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1. What is computer internet?

• A means of connecting a computer to any other computer anywhere in the world via dedicated routers and servers. When two computers are connected over the Internet, they can send and receive all kinds of information such as text, graphics, voice, video, and computer programs.

• The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to link several billion devices worldwide. It is an international network of networks that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks for file sharing and telephony.

2.what are the advantages of internet

3. things needed to access the internet

- needed to access the Internet (1) an ISP, (2) a modem, (3) a Web browser and (4) an e-mail program.

The Internet Service Provider (ISP)Your access to the Internet is through an Internet service provider (ISP), which can be a large company such as America Online or MSN, or any of hundreds of smaller ISPs throughout the country. You are offered unlimited access for a fixed rate per month.

The ModemDepending on the kind of service you have, you will need a unit of hardware called a "modem" for connection. Slow-speed dial-up telephone access uses an analog modem, which may already be installed in your computer. If not, one can be plugged into the USB port.

If you sign up for cable or DSL service, which is from 40 to 100 times faster than telephone dial-up, your provider may send you the appropriate modem, or you can purchase it at your local electronics store. Quite simply, opt for the high-speed service if you can. Dial-up modems are an exercise in extreme patience.

Browsing the WebA Windows PC comes with the Internet Explorer Web browser. The Mac comes with Safari. Windows and Mac users quite often choose a different browser such as Firefox (www.mozilla.org) or Chrome (www.google.com/chrome), which offer additional features and are not as subject to attack by hackers.

The first time you hook up to a new ISP, you may need their assistance to configure the dial-up or networking software in your computer. After that, all you do is launch the browser to "surf the Web."

Sending E-MailAlthough e-mail can be sent and received using your Web browser (see e-mail interfaces), your computer may come with a dedicated e-mail program like the ones found in smartphones. For example, the Mac comes with Mail, while Windows has renamed its free program many times: Outlook Express, Windows Mail, Windows Live Mail and Mail. However, many users prefer Eudora, Thunderbird and other e-mail clients.

The first time you connect to a new ISP, you may need help in configuring your e-mail program to use their mail servers. From then on, you launch the mail program as you would any other application.

Switching ISPs

If you only browse the Web, there is little lost in starting with one ISP and switching to another. However, switching your e-mail address is not like switching your street address. The U.S. Postal Service will forward your letters for a while, but if you close your account with an ISP, they may not be as accommodating. It would be a good idea to find out, if you plan on heavily promoting your e-mail address.

Get Your Own Domain NameThere are two ways around this problem. First is to register your own domain name and use an ISP that supports third-party names. For example, had Alan Freedman, editor of this encyclopedia, wanted to secure the alanfreedman.com domain name, his e-mail address could have been [email protected]. If you have your own domain name and switch ISPs, you keep your e-mail address because it belongs to you.

Use an Alternate E-Mail ProviderA second way to keep your e-mail address is to establish an account with an Internet e-mail provider that you stay with no matter which ISP you use for Internet access. There are sites on and off the Web that provide free e-mail and e-mail forwarding. See how to register a domain name.

4. what is computer communication?

- Computer network is a collection of nodes, where the computing stations (resources) reside. The nodes communicate to each other via communication network. Transmission, and switching accomplishes the course of communications.

-using a computing device while in transit. Mobile computing implies wireless transmission, but wireless transmission does not necessarily imply mobile computing. Fixed wireless applications use satellites, radio systems and lasers to transmit between permanent objects such as buildings and towers.

5. Uses of computer communication

- the purpose of a computer communications network is to allow moving information from one point to another inside the network. The information could be stored on a device, such as a personal computer in the network, it could be generated live outside the network, such as speech, or could be generated by a process on another piece of information, such as automatic sales transactions at the end of a business day. The device does not necessarily have to be a computer; i t c o u l d b e a h a r d d i s k , a c a m e r a o r e v e n a p r i n t e r o n t h e n e t w o r k . D u e t o a l a r g e v a r i e t y o f information to be moved, and due to the fact that each type of information has its own conditions for intelligibility, the computer network has evolved into a highly complex system. Specialized knowledge from many areas of science and engineering goes into the design of networks. It is practically impossible for a single area of science or engineering to be entirely responsible for the design of all the components. Therefore, a study of computer networks branches into many areas as we go up from fundamentals to advanced levels.

6. what is computer network?

- A computer network or data network is a telecommunications network that allows computers to exchange data. In computer networks, networked computing devices pass data to each other along data connections (network links). Data is transferred in the form of packets.

- Network computer devices that originate, route and terminate the data are called network nodes.[1] Nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices are said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other.

7. define the following:

• WAN

A wide area network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, national or international boundaries) using leased telecommunication lines. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable.[1]

• LAN

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a home, school, computer laboratory, or office building, using network media.[1] The defining characteristics of LANs, in contrast to wide area networks (WANs), include their smaller geographic area, and non-inclusion of leased telecommunication lines

• WLAN

A wireless local area network (WLAN) is a wireless distribution method for two or more devices that use high-frequency radio waves and often include an access point to the Internet. A WLAN allows users to move around the coverage area, often a home or small office, while maintaining a network connection.A WLAN is sometimes call a local area wireless network (LAWN).

• MAN

A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN).

8. What are the different network architecture? Define each

- Network architecture is the design of a communications network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as data formats used in its operation.

- Network architectures are sometimes classified into two broad categories:

· client-server architectures,

· peer-to-peer architectures.

In the client-server architectural model, a system is decomposed into client and server processors or processes. Servers provide computational resources (or services), which clients consume. Typically a server provides services to many clients. It is also common for clients to consume services from multiple services. Stated otherwise, there is generally a 1:M relationship between a server and its clients, and it is sometimes the case that there is a 1:M relationship between a client and the servers that it uses. The client-server architectural model supports the separation of functionality based on the service concept.

Client-server architectures are commonly organized into layers referred to as “tiers”.

Tiered Architectures

· Two-tier architectures. The system architecture consists of a data server layer and an application client layer. Data access computation is associated with the data server layer, and the user interface is associated with the client application layer. If most of the application logic is associated with the client application logic, it is sometimes referred to as a “fat client.” If it is associated with the data access server, the application client layer is sometimes referred to as a “thin client.”

· Three-tier architecture. The system architecture consists of data server layer, an application server layer and a client application layer. The application server layer facilitates the separation of application logic from presentation, and promotes distributed processing.

· Multi-tier architecture. The system architecture is a superset of a three-tier architecture, and includes additional layers for data and/or application servers.

Peer-to-Peer Architectures

In a peer-to-peer architecture model, a system is decomposed into computational nodes that have equivalent capabilities and responsibilities. This division is in contrast to a client-server architectural model, where client and server nodes are divided into server and client roles.

An example of a peer-to-peer architecture is a system of intelligent agents that collaborate to collect, filter, and correlate information.

Sometimes layered (“tiered”) and peer-to-peer architectures are combined, where the nodes in particular layers are in peer-to-peer relationships. For example, a multi-tiered architecture might include an enterprise management layer, consisting of peer nodes for such things as network management, event management, database management, Web sever management, and workload balancing.

9. types of networking devices

List of network devices

Connectivity network devices

• Network hub

A hub is a small Network Device. A hub joins multiple computers (or other network devices) together to form a single network segment. On this network segment, all computers can communicate directly with each other. Ethernet hubs are by far the most common type, but hubs for other types of networks such as USB also exist.

A hub includes a series of ports that each accept a network cable, one port is reserved for "uplink" connections to another hub or similar device.

Main Features

■ Operate at Layer 1 devices ( Physical layer ) in the OSI model . ■ Hubs do not read any of the data passing through them and are not aware of their source or destination. ■ Hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network - including the one that originally sent the packet!

Types of Hub

■ Passive Hub ■ Active Hub ■ Intelligent Hub

Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network.

Active hubs on the other hand, do perform this amplification, as does a different type of dedicated network device called a repeater. Some people use the terms concentrator when referring to a passive hub and multiport repeater when referring to an active hub.

Intelligent hubs add extra features to an active hub that are of particular importance to businesses. An intelligent hub typically is stackable (built in such a way that multiple units can be placed one on top of the other to conserve space). It also typically includes remote management capabilities via SNMP and virtual LAN (VLAN) support.

• Network repeater

Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel. Actual network devices that serve as repeaters usually have some other name. Active hubs, for example, are repeaters. Active hubs are sometimes also called " Multiport Repeaters " but more commonly they are just "hubs." Other types of "passive hubs" are not repeaters. In Wi-Fi, access points function as repeaters only when operating in so-called " Repeater mode ."

• Network bridge

A Network Bridge reads the outermost section of data on the data packet, to tell where the message is going.only the outermost hardware address of the packet.

Main Features

■ 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.■ Bridge cannot read IP addresses .■ Bridge can read the ethernet data which gives the hardware address of the destination 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:

■ 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.

■ Source route bridging - The source computer provides path information inside the packet. This is used on Token Ring networks.

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• Network router

Network Router is a network device with interfaces in multiple networks whose task is to copy packets from one network to another. Router gives path to data packet to destination. Routers provide connectivity inside enterprises, between enterprises and the Internet, and within an Internet Service Provider (ISP).

Main Features

■ Operates at Layer 3 (Network Layer) of the OSI Model. ■ Router works with Static Routing manully configure by Network Administrator.■ Router works with Dynamic Routing which routers calculate automatically by different methods. ■ Router stores calculate path in his Routing Table.■ The network router will then use its routing table to make intelligent decisions about which packets to copy to which of its interfaces .■ The router will use this information to create a routing table.■ This process is known as routing.

Types of Router

■ Wired Router ■ Wireless Router

Types of Router by Placement

■ Internal Routers (Access)Routers are used to connect two LAN's.

■ Edge Routers Router used to connect LAN with WAN, means at the end of your network.

■ Core Routers Core Router provides a stepdown backbone , interconnecting the distribution routers from multiple building of a campus ( LAN), or Large enterprise Location (WAN).

■ Security Routers for Interconnecting ISPs.

■ Inter-provider Border Routers considered as part of the overall security strategy, firewall & VPN.

• Network switch

Network Switch is a small hardware device that joins multiple computers together within one local area network (LAN).

Main Features

■ Network Switches operate at layer two (Data Link Layer) of the OSI model . ■ Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. ■ Unlike hubs, Switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. ■ By delivering messages only to the connected device intended. ■ Switch conserves network bandwidth and offers generally better performance than a hub. ■ Switch supports different bandwidth either 10/100 Mbps Fast Ethernet or Gigabit Ethernet (10/100/1000) standards. ■Switches can be connected to each other, a so-called daisy chaining method to add progressively larger number of devices to a LAN. ■ Switch Reduce the Collision Domain.

Types of Switches by Forms

■ Rack Mounted Switches.■ Chassis Switches.■ Catalyst Switches.■ DIN Rail Switches.

Types of Switches by Configuration

Unmanaged Switches

■ Switches are not configured. ■ Commonly used in home networks and small businesses.■ Switches does not need to be monitored or configured using external software applications.■ They are easy to set up and require only cable connections.

Managed Switches

■ Can be configured with SNMP.

■ Console Cable.■ secure shell. ■ This types of Switches will be configured. Check cisco for Managed Switches

Types of Managed Switches

Smart Managed Switches

■ Operates in Managed and Unmanaged.■ Configure virtual LANs ports. ■ Set up for trunking with other Switches. ■ Fast LANs to support gigabit data transfer.

Enterprise Managed Switches

■ Fully Managed. ■ Support web interface.■ Support SNMP agent.■ Support command-line interface.■ Restore, Backup, Modify & Display Configurations.

Types of Switches by Placement or Function

■ Access Switches. ■ Distribution Switches. ■ Core Switches.

• cdsu/dsu device

A CSU/DSU (Channel Service Unit/Data Service Unit) is a hardware device about the size of an external modem that converts a digital data frame from the communications technology used on a local area network (LAN) into a frame appropriate to a wide-area network (WAN) and vice versa.

■ The Channel Service Unit (CSU) receives and transmits signals from and to the WAN line and provides a barrier for electrical interference from either side of the unit. ■ The CSU can also echo loopback signals from the phone company for testing purposes. ■ The Data Service Unit (DSU) manages line control, and converts input and output between RS-232C, RS-449, or V.xx frames from the LAN and the time-division multiplexed (TDM) DSX frames on the T-1 line. ■ The DSU manages timing errors and signal regeneration. ■ The DSU provides a modem-like interface between the computer as Data Terminal Equipment (DTE) and the CSU.

Hybrid network devices

• Protocol Conversion

■ A protocol converter is a mechanism that changes a standard protocol by one device to a protocol that can be used to facilitate the function of another device. Protocol converters also are referred to as protocol translators. Process.

■ Protocol converters are essentially software installed on routers that are used to convert the data rate, or speed at which data is transmitted, and existing protocols in one network to the protocols of the other network that is sending or receiving the data. Protocol converters, much like a language translator, translate messages, or data streams, between networks to enable both networks to easily interpret the data. Applications.

■ Protocol converter software is used in a variety of industries for applications such as building and process automation. Protocol converters also are used for substation automation, or a system for managing and controlling equipment in an electric power system

• Brouter

■ A Network brouter is a network device that works as a bridge and as a router. Network brouter (pronounced BRAU-tuhr or sometimes BEE-rau-tuhr) is a network bridge and a router combined in a single product. A bridge is a device that connects one local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). ■ If a data unit on one LAN is intended for a destination on an interconnected LAN, the bridge forwards the data unit to that LAN; otherwise, it passes it along on the same LAN. A bridge usually offers only one path to a given interconnected LAN. A router connects a network to one or more other networks that are usually part of a wide area network (WAN) and may offer a number of paths out to destinations on those networks. ■A router therefore needs to have more information than a bridge about the interconnected networks. It consults a routing table for this information. Since a given outgoing data unit or packet from a computer may be intended for an address on the local network, on an interconnected LAN, or the wide area network, it makes sense to have a single unit that examines all data units and forwards them appropriately.

Hardware or software components

• Proxy

Proxy: In communications, a proxy is something that acts as a server, but when given requests from clients, acts itself as a client to the real servers. Analogy: Consider talking to somebody who speaks a foreign language through a translator. You talk to the translator, who receives your statements, then regenerates something else completely to the other end. The translator serves as your proxy. Key point: The communication terminates at the proxy. In other words, the proxy doesn't forward data so much as it tears it completely apart.

For example, an HTTP proxy doesn't forward every request sent through it. Instead, it first examines if it already has the requested web page in its cache. If so, then it returns that page without sending another request to the destination server. Because proxies completely terminate the communication channel, they are considered a more secure firewall technology than packet filters, because they dramatically increase the isolation between the networks. Key point: You will occasionally be scanned for proxies.

• Network Firwall

A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. There are several types of firewall techniques: ■ Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing. ■ Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. ■ Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking. ■ Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses. In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.