Le 2012-03-19 à 10:21, Maoke a écrit : > > > 2012/3/19 Rémi Després <[email protected]> > > Le 2012-03-19 à 09:16, Maoke a écrit : > >> >> >> 2012/3/16 Rémi Després <[email protected]> >> Maoke, >> >> Let me try a more complete picture than before: >> >> >> A1 -----. >> RFC6145-host| .-- 4rd BR --. >> | | | >> A2 -----:--(v6net)--: :--(v4 Internet)--- B >> 4rd-CE | | | UDP Lite appli >> >> (no IPv4 @) | '-- NAT64+ --' >> | >> A3 -----' >> 4rd-CE >> (IPv4 @, shared or not) >> >> >> NAT64+ is supposed to have a bindings for UDP Lite, either only for 4rd IPv6 >> addresses (the minimum), or also for native IPv6 addresses (the complete >> upgrade, with UDP-Lite checksum adjustment for these addresses) >> >> Connectivities I get are: >> A2 => B (via NAT64+) >> A3 <=> B (via 4rd BR) >> (There is no A1-B connectivity) >> >> A2 is IPv6-only, right? > > There seems to be a misunderstanding on what is IPv6-only. > a) A2 is dual stack. Being a CE node, it supports IPv4 applications, and > typically includes a NAT44. > b) Its IPv6 prefix matches neither a CE nor the BR mapping rule, it has no > assigned public IPv4 address (even shared). > c) Because it has received a NAT64+ mapping rule, it knows it can tunnel IPv4 > packets to the NAT64+. > > >> if so, let me go down. > > Not so => doesn't apply. > (Yet some further comments below) > > RD > > >> >> >> Anything missed? >> >> >> Other detailed comments follow. >> >> Le 2012-03-16 à 01:59, Maoke a écrit : >> >>> >>> >>> 2012/3/15 Rémi Després <[email protected]> >>> >>> Le 2012-03-15 à 14:47, Maoke a écrit : >>> >>>> >>>> >>>> 2012/3/15 Rémi Després <[email protected]> >>>> >>>> Le 2012-03-15 à 11:45, Maoke a écrit : >>>> >>>>> i understand NAT64 makes translation between arbitrary IPv6 address to >>>>> arbitrary IPv4 address. i don't understand how you make CNP in any IPv6 >>>>> address. >>>> >>>> >>>>> in other words, we cannot limit NAT64 stateful service only serve those >>>>> IPv6 addresses with CNP. >>>> >>>> That's no the case at all(!). >>>> A NAT64+ is a *backward compatible* extension of NAT64 (everything that >>>> worked before still works completely unchanged). >>>> >>>> The draft says: >>>> "NAT64+: An ISP NAT64 of [RFC6146] that is upgraded to support 4rd >>>> tunneling when IPv6 addresses it deals with have the 4rd-IPv6-address >>>> format." >>>> >>>> >>>> this phrase is not understood yet. do you mean using 4rd-IPv6-address >>>> format for stateful translation service? >>> >>> Yes (but, &s said, only for CE nodes that are 4rd capable (with the >>> advantage of better IPv4 transparency between CEs and NAT64+ than between >>> RFC6145 and NAT64). >>> >>>> please draw an example of A <---> B communication as i did for >>>> clarification. >>> >>> Here is an example scenario: >>> >>> v4appli-BIH ----. => A>B NOK (because, according to RFC6535, BIH uses >>> RFC6145) >>> A1 | >>> :----(v6net)----- NAT64+ ---(IPv4 Internet)--- Server >>> | UDP-lite UDP-lite >>> v4Appli-4rdCE --' capable B >>> A2 => A-B OK >>> >>> >>> yes, BIH uses RFC6145 that doesn't claim supporting UDP-Lite. but exactly >>> speaking, if the "not support" means passing-it-through without checksum >>> adjustment, A --> B is fine because neither BIH nor NAT64+ does nothing >>> with the L4, right? >> >> A NAT64 that supports UDP Lite MUST update checksum for hosts that have >> native IPv6 addresses. >> That's why A1 => B doesn't work unless the NAT64 recognizes which packets >> are those of IPv4 applications in DS hosts. >> >> A1 -> B doesn't need stateful NAT64 but stateless service is enough. well, >> stateful is also ok. it is true NAT64 supporting UDP-Lite must update >> checksum. >> >> >>> B --> A is a question mark, if we use the NAT64+ which does nothing with >>> the L4 checksum, it is also not a problem. >> >> >>> however, if we use, as you mentioned before, an UDP-Lite-aware update of >>> RFC6146, that may updates the checksum while the BIH doesn't know that. >> >> Note that an upgrade of RFC6146 isn't needed for A NAT64 (and NAT64+) to >> support more protocols than the two required by the RFC. It is just an >> extension which cannot break anything (backward compatible). >> >> confusing. upgrade vs. extension?? >> >> >> >>> >>> my point here is: what is the use case with the details of addressing? if >>> and only if A1 or A2 is configured with an RFC6052 or a MAP or a 4rd-U >>> address while NAT64+ has a pool of checksum-neutral IPv6 address to serve B >>> for the communications, A1 BIH or A2 CE may do the stateless processing >>> successfuly. if NAT64+ hasn't such a address pool for B, things will fail >>> because only one among src and dst is checksum-neutral. >> >> Sec 4.4 (8) says that a CE that targets an off-domain IPv4 address reaches >> the NAT64+ at this IPv6 address: >> >> +-------------------------------+---+---+-------------+------+ >> | NAT64+ IPv6 prefix |"u"| 0 |DST IPv4 add.| CNP | >> +-------------------------------+---+---+-------------+------+ >> : 64 : 8 : 8 : 32 : 16 : >> >> In the reverse direction, and for the same IPv4 address, it is the same IPv6 >> address that must be synthesized by the NAT64+. >> >> this address is used for A2 or used for B? if you mean B, then may i >> conclude that NAT64+ is serving between A2 (native IPv6 address with 4rd-U >> CNP) and B (synthesized by NAT64+ into another IPv6-converted address having >> CNP)? if i can, may i further conclude that NAT64+ serves only for the case >> where A2 has the 4rd-U-style address? > > Let me repeat that: > - NAT64+ works as a NAT64 for addresses that aren't 4rd-u style. > - The only difference is that NAT64+ has a plus for addresses that are those > of 4RD-u CEs (better IPv4 transparency). > > accepted. but i have pointed out the "better transparency" has some cost and > uncertaity up to now (see another thread). > > > >> if the A2 is configured with any IPv6 address, for example, address with the >> autoconfigured EUI64 IID, it is out of the scope of the NAT64+, right? >> >> if so, i do really suggest you call it NAT64- instead of NAT64+ because >> NAT64 can also serve hosts with any native IPv6 address to connect with an >> IPv4 peer. >> >> your answer below didn't respond my question, sorry. for example (in the use >> case of NAT64 instead of NAT64-), A2 has native IPv6 address >> 2001:db8:1234:5678:208:1fff:fe4d:606e while B is 192.32.77.50. the CE might >> synthesize an IPv6 address for B, with the NAT64+ prefix and the 0xc0204d32 >> and a CNP embedded, say B', and let A2 connect to B' through IPv6; however, >> when this packet goes through the NAT64+, > >> because only B' is checksum-neutral while A2 is not, > > If the /64 of A2 is 2001:db8:1234:5678::/64, its 4rd IPv6 address is, per Fig > 6, 2001:db8:1234:5678:3000::<CNP> > It IS checksum neutral. > > well, it is saying A2 must have the 4rd address in order to get the benefit > of NAT64-, right?
(*) For native IPv6, it has whatever address applies (that of your example is OK). Its CE is reached with all destination addresses starting with the site /64 followed by with the V octet. > i have typed "for example (in the use case of NAT64 instead of NAT64-), ..." > as the prerequisite of the above discussion. let me have the following > propositions: > > a. NAT64 suitable for any case no matter A2 is assigned with any kind of > address, but currently only works for TCP and UDP. Yes (but with the DF bit transparency limitation that is avoided in case of NAT64+) > b. NAT64+ works for the cases where A2 is assigned with a special type of > IPv6 address with the CNP, without need to update checksum for any L4 > protocols. > c. NAT64+ works like: > if A2 has a V-CNP-address, then it doesn't update the checksum for any L4 > protocols; > if A2 has any other kind of native IPv6 address, then NAT64+ works just > like NAT64, updating the checksum but also currently only works for TCP and > UDP. > > i think we are common that a. is true, right? Right, with the caveat above. > do you mean c. instead of b. ? NAT64+ works like NAT64 in all cases, except for 4rd CEs that: - received a NAT64+ mapping rule - have IPv6 prefixes from which no IPv4 address can be derived. For them, better transparency is achieved by replacing double RFC6145 translation by a Reversible header mapping. That's IMHO clear enough, especially with the (*) above which clarifies AFAIK which native and 4rd IPv6 addresses are used by CEs. Cheers, RD > > thanks, > maoke > > > >> NAT64+ passing it without L4 checksum adjustment will make B receive a >> packet with wrong checksum, for any L4 protocols. >> >> the above example works well for TCP and UDP with today's NAT64, without >> limitations on A2's address. >> >> - maoke >> >> This is I suppose implicit, but it can advantageously be made explicit in >> the draft. >> Thanks. >> >> >>>> Because 4rd IPv6 addresses of CEs are distinguishable from all other IPv6 >>>> addresses (due to the V octet), NAT64s are concerned with CNPs ONLY for >>>> addresses that actually are 4rd CE addresses. >>>> >>>> >>>> we need to make sure if the NAT64s make both src and dst addresses >>>> checksum-neutral. >>> >>> Correct, iff the host address has the V octet. >>> >>> 1. without the V-octet, CE and NAT64 can also distinguish the 4rd-CE >>> addresses from others. >> >> True, but while testing the V octet is sufficient in 4rd, the NAT64 has in >> MAP to process mapping rules to find for null subnet IDs whose lengths >> depend on which mapping rule applies. >> That's IMHO one instance where the V-octet potential is clear. >> >> >>> 2. even with the V-octet, do you mean B's IPv4 address also translated (by >>> the NAT64+) to a CNP-and-V-containing IPv6 address? >> >> Yes (see above). >> >>> if 2 is true, why you use stateful NAT64+ here for B rather than a >>> stateless one? >> >> Because we consider hosts that are not assigned any public IPv4 address, >> even shared. >> >>> if 2 is not true, then the NAT64 can use any arbitrary IPv6 address for B's >>> communications, and such a case results only A's mapped address is >>> checksum-neutral, and thus anyway L4 adjustment is needed. >>> >>> if 2 is true, i do suggest you naming NAT64+ as NAT64- instead, because >>> NAT64 doesn't have the limitation on the IPv6 address pool in use. >> >> Suggestion not retained ;-). >> What you call the IPv6 address pool isn't a reserved pool: as explained >> above, NAT64+ synthesizes its IPv6 source addresses using its unchanged /64 >> prefix. >> >> >>> 3. RFC6535 states, explicitly, "Use of BIH together with a NAT64 is NOT >>> RECOMMENDED [RFC6180]" (but the above technical discussion can omit this >>> for the time being). >> >> Right. >> >> RD >> >> >> >> >> >>> >>> - maoke >>> >>> >>>> i cannot imagine what the use case is. please specify! >>> >>> Hope the picture above helps. >>> >>> RD >>> >>> >>> >>>> >>>> - maoke >>>> >>>> >>>> >>>> RD >>>> >>>> >>>>> - maoke >>>>> >>>>> 2012/3/15 Rémi Després <[email protected]> >>>>> >>>>> Le 2012-03-15 à 10:59, Rémi Després a écrit : >>>>> >>>>> > Maoke, >>>>> > >>>>> > Thanks for this question. >>>>> > This subject being new, I take it on a new thread. >>>>> > >>>>> > 2012-03-15 10:38, Maoke: >>>>> > ... >>>>> >> i didn't understand the how the stateful NAT64 benefits from CNP. >>>>> > >>>>> > The point is that if a NAT64 is upgraded to support 4rd-u tunnels (thus >>>>> > becoming a NAT64+) it can take IPv6 payloads as valid IPv4 payloads. >>>>> > Any protocol that this NAT64 supports is then supported e2e for 4rd-u >>>>> > CEs >>>>> > These CEs need not being dependent on which NAT64 supports which >>>>> > protocols. >>>>> > >>>>> > Note that the NAT64 doesn't need to have CNP code. It just happens that >>>>> > host IPv6 addresses it sees are checksum neutral. (Thus, IPv6 and IPv4 >>>>> > payloads are the same for all protocols that have ports at the same >>>>> > place as TCP/UDP/..., and the same checksum algorithm) >>>>> >>>>> Oops. >>>>> This is only true for the IPv6 host address. To construct an IPv6 address >>>>> when transmitting to a 4rd-u CE, the NAT64 should compute a CNP. (This >>>>> is to maintain the property that that middleboxes can treat tunnel >>>>> packets as valid IPv6 packets. Not a big deal, but necessary). >>>>> Sorry for having hastily added this sentence. >>>>> >>>>> RD >>>>> >>>>> > >>>>> > RD >>>>> > >>>>> > >>>>> > >>>>> > >>>>> > _______________________________________________ >>>>> > Softwires mailing list >>>>> > [email protected] >>>>> > https://www.ietf.org/mailman/listinfo/softwires >>>>> >>>>> >>>> >>>> >>> >>> >> >> > >
_______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
