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? 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. 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? do you mean c. instead of b. ? 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 >>>>> >>>>> >>>> >>>> >>> >>> >> >> > >
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