VoIP explained

Voice over IP (VoIP) carries phone calls as data over your network and the internet instead of over traditional copper phone lines. It is now the standard for business phone systems, offering features like softphones, call routing between offices and voicemail to email. Call quality depends on the network, so a VoIP project is as much about switches, cabling and bandwidth as it is about phones.

How a VoIP call works

A phone or softphone app turns your voice into digital audio using a codec, splits it into small packets and sends them across the network. A call control system, usually using the SIP protocol, sets up the call, rings the other phone and tears the call down at the end. Calls to the outside world leave through a connection to a phone carrier, such as a SIP trunk.

Codecs trade audio quality against bandwidth. G.711 is uncompressed narrowband audio and is common on trunks. Wideband codecs such as G.722 and Opus sound noticeably clearer. Compressed codecs use less bandwidth, which mattered more when links were slower.

Hosted vs on-premises

Hosted systems, often bundled with messaging and video as unified communications, suit most small and mid-sized organizations. On-premises systems remain common where integration, control or local survivability matter, such as healthcare, manufacturing and sites with unreliable internet. Hybrid designs also exist.

Features worth planning

A new phone system is a chance to rethink how calls are handled, not just to copy the old setup. Before configuring anything, decide:

• Call flow: who answers the main number, what happens after hours, and where calls go when nobody picks up
• Auto attendants and hunt groups: menus and groups of phones that ring together or in turn
• Softphones and mobile apps: which staff work remotely or on the move and need their desk number on a laptop or phone
• Integrations: links to contact centre tools, customer records, paging, door intercoms or nurse call
• Recording and reporting: whether calls must be recorded, and how long records are kept under your privacy obligations

What the network needs

Voice is sensitive to three things more than raw bandwidth:

• Latency: delay from speaker to listener. Too much and people talk over each other.
• Jitter: variation in delay between packets, which causes choppy audio.
• Packet loss: missing packets, which cause gaps and robotic sound.

A network ready for voice usually has:

• Managed switches with a separate voice VLAN
• Quality of service configured end to end; see QoS for voice and video
• PoE switches to power desk phones, on UPS
• Internet bandwidth sized for peak concurrent calls, with traffic shaping at the edge
• WiFi designed for voice if wireless handsets or softphones on mobile devices are used
• Firewall settings that handle SIP correctly, without problematic SIP helper features

Planning for outages

A VoIP phone needs network power and connectivity. To keep phones working in a power or internet failure:

1. Put switches and the phone system on UPS, sized for PoE phones.
2. Provide a backup internet connection or carrier failover for hosted systems.
3. Configure call forwarding to mobile phones if the site goes offline.
4. Review which lines must work in any outage, such as elevator phones, alarm communicators and emergency phones, which may need dedicated solutions.

Those special lines are covered in moving from landlines to VoIP.

How ehZee can help

Through our VoIP design and build service we start by asking how your people use the phone today and what they need, then check the network, design the system and build it, and test call quality before cutover.

Common questions