This lesson will provide a very basic overview of computer networks covering types of networks, common topologies, networking standards, devices, and modes of access. Please note this is a very high level overview and the information contained in these slides is intended for general knowledge only.
A computer network is a group of interconnected computers.
A computer network is a group of interconnected computers. While the term “network” and “LAN” are often used interchangeably by some, the term LAN describes a fairly specific type of computer network. In this, and the next slide, we will discuss three common types of computer networks. A Local Area Network (LAN) is a computer network for a “small” geographic area – small being a relative term here. A LAN could consist of a few computers or thousands. LANs can be interconnected or uplinked to much larger networks to provide even greater connectivity. LANs are by far the most common computer network. LANs are typically owned and operated by a single organization, such as a business or school. A Metropolitan Area Network (MAN) typically involves much larger distances and scope of systems than a LAN. For example, a MAN may connect all the major office buildings in a city and be owned and operated by a local telecommunications company. A MAN can be used to connect various LANs together
A Wide Area Network (WAN) is characterized primarily by distance – a WAN is used to interconnect LANs, MANs, or other networks together. For example, a WAN might be used to connect a company’s offices in Dallas to their offices in New York City. Each of the offices will have their own LAN but the WAN connecting the two offices will allow them to communicate between the two offices in different cities.
From Wikipedia: “Network topology is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes. A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that determines the physical topology of the network. Likewise, the mapping of the flow of data between the nodes in the network determines the logical topology of the network.” A LAN is typically built using one of 3 main types of topologies: Bus: In a bus topology all of the nodes in the network are connected to a common transmission medium (often called the “backbone” or “bus”). Data transmitted between nodes must travel along the common medium. Ring: In a ring topology, each node is connected to two other nodes forming a ring as seen in the illustration. Data travels in a circular pattern from node to node. Star: In a star topology, each of the nodes is connected to a central element (usually a switch) in a point to point fashion. Data travelling between nodes must pass through the central node.
In order for nodes on networks to communicate they all have to be able to “speak the same language”. Networking standards are usually quite technical and specify things such as the voltage used across wires, maximum length of a cable, and how to handle multiple nodes using the same common medium. The Ethernet standard is by far the most popular and commonly used networking standard. It’s low cost and ease of use make it the de facto standards for LANs around the world. Token Ring is one of the networking standards that feel victim to the success of the Ethernet standard. Once popular in banks and financial institutions, Token Ring is rarely used today. WiFi is another popular and commonly used networking standard, especially in campus environments such as colleges. Due to their very nature of being broadcast using radio waves, wireless networks have some rather unique privacy and security issues.
Network topologies have both a physical and logical component. All Ethernet networks use a shared access mode and common media (at some level). Ring topologies tend to use token based access models as information must be passed from node to node within the ring to be transmitted. Star topologies are the most common physical topology and tend to use Ethernet as the networking standard.
A Network Interface Controller (a NIC or network card as it is sometimes called) is the piece of hardware that connects your computer to the network. It handles the physical connection of your computer to the network which can be wire-based or wireless. By specification, every NIC should have a unique Media Access Control (MAC) address. A hub is a device that connects multiple wires together and makes them appear to be one logical wire. Hubs are rarely used today as they are slower and less efficient than most switches and allow every system connected to the hub to see every packet that passes through the hub. A switch connects multiple nodes together and is often used as the “central node” in a star topology. Switches help control traffic in a network by only forwarding traffic to nodes that need to receive it. This is desirable from both a security and a traffic reduction perspective.
Cable modems are used to connect computers (typically home and small business networks) to broadband services provided by cable providers. These modems use the same CATV cable infrastructure as cable television. Similar to a cable modem in usage, a DSL modem is used to provide high-speed Internet access across traditional telephone wires. A wireless access point is a device that uses radio waves as the physical medium to connect nodes within a wireless network. Wireless networks are limited in range due to the radiated power of the access point and the frequencies used. Because wireless networks use radio waves as their physical medium, wireless networks tend to extend beyond the physical boundaries of the location they are installed in.
Dial-up access is another means of providing Internet access through traditional telephone lines. Dial-up access requires a telephone line and physical device, called a modem, that sends and receives tones across the telephone lines to provide Internet access.
Most Ethernet cabling consists of 4 pairs of wires twisted together in a specific fashion to reduce interference from the wires next to them. Twisted pair cabling is the most common cabling used in networks today.
LAN – A Local Area Network is a computer network covering a small geographic area, like a home, office, or group of buildings.
Each node (computer) on the LAN has its own computing power but can also access other devices on the LAN subject to the permissions it has been allowed. These could include data, processing power, and the ability to communicate or chat with other users in the network.
The defining characteristics of LANs include their high data transfer rates, small geographic range, and lack of a need for leased telecommunication lines
MAN – Metropolitan Area Networks are large computer networks usually spanning a city. They may use wireless infrastructure or optical fiber connections to link their sites.
As with LANs, MANs also use communications channels of moderate-to-high data rates
Might be owned and operated by a single organization, but usually used by many individuals and organizations
A form of Internet access through which the client uses a modem connected to a computer and a telephone line to dial into an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then routed to the Internet
Turns the digital '1s and 0s' of a personal computer into sounds that can be transmitted and received over telephone lines
Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources and crosstalk from neighboring wires
This cable has an RJ-45 jack on each end
It connects your PC to the wall (hub, router, etc.)
CyberPatriot wants to thank and acknowledge the CyberWatch program which developed the original version of these slides and who has graciously allowed their use for training in this competition. List of References