Hi, all, How to use the 4rd stateless address mapping to support, in a provider network having multiple IPv4 prefixes, both exclusive and shared IPv4 addresses, is an typical question.
Starting from a comment from Quiong Sun, here are some views on the subject. Le 28 juil. 2011 à 11:53, Qiong a écrit : > Hi, Remi, > > Thanks for your comments. I agree with you that in this situation, stateless > solution still superior to stateful ones from scalability aspect. It is "per > independent IPv4 prefix" mapping rule database, rather than customer-based. > But it still may have some tradeoff for domain realm. The larger the domain > it covers, the more independent IPv4 prefix there will be. And also the whole > domain has to synchronize these mapping rules. > > I think this problem would be quite common for large broadband service > providers who already have a huge amount of customers. Do we have to transfer > all these legacy customers with public IPv4 address into shared-mode > directly? In our consideration, we think it might be better to offer > shared-mode solution for new customers only and leave the legacy customers > with non-shared-mode solution to avoid complaint from address sharing. > As a result, we have to deal with the co-existence scenario for at least > shared-mode and non-shared-mode. Yes, I think this will prove a frequent requirement. Complementary comments: 1. A possible approach, to progressively reduce the number of used IPv4 prefixes, consists in proposing two different tariffs: - one for length L of IPv6 prefixes, and full IPv4 address per customer, - the other, slightly lower, for length L+K of IPv6 prefixes, and shared IPv4 address per customer. Thus the number of full-address customers can be expected to decrease, and the longest IPv4 prefixes can be expected to progressively be reclaimed. 2. With a dihcotomic search for a prefix match in BR's and CE', the performance impact of having a large number of rules can remain quite limited, both in CE's and in BR's. (Scalability of the BR function is in any case ensured by the fact that BR's are, with respect to individual-customer states, completely stateless (and also, of course, with respect to transport-connection states). 3. By configuring appropriately as many mapping rules as there are IPv4 prefixes, all IPv4 prefixes can be used without any impact on IPv6 routing (no "IPv4 entropy" exported to IPv6). This is illustrated in sec 3.2 of tools.ietf.org/html/draft-despres-softwire-sam-01 (not too easy to read, sorry for that, but the subject had some intrinsic sophistication and was new). (Incidentally this 4rd founding draft wasn't included Ole's 4rd-history slide yesterday, but is IMHO worth looking at for anyone interested in the genesis of 4rd.) Hope it helps. Regards, RD > I agree that this mapping specification can be applied to all stateless > solutions, separated from specific solution. Thanks for your suggestion. > > Best wishes > > Qiong Sun > > _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
