TCP/IP data transfer over Ethernet

[jdu@sasd1.att.com (John D Unruh +1 708 979 6765)]

No specific experience with MacTCP other than as a frequent Telnet, FTP, and
NFS user.  It seems to work well enough, not nearly as slowly as what you
describe.  I think it might be valuable to look into your network and the
way in which you are using the protocols for a speedup.  

With the various Ethernet topologies, the one consistent thing is that unless
your network is overly long, the throughput is pretty much independent of 
the distance between stations.  Now, if you are going across networks using
routers, then things are different.  In any case, could the Ethernet between
your mac and whatever is receiving the video heavily loaded?  If you have
a high load and a lot of collisions, you will not get good throughput.
Similarly, if the boxes 10 feet apart of on different networks connected by
routers (yes, I have seen such things), you may have a bottleneck.  Another
possibility is a improperly terminated thinnet network, or a station jamming
the network.

Once past the physical layer, there is the protocol.  I think the use of TCP
is probably more appropriate than UDP, but it depends on the amount of data
you are sending.  In general, UDP is used to send unreliable datagrams that
don't contain huge amounts of data.  If a frame is say 1K of data, UDP might
be appropriate.  If you use TCP, you must make sure that you don't constantly
connect and disconnect.  It you establish and destroy a connection for each
frame, and the frames are pretty small, you will have a huge amount of 
overhead.

John Unruh

P.S.  It is also possible that there are other problems on the network causing
massive retransmissions.  For example, if one side doesn't acknowledge in
a reasonable amount of time.  You might also have a bottleneck in your code
on one side or the other.