Re: a question on what I buy when I get a broadband connection.

[David Farber <dave () farber net>]

Begin forwarded message:

From: "Mike O'Dell" <mo () ccr org>
Date: February 28, 2007 12:02:35 PM JST
To: dave () farber net
Subject: Re: [IP] a question on what I buy when I get a broadband  
connection.

i suspect you are getting something which will never go *faster* than
6 megabits averaged over some interval - possibly as small as a
bit-time, or possibly as large as a few minutes. clearly the Mean
Value Theorem is your friend with longer averaging intervals.

this is called a "peak number" - you won't ever do better than this,
and how close you ever come is separate a discussion in its own right.

you need to ask the question of your service provider - it depends
entirely on their product definition.  at least in the case of
leased-line IP service, there are both "tiered" and "burstable"
services with tiered being more expensive than burstable in most
cases. precisely what duty cycles are implied by those two classes of
service are a function of the provider's product definition. again,
ask your provider - there is no single industry definition of the
terms or services.

as for economics, a guaranteed 6 megabit sustained bearer should
cost on the order of multiple 100s of dollars per month regardless
of implementation technology. packet switched networks rely on
statistical multiplexing for sharing - simulation of isochronous
links is not something they do very well or very cheaply.

the fundamental question is whether you are trying to optimize latency
or bandwidth - it's hard to to both at the same time (not impossible,
just hard).

for most purposes, i'd much rather have a 100 megabit bearer that
requires me to be less than 6 megabits averaged over 5 minutes 95% of
the time than a 6 megabit bearer that guarantees me 6 megabits all the
time.  the former is likely much cheaper as well.

     -mo


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