> On 09 Dec 2016, at 23:13, Joe Touch <[email protected]> wrote: > > > > On 12/9/2016 1:38 PM, Michael Tuexen wrote: >>> On 9 Dec 2016, at 22:30, Joe Touch <[email protected]> wrote: >>> >>> >>> >>> On 12/9/2016 1:26 PM, Michael Tuexen wrote: >>>> Not sure what the reassembly limit is... SCTP handled arbitrary sized >>>> user messages a the receiver side by using partial delivery. >>>> >>>> The SCTP_MAXSEG allows a user to limit the size of DATA chunks without >>>> reducing the pmtu. >>> Yes, but that size can actually be larger than the PMTU, not just smaller. >> Hmm. https://tools.ietf.org/html/rfc6458#section-8.1.16 states: >> >> Note that the >> underlying SCTP implementation may fragment into smaller sized chunks >> when the PMTU of the underlying association is smaller than the value >> set by the user. >> >> So this means the user can not rely on this option to turn off SCTP >> fragmentation and let SCTP pass IP-packets down the stack to let >> the IP do the fragmentation. >> >> That is why I said, the user can use this option to ask the SCTP >> layer to use a smaller value than the one deduced from the PMTU. >> That is something you can do safely. > > It seems like this setting is independent of PMTU. It could be larger > than PMTU, in which case SCTP *or* IP could do fragmentation (and I > don't see whether there's a way to know or force that decision).
Why do you say that? IIUC, you can get "spinfo_mtu" ( https://tools.ietf.org/html/rfc6458#section-8.2.2 ), and then set the maximum fragmentation size ( https://tools.ietf.org/html/rfc6458#section-8.1.16 ) to be equal to or smaller than that value, in which case you can safely assume no fragmentation inside the same host. Cheers, Michael _______________________________________________ Taps mailing list [email protected] https://www.ietf.org/mailman/listinfo/taps
