I am backuping my nearstore to tapes using EMC Networker. It uses its command nsrndmp_save to make the nearstore dump to an attached SAN tape drive. I currently have a problem with an internal process of EMC (nsrndmpix) which fails to update its index. The data is clean (waflironed) but EMC doesn't like it. EMC tells me that may be the metadata gets corrupted when sent to their server. So now, EMC asks me to run a network snoop between the nearstore and the Networker EMC in order to check for file history troubles, which puzzles me: i though there were no TCP communication during the backup to SAN tape drives.
All control information from NetWorker storage node and NDMP device goes via LAN. This of course includes file index from NDMP device back to NetWorker storage node. This is in addition to data written to tape, which is in dump format as described in KB you mentioned.