Best practice design for VoIP Network

[c_dutoit]

Hi,

I have multiple remote sites linked together with a 100/100 or 200/200Mb link. A ZD100 is on one of the site. I'm going to have to implement VoIP for mobile devices on several of these sites

I'm think I'll create a new WLAN only for the mobile phones on the already existing VoIP subnet. As there is only one IP subnet for VoIP on each site is the tunnel mode useful or should I use a "regular" WLAN ?

Regards,

[neelesh_verma]

If your phone systems are already empowered by VoIP phone system, my suggestion would be to use the subnet for your existing phone system used local PBX with ATA or hosted configuration PBX system to use the entire VoIP benefits such as Unified Communication. Services related to this can be affordably yours.  

[syamantakomer]

Hi,

Here are some of the recommended configurations to consider that are specific to ZD and APs -

1. Dedicated SSID for voice clients. Use a dedicated VLAN as well.
2. Tunnel traffic to ZD
3. Enable Call Admission Control (CAC)
4. DTIM value of 2 (this will ensure decent battery life without compromising call quality)
5. Enable OFDM-only
6. BSS minrate of 5.5 Mbps
7. Use particular channels only (e.g.: channels 1, 6, and 11 only)
8. Enable 802.11d
9. Increase background scan interval to a higher value - 5 or 10 minutes
10. See if ChannelFly is appropriate for your environment. If this doesn't suit, switch to background scanning and increase the scan interval to a higher value as mentioned above.
11. Disable mesh
12. Avoid any additional load on the APs
13. Enable RTS/CTS
14. Eliminate rogue APs and mobile hotspots

Please note that not all these settings may be appropriate for your deployment and VoIP handset you are using. Use only the ones that are recommended by your VoIP handset maker.
 
Here are some of the configuration settings to consider that are specific to a VoIP handset: 
1. Enable voice DSCP marking
2. Operate at max transmit power
3. Prefer 5 GHz frequency mode if available. This might require more number of APs. So site survey is the key.
4. Disable DHCP request on roam if there is a single VLAN for all voice clients
5. Control roaming if the device permits fine tuning

6. QoS preference. Some handset makers recommend using Continuously Awake Mode (CAM). Some may recommend legacy power save.

Note: Generally, use the VoWLAN manufacturer's design guide and compare to recommended settings above and accordingly configure the WLAN.