Basic Overview of VOIP and SIP Trunking

Are SIP trunks the wave of the future in telecom? Only time will tell. SIP (Session Initiated Protocol) trunking has been a hot topic in the telecom community for the last couple of years. Back in the days of wire line telephony, when all phone calls went over the PSTN, businesses would purchase “trunks” – a dedicated line or a bundle of circuits – from their service provider. Today, we have adapted the concept of “trunking” to the IP-enabled landscape resulting in lower telephony costs and rapid return on investment plus the opportunity for enhanced communications both within the enterprise and with vendors, customers and partners. SIP trunks can offer significant cost-savings for enterprises and unlike in traditional telephony a SIP trunk allows a company to replace these traditional fixed PSTN lines with PSTN connectivity via a SIP trunking service provider on the Internet. Another major reason why many people regard SIP Trunk telephony as next generation technology is that it lends itself to superb disaster recovery and business continuity provisioning.

 Let me first try to explain VoIP (Voice over Internet Protocol). Numerous PBX vendors have been recommending SIP trunking with their Voice over Internet Protocol. Although VoIP technology has evolved greatly over the past decade, such fundamentals of IP PBX systems as how they operate and what they require to perform reliably has not changed. A common misconception is that VoIP means that phone calls are carried primarily over the Internet. Although that capability exists, the “Internet” as used in “Internet Protocol” has nothing to do with the World Wide Web. It really should be spelled “inter-net” — between networks.   And, a definition for “protocol” is that it is just a technology rule or standard, in this case for enabling the transport of voice data packets over a network. That network can be a local area network (LAN) that is within a building, a wide area network (WAN), and yes, the Internet itself.

If using the Internet, connectivity to the IP PBX is achieved through SIP trunks and the communications are managed by an Internet Service Provider (ITSP), the equivalent of the “phone company”.  SIP represents another industry standard protocol, and the trunks can be a broadband T1 circuit, DSL, Cable Modem, etc., opening up a new world of communications capabilities and savings including remote worker communications, inter-office system integration, least cost routing of phone calls including international calling, unified communications, effective “find me” routing of calls, lower line costs, etc.

Many enterprises are already using VoIP; however, many are only using it for communication on the enterprise LAN. In this scenario VoIP is only being used as a one-to-one replacement for traditional wire line telephony. For all calls made to the outside of the LAN a PSTN gateway on the enterprise edge is used. These businesses realize a solid ROI just by lowering administrative costs and the costs associated with calls made within the company. With SIP trunking, the potential for ROI is far greater because SIP trunking takes the idea of VoIP a step further, beyond this LAN application. The full potential for IP communications can be realized only when the communication is taken outside of the corporate LAN.

The productivity benefits with SIP and SIP trunking are also significant. By extending the SIP capabilities of the corporate network outside the LAN, satellite offices, remote workers and even customers can use VoIP and other forms of real-time communications applications to break down barriers of geography to share ideas and increase productivity.  The basic principles of SIP Trunks are understood as Voice/ data is carried via a dedicated ‘trunk’ across the web, a portion of the bandwidth is reserved for those services, rather than across ordinary internet routes. SIP Trunking is therefore faster and more reliable, being less prone to performance issues as determined by the volume of public web traffic. Using a SIP Trunk can offer your business number portability and disaster recovery which are significant strengths. Another advantage of SIP Trunking is that it allows users’ telephone numbers to exist independently of their phone’s location. In contrast, the number allocated to any given ISDN or PSTN line is determined by the local exchange.

Businesses do not really care what a SIP trunk is, what they are looking for is reliability, quality and low cost telephone service. The transport mechanism is secondary.  A good vendor can explain the rest.


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