Movatterモバイル変換

Network Working Group                                           R. VermaRequest for Comments: 3145                           Deloitte ConsultingCategory: Standards Track                                       M. Verma                                                        3Com Corporation                                                              J. Carlson                                                        Sun Microsystems                                                               July 2001L2TP Disconnect Cause InformationStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2001).  All Rights Reserved.Abstract   This document provides an extension to the Layer 2 Tunneling Protocol   ("L2TP"), a mechanism for tunneling Point-to-Point Protocol (PPP)   sessions.  L2TP lacks a mechanism for a host to provide PPP-related   disconnect cause information to another host.  This information,   provided by the extension described in this document, can be useful   for accounting and debugging purposes.1.  Introduction   L2TP [1] defines a general-purpose mechanism for tunneling PPP over   various media.  By design, it insulates L2TP operation from the   details of the PPP session that is being encapsulated by L2TP.  There   are, however, cases where it may be desirable for PPP-specific   disconnect information to be provided to an L2TP host (L2TP Access   Concentrator [LAC] or L2TP Network Server [LNS]) in a descriptive   format.  The lack of this information is especially a problem when   the LAC and LNS are not owned or managed by the same entities.   The Result and Error Codes defined for L2TP specify only L2TP-   specific disconnect information.  This document provides an   additional Attribute Value Pair (AVP), called PPP Disconnect Cause   Code, that MAY be used by an L2TP host to provide PPP-specificVerma, et al.               Standards Track                     [Page 1]

RFC 3145           L2TP Disconnect Cause Information           July 2001   disconnect information to its peer.  This AVP should be used in   conjunction with, and not as a replacement for, the L2TP Result and   Error Code AVPs.   The PPP Disconnect Cause Code AVP can also be used to provide a   human-readable disconnect reason to the user.  This AVP should not   have any effect on either the functioning of the tunnel or the   functioning of the PPP session; it is for informational and logging   purposes only.   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inBCP 14 [2].2.  PPP Disconnect Cause Code AVP   The AVP is valid in the L2TP Call-Disconnect-Notify (CDN) message   only, and it MUST NOT be marked Mandatory.   The PPP Disconnect Cause Code AVP is encoded with Vendor ID 0 and an   Attribute Type of PPP Disconnect Cause Code (46).  The length of the   Value field MUST be at least 11 octets.  If the length is more than   11 octets, the additional octets MUST contain a descriptive text in   UTF-8 [3] format that can be displayed to the user or in a log file.   The format of the AVP is shown below.      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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |M|H| rsvd  |      Length       |          Vendor ID          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |         Attribute Type        |       Disconnect Code       |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Control Protocol Number    |   Direction   | Message...      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-                  Figure 1: PPP Disconnect Cause Code AVP   Mandatory (M) bit: MUST be 0.   Hidden (H) bit: MAY be 1 if the attribute is hidden.   Length: The length of the entire attribute in octets, expressed as a   single octet.  The length MUST be at least 11.   Vendor ID: A two octet value in network byte order; set to 0 to   indicate that this is an IETF-assigned attribute.Verma, et al.               Standards Track                     [Page 2]

RFC 3145           L2TP Disconnect Cause Information           July 2001   Attribute Type: A two octet value in network byte order; set to 46   (PPP Disconnect Cause Code).   Disconnect Code: A two octet value in network byte order.  (Described   insection 3 of this document.)   Control Protocol Number: The PPP Control Protocol number of the   primary protocol known to have caused the error, if any.  This field   may be 0 unless mentioned otherwise in the description of the   Disconnect Codes insection 3.   Direction: A single octet value; specifies the direction in which the   Disconnect Code applies.            The valid values of this field are:                    0: global error                    1: at peer                    2: at local                    3-255: Reserved   This field SHOULD be 0 unless documented otherwise in the description   of the specific Disconnect Code.3.  Disconnect Codes   This section contains the list of well-known values of the Disconnect   Code field in the PPP Disconnect Cause Code AVP.  The IANA will   maintain a registry of the up-to-date values (seesection 5 of this   document).  These values should be used in conjunction with the   Direction value and the Control Protocol Number field to interpret   the specific error condition.   Unless documented otherwise for a specific Disconnect Code, the   Direction value SHOULD be 0.3.1.  Global Errors   The global error codes, given in the list below, are Disconnect Codes   that do not relate to one particular PPP Control Protocol.  The   Control Protocol Number for these errors thus MUST be set to 0.   0    No information available.   1    Administrative disconnect.   2    Link Control Protocol (LCP) renegotiation at LNS disabled; LNS        expects proxy LCP information, LAC did not send it.Verma, et al.               Standards Track                     [Page 3]

RFC 3145           L2TP Disconnect Cause Information           July 2001   3    Normal Disconnection, LCP Terminate-Request sent.        Valid Direction values are:           1: LCP Terminate-Request sent by peer           2: LCP Terminate-Request sent by local   4    Compulsory encryption required by a PPP peer was refused by the        other.        Valid Direction values are:           1: Required by local; refused by peer           2: Required by peer; refused by local3.2.  LCP Errors   The LCP error codes, listed below, are disconnect reasons that are   directly related to the failure of PPP peers to negotiate mutually   agreeable link parameters.  The Control Protocol Number for these   errors MUST be set to C021 hexadecimal (LCP).   5    FSM (Finite State Machine) Timeout error.  (PPP event "TO-".)   6    No recognizable LCP packets were received.   7    LCP failure: Magic Number error; link possibly looped back.   8    LCP link failure: Echo Request timeout.   9    Peer has unexpected Endpoint-Discriminator for existing        Multilink PPP (MP) bundle.   10   Peer has unexpected MRRU for existing MP bundle.   11   Peer has unexpected Short-Sequence-Number option for existing        MP bundle.   12   Compulsory call-back required by a PPP peer was refused by the        other.        Valid Direction values are:           1: Required by local; refused by peer           2: Required by peer; refused by localVerma, et al.               Standards Track                     [Page 4]

RFC 3145           L2TP Disconnect Cause Information           July 20013.3.  Authentication Errors   The authentication error codes, listed below, are disconnect reasons   that are directly related to authentication failures between the PPP   peers.  The Control Protocol Number for such errors MUST correspond   to the PPP Control Protocol number for the authentication protocol in   use.   13   FSM Timeout error.   14   Peer has unexpected authenticated name for existing MP bundle.   15   PPP authentication failure: Authentication protocol        unacceptable.        Valid Direction values are:           1: All local authentication protocols were rejected by the              peer.           2: All authentication protocols requested by peer were              unacceptable or unimplemented locally.   16   PPP authentication failure: Authentication failed (bad name,        password, or secret).        Valid Direction values are:           1: Authentication of peer identity by local system.           2: Authentication of local identity by peer system.3.4.  Network Control Protocol (NCP) Errors   NCP Errors are disconnect reasons that are directly related to the   failure of PPP peers to negotiate a mutually agreeable set of   parameters for the network protocols.  The Control Protocol Number   for such errors SHOULD correspond to the PPP Network Control Protocol   number in use.  Where multiple network protocols are in use, multiple   copies of this AVP MAY be given to indicate failure reasons for each   NCP.  Otherwise, if only one copy of the AVP is given, the Control   Protocol Number SHOULD correspond to the last (most recent) failing   NCP.   17   FSM Timeout error.   18   No NCPs available (all disabled or rejected); no NCPs went to        Opened state.  (Control Protocol Number may be zero only if        neither peer has enabled NCPs.)Verma, et al.               Standards Track                     [Page 5]

RFC 3145           L2TP Disconnect Cause Information           July 2001   19   NCP failure: failed to converge on acceptable addresses.        Valid Direction values are:           1: Too many Configure-Naks received from peer.           2: Too many Configure-Naks sent to peer.   20   NCP failure: user not permitted to use any addresses.        Valid Direction values are:           1: Local link address not acceptable to peer.           2: Remote link address not acceptable to local system.4.  Notes   This AVP MAY may be sent by either the LNS or LAC.  It is generally   expected that this AVP will be most useful in sending notification   from the LNS to LAC in the compulsory tunneling case, although it is   not precluded from use in any other case.   A draft form of this AVP used Vendor ID 43 (3Com Corporation) and   vendor-specific Attribute Type 46.  Implementations MAY accept AVPs   with these values as equivalent to the message described in this   document, but SHOULD NOT transmit an AVP using these values.5.  Security Considerations   The integrity and confidentiality of this AVP relies on the   underlying L2TP security mechanisms.  It is intended for logging and   diagnostic purposes in the event of PPP link failure and should not   pose a threat to system security, but the AVP MAY be hidden as   described insection 4.3 of RFC 2661.   The defined extension does not provide information that would be   useful to an attacker.  Future extensions should not be defined to   lessen security.  For instance, it is inappropriate to provide   distinguishing information that would inform the peer that a given   authentication name is correct, but the password/secret is incorrect.Verma, et al.               Standards Track                     [Page 6]

RFC 3145           L2TP Disconnect Cause Information           July 20016.  IANA Considerations   IANA has assigned an L2TP Attribute Type value of 46 for the PPP   Disconnect Cause Code defined inSection 2.   This AVP includes an enumerated cause code value, called the   "Disconnect Code."  Values 0 through 20 are described in this   document.  Values 21 through 32767 (inclusive) are assigned by the   IANA subject to IESG Approval.  Values 32768 through 65279   (inclusive) are assigned by the IANA on a First Come First Served   basis, and are intended for vendor-specific features.  Values 65280   through 65535 (inclusive) are allocated for Private or Experimental   Use, and no assignment through the IANA is expected.7.  References   [1] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G. and B.       Palter, "Layer 2 Tunnel Protocol (L2TP)",RFC 2661, August 1999.   [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement       Levels",BCP 14,RFC 2119, March 1997.   [3] Yergeau, F., "UTF-8, a transformation format of ISO 10646",RFC2279, January 1998.8.  Acknowledgments   The authors thank W. Mark Townsley and Thomas Narten for their   comments and help.Verma, et al.               Standards Track                     [Page 7]

RFC 3145           L2TP Disconnect Cause Information           July 20019.  Contacts9.1.  L2TP Working Group Chair   W. Mark Townsley   Cisco Systems   7025 Kit Creek Road   PO Box 14987   Research Triangle Park, NC 27709   EMail:  townsley@cisco.com9.2.  Authors' Addresses   Rohit Verma   180 N. Stetson Avenue   Chicago IL 60601   Phone:  +1 312 374 2475   Fax:    +1 312 870 2475   EMail:  rverma@dc.com   Madhvi Verma   3800 Golf Road   Rolling Meadows IL 60008   Phone:  +1 847 262 2987   Fax:    +1 847 262 2255   EMail:  Madhvi_Verma@3com.com   James Carlson   Sun Microsystems   1 Network Drive MS UBUR02-212   Burlington MA  01803-2757   Phone:  +1 781 442 2084   Fax:    +1 781 442 1677   EMail:  james.d.carlson@sun.comVerma, et al.               Standards Track                     [Page 8]

RFC 3145           L2TP Disconnect Cause Information           July 200110.  Standard Notices10.1.  IETF Intellectual Property Statement   The IETF takes no position regarding the validity or scope of any   intellectual property or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; neither does it represent that it   has made any effort to identify any such rights.  Information on the   IETF's procedures with respect to rights in standards-track and   standards-related documentation can be found inBCP 11.  Copies of   claims of rights made available for publication and any assurances of   licenses to be made available, or the result of an attempt made to   obtain a general license or permission for the use of such   proprietary rights by implementers or users of this specification can   be obtained from the IETF Secretariat.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights, which may cover technology that, may be required to practice   this standard.  Please address the information to the IETF Executive   Director.Verma, et al.               Standards Track                     [Page 9]

RFC 3145           L2TP Disconnect Cause Information           July 2001Full Copyright Statement   Copyright (C) The Internet Society (2001).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Verma, et al.               Standards Track                    [Page 10]