Nebula [Wireless] - Configure VoIP for Best Practice [VoWiFi]

Voice over IP (VoIP) is a critical communication tool for businesses and individuals alike. To ensure the best VoIP experience over a wireless network, it's essential to configure your WiFi network properly. This guide provides comprehensive guidelines for configuring VoIP on Zyxel devices, ensuring VoIP integrity, and enhancing overall performance.

 

Section 1: VoIP Considerations

1.1 Understanding VoIP Characteristics:

• VoIP requires real-time transmission/conversation.
• Voice packets lack integrity checks.
• Latency significantly impacts conversation quality.

1.2 Goals:

• Provide guidelines for optimizing VoIP performance.
• Improve VoIP integrity.
• Identify complementary features.
• Highlight features to avoid.
• Extend guide to Nebula Switch configuration.

Section 2: WiFi Setup for VoIP

2.1 Configure a Dedicated SSID and VLAN for VoIP:

• Create a separate SSID and VLAN exclusively for VoIP traffic.

Navigate to: 

Site-wide > Configure > Firewall > Interfaces

Then add the VLAN interface for the VoIP traffic.

Then create the SSID by navigating to: 

Site-wide > 

 

2.2 Limit the Number of SSIDs:

• Maintain fewer than 3 SSIDs to minimize wireless traffic overhead.

2.3 Select the 5GHz band & Enable U-APSD:

Navigate to: 

Site-wide > Configure > Access Points > SSID Advanced Settings

• Avoid the congested 2.4GHz band.
• Disable band selection to prevent unwanted band switches by IP phones.
• Ensure that features like L2 isolation and guest networks are disabled to facilitate VoIP communication.
• Activate U-APSD (Unscheduled Automatic Power Save Delivery) only on the SSID dedicated to IP phones.
• U-APSD prevents phones from entering sleep mode during active calls.
• If smartphones are used for VoIP, we recommend to leave 802.11k/v & 802.11r disabled
• Enable 802.11k/v for IP phones frequently on the move.
• Enable 802.11r if phones require WPA2-PSK or WPA2-Enterprise for faster roaming.
• Remember that some phones does not support 802.11k/v and 802.11r which could cause issues in your network.

2.4 Implement Rate Limiting:

Navigate to:

Site-wide > Configure > Access Points > SSID Advanced Settings

• Enable rate limiting on SSIDs not dedicated to VoIP.
• Assign unlimited upload/download speeds for VoIP.
• Allocate 5 Mbps upload/download for office services.
• Limit guest services to 1 Mbps upload/download.

For Office WiFi:

5 mbit/s Download + 5 mbit/s Upload

 

For Guest WiFi:

1 mbit/s Download + 1 mbit/s Upload

2.6 Optimize Wireless Radios:

• If you need 2.4GHz radio for WiFi, please set the max output power of the 5GHz radio 6~8 dB higher than the 2.4GHz radio.

Navigate to: 

Site-wide > Configure > Access Points > Radio Settings

• Schedule Dynamic Channel Selection (DCS) outside of office hours.

2.7 Enable Smart Steering:

• Activate Smart Steering and configure the following thresholds:
  • Station Signal Threshold: -76 dBm
  • Disassociate Station Threshold: -80 dBm
  • Station Retry Count: 2

2.8 Survey Client Signal:

• Aim for an ideal signal strength of IP phones better than -67 dBm.
• Re-evaluate AP deployment if stationary IP phones show worse than -67 dBm.

 

Section 3: VoIP Configuration on Nebula Switch

3.1 Set Quality of Service (802.1p) for VoIP Traffic:

Navigate to: 

Site-wide > Configure > Switches > Switch Settings

• Configure 802.1p for VoIP traffic on Nebula switch.

• Then configure Voice VLAN with the OUI of the IP phones

For example, if you have an IP phone from Company A with MAC address 00:0a:95:9d:68:16, you can enter OUI 00:0a:95 to match all devices from Company A.

 

3.2 Switch Port Configuration

• Specify settings for Access Ports (connected to IP phones/PC) and Trunk Ports (connected to AP/gateway).

Section 4: Application Layer Gateway (ALG) for VoIP

4.1 Understanding ALG for VoIP Phones:

• An Application Layer Gateway (ALG) is a critical component in facilitating VoIP communication over a network.
• ALG helps VoIP phones establish and maintain connections by dynamically translating network addresses and ports.
• ALG is essential for handling the signaling and media streams used in VoIP protocols, such as SIP (Session Initiation Protocol) and RTP (Real-time Transport Protocol).

4.2 Configuring ALG in Your PBX:

• Access your PBX (Private Branch Exchange) configuration settings.
• Locate the ALG or SIP ALG option in your PBX settings.
• Enable the ALG feature to ensure that your PBX can intelligently manage VoIP traffic.
• Configure ALG settings as necessary, including specifying the protocols to monitor (e.g., SIP and RTP).

4.3 Caution: Setting UDP Session Timeout:

• While configuring your network for VoIP, be cautious about the UDP Session Timeout setting.
• Setting a UDP Session Timeout that is too high (e.g., 300 seconds) can lead to an excessive number of active sessions in your network.
• Too low UDP Session Timeout setting can cause disconnections and other issues
• Recommended UDP Session Timeout is 60 seconds
  
• High session counts can strain network resources and potentially impact VoIP performance.

4.4 Rebooting IP Phones:

• After enabling ALG and making any relevant network configuration changes, it is recommended to reboot your IP phones.
• Rebooting ensures that the phones establish new connections and apply the ALG settings correctly.

 

After successful VoIP configuration, please reboot your phones.

 

Note: PDF can be found attached at the bottom of this article.