We have put together some items that you may wish to check / further investigate before you carry out any VOIP Install.
Ensure the Internet line has Quality of Service (QoS) i.e Voice is prioritised over data, ideally a dedicated fibre line such as BT infinity.
Ensure a VOIP enabled router and correct firmware is being used - recommendations on our wiki; Router Recommendations
The router has SIP ALG Switched off; see Supported Routers for advice on disabling SIP ALG.
Bandwidth planning has been undertaken; see Bandwidth Planning for our handy planning guide. Ideally we recommend a dedicated line for VOIP, but if you * are planning on using an existing internet line, just check to see if you have excessive downloads, or indeed what is left on the line after normal networking takes places. You can find this out by going to www.speedtest.net.
Have babblevoice compatible handsets been chosen, if an alternative handset has been chosen, has one been sent off to babblevoice for testing?
Have you considered all the other equipment in your office? Old network switches, or network switches which are daisy chained together will cause huge quality issues, save yourself some hassle and update to the new smarter switches. If you are going to use PoE phones, then look at purchasing a PoE switch, it be more cost effective than separate power supplies per phone?
If you are considering using softphones on computers? Consider the capability of your user and also the quality of the computer and headset you intend to use with it. Have a look at Supported_Phones for more information on specific phones. If you are unsure, you will get less issues if you run with a good Polycom phone.
Are you planning to migrate existing numbers; see Porting for our porting of numbers document.