Barracuda Phone System deployment requires a network connection. The performance of your phone system and the ease or complexity of setup depends, in part, on the network configuration you choose. The Barracuda Phone System relies on the attached network to provide bandwidth, the amount of data flow available for voice connections, and to provide correct configuration information. While connecting your Barracuda Phone System to an existing network may require less physical network configuration, it introduces some performance and complexity issues to your phone system deployment. You should consider these issues before deciding which network configuration you will implement.
Voice connections rely on adequate network bandwidth. By attaching your Barracuda Phone System and phones to an existing network, the bandwidth available for voice connection traffic will be constrained to the existing network bandwidth available. Lack of bandwidth could negatively impact voice connection quality and reliability. Also, attaching the Barracuda Phone System and phones to the existing network may impact other network elements vying for the same bandwidth.
Any network device with its own IP address (phones and SIP devices in your system) receives configuration information from the DHCP server when connected to the network. Because phones need configuration to point to the Barracuda Phone System as the phone server, the network must be configured to allow the DHCP server to correctly distinguish which network elements are phones and SIP devices so correct configuration information can be transmitted to them. Implementing a virtual LAN (VLAN) comprised of only phone system elements is one way to ensure that phones are correctly identified, and receive correct configuration information from the DHCP server when attached to an existing network.
Other VLAN Considerations
The Barracuda Phone System can be configured to work in layer 2 segmented VLANs by simply configuring the connected switch port as an access port in the Voice VLAN. This allows broadcast messages to flow to and from the connected phones. UI access to the Barracuda Phone System can then be configured by either:
- Adding a route from the data VLAN to the Barracuda Phone System in the voice VLAN or,
Configuring the Barracuda Phone System WAN port to connect to the Data VLAN.
Endpoint makes and models vary in the level of support for VLANs and likely in the available VLAN features. Most supported phone vendors support VLAN discovery via the Link Layer Discovery Protocol with the Media Endpoint Discovery extension (LLDP-MED) which is recommended; some phone vendors support the proprietary Cisco Discovery Protocol (CDP). If you utilize segmented voice/data VLANs, Barracuda Networks recommends configuring them on each phone according to the manufacturer's guidelines, or using the phones in access mode and configuring VLANs at the switches/routers themselves.
Supported Polycom endpoints also support an alternative method for VLAN discovery. It requires:
- At least two VLANs, one voice VLAN (e.g. VLAN ID 10) and one untagged VLAN (e.g. VLAN ID 1).
- Setting Option 128 on the untagged VLAN's DHCP server. This tells the Polycom to start tagging voice traffic. Please see http://community.polycom.com/t5/VoIP/FAQ-Utilizing-VLAN-s-with-Polycom-phones/td-p/38100 for more details.
Dedicated Physical Network
Considering these quality and complexity issues, the ideal network setup for the Barracuda Phone System and the phones it serves (SIP devices, IP phones) is a dedicated physical network. Using this configuration results in high quality voice transmission with the fewest dropped calls. This setup enables phones to get the proper configuration information without introducing added complexity into the existing network.