rfc2637.txt

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      |                         Magic Cookie                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Control Message Type      |           Reserved0           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Identifier                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Length                   Total length in octets of this PPTP message,
                            including the entire PPTP header.

   PPTP Message Type        1 for Control Message.

   Magic Cookie             0x1A2B3C4D.

   Control Message Type     5 for Echo-Request.

   Reserved0                This field MUST be 0.






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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


   Identifier               A value set by the sender of the Echo-
                            Request that is used to match the reply with
                            the corresponding request.

2.6.  Echo-Reply

   The Echo-Reply is a PPTP control message sent by either peer of a
   PAC-PNS control connection in response to the receipt of an Echo-
   Request.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Length             |      PPTP Message Type        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Magic Cookie                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Control Message Type      |           Reserved0           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Identifier                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Result Code  |   Error Code  |           Reserved1           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Length                   Total length in octets of this PPTP message,
                            including the entire PPTP header.

   PPTP Message Type        1 for Control Message.

   Magic Cookie             0x1A2B3C4D.

   Control Message Type     6 for Echo-Reply.

   Reserved0                This field MUST be 0.

   Identifier               The contents of the identify field from the
                            received Echo-Request is copied to this
                            field.

   Result Code              Indicates the result of the receipt of the
                            Echo-Request. Current valid Result Code
                            values are:

                                  1 (OK) - The Echo-Reply is valid

                                  2 (General Error) - Echo-Request not
                                    accepted for the reason indicated in
                                    Error Code



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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


   Error Code               This field is set to 0 unless a "General
                            Error" condition exists, in which case
                            Result Code is set to 2 and this field is
                            set to the value corresponding to the
                            general error condition as specified in
                            section 2.2.

   Reserved1                This field MUST be 0.

2.7.  Outgoing-Call-Request

   The Outgoing-Call-Request is a PPTP control message sent by the PNS
   to the PAC to indicate that an outbound call from the PAC is to be
   established.  This request provides the PAC with information required
   to make the call. It also provides information to the PAC that is
   used to regulate the transmission of data to the PNS for this session
   once it is established.


































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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Length             |       PPTP Message Type       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Magic Cookie                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Control Message Type      |           Reserved0           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Call ID            |      Call Serial Number       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Minimum BPS                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Maximum BPS                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Bearer Type                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Framing Type                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Packet Recv. Window Size    |    Packet Processing Delay    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Phone Number Length      |           Reserved1           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                   Phone Number (64 octets)                    +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                    Subaddress (64 octets)                     +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Length                   Total length in octets of this PPTP message,
                            including the entire PPTP header.

   PPTP Message Type        1 for Control Message.

   Magic Cookie             0x1A2B3C4D.

   Control Message Type     7 for Outgoing-Call-Request.

   Reserved0                This field MUST be 0.









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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


   Call ID                  A unique identifier, unique to a particular
                            PAC-PNS pair assigned by the PNS to this
                            session.  It is used to multiplex and
                            demultiplex data sent over the tunnel
                            between the PNS and PAC involved in this
                            session.

   Call Serial Number       An identifier assigned by the PNS to this
                            session for the purpose of identifying this
                            particular session in logged session
                            information.  Unlike the Call ID, both the
                            PNS and PAC associate the same Call Serial
                            Number with a given session. The combination
                            of IP address and call serial number SHOULD
                            be unique.

   Minimum BPS              The lowest acceptable line speed (in
                            bits/second) for this session.

   Maximum BPS              The highest acceptable line speed (in
                            bits/second) for this session.

   Bearer Type              A value indicating the bearer capability
                            required for this outgoing call.  The
                            currently defined values are:

                                  1 - Call to be placed on an analog
                                      channel

                                  2 - Call to be placed on a digital
                                      channel

                                  3 - Call can be placed on any type of
                                      channel

   Framing Type             A value indicating the type of PPP framing
                            to be used for this outgoing call.

                                  1 - Call to use Asynchronous framing

                                  2 - Call to use Synchronous framing

                                  3 - Call can use either type of
                                      framing

   Packet Recv. Window Size The number of received data packets the PNS
                            will buffer for this session.




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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


   Packet Processing Delay  A measure of the packet processing delay
                            that might be imposed on data sent to the
                            PNS from the PAC.  This value is specified
                            in units of 1/10 seconds.  For the PNS this
                            number should be very small.  See section
                            4.4 for a description of how this value is
                            determined and used.

   Phone Number Length      The actual number of valid digits in the
                            Phone Number field.

   Reserved1                This field MUST be 0.

   Phone Number             The number to be dialed to establish the
                            outgoing session.  For ISDN and analog calls
                            this field is an ASCII string.  If the Phone
                            Number is less than 64 octets in length, the
                            remainder of this field is filled with
                            octets of value 0.

   Subaddress               A 64 octet field used to specify additional
                            dialing information.  If the subaddress is
                            less than 64 octets long, the remainder of
                            this field is filled with octets of value 0.

2.8.  Outgoing-Call-Reply

   The Outgoing-Call-Reply is a PPTP control message sent by the PAC to
   the PNS in response to a received Outgoing-Call-Request message.  The
   reply indicates the result of the outgoing call attempt.  It also
   provides information to the PNS about particular parameters used for
   the call.  It provides information to allow the PNS to regulate the
   transmission of data to the PAC for this session.


















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RFC 2637        Point-to-Point Tunneling Protocol (PPTP)       July 1999


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1