Networking & the Internet

What is a Computer Network?

□ A collection of computers and peripherals connected by communication links which allows computers to communicate with many other computers and to share resources and information.

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Purposes:

□Departments to share hardware□Information to be shared□Communication between organizations□Decentralization of data processing

functions

Connection Method While Transmission

speed/range matters

□ Wired◊ Coaxial Cable : widely used for cable television systems, office

buildings, and other worksites for local area networks - copper or aluminum wire wrapped with insulating layer

◊ Twisted Pair Cables : the most widely used medium for telecommunication - a kind of ordinary telephone wires, for voice and data transmission

◊ Fiber Optics : Thin filaments of glass fiber wrapped in a protective layer. It transmits light which can travel over long distance and higher bandwidths

□ Wireless◊ Cellular and PCS System : Radio communications

technologies◊ Wireless LANs : high-frequency radio technology similar to

digital cellular-enable communication between multiple devices in a limited area

◊ Bluetooth : A short range wireless technology. Operate at approx. 1Mbps with range from 10 to 100 meters

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Scale□ Local Area Network (LAN)

◊ a computer network covering a small physical area, like a home, office, or small group of buildings

□ Wide Area Network (WAN)◊ a data communications network that covers a relatively

broad geographic area

□ Metropolitan Area Network (MAN)□ Virtual Private Network(VPN)

□ Additional software layer (overlay) on top of an existing larger network for the purpose of creating a private scope of computer communications or providing a secure extension of a private network into an insecure network such as the Internet.

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Network Topology(physical and logical)

□ Physical interconnections of the elements (links, nodes, etc.) of a computer network

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Physical : Mapping of these links and nodes in a graph which results in a geometrical shapeLogical : Mapping of the data flows between the nodes

Link: means of connecting one location to another for the purpose of transmitting and receiving digital info.Node : a connection point

What is Internet

□ ARPANET : In 1968 the US department of defense launched a project to electronically connect government scientist at university throughout the United states, in order to share information easily, quickly and securely.(app. 500 universities connected)

□ ARPANET was renamed INTERNET and …□ INTERNET is a network of networks that consists of millions of

private and public, academic, business, and government networks of local to global scope that are linked .

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NOW Internet is NOT owned by anyone

WWW(World Wide Web) The first major Improvement to the

internet came in 1989 when WWW was created by Tim Berners-Lee

To uniform presentation of information on all Internet Computers.

WWW is a way information is organized on the Internet.

Specifies RULES for Finding and Displaying information on all Internet computers.

WWW is somehow software of Internet!These Rules are called : HTTP(HyperText Transfer Protocol)

Web(world wide web) Browser(How to find and

display info. )

No need to learn strange commands to find info on the Internet.

a software application for retrieving, presenting, and traversing information resources on the World Wide Web

The first web browser : Mosaic

Addressing System(identification is needed )

Is needed for both nodes in a network(connected to Internet) and also information(sites and pages)

Must be unique

Internet Protocol(IP)

Provides addressing systems (IP addresses) for computers on the Internet

□ IP Version 4 (IPv4) – e.g. 192.168.0.2◊ the initial version used on the first

generation of the today's Internet and is still in dominant use. It was designed to address up to ~4.3 billion (109) Internet hosts. However, the explosive growth of the Internet has led to IPv4 address exhaustion which is estimated to enter its final stage in approximately 2011.

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subnetWhich computer

Internet Protocol(cont.)

□ IPv6 – e.g. ::ffff:192.0.2.128◊ A new protocol version, IPv6, was developed

in the mid 1990s which provides vastly larger addressing capabilities and more efficient routing of Internet traffic. IPv6 is currently in commercial deployment phase around the world

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Port

□ A port is an application-specific or process-specific software construct serving as a communications endpoint . Is somehow the way(where) to connect to an IP(for a computer).

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DHCP servers

Can have static and dynamic IP +LAN and Wireless Adaptors. 127.0.0.1 is you (Localhost)

Assigned names and Domains. ICANN Organization created

Domains A Domain Implies the nature of the

organization that owns a computer

BUT totally Internet is NOT owned by anyone

.com commercial.org nonprofit organizations

.gov governmental…

Uniform Resource Locator (URL)rather than strange IP address

□ A string of characters used to specify where an identified resource is available and the mechanism for retrieving it. e.g.

◊ http://www.sharif.ir

◊ ftp://cabinet.ce.sharif.edu/ : for receiving files from Cabinet

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Protocol Web service Domain

+ What is DNS Server

Protocol

□ In computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication

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Famous Protocols

□ HTTP(Hypertext Transfer Protocol)□ FTP(File Transfer Protocol)□ SMTP(Simple Mail Transfer Protocol)-for

sending emails□ POP3(Post Office Protocol)-for receiving emails

/ IMAP(Internet Message Access Protocol)□ HTTPS/SFTP/SMTPS/POP3S/IMAPS (Secure)

□ Telnet host port (e.g. telnet ce.sharif.edu 22)

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Know about TCP and UDP protocols too

Basic Hardware ComponentsBuilding blocks of networks (PCs, Servers, Hubs, Switches, Routers, Cables, etc.)

All networks are made up of basic hardware building blocks to interconnect network nodes.

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Basic Hardware Components(Nodes & Building Blocks)

□ PCs & Servers◊ Network card

□ Cables□ Hubs□ Switches□ Routers

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Basic Hardware Components(cont.)

□ Clients(PCs) & Servers◊ Network card

◊ a Media Access Control address (MAC address) is a unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number

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Basic Hardware Components(cont.)

□ Routers◊ A router is a networking device that receives and forwards

packets between networks using information in protocol headers and forwarding tables to determine the best next router for each packet

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Data are transmitted in form of Packets. Each packet has a header.

Basic Hardware Components(cont'd)

□ Hubs◊ When a packet arrives at one port(connected

cable), it is copied unmodified to all ports of the hub for transmission. Each node receives the packet but uses it only if the MAC and IP address is its.

□ Switches◊ A network switch is a device that forwards and

filters chunk of data communication between ports based on the MAC addresses in the packets. Sends the packet directly to the designated IP.

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Networking CommandsWindows Command line/Linux Terminal

□ Ipconfig (linux: ifconfig)□ Ping google.com : -t → Ctrl-C□ Nslookup google.com : query DNS□ Tracert google.com (linux: traceroute)

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Whois

□ WHOIS (pronounced as the phrase who is) is a query/response protocol that is widely used for querying databases in order to determine the registrant or assignee of Internet resources, such as a domain name, an IP address block, or an autonomous system number.

□ Whois sharif.edu

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Any Questions?