Security: April 2005 Archives

TIPPINST- I commented earlier this week on the release of phase 1 community broadband figures. 43% of communities elected to use satellite as their preferred method of access. I was quiet surprised by the high adoption rate.

I can understand if you are in a rural area with no other option than to use satellite, what has me surprised are some of the benefits that you miss out on if you do choose satellite.

There are two big problems with satellite they are bit error rate and latency. The latter is usually more noticable than the former. From talking to people who have employed satellite in business and educational premises, they have remarked upon how it can be slow.

There is confusion as to how much latency there really is, ildana.net point out that delay is 240ms (0.24 seconds) this is true based on the maths of calculating the length of time it takes a signal to travel from satellite earth station to another

(22300 miles uplink + 22300 miles downlink) / 186000 miles per second = 0.24 seconds (240 ms).

This answer however is deceptive as is does not take into account the additional time required for processing by electronic equipment at the originating, receiving, and repeater stations, which adds to the total delay. In practice, round trip transaction time can easily exceed 750 milliseconds

Satellite Internet access providers such as vsat systems are more open about the problem and point that the latency is in the 600 ms range , they offer tcp spoofing as a means to combat this problem.

So the 750 ms delay that satellite experience does have an impact on certain technologies, these include Voice Over IP (products such as skype), video conferencing and VPNS.

The phrase caveat emptor springs to mind when considering broadband products, all aspects must be considered. If VOIP, video conferencing and VPNS are not a requirement then satellite might well be the suitable choice for you.