Workshop

Application and Protocol Efficiency
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Let’s consider the example of a driver who stops every few minutes to go to the bathroom. This isn’t
exactly an efficient way to drive, but some folks do it. Similarly, some applications don’t take advantage
of certain protocol efficiencies. What protocol efficiencies might these be?
Let’s take a look at a concrete example. Novell’s “packet burst mode” for IPX/SPX is a way for an
application at one end to avoid a “ping pong” effect with the end station. On totally unreliable networks,
it’s sometimes necessary to get an acknowledgment for each packet transmitted. On a reasonably reliable
network, this creates unnecessary traffic. Take a look at Figure 23.1. The workstation on the right gets all
the packets it needs in six transmissions; the workstation on the left needs many more to get the same
data, because the application on the workstation is insisting on an acknowledgment for each packet. In
large quantities, this is extremely inefficient; Novell’s burst mode is a way of avoiding this. However,
older Novell networks using older clients don’t take advantage of this feature.
Figure 23.1 Unnecessary network traffic.
A way of seriously upgrading the speed of an older Novell network—without a new investment in
hardware—is to get the newest Client32 for your DOS or Windows workstations. Make sure that
PBURST.NLM is loaded on your 3.x server (no action is necessary on a 4.x server). You’ll be amazed at
how much faster your network seems to run.
TCP/IP also has a “burst mode” called sliding windows. Why? Because, when conditions are good, the
TCP “window” (the amount of data that may be sent without an acknowledgment) is large, but when
conditions get bad, that amount “slides” down to compensate. When conditions are good, it slides back
up.
When testing two similar applications’ network efficiency, you can simply do the same operation twice,
measure how much data was transmitted, and come up with the throughput per second for each. I did this
once with two thin-client applications and found that one client was almost four times as efficient as the