University of Virginia Computer Science
CS150: Computer Science, Fall 2005

(none)
2 November 2005

CS150 Notes 30 (2 November 2005)

Upcoming Schedule

Notes (for classes 29 and 30)
Latency: time it takes between when a bit is sent and when it arrives at its destination (milliseconds)

Bandwidth: how much data can be transmitted per unit time (bits per second)

You can think of latency as the length of the pipe, and bandwidth as the width of the pipe.

How can we improve latency of a network?





How can we improve bandwidth of a network?





What things you do on the Internet would be better if latency was lower (faster) and bandwidth was reduced?




What things you do on the Internet would be better if latency was higher (slower) and bandwidth was increased?




Tracing Routes on the Internet

] tracert www.virginia.edu
Tracing route to www.virginia.edu [128.143.22.36]
over a maximum of 30 hops:

  1   <10 ms   <10 ms   <10 ms  router137.cs.Virginia.EDU [128.143.137.1] 
  2   <10 ms   <10 ms   <10 ms  www.Virginia.EDU [128.143.22.36] 

Trace complete.

] tracert www.jmu.edu
Tracing route to finch.jmu.edu [134.126.10.60]
over a maximum of 30 hops:

  1   <10 ms   <10 ms   <10 ms  router137.cs.Virginia.EDU [128.143.137.1] 
  2   <10 ms   <10 ms   <10 ms  carruthers-6509a-x.misc.Virginia.EDU [128.143.222.46] 
  3   <10 ms   <10 ms   <10 ms  uva-internet.acc.Virginia.EDU [128.143.222.93] 
  4    70 ms    40 ms    60 ms  nwv-wash-uva.misc.Virginia.EDU [192.35.48.46] 
  5    50 ms    30 ms    70 ms  65.162.89.38 
  6    50 ms    30 ms    90 ms  JamesMadisonU-ROA.networkvirginia.net [204.95.121.114] 
  7    50 ms    40 ms    80 ms  wilson-core.jmu.edu [134.126.2.6] 
  8    80 ms    61 ms   110 ms  finch.jmu.edu [134.126.10.60] 

Trace complete.

] tracert www.fsu.edu
Tracing route to www.fsu.edu [128.186.6.14]
over a maximum of 30 hops:

  1   <10 ms   <10 ms   <10 ms  router137.cs.Virginia.EDU [128.143.137.1] 
  2   <10 ms   <10 ms   <10 ms  carruthers-6509a-x.misc.Virginia.EDU [128.143.222.46] 
  3   <10 ms   <10 ms   <10 ms  uva-internet.acc.Virginia.EDU [128.143.222.93] 
  4   <10 ms   <10 ms    10 ms  abilene-uva.misc.Virginia.EDU [192.35.48.42] 
  5   <10 ms    10 ms   <10 ms  192.70.138.22 
  6    10 ms    20 ms    20 ms  atla-washng.abilene.ucaid.edu [198.32.8.65] 
  7     *        *        *     Request timed out.
  8    20 ms    30 ms    20 ms  sox2fsu-a5002.c7507.fsu.edu [192.80.53.114] 
  9    20 ms    30 ms    30 ms  vlan916.6509.bfs.fsu.edu [128.186.250.17] 
 10    20 ms    30 ms    20 ms  www.fsu.edu [128.186.6.14] 

Trace complete.

] tracert www.govt.nz
Tracing route to www.webportal.govt.nz [202.27.77.188]
over a maximum of 30 hops:

  1   <10 ms   <10 ms   <10 ms  router137.cs.Virginia.EDU [128.143.137.1] 
  2   <10 ms   <10 ms   <10 ms  carruthers-6509a-x.misc.Virginia.EDU [128.143.222.46] 
  3   <10 ms   <10 ms   <10 ms  uva-internet.acc.Virginia.EDU [128.143.222.93] 
  4   400 ms   351 ms   381 ms  nwv-wash-uva.misc.Virginia.EDU [192.35.48.46] 
  5   271 ms   280 ms   221 ms  65.162.89.38 
  6   301 ms   350 ms   291 ms  sl-gw20-rly-2-2.sprintlink.net [160.81.255.1] 
  7   220 ms   221 ms   150 ms  sl-bb20-rly-3-2.sprintlink.net [144.232.14.29] 
  8   180 ms   311 ms   420 ms  sl-bb20-sj-5-3.sprintlink.net [144.232.9.218] 
  9   230 ms   321 ms   350 ms  sl-st20-pa-15-1.sprintlink.net [144.232.20.42] 
 10   171 ms   120 ms   330 ms  sl-newzeal-1-0.sprintlink.net [144.223.243.18] 
 11   441 ms   410 ms   411 ms  p4-0.akbr2.global-gateway.net.nz [202.50.116.177] 
 12   401 ms   401 ms   340 ms  f2-0-0.akbr1.global-gateway.net.nz [202.50.116.166] 
 13   421 ms   431 ms   400 ms  oil-dsl-int.akbr1.global-gateway.net.nz [202.50.119.158] 
 14   470 ms   481 ms   451 ms  202.175.136.129 
 15   601 ms   681 ms   521 ms  192.203.216.21 
 16   490 ms   451 ms   371 ms  192.203.216.22 
 17     *        *        *     Request timed out.
 ...
 30     *        *        *     Request timed out.

Trace complete.
Tallahassee, Florida is about 1200 km from Charlottesville, VA and it takes about 20 milliseconds for data to travel from my office to www.fsu.edu. The fastest data can move is the speed of light (300 000 000 meters per second). If data on the Internet travelled at the speed of light, it would take 3.7 milliseconds. How much opportunity is there to realistically improve the latency of the Internet?





Is data moving at a faster average speed between my office and Tallahassee or my office and New Zealand?





Links

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