Tom DeReggi wrote:
First off, in true technical theory, it is my opinion, that Latency
=speed, Transfer rate = capacity. Latency is the "speed" in which one
packet goes from point A to Point B. Transfer rate is the "quantity of
packets" that can be transfered within a specific time. Therefore the
Term "Speed" is incorrectly used in marketing.
While your usage is correct from the perspective of physics, the
customer's perception of speed is the relevant one. I suspect most
customers would say a service with 10Mbps and 30ms latency to a major
backbone is "faster" than one with 1Mbps but 5ms latency to that same
backbone.
(I'm assuming some value of "normal" here. Satellite-grade latency of,
say, 2000ms, obviously skews customer perceptions. I don't know where
I'd want to put the cutoff, but the exact numbers aren't as important here.)
As an aside, most of what I'm doing is purely speculatory from here on
in. Anyone know whether any serious academic research has been done on
this point?
Anyway, I don't want this to turn into anything related to semantics.
Let's get back to the good stuff :)
MP4 Streaming Video-- only needs 400kbps.
VOIP --- only need MAX of 70kbps.
Web Browsing, VERY LITTLE, as most images are web optimized.
Haven't been to YouTube lately, I take it? :)
Between high-bandwidth services like that (and DailyMotion and Google
Video and all the other folks doing the same sort of thing), and the
dreaded peer-to-peer, and teleconferencing and maybe even telemedicine,
and ...
My point is that while your numbers above may be sufficient for very
casual users, today, those numbers won't hold much longer. I'm not sure
they even hold today, honestly. Many residential customers want and
expect more bulk bandwidth.
I just looked at amazon.com's front page (to borrow one of your
examples), and there's about sixty distinct images, plus the page's
HTML, and other stuff like JavaScript and CSS imports. If you just
cleared out your browser and DNS cache, and had to load that page
completely from scratch, it's likely to take ten to fifteen seconds to load.
(www.websiteoptimization.com offers a testing tool for that, but they're
throwing in ridiculous latency numbers of 200ms per file, cumulative,
and apparently never have heard of HTTP pipelining. I don't think I
would take their numbers too seriously, but it's a good way to get basic
"how big is a page" data to play with.)
The simple amount of bulk data there - amazon's home page including all
those graphics adds up to around 300k, though it changes as the whole
page is dynamic - is the key in this instance. Doesn't matter if you're
plugged straight into amazon.com with a crossover cable in this
instance; the perception of slowness comes not from the latency but from
the volume of data.
eBay's home page isn't much better, and CNN.com's front page, including
all scripts and images, is about 250 files and nearly 800K. (For
comparison, on a classic 56k dialup, that's probably about three minutes
just waiting for the front page to load.)
Sure if you are a IT guy -constantly downloading software drivers, or a
Designer or Architec -constantly transfering CAD/Layout files, sure
"Transfer Rate" is going to be important to you.
In all fairness, I should disclose my bias, it's been argued I'm an IT
guy. :)
PS. I recognize next generation applications such as HD TV, can easilly
justify GB transfer rates to the home. But we aren't in that generation
today.
I think that generation is much, much closer than you think.
David Smith
MVN.net
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