Download networking - Department of Computer Engineering

Networking & the
Internet
What is a Computer Network?
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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:
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Departments to share hardware
Information to be shared
Communication between organizations
Decentralization of data processing functions
Connection Method
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While Transmission speed/range matters
Wired
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Coaxial Cable : widely used for cable television systems, office buildings,
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Twisted Pair Cables : the most widely used medium for
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Fiber Optics : Thin filaments of glass fiber wrapped in a protective layer.
and other worksites for local area networks - copper or aluminum wire wrapped
with insulating layer
telecommunication - a kind of ordinary telephone wires, for voice and data
transmission
It transmits light which can travel over long distance and higher bandwidths
Wireless
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Cellular and PCS System : Radio communications technologies
Wireless LANs : high-frequency radio technology similar to digital cellular-
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Bluetooth : A short range wireless technology. Operate at approx. 1Mbps
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enable communication between multiple devices in a limited area
with range from 10 to 100 meters
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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
Metropolitan Area Network (MAN)
Virtual Private Network(VPN)
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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)
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Physical interconnections of the elements
(links, nodes, etc.) of a computer network
Physical : Mapping of these links and nodes in a graph which results in a geometrical shape
Logical : 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
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What is Internet
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NOW Internet is NOT owned by anyone
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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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.

These Rules are called : HTTP(HyperText Transfer Protocol)
WWW is somehow software of Internet!
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
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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
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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
subnet
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Which computer
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.)
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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 processspecific 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)
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Assigned names and Domains.
BUT totally Internet is NOT owned by anyone
ICANN Organization created Domains
 A Domain Implies the nature of the
organization that owns a computer

.com commercial
.org nonprofit organizations
.gov governmental
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Uniform Resource Locator (URL)
rather than strange IP address
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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.
Protocol
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Web service
Domain
http://www.sharif.ir
ftp://cabinet.ce.sharif.edu/ : for receiving files from
Cabinet
+ What is DNS Server
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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)
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)
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Telnet host port (e.g. telnet ce.sharif.edu 22)
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Know about TCP and UDP protocols too
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Basic Hardware Components
Building blocks of networks (PCs, Servers, Hubs, Switches, Routers, Cables, etc.)
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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
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Network card
Cables
Hubs
Switches
Routers
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Basic Hardware Components(cont.)
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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.)
Data are transmitted in form of Packets. Each packet has a header.
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Routers
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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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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. Each node receives the packet but
uses it only if the MAC and IP address is its.
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. Sends the
packet directly to the designated IP.
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Networking Commands
Windows Command line/Linux Terminal
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Ipconfig (linux: ifconfig)
Ping google.com : -t → Ctrl-C
Nslookup google.com : query DNS
Tracert google.com (linux: traceroute)
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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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