On Apr 13, 2011, at 11:23 PM, Dmitry Anipko wrote: > Hello Mark, > > I agree that if the 4rd IPv4 address is only used in such a way, that > applications cannot start use the address directly (such as e.g. perform > binding to the address assigned to an interface), then this issue doesn't > apply. > > However I'm not sure that the current draft makes clear that this is the only > intended use. For example, it defines CE as "a node.. it may be a host..", > instead of saying that CE is a function implemented in a host. Also, the > introduction in section 1 also does not include NAPT as a required element of > the solution (it says "The 4rd mechanism tunnels IPv4 over IPv6 using an > algorithmic mapping.."). > > Some existing implementations may be assigning the address used for NAPT to > an interface (and as long as the address is for the host exclusive use, an > implementation is able ensure such usage doesn't cause problems) - that's > what Windows ICS you mentioned actually does. > > With the current language, I don't think it is unlikely that implementers > will be tempted to assign a 4rd IPv4 address to an interface (e.g. with > intent to enable wider set of apps to work without a NAPT in the middle), and > if the spirit of the draft is that the IPv4 address assigned to the node by > 4rd should be only be used for CE function, performing NAPT, (or more > specifically, should not be made available for applications to bind) then I > think it may be useful to state it as such to guide implementers.
Then at least you and I agree. If 4rd becomes a WG item, this is the kind of change we should be able to affect in the draft with WG consensus. - Mark > > Thank you, > Dmitry > > -----Original Message----- > From: Mark Townsley [mailto:[email protected]] > Sent: Tuesday, April 12, 2011 1:04 PM > To: Dmitry Anipko > Cc: [email protected] > Subject: Re: [Softwires] sharing restricted addresses by hosts in 4rd > (draft-despres-intarea-4rd-01) > > > Hello Dmitry, > > My view is that 4rd is most easily understood if and only if it connects to a > CE function that is performing NAPT. The CE function may be in what is > traditionally considered a host, or in what is clearly a router. > > More specifically, a device that is forwarding packets from one interface > (virtual or otherwise) to another through a NAPT that has one interface with > IPv6 configured (via DHCPv6 or otherwise) as performing 4rd (which enables > dual-stack via a port-restricted IPv4 address for the NAPT using IPv6 as the > transport) then you a have a 4rd CE. That could be a "host" in that it is a > Windows PC with internet connection sharing for IPv4 turned on and hence > forwards packets between interfaces with a NAPT due to the IPv4-enabled > interface created when 4rd is configured. > > I would avoid anything that requires the host forwarding table to be altered > to accommodate 4rd. Instead, the NAPT function that is already present in a > small router or host configured to look like a router is modified to use a > set of ports that it is allowed to use when 4rd is enabled. > > - Mark > _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
