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The Buzz Around SIP

VoIP SIP is being marketed under the banner of Unified Communications. "SIP" or Session Initiation Protocol is a signaling protocol used to make internet telephone calls. There is a lot of buzz that this service is going to single handedly replace the Central Offices. SIP Trunks are no magic bullet at this stage in their development. This is a data service that is trying to be like voice and falling short. It works fine in small offices. It is a technology to watch and if the functional bugs are worked out it has potential to be a useful part of your toolset if the pricing stabilizes and the cost for Connections gets more realistic. The SIP community is trying to model something new and yet they charge for connections as if they are trunks. These are not anything like what you are used to. Unified Communications has been an erector set since inception. New technologies like SIP are always surrounded by 'forward looking statements' and SIP is no exception. There are wide variations in implementations by the vendors. Not all that glitters is gold. Hospitals Should Not Adopt SIP For Cost Savings

The SIP Pricing Model provides cost savings if you can put all your communications eggs in one basket. First Responders require service stability foremost and use service diversity to improve reliability. This service is a mismatch for the communications objectives of a hospital. Durability trumps savings every time. SIP is not a direct replacement for existing voice services.

SIP has limitations including built in call blocking. In a small office or clinic you may not notice the blocking because the call volume is low. In a mid sized Hospital this problem directly impacts groups that have peak call activity times like Surgery or Radiology Scheduling. During emergency situations the call blocking can become a critical issue. Here's how the problem manifests operationally: Callers may complain that they can't get through. The recordings are generic so the caller does not know who to tell or what caused the issue. Your technical staff can't find anything wrong.

Here is what is going on. SIP has a system limit on the total number of Calls Per Second (CPS) that can be processed. When the CPS threshold is exceeded, callers are played a recording to 'please hang up and try again later'. Two calls per second is considered normal so all others calls above this limit get the recorded message. Your SIP provider will point to their contract terms posted on the web in a technical document that explains CPS and report that it is operating according to specification. Purchasing SIP Connections (These Are Not Like Trunks) There is no relationship between the number of connections that you purchase and the number that you can use because of the CPS interaction. Make sure you understand your use cases for SIP services. The average person would conclude that 72 calls at a time would be possible given the following:

You purchase a High Speed Internet Connection and pay for all the bandwidth. You purchase 72 SIP Sessions -- virtual (software) connections that use the Internet Connection. You purchase 500 Direct Inward Dial Numbers

The Call Per Second (CPS) setting will limit the total number of connections that can be accessed, not the number of sessions purchased. This is something very different indeed and warrants investigation. Corilate, Inc. has a unique process to remotely identify, document, and verify that every telecom service you pay for is actually connected and being used -without CapEx. Contact us for a free healthcheck at 714-267-0864 or email

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