entification number called a physical address because it is put there by the manufacturer as part of the hardware manufacturing process and remains fixed in the card for life. The IEEE administers the standard for creating and producing these numbers for each card. The process requires each manufacturer to register with the IEEE, whereupon they receive unique manufacturer identification, and then the manufacturer is responsible for creating unique numbers for each card built and shipped. To be just a bit more specific, a MAC address is assigned to each network port on any device. For example, many motherboards in computers have built in LAN ports. Other plug-in cards may be built to accommodate multiple LAN connections such as a virtual local area network (VLAN) cards in a router, or LAN emulation (LANE) cards in an ATM switch. Internet identification is accomplished by assigning network- wide unique IP addresses to each device on the network. Successful connectivity between two or more hosts on an IP network involves a translation scheme where the unique IP address is subjected to an address resolution process involving the local network add- ressing scheme or protocol and the physical or MAC address. For example, the local network is likely to be some version of Ethernet. TABLE 4-4 Network type Application or use Signaling technique Data Networks LAN, MAN, WAN Connectivity Layer 2 IEEE 802.x Logical Link Voice Networks Local, Regional & Long Distance Calling DTMF, CCS7/SS7 Internet Network Connectivity PPP, L2TP IGP, BGP PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS Signaling, even in general, is beyond the scope of this book. How- ever, literature is widely available from many sources, the least expensive of which is your favorite Internet browser. SWITCHING Here we will consider several types of switching: circuit switching, cell switching, and packet switching. While there's less confusion surrounding switching than routing, there's still enough to elicit caution when discussing, reading,