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Sidewinder G2 6.1.1 Administration Guide - Glossary of Technical ...

Sidewinder G2 6.1.1 Administration Guide - Glossary of Technical ...

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Configuring connection ports<br />

Setting up a new proxy<br />

The Edit a Port window allows you to configure a single port or a port<br />

range, or you can select from pre-defined ports for specific proxies by<br />

selecting one <strong>of</strong> the following radio buttons:<br />

Specify a Port—Select this option to specify a single port. In the Port<br />

field, type a port number or use the up and down arrows to<br />

display the desired port.<br />

Specify a Port Range—Select this option to specify a port range. In<br />

the Begin Port and End Port fields, specify the range <strong>of</strong> ports that<br />

this proxy can use (you can either type the port numbers in the<br />

appropriate fields or use the up and down arrows to display the<br />

desired ports).<br />

TCP maximum segment size<br />

The TCP layer uses a maximum segment size (MSS) parameter to<br />

determine how much data can fit in a single data segment. At<br />

connection time, systems negotiate how big this value can be.<br />

If you choose an MSS that is too small, all systems passing a given<br />

piece <strong>of</strong> data through a network must process more IP and physical<br />

network frames. This can drastically slow down an entire network. On<br />

the other hand, an MSS value that is too large forces the IP layer to<br />

fragment and reassemble the data, overburdening the receiving<br />

system.<br />

Almost all systems on the Internet accept a TCP MSS <strong>of</strong> 536 data bytes.<br />

Most newer TCP/IP systems can effectively use a TCP MSS <strong>of</strong> 1460<br />

bytes, improving the traffic load on the entire network. The<br />

<strong>Sidewinder</strong> <strong>G2</strong> uses this as the default MSS value. With systems that<br />

cannot accept segments <strong>of</strong> 1460 bytes, the <strong>Sidewinder</strong> <strong>G2</strong> negotiates<br />

down to the MSS that can be effectively used.<br />

In a few cases, the default 1460 byte MSS size could cause a problem.<br />

Some older TCP/IP implementations do not negotiate the TCP MSS<br />

value. These older implementations also cannot perform IP<br />

reassembly. The most likely symptom will be that these systems will<br />

no longer be able to communicate through the <strong>Sidewinder</strong> <strong>G2</strong>.<br />

Configuring Proxies 8-33

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