| As use of Voice over Internet Protocol (VoIP) | | | | cannot share an IP address which means no |
| continues to grow at a frenetic pace, new users are | | | | softphones. The computer can use the small Ethernet |
| frequently surprised by the frequency of problems. | | | | switch on the back of most IP Telephones and share |
| Unless the user has more bandwidth than his needs | | | | a single Ethernet cable back to the managed switch. |
| could ever consume, users of Vonage, Skype, Google | | | | In setting up the VLAN, all computers and |
| Voice, as well as users of business-type services like | | | | non-telephony devices are programmed as members |
| Hosted PBX, Virtual PBX and Hosted VoIP will | | | | of the default data VLAN. All VoIP telephones should |
| experience trouble. Experienced and successful VoIP | | | | be members of the voice VLAN. |
| users have learned that with proper planning and care, | | | | The router is on the edge between the Local Area |
| VoIP does live up to its hype. | | | | Network (LAN) and the Internet. Its LAN interface does |
| Voice prioritization is one of many areas that require a | | | | know which packets are in which VLAN but its Wide |
| network administrator's attention. Voice prioritization | | | | Area Network (WAN) interface to the Internet does |
| can be handled by the Differentiated Service Code | | | | not. Thus, the edge router must set to 'yes' the EF bits |
| Point (DSCP) field in the network's packets or by | | | | of the DSCP field for all packets in the voice VLAN. It |
| segmenting VoIP equipment into a separate VLAN. | | | | sets all the bits of the DSCP field to 'no' for all traffic in |
| This article discusses the set-up of VLANs for | | | | the default or data VLAN. |
| successful VoIP transmission. | | | | The edge router's Quality of Service (QoS) capabilities |
| VLANs have several advantages over using only the | | | | should be enabled for traffic going out to the Internet |
| DSCP field, although they are somewhat more difficult | | | | on its WAN interface. Packets are sent to it with the |
| to construct. They can effectively prioritize all of the | | | | EF field set to 'yes' for only those that were originally in |
| mission critical VoIP traffic including call signaling. They | | | | the voice VLAN. The QoS settings recognize the EF |
| will also exclude packets generated on computers that | | | | field and prioritizes the voice packets out to the |
| use the Expedited Forward (EF) Per Hop Behavior | | | | Internet. |
| (PHB) of the DSCP field that may compete with | | | | For successful implementation of business VoIP |
| mission critical VoIP. Additional advantages include the | | | | services like Hosted PBX and Hosted VoIP, |
| reduction of broadcast network traffic as well as | | | | prioritization of voice packets out to the Internet is |
| higher security as other computers in other VLANs will | | | | crucial. Of the two methods for establishing voice |
| not be able to monitor phone calls. | | | | priority, VLANs require some extra hardware |
| The network needs a managed Ethernet switch and | | | | (managed Ethernet Switches) and a extra |
| an Internet router capable of manipulating the DSCP | | | | programming. However, they can do a superior job by |
| field to successfully implement a VLAN for voice | | | | including call signaling in the prioritization queues and |
| prioritization. In addition, the computer and VoIP endpoint | | | | excluding any non-mission critical traffic. |