The key components to a basic VoIP installation are:
- Gateway. This is the hub of the network that replaces the traditional PABX rack. These can be wall mounted or rack mounted and take on a multitude of sizes and form factors. Most have the ability to take one or more blades, which enable the interconnects with the outside world and normal telephone system. Most also incorporate some level of autosensing directory service and device registration capabilities, along with the voice mail system and call control/logging functionality.
- Routing and switching. This is mostly done with standard network routers and switches; some gateways have routing built in.
- Cabling. Good old "bluey" RJ45 cabling and termination is all that is required.
- Handsets. An overwhelming array of handsets is available from all VoIP vendors. These "transparently" replace the traditional handset, but are far in advance of regular dumb handsets. Smart VoIP handsets incorporate their own CPUs, memory, storage (in some cases), as well as some of them having integrated, routers, firewalls, switches, management software, and even calculators.
- Soft phones. These can replace or augment the deployment by transferring all functions of the handsets and their displays onto a client PC. As long as it's equipped with microphone and speakers or a headset, a PC can totally replace the desktop handset. This is very popular in call centres.
Important issues to look out for include:
- Security. Right from the get-go ensure that your plans revolve around security, security, security. It is bad enough having data leaks from sniffers picking up e-mail transmissions or hackers gaining unauthorised access to your servers, but to have voice calls intercepted is beyond the pale. Ensure your VoIP data traffic security is as good if not better than your normal data traffic security. Encryption is one of the keys currently accepted to protect calls; most if not all vendors offer encryption of some level across their systems.
- Load testing. Ensure your existing network will cope with the added load of a VoIP deployment, or plan to add another network for the VoIP system.
- Location. Make sure the placement of the PSTN interconnects or gateways will benefit your company financially by reducing the cost of telephone bills (using toll bypass). This may even include the necessity to set up PSTN gateways in several remote offices to take advantage of the reduced interstate or overseas call rates. If this is the case, a robust VoIP routing system needs to be developed so that the calls are routed correctly through the right gateways with a sufficient amount of available bandwidth to maintain the quality of the call.
- Redundancy. Always have a backup plan; redundancy is not a luxury or option when it comes to telephony systems. Any company worth its salt when implementing a VoIP solution must ensure that there are alternative routes and options available should the worst happen and the IP network or links stop working. Consider having PSTN gateways as a backup at all offices, even if these only have a low ratio of ports per user available, it would still allow calls to be received and placed should the main Internet or VPN link go down.