3Com 3C319 Class of Service Advanced Options Settings, Fifo Packet Threshold, Low-Priority Ratio

Using Class of Service Advanced Options 7-7

Class of Service Advanced Options Settings

This section provides a detailed description of each Advanced Values field shown on the Class of Service Advanced Options screen (Figure 7-4).

The Advanced Options section of the Class of Service Advanced Options Screen shown in lower part of Figure 7-4 is not currently available for token ring installations.

FIFO Packet Threshold

This setting controls the number of non–Class of Service packets the network driver will allow in the FIFO ahead of any Class of Service packets. A smaller number decreases the time between Class of Service packets but can adversely affect performance. A value of 12

is recommended.

Concurrent UDP Streams

This option controls the number of simultaneous multimedia UDP packet streams the network driver can handle at any time. For many applications, the number of UDP streams is the same as the number of connections.

For example, for videoconferencing with three people, applications use three UDP streams for the video data. The value must be a power of two (2, 4, 8) but the optimal value may vary depending on the PC and application.

A video server may support 32 connections, but a client may only want to conference with four other people at a time.

A value of 16 is recommended for most applications.

Low-Priority Ratio

When Class of Service support is enabled, high-priority packets are always transmitted before low-priority packets. If a certain high-priority application sends out enough packets, no low-priority packets may be sent.