Fred, [...]
>> Why advertise WAN side MTU to LAN side? Doesn't routers >> advertise LAN MTU via RA? PMTU would work out the optimal >> MTU for end-to-end communication. > > PMTUD within end sites *has* to work in order for there > to be any measure of robustness. Customer end systems > and middleboxes that filter ICMPs are only hurting > themselves and need to change their ways. > > That said, I believe the reason for asking the CE to > advertise 1480 internally to the customer site is to > minimize the incidence of invoking PMTUD. Otherwise, > customer end systems would be constantly sending 1500 > packets initially which would be thrown away by the > CE until PMTUD kicks in. As I mentioned however, the > issue with advertising the 1480 is that it would cause > an MTU reduction even for communications that never > leave the end site. Customers with 9K links might > not like that. 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. it should be rare that path MTU discovery doesn't work on the first hop. cheers, Ole _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
