Wednesday, August 29, 2012

Cisco SIP Trunk Deployment Secrets

By Rolf Versluis


There is a interesting new technology that is used to bring phone calls into a business phone system that provides lower monthly costs and a higher level of reliability. It is named a Cisco SIP trunk, and it is worth evaluating ways it can benefit your organization. The one thing you need to know is that your business has to be using a VoIP telephone system in order to take advantage of all the benefits, however, in some cases the monthly cost savings from changing over to a Cisco SIP trunk with a Cisco VoIP telephone system can pay for all of the costs to upgrade to a Voice over IP telephone system!

Most businesses that have more than sixty phone users have a type 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 telephone 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 traditional voice T1's as well as a SIP trunk, making the changeover very straightforward.

One of the big advantages of SIP trunking is cost savings. For example, a business that has 10 sites, each with a voice T1 and an Internet data T1, can reduce their costs significantly. 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 voice and data circuit cost to about $7000/month by putting in place SIP trunking and an MPLS wide area network instead of voice T1's and Internet T1's. This leaves $5000 extra every month that can be used to fund the purchase of equipment and installation services for a VoIP telephone system. If the telephone system is financed over a 3 year period, that provides a 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 calls are sent over a data network to a Session Border Controller that can terminate the SIP call. It is over an IP connection. If the first SBC the call is sent to is unavailable, then a second location can receive 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 lets the business to continue to provide customer service to the caller and not just deliver a busy signal, which is what the caller would get if the call was sent to a voice T1 terminated by 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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