Implementation of sip over VoIP

Abstract

Back in the days of wired 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 (ROI) plus the opportunity for enhanced communications both within the enterprise and with vendors, customers and partners. A SIP trunk is a service offered by an ITSP to use SIP to set up communications between an enterprise PBX and the ITSP. A trunk includes multiple voice sessions – as many as the enterprise needs. While some see SIP as just voice, SIP trunking can also serve as the starting point for the entire breadth of real time communications possible with the protocol, including Instant Messaging, presence applications, white boarding and application sharing. The potential for a rapid return on investment is a key driver of SIP trunk deployments. However, maximum return on investment can be achieved when you extend VoIP outside of the corporate LAN. In terms of infrastructure purchases, SIP trunks provide an immediate cost-savings. They eliminate the need to purchase costly BRIs, PRIs or PSTN gateways. 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. There are three components necessary to successfully deploy SIP trunks: a PBX with a SIP-enabled trunk side, an enterprise edge device understanding SIP and an Internet telephony or SIP trunking service provider. Equipment based on the SIP protocol – SIP phones, IP-PBXs etc. – have been around for some time. Now that SIP trunks have gained momentum, it has become 3 | P a g e important to ensure that equipment works together. It is for this reason that standards such as SIP connect™ have become so critical. SIP connect was developed by the SIP Forum as a set of best practices for interfacing an enterprise PBX implementation with an ITSP that attempts to eliminate some of the unknowns and incompatibilities of mixing equipment from different vendors in a single environment. Like any application that opens the network to the Internet, SIP trunking deployments have security considerations, but there are ways to maximize enterprise security. One of the most effective techniques is to address SIP security the same way data security is addressed - at the enterprise edge. SIP server and SIP proxy technologies offer maximum control over the flow of SIP traffic, enabling the administrator to ensure correct routing, apply verification and authentication policies and mitigate Denial-of-Service attacks. Voice quality is not an issue with SIP trunking if proper Quality of Service (QoS) measures are applied, such as over provisioning of links, and prioritization of voice traffic. Reliability is also a moot point. In fact, SIP trunks can be more reliable than the traditional PSTN as a number of failover solutions can be implemented.