SIP Services

Session Initiation Protocol (SIP) is a signaling protocol for creating, modifying and terminating multi-media sessions with one or more peer-to-peer participants.  VoIP calls, video calls, multi-media distribution and multi-media conferences are examples of services provided by the SIP multi-media sessions.

Once a session is created between two end points, for example, two SIP phones, it can be used to transport a VoIP call or a video call. Multi-media data are transported between the SIP end points by the Real-time Transport Protocol (RTP).

SIP VoIP services are designed to be implemented at the edges of an IP network and in the communicating end points like the SIP phones, which are also the two ends of a multi-media session.

During the session initialization and service negotiation, the SIP end points are expected to provide their peers with their multi-media capabilities: video or only audio, codecs, and other information.  And they negotiate for the optimal media session parameters that work for both ends. In contrast, the call services provided by the voice carriers, both wireless and wired, are deployed in centralized control SS7 in the carriers' internal networks. The phones controlled by SS7 don't negotiate services and are considered "dumb devices". 

The following is a list of SIP VoIP services can be supported by the SIP phones. Most services in the list are built in with the SIP phones, only some need the assistance of a SIP server. These SIP services are defined in SIP RFCs. The same set of services are also offered by SS7 supported wired or wireless voice carriers.  You can test these services with the SIP phones listed in the page SIP Phone Download.

  • Call Hold 
  • 3 Way Conference
  • Consultation Hold
  • Find-Me
  • Music on Hold
  • Incoming Call Screening
  • Unattended Transfer
  • Outgoing Call Screening
  • Attended Transfer
  • Call Park
  • Instant Messaging Transfer
  • Call Pickup
  • Unconditional Call Forwarding
  • Automatic Redial
  • Call Forwarding on Busy
  • Click to Dial
  • Call Forwarding on No Answer