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Networking & the
Internet
What is a Network?
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A computer network allows computers to communicate
with many other computers and to share resources and
information.
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Connection Method
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Wired
◊
Twisted Pair Cables
◊
Fiber Optics, ...
Wireless
◊
Wireless LANs
◊
Bluetooth
◊
Cellular System, ...
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Scale
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Local Area Network (LAN)
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Wide Area Network (WAN)
◊
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a computer network covering a small physical area, like a
home, office, or small group of buildings
a data communications network that covers a relatively
broad geographic area
...
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Network Topology
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physical interconnections of the elements (links, nodes,
etc.) of a computer network
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What is Internet
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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
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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)
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IPv6 – e.g. ::ffff:192.0.2.128
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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
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A port is an application-specific or process-specific
software construct serving as a communications
endpoint
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Uniform Resource Locator (URL)
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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
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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
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HTTP(Hypertext Transfer Protocol)
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FTP(File Transfer Protocol)
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SMTP(Simple Mail Transfer Protocol)
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POP3(Post Office Protocol) / IMAP(Internet Message
Access Protocol)
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HTTPS/SFTP/SMTPS/POP3S/IMAPS (Secure)
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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)
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PCs & Servers
◊
Network card
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Cables
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Hubs
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Switches
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Routers
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Basic Hardware Components(cont'd)
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Clients(PCs) & Servers
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Network card
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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)
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Hubs
◊
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When a packet arrives at one port(connected cable),
it is copied unmodified to all ports of the hub for
transmission
Switches
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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)
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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
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Ping google.com -t → Ctrl-C
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Nslookup google.com
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Tracert google.com (linux: traceroute)
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Ipconfig (linux: ifconfig)
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Whois
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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?
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