What Is VoIP?
VoIP (Voice over Internet Protocol) is a technology that carries voice calls over the internet instead of traditional phone lines (PSTN). Voice data is converted into packets and transmitted via the internet. In Japan, 050-number IP phone services are the most common example, and services like NTT's Hikari Denwa that use traditional area-coded numbers are also widespread. If you are considering switching from a landline to Hikari Denwa, see Hikari Denwa Migration Guide.
Understanding VoIP is important for anyone looking to reduce communication costs or improve business efficiency. VoIP is used across a wide range of scenarios from personal to business use. Recommended IP phones are worth comparing when considering adoption.
How VoIP Works
Digitization and Packetization of Voice
Voice captured by a microphone is converted to digital data, split into small packets, and transmitted over the internet. The receiving end reassembles the packets and plays them back as audio. This entire process happens in real time, providing a conversation experience similar to a regular phone call.
Voice compression uses codecs. G.711 offers high quality but consumes more bandwidth, while G.729 saves bandwidth at the cost of slightly lower quality. The appropriate codec is automatically selected based on the network environment.
Key Protocols
VoIP uses SIP (Session Initiation Protocol) to manage call setup and teardown, and RTP (Real-time Transport Protocol) to carry the actual voice data. These protocols work together to deliver stable calls. SIP is a text-based protocol similar to HTTP, offering high extensibility.
Advantages of VoIP
- Significant cost savings: Cheaper than landlines, especially for long-distance and international calls where savings of 50%-90% are possible
- Location flexibility: Make and receive calls from the same number anywhere with an internet connection. Ideal for remote work
- Rich add-on features: Call forwarding, recording, IVR (interactive voice response), and call analytics can be added via software
- Multi-device support: Use simultaneously on smartphones, PCs, and dedicated handsets
- Scalability: Easy to add or reduce lines as the business grows
Disadvantages and Considerations
- Quality depends on the network: Call quality is directly tied to internet speed and stability. Jitter and packet loss cause audio degradation
- Unusable during power outages: Requires power for internet equipment. A UPS (uninterruptible power supply) can mitigate this
- Emergency call limitations: Many 050-number IP phone services do not support emergency calls to 110/119
- Social credibility of 050 numbers: 050 numbers may be perceived as less credible than landline numbers. For business use, consider services supporting 0AB-J numbers
- Security risks: Being internet-based, there are risks of eavesdropping and spoofing. Encryption (SRTP) is recommended
Comparing Major VoIP Services
In Japan, consumer services include NTT Communications' "050 plus," Rakuten Mobile's "Rakuten Link," and FUSION's "FUSION IP-Phone SMART." For businesses, carriers offer cloud PBX-integrated services, and global platforms like Zoom Phone, Microsoft Teams Phone, and Cisco Webex Calling have also entered the Japanese market.
When choosing a service, comprehensively compare call quality, pricing, supported numbers (050 or 0AB-J), emergency call support, and customer service. VoIP-compatible headsets are also worth checking.
VoIP Deployment Steps
Step 1: Check Your Network Environment
VoIP call quality depends directly on your internet connection. For stable calls, at least 1 Mbps up and down is recommended. For multiple simultaneous calls, allocate about 100 kbps per call. Ideally, jitter should be under 30 ms and packet loss under 1%.
Step 2: Select a Service
For personal use, a 050-number IP phone service is the easiest option. For business, choose a service supporting 0AB-J numbers (with area codes). Combining with a cloud PBX enables advanced features like extensions, forwarding, and IVR.
Step 3: Prepare Equipment
VoIP requires an IP phone handset, an ATA (Analog Telephone Adapter), or a softphone app (for PC/smartphone). If you want to keep using an existing analog phone, connect it through an ATA. Softphones require no additional hardware and pair well with remote work.
VoIP Security Measures
Since VoIP communicates over the internet, it faces security risks that traditional phone lines do not. Proper measures ensure safe VoIP usage.
- Call encryption: Use SRTP (Secure Real-time Transport Protocol) to encrypt voice data, significantly reducing eavesdropping risk
- Strengthen SIP authentication: Set complex passwords for SIP accounts and change them regularly to prevent brute-force attacks
- Firewall configuration: Allow only SIP traffic (ports 5060/5061) and RTP traffic (ports 10000-20000), closing unnecessary ports
- Use VPN: In remote work environments, route VoIP through a VPN to encrypt the entire communication path
When to Use VoIP vs. Traditional Landlines
VoIP and traditional landlines each have distinct strengths. Choosing based on your needs leads to the optimal communication setup.
- Cost priority: VoIP wins, especially for long-distance and international calls
- Reliability priority: Traditional landlines win. They work during power outages via exchange power and offer higher emergency call accuracy
- Flexibility priority: VoIP wins. Make and receive calls from anywhere on the same number, ideal for remote work
- Social credibility: VoIP with 0AB-J numbers is equivalent to landlines. 050 numbers may be seen as slightly less credible
Many businesses adopt a hybrid setup, using VoIP for regular calls while maintaining a landline as an emergency backup - a good balance of cost and reliability. Understand VoIP's pros and cons to choose the best service for your communication needs.