GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3145

Network Working Group R. Verma Request for Comments: 3145 Deloitte Consulting Category: Standards Track M. Verma

                                                      3Com Corporation
                                                            J. Carlson
                                                      Sun Microsystems
                                                             July 2001
                 L2TP Disconnect Cause Information

Status 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-specific

Verma, 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 in BCP 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
 in section 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 in section 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 (see section 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 local

3.2. 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 local

Verma, et al. Standards Track [Page 4] RFC 3145 L2TP Disconnect Cause Information July 2001

3.3. 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 in section 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 2001

6. IANA Considerations

 IANA has assigned an L2TP Attribute Type value of 46 for the PPP
 Disconnect Cause Code defined in Section 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", RFC
     2279, 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 2001

9. Contacts

9.1. L2TP Working Group Chair

 W. Mark Townsley
 Cisco Systems
 7025 Kit Creek Road
 PO Box 14987
 Research Triangle Park, NC 27709
 EMail:  townsley@cisco.com

9.2. 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.com

Verma, et al. Standards Track [Page 8] RFC 3145 L2TP Disconnect Cause Information July 2001

10. Standard Notices

10.1. 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 in BCP 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 2001

Full 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]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3145.txt · Last modified: 2001/07/14 00:17 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki