Hi Joe, > -----Original Message----- > From: Joe Touch [mailto:[email protected]] > Sent: Thursday, May 26, 2016 9:34 AM > To: Templin, Fred L <[email protected]>; Tom Herbert > <[email protected]> > Cc: [email protected] > Subject: Re: [Int-area] Call for adoption of draft-xu-intarea-ip-in-udp-03 > > > > On 5/26/2016 9:16 AM, Templin, Fred L wrote: > >>>> There is an existing solution to the same problem. GUE allows > >>>> encapsulation of IPv4 and IPv6, as well as other IP protocols (the GUE > >>>> header indicates encapsulated protocol by IP number). The only > >>>> material between GUE encapsulation of IP and IP in UDP is additional > >>>> four byte header and associated processing of that. I don't think > >>>> we've seen a use case where avoiding that overhead is critical > >>>> motivation. > >>> I thought at one time we had come up with an idea for omitting the GUE > >>> header when the payload is a plain IPv4/IPv6 packet. There was a check > >>> of the first four bits following the UDP header to see if they encoded the > >>> value '4' or '6'. Did that not make it into the draft? > >>> > >> Yes, we had come up with the idea and I have implemented the > >> prototype. It is not in the draft. I believe the only discernible > >> benefit we could identify was that it saves 4 bytes of overhead. The > >> major drawback is that this only works specifically for IPv4 and IPv6. > > I don't see the drawback; I think those two IP protocol versions could > > carry us forward into the forseeable future. Are you thinking there > > could be another IP version on the near term horizon? > > IMO, this is a bad idea unless the protocol is specifically limited to > having IP as a payload. Otherwise, there's no way to ensure that some > other protocol won't start off with those values.
Tom's proposal unambiguously differentiates raw IPv4 and IPv6 from all other encapsulations. If it is raw IPv4 or IPv6, the GUE 4-byte header is not present. Otherwise, the GUE 4-byte header is present. Thanks - Fred > In particular, ICMP for IPv4 isn't an IP packet but has no rule about > the first 4 bits. That field ought to be large enough to handle any > protocol that might need to share the path with IP. > > Joe _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
