"Reversed" modem pool?

Hi all,

I'd like to set up what I can only describe as the opposite of what's
often referred to as a modem pool. Instead of having several modems set
up to accept incoming calls, I'd like to set up the reversed scenario in
which the modems can be used for dialing out. My reasons for doing this are:

1. I have a limited number of modems and analogue lines.
2. I have a *lot* of dial-up peers - for argument's sake, let's say
around 10 to 20 times as many as I have modems.
3. Most of the peers are only connected to on a rather occasional
basis, and not for extended periods.
4. There is, however, a large chance that more than one connection
needs to be open at any one time (hence the multiple modems).
5. Users are currently forced to use modems on/in their workstations.
Not only is this a pain for them to configure, it's pretty awful
for security.

My thinking is that centralising the dial-up connections in this manner
will allow more efficient use of the available lines, enhance security
and simplify configuration. Dial-on-demand and a bit of routing should
make dialing in much simpler, if not transparent, for the end user.

Having done a fair bit of research I've come across a number of possible
tools for the job and have stuff like dial-on-demand working fine with
pppd and wvdial. It's just a matter of setting up the dynamic modem
"sharing" part (and of course, googling on "modem sharing" returns
plently of matches describing how to masquerade your Internet connection
which is of little help). I'm toying with the idea of using if-up
scripts to point a symlink at the next modem after dialing, but it all
seems a bit hairy to me and it seems there must be a more elegant solution.

The question is, if it were not obvious already: how would one go about
setting this up properly? I can imagine it's been done before, but
either it's not been documented or my searching's not up to scratch!

Any ideas would be most appreciated.


Cheers,

Steve Maddison

Steve,

One question your model does not seem to address is the "on demand"
issue. Your peers will always be there when scheduled? If so, I think
you have a very unique user base.

One thing that might help you is a call-back feature. The user dials
from their workstation, logs in, and then the pool modem hangs up and
dials that user back based on their saved login credentials. In other
words, each user would be required to be at one specific phone number,
the way things normally work.

A configuration script (eg an InstallShield package or similar) would
allow for easy configuration, because everyone would call the same
number. Put it on a CD, burn a few dozen copies and hand them out.
You would in effect become an ISP, but you would have the call-back
feature which increases security.

You could also look into a PGP-style signature per user or just go with
encrypted connections with a list of trusted keys on your pool side.

Steve Maddison wrote:
> Hi all,
>
> I'd like to set up what I can only describe as the opposite of what's
> often referred to as a modem pool. Instead of having several modems set
> up to accept incoming calls, I'd like to set up the reversed scenario in
> which the modems can be used for dialing out. My reasons for doing this are:
>
> 1. I have a limited number of modems and analogue lines.
> 2. I have a *lot* of dial-up peers - for argument's sake, let's say
> around 10 to 20 times as many as I have modems.
> 3. Most of the peers are only connected to on a rather occasional
> basis, and not for extended periods.
> 4. There is, however, a large chance that more than one connection
> needs to be open at any one time (hence the multiple modems).
> 5. Users are currently forced to use modems on/in their workstations.
> Not only is this a pain for them to configure, it's pretty awful
> for security.
>
> My thinking is that centralising the dial-up connections in this manner
> will allow more efficient use of the available lines, enhance security
> and simplify configuration. Dial-on-demand and a bit of routing should
> make dialing in much simpler, if not transparent, for the end user.
>
> Having done a fair bit of research I've come across a number of possible
> tools for the job and have stuff like dial-on-demand working fine with
> pppd and wvdial. It's just a matter of setting up the dynamic modem
> "sharing" part (and of course, googling on "modem sharing" returns
> plently of matches describing how to masquerade your Internet connection
> which is of little help). I'm toying with the idea of using if-up
> scripts to point a symlink at the next modem after dialing, but it all
> seems a bit hairy to me and it seems there must be a more elegant solution.
>
> The question is, if it were not obvious already: how would one go about
> setting this up properly? I can imagine it's been done before, but
> either it's not been documented or my searching's not up to scratch!
>
> Any ideas would be most appreciated.
>
>
> Cheers,
>
> Steve Maddison

"Steve Maddison" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)

> I'd like to set up what I can only describe as the opposite of what's
> often referred to as a modem pool. Instead of having several
> modems set up to accept incoming calls, I'd like to set up the
> reversed scenario in which the modems can be used for dialing out.
....
> It's just a matter of setting up the dynamic modem "sharing" part
> (and of course, googling on "modem sharing" returns
> plently of matches describing how to masquerade your Internet
> connection which is of little help).
....
> I can imagine it's been done before, but either it's not been
> documented or my searching's not up to scratch!

I'd say that your searching is deficient, since the Subject: states "modem
pool" yet you're searching for "modem sharing". See if any of the links
returned by http://www.google.com/linux?q=outgoing+%22modem+pool%22 are of
any use to you.

On Mon, 24 Jul 2006 22:30:43 +0200, Steve Maddison <(E-Mail Removed)>
wrote:

> I'd like to set up what I can only describe as the opposite of what's
> often referred to as a modem pool. Instead of having several modems
> set up to accept incoming calls, I'd like to set up the reversed
> scenario in which the modems can be used for dialing out.

This may be completely off-the-wall, but if what you are doing is
periodic batch transfers of data (email, data records, whatever) between
a central "hub" and remote "spokes, you might want to look at UUCP. It
is a little old-fashioned, but works great for that sort of network.


--
-| Bob Hauck
-| A proud member of the unhinged moonbat horde.
-| http://www.haucks.org/

Ken Roberts wrote:
> One question your model does not seem to address is the "on demand"
> issue. Your peers will always be there when scheduled? If so, I
> think you have a very unique user base.

Hi Ken,

The peers in question are on remote networks to which my users must be
able to connect in order to provide support. Most of them are indeed
always listening for connections and those which aren't will be
activated manually (at the remote end) before the user attempts to connect.

What I indeed have not mentioned is what would happen when all modems
are in use and/or a peer is unavailable when someone tries to initiate a
new connection. In this case the connection attempt would fail silently
and the user would have to report the problem.

An alternative would of course be to provide some kind of interface
through which users could select a peer and modem manually, then dial in
and set up routing on behalf of the user. I was however hoping to
automate as much of the process as possible, so an on-demand system
would be preferable.

> One thing that might help you is a call-back feature. The user dials
> from their workstation, logs in, and then the pool modem hangs up
> and dials that user back based on their saved login credentials. In
> other words, each user would be required to be at one specific phone
> number, the way things normally work.

Unfortunately the configuration of the remote peers is solely in the
hands of the administrators of the network in question. We don't have
much (if any) say in what goes on at their end, the rationale being that
the peers (our customers) provide a method of remote access and it's up
to us to make it work.

Thanks for your response,

Steve

Patrick wrote:
> "Steve Maddison" <(E-Mail Removed)> wrote in message
>
>>I can imagine it's been done before, but either it's not been
>>documented or my searching's not up to scratch!
>
> I'd say that your searching is deficient, since the Subject: states "modem
> pool" yet you're searching for "modem sharing". See if any of the links
> returned by http://www.google.com/linux?q=outgoing+%22modem+pool%22 are of
> any use to you.
>

Already tried that, and many other similar search queries. Everything on
modem pools seems to refer to the incoming variety or states briefly
that they can be used for outgoing connections with no further deatils.

BTW, we've no budget for a multi-modem card, as is referred to in many
those of those links, which would seeming do all this automagically.

Cheers,

Steve

Bob Hauck <(E-Mail Removed)> wrote:
> This may be completely off-the-wall, but if what you are doing is
> periodic batch transfers of data (email, data records, whatever) between
> a central "hub" and remote "spokes, you might want to look at UUCP. It
> is a little old-fashioned, but works great for that sort of network.

Oh my goodness. That brings back memories!
Chris

On Tue, 25 Jul 2006 12:08:09 +0100, Chris Davies
<chris-(E-Mail Removed)> wrote:

> Bob Hauck <(E-Mail Removed)> wrote:

>> This may be completely off-the-wall, but if what you are doing is
>> periodic batch transfers of data (email, data records, whatever) between
>> a central "hub" and remote "spokes, you might want to look at UUCP.

> Oh my goodness. That brings back memories!

Solving old problems is sometimes best done with old tech 8->

But after reading his followups it sounds like the OP is doing online
support rather than file transfers so UUCP isn't what he needs at all.


--
-| Bob Hauck
-| A proud member of the unhinged moonbat horde.
-| http://www.haucks.org/

On Mon, 24 Jul 2006 22:30:43 +0200, Steve Maddison <(E-Mail Removed)> wrote:
> I'd like to set up what I can only describe as the opposite of what's
> often referred to as a modem pool. Instead of having several modems set
> up to accept incoming calls, I'd like to set up the reversed scenario in
> which the modems can be used for dialing out. My reasons for doing this are:
> 1. I have a limited number of modems and analogue lines.
> 2. I have a *lot* of dial-up peers - for argument's sake, let's say
> around 10 to 20 times as many as I have modems.
> 3. Most of the peers are only connected to on a rather occasional
> basis, and not for extended periods.
> 4. There is, however, a large chance that more than one connection
> needs to be open at any one time (hence the multiple modems).
> 5. Users are currently forced to use modems on/in their workstations.
> Not only is this a pain for them to configure, it's pretty awful
> for security.
> My thinking is that centralising the dial-up connections in this manner
> will allow more efficient use of the available lines, enhance security
> and simplify configuration. Dial-on-demand and a bit of routing should
> make dialing in much simpler, if not transparent, for the end user.
> Having done a fair bit of research I've come across a number of possible
> tools for the job and have stuff like dial-on-demand working fine with
> pppd and wvdial. It's just a matter of setting up the dynamic modem
> "sharing" part (and of course, googling on "modem sharing" returns
> plently of matches describing how to masquerade your Internet connection
> which is of little help). I'm toying with the idea of using if-up
> scripts to point a symlink at the next modem after dialing, but it all
> seems a bit hairy to me and it seems there must be a more elegant solution.
> The question is, if it were not obvious already: how would one go about
> setting this up properly? I can imagine it's been done before, but
> either it's not been documented or my searching's not up to scratch!
> Any ideas would be most appreciated.

I used to do this all the time with a terminal server and kermit.

We had a pool of modems attached to a terminal server that were
intitially set up as incoming connections to the terminal server, and
then users would connect to various systems in the network from it.
As it turned, it worked in the reverse just fine. This was on a
DECserver200MC, and the protocol was LAT (for incoming connections) or
reverse LAT (for outgoing).

This should still be possible in the Unix/Linux world using a terminal
server and TCP/IP.

Talk to the people at Cyclades
http://www.cyclades.com
about their TS-series, or any other company that makes terminal
servers. (Nowadays, their main business is data center management of
multiple serial consoles, but I think that terminal servers can still
be used the way you want to.) The terminal server would own all the
modems, and appear as another system on your network.

Make sure you explain exactly what you want to do, especially that
users at their desktops want to establish ppp connections through the
modems.

You might need some scripting on a central system to give out the
modems in the pool (for example, a web page on some server in your
system that keeps track of who is using which modem).

It's not quite standard, but I think it's doable.

--
Dale Dellutri <(E-Mail Removed)> (lose the Q's)

Dale Dellutri wrote:
> Talk to the people at Cyclades
> http://www.cyclades.com
> about their TS-series, or any other company that makes terminal
> servers. (Nowadays, their main business is data center management of
> multiple serial consoles, but I think that terminal servers can still
> be used the way you want to.) The terminal server would own all the
> modems, and appear as another system on your network.

I'd never have come up with it, but that sounds very much like what I'm
trying to achieve. Completely different way of getting there, of course,
but definitely worth a look - thanks.

> You might need some scripting on a central system to give out the
> modems in the pool (for example, a web page on some server in your
> system that keeps track of who is using which modem).

I've resigned myself to there being at least some scripting of this kind
involved. The thing is, if I'm building a web page anyway, I might as
well just script the whole lot and let the users switch their
connections on and off when they need them. Shame about the (lack of)
automation then, but even this scenario is an order of mangitude better
than the current set-up.

Thanks for the input,

Steve