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Link characteristics. S kills : none Concepts : Link characteristics -- technology, length, speed , latency, jitter and packet loss rate, units of measure for amount of data and connection speed, link trends and the gap between developed and developing nations.

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  1. Link characteristics Skills: none Concepts: Link characteristics -- technology, length, speed, latency, jitter and packet loss rate, units of measure for amount of data and connection speed, link trends and the gap between developed and developing nations This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

  2. Where does this topic fit? • Internet concepts • Applications • Technology (communication) • Implications • Internet skills • Application development • Content creation • User skills

  3. Link characteristics Computer 2 Computer 1 Link technology Link length Link speed Latency, jitter and packet loss rate

  4. Wireless connection technologies Terrestrial radio Satellite radio

  5. Wire-line connection technologies Copper, twisted pair (electronic) Copper, coaxial cable (electronic) Fiber (optical)

  6. Only use wireless links when a wired connection is not convenient or possible.

  7. Link characteristics Computer 2 Computer 1 Link technology Link length Link speed Latency, jitter and packet loss rate

  8. Link length

  9. Link characteristics Computer 2 Computer 1 Link technology Link length Link speed Latency, jitter and packet loss rate

  10. What are some unit of measure for … Length? Weight? 0101010101001011010010111001010101010010101010001010101010101010100101010010101010010010010010101010010001010101011101001010010101010 Data?

  11. Units of measure for quantity inches, meters, millimeters, miles, nanometers, light years, etc. pounds, ounces, grams, kilograms, tons, nanograms, milligrams, etc. 0101010101001011010010111001010101010010101010001010101010101010100101010010101010010010010010101010010001010101011101001010010101010 bits, bytes, kilobytes, kilobits, terabits, megabits, gigabytes, etc.

  12. What are some units of measure for time?

  13. Units of measure for time hours, days, weeks, years, centuries, seconds, microseconds, nanoseconds, and so forth

  14. Rate = quantity per unit of time Distance traveled per unit of time

  15. Units of measure for data transmission rate Transmission rate = amount of data per unit of time

  16. Units of measure for data transmission rate Transmission rate = amount of data per unit of time

  17. Units of measure for data transmission rate Transmission rate = amount of data per unit of time

  18. The Internet Home

  19. Link characteristics Computer 2 Computer 1 Link technology Link length Link speed Latency, jitter and packet loss rate

  20. Latency – the time for the first packet to arrive

  21. Jitter Which has the lowest jitter?

  22. Packet loss rate

  23. Service level agreement

  24. Speed and ping tests

  25. The link from your home to the Internet ? Home LAN The Internet LAN router ISP router

  26. Typical speed examples

  27. Global view PingER at Stanford University http://bit.ly/mnruYf

  28. Steadily faster

  29. International traffic

  30. Intercontinental traffic flows

  31. Summary Computer 2 Computer 1

  32. Self-study questions • We discussed several characteristics of a communication link. Without looking back, do you recall what they were? • Name two units of measure for each of the following: • Weight • Length • Rate at which you run • Amount of data • Rate of data transmission • The general form of a unit of measure for velocity is distance/time. What is the general form of a unit of measure for data transmission speed? • What unit of measure would you use for a quantity of water? • What unit of measurement would you use for the rate at which water flows through a hose? • When you walk, you typically travel at rate of about 4 miles per hour. Convert that to miles per second. • When you walk, you typically travel at rate of about 4 miles per hour. Convert that to feet per second. • How many bits in a megabyte? • How long would it take to transmit a 100 megabit file over a 100 megabit/second link? • How long would it take to transmit a 100 megabit file over a 10 megabit/second link? • How long would it take to transmit a 100 megabit file over a one gigabit/second link? • How long would it take to transmit a 100 megabyte file over a 100 megabit/second link? • How long would it take to transmit a 100 megabit file over a 100 megabyte/second link? • How long would it take to transmit a 132 megabyte file over a 12 megabit/second link? • What are the speed, technology, length and monthly cost of the link from your home to your Internet service provider? • We saw that Internet links are often asymmetric – faster in one direction than the other. Why is the transmission rate from your ISP to your home faster than the other direction?

  33. Resources Test ping times: http://pingtest.net Test data transmission rate: http://speedtest.net A more detailed link test with hints to improve performance by adjusting TCP parameters: http://ndt.anl.gov Current data on Verizon network performance: http://www.verizonbusiness.com/about/network/latency/ The 2010 Stanford report on Internet performance:http://www.slac.stanford.edu/xorg/icfa/icfa-net-paper-jan10/report-jan10.doc Aladdin Nassar, Worldwide Inventory of Last-mile Bandwidths & Network Latencies:http://velocityconf.com/velocity2010/public/schedule/detail/14075 Project PingER: http://www-iepm.slac.stanford.edu/pinger/

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