Le 2012-02-03 à 13:25, Ole Trøan a écrit : > Remi, > >>> here is a comparison table of the feature differences between MAP and 4rd-U. >>> (try a fixed width font if it doesn't survive your particular MUA mail >>> mangling algorithm.) >>> >>> Appendix A. Comparions of stateless A+P solutions >>> >>> +-------------------------------+----------------+------------------+ >>> | Feature | MAP | 4rd-U | >>> +-------------------------------+----------------+------------------+ >>> | Encapsulation | Y | Y | >>> | Translation | Y | Y | >>> | Hub and Spoke mode | Y | Y | >>> | Nested CPE | N | Y | >>> | End-user prefixes > 64 | Y | N | >> >> (1)It is AFAIK also a "Y" for 4rd. >> (Not sure to understand the point.) > > I might have misunderstood R-11 and R-24. it depends on the V octet. > but I suppose for any solution it is more of a deployment choice than a > inherent limitation to the mechanism.
Unless use cases showing a practical limitation of 4rd-U in this respect, this line can then be left out. OK? > >>> | E-mode: Support for IPv4 | Y | N | >>> | options | | | >> >> (2) 4rd-U draft 03 has excluded IPv4 options for both 4rd-H and 4rd-E but, >> for 4rd-E, they can easily be put back if found useful. (My vote is NO, but >> a WG consensus on YES for 4rd-E would not be a problem at all). > > indeed, part of the smorgasbord of features the working group can choose > between. The design team is mandated to assemble a particular proposal, and the WG then decides what to do with it, globally or piece by piece. >>> | T-mode: MF bit and TOS bits | N | Y | >>> | transparency | | | >>> | T-mode: Checksum | L4 rewrite | CNP | >> >> (3) The functional point is guaranteeing IPv4-payload preservation, with >> compatibility with ALL protocols using TCP-like checksum, present of future, >> with checksums anywhere in the payload. > > the MDT recommends L4 rewrite: > - this is what existing implementations do > - works for any L4 protocol Present or future without change? > (MAP has to be L4 aware for port anyway) > >>> | H & S set bit 79 needed | N | Y | >> >> (4) The functional point is to permit use cases like that of 5.3 of the last >> 4rd-U draft. >> The added complexity for this is close to nil, and applies ONLY to H&S >> scenarios. >> >> If abandoned (which is easy), it should be with due WG consciousness of >> which use cases are thus abandoned. > > indeed. > >>> | Interface-id | RFC6052 | V octet | >>> | MAP traffic identified by | Address/prefix | Interception of | >>> | | | V octet | >> >> (5) The main functional point of the V octet is to avoid interfering with >> subnet assignments in customer sites. > > the MDT recommendation is to set aside a prefix or an IPv6 address to > terminate MAP traffic. Indeed, so that an IPv6 site to which MAP support is added may have to change its intra-site subnet assignments for this. This is avoided with the V octet. > >> (6) Not sure to understand what you mean by "Interception of V octet". IPv6 >> routing within CEs or BRs is sufficient to orient IPv6 packets to the 4rd >> function. > > if classification of MAP packets versus native packets have to be done, not > using the best matching prefix algorithm, but a non contiguous mask. e.g.: > > a match on: > 2001:db8:1234:*:0V00:* (6.a) In BRs or CEs, the first * isn't needed because its value is fixed so that best matching works. (6.b) In middle boxes, if this is what you discuss, testing the V octet is sufficient. (6.c) Note that use cases where middle boxes interpret tunnel packets is the case where MAP-T and 4rd-H have their functional advantages over MAP-E and 4rd-E. > >>> | Port mapping algorithm | GMA. Prog. | GMA. Fixed | >> >> (7) Substantial complexity added for GMA isn't justified, in my >> understanding, by real use cases that would need it. >> This could easily be added to 4rd-U if so decides the WG (a waste IMHO). > > GMA and the 4rd-U algorithm is the same algorithm. with the same bit > representation on the wire. - The 4rd-U algorithm is: "A port of the port set contains the PSID, starting at bit 4. - The MAP algorithm is: "1. The port number (P) of a given PSID (K) is composed of: P = R * M * j + M * K + i Where: * PSID: K = 0 to R - 1 * Port range index: j = (4096 / M) / R to ((65536 / M) / R) - 1, if the port numbers (0 - 4095) are excluded. * Contiguous Port index: i = 0 to M - 1 2. The PSID (K) of a given port number (P) is determined by: K = (floor(P/M)) % R Where: * % is the modulus operator * floor(arg) is a function that returns the largest integer not greater than arg." - It has to be faced that this isn't the same algorithm. This difference is significant because the simpler the algorithm, the simpler is personnel training, and the simpler if network maintenance. > the MAP text goes in more detail in explaining how to calculate the port > ranges and so on. > 4rd-U has fixed (a) the offset bits, while MAP has the same default, but > allows it to be configured. > >>> | Fragment forwarding on BR | N | Y | >>> | without reassembly | | | >>> | Shared fragmentation id space | N | Y | >>> | BR rewrite fragmentation | N | Y | > > btw, in 4rd-U did you intend for the BR to rewrite the fragmentation id on > packets to the Internet from the CEs? (6-bis) As explained in the draft, not for packets from ALL CEs. But the 4rd-U draft does propose ID rewrite in BRs for packets from CEs having shared addresses. Reason, explained in the draft, is that if original IDs are kept unchanged for shared-address CEs, reassembly may be broken in destination end points. A discussion of this point, which so far had only been discussed verbally, is of course welcome. > instead of making the CE use the fragmented fragmentation (sic!) space > directly? Not understood. > > I think the fragmentation ideas are well worth considering btw. > >>> | MSS update | Y | N | >> >> (8) I found no reference to MSS in MAP-E, and no reference to MSS update in >> MAP-T. >> Did I miss them? > > RFC6145 mentions it at least. I don't think MAP-E should do anything on MSS, > in that case it would be part of the NAT function prior to encapsulation. > >>> | Complete IPv6 address / | Y | N | >>> | prefix | | | >> >> (9) Not sure what you mean by a complete IPv6 prefix. I see no functional >> limitation of 4rd-U with prefix lengths. > > ah, misspelling. MAP describes how to provision a complete IPv4 address or > IPv4 prefix. (not IPv6 of course). - Sec 5.1 says: "As far as mapping rules are concerned, the simplest deployment model is that in which the Domain has only one rule (the Default mapping rule). To assign an IPv4 address to a CE in this model, an IPv6 /112 is assigned to it comprising the BR /64 prefix, the V octet, a null octet, and the IPv4 address." Also, the use case of 5.3 uses full IPv4 addresses. I agree however that the text could make it clearer. - A Mapping rule that has Rule IPv4 prefix = 0 and EA-bits length < 32 assigns an IPv4 prefix. Cheers, RD BTW, could you use my e-mail address that works in Softwire, otherwise my responses get lost. Thanks. > >>> | Provisioned with DHCP | Y | Y | >>> +-------------------------------+----------------+------------------+ >>> >>> Table 1: A+P comparison >> > > cheers, > Ole > _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
