On Fri, Nov 25, 2005 at 12:11:18PM +0100, Mohacsi Janos wrote: > > > > > On Fri, 25 Nov 2005, Vishwas Manral wrote: > > >Hi Mohacsi, > > > >LWAPP encapsulation, IPv6-in-IPv6 etc. > > I have to study LWAPP encapsulation - currently I have no opinion. In the > IPv6-in-IPv6 encapsulation It is completely possible that tunnel endpoint > has to fragment the packet. Multiple level encapsulation might cause > multiple level of fragmentation. This is the price of if encapsulation....
Right, so I think a typical implementation would as you say, let each fragment have the Path MTU size (at least 1280), while the last might be smaller. But assume you have say a 1500 byte packet. Instead of fragmenting so that the first fragment has say 1280 bytes, why not split packet in two equal sized fragments. That way you avoid further fragmentation which might occur if there is further encapsulation taking place later on the path. BTW, I know that fragmentation order might vary, e.g. Linux at times send (or used to send) fragments in reverse order. Stig > > Regards, > > > Janos Mohacsi > Network Engineer, Research Associate > NIIF/HUNGARNET, HUNGARY > Key 00F9AF98: 8645 1312 D249 471B DBAE 21A2 9F52 0D1F 00F9 AF98 > > > > >Thanks. > >Vishwas > > > >-----Original Message----- > >From: Mohacsi Janos [mailto:[EMAIL PROTECTED] > >Sent: Friday, November 25, 2005 4:11 PM > >To: Vishwas Manral > >Cc: Pekka Savola; ipv6@ietf.org > >Subject: RE: IPv6 and Tiny Fragments > > > >On Fri, 25 Nov 2005, Vishwas Manral wrote: > > > >>Hi Pekka, > >> > >>That sounds good. We seem to be coming from different direction but to > >>the same thing. > >> > >>I however would prefer to be closer to 800, to allow more levels of > >>encapsulation, especially the first header. > >> > >>I do not agree with Mohacsi because the 1280 limit will not allow > >>further encapsulations, without fragmentation. > > > >What further encapsulation are you referering to? If I would be a > >implementer and I would have to pass packets bigger than MTU. > >I would take as much content as I can into the first fragmented packet > >and > >so on until there is content left. I would use fragment at least minimum > > > >MTU (size >1280). > > > > > >> > >>Pekka, besides the RFC does not state how we treat M flag as 0 and > >>fragment Offset as 0? > >> > > > > > >Janos Mohacsi > >Network Engineer, Research Associate > >NIIF/HUNGARNET, HUNGARY > >Key 00F9AF98: 8645 1312 D249 471B DBAE 21A2 9F52 0D1F 00F9 AF98 > > > > > >>Thanks, > >>Vishwas > >>-----Original Message----- > >>From: Pekka Savola [mailto:[EMAIL PROTECTED] > >>Sent: Friday, November 25, 2005 3:12 PM > >>To: Vishwas Manral > >>Cc: Mohacsi Janos; ipv6@ietf.org > >>Subject: RE: IPv6 and Tiny Fragments > >> > >>Hi, > >> > >>On Fri, 25 Nov 2005, Vishwas Manral wrote: > >>>I think that is the minimum Link MTU and not the smallest size > >>non-last > >>>fragment. > >>> > >>>Can you point me to the RFC/ draft which says what you stated? > >> > >>This is a good point. Let me copy a part of Elwyn Davies's message on > >>the list on September: > >> > >> > >>Date: Wed, 21 Sep 2005 23:14:26 +0100 > >>From: Elwyn Davies <[EMAIL PROTECTED]> > >>To: Bob Hinden <[EMAIL PROTECTED]>, Brian Haberman > >><[EMAIL PROTECTED]> > >>Cc: ipv6@ietf.org > >>Subject: Taking RFC2460 (base IPv6) spec to full standard - issues > >>outstanding > >>.... > >>[outstanding issues in core IPv6 spec before moving to full standard] > >>? Fragment reassembly algorithm - should explicitly forbid > >>overlapped > >> fragments and possibly require that non-final fragments are > >>(say) at > >> least 1024 bytes. > >> > >>The minimum IPv6 fragment size is not specified AFAICT. > >> > >>-- > >>Pekka Savola "You each name yourselves king, yet the > >>Netcore Oy kingdom bleeds." > >>Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings > >> > >> > >> > > > > > > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
