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SIP Trunking: When Disaster Strikes

Maybe the Internet ran out of bandwidth or someone didn't pay the light bill, but our SIP trunks were down for 2 hours and 15 minutes. This isn't the first outage we've experienced and I don't think it will be the last.As usual, I start early and get the coffee brewing and as I've commented before--I've mapped an alarm button to my phone for any minor or major alarms in our IP-PBX. It seems that the past failures are in the mornings.

I pondered over the last trouble where I went through the routine--packet trace to see what was going on, checked the firewall log, rebooted the SIP gateway first, then the IP-PBX and finally the router. Still no-dial-tone. I did all the work and called in a ticket and was told the problem was my end since the provider wasn't getting authentication information. It was a day that was already dedicated to service our customers, not our internal issues with SIP trunks. Thank heavens our SIP trunks are just cheap long distance for us. Several hours later the trunks started working again and sorry but I have to say it--all by themselves!

This event was different though because before I stopped thinking about it and whether or not I would even call the provider I got an email informing me about a network emergency. The problem was a failure due to a change in a different NOC than the NOC serving us.

What can you learn from my lesson?

First, be sure to make the coffee first. Don't assume that it's your problem. Then, for those that are more dependent upon SIP trunking, you must ensure that you have more than one backup route, two is better and depending upon the complexity of your network you may want to have more than one provider for greater diversity as I mentioned in SIP Trunking: Alternative Routing. You may have redundancy within your site but you must consider the provider and counter issues that they will encounter. By quick math -five nines isn't in the picture and neither are four nines reliability for this provider. They are at three nines if I don't count the past issues. Verizon brags that their network is .999 reliable and is far superior to VoIP/IPT networks. When I count the time for the rebooting frenzy on our side of the network it makes our network reliability look pretty lame and it isn't. You may also want to consider using standalone gateways for cellular backup too, which is a pretty cool way to use cell-to-cell to avoid airtime charges when calling employees in the field. Multitech makes a slick gateway to use a cell card (or cards for multiports) and connecting the box to a CO port(s) on your PBX/IP-PBX. Whatever you do make sure you have backup routing and plan for disaster because it will strike. In our IP-PBX the SIP trunk failure creates a no-channels available condition in the trunk group and our ARS/LCR automatically pick beyond these channels so there is no disruption for the users. I give my provider credit--they sent me emails about the outage and followed up except for the RFO (Reason for Outage). I wonder whether or not my provider will give me credit on the next bill--.00336021505% down = 7 cents credit? Seriously, make sure that your provider can do the same by emailing a list or key people maintaining your network because it may save some time and give your folks opportunity to make the brew before meeting the day head on.

Now whether or not you believe than an all IP public network is possible, one thing remains constant and clear. In the old days, rebooting wasn't the norm for telephony unless you're talking about unprotected key systems with no power protection and battery backup. Today, reboot reigns in the IP world and in my case I elected to play the game until it cut into my coffee time. I'm not giving up my Centrex service from Verizon and I'm not giving up my cheap long distance service by way of using SIP trunks. When I get inspired enough, maybe I'll explore other options but the reality remains that will happen only when the rest of the industry catches up. I have to add as I wrote long ago--my 2500 sets aren't going away either. That includes the connection to the DirecTV box, alarm system and other devices using 2500 ports.

As much as some folks want to wish away TDM or sound the death bell for the technology another reality that they don't understand escapes them. Don't get caught in the middle and don't get left behind. I've got a great IP box that just happens to do all the TDM and analog things we don't want to give up. Our loss of SIP trunks was no disaster but how would your configuration fare had your SIP trunks been down for 2.5 hours? What is the cost for re-routing your traffic? Did you have disruption to personnel? Was the disruption transparent to your operation? These are some of the questions you need to address before making your pitch for lowered costs because without them the potential to wipe out the savings lies within your configuration and dependence upon one vendor.