Network Working Group Rohit Verma Internet Draft Deloitte Consulting Expires November 2000 Madhvi Verma 3Com Corporation James Carlson Sun Microsystems May 2000 L2TP Disconnect Cause Information Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract The Layer 2 Tunneling Protocol (``L2TP'') defines a mechanism for tunneling PPP sessions. The current RFC lacks a mechanism for the LNS to provide PPP related disconnect cause information to the LAC. 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 expires November 2000 Verma, Verma, Carlson [Page 1] INTERNET DRAFT L2TP Disconnect Cause May 2000 disconnect information to be provided to an L2TP host (LAC/LNS) in a descriptive format. The lack of this information is especially a problem when the LAC and LNS are not managed by the same entities. The Result and Error Codes defined for L2TP specify only L2TP- specific disconnect information. This document provides an additional AVP that MAY be used by an L2TP host to provide PPP specific discon- nect information to its peer for accounting and debugging purposes. This AVP should be used in conjunction with, and not as a replacement for, the 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. The following AVP should not have any effect on either the functioning of the tunnel or the functioning of the PPP session. 2. AVP 2.1. PPP Disconnect Cause Code The AVP is valid in the CDN message only, and it MUST NOT be marked Mandatory. The PPP Disconnect Cause Code AVP is encoded as Vendor ID 43 (3Com Corporation), with an Attribute Type of PPP Disconnect Cause Code (46). The attribute value is one of the values discussed in section 2.1.1. The length of the value field MUST be at least 11 octets. If the length is more than 11 octets, the additional octets SHOULD con- tain a descriptive text in ASCII format that can be displayed to the user or in a log file. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CP Number | Direction | Message... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1.1 PPP Disconnect Cause code AVP Mandatory (M) bit: MUST be 0. Hidden (H) bit: MAY be 1 if the attribute is hidden. expires November 2000 Verma, Verma, Carlson [Page 2] INTERNET DRAFT L2TP Disconnect Cause May 2000 Length: The length of the entire attribute in octets, expressed as a single octet. MUST be at least 11. Vendor ID: A two octet value in network byte order; set to 43 (3Com Corporation). 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. CP Number: Primary failing Control Protocol, if any. This field may be 0 unless mentioned otherwise in the description of the Disconnect Cause Codes in section 2.1.1. Direction(D) Flag: 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 may be 0 unless mentioned otherwise in the description of the Disconnect Cause Codes in section 2.1.1. 2.1.1. Disconnect Cause 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 main- tain a registry of the up-to-date values. These values should be used in conjunction with the Direction flag and the Control Protocol Number to get the specific error code. 2.1.1.1. Global Errors The global error codes, given in the list below, are Disconnect Codes that do not relate to one particular control protocol. The CP Number for these errors MUST be set to 0 and the Direction (D) flag MUST also be set to 0 unless specified otherwise for a given code. 0 No information available. 1 Administrative disconnect. expires November 2000 Verma, Verma, Carlson [Page 3] INTERNET DRAFT L2TP Disconnect Cause May 2000 2 LCP renegotiation at LNS disabled; LNS expects proxy LCP information, LAC did not send it. 3 Normal Disconnection, LCP Terminate-Request sent. Valid Direction flags: 1: By peer 2: By local 4 Compulsory encryption required by a PPP peer was refused by the other. Valid Direction flags are: 1: Required by local; refused by peer 2: Required by peer; refused by local 2.1.1.2. LCP Errors The LCP error codes, listed below, are disconnect reasons that are directly related to failure of PPP peers to negotiate mutually agree- able link parameters. The CP Number for such errors MUST be set to 0xCO21 and the direction flag to the direction of the failure. 5 FSM Timeout error. 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 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 callback required by a PPP peer was refused by the other. Valid Direction flags are: 1: Required by local; refused by peer expires November 2000 Verma, Verma, Carlson [Page 4] INTERNET DRAFT L2TP Disconnect Cause May 2000 2: Required by peer; refused by local 2.1.1.3. Authentication Errors The authentication errors codes, listed below, are disconnect reasons that are directly related to authentication failures between the PPP peers. The CP Number for such errors MUST correspond to the control protocol number for the authentication protocol in use and the direc- tion flag to the direction of the failure. 13 FSM Timeout error. 14 Peer has unexpected authenticated name for existing MP bundle. 15 PPP authentication failure-Authentication protocol unacceptable. Valid Direction flags 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 flags are: 1: Authentication of peer identity by local system. 2: Authentication of local identity by peer system. 2.1.1.4. Network Control Protocol Errors NCP Errors are disconnect reasons that are directly related to the failure of PPP peers to negotiate a mutually agreeable set of parame- ters for the network protocols. The CP Number for such errors MUST correspond to the network control protocol number in use and the direction flag to the direction of the failure. Where multiple net- work protocols are in use, multiple copies of this AVP may be given to indicate failure reasons for each NCP. The Control Protocol field in the following cases will be the last or primary failing NCP. 17 FSM Timeout error. expires November 2000 Verma, Verma, Carlson [Page 5] INTERNET DRAFT L2TP Disconnect Cause May 2000 18 No NCPs available (all disabled or rejected); no NCPs went to Opened state. 19 NCP failure: failed to converge on acceptable addresses. 20 NCP failure: user not permitted to use any addresses. 3. Notes This AVP MAY always be sent by the LNS to the LAC. However, at the LAC, this AVP would be more useful diagnostically in the compulsory case than in the voluntary case. In a voluntary model, it can be presumed that local PPP traces are always present. 4. IANA Considerations This AVP includes an enumerated cause code value. Values 0 through 20 are described in this document. New values may be assigned by the IANA. 5. References [1] W. Townsley, A. Valencia, A. Rubens, G. Pall, G. Zorn, B. Palter, ``Layer 2 Tunnel Protocol (L2TP)'', RFC2661, August 1999. 6. Acknowledgements The Authors would like to thank W. Mark Townsley for his useful com- ments to an earlier version of this document. 7. Contacts 7.1. L2TP Working Group Chair W. Mark Townsley Cisco Systems 7025 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 Email: expires November 2000 Verma, Verma, Carlson [Page 6] INTERNET DRAFT L2TP Disconnect Cause May 2000 7.2. Authors Rohit Verma 180 N. Stetson Avenue Chicago IL 60601 Phone: +1 312 374 2475 Fax: +1 312 870 2475 Email: Madhvi Verma 1800 W. Central Road Mount Prospect IL 60056 Phone: +1 847 797 6528 Fax: +1 847 222 2424 Email: James Carlson Sun Microsystems 1 Network Drive MS UBUR02-212 Burlington MA 01803-2757 Email: Voice: +1 781 442 2084 Fax: +1 781 442 1677 8. Notices The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to per- tain 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. expires November 2000 Verma, Verma, Carlson [Page 7] INTERNET DRAFT L2TP Disconnect Cause May 2000 expires November 2000 Verma, Verma, Carlson [Page 8]