David, et al,
CRC is almost certainly not the right choice. It is computationally
expensive or requires large tables and is much stronger than needed
for this application. It is worth noting that TCP uses a slight
variation on simple arithmetic checksum and works surprisingly well.
Current developments seem to be gravitating toward the RSADSI-donated
MD4 and MD5 (MD=message digest - designed just for this sort of
application!)
Note that the checksum is being used on top of quite a bit of other
mechanism and isn't trying to do the work of a strong, link-level
checksum. It is trying to make sure that errors-between-the-cracks
are detected.
Dave