In message <[email protected]>, "Tony Hain" writes: > Tore Anderson wrote: > > * George Michaelson > > > > > One thing I *strongly* agree with: the sentence at 2.2: > > > > > > The effective MTU for IPv6 is 1280 bytes. > > > > > > This is looking compellingly awful, but true to me. > > > > I believe this is a gross exaggeration. I'm running 1500 bytes MTU on all > the > > clients and servers in my network, and have yet to hear about significant > > trouble (there have been a few, but no more than what I get with IPv4 as > > well). > > So what happens over the next 10 years as there is a mix of 1500 & 4k > systems? Or over the next 100 as the sizes continue to vary and routes flap > across an array of link sizes? Yes pmtud sorts out part of that, but does > tcp or the app need to become more dynamic about MSS changes during a > connection? Why? Just so people that want to use the hammer of 'no > fragments' are happy? Wouldn't it be better for everyone to actually solve > the only real problem, and simply require the L4 protocol be in the first > fragment? > > Short sighted myopia about a seriously outdated frame size should not drive > decisions about long term deployment of an emerging protocol. If the L4 is > in the first fragment, there are no other problems that need solving. If > reassembly resources are a challenge for boxes specifically designed to do > that, question why; but one could go further and require that the only > fragment allowed to be smaller than 1280 is the last fragment. That would > mitigate most of the resource-consumption-crafting nonsense. > > Tony
One needs to get the L4 information the firewall/loadbalancer uses in *each* fragment. For UDP this is the source and destination ports. Create a new skipable hop-by-hop option that contains a copy of these values and add it along with a fragment header when fragmenting UDP packets. For TCP ensure that the IP layer informs the TCP layer if it would have to fragment the packet. i.e. don't send fragmented TCP packets. For ICMPv6 ??? For IPv4 if DF=0 fragment the Ipv4 packet to fit in inside 1280 IPv6 packets destination reassembles. For IPv4 if DF=1 return IPv4 PTB For XXX ???? > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > [email protected] > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: [email protected] -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
