VoIP Network Requirements and Best Practices

A properly configured network is the foundation of reliable VoIP service. This comprehensive guide covers all network requirements, bandwidth calculations, and best practices to ensure optimal voice quality and system performance.

Network Fundamentals for VoIP

Understanding VoIP Traffic

VoIP systems generate two types of network traffic:

1. SIP Signaling Traffic

   • Call setup, teardown, and control messages
   • Small packets, low bandwidth requirement
   • Uses UDP/TCP port 5060
   • Requires reliable delivery

2. RTP Media Traffic

   • Actual voice data packets
   • Larger packets, higher bandwidth requirement
   • Uses dynamic UDP ports (10000-20000)
   • Requires real-time delivery

Network Quality Metrics

Latency (Delay):

• Optimal: < 50ms one-way
• Acceptable: 50-150ms one-way
• Poor: > 150ms one-way

Jitter (Variation in Delay):

• Optimal: < 10ms
• Acceptable: 10-30ms
• Poor: > 30ms

Packet Loss:

• Optimal: 0%
• Acceptable: < 1%
• Poor: > 1%

Bandwidth Requirements

Per-Call Bandwidth Calculations

G.711 Codec (PCMU/PCMA):

Bandwidth per call: 64 Kbps
Header overhead: 16 Kbps
Total per call: 80 Kbps
Recommended: 100 Kbps per call

G.722 Codec (HD Voice):

Bandwidth per call: 64 Kbps
Header overhead: 16 Kbps
Total per call: 80 Kbps
Recommended: 100 Kbps per call

G.729 Codec (Compressed):

Bandwidth per call: 8 Kbps
Header overhead: 16 Kbps
Total per call: 24 Kbps
Recommended: 30 Kbps per call

G.722.2 Codec (Wideband):

Bandwidth per call: 12.65 Kbps
Header overhead: 16 Kbps
Total per call: 28.65 Kbps
Recommended: 35 Kbps per call

Total Bandwidth Requirements

Formula:

Total Bandwidth = (Bandwidth per call × Number of concurrent calls) + Overhead

Examples:

Small Office (5 extensions, 2 concurrent calls):

G.711: 2 calls × 100 Kbps = 200 Kbps
Overhead: 50 Kbps
Total: 250 Kbps minimum
Recommended: 1 Mbps

Medium Office (20 extensions, 8 concurrent calls):

G.711: 8 calls × 100 Kbps = 800 Kbps
Overhead: 200 Kbps
Total: 1 Mbps minimum
Recommended: 5 Mbps

Large Office (50 extensions, 20 concurrent calls):

G.711: 20 calls × 100 Kbps = 2 Mbps
Overhead: 500 Kbps
Total: 2.5 Mbps minimum
Recommended: 10 Mbps

Network Infrastructure Requirements

Internet Connection

Connection Types:

Dedicated Fiber:

• Pros: High bandwidth, low latency, symmetrical
• Cons: Expensive, limited availability
• Best for: Large businesses, call centers

Cable Internet:

• Pros: High download speeds, widely available
• Cons: Asymmetrical, shared bandwidth
• Best for: Small to medium businesses

DSL:

• Pros: Dedicated line, stable
• Cons: Limited bandwidth, distance dependent
• Best for: Small offices, remote locations

Wireless (4G/5G):

• Pros: Quick deployment, mobile
• Cons: Variable latency, data caps
• Best for: Temporary setups, backup connections

Network Equipment

Router Requirements:

• CPU: Multi-core processor
• RAM: 512MB minimum, 1GB recommended
• Features: QoS, VLAN support, SIP ALG disable
• Brands: Cisco, Ubiquiti, MikroTik, Netgear Pro

Switch Requirements:

• PoE: Power over Ethernet support
• QoS: Quality of Service capabilities
• VLAN: Virtual LAN support
• Bandwidth: Gigabit ports recommended

Firewall Requirements:

• Throughput: Handle expected bandwidth
• VoIP Support: SIP/RTP protocol support
• QoS: Traffic prioritization
• Security: Intrusion prevention

Quality of Service (QoS) Configuration

QoS Priority Levels

Priority 1 (Highest): VoIP RTP traffic Priority 2 (High): VoIP SIP signaling Priority 3 (Medium): Web browsing, email Priority 4 (Low): File downloads, streaming

QoS Implementation

Router-Based QoS:

Cisco Configuration:

class-map match-all VOIP-RTP
 match dscp ef
 match dscp cs4
!
class-map match-all VOIP-SIP
 match dscp cs3
 match access-group name SIP
!
policy-map VOIP-POLICY
 class VOIP-RTP
  priority percent 20
 class VOIP-SIP
  bandwidth percent 5
 class class-default
  fair-queue
!
interface FastEthernet0/0
 service-policy output VOIP-POLICY

Ubiquiti Configuration:

1. Go to Settings → Traffic Management
2. Enable Smart Queues
3. Set upload/download speeds
4. VoIP traffic automatically prioritized

MikroTik Configuration:

/queue simple add name=voip-rtp target=192.168.1.0/24 max-limit=1M/1M priority=1
/queue simple add name=voip-sip target=192.168.1.0/24 max-limit=100K/100K priority=2
/queue simple add name=other target=192.168.1.0/24 max-limit=10M/10M priority=8

DSCP Marking

DSCP Values for VoIP:

VoIP RTP: EF (Expedited Forwarding) - 46
VoIP SIP: CS3 (Class Selector 3) - 24
Video: CS4 (Class Selector 4) - 32
Data: CS0 (Class Selector 0) - 0

VLAN Configuration

Voice VLAN Benefits

1. Traffic Isolation: Separate voice from data traffic
2. QoS Control: Easier traffic prioritization
3. Security: Enhanced network security
4. Management: Simplified network administration

VLAN Setup

VLAN Configuration Example:

VLAN 10: Voice (VoIP devices)
VLAN 20: Data (computers, servers)
VLAN 30: Management (network devices)
VLAN 40: Guest (visitor access)

Switch Configuration:

vlan 10
 name VOICE
!
interface FastEthernet0/1
 switchport mode access
 switchport access vlan 10
 switchport voice vlan 10
 spanning-tree portfast
 spanning-tree bpduguard enable
!
interface Vlan10
 ip address 192.168.10.1 255.255.255.0

Network Security

Firewall Configuration

Required Ports:

SIP Signaling: UDP/TCP 5060
RTP Media: UDP 10000-20000
HTTPS Provisioning: TCP 443
NTP: UDP 123

Firewall Rules:

# Allow SIP traffic
permit udp any any eq 5060
permit tcp any any eq 5060

# Allow RTP traffic
permit udp any any range 10000 20000

# Allow provisioning
permit tcp any any eq 443

# Allow NTP
permit udp any any eq 123

Security Best Practices

1. Network Segmentation:

   • Separate voice and data networks
   • Use VLANs for traffic isolation
   • Implement access control lists

2. Access Control:

   • Change default passwords
   • Use strong authentication
   • Limit administrative access

3. Monitoring:

   • Enable security logging
   • Monitor for suspicious activity
   • Regular security audits

Network Testing and Monitoring

Performance Testing

Speed Tests:

• Speedtest.net: Basic bandwidth testing
• Fast.com: Netflix speed test
• Ookla Speedtest CLI: Command-line testing

Latency Tests:

# Ping test
ping -c 100 your-sip-server.com

# Traceroute
traceroute your-sip-server.com

# MTR (My TraceRoute)
mtr your-sip-server.com

Packet Loss Tests:

# Extended ping test
ping -c 1000 -i 0.1 your-sip-server.com

# Using pingplotter
pingplotter your-sip-server.com

Monitoring Tools

Free Tools:

• Wireshark: Packet analysis
• SIPp: SIP traffic testing
• Nagios: Network monitoring
• PRTG: Traffic analysis

Commercial Solutions:

• SolarWinds: Network monitoring
• ManageEngine: VoIP monitoring
• Paessler: PRTG Network Monitor

Troubleshooting Network Issues

Common Network Problems

High Latency:

• Causes: Network congestion, routing issues
• Solutions: Implement QoS, optimize routing

Packet Loss:

• Causes: Network congestion, hardware issues
• Solutions: Check network equipment, upgrade bandwidth

Jitter:

• Causes: Network congestion, buffer issues
• Solutions: Implement QoS, optimize buffers

Diagnostic Commands

Network Connectivity:

# Test basic connectivity
ping your-sip-server.com

# Test specific ports
telnet your-sip-server.com 5060
nc -u your-sip-server.com 5060

# Check routing
traceroute your-sip-server.com

Bandwidth Testing:

# Test upload/download speeds
speedtest-cli

# Test with specific server
speedtest-cli --server 1234

Network Optimization

Bandwidth Optimization

1. Codec Selection:

   • Use G.729 for bandwidth-constrained networks
   • Use G.711 for high-quality networks
   • Consider G.722 for HD voice

2. Traffic Shaping:

   • Implement bandwidth limits
   • Prioritize VoIP traffic
   • Limit non-essential traffic

3. Compression:

   • Enable RTP header compression
   • Use compressed codecs when appropriate
   • Optimize packet sizes

Network Redundancy

Primary Connection:

• High-speed internet connection
• QoS-enabled router
• Proper firewall configuration

Backup Connection:

• Secondary internet connection
• Automatic failover
• Different ISP for redundancy

Load Balancing:

• Distribute traffic across connections
• Failover configuration
• Traffic monitoring

Best Practices Summary

Network Design

1. Plan for Growth:

   • Estimate future bandwidth needs
   • Design scalable network architecture
   • Consider redundancy requirements

2. Implement QoS:

   • Prioritize VoIP traffic
   • Configure bandwidth limits
   • Monitor traffic patterns

3. Security First:

   • Segment voice and data networks
   • Implement access controls
   • Regular security updates

Maintenance

1. Regular Monitoring:

   • Monitor network performance
   • Check for bandwidth issues
   • Review security logs

2. Proactive Maintenance:

   • Update network equipment
   • Optimize configurations
   • Test failover systems

3. Documentation:

   • Document network topology
   • Record configuration changes
   • Maintain troubleshooting guides

Conclusion

A properly configured network is essential for reliable VoIP service. By following these guidelines, you can ensure optimal voice quality and system performance.

Key Success Factors:

1. Adequate bandwidth planning
2. Proper QoS implementation
3. Network security configuration
4. Regular monitoring and maintenance
5. Proactive troubleshooting

Need Help? Contact ATCVoIP support for assistance with:

• Network design and planning
• QoS configuration
• Security implementation
• Performance optimization
• Troubleshooting assistance

Remember: A well-designed network is the foundation of successful VoIP deployment.