RE: [MLUG] PGP, Cable, DSL and Sniffing, & MU Network

["Spurling, Shannon " <EMAIL:PROTECTED>]

 Well, GTE dosen't provide ATM service to any one else. And they don't
provide OC
 service to any one else, either. They deem both of these as not cost
effective.
The PVC information (ie DLCI's) should not be visable on the ethernet side,
unle
ss he was looking in the ADSL "Modem". The Ethernet is encapsulated by the
bridg
e on one side, and decapsulated on the other. It should look seamless, like
you
were plugged directly into a slow ethernet on that bay router.
A little secret about phone companies, they talk crap. Don't take every
thing th
ey say at face value. You will get different stories from different techs.
Just
talk to them long enough, and to enough of them, and you will be surprised
what
you find out. With a frame relay circuit, you don't normally define a burst.
You
 let the circuit take care of that. You define the CIR, and that can be what
eve
r. Here is one place where you can't always believe the phone company. I've
had
T1's with full CIR, and the site complains about slowness. You look and they
are
 peaking out at about 50%. You go back and ask the phone company, and the
tech s
ays "well, that's how they all are!" You have to grab them by the ear, and
drag
them down to the provisioning office, and make them look at the circuit
order.
You should be able to sniff a T1 using RF teqnuiqes to regenerate the
siginal on
 an adjacent line. With ADSL, you would have to know how the spectrum on the
lin
e was negotiated. ADSL is not a clear digital siginal, and the carrier
frequency
 that they use could be any thing, depending on what the frequency response
of t
he line is. IF you want more information, you could check out:
http://www.dsl-list.com/DSL_faq.htm

Thanks

Shannon

-----Original Message-----
From: McNutt, Justin M.
To: EMAIL:PROTECTED
Sent: 1/31/01 1:14 PM
Subject: RE: [MLUG] PGP, Cable, DSL and Sniffing, & MU Network

> GTE doesn't do ATM. Only frame relay.

Au contraire.  GTE DOES do ATM, but only within their own network.

> How did you see all 
> this? You should
> not see any DLCI information if you are connected to the 
> Ethernet, you will
> only see Ethernet frames.

Everything he desribed is visible from the Ethernet side.  The rest was
deduction.

> The virtual circuit is going to terminate at your ISP. GTE 
> doesn't do any
> thing with it, but take it from one point to another.

True.  They take it from the ADSL modem all the way to the TCR1 router.

> Rate limiting is a
> physical thing. They limit the rate at the ADSL modem, and 
> then the physical
> line also limits the rate. These ADSL lines are actually limited to
> 64,128,384,768, and 1024, which leads me to believe that they 
> are using
> standard T1 signaling.

They are, although that's not how they're limiting the bit rate
(according
to GTE).

> The number they give you for your 
> maximum bitrate is
> determined by haw many T1 channels they give to you.

It's more than that, because you have two rates:  your CIR and your
Burst
Rate, neither of which must be divisible by 56K or 64K.  Example:  There
are
folks whose CIRs are 10Kb and 32Kb.  All of the Burst Rates I've seen
are
divisible by 64K, although I have no indication that they MUST be.

> want to do. They could run PPP or HDLC, and bridge the 
> Ethernet over it, or
> they could just route IP over it, they could do all kind of 
> fun stuff. 

They're doing something like the former.  The ADSL network looks like
one
big Ethernet, aside from the PVC-to-PVC quirks I described before.  Any
protocol works, although we're only routing IP to the outside world.

> I think the key here is that point-to-point WAN links aren't easily
> sniffable outside of the carriers premises. You have to break 
> into one of
> the endpoints.

...true, such as the GTE DSLAM, a GTE frame switch, or the TCR1 router
(probably the easiest, really, since it can do packet captures on its
own
and send them to you).

> Sniffing the actual ADSL stream is going to be 
> difficult in
> the least.

About as difficult as sniffing a genuine T-1, which I'd never bother to
do.
:-)

> There are ways to eavesdrop on any thing, but it's really
> difficult to do on fiber and DSL. Cable would be easy. 
> Personally, I don't
> care who knows I go to joecartoon.com. :-)

Agreed, but it's good to be aware that unless you've encrypted it, it's
probably insecure.

--J
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