Chapter 3


What the three components of a frame?


Answer: Header, payload, and trailer.


What is a bit?


Answer: Bit is short for "binary digit" and is the smallest unit of information that can reside on a computer or be carried by a network communications device.


What are the main characteristics and differences between a LAN and a WAN?


Answer: LANs are networks confined to relatively small geographic areas, such as within a building, or a house. LANs use hubs, bridges, switches, and routers to connect LAN segments together. WANs are networks spanning across broad geographic areas, such as between cities across a state, country, or the world, interconnecting LANs from these locations. WANs use routers to connect these LANs together.


How does a repeater work?


Answer: A repeater is a communications device that amplifies or regenerates a signal extending the transmission distance of the signal across the network.


How does a hub work?


Answer: A hub is a multiport repeater; when a signal is received on one port, it is forwarded out all ports on the hub. It is up to each network device attached to the hub to determine whether it is the intended recipient of the signal traffic.


How does a bridge or switch work?


Answer: A bridge or switch learns the MAC addresses of devices on the respective sides of the two interfaces. The information helps keep frames that are destined for the local subnet from passing over the bridge and wasting bandwidth on the other side. If it knows that a specific MAC address is on one side, the bridge drops the frame. Bridges forward broadcasts out all ports, as well as forward frames destined for a MAC for which the bridge has no entry in its table.


What is the difference between a bridge and a switch?


Answer: A bridge is considered a multiport hub, whereas a switch is considered to be a multiport bridge with multiple network segments that might, or might not, communicate with each other. Switches also build tables based on the MAC address received on each switch port and forward frames based on these tables.


What is the difference between a physical topology and a logical topology?


Answer: Physical topology is the actual physical, or real, arrangement of network devices via some sort of media, such as copper or fiber-optic cabling. Logical topology is the virtual arrangement of network devices, made possible by the physical topology. The logical and physical topologies might look similar when laid out, but the logical topology is based on user communication requirements. For example, because a frame passes through a switch does not mean it must stop at that switch on its way to its destination.