networking.ppt

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Survey of Information

Technology: Meeting 6

CITA 113

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Welcome to Survey of IT!

Class Agenda

• _{Review Lab Materials}

• _{Discuss Technology Reports}

• _{Data Communications}

Basics

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Lab Review

• _{Are there questions about the Lab?}

• _{Keep practicing the commands}

• _{Try to use the applications on the website:}

– _{Web server} – _{FTP server}

– _{Hash Calculator} – _Sniffer

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Technology Reports

• _Questions

• _{Let’s walk through an example}

• _{http://sites.google.com/a/aubih.edu.ba/cita-113/course-materials}

• _{Remember to think about the business and}

the technical aspects of your topic

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Data Communications

• _{Analog signals are continuous variables that}

change over time

– _{Noise – analog signals are very prone to noise}

– _{Cabling technologies respond with shielding and}

twisting

– _{Modulation is the process of varying a periodic}

waveform to convey a message

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Data Communications

• _{Parameters of a}

sine wave or carrier signal

– _{Frequency - pitch} – _{Amplitude -}

volume

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Data Communications

• _{Digital Signals capture the essence of Analog}

signals with a process called sampling.

• _{By sampling or taking snapshots of the analog}

signal at specific intervals, it is possible to

reconstruct the signal with just those numbers

• _{The advantage of digital signals is that they}

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Data Communications

• _{Nyquist Theorem: to accurately reproduce an}

analog signal with a digital signal, the analog signal must be sampled at a minimum of 2x the highest frequency of the analog signal

• _{Example: voice channels carry frequencies}

between (0 and 4 kHz)

• _{In order to digitize this signal, we must sample}

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Data Communications

• _{These are the absolute basics}

• _{This type of information is essential for people}

who wish to work in networking or telecommunications

• _{We are only scratching the surface with some}

basic vocabulary

• _{For those who wish to learn more, please}

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General Communication Terms

• _{General Communication}

– _Synchronous:_{sender and receiver are active at the same}

time

• _{e.g., telephone call, instant messaging (IM)}

– _{Asynchronous:}_{sending and receiving occur at different}

times

• e.g., e-mail

– _{Broadcast communication}_{(or multicast): single sender and}

many receivers

– _{Point-to-point communication:}_{single sender and single}

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Client / Server Computing

• Server is the computer that stores the web page – Web server, file server, mail server

• _Client_{is the computer that accesses the web page}

• _{When you click link, your computer enters client/server}

relationship with web server

• _{Once the page is sent to you, the client/server relationship}

ends

• _{Server can form many brief relationships so it can serve many}

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Networking

• _{OSI – Open Systems Interconnection Model is an}

abstract description for layered communications and computer network protocol design.

• _{The OSI Reference Model consists of 7 layers}

– Application

– _Presentation – Session

– _Transport – Network

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Networking

• _{OSI Model was not widely implemented because of}

TCP/IP

• _{TCP/IP has four layers}

– _Application _HTTP

– _Transport _TCP

– _Internet _IP

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Networking: Application Layer

• _{HTTP – Hypertext Transfer Protocol (Port 80)} • _{SMTP – Simple Mail Transfer Protocol (Port 25)} • _{FTP – File Transfer Protocol (Port 21)}

• _{DNS – Domain Name System (Port 53)} • _{SSH – Secure Shell (Port 22)}

• _{SFTP – Secure File Transfer Protocol (Port 22)}

• _{A network scanner like nmap sweeps machines on a network}

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Networking: Transport Layer

• _{TCP – Transmission Control Protocol is a}

connection-oriented protocol that provides a reliable byte stream

– _{Data arrives in order}

– _{Data has minimal errors} – _{Duplicate data is discarded} – _{Lost packets are resent}

– _{Includes Congestion control}

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Networking: Transport Layer

• _{UDP – User Datagram Protocol is a}

connectionless protocol that provides no error checking. UDP is a best effort delivery system.

• _{Example: Mail}

• _{Applications that use UDP are responsible for}

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Networking: Internet Layer

• _{IP – Internet Protocol performs the basic task}

of moving information or packets from the source to the destination

• _{ICMP – Internet Control Message Protocol is}

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Networking: Link Layer

• _{The link layer provides the low level}

connection to which a host is attached

• _{Ethernet is an example of a link layer protocol}

• _{The link layer is the closest layer to the}

physical layer which consists of the physical media used to construct a network

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Networking: DNS

• The Domain Name System (DNS) translates the human-readable hostnames into IP addresses

• _{Internet host knows the IP address of its nearest DNS server,}

a computer that keeps a list of host/domain names and corresponding IP addresses

• _{When you use a hostname to send information, your}

computer asks the DNS server to look up the IP address

• _{If the DNS server doesn't know the IP address, it asks a}_Root

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Networking: DNS

• _Domain_{is a related group of networked computers} • _{Top-level domains appear in the last part of domain}

name:

.edu educational institutions .org organizations

.net networks .mil military

.gov government agencies

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Networking: DHCP

• _{DHCP – Dynamic Host Configuration Protocol}

assigns IP addresses to workstations on a network.

• _{This is a more manageable strategy for}

networks like LANs.

• _{We do not need to assign IP addresses}

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Networking Organization

• _{LAN – Local Area Network}

• _Ethernet

• _{WAN – Wide Area Network}

• _{T1 line}

• _{Asynchronous Transfer Mode} • _{Frame Relay}

• _Routing