3Com 3C10200 NBX Installation Guide - Page 230

230 APPENDIX C: GUIDELINES FOR CONNECTING REMOTE AUDIO DEVICES Communication Latency Requirements The interconnect latency requirements can be broken into two main categories: large packet latency and small packet latency. Depending on the configuration of the interconnection mechanism, these latencies can be quite different, often due to the interconnection device applying compression to the packets. The compression function can increase exponentially with packet size, resulting in very long delays for large packets. Large Packet Latency The round-trip latency on large packets, 300 bytes to full MTU, must be less than 450 ms. The system will support an occasional packet delay of 450 to 900 ms, but each such delay will cause retries and thus affect bandwidth and performance. If delays in excess of 450 ms occur at a "high rate" (more than one such delay every three seconds) then system degradation can occur, resulting in problems initializing (downloading devices) as well as sluggish performance of system features. Small Packet Latency The round-trip latency on small packets, from 64 bytes up to the large packet size, should be less than 150 ms, to maintain a high performance level (this is especially significant in the quality of user conversations). Longer latency will not cause system failure but can result in "talk-over" situations within a conversation. Additionally, the longer latency can cause the system to appear sluggish during user interaction (dialing, answering, etc.).