Sip Trunking Definition: This is a native SIP connection between a SIP-compatible router, gateway, or PBX on the
customer premises and a SIP-compatible network node. This connection conforms to applicable IETF
specifications and may also support provider-specific capabilities. As a provider specifies, SIP trunking may be
offered as a managed service and also as a transport-centric service, and provide on-net connectivity to other
SIP sites (served by the same provider), and off-net connectivity to/from the providers PSTN services. The
provider may offer long-distance connectivity, local connectivity, or both long-distance and local connectivity.
Current providers include AT&T, Global Crossing, and Verizon Business.
SAMPLE OF QWEST'S SIP TRUNKING SERVICE
Your end user's current
High TDM and IP Trunking Costs for SMB/SMEs with existing PBX/Key systems
Separate trunks for voice and data
PRIs only available in 23 DS0 increments
Multiple carriers for different end user locations
Significantly improved with Qwest Instant VoIP.
Solved with SIP Trunking.
Single trunk for voice and data
Purchase only the DS0 equivalents needed
Single nationwide carrier and free on-net calling between end user locations
A SIP (Session Initiation Protocol) connection is a service offered by many ITSP (Internet Telephony Service Providers) that connects a company's PBX to the existing telephone system infrastructure(PSTN) via Internet using the SIP VoIP standard.
Using a SIP connection may simplify administration for the organisation as the SIP connection typically will use the same Internet connection that is used for normal data. This eliminates installation and maintenance of a BRI/PRI connection at each location. However, this almost always comes at the expense of the reliability of a standard TDM PSTN connection.
Thanks to the SIP protocol, transmitting Caller ID and other call-related information is easy and even other information like pictures of the caller can be transmitted. Because SIP connections are digital, the voice is also transmitted digitally and can have excellent audio quality (see Codec) and issues from analog lines like connect and disconnect detection are simple. Also, there is no need to limit the telephone number to 10 digits. This makes it possible to assign Direct Inward Dialing numbers for every extension, so that the auto attendant in the PBX plays a less important role.
The challenge with SIP connections over the public Internet is call quality. If the traffic runs on the same connection with other traffic like Email or Web, voice and even signalling packets may be dropped and the voice stream can get interrupted. Businesses must take special preparations when they want to use SIP connections as their primary PSTN termination. Also, the general stability of the Internet connectivity becomes a critical issue. Because of this, many companies split voice and data up into two separate internet connections to solve this problem, so that the resource conflict on the Internet access side is avoided. Other devices perform traffic shaping in order to avoid this resource conflict, but they still depend on the merit of the service provider not to drop packets from the Internet to the PBX.
