Yes, sending voice calls over the IP network works very well but SIP trunks and protocol over many more advantages. Most of the time the connectivity to access the VoIP network is still PSTN/TDM via T1, PRI or ISDN trunks. With SIP you reduce or eliminate the gateway to PSTN/ TDM connectivity and connect directly to the ITSP/SIP provider. So now you have more end-to-end or peer-to-peer communication. No longer need to purchase and manage traditional TDM-based voice circuits with limited scalability. SIP trunks are more flexible and efficient so you get the bandwidth you need. The advantage is reducing access equipment cost and increasing bandwidth.

Once you have SIP trunking you can then take advantage of the many realtime communications features the protocol has to offer. SIP provides the ability to integrate traditional voice services with Web-based features like videoconferencing, single number reach, instant messaging, presence, and mobility. Users will be able to inform callers of their availability and preferred method of communication, such as email, telephone or Instant Message. Presence will also enable users to instantly set up chat sessions and audioconferences. Unlike VoIP, SIP allows you to extend these features beyond your LAN to offer these features to your teleworkers, suppliers, customers, or partners.

The disadvantange of SIP right now is different vendors have created their own version of SIP. But the SIPConnect Forum is correcting this issue and coming up with a standardized version to ensure complete interoperobility.

Here the main advantages we are looking at:

• Investing in SIP Trunks nullifies the need to purchase equipment, such as managed-media gateway devices, to interface between IP voice and the PSTN

  SIP Trunking eliminates the need for PRI (primary rate interface)/ BRI (basic rate interface) connections, which in turn will lower telephony costs

  With SIP Trunks, companies have points of presence in multiple U.S. cities so they can establish local numbers rather than rely on a 1-800 number

  Since only one connection for data and voice is needed with SIP Trunks. Companies reduce the recurring costs of separate PSTN and data circuits (some dedicated to voice and some to data

  SIP Trunking eliminates the over-subscription of voice channels based on business requirements

  SIP Trunks support multiple methods of communicating including instant messaging and video which allows for greater levels of user presence

  SIP Trunking utilizes DID’s (Direct Inward Dials) that allows each employee to have their own phone line. This will increase the flexibility and implementation of call control and dial plans

  SIP Trunking improves the call quality of voice based IP communications because each SIP Trunk is a dedicated “channel

  SIP Trunking allows for the selection of a single SIP Trunk which greatly increases the flexibility and ease of adding, subtracting, or changing a line

  SIP Trunks enable faster and more efficient disaster recovery with an IP network’s distributed architecture, inherently more error tolerant than fixed line, circuit-switched counterparts