> -----Original Message----- > From: Brian E Carpenter [mailto:brian.e.carpen...@gmail.com] > Sent: Wednesday, June 01, 2016 4:01 AM > To: Xuxiaohu; Joe Touch > Cc: joel jaeggli; Fred Baker (fred); Wassim Haddad; int-area@ietf.org > Subject: Re: [Int-area] Call for adoption of draft-xu-intarea-ip-in-udp-03 > > On 31/05/2016 20:13, Xuxiaohu wrote: > > > > > >> -----Original Message----- > >> From: Brian E Carpenter [mailto:brian.e.carpen...@gmail.com] > >> Sent: Tuesday, May 31, 2016 4:46 AM > >> To: Joe Touch > >> Cc: joel jaeggli; Xuxiaohu; Fred Baker (fred); Wassim Haddad; > >> int-area@ietf.org > >> Subject: Re: [Int-area] Call for adoption of > >> draft-xu-intarea-ip-in-udp-03 > >> > >> And being pedantic... > >> On 31/05/2016 06:12, Joe Touch wrote: > >>> > >>> > >>> On 5/29/2016 4:23 PM, joel jaeggli wrote: > >>>>>> I.e., you MUST support source fragmentation at the ingress at the > >>>>>> outer > >>>>>> IPv6 layer (because UDP doesn't have support for fragmentation > >>>>>> and reassembly). If you make this requirement, you can handle > >>>>>> IPv6 over the tunnel. > >>>> Yeah I don't support it for this reason. getting IP fragments back > >>>> together in the same place a reassembled is hard is in some cases > >>>> especially when you hash. (see frag drop) given alternatives that > >>>> better address such situations it seems hard to justify. > >>> > >>> If you intend to support recursive IP tunneling* and believe that IP > >>> has a minimum MTU, then you have to accept reassembly. > >> > >> If you intend to support recursive datagram tunneling and believe > >> that any path has a minimum MTU, then you have to accept reassembly. > >> > >> This is physics, and nothing to do with design details. > >> > >> (Something I discovered in about 1983, when implementing OSI/CLNP at > >> CERN over a homebrew network with 128 byte packets.) > > > > Reassembly on the tunnel egress may be acceptable at that old time. However, > due to the considerable improvement in network bandwidth capability, the > practice acceptable at the old time may have become outdated today. > > I don't understand what network capacity has to do with the physical and > mathematical fact that packets larger than N bytes will not fit into a packet > limited to N bytes.
This article (http://learning.nil.com/assets/Tips-/The-Never-Ending-Story-of-IP-Fragmentation.pdf) may be useful for you to understand why network capability is a key factor to be considered for fragmentation and reassembly on routers (here routers are not software routers or CPU-only routers which were dominant in the old time). Of course, you could also have a look at the current fragmentation and reassembly implementations of major router vendors if you believed that article is a little bit old. Xiaohu > That was true in 1983 and will still be true in 2083. > > Brian > > > See the MAP implementation experience shared by Ole recently. > > > > Xiaohu > > > >> Brian > >> > >>> > >>> Joe > >>> > >>> * where "recursive IP tunneling" is IP in [zero or more other > >>> protocols] in IP. > >>> > >>> _______________________________________________ > >>> Int-area mailing list > >>> Int-area@ietf.org > >>> https://www.ietf.org/mailman/listinfo/int-area > >>> _______________________________________________ Int-area mailing list Int-area@ietf.org https://www.ietf.org/mailman/listinfo/int-area
