Question : Reassembled PDUs / Fragmentented TCP packets

Hi,

I am doing database queries over a relatively slow line and became aware, that only some 1/6th of the available bandwidth is used.

The server is Windows 2000 Server, the database is SQLBase ( please see also this question: http://www.experts-exchange.com/Databases/Q_22073042.html ).

When doing a network trace with ethereal, I noticed that basically all packets sent from the server  are split into fragments, with Ethereal  noting: TCP Segment of a Reassembled PDU. Also, the payload of those packets is really small, usually less than 300 bytes and never more than 600, resulting in a huge number of packets for a small amount of data.

I played with the MTU settings (which didn't show any effect at all), along with the various window sizes and so on. The strange part is:a dump on the server itself shows this behaviour, too. If, on the other side, I just download a file from the server via SMB, everything is fine anf nearly the whole bandwidth is used, though.

I also tried connecting from another server in the same network, but basically it is the same. Lots of PDU segments, just less notible performance impact, because the line is faster.

Any ideas? Is this a problem of SQLBase? One of Windows 2000? Any wrong settings? Thanks for your suggestions.

Answer : Reassembled PDUs / Fragmentented TCP packets

Is your "relatively slow" connection made via VPN or any other encryption methods? VPN and most encryption causes packet fragmentation because of the encapsulation of data packets. It's something to check.
FS-