DSL, broadband and the like

[plastic quart]

Hello all.

Tis my first post... so go easy on me.

Seeing I do know a few things about Internet connections… unlike Linux (I’ve 
only had Linux on one of my boxes for a few months now… give me some time :) 
  allow me to weigh-in on the broadband discussion.

My 9 to 5 weekdays are spent working with companies of all shapes and sizes 
add Internet circuits (T-1, DS-3, OC-3, OC-12 – fractional and burstable).

And although I do not handle DSL lines specifically (I work for Sprint, and 
ION is our DSL offering... but it is handled by another Sprint business 
unit)... I do know a few things about how it is deployed because I have sold 
T-1's, DS-3's and OC circuits to numerous ISP's for handling their DSL 
customers.  So, what Pat says here (below) is correct.

Typically: Your copper to a DSLAM in the CO where your traffic (along with 
you neighbor's DLS traffic and your ISP's dial-up traffic and your ISP's 
hosted traffic, etc) joins together on your ISP's circuits (which is usually 
several T-1's or a DS-3 or an OC-3) which carriers this traffic upstream to 
their Tier-1 provider... which in my case is Sprint.  Now, of course not 
every ISP handles this the same way. And, of course, I've left a few things 
out for simplicity sake... But you get the picture.

DSL is nice. But I, like many of you, do not live in a "DSL-friendly" 
neighborhood…. although I am using a cable modem as we speak, so I'm not 
complaining too loud. But, one thing I must comment on is the "shared 
bandwidth" argument.

As you can see from the network layout – DSL is shared.  Why can some ISP's 
offer a solid 512k DSL connection to one house, and another ISP offer only a 
128k DSL connection to the same house?... because you are "sharing" the 
ISP’s bandwidth with all of their other users… and the 512k ISP obviously 
has more bandwidth to offer.

The difference between a T-1 and a DSL circuit? Good question. While you do 
share bandwidth with a DSL connection (yes, the "sharing" takes place a 
little further upstream than w/ cable (well, it really doesn’t, but we can 
pretend that it does), but it is bandwidth-sharing nonetheless)... while a 
T-1(or DS-3, or OC-x) circuit gives you a dedicated Point-to-Point 
connection to a router in a backbone node... well, unless you get your T-1 
(or DS-3, etc) from a Tier-2 or Tier-3 provider (your typical baby bell, 
CLEC (Birch), ISP, etc). These Tier-2/3 circuits share bandwidth in the same 
way as a DSL circuit... i.e., you get a "static" information rate up to your 
provider, but from their facilities on out to the Internet, you are sharing 
capacity with all of their other customers.

By the way... in case you are wondering what a T-1 is going for these 
days... I'll tell you:  roughly $1200 per month, total. (Unless, of course, 
you live in the middle of nowhere). Now, is the admittedly much higher cost 
justifiable? I don’t know. And, of course I am a little biased. But, I will 
say this... your ISP, CLEC, ILEC, etc uses this type of circuit to carry 
your DLS traffic upstream to the Internet.

Whew.  Well, I hope that isn’t too much for a first post.  But it should 
clear up a few things. If anyone has any questions that I didn’t address... 
post away.

Kirk

----- Original Message -----
From: "Pat Miller" <pert at tas.tas-kc.com>
To: <kclug at kclug.org>
Sent: Friday, April 21, 2000 10:46 AM
Subject: Re: kclug - Re: DSL factoids

>There are a lot of misconceptions going on here about DSL
>
>the copper pair is only used between your place ant the co (unless the co
>won't give you/your ISP shelf space)
>
>Once in the CO the copper is fed into a DSLAM. This breaks the signal into
>two voice goes to the voice (channel bank, coil, etc.) The Data gets 
>decoded
>and switched to the ISP of your choice. Typacly your ISP needs a leased 
>line to each
>co that it wants to serve customers out of. There may be a common ISP ATM
>line (that would make sense for some of the smaller ISP's then they could
>split the cost via usage).
>
>  Not all ISP's use CPE (Customer Premise equipment) that is compatible 
>with
>the DSLAM that is used by the RBOC. SBC's only offer certain brands of 
>ADSL.
>So CLECs/ISPs need shelf space to put in their own DSLAMs.  RBOCS claim
>there is little space, but there CO's are becoming mostly empty
>because equipment is so much smaller; and to cut
>distances and competitors, RBOCs have started to put shelfs with 
>slicks/channel
>banks & DSLAMs in each neighborhood. When doing this the copper distance
>becomes a few blocks or less, but if those are considered a part of the
>CO--requiring CLECs the ability to use available space--they are making the
>space so small that there is no room for clecs.
>
>
>
>Different DSL flavors (SDSL ADSL HDSL...) and speeds use different 
>distances.
>HDSL requires 4 wires but is high speed...
>SDSL offers same speed in each direction...
>ADSL (async?) is faster on the download)... SDSL causes less interference 
>than the type of ADSL encoding SBC
>uses...
>
>Longer distances require/yield lower speeds.
>

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