The Internet is the largest computernetwork in the world, connecting millions ofcomputers. A network is a group of two ormore computer systems linked together.
• In 1969, the US Department of Defense started a project to allow researchers and military personnel to communicate with each other in an emergency.• The project was called DARPAnet (Defence Advanced Research Projects Agency) and it is the foundation of the Internet.• Later its also called ARPAnet (Advanced Research Projects Agency)
• Throughout the 1970s, what would later become the Internet was developed. While mostly military personnel and scientists used it in its early days, the advent of the World Wide Web in the early 1990s changed all that.• Current amount over 1.9 billion users around the world
• The overall responsibility for managing Internet Protocol address or domain names at upper levels is vested in the Internet Assigned Numbers Authority (IANA), which delegates the actual administration of most functions to other bodies.• At global regional levels, the principal bodies providing allocation and registration services that support the operation of the Internet globally are:• RIPE NCC (Réseaux IP Européens Network Coordination Centre)• ARIN (American Registry for Internet Numbers)• APNIC (Asia Pacific Network Information Centre)• LACNIC (Latin American and Caribbean IP address Regional Registry)• AfriNIC (African Regional Registry for Internet Number Resources)
• Dial-up-connections : speed 56kbps• ISDN : speed 128 Kbps• Broadband ▫ ADSL(Asymmetrical Digital Subscriber Line) Speed 2mbps ▫ Cable : speed 42 Mbps• Lease lines : up to 12mbps• FTTH- Fiber to the Home• Wireless ▫ Wi-Fi ▫ Wi-max ▫ Satellite
As you now know, the Internet is thephysical computer network (computer,monitor, modem, cables, phone lines, etc).
• Tim Berners-Lee, a software engineer, invented the World Wide Web in 1991.• The Web is a system of Internet servers that support specially-formatted documents.• These specially formatted documents are text documents created in HTML, a formatting language. In conjunction with the World Wide Web, your web browser interprets these text documents so they become web pages.• Web pages contain formatted text, graphics, sound, animation, and video, allowing point and click navigation.
• “An address that points to a particular document or other resource on the Internet, used most frequently on the World Wide Web (WWW)”.• A computer user can visit an Internet document by typing its URL into a Web browser or similar application used to access the Internet.• Eg: http://www.infortec-international.com/index.html
Domain names• An internet web site address.• Domain names are used in URLs to identify particular Web pages.• The first-level set of domain names are the top- level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, net and org, and the country code top-level domains (ccTLDs).
• "Interconnection, collection of computers for the purpose of sharing resources & Communication that we can take as a Network”.• Resources we can divide in to three categories, Information such as files & folders, Hardware such as printers and software such as MS office.
• Is a method for communication• File/Data sharing• Sharing of printers and other resources• Can centralize administration and support• Can reduce the cost involved in communication & information gathering
Different types of computer network designs is by their scope or scale.• LAN (Local Area Network)• WAN (Wide Area Network)• MAN (Metropolitan Area Network)• WLAN (Wireless Local Area Network)• PAN(Personal Area Network)• CAN(Campus Area Network)
• LAN (Local Area Network): “A computer network that connect two or more electrical or electronic devices or equipments in a single network”Eg: SLT
• WAN (Wide Area Network): “Connect two or more different networks together” Eg: Internet
• MAN (Metropolitan Area Network):• “A data network designed for a town or city”. In terms of geographic breath, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media.
• Wireless Local Area Network “A LAN based on (Wi-Fi) wireless network technology”
• A type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-peer networks are generally simpler, but they usually do not offer the same performance under heavy loads.
• A network architecture in which each computer or process on the network is either a client or a server. Servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network servers).Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power.
• Intranet: A network based on TCP/IP protocols (an internet) belonging to an organization, usually a corporation, accessible only by the organizations members, employees, or others with authorization. An intranets Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access.
• Extranet: A buzzword that refers to an intranet that is partially accessible to authorized outsiders. Whereas an intranet resides behind a firewall and is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view.
Data Communication• Data Communication is the process of moving data & information from one place to another through a transmission system.
• The communication media is the matter or substance that carries voice or data.• Different types of transmission media are currently in use. All these types can be group two categories as Guided and Unguided media.• The Guided media are follows through physical media and unguided media are those in which is the data is broadcast through air.
• Transmission media Guided Unguided Media(wired) Media(wireless) Twisted pair Radio waves Coaxial cable Microwaves Fiber optics Satellite Infrared Bluetooth
Guided Media:• Cable is the medium through which information usually moves from one network device to another.• There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types.
Twisted pair• Is the common medium• Is mainly used in star topology networks• Cheap and easy to work with• There are several categories available in Twisted pairs ▫ CAT1, CAT2, CAT5, CAT5E
Categories of Unshielded TwistedPair Type UseCategory 1 Voice Only (Telephone Wire)Category 2 Data to 4 Mbps (Local Talk)Category 3 Data to 10 Mbps (Ethernet)Category 4 Data to 20 Mbps (16 Mbps Token Ring)Category 5 Data to 100 Mbps (Fast Ethernet)
Specificati Cable Type Max. length Nodes/seg Advantage on name10BaseT Twisted Pair 100 m 1024 Cheapest system10Base2 Thin Coaxial 185 m 30 No hub needed10Base5 Thick Coaxial 500 m 100 Original cable, now obsolete10BaseF Fiber Optic 2000 m 1024 Best between buildings
Unguided Media• Radio Waves ▫ Omni directional ▫ Suffers from interferences ▫ Use to TV, Radio, Cell phone
• Microwave ▫ Microwaves travel nearly in a straight line ▫ Tall building is a barrier ▫ 100 meter high towers, repeaters for every 80km ▫ Is widely used for mobile phone, television etc.
• Satellite ▫ Used for long distance telephone ▫ Television ▫ Private business network ▫ Mostly used with Microwave ▫ Using in long distance communications ▫ Used for weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System,
• Infrared ▫ Is limited for a small area (eg: for a room) ▫ Walls/barriers will block the signals ▫ Mainly used for TV remote control, IRD port.
• Bluetooth(802.15) ▫ Founding members are Ericsson, IBM, Intel, Nokia and Toshiba. ▫ Short range wireless communication technology. ▫ Used to data synchronization between 2 devices ▫ Is limited for a small area ▫ Mainly used in Mobile phones, digital cameras, headsets, scanners, keyboards, mouse and other devices to connect to a computer.
Network Topologies• Topology refers to the shape of a network, or the networks layout. How different nodes in a network are connected to each other and how they communicate is determined by the networks topology. Topologies are either physical or logical.• BUS, RING, STAR, MESH etc.
Considerations When Choosing aTopology:• Money.• Length of cable needed• Future growth.• Cable type.
• “A Protocol is a set of rules(standards) that governs the communications between computers on a network.”• Most common network protocol is TCP/IP• Eg: http, ftp, smtp, telnet, ssh, https, etc.
Properties of Protocol• Detection of the underlying physical connection (wired or wireless),• Handshaking• How to start and end a message• How to format a message• What to do with corrupted or improperly formatted messages (error correction)• How to detect unexpected loss of the connection, and what to do next• Termination of the session and or connection.
Internetworking Models• When networks fist come in to being, computers could typically communicate with computers from the same manufacturer. In the late 1970s, the Open System Interconnection(OSI) reference model was created by the International Organization for Standardization(ISO) to break this barrier.• It is describes how data and network information are communicated.
• A reference model is a conceptual blue print of how communications should takes place.• These processes divide into logical groups called layers.
Provides the user interface to7. Application communicate to the computer. Eg HTTP ----------------------------------------------------- Presents data to the 7th layer and data6. Presentation translation like encryption, conversion ----------------------------------------------------- Manage presentation layers entities. (keep 5. Session different application data separately) ----------------------------------------------------- Performs error correction before 4. Transport retransmit.[Segments] ----------------------------------------------------- Manages the device addressing.(IP 3. Network addressing) , Routes data. [Packets] ----------------------------------------------------- Combines packets in to bytes and error 2. Data Link detection. [Frames] ----------------------------------------------------- Moves bits between devices(physical 1. Physical connection/cabling, electronic singnals) [Bits]
A network server• A network server is a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet. Network servers typically are configured with additional processing, memory and storage capacity to handle the load of servicing clients. Common types of network servers include: ▫ Web servers ▫ proxy servers ▫ FTP servers ▫ online game servers ▫ Mail servers
Modem• Short for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms.
MAC Address• A MAC address, or Media Access Control address, is a 48- or 64-bit address associated with a network adapter.• While IP addresses are associated with software, MAC addresses are linked to the hardware of network adapters.• For this reason, the MAC address is sometimes called the hardware address, the burned-in address (BIA), or the physical address. MAC addresses are expressed in hexadecimal notation in the following format: 01-23-45-67-89-AB, in the case of a 48-bit address.
• “An identifier for a computer or device on a TCP/IP network”. Networks using the TCP/IP protocol route messages based on the IP address of the destination.• The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255.• For example 188.8.131.52 could be an IP address.
What is an IP addressA way to identify machines on a networkA unique identifier
IP usageUsed to connect to another computerAllows transfers of files and e-mail
IP structureIP addresses consist of four sectionsEach section is 8 bits longEach section can range from 0 to 255Written, for example, 184.108.40.206
IP structureThese four sections represent the machine itself and the network it is onThe network portion is assigned.The host section is determined by the network administrator
IP structure5 Classes of IP address A B C D and EClass A reserved for governmentsClass B reserved for medium companiesClass C reserved for small companies
IP structureClass D are reserved for multicastingClass E are reserved for future use
IP structure Class A begins 1 to 126 Class B begins 128 to 191 Class C begins 192 to 223
Reserved addressesAddresses beginning 127 are reserved for loopback and internal testingxxx.0.0.0 reserved for network addressxxx.255.255.255 reserved for broadcast
IP AddressesIP addresses are: Unique Global and Standardised Essential
• Class A : 220.127.116.11 – 18.104.22.168• Class B : 22.214.171.124 – 126.96.36.199• Class C : 188.8.131.52 – 184.108.40.206• Class D : 224.x.x.x (multicasting & research purposes)• Class E : 240.x.x.x (for future use)
Current Private IP addresses asfollows• Class A 10.0.0.0 through 10.255.255.255• Class B 172.16.0.0 through 172.31.255.255• Class C 192.168.0.0 through 192.168.255.255
• IPv4 addresses have 32 bits in them and so allow a maximum of four billion addresses
• IPv6 stands for Internet Protocol version 6. It is the second version of the Internet Protocol to be used generally across the virtual world.• IPv6 addresses have 128 bits.• IPv6 is the future of Internet addressing, mainly because industry experts believe that they are close to running out of available addresses altogether.
• 128 bits - written as eight 16-bit hex numbers. 5f1b:df00:ce3e:e200:0020:0800:2078:e3e3
How to Determine your IP Address?• Go to the start menu and select Run.... Then type cmd in the box and click OK.• At the C:> prompt type ipconfig. Then press Enter. Your IP address, subnet mask and default gateway will be printed on the window.• If you want more detailed information about your network connection, type ipconfig /all at the prompt. Here you can get additional information about your IP configuration.
• For Domain Name System (or Service or Server), an Internet service that translates domain names into IP addresses.• Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address.Domain IP Addresswww.example.com > 220.127.116.11
DNS has a table of Domain names and IPaddresses. It’s map the domain name with the IPaddress and its route to the particular server.Domain IP Addresswww.yahoo.com 18.104.22.168mail.yahoo.com 22.214.171.124
• Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network.• With dynamic addressing, a device can have a different IP address every time it connects to the network.