> On 2 Mar 2021, at 14:21, Liguangpeng (Roc, Network Technology Laboratory) > <[email protected]> wrote: > > Hi Stewart, > > Backwards compatible should be always good thing for investment protection. > Except “could put your new packet into a IPv6 parser”,
> another possible approach is the last new forwarder translate new packet to > IPv6 packet (may encapsulate new fields in extension header), and passthrough > in IPv6 domain. > Then the first new forwarder adjacent to IPv6 forwarder must recognize IPv6 > encapsulation and traversing all extension headers to form new packets if > next hop is new forwarder. If you could write down the two formats and describe the mappings that would make people reading this thread feel a lot more comfortable that this is feasible. It would also enable everyone to understand any limitations and constraints with the approach you propose. - Stewart > Guangpeng Li > > From: Stewart Bryant [mailto:[email protected] > <mailto:[email protected]>] > Sent: Tuesday, March 2, 2021 9:53 PM > To: Toerless Eckert <[email protected] <mailto:[email protected]>> > Cc: Stewart Bryant <[email protected] > <mailto:[email protected]>>; Jiayihao <[email protected] > <mailto:[email protected]>>; > [email protected] > <mailto:[email protected]>; int-area > <[email protected] <mailto:[email protected]>>; > [email protected] > <mailto:[email protected]> > Subject: Re: [Int-area] Using ISO8473 as a network layer to carry flexible > addresses > > > > > On 1 Mar 2021, at 15:33, Toerless Eckert <[email protected] > <mailto:[email protected]>> wrote: > > I really don't understand why the IPv6 world has not understood how the most > easy way > to allow for the applicability of IPv6 to grow (especially beyond "just more > addresses thn IPv4") > would be to come up with a backward compatible encap on the wire that would > support additional > address lengths. > > Toerless > > I don’t think there is a simple backwards compatible approach, but we can > probably do more than we do today. > > Backwards compatible means that you could put your new packet into a IPv6 > parser and it would correctly forward the packet as if nothing had changed. > > You could I suppose put a well known IPv6 address in the IPv6 header and put > the real address in an extension header, perhaps including the pointer to the > address in the suffix of the IPv6 address to make finding the EH much faster, > but I am not sure that is backwards compatible. > > I suppose it might be able to do a bit better if the address in the IPv6 DA > was the DA of the egress router and old routers did best effort to the egress > and newer routers knew to take a look at the extension header for more detail. > > I think that it is worth thinking about how we could do better than we do > today, but I think we need to be careful with the term backwards compatible. > > - Stewart
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