06.01.04 TIE29D - © Ritva Laiho 1

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06.01.04 TIE29D - © Ritva Laiho 1

  1. 1. TIE29F – Operation and practice of an Information Network Part 2: WAN = Additional information
  2. 2. Choosing a network <ul><li>Requirement </li></ul><ul><ul><ul><li>What is the network used for? </li></ul></ul></ul><ul><ul><ul><li>Which solutions meet the requirements? </li></ul></ul></ul><ul><li>Performance </li></ul><ul><ul><ul><li>Does the network meet the required performance </li></ul></ul></ul><ul><ul><ul><li>Speed and reliability </li></ul></ul></ul><ul><li>Knowhow </li></ul><ul><ul><ul><li>Is the technology to modern? Is necessary training available? </li></ul></ul></ul><ul><ul><ul><li>Too many partners? </li></ul></ul></ul><ul><li>Security </li></ul><ul><ul><ul><li>Is the solution secure enough? </li></ul></ul></ul><ul><li>Standards </li></ul><ul><ul><ul><li>Does the solution meet standards? </li></ul></ul></ul>
  3. 3. Choosing a network <ul><li>Costs </li></ul><ul><ul><li>Design, purchase, installation and training </li></ul></ul><ul><ul><ul><li>Both hardware and software </li></ul></ul></ul><ul><ul><ul><li>The price of the hardware is often only a small part of the total costs. </li></ul></ul></ul><ul><ul><li>Costs during the who life span </li></ul></ul><ul><ul><ul><li>What is the estimated life time of the network? </li></ul></ul></ul><ul><ul><ul><li>Cost of maintenance is usually underestimated </li></ul></ul></ul><ul><ul><li>Quality and costs must be in balance </li></ul></ul><ul><ul><ul><li>Users’ needs and the budget are usually far a part </li></ul></ul></ul><ul><ul><ul><li>Find out the real requirements </li></ul></ul></ul><ul><ul><ul><li>Solve the necessary requirements without go bancrupt. </li></ul></ul></ul>
  4. 4. Contents <ul><li>1) Connecting LANs </li></ul><ul><ul><li>Properties of different alternatives </li></ul></ul><ul><ul><ul><li>Leased line, data transmission networks </li></ul></ul></ul><ul><ul><li>Some technology </li></ul></ul><ul><ul><ul><li>structure and operation of an digital phone network </li></ul></ul></ul><ul><ul><ul><li>terminology: circuit switched and packet switched etc. </li></ul></ul></ul><ul><li>2) Working at home </li></ul><ul><ul><li>Properties of different alternatives </li></ul></ul><ul><ul><ul><li>ISDN, modem, GSM, kaapeliverkko, ADSL, wireless, power line networking, satellites </li></ul></ul></ul><ul><ul><li>Some technology </li></ul></ul><ul><ul><ul><li>Modem basics etc. </li></ul></ul></ul>
  5. 5. Contents - 1 <ul><li>Connecting LANs: </li></ul><ul><li>(Micro wave link) </li></ul><ul><li>Leased line </li></ul><ul><ul><ul><li>(Expensive). F ixed monthly rent </li></ul></ul></ul><ul><ul><ul><li>Security is generally good, even if the telephone company may tap the wire. </li></ul></ul></ul><ul><li>Data networks </li></ul><ul><ul><li>Internet </li></ul></ul><ul><ul><ul><li>Open. Combination of many different technologies. Connection through a ISP. </li></ul></ul></ul><ul><ul><ul><li>Inexpensive. No guaranteed speed. Not secure. Need encryption and firewalls to make secure. </li></ul></ul></ul><ul><ul><li>Data network </li></ul></ul><ul><ul><ul><li>Closed system. Service bought from one tele operator. (Datanet, LanLink) </li></ul></ul></ul><ul><li>Note! Small enterprises can use same methods as are used at home. </li></ul>
  6. 6. Digital telephone network ... <ul><li>Many names: </li></ul><ul><li>YPV = Y leinen p uhelin v erkko </li></ul><ul><li>PSTN = P ublic S witched T elephone N etwork </li></ul><ul><li>POTS = P lain O ld T elephone S ervice </li></ul>
  7. 7. Digital telephone network ... Exchange Exchange Exchange Exchange Exchange Exchange Exchange local telephone exchanges (concentrators) <ul><li>Customer line </li></ul><ul><li>(“last mile”, local loop) </li></ul><ul><li>Analog </li></ul><ul><li>max 56 kbit/s </li></ul><ul><li>Digital (ISDN) </li></ul><ul><li>max 2 * 64 kbit/s </li></ul>155 Mbit/s (STM-1) 34 Mbit/s (E3) Connections between exchanges are always digital. Speed of connection: 2,5 Gbit/s (STM-16)
  8. 8. Digital telephone network ... <ul><li>Even if speech is an analog signal connections between telephone exchanges use digital signals. </li></ul><ul><ul><li>Digital technology is cheaper and faster. </li></ul></ul><ul><ul><li>Error rate is smaller and data may be encrypted . </li></ul></ul><ul><li>Analog signal must be digitized : </li></ul><ul><ul><li>Analog line: digitized in the closest exchange/concentrator </li></ul></ul><ul><ul><li>Digital line: ISDN terminal adapter (analog phone) or in ISDN phone </li></ul></ul>exchange exchange
  9. 9. Digital telephone network ... <ul><li>Analog-digital conversion: </li></ul><ul><ul><li>Analog signal is sampled at regular intervals. </li></ul></ul><ul><ul><li>A sample tells the amplitude of the signal at the sample time. </li></ul></ul><ul><ul><li>Original signal can be regenerated from samples with digital-analog conversion. </li></ul></ul>time 0 127 -127 -127  sample  127, each sample is 8 bits
  10. 10. Digital telephone network ... Sample rate is 8000 per second . Each sample is 8 bits . Transmission speed is 8000 * 8 bit/s = 64 000 bps CODEC = co de/ dec ode sample sample … . 01101100 01011011 . . . . CODEC
  11. 11. Digital telephone network ... <ul><li>Coding method </li></ul><ul><ul><ul><li>PCM pulse code modulation </li></ul></ul></ul><ul><ul><ul><li>Nyquist theory: sample rate must be at least twice the signal frequency </li></ul></ul></ul><ul><ul><ul><li>Frequency of normal human speech is between 300-3400 Hz </li></ul></ul></ul><ul><ul><ul><li>A sample rate 8000 1/s is selected. Upper limit of the frequency range is therefore 4000 Hz. Higher frequencies are filtered out. </li></ul></ul></ul>
  12. 12. Digital telephone network ... <ul><ul><li>In old telephone networks one cable was reserved for every call. </li></ul></ul><ul><ul><li>Its not possible to have a cable for each call in today’s telephone networks, because the number of calls have increased rapidly. </li></ul></ul>1 2 3 circuit switching         
  13. 13. Digital telephone network ... <ul><li>In modern telephone netwoks </li></ul><ul><ul><li>Trunk cables between telephone exchanges carry several calls by time division multiplexing (channeling) . </li></ul></ul><ul><ul><li>Each call is given a time slice. Time slices are transmitted alternately in the cable. Number of time slices is constant (for example 32 in E1 cable). </li></ul></ul><ul><ul><li>Network is still circuit switched. Each call gets a virtual circuit. </li></ul></ul><ul><ul><li>The speed of one virtual circuit (or channel) is 64 kbps. </li></ul></ul>
  14. 14. Digital telephone network ... <ul><li>Time division multiplexing </li></ul><ul><li>One cable can carry many calls. Samples of each call are sent alternately. </li></ul><ul><li>For example in ISDN two calls are multiplexed in a cable. </li></ul>1/8000 s 1/8000 second One sample is send in 1/16000 s multiplexer 8-bit sample
  15. 15. Digital telephone network ... <ul><li>Trunk cable types and speeds : </li></ul><ul><ul><li>E1 = 2 Mbps or 32 voice channels, (USA: T1 = 1,5 Mbps ) </li></ul></ul><ul><ul><li>E3 = 34 Mbps or c. 500 voice channels(USA: T3 = 45 Mbps ) </li></ul></ul><ul><ul><li>OC-3/STM-1 = 155 Mbps or c. 2 400 voice channels </li></ul></ul><ul><ul><li>OC-12/STM-4 = 622 Mbps or c. 9 600 voice channels </li></ul></ul><ul><ul><li>OC-48/STM-16 = 2,5 Gbps or c. 38 400 voice channels </li></ul></ul><ul><ul><li>OC-192/STM-64 = 10 Gbps or c. 153 600 voice channels . </li></ul></ul>
  16. 16. Digital telephone network ... <ul><li>Sending data in telephone network </li></ul><ul><li>Each voice channel can carry 64 kbps data. </li></ul><ul><li>Several channels can be combined to achieve higher speeds. </li></ul><ul><ul><li>For example ISDN connection uses two channels which can be combined together. This way the speed can be increased to 128 kbps. </li></ul></ul>
  17. 17. Digital telephone network ... <ul><li>Sending data in telephone network </li></ul><ul><ul><li>Leased line: </li></ul></ul><ul><ul><li>Telephone companies lease channels from trunk cables. </li></ul></ul><ul><ul><li>Connection is permanent. </li></ul></ul><ul><ul><li>Fixed monthly charge. </li></ul></ul><ul><ul><li>High speed </li></ul></ul><ul><ul><li>Cheap if traffic is high </li></ul></ul>
  18. 18. Connecting LANs with a leased line Exchange Exchange Exchange Exchange Telephone network Exchange E1 E1 Helsinki Turku Necessary number of channels leased from trunk cables Structure Usually the whole cable to the closest exchange is leased for the connection
  19. 19. Connecting LANs with a leased line <ul><li>Telephone company leases a point-to-point connection between LANs. </li></ul><ul><ul><li>The cable to the closest telephone exchange (or concentrator) is normally dedicated to this connection. Often a new cable must be installed. </li></ul></ul><ul><ul><li>Trunk cables between exchanges have normally a very high capacity. Only required number of channels is leased. </li></ul></ul><ul><ul><ul><li>For example 2 Mbps => 32 voice channels (32 * 64 kbps = 2048 kbps) </li></ul></ul></ul>
  20. 20. <ul><li>Costs </li></ul><ul><ul><li>Initial costs depend on the speed. </li></ul></ul><ul><ul><li>Monthly charge depends on the speed and distance between networks. The amount of traffic does not effect. </li></ul></ul>Connecting LANs with a leased line
  21. 21. <ul><li>Security </li></ul><ul><li>Leased line is relatively secure if the telephone company can be trusted. </li></ul><ul><ul><li>Security can be improved by using encryption </li></ul></ul><ul><li>Who can use leased lines? </li></ul><ul><li>Medium to large companies. Cost effective if network traffic is high. </li></ul><ul><li>Leased lines are also used to connect to the Internet. </li></ul>Connecting LANs with a leased line
  22. 22. Connecting LANs with a leased line Lan need a router and a cable modem to connect to a leased line. E1-cable
  23. 23. Contents - 1 <ul><li>Connecting LANs: </li></ul><ul><li>Leased line </li></ul><ul><ul><ul><li>Expensive. Fixed monthly rent </li></ul></ul></ul><ul><ul><ul><li>Security is generally good, even if the telephone company may tap the wire. </li></ul></ul></ul><ul><li>Data transmission networks </li></ul><ul><ul><li>Internet </li></ul></ul><ul><ul><ul><li>Open. Combination of many different technologies. Connection through a ISP. </li></ul></ul></ul><ul><ul><ul><li>Inexpensive. No guaranted speed. Not secure. Need encryption and firewalls to make secure. </li></ul></ul></ul><ul><ul><li>Data network </li></ul></ul><ul><ul><ul><li>Closed system. Service bought from one tele operator. (Datanet, LanLink) </li></ul></ul></ul><ul><li>Note! Small enterprises can use same methods as are used at home. </li></ul>
  24. 24. Data transmission network <ul><li>Data transmission networks are designed to data transmission not for speech </li></ul><ul><ul><li>Connection times are longer in data transmission. </li></ul></ul><ul><ul><li>Capacity of the telephone network is waisted, because data is not sent continuously. </li></ul></ul><ul><ul><li>Small delays are acceptable in data transmission. </li></ul></ul><ul><li>Data transmission networks are based on packet switching. </li></ul><ul><ul><li>Better use of capacity </li></ul></ul><ul><li>Charge is based on amount of trasfered data and speed. </li></ul>
  25. 25. Data transmission networks <ul><li>1) X.25 (traditional packet network) </li></ul><ul><ul><li>Originally meant for terminal connections </li></ul></ul><ul><ul><li>Max 64 kbps </li></ul></ul><ul><ul><li>Not recommended any more. </li></ul></ul><ul><li>2) Frame Relay </li></ul><ul><ul><li>Meant for connecting LANs </li></ul></ul><ul><ul><li>Max 2 Mbps </li></ul></ul><ul><ul><li>Rather expensive </li></ul></ul><ul><ul><li>Internet more popular </li></ul></ul><ul><li>3) ATM </li></ul><ul><ul><li>Designed to be a universal network (video, voice, data) </li></ul></ul><ul><ul><li>Speed: 155 Mbps, 622 Mbps, 2.5 Gbps, … </li></ul></ul><ul><ul><li>Used as LAN and Internet backbone </li></ul></ul><ul><ul><li>Complicated and expensive </li></ul></ul>
  26. 26. Open and closed data network <ul><li>Specialized data transmission networks, like Frame Relay, are based on one technology. They are closed networks owned by one operator. </li></ul><ul><li>Internet is an open network which uses many different technologies. </li></ul>
  27. 27. Terminology <ul><li>Circuit switched ... </li></ul><ul><li>Telephone network is base on circuit switching and time division multiplexing </li></ul><ul><li>For each call a fixed amount of capacity is reserved from the network. </li></ul><ul><li>A call reserves the capacity until the call is ended. </li></ul>Piirikytkentä = circuit switching
  28. 28. Circuit switching A virtual circuit is made between terminals. Each call gets a time slice. In the picture every fourth time slice is reserved for the green connection. 2 1 6 5 4 7 3 data Terminology switch
  29. 29. Terminology <ul><li>Packet switched </li></ul><ul><li>Data is split to packets. Each packet contains several bytes. </li></ul><ul><li>Packets of different connections are carried in the same cable. </li></ul><ul><ul><li>If only one connection is sending, it can use the whole capacity. </li></ul></ul><ul><ul><li>Each packet contains information of the connection. </li></ul></ul>Pakettikytkentä = packet switching
  30. 30. Packet switched - A connection reserves capacity only when sending data. 2 1 6 5 4 7 3 data address Terminology A B C B B B B B B B B B B C B C C C C C
  31. 31. Connecting LANs through the Internet firewall ISP Internet ISP VPN (encrypted connection between LANs) Helsinki Turku Connection with a leased line or ADSL No fixed route or speed.
  32. 32. Connecting LANs through the Internet <ul><li>Internet </li></ul><ul><ul><li>Internet is a packet switching data transmission network. </li></ul></ul><ul><ul><li>Internet uses many different technologies. </li></ul></ul><ul><ul><li>Internet is made of networks connected with routers. </li></ul></ul><ul><ul><li>No guaranteed speed! </li></ul></ul><ul><ul><ul><li>The connection to the Internet may be fast (for example 2 Mbps). Still speed between LANs may be only a few kbps. </li></ul></ul></ul>
  33. 33. Connecting LANs through the Internet <ul><li>Enterprises connect to the network of an ISP ( Internet Service Provider ): </li></ul><ul><ul><li>Many different ways to connect. Most popular are: </li></ul></ul><ul><ul><ul><li>Medium and large enterprises: leased line (2, 34, 155 Mbps) </li></ul></ul></ul><ul><ul><ul><li>Small enterprises: ADSL </li></ul></ul></ul><ul><ul><li>Different sites can use different technology and speed. </li></ul></ul>
  34. 34. Connecting LANs through the Internet <ul><li>Security </li></ul><ul><ul><li>Internet is on open network. It is not secure: </li></ul></ul><ul><ul><ul><ul><li>It’s relatively easy to listen and even to change any transmission. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Network can be attacked through Internet. </li></ul></ul></ul></ul><ul><ul><li>Improving security: </li></ul></ul><ul><ul><ul><ul><li>Firewall prevents unauthorized connections </li></ul></ul></ul></ul><ul><ul><ul><ul><li>VPN (Virtual Private Network) creates a secure connection between to LANs. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Virus protection, user authentication, encrypted mail… </li></ul></ul></ul></ul>
  35. 35. Connecting LANs through the Internet <ul><li>Costs </li></ul><ul><ul><li>Internet is cheaper than an dedicated connection between netwoks. </li></ul></ul><ul><ul><ul><li>Internet connection is needed anyway. </li></ul></ul></ul><ul><ul><li>Costs include : </li></ul></ul><ul><ul><ul><li>Connection to the Internet. Leased line or ADSL. Fixed monthly charge. </li></ul></ul></ul><ul><ul><ul><li>Traffic based charge for using Internet. </li></ul></ul></ul><ul><ul><ul><li>Additional services: email, web hosting, domain name registration. </li></ul></ul></ul>
  36. 36. Working at home: <ul><li>ISDN </li></ul><ul><li>Analog modem </li></ul><ul><li>GSM </li></ul><ul><li>ADSL </li></ul><ul><li>Cable modem </li></ul><ul><li>Wireless connection </li></ul><ul><li>Power line </li></ul><ul><li>Satellite </li></ul>Connection through ISP Contents - 2 Direct connection to enterprise network or through ISP ISDN
  37. 37. ISDN ... <ul><li>What does ISDN mean ;-) </li></ul><ul><li>ISDN = It S till D oes N othing </li></ul><ul><li>ISDN = I S ee D ollars N ow </li></ul><ul><li>ISDN = I ntegrated S ervices D igital N etwork </li></ul>
  38. 38. ISDN <ul><li>ISDN developed in the beginning of 1990’s </li></ul><ul><ul><li>Because telephone network is nowadays digital, it seems natural to have also digital subscriber lines. </li></ul></ul><ul><ul><li>ISDN was not popular at first. It was too expensive and didn’t offer any real advantages to ordinary users. </li></ul></ul><ul><ul><li>ISDN became popular only when Internet came to homes. </li></ul></ul><ul><ul><ul><li>ISDN is not recommended any more. New solutions like ADSL are better and prices are almost the same. </li></ul></ul></ul><ul><ul><ul><li>First ISDN was to expensive. Now it’s to slow. </li></ul></ul></ul>
  39. 39. … ISDN <ul><li>BRI - Basic Rate Interface </li></ul><ul><ul><li>2 B-channels and 1 D-channel </li></ul></ul><ul><ul><li>Ordinary telephone line </li></ul></ul><ul><ul><li>used as a home connection </li></ul></ul><ul><li>PRI - Primary Rate Interface </li></ul><ul><ul><li>30 B-channels and 2 D-channels </li></ul></ul><ul><ul><li>Need an E1 cable </li></ul></ul><ul><ul><li>Used to connect telephone exchanges and modem pools. </li></ul></ul>There are two types of standars connections B-channel = voice channel D-channel = control channel PRI B-CHANNEL D-CHANNEL BRI B-CHANNEL D-CHANNEL B-CHANNEL
  40. 40. ISDN, BRI B channel B channel 2B+D All channels in one cable ISDN Terminal adapter D channel: controls the connection. Terminal adapter converts analog signal to digital. Analog connection can be converted to ISDN.
  41. 41. ISDN, BRI <ul><li>ISDN uses time division multiplexing to send all channel in the same cable </li></ul><ul><li>2 B channels </li></ul><ul><ul><li>Two simultaneous connections possible. For example a phone call and Interner connection. </li></ul></ul><ul><ul><li>Both channels can be used together for higher speed (128 kbps) </li></ul></ul><ul><li>1 D channel </li></ul><ul><ul><li>D channel is meant to carry signalling and control information </li></ul></ul><ul><ul><li>D channel is always open. In some countries D channel can be used to carry data. </li></ul></ul>
  42. 42. Working at home: <ul><li>ISDN </li></ul><ul><li>Analog modem </li></ul><ul><li>GSM </li></ul><ul><li>ADSL </li></ul><ul><li>Cable modem </li></ul><ul><li>Wireless connection </li></ul><ul><li>Power line </li></ul><ul><li>Satellite </li></ul>Connection through ISP Contents - 2 Direct connection to enterprise network yrityksen or through ISP
  43. 43. Analog modem Digital signal (1101) modeemi Analog signal Digital signal (1101) modem Analog signal Modulation Demodulation Digital signal (1101)
  44. 44. Analog modem Internet-connection: More information about modems: http://computer.howstuffworks.com/modem.htm
  45. 45. Working at home: <ul><li>ISDN </li></ul><ul><li>Analog modem </li></ul><ul><li>GSM </li></ul><ul><li>ADSL </li></ul><ul><li>Cable modem </li></ul><ul><li>Wireless connection </li></ul><ul><li>Power line </li></ul><ul><li>Satellite </li></ul>Connection through ISP Contents - 2 Direct connection to enterprise network yrityksen or through ISP
  46. 46. GSM-network ... <ul><ul><li>A computer can be connected to a GSM phone with a GSM modem. Modem depends on the model of the phone. New phones can use infrared or Bluetooth connection. </li></ul></ul><ul><ul><li>Connection between the phone and a base station is encrypted. </li></ul></ul><ul><ul><li>Data speed is about 6 kbps. </li></ul></ul>Base station <ul><li>Radio waves </li></ul><ul><li>wireless </li></ul><ul><li>encrypted </li></ul>Internet Cell phone network
  47. 47. GSM-network ... <ul><li>Mobile network is made of cells. (cellular network) </li></ul><ul><ul><ul><li>Each cell has a base station </li></ul></ul></ul><ul><ul><ul><li>One base station controller controls many base stations </li></ul></ul></ul><ul><ul><ul><li>Cells may overlap. </li></ul></ul></ul>Base station controller
  48. 48. GSM-network ... BTS = Base Transceiver Station Cell BSC = Base Station Controller MSC = Mobile Switching Centre NSS = Network and Switching Subsystem Other networks BSS = Base Station System MS = Mobile Station SIM-card = Subscriber Identity Module  HLR, ... databases
  49. 49. GSM-network ...
  50. 50. GSM-network ... <ul><li>Databases in mobile telephone network </li></ul><ul><ul><li>Home Location Register ( HLR ) </li></ul></ul><ul><ul><ul><li>Basic information of subscribers, current locations of the telephones and subscribed services </li></ul></ul></ul><ul><ul><li>Visitor Location Register ( VLR ) </li></ul></ul><ul><ul><ul><li>Information of visiting subscribers. Information is copied from subscribers home location </li></ul></ul></ul><ul><ul><li>Authentication Center ( AuC ) </li></ul></ul><ul><ul><ul><li>Authentication information and encryption keys </li></ul></ul></ul><ul><ul><li>Equipment Identity Register ( EIR ) </li></ul></ul><ul><ul><ul><li>List of authorized telephones </li></ul></ul></ul><ul><ul><ul><li>International Mobile Equipment Identity ( IMEI ) </li></ul></ul></ul>
  51. 51. Working at home: <ul><li>ISDN </li></ul><ul><li>Analog modem </li></ul><ul><li>GSM </li></ul><ul><li>ADSL </li></ul><ul><li>Cable modem </li></ul><ul><li>Wireless connection </li></ul><ul><li>Power line </li></ul><ul><li>Satellite </li></ul>Connection through ISP Contents - 2 Direct connection to enterprise network yrityksen or through ISP
  52. 52. ADSL (Asymmetric Digital Subscriber Line) ... <ul><li>Uses normal telephone cable </li></ul><ul><ul><li>Can be used simultaneously with a normal telephone call. ISDN and ADSL may not work together. </li></ul></ul><ul><li>Asymmetric : incoming speed is higher than outgoing speed. </li></ul><ul><ul><li>For example 256/128 kbps, 512/256 kbps, 1 Mbps/256 kbps </li></ul></ul><ul><li>Used only to connect to the Internet </li></ul><ul><ul><li>Need an ADSL modem. </li></ul></ul><ul><ul><li>Permanent connection. Firewall needed. </li></ul></ul><ul><ul><li>Maximum cable length to the telephone exchange is about 5 km. </li></ul></ul><ul><li>Costs: installation + fixed monthly charge </li></ul>
  53. 53. ADSL (Asymmetric Digital Subscriber Line) <ul><li>ADSL is not one standard. Different providers may have different systems. </li></ul><ul><li>Different ways to connect: </li></ul>ADSL modem connected to a single computer. Computer can share the connection to other computers. Personal firewall needed. ADSL modem with a switch (hub). Personal firewall needed in every computer ADSL ADSL ADSL ADSL modem with switch and firewall
  54. 54. Cable modem <ul><li>Works only where a cable TV is available. </li></ul><ul><li>Permanent connection to Internet. Does not need a telephone line. </li></ul><ul><ul><li>Firewall necessary </li></ul></ul><ul><li>Asymmetric </li></ul><ul><ul><li>Incoming speed: 500 kbps - 10 Mbps </li></ul></ul><ul><ul><li>Outgoing speed about 64 kbps </li></ul></ul>
  55. 55. Wireless <ul><li>Customer connection is wireless. Permanent Internet connection </li></ul><ul><ul><li>ISP installs a base station near the customer and connects the base station with a cable to ISP’s own network. </li></ul></ul><ul><ul><li>The customer needs a WLAN adapter and in some cases an external aerial. </li></ul></ul><ul><ul><li>The customer should use a firewall! </li></ul></ul><ul><li>Used WLAN technology (IEEE 802.11) </li></ul><ul><ul><li>A limited number of connections in each base station </li></ul></ul>
  56. 56. Power line <ul><li>Uses normal electric power line. </li></ul><ul><li>Only available in some areas. </li></ul><ul><li>For more information: </li></ul><ul><ul><li>http://computer.howstuffworks.com/power-network.htm </li></ul></ul>

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