LAN Protocols

In addition to the physical or wireless transmission media that carry the network’s signals, a network also uses protocols (standards) that enable network-connected device to communicate with each other. What are protocols? They’re like the manners you were growing up, you were taught to say certain fixed things, such as “It’s nice to meet you,” when u met someone in a social situation. The other person was taught to reply, “It’s nice to meet you, too.” Such exchangers serve to get communication going. Network protocols are similar. They are fixed, formalized exchange that specifies how two dissimilar network components can establish a communication. All of the communications devices in a network conform to different protocols. Take modems, for example. To establish communications, modems must conform to standard called modulation protocols. Which ensure that your modem can communicate with another modem, even if the second modem was made by a different manufacturer.

Internet Backbones

The LANs and WANs that make up the Internet are connected to the Internet backbone. Some backbones are regional, connecting towns and cities in a region such as southern California or New England. Others are continental, or even transcontinental, in scope. Whatever their scope, backbones are designed to carry huge amounts of data traffic. Cross-country Internet backbones, for example, can handle nearly 5.5GBps, and much higher speeds are on the way. A current federally funded research project is constructing a backbone network that will operate at speeds of 17GBps to 18.4GBps. To understand how data travel over a WAN, it helps to understand how data travel over the Internet. This journey can be compared with an interstate car trip. When you connect to the Internet and request access to a Web page, your request travels by local connections-the city streets-to your ISP’s local POP. From there, your ISP relays your request to the regional backbone-a high-way. Your request then goes to network access point-highway on-ramp-where regional backbones connects with national backbone networks. And from there, the message gets on the national backbone network-the interstate. When your request nears its destination, your message gets off the national backbone network and travels regional and local networks until it reaches its destination.