Page 2-94
Specifications
INTER-TEL
®
AXXESS
®
MANUAL VERSION 11.0 – May 2008
IP Network Specifications
7. IP NETWORK SPECIFICATIONS
7.1 Because the IPRC uses Internet Protocol (IP) to connect Inter-Tel systems, your data
network must meet certain specifications to ensure a quality phone network. This section
describes these network requirements.
NOTE: Currently the IPRC does not support faxing over the IP network.
7.2 Inter-Tel recommends that you run the Network Qualifier (for at least 24 hours) to
assess your network before purchasing or installing the hardware required to set up voice over
IP (VoIP). The Network Qualifier currently supports up to eight simulated VoIP connections.
While in the Network Qualifier, set the Audio Frames/IP Packet and Minimum Playback
Buffer Time fields to the appropriate values (see page 2-98). If the assessment reveals that your
network is operating outside the specifications listed below, contact your network administra-
tor. The Network Qualifier application is available on the Inter-Tel Web site (www.inter-
tel.com) and on the phone system software CD.
A. PERFORMANCE
7.3 The quality of the data network is one of the most important factors in achieving a high-
quality Internet Protocol (IP) telephony call. The variables involved include the speed and
capacity of the network configuration, type of connection, routing scheme, and amount of traf-
fic being passed through the network.
7.4 Inter-Tel recommends the following network performance characteristics for voice:
• Packet Loss: (The percentage of unusable packets) No more than 5% random packet
loss
• Successful Packet Rate: (The opposite of packet loss) 95% or more
• Latency: (The time it takes for information to pass from one point to another) Less than
120ms of one-way delay and less than 250ms of total end-to-end delay
NOTE: End-to-end delay is the sum of the one-way network, buffering, and process-
ing delays. For example, at default, the total buffer and processing delays of the IPRC
is 130ms, leaving 120ms (250ms - 130ms) of allowable network delay.
• Jitter: (Changes in delay) 40ms or less (indicated by the results from the Network
Qualifier)
CAUTION
Inter-Tel strongly recommends using the IP devices on a managed private network. If
using a private network, the following recommended guidelines are relatively easy to attain.
However, if connected to the public Internet, IP devices do function, but the quality may suf-
fer due to the dynamic bandwidth availability. The possible problems could be voice quality
degradation, garbled speech, dropped calls, equipment resets, etc. Also, the VoIP suitability
of any Internet connection can change at any time, with no advance notice. Inter-Tel cannot
guarantee any voice quality when connected to the public Internet. Therefore, Inter-
Tel is not responsible for network quality issues that are caused by using the public
Internet.
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