Remi, > The key is "keep it simple", with neither IPv4 addresses nor PSIDs in MAP-E > IIDs. > More explanations below. > > 2013-01-28 14:51, Wojciech Dec <[email protected]>t : > >> Hi, >> >> the IPv4 and PSID in the IID are particularly useful in cases of address >> independence (ie 1:1). As said previously, the benefit is primarily in the >> ability an operational facilitation, where an operator can easily >> see/observe what IPv4 and PSID is being used by a given customer. This is >> easier than to look at the v6 prefix and use some magic decoder ring. > > (a) The IPv4 address already readable in the encapsulated IPv4 packet (the > subject is only MAP-E, not MAP-T or 4rd).
yes. > (b) With the proposed IID format, the length of the PSID cannot be determined > without looking at the applicable mapping rule. (As already noted, the number > of zeroes at the end of the PSID isn't specified in the address). correct. > (c) Once the rule is looked at, getting the PSID is easy (no more magic > needed than to get find the PSID length ;-)). unless you are in 1:1 mode. >> In addition, it has the desirable characteristic of creating an IID. > > A constant IID was the logic proposal for the original Encapsulation solution > (then called "4rd" before becoming "MAP-E", ref. > tools.ietf.org/html/draft-murakami-softwire-4rd-01). > It is only when we tried to merge -E it with -T that we abandoned this > simplicity. simplicity for whom? the interface-id is constant for the MAP node. I have not heard any implementors state it is hard enough to be worth arguing over whether to write an IPv4 address in there rather than a set of zeroes. what is simplest for the operator? having to calculate the IPv4 address based on the rules? or look at the IPv4 address in the IID? > (Incidentally, to avoid limitation (b) above, we introduced that at that time > a PSID-length field in IIDs (ref. > www.ietf.org/mail-archive/web/softwires/current/msg02994.html), but this > complexity would be superfluous for MAP-E.) to summarise, your proposal is to overlap with the subnet router anycast address, i.e. all zeroes? cheers, Ole _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
