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.