From Zenitel Wiki

SIP - Session Initiation Protocol is the call control protocol used for non-proprietary internet telephony. gives a brief overview of the protocol. is the standards document. SIP is a human readable text protocol, which makes it a bit easer to debug.


AlphaCom supports a subset of the SIP (Session Initiation Protocol). The AlphaCom SIP interface is implemented as a daemon service, SIPd. SIPd runs on the AMC-IP board alongside the main AlphaCom daemon, AMCd. The SIPd process is always started on AMC-IP, but the actual use require purchase and installing proper SW license. SIPd is act as a gateway between the AlphaNet protocol and SIP. The SIPd enables calls between AlphaCom stations and SIP phones.

AlphaCom - SIP integration

The AlphaCom has successfully been integrated with the following products (the list is not complete):

SIP Gateways

iPBX (SIP Trunk)

SIP Phones

SIP WiFi Phones

SIP Analog Telephone Adapters


IP-DECT systems

SIP Stations with iPBX

The STENTOFON SIP Stations have successfully been integrated with the following products (the list is not complete):

Related standards

SIP is a 270 page document which mainly deals with locating the destination "user" when making a call, and provides a framework for negotiating the media setup. Describing the media (audio/video) formats and protocols is left to another protocol: SDP (Session Description Protocol). SDP messages are attached to some of the SIP messages. See for a introduction. is the standards document. By current practice, SIP and SDP is almost always used together.

RTP (Real-time Transport Protocol) is the most usual method for encapsulating audio into IP packets. Further reading here, And the standards document is In AlphaCom, all voice over IP uses RTP, both in internal connections with proprietary call protocols, as well as for SIP calls. RTP mainly deals with handling the sequencing and timing of packets, not so much about the actual audio or video contents. However, a number of very common audio codes formats are listed and enumerated in The number behind the "RTP/AVP" often found in SDP messages refer to table 4 in this document. These are called "static payload types". When they are used, it is possible to playback the stream of RTP packets without having any other information. On the other hand, when using "dynamic payload types", the meaning of the RTP packets has to be agreed upon using an other protocol, like SIP/SDP.