VoIP also makes possible other services that older telephony systems can’t
provide. VoIP telephony services are interoperable, meaning that they workwell over all kinds of networks. They are also highly portable, which meansthey will work with any IP-enabled device such as an IP telephone, a computer,or even a personal digital assistant (PDA).IP telephony works by taking traditional voice signals and converting them toa form that can be easily transmitted over a local area network. Thus, theheart of IP telephony is the same as traditional data networking with computers.IP-enabled phones handle the voice-to-data conversion well, but don’t bemisled — implementing VoIP doesn’t mean that everyone has to use IP-enabledphones. The best VoIP providers implement IP telephony in a manner thatprotects your investment in existing telephone equipment, even if you haveanalog telephone stations. (You’ll find more on this topic in Chapter 10.)All IP phones have one important thing in common: a built-in network interfacecard (NIC), just like a computer uses. The NIC is critical for any networkdevice because it provides the device with a physical address and a way tocommunicate over the network.The physical address supplied by a NIC is called a MAC address. MAC standsfor media access control. The MAC address uses a standardized address andis usually represented by six hexadecimal numbers separated by dashes. Forexample, the following is a valid MAC address: 00-0A-E4-02-7B-99.To support IP telephony, a server is typically dedicated to run the softwareused to manage calls. Servers are just like personal computers, except theyhave more memory, speed, and capacity. The server stores the database thatcontains all the MAC addresses corresponding to all the IP telephone extensionsassigned to users. Depending on the size of the LAN and the number ofusers, you may use more than one server. For example, some LANs running IPtelephony dedicate a server just for handling voice mail.Depending on the size of the LAN, one or more devices known as switchesare installed. These switches are boxes that have a series of ports into whichall LAN-addressable devices ultimately connect. (Examples of LAN-addressabledevices include computers, printers, wireless access devices, gateways, andstorage devices.) Usually the switches are set up in the communications closetsaround the LAN, and they operate 24/7. All the switches are interconnected,often with fiber-optic cable.In a nutshell, all network devices, including your IP telephone, must physicallyconnect to the LAN through a port on a switch.
provide. VoIP telephony services are interoperable, meaning that they workwell over all kinds of networks. They are also highly portable, which meansthey will work with any IP-enabled device such as an IP telephone, a computer,or even a personal digital assistant (PDA).IP telephony works by taking traditional voice signals and converting them toa form that can be easily transmitted over a local area network. Thus, theheart of IP telephony is the same as traditional data networking with computers.IP-enabled phones handle the voice-to-data conversion well, but don’t bemisled — implementing VoIP doesn’t mean that everyone has to use IP-enabledphones. The best VoIP providers implement IP telephony in a manner thatprotects your investment in existing telephone equipment, even if you haveanalog telephone stations. (You’ll find more on this topic in Chapter 10.)All IP phones have one important thing in common: a built-in network interfacecard (NIC), just like a computer uses. The NIC is critical for any networkdevice because it provides the device with a physical address and a way tocommunicate over the network.The physical address supplied by a NIC is called a MAC address. MAC standsfor media access control. The MAC address uses a standardized address andis usually represented by six hexadecimal numbers separated by dashes. Forexample, the following is a valid MAC address: 00-0A-E4-02-7B-99.To support IP telephony, a server is typically dedicated to run the softwareused to manage calls. Servers are just like personal computers, except theyhave more memory, speed, and capacity. The server stores the database thatcontains all the MAC addresses corresponding to all the IP telephone extensionsassigned to users. Depending on the size of the LAN and the number ofusers, you may use more than one server. For example, some LANs running IPtelephony dedicate a server just for handling voice mail.Depending on the size of the LAN, one or more devices known as switchesare installed. These switches are boxes that have a series of ports into whichall LAN-addressable devices ultimately connect. (Examples of LAN-addressabledevices include computers, printers, wireless access devices, gateways, andstorage devices.) Usually the switches are set up in the communications closetsaround the LAN, and they operate 24/7. All the switches are interconnected,often with fiber-optic cable.In a nutshell, all network devices, including your IP telephone, must physicallyconnect to the LAN through a port on a switch.
