Digital Subscriber Line question about "routers" and PPP

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Subject Author Date
question about "routers" and PPP jameshanley39@yahoo.co.uk 11-12-07
Posted by jameshanley39@yahoo.co.uk on November 12, 2007, 10:53 am
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I`ve noticed that for user,pass PPP(whether in the router or in
windows) seems to use a username with an @ like

username@adsl.provider.com

is that always the case?
anybody know why?

I am in the UK, the ones I Have seen have all been PPPoA. Is it only
PPPoA that have that?

With some USB modems the PPP is done in windows. Is that still
PPPoA ?
(I am guessing so, since isn`t A for ATM , which is to do with the
service provider)

Yet This link here
http://www.udel.edu/topics/connect/ppp/XP/index.html
shows a windows screen that suggests that USB modems use PPPoE, and
that the username does not have an @.
(windows screen obtained by ctrl panel..network connections..new
network connection wiz..connect to internet...manually)
I can guess that they use PPPoA in UK, and PPPoE in america.

Is it also the case that PPPoA tends to use an @, and PPPoE tends not
to ?

Is there a name for a device whose function is PPP? I am guessing
not. I guess it is another function they bundle into the device
called a "home router". I know with dial up modems it is always
windows that does it. And I have heard that a router can be put in
bridge mode and then PPP can be done in windows. Is that right?

TIA


Posted by Doug McIntyre on November 12, 2007, 1:07 pm
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>I`ve noticed that for user,pass PPP(whether in the router or in
>windows) seems to use a username with an @ like

>username@adsl.provider.com

>is that always the case?

No, it can be anything.

>anybody know why?

Why not?

Two things.
Realms and that usernames for many services look like email addresses anyway.


>I am in the UK, the ones I Have seen have all been PPPoA. Is it only
>PPPoA that have that?

No, anything that authenticates can have any username they wish.

>With some USB modems the PPP is done in windows. Is that still
>PPPoA ?

It could be.

>(I am guessing so, since isn`t A for ATM , which is to do with the
>service provider)

Technically the A in PPPoA is for AAL5, which is one layer ontop of ATM.
Alot of people commonly put that back as ATM.

>Yet This link here
>http://www.udel.edu/topics/connect/ppp/XP/index.html
>shows a windows screen that suggests that USB modems use PPPoE, and
>that the username does not have an @.

Yes, there could be USB modems that require PPP authentication
(ie. Intel 3200 is one discontinued one. Not too familure with the
batch out there). Or, they could be simple bridges, and depend on
Windows built-in PPPoE to handle those functions.

Either way, the username can be anything the service provider wants to run.

>(windows screen obtained by ctrl panel..network connections..new
>network connection wiz..connect to internet...manually)
>I can guess that they use PPPoA in UK, and PPPoE in america.

I run almost all PPPoA in the US, as do most ISPs using Qwest as a
facilities provider.

>Is it also the case that PPPoA tends to use an @, and PPPoE tends not
>to ?

No. There's no correlation.

>Is there a name for a device whose function is PPP? I am guessing
>not. I guess it is another function they bundle into the device
>called a "home router". I know with dial up modems it is always
>windows that does it. And I have heard that a router can be put in
>bridge mode and then PPP can be done in windows. Is that right?

eh? Lost me alot on this one.

Alot of what you are asking depends alot on the service provider, and
what they can provide you.
You're trying to generalize too far.



Posted by jameshanley39@yahoo.co.uk on November 12, 2007, 7:22 pm
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<snip>
> This link here
> >http://www.udel.edu/topics/connect/ppp/XP/index.html
> >shows a windows screen that suggests that USB modems use PPPoE, and
> >that the username does not have an @.
>
> Yes, there could be USB modems that require PPP authentication
> (ie. Intel 3200 is one discontinued one. Not too familure with the
> batch out there). Or, they could be simple bridges, and depend on
> Windows built-in PPPoE to handle those functions.

<snip>
if an ISP uses PPPoA e.g. if using a "Router" one selects PPPoA and it
connects.
Then, if one was to change the router for a USB bridge, and connect
via windows.

Would the built in windows thing be PPPoA or PPPoE?

PPP is something from the DSL world. A plain router would just do
routing and not know about PPP. Router is really a function. The boxes
people have at home act as a router, bridge, modem, dhcp server. So,
since you know the DSL world.. I ask, is there a name for a device
that does PPP?


Posted by Doug McIntyre on November 14, 2007, 6:01 pm
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>if an ISP uses PPPoA e.g. if using a "Router" one selects PPPoA and it
>connects.
>Then, if one was to change the router for a USB bridge, and connect
>via windows.
>Would the built in windows thing be PPPoA or PPPoE?


Bridge is such a generic term. Is it really a bridge? Or is it a modem?
There are both types of boxes out there. Both terms are abused so often
as to what they actually are. Maybe thats part of some issue, when
people commonly call anything that terminates the signal a
router/bridge/modem depending on what they are used to, not depending
on what it actually is, it tends to get a bit confusing..
(ie. a router will make layer-3 routing decisions across two or more
interfaces. a bridge will pass layer-2 packets between two interfaces.
A modem generally has one interface and some method to put the data back
out somehow, serial, usb, whatever). A router or bridge would "contain"
a modem as part of its hardware, although you won't see it.

I'm going to assume that everything is ATM here for the most part.
Some ISP networks are built on pure IP now-a-days, although the
classic DSL since the ANSI/ITU standards came along was built on ATM.

A DSL USB bridge would imply that it takes the DSL signal in,
reassembles the ATM cells into regular Ethernet frames. Then on the
USB interface, it would present an Ethernet NIC interface to the OS.
The OS then if using PPP, implement the PPPoE stack on the Ethernet
interface that pops up, do the phases of PPP and get online.
A Zoom 5615 is this sort of device.

a DSL USB modem would imply that it takes the DSL signal in, and
presents a modem interface to the OS over the USB interface. Typically
an ISP running this sort of configuration could be talking PPPoA or
PPPoE to the far end, because there's no Ethernet involved, virtual or
otherwise. You can not talk PPPoA over ethernet (ie. like the DSL
Bridge I discussed above), it *has* to be over some sort of ATM
interface, which the DSL USB modem can provide. In this setup, you
get a modem showing up on your OS, you dial using it with normal
Dialup Networking, usually dialing the ATM VPI/VCI to talk with as the
phone number and plugging in your ISP username and password in the
normal fields.
A Zoom 5510 or Intel 3200 is this type of device.

>PPP is something from the DSL world. A plain router would just do
>routing and not know about PPP. Router is really a function. The boxes
>people have at home act as a router, bridge, modem, dhcp server. So,
>since you know the DSL world.. I ask, is there a name for a device
>that does PPP?

PPP is from long long before DSL was around, we should be coming up on
20 years pretty soon. I was doing PPP over analog modems in 1993.
Such an easier solution than SL\IP. PPP is also used in many other
applications. Many T1s run PPP as their layer-2 protocol. I've seen it
used over X.25 networks. Appletalk and IPX protocols can run over it.
PPP was an existing solution adapted by DSL to provide the same
benefits. The design of PPP was obviously well done to provide such
extendibility for so long.

A plain router has had PPP in it for some time. cisco IOS introduced
it in 10.0 IIRC, somewhere around 1994. A router in classic sense just
is a device that can make layer-3 protocol decisions between two or
more interfaces.

Most DSL routers have had PPP stacks built into them. There have been
a few (lower-end than normal Speedstream comes to mind) that have not,
even though PPP usage in the DSL world was long established. A few
years ago, customers coming to me with weird random devices asking
about compatibility, I'd have to read the tech specs carefully to see
if they did support PPPoA or not. Sometimes they did, sometimes not.

There is not a designation of a network device that says it can talk
PPP, although most (if not all currently shipping ones) DSL routers
can do so. PPP is just one of many 100's if not 1000's of
features/protocols a router has to deal with.

Any non-DSL network router would have the PPP protocol in it from
before the time that DSL existed. (ie. cisco, juniper, etc).

So, no there is nothing that says a box can do PPP other than its tech specs.

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