Internet Draft INTERNET DRAFT Pat R. Calhoun Category: Informational Sun Microsystems, Inc. Title: draft-ietf-pppext-l2tp-mpls-02.txt Ken Peirce Date: February 1999 3Com Corporation Layer Two Tunneling Protocol "L2TP" Multi-Protocol Label Switching Extension Status of this Memo This document is a submission by the PPP Extensions Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the l2tp@ipsec.org mailing list. Distribution of this memo is unlimited. 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 L2TP document [1] defines the base protocol which describes the method of tunneling PPP [2] data. The L2TP base protocol does not address any MPLS extensions. The goal of MPLS is to speed forwarding of packets by reducing the lookup required in routing. This draft proposes a method to allow Calhoun, Peirce expires August 1999 [Page 1] INTERNET DRAFT February 1999 L2TP Data Sessions to be assigned a Multi-Protocol Label. Table of Contents 1.0 Introduction 1.1 Conventions 2.0 Multi-Protocol Label Switching 2.1 Multi-Protocol Label AVP 2.2 Error Reporting 3.0 References 4.0 Acknowledgements 5.0 Authors' Addresses 1.0 Introduction The L2TP protocol specification does not discuss Multi-Protocol Label Switching(MPLS) [4] in any way. This document will describe how two L2TP peers can negotiate an Multi-Protocol Label (Mlabel) for an L2TP session. This will provide either the LNS or LAC with an Mlabel with which to initiate the creation of an MPLS Label Switched Path to the peer. The application of an MPLS should speed the forwarding of the L2TP packets by reducing the header analysis/lookup. This L2TP extension allows individual sessions within a tunnel to have their own Mlabel. Note that this document does not cover the negotiation of the LSP. This is a function of either the Label Distribution Protocol [5] or a routing protocol(like BGP)[6] with extensions. However, having the L3 address and it's contextually meaningful Mlabel should provide the components needed to use an LSP regardless of the label distribution mechanism used. The mechanism defined in this document assumes that the Tunnel Initiator determines what the user's appropriate label is and sends the value in either the ICRQ or OCRQ messages. The Tunnel Terminator can respond to the message by stating what it believes is the user's appropriate label. In the case where the Tunnel Terminator does not propose ANY indicator (which is infered by the absence of the MPLS AVPs in either the ICRP or OCRP) the Tunnel Initiator will assume its Mlabel is acceptable or, if it did not send one in the ICRQ or OCRQ, that no Mlabel is assigned to the session. Calhoun, Peirce expires August 1999 [Page 2] INTERNET DRAFT February 1999 A tunnel peer which violates the negotiated label value is unlikely to successfully create an LSP. 1.1 Conventions The following language conventions are used in the items of specification in this document: o MUST, SHALL, or MANDATORY -- This item is an absolute requirement of the specification. o SHOULD or RECOMMEND -- This item should generally be followed for all but exceptional circumstances. o MAY or OPTIONAL -- This item is truly optional and may be followed or ignored according to the needs of the implementor. 2.0 Multi-Protocol Label Switching This section will define the new AVP which is required for the MPLS label distribution extension of the L2TP protocol. The AVP allows the designation of an Mlabel for a specific data channel or group of data channels. 2.1 Multi-Protocol Label AVP The Mlabel is an opaque object for an L2TP session used in a method similar to [5]. The following AVP holds the Mlabel without any knowledge of its composition. The Multi-Protocol Label AVP MAY be present in ICRQ, ICRP, OCRQ and OCRP. This message is used to inform the tunnel peer that a specific Mlabel SHOULD be used for all packets related to the data channel associated with the Tunnel and Call Identifiers in the L2TP header [1]. A tunnel peer which violates the negotiated label value is unlikely to successfully create an LSP. Calhoun, Peirce expires August 1999 [Page 3] INTERNET DRAFT February 1999 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|1|0|0| Length | 43 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1 | Multi-Protocol Label Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Protocol Label Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This AVP MAY be present in the messages shown above. It is encoded with a Vendor ID of 43 (3Com Corporation) with the attribute set to 2, marked as optional, with the indicator value as data. This AVP SHOULD NOT be hidden and is optional. When present, the L2TP peer is indicating that Multi-Protocol Labels are to be used at the link layer. 2.2 Error Reporting In the event that the peer did not accept the Mlabel provided, or is unable to support MPLS a Call-Disconnect-Notify is returned to the peer. If the Mlabel provided cannot be used by the peer, the Call- Disconnect-Notify message will include the Multi-Protocol Label AVP as provided in the message that caused the Call-Disconnect-Notify. 3.0 References [1] W.M. Townsley, A. J. Valencia, A. Rubens, G.S. Pall, G. Zorn, B. Palter, "Layer Two Tunneling Protocol (L2TP)", draft-ietf-pppext-l2tp-13.txt, Work in Progress, January 1999. [2] E. Rosen, Y. Rekhter, D. Tappan, D. Farinacci, G. Fedorkow, T. Li, A. Conta, "MPLS Label Stack Encoding", draft-ietf-mpls-label-encaps-03.txt, Work in Progress, March 1999. [3] E. Rosen, A. Viswanathan, R. Callon, "Multiprotocol Label Switching Architecture", draft-ietf-mpls-arch-04.txt, Work in Progress, February 1999. [4] R. Callon, P. Doolan, N. Feldman, A. Fredette, G. Swallow, A. Viswanathan, "A Framework for Multiprotocol Label Switching", draft-ietf-mpls-framework-02.txt, Work in Progress, November 1997. Calhoun, Peirce expires August 1999 [Page 4] INTERNET DRAFT February 1999 [5] Andersson, Doolan, Feldman, Fredette, Thomas, "LDP Specification", draft-ietf-mpls-ldp-03.txt. Work in Progress, January 1999. [6] Rekhter, Rosen, "Carrying Label Information in BGP-4", draft-ietf-mpls-bgp4-mpls-02.txt, Work in Progress, August 1999. 4.0 Acknowledgements The Authors would like to acknowledge John Shriver for his useful comments to an earlier version of this document. 5.0 Authors' Addresses Questions about this memo can be directed to: Pat R. Calhoun Network and Security Research Center, Sun Labs Sun Microsystems, Inc. 15 Network Circle Menlo Park, California, 94025 USA Phone: 1-650-786-7733 Fax: 1-650-786-6445 E-mail: pcalhoun@eng.sun.com Ken Peirce 3Com Corporation 1800 Central Ave. Mount Prospect, Il, 60056 Phone: 1-847-342-6894 Fax: 1-847-222-2424 E-mail: Ken_Peirce@mw.3com.com Calhoun, Peirce expires August 1999 [Page 5]