[NCLUG] DSL Throttling or General Congestion?

[Sean Reifschneider]

On Wed, Nov 22, 2006 at 09:06:20PM -0700, Michael Milligan wrote:
>1.5Mb/s to the fiber, whether it is ATM or not is irrelevant (though I

Well, ATM does add almost 20% overhead to sending IP traffic, which is why
1.5mbps DSL traffic only actually shows around 1.25mbps on DSL speed tests.

>can't stuff 10.5Mb of traffic onto one 1.5Mb/s ATM VC when everyone

As far as I know, if you have 10 houses with 1.5mbps service, each of them
have a 1.5mbps ATM VC directly from your DSL modem to the ISP's router
terminating their Megacentral.  Now, if they have a DSLAM located in your
area, that has a 1.5mbps T1 for connectivity to the ATM cloud, that would
siphon all of you into a 1.5mbps channel.

No idea how likely that is.  I know in the past QWest has been reluctant
to put DSLAMs anywhere except the COs, because doing so would mean that
they'd have to give competitors access to remote terminals as well.

>congestion.  And if I'm right, that will have little to do with which
>ISP I'm using to take my IP packets.

Well, it depends on a number of things.  Could be the ATM line from the
DSLAM, or a longer haul ATM line like going to Denver (remember ATM can
provide a VC from Fort Collins to anywhere in the northern Colorado LATA.
So your ISP could terminate it in Grand Junction for all you know, which is
a lot more opportunity for congestion across the cable miles.  Of course,
the line from Denver to Grand Junction is a pretty big pipe, compared to
the pipe from a DSLAM to the CO.

>Does anyone else think it's not a Qwest issue and switching ISPs would

Hard to say.  Get another DSL line and if it fixes it drop the other one,
and if it doesn't call up QWest and whinge?  We have both cable and DSL,
with cable primary and DSL for when cable falls over.  Though it hasn't
happened much in the last 6 months, the previous 6 months were pretty
nasty.

>help?  I'm game to go with FRII if it makes sense, they've been pretty
>good to me w.r.t. co-lo service...  But from talking with a tech at
>FRII, bascically all the Qwest DSL traffic is aggregated locally, routed
>over the ATM cloud down to Denver (building on 16st Street), then
>cross-connected to all the various ISPs that are available (most with
>zero-mile DS3s or OC3s)...  so I doubt it would make any difference.

That is very FRII-specific.  FRII used to have a megacentral here in Fort
Collins when they first started offering it, but now I think all of their
DSL concentration for QWest happens in Denver in the Carrier Hotel
building.  However, the ISPs that used to terminate DSL via NCIC were all
terminated on a line connected from the Fort Collins south switch.  We had
DSL through that, which was great because our home DSL line also terminated
at the south switch, so our first IP hop was an ATM VC that went over our
POTS line, into the CO, then right onto the DS3 to the router terminating
it.  However, recently NCIC dropped their DS-3.  I don't know anyone else
in Fort Collins that is terminating DSL locally for consumers, but there
probably are some...

>something is available (can you say "WiMAX trial" anyone?).  It's so bad
>that I'm even considering going back to CWX...

I guess cable isn't an option in your area?  The 8mbps service is pretty
tasty, though I wish the upstream link were a bit faster...  LP Broadband
I've had pretty good luck with at the Moxie coffee shop on Harmony, and
they do donate the wireless for the bazcamp camping events we have been
having, and it's worked well for that.  Lots of wireless choice, which is
good.

Sean
-- 
 We have just gotten a wake-up call from the Nintendo Generation.
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Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995: Ask me about High Availability