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)
- 20 mega-bits/s download
- 2 mega-bits/s upload
- 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).
- 2.50 mega-bytes/s download,
- 0.25 mega-bytes/s upload
- 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.
(mega-bits per sec)
(mega-bits per sec)
Download 5 MB MP3 audio file
Upload 5 MB MP3 audio file
Download 3 GB DVD/ISO file
Upload 3 GB DVD/ISO file
|On-campus to SFS||350||350||0.13||0.13||75.88||75.00|
|Time Warner RR Packages|
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.