PictureTel III ISA manual Fifo Packet Threshold, Concurrent UDP Streams, Low-Priority Ratio

Advanced Options Tab B-3

The following advanced values can be modified to regulate PACE traffic on the network.

FIFO Packet Threshold

Controls the number of non-PACE packets that the network driver allows in the FIFO ahead of PACE packets. A smaller number decreases the time between PACE packets, but it can also decrease performance. The recommended setting is 3.

Concurrent UDP Streams

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

For example, a videoconference with three people at three different sites uses three concurrent UDP streams for the video data. The concurrent UDP streams setting must be a power of two (2, 4, 8, 16, etc.), but the optimal value varies depending on your PC and the application that you are running.

Although a video server can support up to 32 connections, a client may only want to conference with four other people at a time. The recommended setting is 16.

Low-Priority Ratio

When PACE support is enabled, high-priority packets are always transmitted before low-priority packets. If a high-priority application sends out a sufficiently high number of high-priority packets, low-priority packets may not be sent.

To prevent this problem, the driver uses a ratio setting to periodically send out a low-priority packet (if one is waiting to be sent). For example, if a value of 1000 is entered, one low-priority packet would be sent for every 1,000 high-priority packets. The recommended setting is 25.

Natural Packet Interval

To communicate packet priority to interconnect devices (repeaters, switches, and the like), the PACE driver slightly modifies the Ethernet packet. Because of this, connection problems may result when these modified packets are sent out for long periods of time during which no low-priority packets are sent. To get around this problem, the driver can be configured to periodically send out an unaltered, natural packet. The recommended setting is 180 seconds.