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Speed for On-or Off-campus Access

This article applies to: Shared File Services


Technical detail about on-campus vs. off-campus speed. This is a more detailed version of the FAQ entry: Speed for on- or off-campus (from a remote office or home via VPN).

IP-network connectivity is measured in mega-bits per seconds, Mb/s.

  • File sizes are typically measured in mega-bytes, MB.
  • File transfers (throughput) are normally measured in mega-bytes per second, MB/s.
  • Latency is the “response time” for the round-trip from your computer to a network location (SFS) and back, a “delay” in every I/O operation.

It is very common for people to think of Mb/s and MB/s as the same thing, however they are vastly different.

  • 8 bits = 1 byte
  • 8 mega-bits (Mb) = 1 mega-byte (MB)
  • This is an 8:1 ratio.

On-campus a computer can typically obtain 40 mega-bytes/s (MB/s) while copying files to/from SFS.  This is a “cap” imposed by our storage device, and has nothing to do with the potential of the network or your computer.

  • On-campus the typical latency is less than 1 milli-second.
  • Off-campus this kind of performance is not to be expected with SFS.

As an example, Time Warner Cable (RoadRunner) connectivity is advertised as follows: (See table for more data)

  • Turbo: 
    • 20 mega-bits/s download
    • 2 mega-bits/s upload
  • Standard: 
    • 15 mega-bits/s download
    • 1 mega-bits/s upload

 Note:  These are NOT mega-bytes per second.
 
With these numbers the following throughput should be expected while copying files over Time Warner Cable/RoadRunner (1/8 of the numbers above).

  • Turbo: 
    • 2.50 mega-bytes/s download,
    • 0.25 mega-bytes/s upload  
  • Standard:
    • 1.87 mega-bytes/s download
    • 0.125 mega-bytes/s upload

In testing the latency (response time) has been as high as 55 milli-seconds on RoadRunner.

Connection Download Mb/s
(mega-bits per sec)
Upload Mb/s
(mega-bits per sec)
Download 5 MB MP3 audio file
(seconds)
Upload 5 MB MP3 audio file
(seconds)
Download 3 GB DVD/ISO file
(seconds)
Upload 3 GB DVD/ISO file
(seconds)
On-campus to SFS 350 350 0.13 0.13 75.88 75.00
Time Warner RR Packages
Ultimate 50 5 0.80 8.00 480.00 4,800.00
Extreme 30 5 1.33 8.00 800.00 4,800.00
Turbo 20 2 2.00 20.00 1,200.00 12,000.00
Standard 15 1 2.67 40.00 1,600.00 24,000.00
Basic 3 1 13.33 40.00 8,000.00 24,000.00
EveryDay 2 1 20.00 40.00 12,000.00 24,000.00

Most home users have Turbo or Standard.

  • SFS caps file transfers at ~ 40 MB/s (mega-bytes/second), = 320 Mb/s (mega-bits/second).
  • Gigabit connectivity (desktop or server) allows for up to 1,024 Mb/s maximum.
  • Time Warner's offerings are slower on UPLOAD than DOWNLOAD

Effectively SFS is ~6-160 times faster on-Campus for a download (copying a file), and 64-320 times faster for an upload (write a file), compared to remote-access via VPN over RoadRunner.

About this Article

Last updated: 

Wednesday, April 5, 2017 - 12:11pm

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