Aastra OpenCom 510 User Guide - Page 121

Voice over IP (VoIP) Fundamentals ■ G.729A (Level 2): Reduction to approximately 8 kilobit/s. ■ G.723.1 6.3 (Level 3): Reduction to 6.3 kilobit/s. ■ G.723.1 5.3 (Level 3): Reduction to 5.3 kilobit/s. Unfavourable packet length selection may reduce voice quality. The duration of the recording and not the data packet's byte count is relevant in making this selection: ■ Duration 60 ms: two quality-levels depreciation The achievable voice quality also depends on the packet propagation delay and the packet loss between the terminals involved. These parameters can be determined using the "ping" program. Note: Measurements made with "ping" are round-trip propagation delays. Divide the maximum value displayed by two. Packet Propagation Delay and Packet Loss Value Quality Level Propagation delay Optimal < 50 ms Propagation delay 0.5 level 50-100 ms depreciation Propagation delay 1 level 100-150 ms depreciation Propagation delay 2 level deprecia- 150-200 ms tion Propagation delay 3 level deprecia- 200-300 ms tion Propagation delay 4 level deprecia- > 300 ms tion Value Loss < 1 % Loss 1-2 % Loss 2-3 % Loss 3-4 % Loss 4-6 % Loss > 6 % Quality Level Optimal 0.5 level depreciation 1 level depreciation 2 level depreciation 3 level depreciation 4 level depreciation 119