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Is Your Network Ready for VoIP? A Pre-Switch Checklist

Check bandwidth, latency, jitter, QoS, and power backup before switching to VoIP so calls sound clear from day one. A practical checklist for small offices.

One Solutions Team · · 5 min read

VoIP can give your business clearer calls, more features, and a phone system that follows your team anywhere. But VoIP is only as good as the network it runs on. Before you switch, it's worth checking whether your network is ready for VoIP, so calls sound clear from day one instead of choppy, delayed, or dropped.

Why the Network Matters

With a traditional phone line, voice travels over a dedicated circuit. With VoIP, voice is broken into small data packets and sent over the same network as your email, file transfers, and video calls.

That's what makes VoIP flexible, and it's also why network problems show up as call problems. Voice is unforgiving. A file download can pause for a second without anyone noticing, but a one-second pause in a conversation is obvious.

If you're still deciding whether to switch at all, start with our comparison of VoIP vs. landline business phones.

Check Your Bandwidth

Each VoIP call uses a fairly small, steady amount of bandwidth, but it adds up when several people are on the phone at once.

A common codec for business calls, G.711, uses roughly 100 kbps per call in each direction once network overhead is included. Compressed codecs such as G.729 use considerably less, at some cost to audio quality. Your provider can tell you which codec they use.

To estimate what you need:

  1. Count the most simultaneous calls you'd expect at your busiest time.
  2. Multiply by about 100 kbps for upload and the same for download.
  3. Add that to the bandwidth your team already uses for everything else.
  4. Leave generous headroom for spikes like large uploads or video meetings.

Upload speed is the one people forget. Many business internet plans have much less upload than download, and voice needs both directions.

Measure Latency, Jitter, and Packet Loss

Raw speed isn't enough. VoIP quality depends on how consistently packets arrive. Three measurements matter most.

Latency

Latency is the time it takes for a packet to travel from one end to the other. Widely used guidance is to keep one-way latency under 150 ms. Above that, people start talking over each other.

Jitter

Jitter is variation in latency, when packets arrive unevenly. Phones use a small buffer to smooth it out, but a common target is to keep jitter under 30 ms. High jitter sounds like robotic or garbled audio.

Packet loss

Packet loss is data that never arrives. For clear calls, aim for less than 1% packet loss. Even small amounts can cause clipped words and dropouts.

Run tests at different times of day, especially during your busiest hours. A connection that looks fine at 7 a.m. may struggle at 2 p.m. when everyone is online. Many VoIP providers offer their own network test tool, which is a good place to start.

Key takeaway: Bandwidth gets the attention, but latency under 150 ms, jitter under 30 ms, and packet loss under 1% are what actually make calls sound clear.

Prioritize Voice with QoS

Quality of Service, or QoS, tells your network equipment to send voice traffic first. When the connection is busy, a big file upload waits a moment, but your phone call doesn't.

A solid QoS setup usually includes:

  • Marking voice packets so routers and switches recognize them as high priority
  • Configuring your firewall or router to prioritize those packets on the way out to the internet
  • Placing phones on their own voice VLAN to keep voice traffic separate from data
  • Limiting bandwidth for non-urgent traffic, like large backups, during business hours

Keep in mind that QoS works best on the parts of the network you control. Once traffic leaves your office, your internet provider's network takes over, which is why a reliable connection still matters.

Review Your Network Equipment

Older or consumer-grade equipment is a common cause of VoIP trouble. Walk through these items before you switch.

  • Firewall and router: Make sure it supports QoS and can handle your traffic. Some routers include a feature called SIP ALG that is meant to help VoIP but often causes one-way audio or dropped calls; many providers recommend turning it off.
  • Switches: Business-grade managed switches support VLANs and QoS. If your phones will draw power from the network, you'll need switches with Power over Ethernet (PoE).
  • Cabling: Damaged or very old cabling can cause intermittent errors. Desk phones generally work best on wired connections.
  • Wi-Fi: If people will use softphones or mobile apps in the office, make sure wireless coverage is strong where they actually take calls.

Plan for Power and Outages

Traditional copper phone lines often kept working when the power went out. VoIP phones need power and internet to work, so plan ahead.

  • Battery backup: Put a UPS on your firewall, switches, and modem so phones stay up during brief power blips.
  • Backup internet: A second connection from a different provider, or a cellular backup, keeps calls flowing if your primary line fails.
  • Call forwarding: Set up rules to route calls to mobile phones or voicemail if the office goes offline.
  • Emergency calling: Register the correct physical address for each phone with your provider so 911 calls are routed properly, and update it whenever phones move.

Your Pre-Switch Checklist

Before you sign off on a VoIP rollout, confirm each of these:

  • Enough upload and download bandwidth for your peak call volume
  • Latency, jitter, and packet loss tested during busy hours
  • QoS configured on your firewall and switches
  • Phones on a separate voice VLAN
  • SIP ALG reviewed and disabled if your provider recommends it
  • PoE switches or power adapters for every desk phone
  • UPS battery backup on core network gear
  • A backup internet connection or failover plan
  • Emergency addresses registered for every phone
  • A plan to port your existing phone numbers

How One Solutions Can Help

One Solutions installs SIP-based VoIP phone systems with 24/7 voicemail, call forwarding, and mobile integration, designed so calls keep flowing during outages. Our installation team uses pre-configured equipment and weekend deployment so the switch doesn't interrupt your workday.

If you'd like a second opinion on whether your network is ready, call us at (703) 263-8500 or contact us.