Establishing a Point to Point connection over radio networks - PPP

This is a discussion on Establishing a Point to Point connection over radio networks - PPP ; Hi All, I need to establish a point to point connection between two VHF Radios. MY idea is to do data transfer between the two. I have written an application to transfer data between the two, but it works only ...

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Thread: Establishing a Point to Point connection over radio networks

  1. Establishing a Point to Point connection over radio networks

    Hi All,

    I need to establish a point to point connection between two VHF
    Radios. MY idea is to do data transfer between the two. I have written
    an application to transfer data between the two, but it works only on
    full duplex lines. Is there any protocol standard for file transfer on
    half-duplex lines.

    Is it possible for me to establish a PPP connection. The radios have a
    serial interface (RS 232C) which can be connected to a Linux PC. Can i
    run PPPD on this ?.Will it work on half-duplex radios ?
    Any help is appreciated.
    Thanks
    Vanitha

  2. Re: Establishing a Point to Point connection over radio networks

    In article <15faa2ac.0408141852.4d82b501@posting.google.com>, Vanitha wrote:
    >I need to establish a point to point connection between two VHF
    >Radios.


    >The radios have a serial interface (RS 232C) which can be connected
    >to a Linux PC. Can i run PPPD on this ?.Will it work on half-duplex
    >radios ?


    I suppose so, but the latency might be a problem. A lot might depend on
    the protocols you are using - for example IP has a maximum data window
    of 65k, meaning you can only send a maximum of 65k before you need an
    acknowledgement that the data has been received. Most data transfer
    protocols have similar limitations.

    There _used_ to be a HAM-HOWTO that might contain some hints if you can
    find a copy. There is also the AX25-HOWTO that isn't to out of date.

    Old guy

  3. Re: Establishing a Point to Point connection over radio networks

    ibuprofin@painkiller.example.tld (Moe Trin) writes:

    > In article <15faa2ac.0408141852.4d82b501@posting.google.com>, Vanitha wrote:
    > >I need to establish a point to point connection between two VHF
    > >Radios.

    >
    > >The radios have a serial interface (RS 232C) which can be connected
    > >to a Linux PC. Can i run PPPD on this ?.Will it work on half-duplex
    > >radios ?

    >
    > I suppose so, but the latency might be a problem.


    Perhaps. Technically, PPP does require a full-duplex connection.
    What this really means is that there's nothing in PPP that will
    support half-duplex operation; there's no "go ahead" or "poll" signals
    that you could use. If your half-duplex system doesn't require those
    sorts of signals -- if each side can send when it wants -- then at
    least that's not a problem.

    > A lot might depend on
    > the protocols you are using - for example IP has a maximum data window
    > of 65k, meaning you can only send a maximum of 65k before you need an
    > acknowledgement that the data has been received. Most data transfer
    > protocols have similar limitations.


    Say what? There's no such limitation in IP. In fact, IP doesn't
    require *ANY* acknowledgments at all.

    Perhaps you're thinking of TCP -- but see RFC 1323. Modern TCP
    doesn't have that limitation.

    > There _used_ to be a HAM-HOWTO that might contain some hints if you can
    > find a copy. There is also the AX25-HOWTO that isn't to out of date.


    AX.25 might be a possibility.

    --
    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

  4. Re: Establishing a Point to Point connection over radio networks

    James Carlson wrote in message news:...
    > ibuprofin@painkiller.example.tld (Moe Trin) writes:
    >
    > > In article <15faa2ac.0408141852.4d82b501@posting.google.com>, Vanitha wrote:
    > > >I need to establish a point to point connection between two VHF
    > > >Radios.

    >
    > > >The radios have a serial interface (RS 232C) which can be connected
    > > >to a Linux PC. Can i run PPPD on this ?.Will it work on half-duplex
    > > >radios ?

    > >
    > > I suppose so, but the latency might be a problem.

    >
    > Perhaps. Technically, PPP does require a full-duplex connection.
    > What this really means is that there's nothing in PPP that will
    > support half-duplex operation; there's no "go ahead" or "poll" signals
    > that you could use. If your half-duplex system doesn't require those
    > sorts of signals -- if each side can send when it wants -- then at
    > least that's not a problem.
    >
    > > A lot might depend on
    > > the protocols you are using - for example IP has a maximum data window
    > > of 65k, meaning you can only send a maximum of 65k before you need an
    > > acknowledgement that the data has been received. Most data transfer
    > > protocols have similar limitations.

    >
    > Say what? There's no such limitation in IP. In fact, IP doesn't
    > require *ANY* acknowledgments at all.
    >
    > Perhaps you're thinking of TCP -- but see RFC 1323. Modern TCP
    > doesn't have that limitation.
    >
    > > There _used_ to be a HAM-HOWTO that might contain some hints if you can
    > > find a copy. There is also the AX25-HOWTO that isn't to out of date.

    >
    > AX.25 might be a possibility.


    Is is possible to establish PPP session from an Windows XP machine?
    Are there any drivers available for that ?

  5. Re: Establishing a Point to Point connection over radio networks

    vanitha@agilis.st.com.sg (Vanitha) writes:
    > Is is possible to establish PPP session from an Windows XP machine?
    > Are there any drivers available for that ?


    Doesn't XP come with PPP as a basic part of the operating system?

    Something called "Dial-Up Networking," perhaps?

    --
    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

  6. Re: Establishing a Point to Point connection over radio networks

    [Delayed posting - news server problems]

    In article , James Carlson wrote:
    >ibuprofin@painkiller.example.tld (Moe Trin) writes:


    >Perhaps. Technically, PPP does require a full-duplex connection.
    >What this really means is that there's nothing in PPP that will
    >support half-duplex operation; there's no "go ahead" or "poll" signals
    >that you could use.


    I was making the unsupported assumption that the OP had figured out
    some method of supporting that - possibly some external FIFOs, with
    send/receive logic somehow cobbled off that.

    >Say what? There's no such limitation in IP. In fact, IP doesn't
    >require *ANY* acknowledgments at all.


    Picky, picky ;-)

    >Perhaps you're thinking of TCP -- but see RFC 1323. Modern TCP
    >doesn't have that limitation.


    Yes, I was. Is anyone actually implementing that? The RFC is dated in
    1992, and I don't see any further documents talking about it. I also don't
    think I've seen any packets passing nearby with the required options
    fields.

    >AX.25 might be a possibility.


    I'm thinking there was an RFC about it, but can't put my finger on it now.
    The only thing I turn up is RFC1226 which is IP encapsulation of AX.25.
    Not what we're looking for.

    Old guy

  7. Re: Establishing a Point to Point connection over radio networks

    ibuprofin@painkiller.example.tld (Moe Trin) writes:
    > >Perhaps you're thinking of TCP -- but see RFC 1323. Modern TCP
    > >doesn't have that limitation.

    >
    > Yes, I was. Is anyone actually implementing that? The RFC is dated in
    > 1992, and I don't see any further documents talking about it. I also don't
    > think I've seen any packets passing nearby with the required options
    > fields.


    On what systems? I can't say I've noticed any that lack TCP timestamp
    usage for PAWS or window scaling. But, then, I really only use UNIX
    and UNIX-like systems.

    > >AX.25 might be a possibility.

    >
    > I'm thinking there was an RFC about it, but can't put my finger on it now.
    > The only thing I turn up is RFC1226 which is IP encapsulation of AX.25.
    > Not what we're looking for.


    There are many references you can dig up with Google. Here are a
    couple:

    http://hams.sourceforge.net/ax25/
    http://www.tapr.org/tapr/pdf/AX25.2.2.pdf

    --
    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

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