+1 - All of RJ's comments. There has to be a solution that not only allows for but encourages IPv6 deployment, not prevents it. -- Brian
On Tue, Jul 9, 2013 at 11:02 AM, RJ Atkinson <rja.li...@gmail.com> wrote: > All, > > I think everyone agrees that intermediate fragmentation > (e.g. by routers having high-speed links in the middle of the path) > can be problematic,and that is why IPv6 does NOT require that > (i.e. RFC-2460 says that the "DF" bit is invisible but always > set for IPv6). > > That noted, I agree very much with Fernando Gont's > comments on 5th July 2013 that IPv6 fragmentation in > end systems ought NOT be deprecated -- and I find his > reasoning compelling. > > > (SEPARATELY) > > Not all deployed links are built out of wired/wireless > Ethernet or SONET. The assumption that everything is either > Ethernet or SONET (or perhaps WDM) is a bit of a "First > World" assumption and puts lesser-developed countries/regions > at a significant disadvantage for Internet access. > > Frankly it is embarrassing for IETF participants to make > such an assumption (i.e. that all links are Ethernet, > SONET, WDM, or better). > > While it is fine to optimise so that Ethernet or SONET links > have great performance, for example by eliminating the > requirement for backbone routers to fragment packets, > we ought to retain the ancient "IP OVER EVERYTHING" mantra > that has served the Internet (and ALL regions of the world) > so well for so many years now. > > I know of a number of link technologies that simply can't > support the existing 1280 byte minimum IPv6 MTU. Links > with the lower MTU overwhelmingly are relatively low speed > wireless links (everything in the gamut from HF radio > to SATCOM). My concerns about this have been expressed in > IPv6 WG meetings dating back to the early 1990s, as IETF > meeting minutes show. All the data available to me indicates > that these lower-speed (and smaller MTU) links are NOT going away. > > For HF radio links, link transmission speed is usually > measured in Kbps, with some deployed IPv4/HF links today > running as low as 2.4 Kbps. VHF and UHF line-of-sight > links tend to be much faster than HF, but are still well > below the slowest modern Ethernet link (i.e. 10 Mbps). > > The IPv6 concept of adding a special link-specific > fragmentation/reassembly protocol layer has never been > practical. By definition, these links have severe bandwidth > limitations already. I've seen multiple instances where > specialised routers that are connected to these LOW speed > links insert IPv6 Fragmentation Headers and perform > intermediate fragmentation to get IPv6 packets through > such links. In these special cases, there is no performance > issue because these wireless links have such low data rates. > > A result of deprecating the IPv6 Fragmentation Header will be > that such links will be running IPv4 *forever*. This is > the opposite of encouraging IPv6 transition -- it is preventing > IPv6 transition. It also probably requires the ongoing deployment > of IPv6::IPv4 protocol translation gateways -- and also > probably inhibits Internet deployment outside of "1st World" > countries. > > Sigh. > > > Deprecating IPv6 Fragmentation Header and related end-system > support is going to harm users and inhibit transition to IPv6. > > > PLEASE, PLEASE, let us NOT go there. > > > Sincerely Yours, > > Ran Atkinson > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- >
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