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VNet Professionals Inc. Voice Solution

About SIP, Analog and PRI Trunk

What is a SIP Trunk?
A SIP Trunk is primarily a concurrent call that is routed over the IP backbone of a carrier using VoIP technology. VoIP is the promise and SIP is the delivery on that promise. Many years ago there were issues with VoIP as the infrastructure could not handle the sensitivity of VoIP. And now SIP Trunks are becoming the norm in all our phone system installations, SIP is used in conjunction with an Allworx IP Phone System and is the replacements for traditional PRI or analog circuits. The popularity of SIP Trunks is due primarily to the cost savings and the flexibility, along with the increased reliability as backed by the SLAs of SIP Trunk Providers.

What are the advantages of SIP Trunks versus Analog Circuits?
SIP Trunks are less expensive than analog circuits while maintaining the same service quality that businesses expect from line quality. SIP Trunks cost approximately $12 to $25 per trunk with usage included, versus $35 per analog circuit with no usage (these prices may vary depending on the carrier.) In addition, long distance termination charges associated with SIP Trunks are much cheaper than traditional analog or TDM rates.

What are the advantages of SIP Trunks versus T1/PRI?
SIP Trunks realize their primary benefit over T1/PRIs from cost savings, and keeping many of the benefits of a traditional T1/PRI such as DID and outbound caller ID, etc. SIP trunks typically cost $12 to $25 per trunk for unlimited inbound and local calling along with a long distance rate that can be under 2 cents per call. When coupled with line oversubscription (e.g. a 20 person company purchasing just as many SIP trunks as they anticipate having concurrent calls….typically 8 to 10) SIP Trunks are a very cost effective way for a business to save money. Lastly, a primary benefit of SIP Trunks over PRIs is that SIP Trunks can be purchased in increments of 1, whereas PRIs have to be purchased in increments of 23 channels or a fraction from the first.

Do business need SIP Trunking instead of Analog or T1/PRI?
A business should look into purchasing SIP Trunks when they decide to replace the current TDM phone system or when the business dictates the need to lower telecommunications cost. When the phone system cannot handle the current volume of calls and replacing the phone system is part of the growth, it is the right time to change for a more cost effective means of doing business. In conjunction with an IP-PBX (our choice is Allworx.) Coupled with SIP Trunks, an IP-PBX serves up similar features as a digital system without the cost of the T1 interface witch is the most expensive part of the phone system. SIP Trunks typically save our business customers money over any other solution in that a SIP Trunk can increase or decrease serving the seasonal needs for any business.  This is one ability that cannot be said from any other medium. With analog you need a truck roll and possibly more hardware to sustain the additional coper phone lines.  With a digital T1 you are certainly investing in up front hardware at a higher cost. SIP is so flexible that you can grow your business without a truck roll and without expensive hardware.

What equipment will I need to be able to use SIP Trunking?
SIP Trunks work with a SIP-ready PBX. Allworx is SIP native (ready out of the box) and has no need for additional hardware or software. Allworx can also be made to work with traditional analog or key systems replacement as it connects directly to the carrier’s IAD (Integrated Access Device) which is no cost to you the client. There is no need to test interoperability with any solution we sell as the testing and underlying equipment has been tested by the manufacturer with the carrier of your choice. However, it should be noted that with the advent of standards around RFC 3261 and SIP Connect, we have identified and found SIP Trunk Service Providers with SIP Trunk compatible equipment that is reliable and we have significantly increased our compatibility success.

Would I need more Internet bandwidth when using SIP Trunks?
SIP Trunks are virtual circuits delivered over an Internet Access, in other words they are part of your Internet access bandwidth provided by your carrier. Depending on the number of SIP Trunks purchased (from 1 to 99,) and the amount of excess Internet connectivity, a business should consider purchasing more Internet Access. There is a simple formula to calculate this. However, it’s important to know that when a SIP Trunk is not being used, the bandwidth otherwise allocated to a SIP Trunk is freed up for use in less intensive applications, such as e-mail and general web use. This dynamic allocation of bandwidth is yet another great feature of SIP Trunks versus more traditional technologies. If you can imagine a freeway with car pool lanes (this would be your SIP trunks) when they are in use these lane allow for dedicated voice calls.  When they are not in use they increase your Internet bandwidth.  This is just a smarter way to use the resources you have.