Networking & the Internet

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What is a Network?

□ A computer network allows computers to communicate with many other computers and to share resources and information.

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Connection Method

□ Wired

◊ Twisted Pair Cables

◊ Fiber Optics, ...

□ Wireless

◊ Wireless LANs

◊ Bluetooth

◊ Cellular System, ...

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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

□ ...

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Network Topology

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

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What is Internet

□ It 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 by copper wires, fiber-optic cables, wireless connections, and other technologies

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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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Internet Protocol(cont'd)

□ 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

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Uniform Resource Locator (URL)

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

◊ http://ce.sharif.ir

◊ ftp://cabinet.ce.sharif.edu/

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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)

□ POP3(Post Office Protocol) / 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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Basic Hardware Components

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'd)

□ 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'd)

□ Hubs

◊ When a packet arrives at one port(connected cable), it is copied unmodified to all ports of the hub for transmission

□ 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

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Basic Hardware Components(cont'd)

□ Routers

◊ A router is a networking device that 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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Networking Commands

□ Ping google.com -t → Ctrl-C

□ Nslookup google.com

□ Tracert google.com (linux: traceroute)

□ Ipconfig (linux: ifconfig)

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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?