On 5/5/2015 11:04 AM, Templin, Fred L wrote: > Hi Joe, > >> -----Original Message----- >> From: Joe Touch [mailto:to...@isi.edu] >> Sent: Tuesday, May 05, 2015 10:54 AM >> To: Templin, Fred L; Xuxiaohu; Donald Eastlake; tr...@ietf.org >> Cc: n...@ietf.org; int-area@ietf.org; s...@ietf.org >> Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip >> >> >> >> On 5/5/2015 9:39 AM, Templin, Fred L wrote: >>> Hi Joe, >> .. >>>> IP in UDP adds only port numbers and an Internet checksum. >>>> >>>> That doesn't address fragmentation; if outer fragmentation is assumed, >>>> IPv4 needs to be rate-limited to avoid ID collisions and the Internet >>>> checksum is insufficient to correct those collisions. >>> >>> Right - that is why we have GUE. But, when these functions are not >>> needed GUE can perform header compression and the result looks >>> exactly like IP in UDP. >> >> That seems impossible. > > Not impossible - Tom Herbert provided the solution: > > http://www.ietf.org/mail-archive/web/int-area/current/msg04593.html
That is allocating bits (or bit patterns) from the IP header. The solution provided - to check for 0x01 - is incorrect. IP can have versions that include 0x10 and 0x11. The only solution would be to say that if the first three bits were 0, then it's not an IP packet - but that would require reassigning 0x0000 and 0x0001 for GUE purposes. Although that's possible, I don't see why we would allocate IP versions to GUE message types. Joe _______________________________________________ Int-area mailing list Int-area@ietf.org https://www.ietf.org/mailman/listinfo/int-area
