Monday 13 August 2012

Trust all Your Businesses Phone Calls to a Cisco SIP Trunk

By Rolf Versluis


There is a great new technology that is used to bring phone calls into a business phone system that provides lower monthly costs and a better level of reliability. It is named a Cisco SIP trunk, and it is worth looking at ways it can help your organization. The only catch is that your organization has to be using a Voice over IP telephone system in order to take advantage of all the benefits, however, in most cases the monthly cost savings from changing over to a Cisco SIP trunk with a Cisco VoIP phone system can pay for all of the costs to upgrade to a VoIP phone system!

Most organizations that have more than fifty phone users have a kind of business phone system called a Private Branch eXchange, or PBX. This system allows users to call each other quickly, and to share the circuits that are provided by the phone company for outside calls. The circuit that connects the organization to the phone company is most often a type of voice T1 called an ISDN PRI, which can have 23 concurrent calls on it, and costs typically $600/month. A T1 can also be used for other reasons, including providing data connections in the form of Internet or a private Wide Area Network such as MPLS. Because all business locations require voice service as well as data service, most typically have multiple T1 connections coming into each of their sites. A Cisco phone system can work with regular voice T1's as well as a SIP trunk, making the conversion very straightforward.

One of the big advantages of SIP trunking is cost savings. For example, a business that has 10 locations, each with a voice T1 and an Internet data T1, can reduce their costs enormously. An Internet T1 is about $600/month, whereas an MPLS T1 costs less at about $450/month. It is possible to reduce a $12,000/month data and voice circuit cost to about $7000/month by putting in place SIP trunking and an MPLS private network instead of voice T1's and Internet T1's. This leaves $5000 extra every month that can be used to pay for the purchase of equipment and installation services for a VoIP phone system. If the telephone system is financed over a 3 year period, that provides a total budget of about $180,000 for a new telephone system.

There are additional cost savings from circuit consolidation. SIP trunking can be used to consolidate unused circuit channels from the telephone company. With traditional voice T1 circuits, If a location requires that more than 23 concurrent calls be completed, a second T1 has to be added, bringing the total circuit capacity to 46 concurrent calls. The higher capacity is only available for that site. It is very different with SIP trunking. In most situations the SIP trunk is priced for aggregate concurrent calls for the whole organization, which means utilization is higher and monthly costs lower.

Another advantage of SIP trunking is reliability. The SIP trunk phone calls are sent over a data network to a voice gateway that can terminate the SIP call. It is over an IP connection. If the first location the call is directed to is unavailable, then a second and possibly third location can terminate the call. That means if a remote office location is not available due to power outage or natural disaster, the calls can still be sent to a person on the phone system who is available. This allows the business to continue to provide customer service to the caller and not just give a busy signal, which is what the caller would receive if the call was directed to a voice T1 connected to a PBX that was turned off.

Just like any newer technology, there are many details that have to be addressed in a SIP trunk deployment. When a SIP trunk upgrade is combined with a phone system changeover, there are more details and potential issues. For most organizations, the cost savings, improved availability and increased productivity from a new phone system make it a worthwhile changeover. SIP trunking combined with a VoIP phone system is a project that should be on every business's future plans.




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