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IP telephony is a very exciting area for many people nowadays; even if it is really old from a technology standpoint. Protocols and technology are ready for long now but the market wasn’t according too much caution to this solution to transport voice over data network. Vendors have finally adopted the IP technology and are now pushing organizations and telcos to move to integrated service over IP networks. Taking advantage of the normal replacement of equipment bought during the pre 2000 period, moving to an IP solution is really something we can talk about.

Either you already have a functional telephony installation or you think about installing a new one, some questions needs to be answered or at least asked prior jumping in the deep ocean.

The purpose of this article is to put 12 questions that may help you for your next installation, keep these in mind when talking to your vendor or integrator.

1. Do you already have a telephony system?
2. Is your IP network ready for voice?
3. Do you have analog equipment or lines?
4. Is your voice installation split on multiple location?
5. Are you using wireless phones on your system?
6. Do you need a call billing feature?
7. Are you planning an outsourcing process of the telephony system?
8. Does telephony needs to be linked to computer systems?
9. Are you planning to exchange voice over IP traffic with telcos or partners?
10. Are you using a call-center?
11. Are you monitoring or recording your phone calls?
12. Are you using a automated call system?

1- Do you already have a telephony system?

Starting a telephony system on a brand new site (or renovated one) is very different from changing a running one. Today, a new installation would probably be running over IP since vendors are suppressing their traditional solution from the portfolio, furthermore, integrators are pushing towards IP installation since they are generally more expensive and allow data product sell in addition (like data switches or cabling).

A new site will probably be installed with an up to date cabling system supporting high speed Ethernet networks up to gigabit¹, thus no constraints at this level to start an IP telephony system. On top of cabling, Ethernet switches are today supporting quality of service² and virtual network³ which are useful for voice quality.

On the other hand, for an existing site which runs standard telephony, either analog or digital, migration towards IP could be more complex. First of all it is mandatory to have all features from the old system to the new one, which can be a nightmare in some cases where features are complex to reproduce. Once the telephony solution is chosen, the IP network should support the new traffic, we are not talking here about bandwidth but more quality with packet loss and jitter (see question 2).

Next we have to talk about how to power each phone. On traditional installation each phone is powered by a central point and the power is transported on the dedicated cabling infrastructure. Since traditional PBX are coupled to a secured powering solution with batteries, the phone system still provide service even in case of power outage, this is really a good thing for emergency calls even if now we can sometimes rely on cellular phones.

In the ToIP world the model is distributed, this means that telephony features are embedded directly inside IP phones. We should therefor provide each IP phone with its own power either through a wall mount adapter or through a power over Ethernet solution⁴. The impact with power outage is real in this case: for adapters the wall circuit should be secured, in the case of PoE switches the closet where it resides should be secured. In either case it could be necessary to rethink the electrical power installation.

On an existing installation it is sometime possible to add an IP component allowing to install IP phones in addition to the traditional ones. This approach ease the migration towards IP and can be interesting from a financial point of view since the investment on the IP phone⁵ can be delayed over time. One can, for example, change a standard phone to an IP one when first is broken. Be careful to check that the IP phone is providing the same service level as a traditional one, it is not always the case.

Finally a human point: with an existing installation, sometimes people are dedicated to its maintenance and administration. These people will have to be trained to the new system but probably on the IP world as well. This is really an important point in order to maintain smoothly the service level while changing the technology.

1. be careful to IP phones with integrated Ethernet switch which runs most of the time at 100Mbps [↩]
2. QoS [↩]
3. VLAN [↩]
4. see IEEE 802.3af [↩]
5. expensive part of the installation [↩]

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