User Manual

Additional Remote Networking Increasing Performance
5-9
5.4 Increasing Performance
5.4.1 Filtering Unwanted Data
To reduce the use of bandwidth for unwanted packet traffic, each site may configure an incoming and an
outgoing filter list. Packets will be compared to these filter lists as they are received or generated. If they do
not pass the filter, they will be discarded. See Filter Lists on page 5-2 for more details.
5.4.2 Compressing Data and Correcting Errors
The amount of data that can be transmitted at once (throughput) can be increased by using data compression.
Data compression enables a device such as a modem to transfer a larger amount of data at once. When
compression is used, uncompressed data arrives on the modem’s serial port and the modem compresses the
data before sending it over the phone line.
The disadvantage of compression is increased latency, the time required to transfer data from one place to
another. Compression increases latency due to the time required to compress the data before it is sent. Error
correction can also increase latency, as the data must be checked for integrity after it is received.
In situations where the delay is undesirable (for example, during interactive use over a long distance line),
compression and error correction should not be used. These options are enabled by default on the SCS; to
disable them, use the following commands:
Figure 5-16: Disabling Error Correction and Compression
Note: For a complete discussion of compression and error correction, see Chapter 9,
Modems.
5.4.3 Adding Bandwidth
Like compression, adding bandwidth can increase throughput. Sites can be configured to automatically
bring up additional connections when more bandwidth is needed, for example, when the amount of data to
be transmitted exceeds the bandwidth of the port.
How "aggressively" a site will add bandwidth can be controlled with two factors: the period during which
the use of bandwidth is measured, and the percentage at which bandwidth is added.
For example, to increase bandwidth for small or periodic increases in traffic, reduce the measurement time
period. A similar effect could be obtained by reducing the percentage utilization at which bandwidth is
increased. To require a sustained increase in traffic to increase bandwidth, the measurement time period and
the utilization percentage should be increased. See Bandwidth On Demand on page 5-5 for more
information.
Local>> DEFINE PORT 2 MODEM ERRORCORRECTION DISABLED
Local>> DEFINE PORT 2 MODEM COMPRESSION DISABLED