Re: Meta-issues: On the deprecation of the fragmentation function
RJ Atkinson <rja.lists@gmail.com> Wed, 10 July 2013 00:42 UTC
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Subject: Re: Meta-issues: On the deprecation of the fragmentation function
From: RJ Atkinson <rja.lists@gmail.com>
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Date: Tue, 09 Jul 2013 20:42:22 -0400
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On July 9th, Carsten Bormann wrote, in part: >>> But for one problem: adaptation layer fragmentation is >>> *transparent*, so there is no way for an application >>> to do the equivalent of PMTUD to avoid/minimize adaptation >>> layer fragmentation. >> On 10/07/2013 05:28, RJ Atkinson wrote: >> Good point. On 09 Jul 2013, at 16:50 , Brian E Carpenter wrote: > And you can't get round it. The decision to raise the minimum link > MTU from 576 to 1280 was not a change in principle; For IPv6, the specification of any minimum MTU might well have been the fundamental mistake here. Specifying a minimum MTU above 576 definitely was a mistake in practical terms of IPv6 deployability -- and some of us objected to the change at the time (giving examples of links that would be broken -- which have come true since). As you know already, IPv4 simply does not have any Minimum Link MTU. So it was probably over-specification for IPv6 to specify any minimum link MTU. For IPv4, RFC-791 says 576 actually was the size of buffer space that hosts had to have available for fragment reassembly. RFC-1122 agrees with RFC-791 and gives it the name EMTU_R ("Effective MTU to receive"). RFC-1122 further defines EMTU_S ("Effective MTU to send") and says: "... the IP layer SHOULD use EMTU_S <= 576 whenever the destination address is not a a connected network, and otherwise use the connected network's MTU." A bit later on, RFC-1122 also says: "Since nearly all networks in the Internet currently support an MTU of 576 or greater, we strongly recommend the use of 576 for datagrams sent to non-local networks." Again, this doesn't make 576 a minimum link MTU for IPv4. > The big change in principle was the abolition of on-path fragmentation. Well, at the moment, on-path fragmentation is not actually prohibited, as near as several implementers (including me) can tell, although it absolutely is never required to be supported by routers. Everyone agrees that on-path fragmentation by routers is generally undesirable. Everyone also agrees that a router, for example a backbone high-speed router, must not be forced to fragment anything -- for practical performance reasons that are widely understood. However, the IPv6 specs don't prohibit a router from choosing to fragment a packet in the way described in my earlier note in those circumstances. Such fragmentation is generally undetectable at present, except to the router that performs the fragmentation in order to transmit the IPv6 packet over a link having a smaller MTU. This difference between "not required" and "prohibited" is critical for IPv6 deployment over low-rate links having a smaller MTU size, as I outlined in my previous note within this thread. If a goal of this WG is to encourage deployment of IPv6 and transition from IPv4 to IPv6, then it would be best not to change the current status of fragmentation in IPv6 -- and it would be helpful to change the minimum Link MTU to a value lower than 1280 (or deprecate the Minimum Link MTU specification entirely, although that seems quite unlikely here now). I'd really like to see IPv6 get universally deployed. These particular changes are significant barriers to that happening and create perverse incentives either to stay with IPv6 forever or to build & deploy IPv6::IPv4 translational gateways (ugh). Cheers, Ran
- Re: draft-bonica-6man-frag-deprecate sthaug
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: Meta-issues: On the deprecation of the fragme… Carsten Bormann
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- FW: New Version Notification for draft-bonica-6ma… Ronald Bonica
- Re: FW: New Version Notification for draft-bonica… Arturo Servin
- Re: New Version Notification for draft-bonica-6ma… Mark Smith
- Re: FW: New Version Notification for draft-bonica… Tassos Chatzithomaoglou
- Re: FW: New Version Notification for draft-bonica… Simon Perreault
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- Re: RE: FW: New Version Notification for draft-bo… Ray Hunter
- Re: FW: New Version Notification for draft-bonica… joel jaeggli
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- RE: RE: FW: New Version Notification for draft-bo… Ronald Bonica
- Re: FW: New Version Notification for draft-bonica… Ray Hunter
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- Re: FW: New Version Notification for draft-bonica… Brian E Carpenter
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- Re: FW: New Version Notification for draft-bonica… Tore Anderson
- Re: FW: New Version Notification for draft-bonica… Mark Andrews
- RE: FW: New Version Notification for draft-bonica… Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… Glen Turner
- Re: New Version Notification for draft-bonica-6ma… George Michaelson
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- RE: New Version Notification for draft-bonica-6ma… Sheng Jiang
- Re: FW: New Version Notification for draft-bonica… Doug Barton
- RE: FW: New Version Notification for draft-bonica… Liubing (Leo)
- Re: FW: New Version Notification for draft-bonica… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Tore Anderson
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- RE: New Version Notification for draft-bonica-6ma… Ronald Bonica
- RE: New Version Notification for draft-bonica-6ma… Ronald Bonica
- Re: New Version Notification for draft-bonica-6ma… Ole Troan
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: FW: New Version Notification for draft-bonica… Marc Lampo
- Re: FW: New Version Notification for draft-bonica… Mark Smith
- Re: FW: New Version Notification for draft-bonica… Hagen Paul Pfeifer
- Re: FW: New Version Notification for draft-bonica… Hagen Paul Pfeifer
- RE: FW: New Version Notification for draft-bonica… Ronald Bonica
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- Re: New Version Notification for draft-bonica-6ma… joel jaeggli
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- RE: New Version Notification for draft-bonica-6ma… Sheng Jiang
- Re: New Version Notification for draft-bonica-6ma… George Michaelson
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… joel jaeggli
- RE: New Version Notification for draft-bonica-6ma… Ronald Bonica
- Re: FW: New Version Notification for draft-bonica… Brian E Carpenter
- Re: FW: New Version Notification for draft-bonica… Randy Bush
- Re: FW: New Version Notification for draft-bonica… joel jaeggli
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… George Michaelson
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… Geoff Huston
- Re: FW: New Version Notification for draft-bonica… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Bob Hinden
- Re: New Version Notification for draft-bonica-6ma… Glen Turner
- Re: New Version Notification for draft-bonica-6ma… Geoff Huston
- Re: New Version Notification for draft-bonica-6ma… Tore Anderson
- Re: FW: New Version Notification for draft-bonica… John Leslie
- RE: FW: New Version Notification for draft-bonica… Templin, Fred L
- RE: New Version Notification for draft-bonica-6ma… Christian Huitema
- Re: [6MAN] New Version Notification for draft-bon… Warren Kumari
- Re: New Version Notification for draft-bonica-6ma… Ole Troan
- Re: FW: New Version Notification for draft-bonica… Brian Jones
- Re: New Version Notification for draft-bonica-6ma… Randy Bush
- Re: New Version Notification for draft-bonica-6ma… Ole Troan
- Re: New Version Notification for draft-bonica-6ma… Randy Bush
- RE: New Version Notification for draft-bonica-6ma… Tony Hain
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- Re: New Version Notification for draft-bonica-6ma… Randy Bush
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Brian E Carpenter
- Re: New Version Notification for draft-bonica-6ma… George Michaelson
- Re: New Version Notification for draft-bonica-6ma… Brian E Carpenter
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Kevin Lahey
- RE: New Version Notification for draft-bonica-6ma… Tony Hain
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- RE: New Version Notification for draft-bonica-6ma… Sheng Jiang
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… Randy Bush
- Re: New Version Notification for draft-bonica-6ma… Mark ZZZ Smith
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… Hagen Paul Pfeifer
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- Re: draft-bonica-6man-frag-deprecate Hagen Paul Pfeifer
- Re: New Version Notification for draft-bonica-6ma… Fernando Gont
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- Re: New Version Notification for draft-bonica-6ma… Mark Andrews
- draft-bonica-6man-frag-deprecate Brian E Carpenter
- Re: New Version Notification for draft-bonica-6ma… Randy Bush
- Re: New Version Notification for draft-bonica-6ma… Fred Baker (fred)
- Re: New Version Notification for draft-bonica-6ma… Fernando Gont
- Re: draft-bonica-6man-frag-deprecate Marc Lampo
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- Re: draft-bonica-6man-frag-deprecate Antonios Atlasis
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- Re: draft-bonica-6man-frag-deprecate Antonios Atlasis
- RE: draft-bonica-6man-frag-deprecate Tony Hain
- Re: draft-bonica-6man-frag-deprecate Fred Baker (fred)
- Re: draft-bonica-6man-frag-deprecate Mark Andrews
- Re: draft-bonica-6man-frag-deprecate Karl Auer
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- Re: draft-bonica-6man-frag-deprecate Ole Troan
- Re: draft-bonica-6man-frag-deprecate Mark Andrews
- Re: New Version Notification for draft-bonica-6ma… Erik Nygren
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… james woodyatt
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… Brian E Carpenter
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Meta-issues: On the deprecation of the fragmentat… Fernando Gont
- Re: Meta-issues: On the deprecation of the fragme… Brian E Carpenter
- Re: New Version Notification for draft-bonica-6ma… Brian E Carpenter
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: Meta-issues: On the deprecation of the fragme… Hannes Frederic Sowa
- Re: New Version Notification for draft-bonica-6ma… Brian E Carpenter
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- Re: New Version Notification for draft-bonica-6ma… Doug Barton
- Re: Meta-issues: On the deprecation of the fragme… Antonios Atlasis
- Re: draft-bonica-6man-frag-deprecate Ole Troan
- Re: Meta-issues: On the deprecation of the fragme… C. M. Heard
- RE: draft-bonica-6man-frag-deprecate Templin, Fred L
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- RE: New Version Notification for draft-bonica-6ma… Templin, Fred L
- Re: Meta-issues: On the deprecation of the fragme… Francis Dupont
- Re: Meta-issues: On the deprecation of the fragme… Marc Lampo
- Re: Meta-issues: On the deprecation of the fragme… Fernando Gont
- Re: Meta-issues: On the deprecation of the fragme… Fernando Gont
- RE: Meta-issues: On the deprecation of the fragme… Manfredi, Albert E
- RE: Meta-issues: On the deprecation of the fragme… Manfredi, Albert E
- Re: Meta-issues: On the deprecation of the fragme… Mark Andrews
- RE: Meta-issues: On the deprecation of the fragme… RJ Atkinson
- Re: Meta-issues: On the deprecation of the fragme… Randy Bush
- Re: Meta-issues: On the deprecation of the fragme… Brian Jones
- Re: Meta-issues: On the deprecation of the fragme… Carsten Bormann
- Re: Meta-issues: On the deprecation of the fragme… RJ Atkinson
- Re: Meta-issues: On the deprecation of the fragme… Doug Barton
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- Re: Meta-issues: On the deprecation of the fragme… Doug Barton
- Re: Meta-issues: On the deprecation of the fragme… Carsten Bormann
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- Re: Meta-issues: On the deprecation of the fragme… RJ Atkinson
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- Re: Meta-issues: On the deprecation of the fragme… james woodyatt
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- Re: Meta-issues: On the deprecation of the fragme… james woodyatt
- RE: Meta-issues: On the deprecation of the fragme… Ronald Bonica
- RE: Meta-issues: On the deprecation of the fragme… Templin, Fred L
- Re: Meta-issues: On the deprecation of the fragme… Brian E Carpenter
- RE: "Deprecate" Templin, Fred L
- Re: "Deprecate" Mark Andrews
- Re: "Deprecate" Francis Dupont
- Re: "Deprecate" RJ Atkinson
- Re: "Deprecate" RJ Atkinson
- RE: "Deprecate" Templin, Fred L
- RE: "Deprecate" Templin, Fred L
- RE: "Deprecate" Templin, Fred L
- RE: "Deprecate" Templin, Fred L
- RE: "Deprecate" C. M. Heard