ppp setup and hardware requirement - PPP

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  1. ppp setup and hardware requirement

    Hi,

    i m wondering how to setup a RAS server in FreeBSD, I m more concerned
    hardware requirement for RAS. The hardware requirement of RAS needs a
    lot of modems and serial com ports in order to make multple connections
    to the server.
    Another way to setup a RAS with security enhancement is use poptop +ppp.
    Does poptop also need to have a lot of modems and com ports?
    Please correct me if my statement is wrong. I think they rely on the
    same hardwares but with different implementation.

    Another question with RAS or poptop+ppp is that when a client dial-in to
    the RAS/poptop server, is the client will be assigned an IP address by
    the RAS/poptop server and the IP is not limited to public, can be a
    class C IP as long as the IP is not conflict with the one already in the
    client's machine?

    Does the following modem cards supported by FreeBSD?
    Netaccess Instant RAS MultiPort Modem Card



    many thanks
    Sam


  2. Re: ppp setup and hardware requirement

    sam writes:
    > i m wondering how to setup a RAS server in FreeBSD, I m more concerned
    > hardware requirement for RAS. The hardware requirement of RAS needs a
    > lot of modems and serial com ports in order to make multple
    > connections to the server.
    > Another way to setup a RAS with security enhancement is use poptop
    > +ppp. Does poptop also need to have a lot of modems and com ports?
    > Please correct me if my statement is wrong. I think they rely on the
    > same hardwares but with different implementation.


    They're quite different. And it's not an either/or condition.

    A regular old RAS server would, as you suggest, have a large number of
    serial ports and modems (or ISDN TAs). Modern RAS servers tend to
    have integrated high-density digital modems and substantial management
    and telecom features, so anything constructed with a UNIX-like system
    with external modems would be greatly inferior, but might serve the
    purpose in some cases.

    "Poptop" is a PPTP implementation. PPTP is a Microsoft-proprietary
    tunneling protocol for PPP. You might use that with a pile of modems
    (e.g., an application where the RAS tunnels PPP sessions back to a
    central site over an internal network), or you might use it as a
    central site device, or you might use it with no modems at all
    (VPN-like tunneling).

    It's impossible to tell what you're trying to do here.

    > Another question with RAS or poptop+ppp is that when a client dial-in
    > to the RAS/poptop server, is the client will be assigned an IP address
    > by the RAS/poptop server and the IP is not limited to public, can be a
    > class C IP as long as the IP is not conflict with the one already in
    > the client's machine?


    IP address assignment has little or nothing to do with how the PPP
    session is set up. You can assign addresses any way that is
    convenient for you.

    > Does the following modem cards supported by FreeBSD?
    > Netaccess Instant RAS MultiPort Modem Card


    You'll need to check with freebsd.org or with the manufacturer of that
    product.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

  3. Re: ppp setup and hardware requirement

    James Carlson wrote:
    > sam writes:
    >
    >>i m wondering how to setup a RAS server in FreeBSD, I m more concerned
    >>hardware requirement for RAS. The hardware requirement of RAS needs a
    >>lot of modems and serial com ports in order to make multple
    >>connections to the server.
    >>Another way to setup a RAS with security enhancement is use poptop
    >>+ppp. Does poptop also need to have a lot of modems and com ports?
    >>Please correct me if my statement is wrong. I think they rely on the
    >>same hardwares but with different implementation.

    >
    >
    > They're quite different. And it's not an either/or condition.
    >
    > A regular old RAS server would, as you suggest, have a large number of
    > serial ports and modems (or ISDN TAs). Modern RAS servers tend to
    > have integrated high-density digital modems and substantial management
    > and telecom features, so anything constructed with a UNIX-like system
    > with external modems would be greatly inferior, but might serve the
    > purpose in some cases.
    >
    > "Poptop" is a PPTP implementation. PPTP is a Microsoft-proprietary
    > tunneling protocol for PPP. You might use that with a pile of modems
    > (e.g., an application where the RAS tunnels PPP sessions back to a
    > central site over an internal network), or you might use it as a
    > central site device, or you might use it with no modems at all
    > (VPN-like tunneling).
    >
    > It's impossible to tell what you're trying to do here.
    >

    Thanks for the replies.
    I want to setup poptop in freebsd to serve as a secure Remote Access
    Server for me to dail-in while I m at distance with out Internet access.
    I m wondering if one modem at the Poptop server can handle multiple
    connections or not.

    Thanks
    sam

    >
    >>Another question with RAS or poptop+ppp is that when a client dial-in
    >>to the RAS/poptop server, is the client will be assigned an IP address
    >>by the RAS/poptop server and the IP is not limited to public, can be a
    >>class C IP as long as the IP is not conflict with the one already in
    >>the client's machine?

    >
    >
    > IP address assignment has little or nothing to do with how the PPP
    > session is set up. You can assign addresses any way that is
    > convenient for you.
    >
    >
    >>Does the following modem cards supported by FreeBSD?
    >> Netaccess Instant RAS MultiPort Modem Card

    >
    >
    > You'll need to check with freebsd.org or with the manufacturer of that
    > product.
    >



  4. Re: ppp setup and hardware requirement

    sam writes:
    > Thanks for the replies.
    > I want to setup poptop in freebsd to serve as a secure Remote Access
    > Server for me to dail-in while I m at distance with out Internet
    > access.
    > I m wondering if one modem at the Poptop server can handle multiple
    > connections or not.


    Still too little information to go on.

    A typical usage pattern would be to have a PPTP (or L2TP) server
    placed at some central site with access to both the Internet and some
    private network. You then dial into any regular Internet service
    provider and create a PPTP tunnel back to that central site.

    In this case, there are two instances of PPTP, and neither has
    anything to do with any modems. The configuration looks something
    like this:

    Mobile Node Central Site

    applications
    |
    TCP/IP <- VPN interface IP--- {network}
    | |
    PPP PPP
    | |
    PPTP PPTP
    | |
    IP <- Internet |
    | |
    PPP IP
    | |
    +--modem--ISP---{ The Internet }------------+

    I suspect that's the most common usage.

    Another possibility is that the ISP is in on the game, and has some
    sort of relationship with the operator of the machine at the central
    site. In this case, you just dial in with regular PPP over a regular
    modem (no PPTP), and the ISP tunnels it back to the central site over
    PPTP. I sort of doubt that this is ever done, as it means handing
    over the keys to your local network to that ISP, but I'm sure someone
    can prove me wrong. ;-}

    But, without more information, it's not at all clear what you're
    trying to do.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

  5. Re: ppp setup and hardware requirement

    James Carlson wrote:
    > sam writes:
    >
    >>Thanks for the replies.
    >>I want to setup poptop in freebsd to serve as a secure Remote Access
    >>Server for me to dail-in while I m at distance with out Internet
    >>access.
    >>I m wondering if one modem at the Poptop server can handle multiple
    >>connections or not.

    >
    >
    > Still too little information to go on.
    >
    > A typical usage pattern would be to have a PPTP (or L2TP) server
    > placed at some central site with access to both the Internet and some
    > private network. You then dial into any regular Internet service
    > provider and create a PPTP tunnel back to that central site.
    >
    > In this case, there are two instances of PPTP, and neither has
    > anything to do with any modems. The configuration looks something
    > like this:
    >
    > Mobile Node Central Site
    >
    > applications
    > |
    > TCP/IP <- VPN interface IP--- {network}
    > | |
    > PPP PPP
    > | |
    > PPTP PPTP
    > | |
    > IP <- Internet |
    > | |
    > PPP IP
    > | |
    > +--modem--ISP---{ The Internet }------------+
    >
    > I suspect that's the most common usage.
    >
    > Another possibility is that the ISP is in on the game, and has some
    > sort of relationship with the operator of the machine at the central
    > site. In this case, you just dial in with regular PPP over a regular
    > modem (no PPTP), and the ISP tunnels it back to the central site over
    > PPTP. I sort of doubt that this is ever done, as it means handing
    > over the keys to your local network to that ISP, but I'm sure someone
    > can prove me wrong. ;-}
    >
    > But, without more information, it's not at all clear what you're
    > trying to do.


    Thanks for the drawing. In my case, the uesr won't have internect
    connection at a remote size, only a phone line is available. I want to
    setup a central server(eg. RAS as old tech) to allow remote user dial-in
    over serial phone lines. The RAS server can handle that. I don't know
    whether poptop must use modem to service dial-in connection request.

    Correct me if I m wrong, I think pppd should be used for serving dial-in
    request from phone lines, then pppd hand over the connection to poptop
    server after the user successfully dialed-in.

    Thanks
    sam


  6. Re: ppp setup and hardware requirement

    sam writes:
    > Thanks for the drawing. In my case, the uesr won't have internect
    > connection at a remote size, only a phone line is available. I want to
    > setup a central server(eg. RAS as old tech) to allow remote user
    > dial-in over serial phone lines. The RAS server can handle that. I
    > don't know whether poptop must use modem to service dial-in connection
    > request.


    In that case, I see no reason at all to be using PPTP. The whole
    point of PPTP is to tunnel PPP over an internet, and that implies that
    both ends of the virtual PPP connection have internet connectivity by
    other means.

    > Correct me if I m wrong, I think pppd should be used for serving
    > dial-in request from phone lines, then pppd hand over the connection
    > to poptop server after the user successfully dialed-in.


    I think you should just be using mgetty+pppd on that dial-in server,
    and regular IP forwarding from there. I don't see what PPTP has to do
    with the issue.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

  7. Re: ppp setup and hardware requirement

    James Carlson wrote:
    > sam writes:
    >
    >>Thanks for the drawing. In my case, the uesr won't have internect
    >>connection at a remote size, only a phone line is available. I want to
    >>setup a central server(eg. RAS as old tech) to allow remote user
    >>dial-in over serial phone lines. The RAS server can handle that. I
    >>don't know whether poptop must use modem to service dial-in connection
    >>request.

    >
    >
    > In that case, I see no reason at all to be using PPTP. The whole
    > point of PPTP is to tunnel PPP over an internet, and that implies that
    > both ends of the virtual PPP connection have internet connectivity by
    > other means.
    >
    >
    >>Correct me if I m wrong, I think pppd should be used for serving
    >>dial-in request from phone lines, then pppd hand over the connection
    >>to poptop server after the user successfully dialed-in.

    >
    >
    > I think you should just be using mgetty+pppd on that dial-in server,
    > and regular IP forwarding from there. I don't see what PPTP has to do
    > with the issue.
    >


    Another question is, do I need a null-modem or fax-modem for the pppd
    server? can a modem be used to serve multiple connections at the same time?

    Thanks
    sam


  8. Re: ppp setup and hardware requirement

    sam writes:
    > Another question is, do I need a null-modem or fax-modem for the pppd
    > server?


    You need a modem if someone is going to dial into that instance of
    pppd over a telephone line. If there's a telephone line, then you'll
    need a modem to communicate over it. If there's no telephone line,
    then no modem is required.

    I (still) don't know whether the deployment you're working on involves
    a modem at all, or where the modem might be, so I can't really give a
    helpful answer.

    Pppd doesn't assume the existence of a modem, so no "null-modem" is
    needed.

    > can a modem be used to serve multiple connections at the same
    > time?


    A single modem on a single telephone line? I don't understand that
    question.

    If you're talking about TCP connections, a PPP link is like any other
    network interface, such as an Ethernet. You can have as many TCP
    connections as you like over it. PPP neither knows nor cares about
    the TCP (or higher-level) connections in use.

    If you're talking about handling telephone calls, then I'm very
    confused. How do you propose that a single modem with a single
    telephone line could handle more than one telephone call at a time?

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

  9. Re: ppp setup and hardware requirement

    sam writes:

    ]Hi,

    ]i m wondering how to setup a RAS server in FreeBSD, I m more concerned
    ]hardware requirement for RAS. The hardware requirement of RAS needs a
    ]lot of modems and serial com ports in order to make multple connections
    ]to the server.

    You need as many modems and phone lines as you want to have people
    connected at once. For one person only one phone line and modem is needed.
    For 100, you need 100. This has nothing whatsoever to do with RAS, it is a
    limitation of how telephones work.

    ]Another way to setup a RAS with security enhancement is use poptop +ppp.
    ]Does poptop also need to have a lot of modems and com ports?
    ]Please correct me if my statement is wrong. I think they rely on the
    ]same hardwares but with different implementation.

    ]Another question with RAS or poptop+ppp is that when a client dial-in to
    ]the RAS/poptop server, is the client will be assigned an IP address by
    ]the RAS/poptop server and the IP is not limited to public, can be a
    ]class C IP as long as the IP is not conflict with the one already in the
    ]client's machine?

    No. You are only allowed to assign IP addresses you have the right to
    assign. If you want private IP addresses, use the ranges 192.168.x.x or
    10.x.x.x DO NOT assign other IP addresses you have not gotten explicit
    permission from your counties IP assigners for.

    If you use those private Ip addresses, they will not work on the net. You
    must use NAT then.


    ]Does the following modem cards supported by FreeBSD?
    ] Netaccess Instant RAS MultiPort Modem Card

  10. Re: ppp setup and hardware requirement

    sam writes:

    ]Thanks for the replies.
    ]I want to setup poptop in freebsd to serve as a secure Remote Access
    ]Server for me to dail-in while I m at distance with out Internet access.
    ]I m wondering if one modem at the Poptop server can handle multiple
    ]connections or not.

    1 modem on one phone line = 1 connection.


    If all you want is to be able to dial in to your own machine whan you are
    away from home, than RAS, poptop,... are all irrelevant AFAICS.
    You want something which will answer the phone when it rings (under Linux
    and prob RSA this is mgetty) and hands off to something which will
    establish the connection (eg pppd)



  11. Re: ppp setup and hardware requirement

    sam writes:

    ]James Carlson wrote:
    ]> sam writes:
    ]>
    ]>>Thanks for the drawing. In my case, the uesr won't have internect
    ]>>connection at a remote size, only a phone line is available. I want to
    ]>>setup a central server(eg. RAS as old tech) to allow remote user
    ]>>dial-in over serial phone lines. The RAS server can handle that. I
    ]>>don't know whether poptop must use modem to service dial-in connection
    ]>>request.
    ]>
    ]>
    ]> In that case, I see no reason at all to be using PPTP. The whole
    ]> point of PPTP is to tunnel PPP over an internet, and that implies that
    ]> both ends of the virtual PPP connection have internet connectivity by
    ]> other means.
    ]>
    ]>
    ]>>Correct me if I m wrong, I think pppd should be used for serving
    ]>>dial-in request from phone lines, then pppd hand over the connection
    ]>>to poptop server after the user successfully dialed-in.
    ]>
    ]>
    ]> I think you should just be using mgetty+pppd on that dial-in server,
    ]> and regular IP forwarding from there. I don't see what PPTP has to do
    ]> with the issue.
    ]>

    ]Another question is, do I need a null-modem or fax-modem for the pppd
    ]server? can a modem be used to serve multiple connections at the same time?

    No, No. No.

    A null modem is not a modem. It is the absence of a modem. If you want to
    receive or send faxes then you need a fax modem, otherwise not. A modem can
    only service one phone line at a time. Just as you cannot telephone 10
    people at the same time on one phone, one modem can only handle one call at
    a time.


  12. Re: ppp setup and hardware requirement

    sam writes:
    >
    >Another question is, do I need a null-modem or fax-modem for the pppd
    >server?
    >


    You're misusing the names for things, and this can cause confusion.
    You should probably describe what you're thinking of, rather than
    apply the wrong name.

    "Null-modem" refers to a type of cable, not a type of modem. You
    probably meant to ask about a "data modem". (i.e. a modem that lacks
    fax capabilities)

    Most fax modems that you can buy off-the-shelf from computer stores
    also support ordinary data calls as well as fax calls. Pppd would
    not make use of the fax capabilities of a fax modem, only the data
    capabilities. Mgetty would be able to use both capabilities, by
    invoking fax software when the modem indicates that an incoming call
    is from a fax machine, and by invoking pppd when the modem indicates
    that the incoming call is a data call.

    So the answer to your question is that either type of modem (fax or
    data) can work with pppd.

    >
    >can a modem be used to serve multiple connections at the same time?
    >


    The ordinary modems that you would buy off-the-shelf from computer
    stores (which connect to ordinary phone lines like the one you have
    at your home) cannot serve multiple phone calls at the same time.
    They can only 'talk' to one other modem through the phone line.

    There are expensive modems that attach to special telephone company
    trunk lines rather than an ordinary phone line. The trunk line can
    carry multiple phone calls, and these modems can also support multiple
    phone calls. However, the connection to the computer would be through
    multiple RS232 ports (one for each phone call the modem and trunk line
    can support), or through a network interface that behaves like a device
    known as a "terminal server". So this kind of modem would look to pppd
    as if the computer had 24 ordinary modems connected to 24 serial ports.


    I think this may clear up some of the confusion that I've been seeing
    in this discussion.

    -Greg
    --
    Do NOT reply via e-mail.
    Reply in the newsgroup.

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