Remi, > -----Original Message----- > From: Rémi Després [mailto:[email protected]] > Sent: Friday, March 05, 2010 6:34 AM > To: Templin, Fred L; Ole Troan; Brian E Carpenter > Cc: [email protected] > Subject: Re: [Softwires] SOFTWIRE working group last call on 6rd > > 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."
The 1280 would be disappointing; I'm sure we can do better. Thanks - Fred [email protected] > Regards, > RD _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
