Title: 1.5 Network Topologies
Course: Information and Communication Technology: Module B > Section: Section 1 - Telecommunications and Network Basics

1.5.1 Network Topology

Topology refers to the general shape or layout of a network. Every computer network has both a physical and logical topologies:

- Physical topologies are the layout of the networking cables, devices, and workstations.
- Logical topologies dictate the path data takes between devices and workstations (how data flows).

Common network topologies include:

- Bus—Connects all devices (also known as hosts or nodes) to the same medium or wire and requires a terminator at both ends of the bus.
- Star—Connects all cables to a central point of concentration. It is easy to add more nodes. Star topology is very popular because it is easy to diagnose connection problems.
- Extended Star—Created by linking together several star topologies to a central point. It is considered the topology of choice for structured cabling systems.
- Ring—Uses a closed loop configuration. A token is passed around the loop in sequential order to transmit data.
- Mesh—Provides total redundancy for a network by connecting each host to every other host.
- Cellular—Uses radio waves to broadcast signals. Coverage depends on the direction and distance from a tower.

There are three ways that the data channels over which a signal is sent can operate:

- Simplex transmission is a single one-way base band transmission that only travels in one direction, as in TV broadcasting.
- Half-duplex transmission is an improvement over simplex because the traffic can travel in both directions—but only in one direction at a time (transmit or receive), as in walkie-talkies.
- Full-duplex transmission operates like a two-way, two-lane street. Traffic can travel in both directions at the same time, as in cell phones.

Please complete assignment 1.5.1 in the lab manual.

1.5.2 Network Topology

Communications networks are typically categorized network by size. Examples of different network types are listed here:

- LAN—Local Area Network
- WLAN—Wireless Local Area Network
- WAN—Wide Area Network
- MAN—Metropolitan Area Network
- SAN—Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network
- CAN—Campus Area Network
- PAN—Personal Area Network

LAN and WAN were the original categories of area networks. Other network types have been developed and new technologies have been developed for longer-distance connectivity.

1.5.3 Network Topology

Local Area Networks (LANs) connect many computers in a small geographical area such as a home, an office, a building, or a campus. LANs require the networked computers to share a communications channel called the medium.

In TCP/IP networking, a LAN is often (but not always) implemented as a single IP subnet.  In addition, LANs are typically owned and controlled internal to a home or business and today are Ethernet based.

Wide Area Networks (WANs) connect computers in a large geographical area such as cities, states, and countries. WANs require some type of service provider. Wide area connections between computers use point-to-point or serial communications lines.

Point-to-point lines connect only two computers, one on each side of the line. Wide area connections make use of the communications facilities put in place by the utility companies, called common carriers, such as the telephone company.

WANs typically connect fewer computers than LANs and normally operate at lower speeds than LANs. WANs, however, provide the means for connecting single computers and many LANs over large distances. A network device called a router connects LANs to a WAN. In IP networking, the router maintains addresses for both LAN interfaces and for WAN interfaces.

Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a cable or DSL broadband modem. The ISP provides a single WAN IP address to the modem, and all of the home network devices use internal LAN IP addresses. All computers on the home LAN can communicate directly with each other but they must go through the ISP-supplied broadband router gateway for Internet access.

Please complete assignment 1.5.2 in the lab manual.