As the use of Voice over Internet Protocol (VoIP) continues to grow at a frantic pace, new users are often surprised at the frequency of problems. Without a user having more bandwidth than his needs could ever consume, users of Vonage, Skype, Google Voice, as well as users of business services like Hosted PBX, Virtual PBX and Hosted VoIP, will experience problems. Experienced and successful VoIP users have learned that with proper planning and care, VoIP really justifies its hype.
Prioritizing voicemail is one of many areas that require network administrator attention. Voice prioritization can be processed by the Differentiated Service Code Point (DSCP) field in network packets or by segmentation of the VoIP equipment into a separate VLAN. This article discusses how to configure a VLAN for successful VoIP transmission.
A VLAN has several advantages over using only the DSCP field, although it is somewhat more difficult to build. They can efficiently prioritize all critical VoIP traffic, including call signaling. They will also exclude packets generated on computers using accelerated forwarding (EF) in host mode (PHB) of the DSCP field, which can compete with the critical VoIP protocol. Additional benefits include reduced broadcast network traffic, as well as increased security, since other computers in other VLANs will not be able to control phone calls.
The network requires a managed Ethernet switch and an Internet router capable of manipulating the DSCP field in order to successfully implement a VLAN for voice prioritization. In addition, the endpoint of the computer and VoIP cannot transmit an IP address, which means there are no softphones. The computer can use a small Ethernet switch on the back of most IP phones and send one Ethernet cable back to the managed switch.
When configuring a VLAN, all computers and non-phone devices are programmed as members of the default VLAN. All VoIP phones must be members of a voice VLAN.
The router is on the verge between a local area network (LAN) and the Internet. Its LAN interface knows which packets are in the VLAN, but its WAN interface on the Internet does not work. Therefore, the border router must be set to yes. The EF bits of the DSCP field for all packets in the voice VLAN. It sets all the bits in the DSCP field to & # 39; for all traffic in the default VLAN or data.
The capabilities of the border router (QoS) must be enabled for traffic going to the Internet through its WAN interface. Packages are sent to him with an EF field set to “yes”. for those that were originally in voice vlan. QoS settings recognize the EF field and prioritize voice packets on the Internet.
For the successful implementation of business VoIP services, such as Hosted PBX and Hosted VoIP, the priority of voice packet transmission to the Internet is crucial. Of the two ways to prioritize voice, VLANs require additional hardware (managed Ethernet switches) and additional programming. However, they can perform an excellent job, including call signaling in the prioritization queues and excluding any critical non-mission traffic.
