pptp-draft.txt

pptp第二层隧道模块

Hamzeh, et al                                                  [Page 18]

Internet Draft                    PPTP                         July 1997


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

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



Hamzeh, et al                                                  [Page 19]

Internet Draft                    PPTP                         July 1997


                               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 2.16.

      Reserved1                This field MUST be 0.












































Hamzeh, et al                                                  [Page 20]

Internet Draft                    PPTP                         July 1997


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.

       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.




Hamzeh, et al                                                  [Page 21]

Internet Draft                    PPTP                         July 1997


      Magic Cookie             0x1A2B3C4D.

      Control Message Type     7 for Outgoing-Call-Request.

      Reserved0                This field MUST be 0.

      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



Hamzeh, et al                                                  [Page 22]

Internet Draft                    PPTP                         July 1997


                                  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.

      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 appendix A 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.




















Hamzeh, et al                                                  [Page 23]

Internet Draft                    PPTP                         July 1997


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.

       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            |       Peer's Call ID          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Result Code  |  Error Code   |          Cause Code           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Connect Speed                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Packet Recv. Window Size    |    Packet Processing Delay    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Physical Channel ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      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     8 for Outgoing-Call-Reply.

      Reserved0                This field MUST be 0.

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