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SIP trunking and how it can benefit you

Solution What you need to know about SIP trunking and how it can benefit your business

A SIP (Session Initiation Protocol) trunk is a service that allows businesses with an installed PBX to use real-time communications including VoIP. By connecting a SIP trunk to an internal traditional PSTN (public switched telephone network) phone system, companies can communicate over IP outside the enterprise. What’s more, companies can replace traditional fixed PSTN lines with an IP phone system connected externally through an SIP-trunking service, thereby creating a single conduit for multimedia components including voice, video and data. As a result, an SIP-trunking service typically delivers greater cost savings and increased reliability.

How SIP Trunking Works

SIP trunking blends connections for both data and voice into a single line. By serving as a converter between a legacy phone system and a company’s Internet connection, an SIP-trunking device allows the data network to carry voice traffic. Our SIP-trunking features include local and long-distance calling, E911, directory listing and caller ID, all of which integrate into a company’s existing phone system.

Here’s a hypothetical example of how SIP trunking works: A San Francisco-based sales representative places a long-distance call to a client based in New York City using a dialing prefix and the local-area phone number. The call either originates as an IP call or is converted to one before it leaves the office and then travels the majority of the way over our IP network, then drops back down to the PSTN once it reaches its termination point. Since a sizable portion of the call traveled over our IP network at no additional cost rather than on the PSTN, we can charge a mere fraction of what the traditional fee would be without our IP connection.

SIP trunking consists of three primary components. These include:

IP PBX: An IP-based PBX communicates with all endpoints over an IP network. It also switches calls between VoIP users on local lines while allowing all users to share a number of external phone lines. The typical IP PBX can additionally switch calls between a VoIP user and a traditional-telephone user, or between two traditional-telephone users in the same way that a conventional PBX does.

Our role (Best SIP & VoIP) is to ensure connectivity to the PSTN from an IP network for your mobile and fixed communication devices.

Border element: The border element facilitates connectivity between an enterprise IP network, Best SIP & VoIP and our external IP-carrier network. The border element may be an SIP-capable firewall or a SIP-enabling edge device connected to the firewall, or it can be a switch to transfer calls into and out of the PSTN. Border elements are usually managed by us.

Note we will typically include SIP trunking as an element of an IP-phone-system package; it will only be separated into hybrid solutions when there is a need to maintain some locations on a traditional TDM (time-division multiplexing) system, which will connect to the overall IP infrastructure through various border elements and our SIP-trunking service.


Our SIP Ttrunking service benefits companies by:

* Eliminating the need to invest in costly (and less capable) TDM-gateway equipment infrastructure or desktop equipment
* Nullifying the need to purchase equipment, such as managed-media gateway devices, to interface between IP voice and the PSTN
* Reducing monthly expenses, since only one connection for data and voice is needed
* Eliminating the need for PRI (primary rate interface)/BRI (basic rate interface) connections, lowering telephony costs
* Allowing companies to outsource their PSTN connectivity to us, reducing long-distance charges
* Providing points of presence in multiple U.S. cities so that companies can establish local numbers rather than rely on a 1-800 number
* Accessing the benefits of a hosted VoIP service, without discarding existing investments in a traditional phone system


Although we offer SIP-trunking services with many options at varying costs, it is not uncommon for companies to realize instant cost savings from a relatively modest investment in SIP-based technology. Certainly, SIP requires purchasing services and products including an IP PBX, IP phones, soft clients and SIP-friendly firewalls, to name a few out-of-pocket expenses. But if deployed properly, SIP trunking can produce a healthy return on investments in less than six months.


Whenever companies attempt to mix equipment from different vendors in a unified IT environment, problems can arise. Various equipment based on the SIP protocol is certainly no exception. That’s why companies should use established best practices for interfacing a PBX implementation with us to minimize incompatibilities.

SIP trunking can also give rise to security risks. Fortunately, SIP-server and -proxy technologies can manage the flow of SIP traffic, enabling your IT manager to ensure correct routing, apply verification and authentication policies and minimize threats.

A network-monitoring solution can also help find the best real-time traffic route for greater internal quality and reliability.
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Article ID: 7
Category: Knowledgebase
Date added: May-13-2010 17 5:24pm
Views: 733
Rating (Votes): Article rated 4.3/5.0 (98)

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