NBN VoIP Compatibility for Australian Businesses

NBN Technology Types and VoIP: The Summary

FTTP: The Best NBN Connection for VoIP

FTTP (Fibre to the Premises) delivers optical fibre directly to your building. FTTP removes copper from the access link and is generally NBN's most reliable fixed-line technology, but end-to-end latency and jitter can still vary with the provider network, destination, equipment and congestion; a universal 2-5ms figure should not be assumed. For a business that relies heavily on VoIP and cannot tolerate call quality variation, FTTP is the preferred connection type.

If FTTP is available at your address but the building is not yet connected (common in new developments or recently upgraded areas), contact your NBN retailer. FTTP upgrade programs have expanded significantly since 2022 and many formerly FTTN premises can now access FTTP connections. For a comparison of current options, see our guide to the best VOIP-compatible phone systems for Australian businesses.

FTTN connections (fibre to a street cabinet, then copper wire to your premises) are the most common source of VOIP call quality problems in Australia. If your NBN is FTTN and your copper run is long or in poor condition, call quality will be inconsistent regardless of your plan speed. The permanent access-network remedy, where eligible, is an FTTP upgrade ordered through a participating NBN provider; a separate 4G or 5G service may provide backup connectivity.

A lot of businesses assume poor VOIP call quality means their internet plan is too slow. Speed is rarely the issue. A voice call uses only about 100Kbps of bandwidth. The actual causes are latency (the delay between sending and receiving packets), jitter (inconsistency in that delay), and packet loss. An FTTN connection with 50Mbps download but high jitter will have worse phone call performance than an FTTC connection with 25Mbps but low jitter.

FTTC: Excellent Performance, Close to FTTP

FTTC (Fibre to the Curb) is one of the newer NBN deployments across Australia. Fibre runs to a distribution point (DP) unit in a pit directly outside or near your premises, typically within 10 to 30 metres. A short VDSL2 copper run bridges the final distance from the DP to your building's existing copper socket.

Because the copper component is extremely short, FTTC performance is substantially better than FTTN and approaches FTTP in practice. Latency is typically 3-8ms and jitter is low. Businesses on FTTC can run multiple simultaneous VoIP calls without concern about the connection technology itself. The limiting factors shift to router configuration, SIP ALG handling, and internal network setup, not the NBN connection.

FTTB: Common in Multi-Tenancy Commercial Buildings

FTTB (Fibre to the Building) is a common NBN technology for businesses in multi-tenancy office buildings, commercial towers, and mixed-use developments. Fibre runs to the building's main distribution frame (MDF), typically in the basement communications room, and from there the existing internal building copper serves each tenancy.

Internal copper runs in commercial buildings are typically under 100 metres and are in better condition than the street copper used by FTTN. FTTB latency is generally 5-10ms and is reliable for VoIP. The main risk factor is aging internal building copper in older commercial properties. If your business is in an older building and experiencing VoIP quality issues, check with the building manager whether the internal copper has been tested. Old or poorly jointed internal copper can produce the same symptoms as FTTN, variable latency and occasional packet loss, even though the external connection is fibre-based.

HFC: Generally Reliable With One Caveat

HFC (Hybrid Fibre Coaxial) uses the old Foxtel cable TV infrastructure, coaxial cable, for the final connection to your premises. HFC is generally reliable for business VoIP. Latency is typically 5-15ms, which is well within acceptable range for voice.

The caveat is that the coaxial network is shared between nearby premises. In residential-dense areas, peak-hour congestion can occasionally affect latency. Late-day degradation may be caused by congestion, but testing is needed to distinguish the HFC access segment from retailer-network, local-network, Wi-Fi and router issues. Some business products offer specific traffic-class or service-assurance features, but these must be confirmed in the provider's plan; a generic business-plan label does not establish dedicated or prioritised capacity.

FTTN: The Most Problematic NBN Type for VoIP

FTTN (Fibre to the Node) is the NBN technology that causes the most VoIP problems for Australian businesses. The fibre component runs to a street cabinet (node), and from there a copper telephone line runs to your premises. The length and condition of that copper run determines your line's latency and stability.

Longer or degraded FTTN copper can reduce performance and stability, but there is no universal 300m or 600m VoIP threshold; the individual line must be tested. Deteriorated copper, aged joints, water-damaged pits, and corroded connections can cause significant quality issues regardless of distance. If your business is on FTTN and experiencing VoIP problems, request a line quality check from your NBN retailer and ask specifically about latency and jitter, not just download speed.

Fixed Wireless: Workable for Small Deployments

Fixed Wireless NBN is deployed in regional and rural areas where fibre is not economically viable. The connection uses radio signals from a nearby tower to an antenna mounted on your roof. Latency is typically 30-60ms, higher than any fibre-based NBN type but generally workable for VoIP.

Fixed Wireless can support VoIP, but simultaneous-call capacity should be determined from measured upload bandwidth, latency, jitter and packet loss under representative load rather than a fixed call-count threshold. Variability comes from weather interference, tower congestion, and distance to the tower. Test under real load conditions before committing to a full multi-line deployment.

Satellite Internet and VoIP: Sky Muster vs Starlink

There are two satellite internet options available in rural Australia, and they have completely different implications for VoIP. Most VoIP guidance about satellite refers to the older Sky Muster system, but Starlink has changed the picture significantly for rural businesses.

Sky Muster: Not Compatible With Real-Time VoIP

Sky Muster is NBN Co's geostationary satellite service for very remote areas. Geostationary satellites orbit approximately 35,000km above the earth. The signal must travel up to the satellite and back twice for every packet, adding a minimum round-trip latency of 600 milliseconds. A commonly used design target is less than 150ms one-way end-to-end delay; higher delay progressively affects conversational quality but is not by itself a universal SIP compatibility test. Sky Muster's geostationary-satellite latency can noticeably impair interactive conversation, but VoIP services are available over Sky Muster; businesses should confirm suitability and expected call quality with the provider.

Businesses on Sky Muster who need telephone service should use a mobile-based solution, a hosted business number that rings through to a mobile app, rather than attempting to deploy SIP desk phones.

Starlink: VoIP-Capable With Caveats

Starlink (SpaceX) uses low-earth-orbit satellites at approximately 550km altitude. Because the satellites are far closer to earth than geostationary systems, Starlink latency is typically 20-60ms, well within VoIP-compatible range. Many Australian rural businesses now run VoIP successfully over Starlink.

Two caveats to be aware of: Standard Starlink service commonly uses CGNAT, while Australian Local Priority and Global Priority business plans allow a public-IP policy; confirm the selected plan's IP addressing before deployment. Most current Australian cloud phone system companies handle CGNAT correctly, but confirm with your provider before deploying. Second, Starlink occasionally experiences brief dropouts during satellite handoffs (when your terminal switches between overhead satellites). Starlink itself describes these as brief, but does not publish a specific duration guarantee, treat a dropout as a normal characteristic of satellite handoff rather than assuming it is always sub-second or harmless for every VoIP use cases, but are worth knowing about for high-volume environments.

How Many Simultaneous Calls Can Your NBN Support?

Each simultaneous VoIP call uses approximately 80-100 kbps of bandwidth (G.711 codec, the standard for Australian VoIP deployments). NBN25 services may provide 5Mbps or 10Mbps upload depending on the product and technology. At 100kbps per call, that is raw theoretical capacity for about 50 or 100 calls respectively, before allowing for other traffic and engineering headroom.

Bandwidth is almost never the bottleneck for VoIP on NBN. Latency, jitter and packet loss depend on the access technology, provider network, destination, local equipment and congestion. Plan speed matters when available upload or download capacity becomes saturated. Upgrading from NBN25 to NBN100 will not fix VoIP problems caused by FTTN copper degradation. FTTP generally offers a more reliable access link than FTTN, but voice quality still depends on the complete network path and cannot be guaranteed from access technology alone.

Choose a speed tier that provides sufficient upload capacity and headroom for calls plus other business traffic; the former higher-tier CVC-allocation rationale no longer applies to non-satellite services from 1 July 2026. Some business plans include enhanced restoration targets or other service-assurance features, but inclusions vary by provider, product, technology and area; confirm the actual SLA rather than relying on the business-plan label or staff count.

SIP ALG: The Number One Cause of NBN VoIP Failures in Australia

SIP ALG can disrupt registration, signalling or audio on some routers and hosted-phone services, so check the phone provider's and router manufacturer's configuration guidance.

SIP ALG (Session Initiation Protocol Application Layer Gateway) is a feature built into most consumer and SMB routers. It was designed to help SIP traffic pass through NAT more reliably. In practice, most SIP ALG implementations incorrectly modify SIP packet headers as they pass through the router. The result is corrupted SIP signalling that causes phones to fail to register, produces one-way audio (one party can hear the other but not vice versa), drops calls after 30-60 seconds, or prevents inbound calls from ringing at all.

To disable SIP ALG: log into your router's admin interface (typically 192.168.0.1 or 192.168.1.1 in a browser). Look under Advanced Settings, NAT, ALG, or Firewall. The setting may be labelled 'SIP ALG', 'SIP Passthrough', 'SIP Transformations', or 'VoIP ALG'. Disable it, save, and restart the router. For step-by-step instructions by Australian router brand, see our guide to QoS and SIP settings on Australian routers.

Other Steps to Optimise VoIP on Any NBN Connection

Enable QoS for Voice Traffic

QoS (Quality of Service) tells your router to prioritise VoIP packets over other internet traffic. This prevents video streaming, large file downloads, or background updates from degrading call quality during busy periods. Use the signalling transports, ports and RTP ranges specified by your phone provider. SIP commonly uses 5060 over UDP or TCP and 5061 for TLS, while RTP ranges vary. DSCP EF marking helps only where switches and routers are configured to honour it with appropriate queueing.

Use Wired Ethernet for IP Phones

Every IP desk phone should be connected via wired Ethernet, not Wi-Fi. Wi-Fi introduces variable latency and occasional packet loss as devices compete for airtime. On a wired connection, each device has a dedicated full-duplex channel to the switch. For reception desks, primary business lines, or any phone where reliability matters, Wi-Fi is not appropriate. For hot-desk phones where cabling is impractical, Wi-Fi is a compromise, acceptable for occasional use, not for a primary business line.

Consider a Business-Grade Router

Modem-routers bundled by NBN retailers are generally built for residential internet rather than multi-phone business VoIP, capability varies by model and firmware. If you are deploying multiple IP phones, a dedicated business router generally provides more reliable SIP handling, proper QoS, and better NAT traversal. The Draytek Vigor series is widely used in Australian VoIP deployments for its well-regarded SIP support. Ubiquiti EdgeRouter and MikroTik are popular among technically capable businesses. Budget $300-600 for a purpose-built business router, it is often the highest-value single hardware change for VoIP reliability.

Use G.711 Codec, Not G.729

G.729 encodes voice at 8kbps, but a call commonly consumes about 31kbps over Ethernet after packet and network overhead, compared with about 87kbps for G.711 under common packetisation assumptions. It is sometimes configured by providers or resellers as a bandwidth-saving measure. On any NBN connection above the minimum tier, this is an unnecessary trade-off, bandwidth is not the VoIP constraint on NBN, and G.729 compression introduces audio artefacts and slightly higher processing latency. Use G.711 (PCMU or PCMA) for the best quality on any NBN connection above NBN12.

The PSTN Copper Shutdown

Australia's PSTN copper telephone network has been progressively decommissioned as NBN rollout has completed. Most affected legacy copper voice services in NBN fixed-line areas have been migrated or disconnected, but Fixed Wireless and Sky Muster premises may retain copper services, and some business and Special Services have separate arrangements. If your business has not yet moved to a proper VoIP service and is still on an ISP-supplied ATA (the green phone port on your NBN modem), see our ATA adapter guide and VoIP vs traditional phone comparison to understand your migration path.

If you have purchased a new IP desk phone and want to understand what to do next, our new IP phone setup guide covers business phone company selection, SIP credential entry, Ethernet connection, and getting the phone registered for the first time.

Does NBN Type Affect Phone System Cost?

Cloud phone pricing varies by provider, inclusions, licensing model, call usage and contract; the NBN access technology generally does not determine the licence price. What changes by NBN type is call quality and whether you need a QoS-capable router to prioritise voice traffic. A QoS router costs $100-300 as a one-off if your current router does not support it. QoS may help on any access technology when voice competes with other traffic at a congested or rate-limited interface; the need should be based on measured traffic and router behaviour, not FTTP, HFC, FTTC or FTTN alone.

Once you have confirmed your NBN connection type is compatible with cloud phone calls, the next step is configuration. Our guide to setting up business phones on the NBN covers the full setup process including NBN-specific QoS settings, router requirements for each technology type, and the most common issues by connection type.

NBN connection type is one of the biggest factors in whether VoIP will work reliably for your business. If you have an NBN connection type known for reliability problems, or if your business has very specific uptime requirements, our guide to when VoIP is not the right choice for your business covers the scenarios where you need additional planning before committing to a full VoIP setup.

How do I find out which NBN technology type is at my address?

Use the address checker at nbnco.com.au. Enter your business address and the result will show your current NBN technology type and any upgrade plans. Your NBN retailer's account portal also typically shows your connection technology. Ask specifically for the technology type, FTTP, FTTC, FTTB, FTTN, HFC, or Fixed Wireless, not just your speed tier.

Can I upgrade from FTTN to FTTP for better VoIP quality?

NBN Co has several FTTP upgrade pathways. Eligibility is address-specific and upgrades are ordered through a participating provider; FTTN Fibre Connect upgrades generally require an eligible plan, while selected underperforming lines may follow a different process. Ask the provider about plan and non-standard installation costs. Check nbnco.com.au for current availability at your address.

My NBN speed test results are good but VoIP quality is poor. Why?

Speed tests measure download and upload throughput, not latency or jitter, which are what VoIP depends on. Before investigating anything else, disable SIP ALG on your router. It is the most common cause of this symptom on any NBN connection type. If that does not resolve the issue, run a ping test to measure round-trip latency and jitter. Jitter above about 30ms can impair voice, but latency must be interpreted using the measurement type and provider guidance; an 80ms ping round-trip time alone does not establish noticeable degradation.

Does my NBN plan speed affect VoIP quality?

Rarely. Each VoIP call uses approximately 80-100 kbps. Even an NBN25 plan has more than enough bandwidth for multiple simultaneous calls. Upgrading to NBN100 will not improve call quality unless your connection was genuinely bandwidth-saturated. Connection technology type and router configuration matter far more than plan speed.

Does Starlink support VoIP for Australian businesses?

Yes, with caveats. Starlink's LEO network delivers 20-60ms latency, which is sufficient for SIP-based VoIP. Most Australian small businesses running 1-5 simultaneous calls over Starlink report acceptable quality. The main consideration is CGNAT, Starlink does not provide a dedicated public IP address. Most current Australian cloud phone system companies handle this correctly, but confirm before deploying. Do not confuse Starlink with Sky Muster (NBN Co's geostationary satellite): Sky Muster has 600ms+ latency and is not compatible with real-time VoIP.

What is SIP ALG and why does it break VoIP?

SIP ALG (Application Layer Gateway) is a router feature that attempts to modify SIP traffic passing through NAT. Most implementations do this incorrectly, corrupting SIP headers in ways that prevent phones from registering, cause one-way audio, or drop calls after 30-60 seconds. It is enabled by default on almost all Australian NBN routers. Disabling it is the first step recommended by every major Australian business phone company. Find it under Advanced, NAT, ALG, or Firewall settings in your router's admin interface.

What router should I use for VoIP on NBN?

The consumer modem-router supplied by your NBN retailer is sufficient for basic setups once SIP ALG is disabled. For businesses with 3+ IP phones, a dedicated business router improves reliability significantly. The Draytek Vigor series is widely used in Australian VoIP deployments and has well-regarded SIP handling. Ubiquiti EdgeRouter and MikroTik are popular options for technically capable users. Budget $300-600 for a purpose-built business router, it is often the highest-value single hardware change for VoIP stability.

My new IP phone shows 'Not Registered', is this an NBN problem?

Usually not. 'Not Registered' typically means the phone has no SIP credentials configured, or that SIP ALG on the router is blocking registration. First, confirm you have a business phone company account and have entered SIP credentials into the phone. If credentials are correct but the phone still will not register, disable SIP ALG on your router. Our new IP phone setup guide covers the full process and troubleshooting checklist.

Not sure which VoIP setup suits your NBN connection type?

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