When it comes to redundancy there are many factors to consider.  In general, you will make the decision for you company that you are most comfortable with.  You can always spend more money and as some point you will decide that the cost is not worth the risk.    A Larger company with heavy phone dependency will obviously be much more concerned with designing redundancy in to their solution.  SIP or Session Initiation Protocol provides a new level of redundant options and that is another reason companies are flocking to SIP.   In this blog I want to talk about a couple applications that are most common.

When it comes to the dial tone carrier there are a several ways to design redundancy.  Let me explain a few Scenarios:

The most common issues with a carrier are that the T-1 goes down because the cables were cut, or that the terminating equipment on site or in the Central office has an issue.  Depending on the issue it can be down for 30 minutes to hours or days in the event of a cut cable in the street.

SIP carriers can have multiple routes assigned in the phone system.  Thus the primary route can be directed towards the T-1’s but they could have a secondary route across a separate connection entirely.

This takes working with the Carrier to design this but the result is that if the T-1 goes down completely then the SIP carrier will see that the connection is down and automatically reroute over their secondary route.

So what would that secondary route be?    In general we like to use networks that would not travel in the same paths in the ground.  We often look to a cable company or Business Class Wireless to deliver our redundant connections as they have separate networks.

This does take a little work to get it set up with the carrier, program the phone system, and configure your onsite equipment but it is straight forward.

Carrier Goes Down:

This is much more unlikely but it does happen where a carrier can go down for a period of time.     If the carrier goes down then any number that is assigned to that carrier will be out of service for inbound and you won’t be able to pass outbound calls through the carrier either.

Outbound is easy to resolve because we can set up multiple SIP carriers on the Zultys and easily reroute outbound calls over an available internet connection.    Where you get stuck is on inbound because if the carrier that goes down is the one that owns your number there is no way to reroute those calls.    Some customers have their 800 numbers hosted with a separate carrier from their local carrier so they can reroute the 800 calls easily to a different carrier.  This solves the local carrier going down but you are in the same situation if the 800 provider went down.

The bottom line is that SIP gives you great flexibility and better redundancy with secondary routes and the ability to provision multiple carriers if you choose to design it that way.

Hopefully this helps.  We would be happy to discuss further and to help you design a solution.