Aastra OpenCom X320 User Guide - Page 101
Optimisation, Packet Propagation Delay and Packet Loss, Value, Quality Level
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Voice over IP (VoIP) Fundamentals 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 8.2.4 Optimisation If you detect a large fluctuation in the propagation delay during measurement, this may also cause the voice quality to deteriorate. This may indicate a defective or overloaded line caused by bit-error or collision correction resulting from retransmission by the transmission procedure. An existing star-topology ethernet-network may uses a Hub as the central distributor of ethernet packets. A Hub repeats all ethernet packets received on all connected lines. This can cause substantial collisions and result in a high fluctuation in the propagation delay. If this is the case, use a modern switch component. Selective forwarding of ethernet packets ("Layer 2 switching") avoids collisions. Modern switch components also evaluate the TOS byte of IP packets, thereby providing the optimal prerequisites for VoIP telephony. Note: The OpenCom X320 uses a TOS byte ("Type of Service") value of 0xB8 for IP packets with VoIP data. This requests 99