CURRENT_MEETING_REPORT_ Reported by Jeffrey Mogul/DEC AGENDA 1. Report on current draft (Mogul/Deering) 2. Obtain consensus on approach 3. Focus on details 4. Schedule for standardization MINUTES This was the third meeting of the MTU Discovery Working Group. Jeff Mogul started with a review of where we had been in the past 5 months, including all the failed approaches. He then presented the current proposal, originated by Steve Deering. Summary: send all packets with the DF bit set. Routers that cannot forward these packets return a slightly modified ICMP message that indicates the appropriate MTU. (Current routers return ``0'' in the field meant for this purpose.) The sending host revises its estimate of the Path MTU, and retransmits the dropped datagram. There was no objection to the basic design. Some discussion ensued concerning details of the implementation and the relation between Path MTU discovery and transport protocol actions. This design solves many problems with the previous designs, especially because it is compatible with existing hosts and routers, and is quite simple to implement. ACTION ITEMS 1. Jeff Mogul and Steve Deering will change some details in the current draft and submit it as an Internet Draft. 2. The Router Requirements working group should be notified that we no longer care how fragmentation is done, since we don't rely on the sizes of fragments. We will also recommend that support for MTU Discovery be made a requirement. SCHEDULE We expect never to meet again. Progress towards standardization will go as fast as possible, unless serious objections are raised. 1 ATTENDEES Fred Bohle fab@saturn.acc.com Steve Brunigos(?) David Burdelski daveb@ftp.com Duane Butler dmb@network.com Andrew Cherenson arc@sgi.com Noel Chiappa jnc@PTT.LCS.MIT.EDU Steve Deering deering@pescadero.stanford.edu Dave Forster Rich Fox sytek!rfox@sun.com Karen Frisa karen@kinetics.com Steve Hubert hubert@cac.washington.edu Van Jacobson van@helios.ee.lbl.gov Stev Knowles stev@ftp.com Yoni Malachi yoni@cs.stanford.edu Keith McCloghrie sytek!kzm@hplabs.HP.COM Leo J. McLauglin III ljm@twg.com Jeff Mogul mogul@decwrl.dec.com Drew Perkins ddp@andrew.cmu.edu John Moy jmoy@proteon.com Stephanie Price cmcvax!price@hub.ucsb.edu Mike Reilly reilly@nsl.dec.com Tim Seaver tas@mcnc.org Frank Slaughter fgs@shiva.com Richard Smith smiddy@pluto.dss.com Brad Strand bstrand@cray.com Cal Thixton cthixton@next.com John Veizades veizades@apple.com Jonathan Wenseur(?) jhw@shiva.com 2