---------- From: Ray "The Dragon" Lauff[SMTP:ray@thunder.ocis.temple.edu] Sent: 08 May 1996 12:10 To: Alpha Mailing List; gurus@thunder.ocis.temple.edu; John Center Cc: pulakr@cableol.net Subject: SUMMARY: UPD checksumming for Digital Unix Nameserver First off, thanks for all the replies. It would appear that Digital Unix indeed does do UDP checksums by default. The checksum is across the header and contents of each UDP packet sent across the network and is required by several RFCs. You can use the netconfig(8) tool if you have it, which will display the state of several kernel networking settings. I obtained netconfig from: ftp://ftp.std.com/customers3/src/network/netconfig.tar.gz It compiled easily on DU 3.2. If you don't want to use netconfig, you can use dbx to examine the appropriate variable as follows: -- root> dbx /vmunix dbx version 3.11.8 Type 'help' for help. (dbx) p udpcksum 1 ---- If for some reason you want to turn it off (why...I don't know...) you can use: echo 'assign udpcksum=0' | dbx -k /vmunix /dev/mem As Chris Jankowski said in his email: "Not checking checksums on received packets was a hack to squeeze last drop of performance from an overloaded CPU. The rationale given was that the networks no longer corrupt packets or that the higher layer of protocols will do it. (:-))." The following people were helpful in their responses: Kevin Oberman <oberman@nersc.gov> Stuart Davidson <dav@mas.eurocontrol.be> Chris Jankowski <chris@lagoon.meo.dec.com> Dan Riley <dsr@lns598.lns.cornell.edu> Phil LAwrence <philip@uvo.dec.com> Matt Thomas <thomas@lkg.dec.com> Thanks again folks! Ray -- Ray Lauff : ray@thunder.ocis.temple.edu : (215) 204-5678 : Temple University