Hi, > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Carsten Bormann > Sent: Tuesday, July 09, 2013 3:08 PM > To: Manfredi, Albert E > Cc: [email protected] List > Subject: Re: Meta-issues: On the deprecation of the fragmentation > function > > > First is, the change of MTU was not one of 576 to 1280. > > I think he was talking about changing the minMTU of Steve Deering's > Simple IP from 576 first into the mistaken 1500 and then into 1280 in > the process of turning it into IPv6. > http://tools.ietf.org/html/draft-deering-sip-00 > (BTW, is that process documented anywhere? RFC1710 doesn't seem to > mention the MTU.) > > > The other point is, I don't see how transparent adaptation layers are > an issue at all? I don't think anyone is saying that it's impossible to > transmit IPv6 over ATM cells? Or are they? > > The problem comes up where the transparency is a leaky abstraction > (http://en.wikipedia.org/wiki/Leaky_abstraction). > > For ATM, the abstraction was not very leaky as the performance impact > of sending an MTU-size packet was negligible (at least for the more > recent cases of ATM). > > For the constrained networks Ran and I are interested in, the > performance impact of adaptation layer fragmentation can be > significant, and application layer protocols that get to choose their > packet sizes can benefit quite a bit if they know this fragmentation is > taking place and what packet sizes are the thresholds.
I already said in the other thread that aviation and tactical military links are examples of slow RF links where even as much as 1280 is asking a lot. About size issues, the first IPv6 spec (RFC1883) had a 576 minMTU, and that was changed to 1280 during publication of RFC2460 based on Steve Deering's Nov. 1997 proposal on the IPng list. Other sizes of interest: 68 - real IPv4 minMTU 576 - de-facto IPv4 minMTU (the one everyone assumes) 576 - real IPv4 minMRU 576 - old IPv6 minMTU 1280 - current IPv6 minMTU 1500 - current IPv6 minMRU 1500 - de-facto IPv4 minMRU (the one everyone assumes) 1500 - legacy Ethernet MTU 2048 - proposed new IPv6 minMRU Fred [email protected] > Please read the short ALFI draft for more background. > http://tools.ietf.org/html/draft-bormann-intarea-alfi-03 > http://www.ietf.org/proceedings/85/slides/slides-85-intarea-1.pdf > > Grüße, Carsten > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > [email protected] > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
