Computer Networking Explained: Types of Networks, LAN vs WAN & Interconnect Devices

Network

A network is a group of two or more computer systems linked together. There are many types of computer networks, including:

1. Local-area networks (LANs): The computers are geographically close together (that is, in the same building).
2. Wide-area networks (WANs): The computers are farther apart and are connected by telephone lines or radio waves.
3. Campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base.
4. Metropolitan-area networks MANs): A data network designed for a town or city.
5. Home-area networks (HANs): A network contained within a user's home that connects a person's digital devices.

In addition to these types, the following characteristics are also used to categorize different types of networks:

1. Topology: The geometric arrangement of a computer system. Common topologies include a bus, star, and ring.
2. Protocol: The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network.
3. Architecture: Networks can be broadly classified as using either a peer-to-peer or client/server architecture. Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers. To connect two or more computers together with the ability to communicate with each other.

What is (Computer) Networking?

In the world of computers, networking is the practice of linking two or more computing devices together for the purpose of sharing data. Networks are built with a mix of computer hardware and computer software.

1. Area Networks - Networks can be categorized in several different ways. One approach defines the type of network according to the geographic area it spans. Local area networks (LANs), for example, typically span a single home, school, or small office building, whereas wide area networks (WANs), reach across cities, states, or even across the world. The Internet is the world's largest public WAN.
2. Network Design - Computer networks also differ in their design. The two basic forms of network design are called client/server and peer-to-peer. Client-server networks feature centralized server computers that store email, Web pages, files and or applications. On a peer-to-peer network, conversely, all computers tend to support the same functions. Client-server networks are much more common in business and peer-to-peer networks much more common in homes. A network topology represents its layout or structure from the point of view of data flow. In so-called bus networks, for example, all of the computers share and communicate across one common conduit, whereas in a star network, all data flows through one centralized device. Common types of network topologies include bus, star, ring networks and mesh networks.
3. Network Protocols - Communication languages used by computer devices are called network protocol. Yet another way to classify computer networks is by the set of protocols they support. Networks often implement multiple protocols with each supporting specific application. Popular protocols include TCP/IP, the most common protocol found on the Internet and in home networks.
4. Home Networking - While other types of networks are built and maintained by engineers, home networks belong to ordinary homeowners, people often with little or no technical background. Various manufacturers produce broadband router hardware designed to simplify home network setup. Home broadband routers allow devices in different rooms to efficiently share a broadband Internet connection, enable people to more easily share their files and printers within the network, and help with overall network security. Home networks have increased in capability with each generation of new technology. Years ago, people commonly set up their home network just to connect a few PCs, share some documents and perhaps a printer. Now it’s common for households to also network game consoles, digital video recorders, and smart phones for streaming sound and video. Home automation systems have also existed for many years, but these too have grown in popularity more recently with practical systems for controlling lights, digital thermostats and appliances.
5. Business Networks - Small and home office (SOHO) environments use similar technology as found in home networks. Businesses often have additional communication, data storage, and security requirements that require expanding their networks in different ways, particularly as the business gets larger. Whereas a home network generally functions as one LAN, a business network tends to contain multiple LANs. Companies with buildings in multiple locations utilize wide-area networking to connect these branch offices together. Though also available and used by some households, voice over IP communication and network storage and backup technologies are prevalent in businesses. Larger companies also maintain their own internal Web sites, called intranets to help with employee business communication.
6. Networking and the Internet - The popularity of computer networks sharply increased with the creation of the World Wide Web (WWW) in the 1990s. Public Web sites, peer to peer (P2P) file sharing systems, and various other services run on Internet servers across the world.
7. Wired vs. Wireless Networking - Many of the same network protocols, like TCP/IP, work in both wired and wireless networks. Networks with Ethernet cables predominated in businesses, schools, and homes for several decades. More recently, however, wireless alternatives have emerged as the premier technology for building new computer networks, in part to support smart phones and the other new kinds of wireless gadgets that have triggered the rise of mobile networking.

Network Types

One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are:

• 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, Controller Area Network, or sometimes Cluster Area Network
• PAN - Personal Area Network
• DAN - Desk Area Network

LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution. Note that these network types are a separate concept from network topologies such as bus, ring and star.

LAN - Local Area Network - A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet. In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring.

WAN - Wide Area Network - As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth. A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address. A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances.

LAN, WAN and Home Networking - Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically a broadband router, to reach the ISP.

Other Types of Area Networks

While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others:

1. Wireless Local Area Network - a LAN based on WiFi wireless network technology
2. Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned and operated by a single entity such as a government body or large corporation.
3. Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.
4. Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel.
5. System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.

Difference between LAN (local area network) and WAN (Wide area network)

LAN (Local Area Network)	WAN (Wide Area Network)
A LAN is a computer network covering a small geographic area such as home, office, school, or group of buildings.	A WAN is a computer network covering a broad area (e.g., country or continent) whose communication links cross metropolitan, regional, or national boundaries.
High speed – around 1000 Mbps	Lower speed – around 50 Mbps
Experiences fewer data transmission errors	Experiences more data transmission errors compared to LAN
Uses Ethernet, Token Ring, and short-distance communication technologies	Uses MPLS, ATM, Frame Relay, X.25, and long-distance communication technologies
LANs cover only short-distance wired connections	WANs involve long-distance connections using leased lines, satellites, or radio waves
Includes Layer 2 devices like switches, hubs, bridges, and Ethernet cables	Includes Layer 3 devices like routers, multi-layer switches, and advanced transmission media
LANs tend to have fewer problems and are easier to manage	WANs need to be more fault tolerant because they consist of many interconnected systems
Usually owned and managed by a single person or organization	Ownership may be collective or distributed across different branches
Relatively inexpensive to set up	Very expensive to set up due to long-range infrastructure
Spread to a very small location	Spread worldwide
High bandwidth available	Lower bandwidth compared to LAN
Less congestion	More congestion

Network Interconnect Devices

Repeaters

As signals travel along a network cable (or any other medium of transmission), they degrade and become distorted in a process that is called attenuation. If a cable is long enough, the attenuation will finally make a signal unrecognizable by the receiver. A Repeater enables signals to travel longer distances over a network. Repeaters work at the OSI's Physical layer. A repeater regenerates the received signals and then retransmits the regenerated (or conditioned) signals on other segments. To pass data through the repeater in a usable fashion from one segment to the next, the packets and the Logical Link Control (LLC) protocols must be the same on each segment. This means that a repeater will not enable communication, for example, between an 802.3 segment (Ethernet) and an 802.5 segment (Token Ring). That is, they cannot translate an Ethernet packet into a Token Ring packet. In other words, repeaters do not translate anything.

Bridge 

A bridge reads the outermost section of data on the data packet, to tell where the message is going. It reduces the traffic on other network segments, since it does not send all packets. Bridges can be programmed to reject packets from particular networks. Bridging occurs at the data link layer of the OSI model, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. In our case the bridge can read the Ethernet data which gives the hardware address of the destination address, not the IP address. Bridges forward all broadcast messages. Only a special bridge called a translation bridge will allow two networks of different architectures to be connected. Bridges do not normally allow connection of networks with different architectures. The hardware address is also called the MAC (media access control) address. To determine the network segment a MAC address belongs to, bridges use one of:

1. Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on Ethernet networks.
2. Source route bridging - The source computer provides path information inside the packet. This is used on Token Ring networks.

Routers

In an environment consisting of several network segments with different protocols and architecture, a bridge may not be adequate for ensuring fast communication among all of the segments. A complex network needs a device, which not only knows the address of each segment, but also can determine the best path for sending data and filtering broadcast traffic to the local segment. Such device is called a Router. Routers work at the Network layer of the OSI model meaning that the Routers can switch h and route packets across multiple networks. They do this by exchanging protocol-specific information between separate networks. Routers have access to more information in packets than bridges, and use this information to improve packet deliveries. Routers are usually used in a complex network situation because they provide better traffic management than bridges and do not pass broadcast traffic. Routers can share status and routing information with one another and use this information to bypass slow or malfunctioning connections. Routers do not look at the destination node address; they only look at the network address. Routers will only pass the information if the network address is known. This ability to control the data passing through the router reduces the amount of traffic between networks and allows routers to use these links more efficiently than bridge.

Gateways

Gateways make communication possible between different architectures and environments. They repackage and convert data going from one environment to another so that each environment can understand the other's environment data. A gateway repackages information to match the requirements of the destination system. Gateways can change the format of a message so that it will conform to the application program at the receiving end of the transfer. A gateway links two systems that do not use the same:

• Communication protocols
• Data formatting structures
• Languages
• Architecture

For example, electronic mail gateways, such as X.400 gateway, receive messages in one format, and then translate it, and forward in X.400 format used by the receiver, and vice versa. To process the data, the gateway: Decapsulates incoming data through the networks complete protocol stack. Encapsulates the outgoing data in the complete protocol stack of the other network to allow transmission.

Brouter 

There is a device called a brouter which will function similar to a bridge for network transport protocols that are not routable, and will function as a router for routable protocols. It functions at the network and data link layers of the OSI network model.

NIC 

A NIC or Network Interface Card is a circuit board or chip, which allows the computer to communicate to other computers on a Network. This board when connected to a cable or other method of transferring data such as infrared can share resources, information and computer hardware. Local or Wide area networks are generally used for large businesses as well as are beginning to be found in homes as home users begin to have more than one computer. Utilizing network cards to connect to a network allow users to share data such as companies being able to have the capability of having a database that can be accessed all at the same time send and receive e-mail internally within the company or share hardware devices such as printers.

Connectors

Network cards have three main types of connectors. Below is an example of what a network card may look like.

1. BNC connector: As illustrated in the above picture the BNC connector is a round connector, which is used for thin net or 10Base-2 Local Area Network.
2. DB9 (RJ45 JACK): The DB9 connector not to be confused with the Serial Port or sometimes referred to as the RJ45 JACK not to be confused with the RJ45 connection is used with Token Ring networks.
3. DB15 Connector: The DB15 connector is used for a thick net or 10Base-5 Local area network.
4. RJ45 connector: Today one of the most popular types of connections used with computer networks. RJ45 looks similar to a phone connector or RJ11 connector however is slightly larger.
5. LED - The LED's as shown in the above illustration indicates if it detects a network generally by a green light which may flash as it communicates and then a red light which indicates collisions which will generally flash or not flash at all.

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Sandeep Ghatuary

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