Networks and Communication

NETWORKS AND COMMUNICATION

History of Communication• Middle Ages

• Communication and Transportation are linked• Printing Press

• Guttenburg• Telegraph

• Samuel Morse• Telephone

• Alexander Graham Bell• Internet

History of the Internet

• 1950’s XEROX developed Networked computers• 1960’s – ARPANET - Originally a network connecting military

installations to safeguard US military secrets in case of a nuclear attack

• 1970’s – Universities – shared resources• 1980’s – Nerds • 1990’s – Normal People

Physical Methods of Connectivity• Wired

• Category 5 cable – Twisted Pair (4x2)• Coaxial• POTS• FIOS

• Wireless• Satellite TV (Disk Network)• WiFi (802.11 standard)• 3G 4G (Phone Networks)• Infrared (TV Remote control)• Bluetooth

LAN vs WAN• Local Area Network

• IHA ,Small business• Home Networks

• Wide Area Network• Multinational Corporations• Internet

How do computers CommunicateTCP/IP

• Transfer Control Protocol / Internet Protocol • Protocol used for most networks including the Internet• Every computer on a network has its own IP address for

that network.• IP address consists of 4 bytes separated by periods –

192.168.100.63.• Over 4 billion possible addresses.• All Internet IP’s are taken.• 192.168. ? . ? are reserved for LANs

IP addresses – Static vs Dynamic

• Static IP addresses • Some computers never change their IP address.

• 74.125.239.33• 98.139.183.24

• 74.123.155.128• immaculateheartacademy.org = 173.210.1.82

Ntserver121 (LAN) = 192.168.100.2• Dynamic IP addresses – DHCP –

• Dynamic Host Control Configuration• Most Home Routers are given a different available address every time

they connect.

How does a computer get an IP address?

• Every Network device (laptop, smartphone, iPad, etc.) has a unique “MAC” address that never changes• Consists of 6 hexadecimal pairs ( 00 3A BC 14 F3 29 )

• Every LAN has a DHCP server• When a device joins the network it sends a broadcast to

every device it can find:• “Are you a DHCP server? If so, give me an IP address.”

• The DHCP server answers and temporarily gives an IP address (192.168.0.3) to your computer which it then uses to communicate with the network.

Packets of Data• Data arrives in a series of addressed packets.• Only a limited number of bytes (1000 – 4000) are transmitted in each packet.

• Each packet starts with the IP address.• Your network card only accepts packets that are addressed to it.

• Your Internet browser reassembles the file as the packets arrive.

Hubs, Switches and Routers• All three devices send packets over a network• Hub – sends all packets out each port• Switch – learns where each IP addresses lives and only

sends packets down that switch• Router – sends packets onto a different network

How a router works• Your router is given an Internet IP address by your ISP. ie. 173.210.1.82

• Your router gets a LAN IP address for your local network

• Any computer on your home network speaks to its default gateway (the router) using its local IP address. The router then speaks to the Internet, fetches your page and sends it to your computer.

Wired Bandwidth (Speed)• LANs

• 10 mbs (megabits/sec) – Ethernet• Older computers (> 10 years old)

• 100 mbs – Fast Ethernet• 1000 mbs – Gigabit

• All new laptops and computers have a gigabit port for wired connections

WiFi Speeds – 802.11

• 11 mbs (“B”)• 54 mbs (“G”)• 54 mbs (“A”) – used in some businesses• 300 mbs (“N”)

All standards are “backwards compatible”

ISP – Internet Service Providers• Client computers must connect to a computer on the backbone of the Internet.

• Popular ISP’s in Bergen County: • Optimum Online (cable)• Verizon (FIOS)

WAN Bandwidth (Speed)

• FIOS – 50 mbs• Optimum – 20 mbs• 4G – 10 mbs• 3G – 4 mbs

Test your speed at speedtest.net

Browsers• A browser is software on the client computer that is need to convert html text into a web page.

• Most popular – • Google Chrome• MS Internet Explorer• Mozilla Firefox• Apple Safari• Opera

Analyzing a URL

1. Protocol2. Domain Name or server3. Folders4. File Name

http://wb11.com/shows/seinfeld/newman.htm

Protocol determines what type of data is being transmitted

Internet protocols• http: – hypertext transfer protocol – by far the most common

• https: - secure (encrypted)• ftp: - file transfer protocol• mailto: – sends e-mail

http://wb11.com/shows/seinfeld/newman.htm

Domain Name

Name of the computer (server) that holds the desired information

DNS – Domain Name Server• Large database of domain name sends the IP address back to the computer that requested the domain name.

• There are 7 “master” domain controllers on the Internet

• LANs have their own DNS. • Networksolutions.com • Network-tools.com – website that will display names and IP addresses

http://www.yougetsignal.com/tools/visual-tracert/

Domain Name Extensions (7 Original)

• 3 – letter• .com - commercial• .edu – educational (now just colleges)• .org – organization (usually non-profit )• .net – internet related• .gov – US federal government• .mil – military• .int – international databases

Additional Common Extensions• .biz – businesses• .info – information• .name – individuals (john.smith.name)• .pro – professionals (johndoe.med.pro)

Domain Name Extensions• 2 letter extensions• Usually Country names

• .uk .jp .us .au .de .ch .tv• Sometimes State names

• .nj .in .ca

http://www.networksolutions.com/domain-name-registration/popup-extensions.jsp

Subdomains• There is a hierarchy working from the back of the URL:

http://baseball.fantasysports.yahoo.com

Registering your own Domain• You must have someplace to host the site-

• A computer with a static IP address running Web Server software

• It cost about $10 / year to register your name.

• Check availability of your name. • Iha.net iha.com ihahs.org

http://wb11.com/shows/seinfeld/newman.htm

Folders (optional)

Just like your computer, the server is divided into folders or directories.

There may be many. There may be none.

http://wb11.com/shows/seinfeld/newman.htm

File Name

The name of the file to be viewedIf no file is mentioned, the index.htm or default.htm is displayed.

If index.htm or default.htm don’t exist, a listing of all files in the folder is sometimes displayed.

http://173.210.1.82/Outside2/Computer/Hotz/

File names• .html or .htm – hypertext markup language• .asp – active server page• File types that are associated with certain applications will

automatically start that application or run within the browser. • (.ppt, .jpg, .mp3, etc.)

• Go to ihahs.com. Download a form.

Cookies• Cookies are small text files stored on the client computer by many websites.

• They contain info such as account name, preferences, etc.

• In general they are “good” files, saving you time.• Look in c:\documents and settings\user\cookies (Win XP)

Miscellaneous URLs• Open a browser• Go to Yahoo. Click an article.• Do a Google Search.• Check your mail.