Unistim

Unistim is Nortel 's proprietary signaling information transfer protocol ^{[1] [2]} . It is also supported in some IP PBXs (for example, Asterisk ) and softphones from other manufacturers.

The UNIStim is an application-level protocol and is based on the RUDP protocol also developed by Nortel. The difference between RUDP and UDP is the presence of the packet number and the mechanism for retransmission in case of packet loss using rudp packets including an ACK with the number of the received UNIStim packet and a NAK with the number of the lost / missing UNIStim packet. The protocol provides control of the thin client server for VoIP . The server (CS1000) manages, receives information about the status of clients, communicates with other participants supporting the protocol. All teams are divided into several sections for functional purposes. Each message includes 3 main fields such as: manager, recipient team, the length of the entire team, the command code for the manager. The rest of the message depends on the type of command.

The client, receiving a message from the server, executes the request. Depending on the team, the client must report the status of the command that was executed. Also, the client can report their status on request or a set time period. The server completely controls the state of the client and the state of the call. The task of the server when making a call is to configure 2 clients to open RTP traffic. The client performs RTP traffic independently using various audio codecs.

Currently, the latest version of the protocol, which Nortel products support, is UNIStim 4.0. Details of the protocol implementation are available in the document titled “Telephony and Data Network Services at a Telephone”, patent No. 7068641 dated May 7, 1999 ^[3] .

The list of clients supporting the UNIStim protocol: 2001, 2002, 2004, 1110E, 1120E, 1140E, 1150E. A full list of clients is available on the website nortel.com