pptp-draft.txt

pptp第二层隧道模块

Internet Draft                    PPTP                         July 1997


2.2 Start-Control-Connection-Reply

   The Start-Control-Connection-Reply is a PPTP control message sent in
   reply to a received Start-Control-Connection-Request message.  This
   message contains a result code indicating the result of the control
   connection establishment attempt.

       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           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Protocol Version        |  Result Code  |  Error Code   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Framing Capability                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Bearer Capability                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Maximum Channels        |       Firmware Revision       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                     Host Name (64 octets)                     +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                   Vendor String (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     2 for Start-Control-Connection-Reply.

      Reserved0                This field MUST be 0.

      Protocol Version         The version of the PPTP protocol that the



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Internet Draft                    PPTP                         July 1997


                               sender wishes to use.

      Result Code              Indicates the result of the command
                               channel establishment attempt.  Current
                               valid Result Code values are:

                                  1 - Successful channel establishment

                                  2 - General error -- Error Code
                                      indicates the problem

                                  3 - Command channel already exists;

                                  4 - Requester is not authorized to
                                      establish a command channel

                                  5 - The protocol version of the
                                      requester is not supported

      Error Code               This field is set to 0 unless a "General
                               Error" 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 2.16.

      Framing Capabilities     A set of bits indicating the type of
                               framing that the sender of this message
                               can provide.  The currently defined bit
                               settings are:

                                  1 - Asynchronous Framing supported

                                  2 - Synchronous Framing supported.

      Bearer Capabilities      A set of bits indicating the bearer
                               capabilities that the sender of this
                               message can provide.  The currently
                               defined bit settings are:

                                  1 - Analog access supported

                                  2 - Digital access supported

      Maximum Channels         The total number of individual PPP
                               sessions this PAC can support.  In a
                               Start-Control-Connection-Reply issued by
                               the PNS, this value SHOULD be set to 0
                               and it must be ignored by the PAC. The



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Internet Draft                    PPTP                         July 1997


                               PNS MUST NOT use this value to try to
                               track the remaining number of PPP
                               sessions that the PAC will allow.

      Firmware Revision        This field contains the firmware revision
                               number of the issuing PAC, or the version
                               of the PNS PPTP driver if issued by the
                               PNS.

      Host Name                A 64 octet field containing the DNS name
                               of the issuing PAC or PNS.  If less than
                               64 octets in length, the remainder of
                               this field SHOULD be filled with octets
                               of value 0.

      Vendor Name              A 64 octet field containing a vendor
                               specific string describing the type of
                               PAC being used, or the type of PNS
                               software being used if this request is
                               issued by the PNS.  If less than 64
                               octets in length, the remainder of this
                               field SHOULD be filled with octets of
                               value 0.




























Hamzeh, et al                                                  [Page 15]

Internet Draft                    PPTP                         July 1997


2.3 Stop-Control-Connection-Request

   The Stop-Control-Connection-Request is a PPTP control message sent by
   one peer of a PAC-PNS control connection to inform the other peer
   that the control connection should be closed.  In addition to closing
   the control connection, all active user calls are implicitly cleared.
   The reason for issuing this request is indicated in the Reason field.

       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           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Reason     |   Reserved1   |           Reserved2           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      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     3 for Stop-Control-Connection-Request.

      Reserved0                This field MUST be 0.

      Reason                   Indicates the reason for the control
                               connection being closed. Current valid
                               Reason values are:

                                  1 (None) - General request to clear
                                    control connection

                                  2 (Stop-Protocol) - Can't support
                                    peer's version of the protocol

                                  3 (Stop-Local-Shutdown) - Requester is
                                    being shut down

      Reserved1, Reserved2     These fields MUST be 0.



Hamzeh, et al                                                  [Page 16]

Internet Draft                    PPTP                         July 1997


2.4 Stop-Control-Connection-Reply

   The Stop-Control-Connection-Reply is a PPTP control message sent by
   one peer of a PAC-PNS control connection upon receipt of a Stop-
   Control-Connection-Request from the other peer.

       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           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  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     4 for Stop-Control-Connection-Reply.

      Reserved0                This field MUST be 0.

      Result Code              Indicates the result of the attempt to
                               close the control connection. Current
                               valid Result Code values are:

                                  1 (OK) - Control connection closed

                                  2 (General Error) - Control connection
                                    not closed for reason indicated in
                                    Error Code

      Error Code               This field is set to 0 unless a "General
                               Error" 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 2.16.

      Reserved1                This field MUST be 0.



Hamzeh, et al                                                  [Page 17]

Internet Draft                    PPTP                         July 1997


2.5 Echo-Request

   The Echo-Request is a PPTP control message sent by either peer of a
   PAC-PNS control connection. This control message is used as a "keep-
   Alive" for the control connection.  The receiving peer issues an
   Echo-Reply to each Echo-Request received. As specified in Section 3,
   if the sender does not receive an Echo Reply in response to an Echo-
   Request, it will eventually clear the control connection.

       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                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      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.

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