I ran into this in a Mac list.  Now that the HP3000 is hot-and-heavy into
serving web pages, I thought you might benefit from this under-the-hood
info:
 
An interesting article by Robert Moskowitz in the March 15 issue of  Network
Computing magazine discusses how HTTP affects the Internet.  Specifically,
he analyzes the router flow-switching statistics from a Cisco router located
between St. Louis and Kansas City.
 
The primary point he makes is that the design of many HTML documents is such
that they do not benefit from the Van Jacobsen Slow Start
performance-enhancement procedures.  Van Jacobsen Slow Start is beneficial
to the transmission of large files (not to the transmission of many small
files that are typical of most HTTP sessions -- text with several small
graphics).
 
The article discusses TCBs (Transmission Control Blocks, which can range in
size from 8 Kb to 32Kb), which are allocated during each TCP session.  A key
point about a TCB is that it cannot be reused for a new session until it has
waited two minutes. (Yes, two MINUTES).  This ensures proper handling of any
straggler packets that arrive after the session is closed.  This state is
called TIME-WAIT.
 
For each component of an HTML doc (text and each graphic), a TCB is
allocated.  So for an HTML doc with nine icons, 10 TCBs will be used.
These 10 TCBs are out of commission for a minimum of 2 minutes because of
the TIME-WAIT.
 
Moskowitz indicates that to ensure enough TCBs, make the Max User parameter
in your web-server software as high as possible.  This minimizes the
frequency of "Host Contacted, Waiting for Reply" messages received by
clients.
 
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Happy web serving,
 
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|               |
|            r  |  Alfredo                     [log in to unmask]
|          e    |                           http://www.adager.com
|        g      |  F. Alfredo Rego               Tel 208 726-9100
|      a        |  Manager, Theoretical Group    Fax 208 726-2822
|    d          |  Adager Corporation
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