HDLC PPP - PPP

This is a discussion on HDLC PPP - PPP ; Hello all, I am writing to ask all the PPP gurus to help assist me in understanding the PPP protocol and Simple HDLC PPP protocol. My situation is I have a IM driver right between the PPP protocol driver and ...

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Thread: HDLC PPP

  1. HDLC PPP

    Hello all,

    I am writing to ask all the PPP gurus to help assist me in
    understanding the PPP protocol and Simple HDLC PPP protocol.

    My situation is I have a IM driver right between the PPP protocol
    driver and the WAN miniport driver. In this case it happens to be on
    WinCE.

    I can see the traffic come in and out but I am new to PPP. And from
    my research it looks like the PPP packets are HDLC. I'm not sure yet
    what this really means.

    What I do know is that I can see the start sequence, 0x7E. And I try
    to capture the known fields afterwards (control, protocl, etc) - but
    they seem invalid.

    Is there something I'm missing?

  2. Re: HDLC PPP

    john_walker2020@yahoo.com (John Walker) writes:
    > My situation is I have a IM driver right between the PPP protocol
    > driver and the WAN miniport driver. In this case it happens to be on
    > WinCE.


    The above is just plain greek to me. No clue what you're saying.

    > I can see the traffic come in and out but I am new to PPP. And from
    > my research it looks like the PPP packets are HDLC. I'm not sure yet
    > what this really means.


    PPP uses HDLC-like framing. This means that PPP reuses the same basic
    framing formats, error detection, and header fields, but doesn't use
    the rest of HDLC -- it doesn't use the 7 bit encoding mechanism, nor
    (at least by default) any of the various reliability schemes (such as
    LAP-B).

    > What I do know is that I can see the start sequence, 0x7E. And I try
    > to capture the known fields afterwards (control, protocl, etc) - but
    > they seem invalid.


    If you're seeing 7E, then this is either octet synchronous PPP (used
    only on SONET/SDH) or (very much more likely) AHDLC. See RFC 1662:

    ftp://ftp.isi.edu/in-notes/rfc1662.txt

    And, of course, the actual exchanges are described in RFC 1661, as
    well as a number of other RFCs that are specific to what you're trying
    to do with the link (likely, you need RFCs 1332 and 1334, but that's
    just a guess).

    I can recommand a book on this if you're interested.

    > Is there something I'm missing?


    Well, for one thing, you haven't actually given any debug output or
    other details, so it's hard to say what the problem might be.

    --
    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: HDLC PPP

    In article ,
    John Walker wrote:
    >Hello all,
    >
    > I am writing to ask all the PPP gurus to help assist me in
    >understanding the PPP protocol and Simple HDLC PPP protocol.
    >
    >My situation is I have a IM driver right between the PPP protocol
    >driver and the WAN miniport driver. In this case it happens to be on
    >WinCE.


    Interesting... I've never had any luck getting an intermediate driver
    at that level. Any hints on how you did that?

    >I can see the traffic come in and out but I am new to PPP. And from
    >my research it looks like the PPP packets are HDLC. I'm not sure yet
    >what this really means.
    >
    >What I do know is that I can see the start sequence, 0x7E. And I try
    >to capture the known fields afterwards (control, protocl, etc) - but
    >they seem invalid.
    >
    >Is there something I'm missing?


    Why don't you dump a bunch of the bytes your seeing (it would be best
    to show all the bytes in sequence seperated by channel only)? I bet
    it'll start to make sense once you see how simple it really is.

    Patrick
    ========= For LAN/WAN Protocol Analysis, check out PacketView Pro! =========
    Patrick Klos Email: patrick@klos.com
    Klos Technologies, Inc. Web: http://www.klos.com/
    ==================== What goes around, comes around... =====================

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