Date: Wed, 8 Aug 2001 18:14:54 +0200 From: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl> To: Mike Tancsa <mike@sentex.net> Cc: freebsd-net@freebsd.org Subject: Re: gif MTU of 1280 ? Message-ID: <20010808181454.Q2937@daemon.ninth-circle.org> In-Reply-To: <5.1.0.14.0.20010808101139.0277e010@marble.sentex.ca> References: <5.1.0.14.0.20010808101139.0277e010@marble.sentex.ca>
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-On [20010808 16:30], Mike Tancsa (mike@sentex.net) wrote: > >Just wondering, is there a reason why the MTU of the gif interface defaults >to 1280 ? Why not 1500 ? Per RFC2460: "IPv6 requires that every link in the internet have an MTU of 1280 octets or greater. On any link that cannot convey a 1280-octet packet in one piece, link-specific fragmentation and reassembly must be provided at a layer below IPv6. Links that have a configurable MTU (for example, PPP links [RFC1661]) must be configured to have an MTU of at least 1280 octets; it is recommended that they be configured with an MTU of 1500 octets or greater, to accommodate possible encapsulations (i.e., tunneling) without incurring IPv6-layer fragmentation." Actually I am wondering about it now myself. X.25 is one of the few link layer protocols left which has a MTU < 1500 (aside from 802.3's 1492). Maybe some IPv6 guru is able to shed some light? -- Jeroen Ruigrok van der Werven/Asmodai asmodai@[wxs.nl|freebsd.org|xmach.org] Documentation nutter/C-rated Coder, finger asmodai@ninth-circle.dnsalias.net http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/ Light-in-Darkness, lift me up from here... To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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