Voice Over IP network fundamentals?

It is really good that you are asking this question and the Consultant, if qualified, is also a good idea. I'll assume that the Consultant has set up the systems properly. It may have been more helpful to ask your question earlier in the design process. However, it is commendable to be asking it. Period.

Like any other service, as you know, telephone service should be maintained to support expected performance levels and anticipated improvements. IP Telephony (IPT) is not so different.

Quality of Service (QOS) should be correct at setup but may need adjustment, so you should revue it regularly and base changes on Performance reports.

The three main items to watch regarding Voice Performance on an IP network are Packet Loss, Jitter and Delay. You should be measuring and reporting on these items, per link, regularly to maintain service levels. WAN links should be watched more closely than LAN segments. Avaya has very good tools for this. Avaya (and many business partners) also provide a Network Assessment service that requires no capital outlay.

Security and patching are regular occurrences and should be considered recurring maintenance. Some systems require more or less patches. Through its use of the hardened Linux OS, Avaya patches are less frequent. However, they are required from time to time to maintain a secure, high performance environment as well as for adding new features.

Mean Opinion Scores (MOS) should be high (3) to meet user expectations. However, a lower MOS is not a death sentence. A good example of where users may expect a MOS lower than 3, would be an international VoIP tie-line. There will be a compromise between performance and money saved.

Moves, Adds and Changes (MACs) will be a learning curve for the administrative staff and for users. Plan to make adjustments to your plan for MACs. The impact of MACs may be minimal in an environment of 30 IP phones, but do not underestimate how often people will change the environment or personnel.

Staffing or maintenance contracts may be contingent upon MACs.

You didn’t mention Unified Communications (UC), so I assume that voice mail is the only voice messaging solution. If you are not already, you should be speaking with the business about, and planning for UC. Avaya has a very robust UC solution set.

Usage reports will still be important, just like they were in the old TDM world. They tell you where people are calling and how often.

Business recovery after a disaster should be planned for regarding telephone service and voice messaging.

The last item I will note is that of contract maintenance. These may be carrier contracts, maintenance contracts, break/fix contracts, etc. Negotiate well, but plan to renegotiate as needed. Technologies and offerings change regularly.

You should partner with a reputable Avaya reseller, but also have at least one alternate partner that you can go to should the need ever arise.

Hopefully, none of this information is new or strange to your IT department. I hope this helps you. Best wishes for a successful IPT future.