On Monday, 11/25/2002 at 09:24 ZE8, John Summerfield <[EMAIL PROTECTED]> wrote: > Isn't the relationship supposed to me > MTU <= MRU > where MTU and MRU are values at the opposite ends of the link? > > I can send as much as I like so long as it's no more than you expect to > receive.
In theory, yes, but in practice, no. The MTU may be used to set the I/O buffer sizes, depending on the device's capabilities. If it is a "packing" device, then the output buffer could be a multiple of the MTU, while the input buffer has only enough space for a single MTU-sized packet. CTC is a case where the MTU size and the I/O buffer sizes are completely independent. The MTU is most often dictated by data link standards. I.e. Ethernet with SNAP headers: 1492. Without: 1500. Jumbo frames: 9K. Everyone in the same LAN segment should have the same MTU. This usually means that whoever configures the routers defines the MTU everyone else on the LAN segment will use. Alan Altmark Sr. Software Engineer IBM z/VM Development
