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4600 Series IP Telephones
Issue 4 August 2006 33
Avaya assumes that your organization has performed a network assessment with or without
Avaya’s assistance before attempting to install Voice over IP. The network assessment provides
a high degree of confidence that the existing data network has the capacity to carry voice
packet traffic. The network assessment assures that the existing data network is compatible
with the required technology.
A network assessment should include:
● A network audit to review existing equipment and evaluate its capabilities, including its
ability to meet planned voice and data needs.
● A determination of network objectives, including the dominant traffic type, selection of
technologies, and setting voice quality objectives.
The assessment should leave you confident that the implemented network will have the
capacity for the foreseen data and voice traffic, and can support H.323, SIP, DHCP, TFTP,
HTTP, and jitter buffers in all applications.
It is important to distinguish between compliance with the minimal VoIP standards and QoS
support, the latter being a requirement to run VoIP on your configuration.
4600 Series IP Telephones
The 4600 Series IP Telephones support either of two signaling protocol families - H.323 and
Session Initiation Protocol (SIP).
The H.323 standard, developed by ITU-T, provides for real time audio, video, and data
communications transmission over a packet network. An H.323 telephone protocol stack
comprises several protocols:
● H.225 for registration, admission, status (RAS), and call signaling,
● H.245 for control signaling,
● Real Time Transfer Protocol (RTP), and
● Real Time Control Protocol (RTCP).
SIP was developed by the IETF. Like H.323, SIP provides for real time audio, video, and data
communications transmission over a packet network. SIP uses various messages, or methods,
to provide:
● Registration (REGISTER),
● Call signaling (INVITE, BYE)
● Control signaling (SUBSCRIBE, NOTIFY)
SIP also supports RTP and RCTP using the Session Description Protocol.
A telephone is loaded with either H.323 or SIP software as part of its initial script file
administration and initialization.