Many companies still run an old PBX: the number of extensions is limited, adding a new line is difficult, calls between branches cost money, and there is no reporting on missed calls. IP telephony (VoIP) carries calls over the data network and removes all of these limitations.
Components of a VoIP System
- IP phone system (IP-PBX): the brain of the system, which manages extensions, call routing, the auto attendant and queues. Many IP phone systems are built on the open-source Asterisk software and run on a server or virtual machine.
- Phones: desk IP phones or softphones on computers and mobile devices.
- External connectivity: landlines through a gateway (a device that connects analog lines to the network), or a SIP trunk from an internet telephony provider.
- Network: switches, ideally with PoE to power the phones over the network cable.
Features You Gain with VoIP
- Auto attendant (IVR): “Press 1 for sales and 2 for support.”
- Call queues: when all agents are busy, callers wait in a queue instead of hearing a busy signal.
- Call recording: for training, quality control and resolving disputes.
- Call reports: how many calls came in, how many went unanswered, and the average wait time.
- Extensions for branches and remote staff: all branches and remote employees on one system, with free internal calls.
Before Deployment: Prepare the Network
VoIP call quality depends on the network more than anything else. Voice is sensitive to latency, jitter and packet loss; issues that go completely unnoticed when downloading a file show up as choppy audio on a phone call.
- A separate VLAN for phones: separate voice traffic from computer traffic.
- Traffic prioritization (QoS): voice traffic should have the highest priority on switches and the firewall.
- Sufficient bandwidth: each concurrent call needs a certain amount of bandwidth, depending on the codec. For external or inter-branch calls, size your internet link capacity based on the maximum number of concurrent calls.
- Check SIP ALG: on many routers and firewalls, this feature causes one-way audio or dropped calls, and it is usually best disabled.
Signs of network problems in VoIP: one-way audio, choppy audio, calls dropping automatically after a few seconds, or noticeable delay in conversation.
Take Phone System Security Seriously
A phone system exposed to the internet without protection is a target for attacks that use it to make expensive international calls at your expense.
- Do not expose the management panel and SIP ports to the internet, or restrict access to specific addresses.
- Set a strong, unique password for each extension, not simple passwords such as the extension number.
- Remote employees should ideally connect through VPN.
- Block international calls if you don’t need them, and set limits on expensive calls.
- Keep the phone system software and phone firmware up to date.
Steps for Migrating from an Old PBX
- Document your current extensions, lines and call handling scenarios.
- Design the extension plan, auto attendant menu and queues.
- Prepare the network, then deploy and test the phone system.
- Move landlines to the gateway; the company’s phone numbers do not change.
- Install the phones and train users on transferring calls and using the new features.
Checklist
- An IP phone system on a stable server or virtual machine
- A separate VLAN and QoS for voice traffic
- Enough bandwidth for the maximum number of concurrent calls
- Protected management panel and SIP ports, and strong extension passwords
- Auto attendant, call queues and missed call reports
- Backups of the phone system configuration
ITPlus724 engineers design and deploy IP phone systems, prepare the network for voice, and bring your company’s branches and remote staff onto a single system.