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SIP Trunking 101 – The Benefits and Challenges

Session initiation protocol (SIP) trunking is playing an increasingly important role in enterprises and their contact centers. SIP trunking, a service offered by Internet telephony service providers (ITSP), is perceived as the preferred method for delivering telephony and unified communications services to enterprises. SIP trunking makes it possible to connect a private branch exchange (PBX) to the outside world using end-to-end Voice over Internet Protocol (VoIP). This is advantageous because SIP trunking allows organizations to replace legacy time division multiplexing (TDM) circuits with a single data circuit, much like an Internet connection. It simplifies the transition to end-to-end IP telephony, which is the foundation for deployment of unified communications (UC).

In the last few years, enterprises have been migrating to SIP trunking to reduce the complexity and cost of their telecom environment. The key benefits that organizations are realizing from implementing SIP trunking are:

  • Eliminating the need to purchase and maintain costly legacy TDM circuits, voice gateways or telephony line cards
  • Facilitating the convergence of voice and data on a single trunk, simplifying the operating environment
  • Establishing a communications infrastructure and foundation for unified communications, which allows organizations to deliver and handle multiple types of real-time interactions (voice, video, and data) on a single trunk
  • Ability to scale up or down more rapidly than TDM-based trunks, as business requirements fluctuate
  • Enhancing disaster recovery and business continuity plans by providing redundancy, using multiple service providers and links; this allows instant rerouting of communications traffic when systems issues arise

Although there are proven benefits that organizations are realizing from using SIP, the following challenges need to be considered:

  1. Provisioning adequate bandwidth – Organizations must ensure that they have the proper bandwidth to carry peak traffic volume. Inadequate bandwidth can lead to poor voice quality and blocked calls, while over-provisioning the circuit could erode potential savings. To address this issue, organizations should perform a traffic analysis to determine peak call volume and the required size of SIP trunks.
  2. Understanding the complexity in integrating SIP devices – Implementing equipment from multiple vendors has always been a challenge. Unfortunately, this issue is of particular concern with SIP, which requires integration of multiple devices, including Internet Protocol-Private Branch Exchanges (IP-PBXs), SIP proxies, session border controllers (SBCs), and the carrier’s network. To address some of this complexity, the SIP Forum has published the SIPconnect 1.1 specification, which presents best practices for enterprise-to-service-provider connectivity.
  3. Minimizing security risks – Because SIP trunks are connected to the Internet, the telephony environment is exposed to threats such as denial of service (DoS), eavesdropping, and VoIP spam. These risks can be mitigated by deploying intelligent border elements such as a SIP-enabled firewalls or SBCs, in conjunction with a SIP server that is used to manage the traffic flow. These devices enable organizations to combat attacks on their networks by applying authentication policies and ensuring proper routing.
  4. Planning for number porting – Transferring existing numbers from the TDM trunk to the new SIP environment must be addressed as part of the migration strategy. Porting is performed in real time, and needs to be coordinated with the ITSP(s). The new SIP environment must be ready for production before porting begins, as once the phone numbers are ported, it is difficult to reverse the process.

SIP trunking is ready for prime time, having proven that it can deliver operational efficiencies and cost savings to organizations. But to achieve the expected benefits and savings, SIP trunks must be implemented in a secure manner that optimizes telephony resources and ensures interoperability between VoIP components and the ITSP(s). SIP trunking also positions businesses for global connectivity and seamlessly extending communications capabilities to anyone outside of the corporate network, as needed. So, when building a next-generation contact center, it’s important to include SIP trunking in the plans, as it will enable organizations to more flexibly and cost effectively respond to changing business needs.


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Ask the Experts

Should companies abandon asking for surveys on receipts, sending email surveys, and forcing pop-up website surveys? Wouldn’t they be better served to exclusively use Social Media as a conduit to their clients concerns and feelings (both good and bad)?

No to both of your questions. “Surveying” – which is where a company solicits feedback can be a very positive activity – when it’s done right. But, these are the operative words – doing it right. Few companies know how to do it right, which includes having a corporate surveying strategy, applying findings on a timely basis and getting back to participants to let them know how their feedback was used.. Secondly, customers must have the option to use their channel of choice; this includes paths for capturing voice of the customer. Restricting feedback channels to social media exclusively will also skew the results as there will be many demographic groups not adequately or accurately represented.

Social media is powerful and we (the world at large) is just beginning to figure out what to do with social media. It is exciting and has unbelievable potential. It can (and should) be used as an input stream – but organizations should not close off other input streams…Read More

DMG Consulting LLC is a leading independent research, advisory and consulting firm specializing in unified communications, contact centers, back-office and real-time analytics. Learn more at