Introduction to networkComputer network or network is collection of computers, printers and other devices connected with each other through a connection medium and other suitable peripherals.
The purpose of the connection is mainly transfer or share data, share of resources such as printers, applications etc. The connected computers and devices may be in the same building or can be Located in different part of the city, country or world. Appropriate connection medium, peripherals, software enable computers to transfer, and receive data such as text, pictures, video, sound through email, file transfer (ftp-file transfer protocol), web pages(http -hyper text transfer protocol) etc from one computer to another computer in the network securely. History of networkingThe first idea of computer networking was developed by J.C.
R Licklider, a computer scientist in 1962. He was later appointed by U.S. Department of Defence at their research project called ARPA (Advanced Research projects agency).
ARPA was funding research for developing computer network to MIT. In 1966 first ARPAnet plan for packet switched network unveiled and in 1969 first official computer network was built between University of California Lon Angels (UCLA), Stanford Research Institute (SRA), University of California Santa Barbara (UCSB) and University of Utah. The first message was sent from UCLA to SRI. In 1973 Arpanet goes global; University College London and few other European organizations joined the network.
In 1982 standardized Internet technology protocols TCP/IP (transmission control protocol and Internet protocol) were developed which enable internetworking among single sets of networks efficiently and commercial Internet services started to evolve. In 1991 World Wide Web was developed and Internet became popular and expanded rapidly including dramatic rise of email users, text based discussion forum etc. Advantages and Disadvantages of using networksAdvantagesDisadvantagesShare of Expensive Resources:Printer, fax machines, modem and other connected resources can be shared. File and application sharing:Major advantage of network. User can access any file remotely from his computer to another computer with appropriate security measures.
Applications also can be used without having installed in every computers of the network. Cost saving: Sharing application by installing its network version saves cost of many copies of individual application. Sharing devices such as printer, fax etc saves cost. Secured: Files and application are password protected in network, which means only authorised person can access it.
It is more secured than traditional file system. Speed:Message, Data, file can be transferred almost instantly to any part of the world. Easy management:Software can be installed in server, also managing and troubleshooting can be performed in server. This eliminates the need of installing and managing software in hundreds of computers in an organization. System failure:Servers or connection faults stop accessing files or data. This can lead to loss of data and resources.
Security issue: data and file can be theft by hacker. This is the main drawback of computer networking. Computer viruses, spyware attack can lead to system failure, data and resources loss. Expensive Equipment:Networking equipments are expensive compare to traditional file system and communication method. Answer of criterion P1 (b)Remote AccessRemote access means accessing and using any file or application from a computer to another computer connected in the network. Both computers may located in same building or thousands miles away.
Generally files or applications are accessed over Internet, intranet or LAN with an authentication process which determine the level of access of the user. For example, a sales staff of Barclays bank accessing loan authorisation database from his home through Internet. IntranetsIntranet is a private computer network between an organization using Internet protocol and tools such and HTTP, file transfer application to share information or application within the organizations. Typically, authorised users of an organization gain access files or applications in Intranet through a web page with their user name and password.
Staffs of the organizations also maintain internal communication in Intranet via email. Email is accessed via an email client such as Microsoft outlook, Eudora etc. this email clients use POP3 (post office protocol) and SMTP (simple mail transfer protocol) for receiving and sending mail. When an email is sent, the email client connect to the server after providing valid user name and password and verify the address of the recipient, if the address is correct it leaves the email on the server. When recipient checks his email, his email client connects to the POP3 server. POP3 server also requires a user name and password.
After logging in email client bring the copy of email message to user’s computer and generally delete the message from the server. User than read or search email message in his computer. InternetInternet is the largest network in the world. It interconnects world wide networks of organisations, billions of computer users in one single network using Internet protocol (TCP/IP). Internet is a global data communication system with the largest resources of information and services such as World Wide Web, Email, file transfer protocol etc.
Email in Internet works using SMTP, POP3, and IMAP. Users use email software or web page email program such as yahoo, hotmail etc for sending and receiving mail. This program connect user to the server for sending and receiving email similarly discussed in Intranet section. In Internet SMTP server has communication between other SMTP servers in Internet. When an email sent SMTP server check the address and send the mail to recipient email server.
Similarly when recipient checks the email using POP3 it does the same as discussed earlier. IMAP (Internet mail access protocol) is more advanced protocol which provides better features than POP3. In IMAP email is kept in the server. User can organise email in different folders and they stays in the server. It enables users accessing mail from any computer any time as email resides in the server.
LANs (Local Area Networks)Network in a limited geographical area such a home, office, school in same building or in different building within short distance. Each connected computer or devices are called node. Currently most wired LAN connects using Ethernet technology. Fig: LAN WAN (Wide Area Network)WAN connects networks over a large geographical area such city, state or over countries. It uses routers and combination of communication channels such as public communication link, air waves, etc. Fig: WAN MANs (Metropolitan area network)MANs connect two or more LAN within a same city or town.
It normally connects two or more branch of an organisation within the same city using routers, switch, and hub. It often connects through public communication link. Fig: MANs Networked applicationAn application software which can be shared on a network from connected computer by an authorise user. Networked application is normally installed on server of a network, and authorise users of that network (LAN/WAN) can access and work with that application from their workstation. This application utilizes Internet or other network hardware infrastructure to perform useful functions.
Answer of Criterion P2Description of Devices/ Hardware/ softwareNumber of unit and unit pricePricePerformanceSecurityUtilityWorkstation:COMPAQ Presario CQ5305UK-m Desktop PC with Monitor CPU- Intel Core2 Duo 2.1 GHz OS; Windows 7.0 15 £359 £5385 20 work station is connected using netgear switch provides a full duplex very high 100 mbps data transmission speed over a 100baseTX connection with UTP CAT6 cable. Dell powerEdge server with Windows server 2008 R2 standard edition gives efficient and secured file sharing and print server functions, remote access, application sharing. Windows server 2008 R2 edition has an increased efficiency and service with windows 7.0 client’s operating system.
Microsoft Windows 2008 server R2 edition network OS have enhanced security features to prevent server form hackers, and gives a solid dependable environment for networking. Kaspersky Business space security software provides real time protection to the server and work stations against harmful virus, spyware, and other harmful internet treats. its constantly monitor and scan all open or modified files and application. It isolate any infected workstation on the network to prevent the server from being infected and clean the workstation. This LAN will enable the users of this organization share file and information whenever they needed from their work station.
They are able to print any document from their printer using network printer. Sharing printers and applications saves company’s cost and increased productivity. Server:DELL™ PowerEdge™ T110 CPU: Intel Core i3 2.93 GHz Net OS: Windows Server 2008 R2 standard edition + 20 CALs (client access license) 1 £1359 Switch:NETGEAR JGS524 Gigabit Switch -24 ports 1 £237 Cables:200 m – UTP – ( CAT 6 ) £42 Connector:Network connector – RJ-45 2 pack ( 25 in a pack) £4 each £8 UPS:(UPS provides uninterrupted power supply to the server and prevent server failure due to an event of power cut).
APC Smart-UPS 2200VA 1 £588 Security Software:Kaspersky Business Space Security for 20 workstation and 1 windows 2008 server. 1 year subscribtion £587 Answer of Criterion P3Overview of network Operating systemA network operation system is a set of software that control and manages computers, printers and other devices connected in a network. it allows computers to share file and devices connected in the network. It is installed on a computer called server which centrally maintain the network. There are many Net OS from different vendors in the market.
Among them most popular are Windows NT, Windows Server from Microsoft, Unix Novel Netware from Novel Inc. Apple Share from Apple Regardless of vendors all Net OS works by providing following functions and services to the client and server File and print sharing Accounts administrations for users Security Some basic features of a network operating system are-Add , remove and modify users, workstations, devices in the network Add, Remove and configure application software to be used and shared by the users on the network Control and manage users and their access Allow and control users to share data, application and devices such as printer, fax etc. Allows users to transfer data from one computer to another computer in the network Mange security and privilege. Security Implications of network useThe computer connected in a network is vulnerable to intruder such as hackers and intrusion programs. Also virus, malware, spyware, worms on the network attack the system. Those attacks may results valuable information theft, system failure and data loss or even irrecoverable damages to the system.
Intruder gain access and control of the system by using some methods as described below- Back door and remote administered program Spam email Email virus Trojan Horse program Hidden files To keep the system secure there are some security measure should be taken. System needs to be password protected, password should be changed regularly and shouldn’t be disclosed to anyone System should have latest software update. Antivirus, firewall, anti spyware should be installed and should be updated regularly. Suspicious email shouldn’t be opened. File or program shouldn’t be opened from unknown sources Disable hidden file extension Disconnect from network when pc is not in use.
Software Licensing IssuesSoftware licensing is an agreement between user and software manufacturer. software using conditions and distribution limitations. Software is intellectual property and protected by copyright laws. When a software is obtained from any sources users enters into some legal bindings set out by the manufacturer or distributor on how this software may be used. These includes but not limited to numbers of users, distribution rights and limitation, resale rights and limitations, reproduction and modification limitations etc. Most of the commercial software comes with license when purchased off the selves.
Some software license is bundled with specific hardware or new system, call OEM License. There are different categories of software license- Propitiatory: Software own by a company or individuals and not free or open sourced. Redistribution or reproduction is generally not allowed or limited Freeware and Open source software: Generally free and permits user to modify, reproduce and distribute according to their own preference Shareware, Trial ware: is propitiatory software but provided free to user to use for a limited period of time for testing. Reproduction is not permitted but distribution may be permitted with certain conditions Constrains on Capacity and performanceEvery Network has limited capacity of transferring and receiving data. this capacity (bandwidth) depends on the several factors such as device and medium used, price etc. each users of a network share the bandwidth and everyone is effecting the performance of the network.
For example, if user sends a very large video or animation file to another computer in the network which most likely to use most of the capacity of the network, which will make the network very slow to other users. Thus performance is affected, in some cases packet or data losses may occur due to overloading of network. When a packet is lost, retransmission of packets attempted and this cause delay of receiving and sending data. Answer of Criterion P5Relationship of Various Protocols, devices of network with OSI-7 layered modelApplication(Layer 7)Http-Hyper text Transfer Protocol Telnet FTP- File transfer protocol Presentation(Layer 6Jpeg, Gif, avi, mov, mpeg etc Session(Layer 5)NetBios Names, RPC, AppleTalk, Winsock Transport(Layer 4)TCP, UDP,SPX Network(Layer 3)IP, IPX, AppleTalk DDP Router Data link(Layer 2)Frame Relay, HDLC, ATM, IEEE 802.3/802.
2/802.5 Ethernet Switch, Bridge Physical layer(Layer 1)Ethernet, 802.3, 802.5, Token ring Repeater, Hub Ethernet: Most commonly used protocol for LAN.
Ethernet fits into the Data link layer and Physical layer of OSI model and deal with the hardware of the network. it define about the type of media, connectors, characteristics, use of wires, shape of connectors etc. HDLC: High-level Data link Control used for point-to-point WAN link. TCP/IP: Transmission Control Protocol/ Internet protocol.
These pair of protocol allows one network to communicate with another by creating logical address, segmentation of large data into small packets, data encapsulation, error recovery etc. UDP: User datagram Protocol. Transmit data from one host to another without establishing a prior connection. It simply transmits data without knowing if the data is transmitted correctly thus unreliable. ICMP: Internet Control Message Protocol carry error recovery data, control data such as ‘destination unreachable’, ‘echo request’, etc between two host Http: Hyper text transfer protocol, FTP: File transfer protocol SMTP: Simple mail transfer protocol
