Fred, Ole, Brian, Le 4 mars 2010 à 22:03, Templin, Fred L a écrit :
>> -----Original Message----- >> From: Ole Troan [mailto:[email protected]] On Behalf Of Ole Troan >> >> ...I can remove the sentence recommending advertising the tunnel MTU on the >> LAN-side interface. or >> change it from a SHOULD to a MAY. as you say this is just to minimize the >> incidence of invoking >> PMTUD. > > Removing the sentence might be best. The MAY would be OK, > but then you might need to also say something like: "(Note > that advertising the tunnel MTU on the LAN-side interface > would cause all hosts attached to the link to use a reduced > MTU even for link-local communications.)" Fred, Ole, Brian, Until PMTUD is made reliable in IPv6 (btw an important objective), all IPv6-enabled hosts should have their MTU set to 1280 to avoid IPv6 blackholes. This could in principle apply only to IPv6 packets that leave customer sites, but as long as hosts have only one MTU parameter, it has to apply to all packets. Since typical hosts have longer default MTUs than 1280, advertising MTU=1280 on links that offer paths to the global Internet appears to be the only available tool at hand. The proposal is then to replace: "A 6rd CE SHOULD advertise the 6rd Tunnel MTU, whether determined automatically or configured directly, on the LAN side by setting the MTU option in Router Advertisements [RFC4861] messages to the 6rd Tunnel MTU." by: "As long as the path MTU discovery has not been made reliable, a 6rd CE SHOULD advertise on the LAN side, in the MTU option of Router Advertisements [RFC4861], an MTU of 1280 octets . This is to prevent that longer packets that could have traversed the local 6rd domain may be discarded, because of their size, further in the Internet because of their size. Note that this may cause all hosts attached to the link to use a reduced MTU even for link-local communications, IPv6 and IPv4." Regards, RD _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
