SIP Trunks and IVR

rtddirad Cloud, IVR, SIP Technology Leave a Comment

The process of procuring an IVR system is arduous enough, but then you have to trunk it. What? If you IVR is going to sit at your facility, you’ll need phone lines to feed it. There are a few ways to do this:

1. Order “legacy” PSTN service from your telco provider. An example would be ordering an ISDN/PRI circuit that can handle 23 concurrent calls. If your IVR is from this century, you’ll need a gateway to convert the signal to Session Initiation Protocol (SIP).

2. Use your current PBX to provide lines to the IVR. Lines can take the form of physical, circuit-switched (legacy) connections, or SIP. For this, a gateway is not necessary because you’re already using SIP to access the IVR.

3. Order a SIP trunk. This is by far the most cost-effective option with the lowest opportunity cost. SIP trunking sends calls to your IVR via your internet connection.  Broadband at 5MB would probably be the minimum, although you can go lower depending on other demands from your network.

The advantages of SIP trunking include:

Usage-based billing. While a PSTN commands a big bill every month regardless of use, a SIP trunk bill is based on usage. The bonus is that SIP trunking has yet to be exploited by politicians looking for more tax revenue, so you’ll see less of that than you’re used to. Unfortunately, we think the politicians will catch on soon, especially since Net Neutrality will allow for greater regulation. This will drive costs up, so enjoy it while it lasts.

Simplified Disaster Recovery Routing: Your SIP trunk can be re-routed almost instantly. Send calls to a backup IVR image in the cloud, or to an alternate location.

More than Just Voice: SIP allows you to carry media like SMS (text), video, and chat, giving your company more channels to communicate.

Open Standard: Your SIP trunk will interoperate with just about any premise-based IVR or phone system; i.e. legacy systems, with the appropriate gateways installed.

SIP Trunking Gotchas

Transfers: If your IVR will be used to transfer calls internally, let’s say to staff, the IVR needs to be able to talk to your current phone system. Ideally, your IVR, SIP Trunk and phone system will interoperate via SIP, but that is not always the case. If you’re running a SIP trunk to your IVR, but you have a legacy phone system, your transfers will either have to go back out the PSTN (creating a two-legged call) to your agent, or traverse a gateway to your PBX. More importantly, if your IVR must transfer to an external number, it is best that your SIP trunking provider supports SIP-REFER so the calls can be released after a transfer. Otherwise, you’ll “hairpin” both legs of the call and they’ll stay on your system until the caller’s session ends. There aren’t many providers that support SIP REFER. You can contact us for help with that.

Call Quality: I still hear “legacy IT guys” announce they’ll never run voice over the internet. Little do they know, almost every phone conversation these days may be traversing SIP somewhere along the call path. SIP was invented in the days of DSL. While SIP’s needs have remained the same, available bandwidth has increased dramatically. A fully uncompressed SIP call uses around 84k per user per session. Since usually only one user at a time is speaking, that 84k is not much. With IVR, it’s also possible to compress the SIP media so that you’re using even less bandwidth.

Security: SIP Trunking traverses the big bad internet. If you’re truly concerned about security but want to have the advantages of SIP Trunking, you can do an private connection to the carrier via MPLS or some other method. SIP can be secured through a number of means, including the same firewall and security technology employed to protect “regular” data. Is SIP Trunking less secure than ISDN? I would have to say yes, if you’re providing trunks into NORAD. You’ll need to weigh the benefits of SIP vs. your particular security needs.  Most commercial IVR transactions can be safely conducted via SIP.

Want to learn more about SIP Trunking? Contact me and I’ll be happy to discuss with you.

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