Hi all

How do I access an ADSL modem from the phone line end? As I understand
it, normally an ADSL modem is connected to a phone line which is
connected to a DSLAM which is connected to an internet backbone which
is accessible via TCP/IP. I want to connect the phone jack of the ADSL
modem to twisted pairs which is connected to a device of some kind
which has an ethernet port coming out of the back of it, so I can talk
TCP/IP with the kit connected to the aforesaid ADSL modem.

Conceptually this would be like connecting the phone jacks of two ADSL
modems together, but I don't think you can do that. Or at least, if
you do it, I don't think it works!

I've seen some DSLAMs with ethernet ports: would something like this
work, or are the ethernet ports just for diagnostics, or controlling
the DSLAM via SNMP, or something like that?

Just in case the above is far too easy, all the DSLAMs I've seen are
quite big and heavy. I'm looking for a device I can attach to a laptop
and carry around.

Any thoughts?

On 14/08/2008 22:04, wrote:

How do I access an ADSL modem from the phone line end?

When you say "ADSL modem" do you mean a USB modem or an Ethernet router?
(alternatively I suppose you could mean an ethernet modem, but I'll
assume you don't for now).

As I understand
it, normally an ADSL modem is connected to a phone line which is
connected to a DSLAM which is connected to an internet backbone which
is accessible via TCP/IP.

Yes, a DSLAM is telco equipment, large and rack-mounted and handling
hundreds of phone lines.

I want to connect the phone jack of the ADSL
modem to twisted pairs which is connected to a device of some kind
which has an ethernet port coming out of the back of it, so I can talk
TCP/IP with the kit connected to the aforesaid ADSL modem.

Eh?

Conceptually this would be like connecting the phone jacks of two ADSL
modems together, but I don't think you can do that. Or at least, if
you do it, I don't think it works!

No you can't connect two ADSL modems back to back, the A in asymmetric
means the modems try to download fast on one set of frequencies, and
upload slower on another set of frequencies, the DSLAMs do the opposite,
two modems won't even think about talking to each other.

Any thoughts?

Perhaps if you explain what you're actually trying to achieve it might
help ...

On 14 Aug, 22:19, Andy Burns wrote:
When you say "ADSL modem" do you mean a USB modem or an Ethernet router?
(alternatively I suppose you could mean an ethernet modem, but I'll
assume you don't for now).

The ADSL modem will have an ethernet port.

Perhaps if you explain what you're actually trying to achieve it might
help ...

It would be easier if I could draw this ... I'll have a go

existing embedded system in remote location
|
| -- ethernet cable
|
ADSL modem
|
| -- short length of twisted pair
|
the device I hope you can advise me on
|
| -- ethernet cable
|
laptop

The embedded system has an ethernet port and an IP address (may be
fixed or via DHCP). The ethernet port is connected to the ADSL modem.
In normal use the ADSL modem will be connected either to an ordinary
BT phone line with DSL or to a private DSL network. Either way it's
connected to a DSLAM. The upshot of this is that a server app can send
messages to the embedded system via TCP/IP. So far so good.

But this is for development, production testing, installation/
commissioning, and maintenance. I need to be able to exercise the
embedded system/ADSL modem combination in isolation, without
connecting it to a real phone line. Using a laptop I want to be able
to send the same TCP or UDP packets that the server can send, and have
them arrive at the ADSL modem attached to the embedded device, just as
if the embedded embedded device were connected to the DSLAM. This will
mean either writing some software or running the server app on the
laptop, but I know how to do that bit.

On 14/08/2008 23:35, wrote:

The embedded system has an ethernet port and an IP address (may be
fixed or via DHCP). The ethernet port is connected to the ADSL modem.
In normal use the ADSL modem will be connected either to an ordinary
BT phone line with DSL or to a private DSL network. Either way it's
connected to a DSLAM. The upshot of this is that a server app can send
messages to the embedded system via TCP/IP. So far so good.

But this is for development, production testing, installation/
commissioning, and maintenance. I need to be able to exercise the
embedded system/ADSL modem combination in isolation, without
connecting it to a real phone line.

I still don't see what is achieved by connecting it to something other
than a real ADSL enabled phone line, it's not as if it's expensive to do
that, then send the packets to your embeded device via the Internet.

Using a laptop I want to be able
to send the same TCP or UDP packets that the server can send,

At the base layer these are ATM packets, containing PPoA (or PPoE)
containing IP packets

and have
them arrive at the ADSL modem attached to the embedded device, just as
if the embedded embedded device were connected to the DSLAM. This will
mean either writing some software or running the server app on the
laptop, but I know how to do that bit.

what you need is either an actual DSLAM (expensive, not portable) or a
DSLAM simulator such as

http://www.aimsint.com/products1.php

Probably still not cheap.

On 15 Aug, 00:02, Andy Burns wrote:
what you need is either an actual DSLAM (expensive, not portable) or a
DSLAM simulator such as

http://www.aimsint.com/products1.php

Thanks. I hadn't seen these. Looks very useful and may be a way
forward. I'll give them a call tomorrow (er, later today...)

On 15/08/2008 00:16, wrote:

On 15 Aug, 00:02, Andy Burns wrote:
what you need is either an actual DSLAM (expensive, not portable) or a
DSLAM simulator such as

http://www.aimsint.com/products1.php

Thanks. I hadn't seen these. Looks very useful and may be a way
forward. I'll give them a call tomorrow (er, later today...)

There are other ADSL simulators if you search.

If you were developing the ADSL modem itself I could understand why
you'd want to do this, but since you're apparently developing the system
that connects via ethernet to an existing ADSL modem, I still can't see
what benefit you get from doing this, compared to just using an actual
ADSL line via the Internet?

Andy Burns wrote:
On 15/08/2008 00:16, wrote:

On 15 Aug, 00:02, Andy Burns wrote:
what you need is either an actual DSLAM (expensive, not portable) or a
DSLAM simulator such as

http://www.aimsint.com/products1.php

Thanks. I hadn't seen these. Looks very useful and may be a way
forward. I'll give them a call tomorrow (er, later today...)

There are other ADSL simulators if you search.

If you were developing the ADSL modem itself I could understand why
you'd want to do this, but since you're apparently developing the system
that connects via ethernet to an existing ADSL modem, I still can't see
what benefit you get from doing this, compared to just using an actual
ADSL line via the Internet?

My thoughts exactly. rent a secind phone line/brodaband and put the eqpt
under test on that with a normal BT type internet access thing.

On Fri, 15 Aug 2008 04:23:38 UTC, The Natural Philosopher
wrote:

My thoughts exactly. rent a secind phone line/brodaband and put the eqpt
under test on that with a normal BT type internet access thing.

The OP mentioned a laptop so I suspect he wants/needs to go to
different locations.

--
Regards
Dave Saville

NB Remove nospam. for good email address

On 15/08/2008 08:59, Dave Saville wrote:

On Fri, 15 Aug 2008 04:23:38 UTC, The Natural Philosopher
wrote:

My thoughts exactly. rent a secind phone line/brodaband and put the eqpt
under test on that with a normal BT type internet access thing.

The OP mentioned a laptop so I suspect he wants/needs to go to
different locations.

All the same, I doubt there'd be a need to go to a location where there
isn't an ADSL enabled phone line (or the equipment can't work) and he
could use a dial-up or 3G connection from the laptop to connect to the
Internet and then connect back to the equipment (assuming no NAT by the
ISP of course).

In message
,
writes
On 14 Aug, 22:19, Andy Burns wrote:
When you say "ADSL modem" do you mean a USB modem or an Ethernet router?
(alternatively I suppose you could mean an ethernet modem, but I'll
assume you don't for now).

The ADSL modem will have an ethernet port.

Perhaps if you explain what you're actually trying to achieve it might
help ...

It would be easier if I could draw this ... I'll have a go

It sounds like you want to be able to demo/test the remote system
without having ADSL enabled lines, am I right?

I seem to remember reading in the Efficient Networks manuals that you
could connect a pair of 586x routers in this fashion over up to 8KM of
twisted pair, I.E. a leased or private line.. Might be worth having a
read to see if using one 586x you could emulate a DSLAM for any device
or if it was a special mode that only worked with two 586x routers.
--
Clint Sharp