rfc2661.txt

第二层隧道模块l2tp源码,开发环境为linux

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Vendor Name ...(arbitrary number of octets)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Vendor Name is the indicated number of octets representing the
      vendor string. Human readable text for this AVP MUST be provided
      in the UTF-8 charset using the Default Language [RFC2277].

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 0.  The Length (before hiding) of this AVP
      is 6 plus the length of the Vendor Name.

   Assigned Tunnel ID (SCCRP, SCCRQ, StopCCN)

      The Assigned Tunnel ID AVP, Attribute Type 9, encodes the ID being
      assigned to this tunnel by the sender.

      The Attribute Value field for this AVP has the following format:

       0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Assigned Tunnel ID       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Assigned Tunnel ID is a 2 octet non-zero unsigned integer.

      The Assigned Tunnel ID AVP establishes a value used to multiplex
      and demultiplex multiple tunnels between the LNS and LAC. The L2TP
      peer MUST place this value in the Tunnel ID header field of all



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RFC 2661                          L2TP                       August 1999


      control and data messages that it subsequently transmits over the
      associated tunnel.  Before the Assigned Tunnel ID AVP is received
      from a peer, messages MUST be sent to that peer with a Tunnel ID
      value of 0 in the header of all control messages.

      In the StopCCN control message, the Assigned Tunnel ID AVP MUST be
      the same as the Assigned Tunnel ID AVP first sent to the receiving
      peer, permitting the peer to identify the appropriate tunnel even
      if a StopCCN is sent before an Assigned Tunnel ID AVP is received.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 8.

   Receive Window Size (SCCRQ, SCCRP)

      The Receive Window Size AVP, Attribute Type 10, specifies the
      receive window size being offered to the remote peer.

      The Attribute Value field for this AVP has the following format:

       0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Window Size           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Window Size is a 2 octet unsigned integer.

      If absent, the peer must assume a Window Size of 4 for its
      transmit window. The remote peer may send the specified number of
      control messages before it must wait for an acknowledgment.

      This AVP MUST NOT be hidden (the H-bit MUST be 0). The M-bit for
      this AVP MUST be set to 1.  The Length of this AVP is 8.

   Challenge (SCCRP, SCCRQ)

      The Challenge AVP, Attribute Type 11, indicates that the issuing
      peer wishes to authenticate the tunnel endpoints using a CHAP-
      style authentication mechanism.










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      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Challenge ... (arbitrary number of octets)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Challenge is one or more octets of random data.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 6 plus the length of the Challenge.

   Challenge Response (SCCCN, SCCRP)

      The Response AVP, Attribute Type 13, provides a response to a
      challenge received.

      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Response ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                              ... (16 octets)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Response is a 16 octet value reflecting the CHAP-style
      [RFC1994] response to the challenge.

      This AVP MUST be present in an SCCRP or SCCCN if a challenge was
      received in the preceding SCCRQ or SCCRP. For purposes of the ID
      value in the CHAP response calculation, the value of the Message
      Type AVP for this message is used (e.g. 2 for an SCCRP, and 3 for
      an SCCCN).

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 22.






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RFC 2661                          L2TP                       August 1999


4.4.4 Call Management AVPs

   Q.931 Cause Code (CDN)

      The Q.931 Cause Code AVP, Attribute Type 12, is used to give
      additional information in case of unsolicited call disconnection.

      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Cause Code           |   Cause Msg   | Advisory Msg...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Cause Code is the returned Q.931 Cause code, and Cause Msg is the
      returned Q.931 message code (e.g., DISCONNECT) associated with the
      Cause Code.  Both values are returned in their native ITU
      encodings [DSS1]. An additional ASCII text Advisory Message may
      also be included (presence indicated by the AVP Length) to further
      explain the reason for disconnecting.

      This AVP MUST NOT be hidden (the H-bit MUST be 0). The M-bit for
      this AVP MUST be set to 1.  The Length of this AVP is 9, plus the
      size of the Advisory Message.

   Assigned Session ID (CDN, ICRP, ICRQ, OCRP, OCRQ)

      The Assigned Session ID AVP, Attribute Type 14, encodes the ID
      being assigned to this session by the sender.

      The Attribute Value field for this AVP has the following format:

       0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Assigned Session ID       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Assigned Session ID is a 2 octet non-zero unsigned integer.

      The Assigned Session ID AVP is establishes a value used to
      multiplex and demultiplex data sent over a tunnel between the LNS
      and LAC. The L2TP peer MUST place this value in the Session ID
      header field of all control and data messages that it subsequently
      transmits over the tunnel that belong to this session.  Before the





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      Assigned Session ID AVP is received from a peer, messages MUST be
      sent to that peer with a Session ID of 0 in the header of all
      control messages.

      In the CDN control message, the same Assigned Session ID AVP first
      sent to the receiving peer is used, permitting the peer to
      identify the appropriate tunnel even if CDN is sent before an
      Assigned Session ID is received.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 8.

   Call Serial Number (ICRQ, OCRQ)

      The Call Serial Number AVP, Attribute Type 15, encodes an
      identifier assigned by the LAC or LNS to this call.

      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Call Serial Number                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Call Serial Number is a 32 bit value.

      The Call Serial Number is intended to be an easy reference for
      administrators on both ends of a tunnel to use when investigating
      call failure problems. Call Serial Numbers should be set to
      progressively increasing values, which are likely to be unique for
      a significant period of time across all interconnected LNSs and
      LACs.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 10.

   Minimum BPS (OCRQ)

      The Minimum BPS AVP, Attribute Type 16, encodes the lowest
      acceptable line speed for this call.








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      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Minimum BPS                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The  Minimum BPS is a 32 bit value indicates the speed in bits per
      second.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 10.

   Maximum BPS (OCRQ)

      The Maximum BPS AVP, Attribute Type 17, encodes the highest
      acceptable line speed for this call.

      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Maximum BPS                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Maximum BPS is a 32 bit value indicates the speed in bits per
      second.

      This AVP may be hidden (the H-bit may be 0 or 1). The M-bit for
      this AVP MUST be set to 1.  The Length (before hiding) of this AVP
      is 10.

   Bearer Type (ICRQ, OCRQ)

      The Bearer Type AVP, Attribute Type 18,  encodes the bearer type
      for the incoming or outgoing call.

      The Attribute Value field for this AVP has the following format:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Reserved for future Bearer Types                |A|D|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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      The Bearer Type is a 32-bit bit mask, which indicates the bearer
      capability of the call (ICRQ) or required for the call (OCRQ). If
      set, bit A indicates that the call refers to an analog channel. If
      set, bit D indicates that the call refers to a digital channel.
      Both may be set, indicating that the call was either
      indistinguishable, or can be placed on either type of channel.