Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!ASYLUM.SF.CA.US!romkey From: romkey@ASYLUM.SF.CA.US (John Romkey) Newsgroups: comp.protocols.tcp-ip Subject: re: V3.2 vs V4 UDP and NFS Message-ID: <9103160909.AA01947@asylum.sf.ca.us> Date: 16 Mar 91 17:09:13 GMT References: <16241@uudell.dell.com> Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: romkey@asylum.sf.ca.us Organization: The Internet Lines: 44 Date: 12 Mar 91 00:57:55 GMT From: decwrl!ames.arc.nasa.gov!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!chinacat!uudell!Kepler.dell.com!mjhammel (Michael J. Hammel) Organization: Dell Computer Corp. I seem to be having a problem with V4 systems and UDP. It appears that an NFS-based test between two V3.2 systems that I run shows up under Netwatch as follows: Are you actually having an NFS problem, or is the Netwatch output just not being clear? IP: src addr -> dest addr UDP -> value is the length of the IP packet. value2 is the UDP source port. value 3 is the UDP destination port. value4 is the length of the UDP packet (as I recall). With V4 to V4 systems its more like: IP: src addr -> dest addr 1500 UDP Fragment And its *always like that. Question: what do these numbers mean, what does Netwatch mean by Fragment (and how does he know its a fragment?), and why does either Netwatch see things differently between the two scenarios or why is there a difference? Can it be related to the rsize/wsize default values? Where are these values specified? I'm not specifying these values in the mount command. Fragment means the packet is fragmented at the IP layer. There's information in the IP header that says "this packet has been fragmented" as well as where it fits in the reassembled packet. Netwatch won't tell you more because it's not sure what the UDP port numbers are since the packet is fragmented. It could've picked them up out of the first packet, but I didn't check on that when I wrote it. I don't know enough details about NFS to relate this to particular versions, but it does like to send large (8Kbyte) packets and fragment them into pieces you can actually transmit over the ethernet (roughly 1500 bytes or less). That's what you're seeing in the second situation. Someone else will have to answer the NFS-specific questions. - john romkey Epilogue Technology USENET/UUCP/Internet: romkey@asylum.sf.ca.us voice/fax: 415 594-1141