Introduction to Computers

1. Introduction to Computers

2. A little history • The Internet has been around since: 1991 1984 1977 1969 1961 1956 • The Internet was largely unnoticed for years • Mostly for military and education use before 1995 • Two innovations caused it to explode in the mid-90s • Tim Berners-Lee created the World Wide Web in 1991 • Two students at the University of Illinois wrote the first graphical web browser, Mosaic, in 1993 • Internet & World Wide Web are not synonymous • The Web is a subset of the Internet

3. What is the internet? • The Internet is a communications infrastructure • Using a common communications protocol • Linking networks and servers worldwide • The Internet communication protocol is TCP/IP(Transmission Control Protocol/Internet Protocol) • The goal: send data from one point to another • It’s a highly decentralized network • Internet servers are found everywhere… worldwide • Data can take many paths to a destination, automatically routing around failing components

4. What is a Protocol? • All forms of communication follow a set of rules • You understand these words because they follow the rules of the English language • If this were in Chinese, it would be gibberish to you • Source and recipient must follow the same rules • Computers must agree upon a set of rules for communication, just like people do • There are many different sets of rules for digital communication • Protocol is just a set of rules for communication

5. The internet Backbone • The Internet backbone is a network of very high-speed and high-capacity data lines • The backbone is like the Interstate Highway System • Consider driving from Waynesville to Nashville • First task is to find the quickest way to I-40 • The slowest part of the trip is getting to I-40 • Can only get on I-40 at an interchange • Once on I-40, it’s a non-stop trip at high speed • Similarly, internet data must get to the backbone

6. How does data get to the backbone? • Individuals contract with an ISP(Internet Service Provider) to gain access to the Internet • ISP connects you to the Internet by providing: • A means to connect you to a local point of presence • A fiber optic line connects local point of presence to backbone at a network access point (NAP) • Connection to ISP is like the street leading out of your neighborhood… it takes you to US-276 • The fiber optic line is like US-276… it takes you to an interchange with I-40

7. Connecting to Your ISP • Currently four major means to connect at home • Dial-up – uses voice grade standard phone line • Cable – uses cable television coaxial connection • DSL – uses digital signal on a standard phone line • Mobile broadband – uses cell phone system • Dial-up speed at 56Kbps is no longer practical • Other connection types are 100-1,000 times faster • ISP connection requires some type of modem • Converts signal for transmission on the medium

8. Cable connections • Advantages: • Very fast: Most users see speeds of 20-50 Mbps1 which vary depending on provider and other factors • Often far slower than maximum advertised by ISP’s • Disadvantages • Many rural areas have no access to cable service • You share bandwidth with neighbors so heavy users in your area may slow your connection 1 From www.dslreports.com

9. DSL connections • Advantages: • Fast: Most users see speeds of 5-25 Mbps1 which vary depending on provider and other factors • Often far slower than maximum advertised by ISP’s • Possible disadvantages • Connection speed slows as distance from switching station increases • Generally slower than cable, but not always • Unavailable to many, too far from switching station 1From www.dslreports.com

10. Mobile broadband connections • Advantages: • Fast: 4G speeds of 15-20 Mbps1 • 3G speeds much slower at 2-4 Mbps1 • Internet access most anywhere “on the go” • Most smart phones will create a hot spot that lets others use Internet by connecting to the hot spot • Disadvantages • Many need wireless data as well as home internet • Be wary of data caps on your data plan • Very slow or no connection in remote areas 1From www.dslreports.com

11. Data Caps • A bandwidth cap may be imposed on heavy users to balance usage & increase ISP revenue • A hard cap requires additional payment when exceeding the cap • A soft cap allows continued access to data but at significantly reduced connection speeds • Wireless hot spots often have very limited caps • Makes it difficult to use wireless plan as home plan

12. Other types of connections • Satellite • Similar speeds as DSL, but more costly • The best and often only option for high-speed access in remote areas • Severe rain or snow can cause signal interruption

13. Wireless Internet access • Cable and DSL are always wired connections • But can get wireless access to cable & DSL at home by installing a wireless network • Router needed for a home wireless network • Most routers function as both wired or wireless • If using wired access, network port is used to connect • A router also allows a single home internet connection to be shared among multiple users and devices • Mobile broadband is always a wireless signal • A wireless router is built into most mobile devices

14. a router provides a firewall • A router also provides a firewall for security • A router hides your computer behind a firewall • Without one, your computer is directly accessible to hackers on the Internet • With one, hackers see your router on the Internet but not the computers hiding behind the router • A wireless router should require a password • If not, neighbors or passersby can “hitchhike” on your wireless signal & use your internet connection

15. Data is sent to an IP address • Every device connected to the Internet has a unique number called an IP address • An IP address consists of 4 sets of numbers, each separated by a period, ranging from 0 to 255 • Why 0 to 255? An IP address consists of 4 bytes! • A typical IP address might be 204.84.169.23 • 247.271.13.87 is not a valid IP address. Why? • An IP address is like the address of your home • It’s unique! It’s where your mail is delivered.

16. A trip on the internet • Request the MSN web site in your web browser • Browser sends a packet to the MSN server • The packet contains: • IP address of the web site being requested (destination) • IP address of browser submitting the request (source) • Routers are the “traffic cops” of the internet • Look at destination IP address at data line intersections • Steer data toward the destination IP address • Each router successively steers the packet closer to its destination • Packet eventually arrives at destination server

17. A trip on the internet • MSN server returns a web page by • Sending packets of data to requesting computer • Several small packets are sent containing: • IP address of computer making request (destination) • IP address of MSN server (source) • Data that makes up that web page • Routers use IP address to steer packet along the Internet communication links back to your browser • Your computer receives several packets of data • Packets reassembled and web page displayed

18. Who uses IP addresses? • Instead of an IP address, you key in msn.com when requesting the MSN web site • Msn.com is a domain name • Domain names automatically map to an IP address • Domain names much easier to use and remember • Try it yourself • Click on the web address http://216.58.216.164 • Surprise! It’s the same Web page as www.google.com • While both take you to the same web page www.google.com is far easier to remember

19. Local area networks & the internet • Large organizations do not provide an Internet connection for each and every computer • Businesses and educational institutions like HCC use a local area network to tie computers together • Computers on the network all share a single, high-speed, large bandwidth Internet connection • LAN’s are a more sophisticated version of the personal area networks (PANs) found in homes

20. Other Protocols on the internet • TCP/IP is the overarching Internet protocol that determines how data is transmitted • Other protocols dictate subsets of the Internet • World Wide Web - Hypertext Transfer Protocol (HTTP) • Receive Email - Post Office Protocol (POP3) • Send Email - Simple Mail Transfer Protocol (SMTP) • Send or Receive Files - File Transfer Protocol (FTP) • Voice Conversations - Voice Over IP (VoIP) • Control a remote computer - Telnet