Marcy: I would add the word "enough" after "large" in Alan's first comment. It makes no difference if your MTU is 1500 bytes or 56K bytes if the longest packet you send is 500 bytes.
Romney On Tue, 12 Feb 2002 17:29:48 -0500 Alan Altmark said: >On Tuesday, 02/12/2002 at 01:42 PST, Marcy Cortes <[EMAIL PROTECTED]> >wrote: >> Now, one more question! In the TCP/IP P&C manual, p.508 lists >> some recommended MTU sizes for various types of interfaces. What's >> a good MTU size for guest lan? (our primary app at this point >> is apache webserving). > >For guests that communicate with *each other* on the guest LAN, a large >MTU is best. When routing traffic to a real LAN, use the MTU of the real >LAN. Otherwise you get packet fragmentation which just steals cycles from >the machine. > >Linux had "dynamic path MTU discovery" so the apache server will >automatically discover the best MTU to use. With this model, feel free to >use a larger MTU on the guest LAN. Fragmentation will occur initially, >but will disappear as Linux reduces the MTU automatically. Just make sure >the initial MTU size specified on the apache server matches the MTU >specified on VM TCP/IP. > >Regards, >Alan > >IBM Senior Software Engineer >z/VM Development, Endicott, NY >Phone 607.752.6027 fax 607.752.1497 t/l 852
