Troubleshooting guide

OmniTouch UC R3.0 – Troubleshooting Guide for IP Softphone
Copyright © 2005 Alcatel, All rights reserved
Edition 3 – Page 14
2.3 Checkpoints
2.3.1 Checking the Quality of Service (QoS)
Layer 2 Ethernet (802.1P/Q) is not supported by IP Softphone applications. Only TOS/DiffServ for
Layer 3 IP is available. The TOS (Type Of Service) can be managed on the client machine
(Windows 2000 or Windows XP) through the Windows registry (use the regedit tool for example):
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"DisableUserTOSSetting" REG_DWORD 0 or 1
Field DisableUserTOSSetting sets to 0 means that the TOS is not managed by the computer but by
the application. So, set this value to 0 so that the IP Softphone application will be able to use
their own TOS/DiffServ.
" If value “DisableUserTOSSetting” does not exist in “Parameters” key, you must create it. To do so
through the regedit tool, go to the Edition menu, select New / DWORD value and enter the new
value “DisableUserTOSSetting”.
If TOS/DiffServ is managed by the application (value 0 in above key), you must activate the
TOS/DiffServ on OmniPCX side to allow flows on the data network to assign a priority.
To do so (through mgr system tool for example), go to the IP section, select Go down hierarchy, and
modify IP Quality of service Category as illustrated below:
Consult/Modify: IP Quality of service Category
Node Number (reserved) : 20
Instance (reserved) : 1
IP Quality of service Category Id : 2
802.1p used + False or True
802.1p priority : 7
VLAN ID : 0
TOS/diffServ : 46
UDP Lost : 15
UDP Lost Reinit : 7
UDP Keep Alive : 3
" Recommended value for the TOS/DiffServ field is 46 (refer also to the Alcatel OmniPCX
Enterprise documentation).
Note that other parameters must be checked for the voice quality:
• Delay in packets (refer to the standard ITU G114):
 Between 0 and 150 ms: normal conversation
 Between 150 and 300 ms: acceptable quality
 Between 300 and 700 ms: bad quality
• Loss of packets
 Limit of 20%. Beyond, the audio signal is no more audible.
 More: no communication possible, very bad quality