1. 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. Link characteristics

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

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

4. Wireless connection technologies Satellite radio Terrestrial 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 technology Link length Link speed Latency, jitter and packet loss rate Link characteristics Computer 1Computer 2

8. Link length

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

10. 0101010101001011010 0101110010101010100 1010101000101010101 0101010100101010010 1010100100100100101 0101001000101010101 1101001010010101010 What are some unit of measure for … Length?Weight? Data?

11. 0101010101001011010 0101110010101010100 1010101000101010101 0101010100101010010 1010100100100100101 0101001000101010101 1101001010010101010 Units of measure for quantity inches, meters, millimeters, miles, nanometers, light years, etc. pounds, ounces, grams, kilograms, tons, nanograms, milligrams, etc. 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 Time? Amount of data? Transmission rate? Transmission rate = amount of data per unit of time

16. Units of measure for data transmission rate Timesecond Amount of databit Transmission rate? Transmission rate = amount of data per unit of time

17. Units of measure for data transmission rate Timesecond Amount of databit Transmission ratebits per second Transmission rate = amount of data per unit of time

18. The Internet Home

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

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

21. Jitter Distance (miles) P1 (ms) P2 (ms) P3 (ms) P4 (ms) Avg. (ms) Jitter (st dev) Santiago Chile5,58541234622822530392.08 Oxford England5,408195194195193194.96 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 LAN router ISP router Home LAN The Internet ?

26. LinkTypical speed residential DSL link3 mb/s residential cable link10 mb/s residential fiber link25 mb/s residential satellite1 mb/s Link from our campus to CSU net1 gb/s intercity fiber10 gb/s undersea fiber cable1 tb/s Typical speed examples

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

28. Steadily faster

29. International traffic

30. Intercontinental traffic flows

31. Summary Computer 1Computer 2

32. Self-study questions 1.We discussed several characteristics of a communication link. Without looking back, do you recall what they were? 2.Name two units of measure for each of the following: Weight Length Rate at which you run Amount of data Rate of data transmission 3.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? 4.What unit of measure would you use for a quantity of water? 5.What unit of measurement would you use for the rate at which water flows through a hose? 6.When you walk, you typically travel at rate of about 4 miles per hour. Convert that to miles per second. 7.When you walk, you typically travel at rate of about 4 miles per hour. Convert that to feet per second. 8.How many bits in a megabyte? 9.How long would it take to transmit a 100 megabit file over a 100 megabit/second link? 10.How long would it take to transmit a 100 megabit file over a 10 megabit/second link? 11.How long would it take to transmit a 100 megabit file over a one gigabit/second link? 12.How long would it take to transmit a 100 megabyte file over a 100 megabit/second link? 13.How long would it take to transmit a 100 megabit file over a 100 megabyte/second link? 14.How long would it take to transmit a 132 megabyte file over a 12 megabit/second link? 15.What are the speed, technology, length and monthly cost of the link from your home to your Internet service provider? 16.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.nethttp://pingtest.net Test data transmission rate: http://speedtest.nethttp://speedtest.net A more detailed link test with hints to improve performance by adjusting TCP parameters: http://ndt.anl.govhttp://ndt.anl.gov Current data on Verizon network performance: http://www.verizonbusiness.com/about/network/latency/ 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 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 http://velocityconf.com/velocity2010/public/schedule/detail/14075 Project PingER: http://www-iepm.slac.stanford.edu/pinger/http://www-iepm.slac.stanford.edu/pinger/