Internet and LAN Technology

1. Internet and LAN Technology Chapter 5

2. Why install networks? • Share resources such as printers or storage space • Reduce costs • Enable people to share documents easily • Allow people to work together regardless of geography or time

3. Disadvantages to Networks • Susceptible to attacks and unauthorized access • Widespread network problems can cause loss of productivity • Access to additional resources (Internet) can also lead to decrease in worker productivity

4. Different ways to classify networks • Geographical scope-how much area does it serve? • Organizational structure-what is the hierarchy of devices attached? • Physical typology-how is it arranged or what is the “shape” of the network? • Network lines-what cables or substitute is responsible for moving data around the network? • Bandwidth-how much data can it carry? • Protocols used-does it use TCP/IP or something else?

5. Geographical • PAN-personal area network (a computer and devices within 30 feet usuallly a computer and a wireless device such as a printer) • LAN-large area network (a small business or part of a larger network, i.e. the library LAN or a home network) • MAN-metropolitan area network covers a city or metropolitan area such as ISPs or cable modem networks • WAN-wide are networks that share information across great distances such as nationwide bank networks

6. Organizational • Client/server where one server provides services to one or many clients • Peer to peer networks where all computers are equal and there isn’t a server doing all of the work…everyone shares jobs.

7. Members of the Network • The items in a network can consist of: • a server • client or workstation • networked peripheral such as a printer • network devices which help broadcast and boost signals on network

8. Network Hardware • In addition to the computers and shared peripherals on the internet, there are

9. Physical Topologies - Star • Server is centrally located • All traffic must travel through central computer • Can be problematic if central computer breaks down • Central point can be a HUB with a repeater which broadcasts and boosts the signal across the network

10. Ring Topology • Connects all devices in a circle • Uses less cable than star topology • Can be dangerous if one computer fails • Infrequently used

11. Bus Topology • Uses common backbone to connect devices • Connected together like a “daisy chain” • Works best with few dozen computers • Trouble if backbone fails

12. Mesh Topology • Connects each device to many others • Data can take many different paths in case one goes down • Original plans for internet were based on mesh topology

13. Tree Topology • Combines star and bus networks • Attaches star configurations to a bus backbone • Many schools and businesses use this plan

14. Networking Hardware • In addition to Hubs and repeaters, many networks need hardware to connect different networks together • Bridges connect similar networks • Gateways and routers join networks that are different

15. More Networking Hardware • Devices either need to be linked together with wires or through wireless technology • Wires come in three flavors: • Twisted pairs-refers to the twisted pairs of copper wires usually used in LANs such as computer labs and dorms • Coaxial cable has a copper wire encase in insulation usually used with cable modems…cable TV too! • Fiber optic cable has strands of glass that conduct data using miniature lasers used for higher traffic areas such as backbones and some larger business and campus networks

16. Wireless Networks • Generally operate of RF signals (radio frequency) or microwaves • Hardware needed includes a transceiver which operates as both a transmitter and receiver • Radio and microwaves can’t bend around earth so satellites are needed • Satellite has a transponder which receives the signal, amplifies it, and retransmits • Infrared can also transfer data for short distances with a clear line of sight

17. What is bandwidth? • Bandwidth is the transmission capacity of a communications usually measured in bits per second • Higher bandwidth options such as DSL and cable access are considered broadband connections • Lower bandwidth connections are considered narrowband

18. How does data travel on a network? • Protocols handle the various tasks such as dividing the information into packets and shipping the to the right location • Protocols can regulate traffic in a number of ways: • Simplex is data travelling in one direction only (radio or TV) • Half duplex allows traffic in both directions but only one at a time (walkie talkies) • Full duplex allows traffic in both directions at the same time (telephone conversation)

19. More on Local Area Networks (LAN) • Controlled by standards so everyone’s LAN works in the same way • Can use ARCnet, Token Ring or FDDI (Fiber distributed data interconnect) • Many use Ethernet because it is fast andinexpensive

20. More on Ethernet • Ethernet technology simultaneously broadcasts data to all devices on the network and is only accepted by the device it is addressed to • Ethernet is generally cabled with twisted pair or fiber optic cables • Generally requires an ethernet card which acts as the computer network interface card

21. Wireless Technology • Wi-Fi (wireless fidelity) refers to networking standards for the most popular wireless network technology • Wi-Fi hotspots are wireless access points in stores and restaurants such as Starbucks and Borders • Wi-fi requires an access point which acts as a hub. • A wi-fi card is required to connect your computer to the wireless network • Some wi-fi hotspots are free, others require service with companies such as T-Mobile • Bluetooth is a wi-fi alternative but generally only carries signals for short distances.

22. Problems with Wireless Networks • Slower transmission speeds than Ethernet • Susceptible to interference from similar devices such as cordless phones • Security • War driving or LAN jacking where people use wireless signals to access networks and possibly data on that network • Easy to intercept so data must be transmitted in an encrypted format (WEP)

23. HomePNA and HomePLC networks • HomePNA uses existing telephone cables and a special network interface card (NIC) to transfer data in a home network • HomePLC uses a special NIC card and the electrical outlets in your home to transfer data

24. The Internet--History • When the Russians launched Sputnik the US felt they were falling behind and created a network called ARPANet to connect scientists to allow them to share info • In the early 1990s new programs were developed to make the internet easier to use • Today, over 500 million users use the internet transferring over 100 trillion bytes per week

25. Internet Structure • The internet is not “owned” by anyone • Network Service Providers (NSP) such as AT&T and Sprint maintain the backbones and routers of the Internet • Network Access Points (NAP) connect backbones from different providers • Large ISPs connect directly to the backbones and smaller ISPs generally connect to a larger ISP

26. Internet Protocols • TCP/IP is used for dividing the info into packets and then sending it on its way • HTTP is used to exchange info via web pages • FTP transfers files between computers • SMTP, POP, and IMAP are all email protocols

27. IP Addresses • In order for info to travel the net it need to know where to go and uses IP addresses. • IP numbers looks something like this: 123.34.46.255 • When you logon to surf the internet, your ISP assigns your computer a dynamic IP address that will be different next time you log on • Sometimes you need to assign one IP address to a machine for a long time so you give it a static IP address

28. Domain Names • Instead of remembering those IP addresses, we substitute names such as tarleton.edu because they’re easy to remember and type • These name substitutions for IP addresses are called domain names • The last part of the domain name such as .com or .edu designates the top-level domain and indicates what type of site it may be

29. Some Top Level Domains • .com – commerce site • .edu – education site • .net – generally used for ISP but has expanded • .gov – for US government • .mil – for US military • .org – for non-profit organizations • .au, .jp,.uk generally are geographical designations for countries such as Australia, Japan and the United Kingdon

30. More on Domain Names • Domain servers sit out on the internet and lookup the corresponding IP address for the domain name you’ve entered and sends you on your way • You may want to purchase your own domain name if you are going to operate a business or large website • You must choose a domain name that is not already being used and pay a fee

31. Voice Over IP • VoIP allows you to speak into your computer’s microphone and have it delivered via the internet to another computer, allowing for conversations • Many times can be used to eliminate long distance fees but the quality is not always the best

32. How does dial-up actually work? • Your modem places a regular telephone call using POTS (plain old telephone system) to transfer data. • Your ISP “answers” your modem’s phone call and a router sends it out to the Internet • Your modem (which comes from modulation and demodulation) is responsible for changing audio signals into digital signals and then back again • Modems can be measured in baud rate but more commonly now are measured in capacity such as kbps • Even though much of the phone system in this country is digital, you still need a modem because the local cable from your house to the telephone company is still designed to carry analog signals

33. What is accelerated dial-up? • Data is not actually sent faster than normal dial-up, just uses some tricks • Server compresses data even more at the ISP before it is delivered to the client • Server also caches or temporarily stores copies of popular pages so the download only goes from the ISP to the customer and not out on the web • Does not improve file download time such as music and video files which are already compressed • Generally costs anywhere from $11-$20/month

34. Cable modem connections • The cable from the cable company has the potential to deliver TV signals, accept data, and send data all on the same wire • Cable internet subscribers are all connected to a neighborhood network with the cable company routing your data onto the internet • You need a special cable modem that translates the cable data into data that your computer understands that is generally then connected to your computer via ethernet cable • Note that the more customers that join the network, the potential for slower connections grow as everyone share the same bandwidth

35. More on DSL • DSL is an always-on high speed connection that uses standard phone lines • Can simultaneously carry voice and digital data • Speed varies and signal degrades over distance • Requires a DSL modem