Mebbe. I confess I didn't study the details of the competing proposals at the time because I was confident the people who were heavily involved surely had things under control. Steve On Oct 10, 2010, at 6:41 PM, Dave CROCKER wrote: > > > On 10/10/2010 2:51 PM, Steve Crocker wrote: >> A compatible solution would have been better, but I don't think IPv4... -- >> were designed in a way that permitted a compatible extension. > > > Oh? > > Perhaps: > > 1. Adopt an IPv6 as Steve Deering originally designed it[1]: A basic upgrade to the IPv4 header, with more address bits, an extensibility mechanisms for adding fields later, and removal of some bits that weren't needed. > > 2. Define the IPv6 address space as the IPv4 address space, with all zeroes for the higher bits. (In other words, defer more interesting schemes until later.) > > 3. Design header translation devices to map between the two formats. > > 4. Start fielding these implementations. (That could have started by 1994 or so.) > > The "gateways" between v4 and v6 would initially be notably for having almost no work to do and of not losing any information. In particular, barely qualifies as a "dual" stack. > > With this approach, "incompatibility" between v4 and v6 would only occur when additional addresses, beyond v4's limitations, start to be assigned. > > We must deal with the current reality and make it work, but historical considerations need to factor in the ambitions that dominated during the many years of design. > > The community got ambitious in a fashion that smacked of the overreaching that is often called second system syndrome (although counting the Arpanet, this was really a third system...) > > d/ > > [1] http://tools.ietf.org/html/draft-deering-sip-00 > -- > > Dave Crocker > Brandenburg InternetWorking > bbiw.net _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf