Newsgroups: comp.parallel.pvm
From: manchek@rudolph.cs.utk.edu (Bob Manchek)
Subject: Re: message integrity
Organization: Computer Science Dept, University of Tennessee, Knoxville
Date: 24 Jan 1996 15:59:55 GMT
Message-ID: <4e5l1rINNqbv@CS.UTK.EDU>

In article <4dj8vj$mup@tempo.univ-lyon1.fr>, exbrayat@lisiflory.insa-lyon.fr (Matthieu Exbrayat) writes:
|> I'm on my first day using pvm.
|> I'd like to know if man can be sure that the message send is
|> the same that is received. In other words, is there any control
|> on the messages, e.g. parity?
|> 
|> Thanks in advance
|> 
|> --
|> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|> ~ Matthieu EXBRAYAT							~
|> ~ LISI - INSA Lyon							~
|> ~ Bat 401								~
|> ~ 20, av. A. Einstein							~
|> ~ 69621 Villeurbanne Cedex						~
|> ~ E-mail : exbrayat@lisiflory.insa-lyon.fr				~
|> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hi,

PVM depends on the integrity of the transport layers to keep the messages
correct.  This is not always a good idea, however.  TCP does a fairly simple
checksum (1's-complement sum) and UDP (these are both used by PVM) checksums
are often turned off for compatability with older systems where they didn't
work.

I built a checksum system into PVM, but it's not turned on by default.
To use it, you'll have to edit pvm3/src/Makefile.aimk and add -DMCHECKSUM
to the OPTIONS line.  Then rebuild PVM and rebuild or relink your app.
It will set the checksum for each message before it is sent and check as
it is received.

Hope this helps,
-b

-- 
/ Robert Manchek                University of Tennessee     /
/                               Computer Science Department /
/ (423)974-8295 / fax -8296     Ayres Hall #104             /
/ manchek@CS.UTK.EDU.           Knoxville TN  37996-1301    /
/     http://www.netlib.org/utk/people/BobManchek.html      /


