Hi there: I believe the issue is not about fragmentation.
The minimum Maximum Transmission Unit (MTU) of 1280 stated in RFC 2460 does not stops IPv6 packets to be smaller that 1280 octets - what it does say is that any link that is supposed to convey IPv6 packets must accept packets that are at least as big as 1280 octets - what the RFC says is that if an IPv6 node has a path MTU smaller that 1280 octets, then the IPv6 packets must be fragmented/reassembled at a layer bellow IPv6. Actually, is kind of dumb to have a protocol that defines packets to be as big as 64K and then mostly uses only 1500 bytes, but that another story, and btw, this was already true for IPv4... Ethernet issue I suppose... So, if a given payload is to conveyed over a network whose path MTU is 1280 (but it can be bigger, as far as I know, there is no upper limit) the sender fragments the payload and encapsulates it in IPv6 packets whose size is 1280 octets. This does not mean that the last (or any) packet cannot be 100 octets long, it only says that an IPv6 node, after running Path MTU Discovery (RFC1981), must fragment its payloads as to make the IPv6 packets as big as the discovered MTU. So here are my 2 cents, hope it helps, and I take this occasion to wish you all a very Happy Season, and a wonderful 2006. Greetings! Nuno Garcia PhD Student SIEMENS S.A. INFORMATION and COMMUNICATIONS * RESEARCH and DEVELOPMENT 1 * RESEARCH Rua Irmãos Siemens, 1 Ed. 1, Piso 0 Alfragide 2720-093 Amadora Portugal Phone: +351-21 416 7159 Fax: +351-21 424 2082 e-mail: [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: quinta-feira, 15 de Dezembro de 2005 19:20 To: [EMAIL PROTECTED]; ipv6@ietf.org Subject: RE: Fragmented IPv6 packets The mandate is on the fragmentation is on the transmitting side (the one that applies the fragmentation). The receiving side may reassemble these packets. From at least one implementation (Open BSD) there is no such check. Also the TAHI test doesn't test for this case. All of the above and the common sense says that the receiver should assemble these packets. Hope this helps! Shuki -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, December 09, 2005 1:42 AM To: ipv6@ietf.org Subject: Fragmented IPv6 packets I have a question on IPv6 fragments. Since IPv6 mandates a minimum MTU of 1280, IPv6 fragments (except the last fragment) should be of minimum 1280 bytes right? When an end host receives an IPv6 fragment which is lesser than 1280 bytes ( except the last fragment ) , should it treat it as invalid and drop it or should it still consider the fragment for reassembly. Are there any IPv6 implementations which reassemble them? Thanks, Muthu -------------------------------------------------------------------- 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 -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
