[LINK] The PLAN, and broadband speeds?

[Karl Auer]

On Tue, 2007-06-26 at 16:46 +1000, Stewart Fist wrote:
> > * our basic communications world-wide seems to need high speed, high
> > volume links, and i would guess this trend increasing for some time.
> 
> That's not BASIC communications at all.

You are confusing basic as a description of the technology and basic as
a description of need. Our "basic" food needs are not bread and water,
though bread and water is a "basic" diet. Our basic comms needs are not
300bps, though 300bps is a basic technology.

> Geoff's point about satellite delays, only apply to roughly symmetrical
> interactive services, where the back-channel is also over the satellite.
> One way broadcast doesn't suffer delay problems.

Well, no - not broadcast. Not one-way consumption of data. But that's
not what we are talking about - is it? I thought we were talking about
technology that would allow participation. I.e., interactive stuff.

A geostationary satellite sits between 30,000 and 40,000 km up. Say
35,000km. That's 70,000 km up and back, or 140,000 km if both inbound
and outbound links go over the satellite. That's about a quarter- (or a
half-)second delay, non-negotiable, and that assumes that all the other
processing introduces no additional delays.

To put that in perspective, you would have to run your signal through
fibre wrapped three (or six) times around the Earth to achieve the same
delay.

Your little old landline back-channel doesn't help at all, but it could
be a big hindrance, especially if it's a slow or error-prone analogue
phone link.

Satellite delays are less noticeable for things like TV or web-pages,
where a small outbound request results in a large download, but for any
interactive application, satellite links are absolute poo-poo.

> Asymmetrical services can use terrestrial low-bandwidth back-channels

Where you have these nasty latency problems.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)                   +61-2-64957160 (h)
http://www.biplane.com.au/~kauer/                  +61-428-957160 (mob)