A complete guide to SIP trunks, this whitepaper provides a comprehensive overview on the basics of SIP trunking, including a discussion of infrastructure needs and deployment issues and solutions. In-depth sections dedicated to interoperability, security as well as quality and reliability issues are also included.
SIP Trunking Benefits and Best Practices White Paper Janne Magnusson Vice President, Product Management ®Ingate Systems
Abstract 1 1 What is SIP trunking 1 2 The benefits of SIP trunking 1 2.1 Calculating the investment ROI 2 2.2 Bandwidth utilization 2 2.3 Flexibility to add new lines 3 2.4 Least Cost Routing (LCR) 4 2.5 Making IP-to-IP calls when possible 5 2.6 SIP trunking - the stepping stone to higher productivity 5 3 SIP trunking infrastructure 6 3.1 The PBX component 6 3.2 The enterprise edge component 8 3.3 The service provider component 10 4 Interoperability 11 4.1 SIP Standards 11 4.2 SIP trunking by means of SIPconnect 11 4.3 Interoperability 12 5 Security considerations for SIP trunking 13 5.1 Threats 13 5.2 Importance of a stable platform 13 5.3 SIP signaling 13 5.4 Controlling media 14 6 Quality and reliability issues 14 6.1 QoS - Different service provider approaches 14 6.2 Prioritization of voice traffic 15 6.3 Call admission control 15 6.4 Poor voice quality can be a client problem, or based on the internal LAN 15 6.5 MPLS 15 6.6 Reliability of SIP trunks 15 6.7 SIP Trunking may be more reliable 16 7 Summary 17 About the Authors References The SIP Connect Spec
Abstract Back in the days of wireline 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 realtime communications possible with the protocol, including Instant Messaging, presence applications, whiteboarding 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 realtime 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 important to ensure that equipment works together. It is for this reason that standards such as SIPconnectT have become so critical. SIPconnect 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 no... [download for more]
