School Computing

Bandwidth Calculations

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For a more general discussion of network optimization, see Internet & Network Bandwidth & Monitoring & QOS

Software ToolsEdit

To measure your Internet connectivity speed, you can use:

How Much is Enough?Edit

One of the challenges as one moves to a 1:1 environment is determing how much bandwidth is enough. As part of that process I have developed a simple measure that I have found useful. Take the total available bandwidth and divide it by the number of end user CPUs in the network.

Using this technique, I surveyed several 1:1 independent schools in January of 2006. It appeared useful to separate them into two catagories managed and unmanaged as this had a substantial impact on relative satisfaction with the bandwidth available. Contributors are anonymous as I did not ask their consent for this use.

Managed (includes use of proxy server, packet shaper, or other management tool)

State Students Grade levels 1:1 Grades Student Laptops Faculty Total CPU Total Bandwidth Bandwidth/CPU
CT 820 PK-12 7-12 500 120 750 1.5 MB 2.0 K
  Packet shaping is key, page rendering 2 to 3 seconds. Downloading during the day is "a joke." A separate circuit is used for tech support and video conferencing.
CA 295 9-12 9-12 295 40 410 3.0 MB 7.3 K
  Using NetEnforcer, blocking P2P and some games, bandwidth monitoring, feels they need more capacity. Increasing summer 2006.
TN 625 5-12 7-12 575 120 750 10.0 MB 13.3 K
  Using NetEnforcer & caching, blocking P2P, IM, some streaming, email throttled, audio files limited until 3:00 PM. Happy with performance.
OH 870 K-12 5-12 550 130 850 11.5 MB 13.5 K
  Has Packeteer, but not shaping since last bandwidth increase. Gaming only permitted in one location. Happy with performance.
TN 787 K-12 9-12 200 30 500 6.0 MB 12 K
  Use Packetsure for bandwith shaping and protocol blocking as well as URL blocking. Using Stratacache for caching services. Very happy with performance since moving from a T1

Unmanaged (no proxy, packet shaping, or other active management. Filtering may be present.)

State Students Grade levels 1:1 Grades Student Laptops Faculty Total CPU Total Bandwidth Bandwidth/CPU
CA 1650 K-12 9-12 675 180 1775 1.5 MB 0.8 K
comment: http, and ftp all unacceptably slow. Video conferencing on separate DSL circuit. Upgrade in progress.
TN 740 PK-12 7-12 320 75 600 3.0 MB 5.0 K
comment: No student use in unsupervised settings. Performance is ok.
FL 1200 PK-12 4-12 900 160 1100 14.0 MB 12.7 K
  No gaming or social networks during academic day. Happy with performance
CT 400 9-12 9-12 400 80 650 16.5 MB 25.4 K
  Caching is used. Some ad blocking. Happy with performance

Proposed rule of thumb based on this anecdotal evidence:
When bandwidth is managed, happiness is reached between 8 K and 13 K per CPU.
When unmanaged the required levels may be higher.

Other contributions to the pool of evidence would be welcome.


Dan Hudkins - The Harker School - San Jose, CA

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