Nicolas Williams writes: > On Tue, May 12, 2009 at 01:25:11PM -0400, James Carlson wrote: > > To be more specific -- it's a performance thing. There are apparently > > a few drivers for which the largest allowable configured MTU is _not_ > > also the MTU that will result in the best application performance > > ... for some given definition of what "application" we're talking > > about and specifically what "performance" means in that context. (I > > suspect "application" means either NFS or iSCSI and "performance" > > means only "throughput," but that's just a guess.) > > That transports and applications could dynamically detect optimal > message sizes in similar ways, provided that the protocols have > something like do-not-fragment. I.e., do PMTUD but also have an > iSER/SRP/RDDP/whatever extension by which you can ask the peer to tell > the sender what is an optimal size -- the combination of PMTU and peer's > local optimal MTU will tell you what is the optimal PMTU. > > (There's a variant of TCP PMTUD that does not depend on ICMP replies to > do-not-fragment -- it probes the path MTU and responds to timeouts if > the ICMP does not arrive. Solaris does not implement it.)
That'd be really quite slick, and in my opinion having it happen automatically is *FAR* superior to any kind of administrative gizmo. -- James Carlson, Solaris Networking <[email protected]> Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ networking-discuss mailing list [email protected]
