mode and extract a non-sharing IPv4 address from the /112 prefix. > >> Otherwise, a CE derives its IPv4 address from delegated IPv6 prefix. right? > > The CE always derives its 4rd prefix from its delegated IPv6 prefix, based on > the Mapping rule that has the longest match. > So you mean that it is only specific case of which if the extracted IPv4 address is same with an address assigned to a dual-stack interface on the CE, the default route on the CE is forced to the BR, and keep that address on the dual-stack interface as NAPT source address. Is that what you request to 4rd-U CE implementation? It also requires operator to manage specific /112 route for each CE that means IPv4 host routes are injected to the operator's IPv6 routing table that's what Ole already pointed out. I agree with Ole that I'm doubt it could be widely acceptable technique for operators. cheers, --satoru _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
