[NCLUG] DSL Throttling or General Congestion?

[Sean Reifschneider]

On Tue, Nov 21, 2006 at 01:47:56PM -0700, Stephen Warren wrote:
>Out of curiosity, do you happen to know the difference between "G.DMT
>Annex A" and "T1.413"?

Only lexically.  :-)

>equipment terminates the ATM session, extracts the packets (IP over PPP
>it seems in my case) and then routes the content as IP packets. I was

Probably more correct to say "IP as PPPoATM", just to be canonical.

>Isn't it possible for the ISP to co-locate their ATM->xxx equipment in
>the CO (or wherever) and choose to run say GigE over fiber back to their

Actually, the more likely scenario is that someone brings an OC-3 into
their machine space, terminates it into their own mini-switch (a smaller
version of what the telco has at their CO), then breaks that OC-3 down into
a DS-3 with ATM which they hand off to a router via a dual coax connection,
which then "converts" it into IP over Ethernet.

The reason I come up with this scenario is that it's much easier to get an
OC-3 into your own building than it is to get your equipment into a Central
Office (where they would be handing you a DS-3 or OC-3 anyway), and then
also getting more equipment connected to some dark fiber that runs to your
location.  I know several ISPs/colo facilities that do the previous
paragraph, but only one that does the latter, and they're actually the
ILEC...

Some ISPs locate equipment *CLOSE* to the telco CO, where various telcos
can run "cheap" high-speed lines, where they then just basically connect it
to their own networking infrastructure.  At least one ISP I know of is in
the building next to the Denver Main telco switch, which is called the
"carrier hotel", and gets probably an ATM for DSL as well as transit to the
rest of their network, and also gets IP connectivity for Internet access,
and that location basically just becomes another extension of their private
network, with transit access to the Internet.

QWest does offer a 100mbps or gigabit Ethernet from location to location.
This is commonly called a Metro Area Network, and we were looking at one
this summer.  Basically, they would have just put routers with Ethernet on
one end and OC-3 on the other side (or better, for gigabit), and run some
level of transit on their network, possibly ATM.

Long-haul is almost always done by one of the phone network lines like an
OC or DS.  An exception is Yipes, which in Fort Collins has a bunch of
fiber running around that they basically run Ethernet on.  They terminate
their fiber directly into a regular (though smart) switch, which has a few
fiber ports and then regular copper ports which they provision using
shaping for whatever speed service you purchase from them.

This goes back to their central location, where they have (last I heard) an
OC-3 or two running to Denver, and (for a while) some connectivity
going north to Cheyenne.  I haven't used Yipes in almost 2 years though,
this may have changed.

Back to that one place where they're running Ethernet over their own dark
fiber.  They're the ILEC in their location, and a client of ours.  At one
point they asked us for help setting up backups to run between their
buildings in two towns, about 50 miles apart.  I verified that they had
plenty of bandwidth so they wouldn't be impacting other IP services: "You
have a DS-3 between those locations?"  "No, we took a spare pair of fibers
and put 100mbps Ethernet transcievers on each end, and a few repeaters in
the middle, so it's 100mbps Ethernet dedicated."  They've since upgraded it
to gigabit.  Must be rough.  :-)

>location? They'd just be leasing the raw fiber from Qwest, or whoever,
>for this, so Qwest wouldn't care about the protocol on the fiber.

As far as I know, QWest doesn't do this.  Platte River Power Authority in
Fort Collins has a ring that runs around town, which you can rent pairs on
and splice into, for a fee.  I believe Yipes uses this as part of their
transit.  I believe you have to commit to a 10 year deal, which works out
pretty cheap per month, relatively, but is a big lump sum, and then you just
have to use an approved person to do the splicing.

QWest will almost always provide you something that is a normal telco line.
because that's what they're comfortable with.  The person you speak to
about a 100mbps connection between buildings, has probably been
provisioning that sort of line for 20 years.

Remember that Ethernet line I mentioned we asked QWest for a quote for
above?  They then gave me pricing for bandwidth utilization of that line,
going all the way up to DS-1 bandwidth!  Yep, 1.544mbps delivered via
Ethernet at each end.  They are *SO* stuck in the '60s.

Sean
-- 
 I remember when legal used to mean lawful.  Now it means some kind of
 loophole.  -- Leo Kessler
Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995: Ask me about High Availability