There are  several good resources, unfortunately I don't remember enough
about them to point you in the right direction.

But I will answer your second question:

An ISP makes money by buying a two-way, fast, reliable connection and
reselling it as a one-way, unreliable, slow connection.

In general an ISP will only have a certian percentage of its customers
attached or using the internet at any one point in time.  So my cable
company provides me with a '2Mbit down, 128kbit up' connection, but says
"Specs indicate peak speeds - real speeds may vary"  This means that I
might see 2Mbit while downloading a little bit with no one else using
their 'fast, reliable' connection.  But when everybody gets on it is
likely to slow down.

Furthermore they set up proxies.  These machines intercept requests and
if a request seems to be popular (say, CNN.COM) then they cache that
request for a variable lenght of time (1 minute to 1 hour) and any
further requests are intercepted and the cached pages sent instead of
using up the expensive reliable bandwidth for what would be a redundant
request.

So you can have 200 customers connected, with only 42 actually using it
at once.  Those forty are browsing web pages, so they request a page,
they read it, then they request another page.  Say that one person takes
1 minute to read a page before requesting another, and it takes 10
seconds to download the new page over the fast, cached connection.  This
means that for every 6 people using the connection, only 1 is actually
downloading a page.  (we are ignoring large file downloads for the
moment - they have less priority than web pages, and so will simply slow
down when seomeone else is browsing)

So of the forty-two people who are browsing, only 7 are actively
downloading at once.  If you promise your customers a "Peak bandwidth of
2Mbit/s", then you could get two T1's for all your 200 customers, and
most of the time it will seem like they are sharing the equivilant of
two T1's with 7 other people.  In this case it would take much less time
to download a single web page, and so it will often be the case that
only one person will be downloading at a time.

If you apply traffic shaping techniques and properly cache then everyone
sees a fast connection.  For those few file downloaders you can penalize
them (since you aren't selling them guranteed bandwidth) by artifically
slowing down certian types of activity if they are constantly (day in,
day out) overusing the bandwidth.  Tell them there's a reason that a
full T1 is as expensive as it is, and you aren't selling them business
class internet access.  (don't tell them it's actually because the
telecom market gouges people for money)

Oh, and be prepared to handle several customer calls per day for every
hundred customers you have.  People will complain to their ISP for every
little computer problem because "It didn't happen before I was on your
service, so it must be your service...".  This is where you will lose
your money, and why it is so expensive.

-Adam

rad0 wrote:

>----- Original Message -----
>
>thanks Neil, tony
>
>I really would like to know how the upstream backbone works.  I'm wondering
>how you can be a high speed internet service provider, supplying people with
>2Mbps and be supplied with T1 lines, it seems like you would need one for
>each customer, and that doesn't make sense.
>
>And a good list is what I need, if anyone knows of one.
>
>I'm just trying to get an acurate picture in my mind of how this works, from
>a fairly cold start.
>
>I won't clog up the piclist with any more, if anyone knows of a list for
>ISP's -- much obliged.
>
>--
>http://www.piclist.com hint: To leave the PICList
>mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>
>
>
>

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