Le 29 nov. 2011 à 19:47, Ole Troan a écrit : > Remi, > > to summarize my view: > - the 4rd-u proposal (including the changes you plan) are well understood
Except that you believe it is a translation solution (which means AFAIK RFC6145 based), while it isn't. > - the main ideas from 4rd-* are already incorporated into MAP Except the fact that, with the two variants of MAP, IPv6 ACLs, web caches, DCCP transparency, and DF-bit transparency cannot be simultaneously available. > - 4rd-u is a slightly different way of doing translation (calling mapping > doesn't change that fact) > go to behave to argue if yours is better than what was specified there. Let us ask Dan Wing whether he believes it would fit in Behave. > - I think it is the wrong thing for this working group to encourage > development of yet another solution, when we already > have many. Are you missing that it is proposed two replace two standards by just one? > - I would also like to see one solution, my choice is encapsulation. Well understood. But this is AFAIK ignoring arguments of double-translation proponents. > given that all the building blocks already exist, 4rd-u has large building blocks that are common with encapsulation, and small differences that are AFAIK simple to implement and easy to deploy. > I > would expect we'll see translation in the wild too, whatever we choose to > do in the IETF. ref: NAT464. We will see deployments of NAT64/DNS64, as standardized by Behave, I agree. But stateless NAT464 doesn't need to be standardized if both DS-lite and 4rd-U exist. > I really hope this is the last I'll ever write on this topic. This depends on you more than on anything else. RD > cheers, > Ole > > > On Nov 29, 2011, at 19:11 , Rémi Després wrote: > >> Le 29 nov. 2011 à 17:15, Ole Troan a écrit : >> >>> Remi, >>> >>>> For those who attended the Softwire session in Taipei, please note that >>>> the serious objection against 4rd-U expressed by several participants >>>> during the meeting has been, soon after, acknowledged to be invalid >>>> (www.ietf.org/mail-archive/web/softwires/current/msg03281.html). >>>> Also, other (less important) objections have been answered in >>>> www.ietf.org/mail-archive/web/softwires/current/msg03284.html, without >>>> reaction so far. >>> >>> I do not think that's a fair representation. >> >> It was intended to be one, and is still believed to be so (see below) >> >>> the main objection to 4rd-u is that it is 'just another translation' >>> solution. >> >> a) >> That's not what I heard during the meeting. >> Both Mark Townsley and Dave Thaler, taking for granted your statement that >> checksum-neutral addresses of 4rd-U would cause "address spray", said firmly >> that 4rd-U should be rejected because it wouldn't work. >> >> In my understanding, not working is a show stopper, which I call a "main >> objection". >> >> b) If your main objection is that 4rd-U would be 'just another translation', >> it is ALSO invalid. >> If you have read my answer to your list of objections, you should know that >> 4rd-U is a reversible-header-mapping solution, and as such is based on >> neither translation nor encapsulation. (actually a tunnel closer to >> encapsulation in my understanding). >> >> >>> how many do we need? >> >> Many consider that, if there is the choice, ONE standard is better than >> several. >> >> The point is that 4rd-U combines advantages of double translation and >> encapsulation with only a slightly different tradeoff between optimizations >> of header-length and processing time. >> >> Doubts are legitimate as long as the specification is incomplete, but that's >> why more work is needed. >> >> >>> it doesn't appear to offer any benefits compared to the already specified >>> solution. >> >> Which solution? (So far, there are two in the pipe - translation and >> encapsulation.) >> Meeting requirements of both solutions is AFAIK a benefit. >> >> >>> as it stands it will just result in 3 ways of doing the same thing, instead >>> of 2. >> >> Different view on this. >> Three standards would make no sense. >> >> >>> the topic discussed in softwires, wasn't the main objection. as far as I >>> can see, "checksum neutrality" does not offer any advantages over >>> incrementally updating the L4 checksum. >> >> Again, commenting my previous answer to your list of objections would be be >> more constructive than repeating that 4rd-U doesn't do anything without >> arguing on substance. >> >> Since there is no obligation to comment, please refrain from criticizing a >> solution without commenting previous answers made for you. >> >> >>> every node doing this will have to look into the L4 header anyway. >> >> Sure. IPv4 address sharing implies _looking_ at port fields (true also for >> encapsulation). >> >> But this doesn't imply that L4 data need to be modified, especially if >> these modifications need to depend on whether the protocol is TCP UDP, DCCP, >> etc. >> Encapsulation and reversible header mapping don't care about this, which is >> one of their virtues. >> >> Cheers, >> RD >> > _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
