On 01/06/2012 05:36 PM, Brian E Carpenter wrote: >> That's why people think of RFC4821 as a mechanism for PMTUD blackhole >> detection rathern than as a repalcement for traditional PMTUD (i.e., you >> use the transport-layer probes when it looks like tradictional PMTUD is >> not working (possibly as a result of filtered ICMP error messages)). > > "when it looks like" is the statement of an AI problem. I think we > were talking about the case where the happy-eyeballs heuristic fails > inelegantly because SYN/ACK worked fine but PMTUD (or possibly MSS > negotiation) failed.
Sorry, I meant "it looks like PMTUD messages are being dropped" -- and yes, "looks like", because you cannot tell for sure. > In that case, the happy-eyeballs state machine > as described so far doesn't know that it needs to do anything more. > So this pretty much needs to be done spontaneously by the transport > layer, if SYN/ACK succeeds but no further traffic occurs. Sorry, not sure what you're referring to. I just said that PLPMTU has a long convergence time, and hence it's usually seen as a "PMTU blackhole detection/recovery mechanism", rather than as a replacement of traditional PMTUD. Thanks, -- Fernando Gont SI6 Networks e-mail: [email protected] PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492 -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
