NETWORKS
A computer network is a communication system that connects two or more Computer so that they can exchange information and share resources. Networks can be set up in different arrangements to suit users' needs.
TERMS
There are a number of specialized terms that describe computer networks. These terms include
● Node - Any device that is connected to a network. It could be a computer, printer, or data storage device.
● Client - A node that requests and uses resources available from other nodes.Typically, a client is a user's personal computer.
● Server - A node that shares resources with other nodes. Dedicated servers specialize in performing specific tasks. Depending on the specific task, they may be called an application server, communication server, database server, file server, printer server, or web server.
● Directory server - A specialized server that manages resources, such as user accounts, for an entire network.
● Host - any computer system connected to a network that provides access to its resources.
● Router - a node that forwards or routes data packets from one network to their destination in another network.
● Switch - central node that coordinates the flow of data by sending messages directly between sender and receiver nodes. A hub previously filled this purpose by sending a received message to all connected nodes, rather than just the intended node.
● Network interface cards (NIC) - as discussed in Chapter 5, these are expansion cards located within the system unit that connect the computer to a network. Sometimes referred to as a LAN adapter.
● Network operating systems (NOS) - control and coordinate the activities of all computers and other devices on a network. These activities include electronic communication and the sharing of information and resources.
● Network administrator - a computer specialist responsible for efficient network operations and implementation of new networks.
A network may consist only of personal computer, or it may integrate personal computers or other devices with larger computers, Networks can be controlled by all nodes working together equally or by specialized nodes coordinating and supplying all resources. Networks may be simple or complex, self-contained or dispersed over a large geographic area.
Questions :-
What is a computer network? What are nodes, clients, servers, directory servers,hosts, routers, and switches?
What is the function of an NIC and an NOS?
What is a network administrator?
NETWORK TYPES
Clearly, different types of channels-wired or wireless-allow different kinds Cof networks to be formed. Telephone lines, for instance, may connect communications equipment within the same building or within a home, Networks also may be citywide and even international, using both cable and wireless connection. Local area, metropolitan area, and wide area networks are distinguished by the size of the geographic area they serve.
LOCAL AREA NETWORKS
Networks with nodes that are in close physical proximity-within the same building, for instance-are called local area networks (LANS). Typically, LANs span distances less than a mile and are owned and operated by individual organizations. LANS are widely used by colleges, universities, and other types of organizations to link personal computers and to share printers and other resources. For a simple LAN.
The LAN is a typical arrangement and provides two benefits: economy and flexibility. People can share costly equipment. For instance, the four personal computers share the high-speed laser printer and the file server, which are expensive pieces of hardware. Other equipment or nodes also may be added to the LAN-for instance, more personal computers, a mainframe computer, or optical disc storage devices. Additionally, the network gateway is a device that allows one LAN to be linked to other LANs or to larger networks. For example, the LAN of one office group may be connected to the LAN of another office group.
There are a variety of different standards or ways in which nodes can be connected to one another and ways in which their communications are controlled in a LAN. The most common standard is known as Ethernet. LANs using this standard are sometimes referred to as Ethernet LANS.
HOME NETWORK
While LANs have been widely used within organizations for years, they are now being commonly used by individuals in their homes and apartments. These LANs, called home network, allow different computers to share resources, including a common Internet connection. Computers can be connected in a variety of ways, including electrical wiring, telephone wiring, and special cables. One of the simplest ways, however, is without cable, or wireless.
WIRELESS LAN
A wireless local area network is typically referred to as a wireless LAN (WLAN). It uses radio frequencies to connect computers and other devices. All communications pass through the network's centrally located wireless access point or base station. This access point interprets incoming radio frequencies and routes communications to the appropriate devices.
Wireless access points that provide Internet access are widely available in public places such as coffee shops, libraries, bookstores, colleges, and universities. These access points are known as hotspots and typically use Wi Fi technology. Many of these services are free and easy to find using free locator sites such as www.hotspot-locations.com. Most mobile computing devices have an internal wireless network card to connect to hotspot. If your mobile device does not have an internal wireless network card, you can use an external wireless adapter that plugs into your computer's USB port or PC card slot.
PERSONAL AREA NETWORK
A personal area network (PAN) is a type of wireless network that works within A a very small area-your immediate surroundings. PANs connect cell phones to headsets, keyboards to cell phones, and so on. These networks make it possible for wireless devices to interact with each other. The most popular PAN technology is Bluetooth, with a maximum range of around 33 feet, Virtually all wireless peripheral devices available today use Bluetooth, including the controllers on popular game systems like the PlayStation and Wii.
METROPOLITAN AREA NETWORKS
Metropolitan area networks (MAN) span distances up to 100 miles. These networks are frequently used as links between office buildings that are located throughout a city
Unlike a LAN, a MAN is typically not owned by a single organization. Rather, it is owned either by a group of organizations or by a single network service provider that provides network services for a fee.
WIDE AREA NETWORKS
Wide area networks (WANs) are countrywide and worldwide networks. These networks provide access to regional service (MAN) providers and typically span distances greater than 100 miles. They use microwave relays and satellites to reach users over Long distances-for example, from Los Angeles Paris, Of course, the widest of all WANS is the Internet, which spans the entire globe.
The primary difference between a PAN, LAN, MAN, and WAN is the geographic range. Each may have various combinations of hardware, such as personal computers, midrange computer, mainframe, and various peripheral devices.
NETWORK ARCHITECTURE
Network architecture describes how a network is arranged and how IVresources are coordinated and shared. It encompasses a variety of different network specifics, including network topologies and strategies. Network topology describes the physical arrangement of the network. Network strategies define how information and resources are shared.
TOPOLOGIES
A network can be arranged or configured in several different ways. This arrangement is called the network's topology. The most common topologies are
● Bus network - each device is connected to a common cable called a bus or backbone, and all communications travel along this bus.
● Ring network - each device is connected to two other devices, forming a ring.When a message is sent, it is passed around the ring until it reaches the intended destination.
● Star network - device is connected directly to a central network switch.Whenever a node sends a message, it is routed to the switch, which then passes the message along to the intended recipient. The star network is the most widely used network topology today. It is applied to a broad range of applications from small networks in the home to very large networks in major corporations.
● Tree network - each device is connected to a central node, either directly or through one or more other devices. The central node is connected to two or more subordinate nodes that in turn are connected to other subordinate nodes, and so forth, forming a treelike structure.This network, also known as a hierarchical network, is often used to share corporate wide data.
● Mesh network - this topology is the newest type and does not use a specific physical layout (such as a star or a tree). Rather, the mesh network requires that each node have more than one connection to the other nodes. The resulting pattern forms the appearance of a mesh. If a path between two nodes is somehow disrupted, data can be automatically rerouted around the failure using another path. Wireless technologies are frequently used to build mesh network.
STRATEGIES
Every network has a strategy, or way of coordinating the sharing of information and resources. Two of the most common network strategies are client/server and peer-to-peer.
Client/server networks use central servers to coordinate and supply services to other nodes on the network. The server provides access to resources such as web pages, databases, application software, and hardware. This strategy is based on specialization Server nodes coordinate and supply specialized services, and client nodes request the services. Commonly used server operating systems are Windows Server, Mac OS X Server, Linux, and Solaris.
Client/server networks are widely used on the Internet. For example, each time you open a web browser, your computer (the client) sends out a request for a specific web page. This request is routed over the Internet to a server. This server locates and sends the requested material back to your computer.
One advantage of the client/server network strategy is the ability to handle very large networks efficiently. Another advantage is the availability of powerful network management software to monitor and control network activities. The major disadvantages are the cost of installation and maintenance.
In a peer-to-peer (P2P) network, nodes have equal authority and can act as both clients and servers. The most common way to share games, movies, and music over the Internet is to use a P2P network. For example, special file sharing software such as BitTorrent can be used to obtain files located on another personal computer and also can provide files to other personal computers.
P2P networks are rapidly growing in popularity as people continue to share information with others around the world. The primary advantage is that they are easy and inexpensive (often free) to set up and use. One disadvantage of P2P networks is the lack of security controls or other common management functions, For this reason, few businesses use this type of network to communicate sensitive information
Questions :-
What is a network topology?
Compare bus, ring, star, tree, and mesh topologies.
What is a network strategy?
Compare client/server and peer-to-peer strategies.
ORGANIZATIONAL NETWORKS
Computer networks in organizations have evolved over time. Most large organizations have a complex and wide range of different network configurations, operating systems, and strategies. These organizations face the challenge of making these networks work together effectively and securely.
INTERNET TECHNOLOGIES
Many organizations today employ Internet technologies to support effective communication within and between organizations using intranets and extranets.
● An intrenet is a private network within an organization that resembles the Internet. Like the public Internet, intranets use browsers, websites, and web pages. Typical applications include electronic telephone directories, e-mail addresses, employee benefit information, internal job openings, and much more. Employees find surfing their organizational intranets to be as easy and as intuitive as surfing the Internet.
● An extranet is a private network that connects more than one organization. Many organizations use Internet technologies to allow suppliers and others limited access to their networks. The purpose is to increase efficiency and reduce costs. For example, an automobile manufacturer has hundreds of suppliers for the parts that go into making a car. By having access to the car production schedules, suppliers can schedule and deliver parts as they are needed at the assembly plants. In this way, operational efficiency is maintained by both the manufacturer and the suppliers.
NETWORK SECURITY
Large organizations face the challenge of ensuring that only authorized have access to network resources, sometimes from multiple geographic locations or across the Internet. Securing large computer networks requires specialized technology. Three technologies commonly used to ensure network security are firewalls, intrusion detection systems, and virtual private networks.
● A firewall consis of hardware and software that control access to a company's intranet and other internal networks. Most use software or a special computer called a proxy server. All communications between the company's internal networks and the outside world pass through this server. By evaluating the source and the content of each communication, the proxy server decides whether it is safe to let a particular message or file pass into or out of the organization's network.
● Intrusion detection systems (IDS) work with firewalls to protect an organization's network. These systems use sophisticated statistical techniques to analyze all incoming and outgoing network traffic. Using advanced pattern matching and heuristics, an IDS can recognize signs of a network attack and disable access before an intruder can do damage.
● Virtual private networks (VPN) create a secure private connection between a remote user and an organization's internal network. Special VPN protocols create the equivalent of a dedicated line between a user's home or laptop computer and a company server. The connection is heavily encrypted, and, from the perspective of the user, it appears that the workstation is actually located on the corporate network.
Like organizations, end users have security challenges and concerns. We need to be concerned about the privacy of our personal information. In the next chapter, we will discuss personal firewalls and other ways to protect personal privacy and security.
Questions :-
What are Internet technologies?
Compare intranets and extranets.
What is a firewall?
What is a proxy server?
What are intrusion detection systems?
What are virtual private networks?
