Network Working Group Luca Martini Internet Draft Cisco Systems, Inc. Category: Standards Track Expiration Date: September 2006 George Swallow Cisco Systems, Inc. March 2006 Target Choice of Pseudowire Type draft-ietf-pwe3-wildcard-pw-type-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract The Generalized PWid FEC permits a procedure know as single-sided signaling. In this procedure, one end of the pseudowire always initiates the pseudowire setup and the target of that label mapping message only signals in response. For certain applications of pseudowires it is advantages to configure the pseudowire type (PW type) at the target of the initial label mapping message. This document specifies a means of doing this. Martini & Swallow Standards Track [Page 1] Internet Draft draft-ietf-pwe3-wildcard-pw-type-01.txt March 2006 Contents 1 Introduction .............................................. 3 1.1 Conventions and Terminology ............................... 3 2 Wildcard PW Type .......................................... 3 3 Procedures ................................................ 4 4 Security Considerations ................................... 4 5 IANA Considerations ....................................... 5 6 References ................................................ 5 Martini & Swallow Standards Track [Page 2] Internet Draft draft-ietf-pwe3-wildcard-pw-type-01.txt March 2006 1. Introduction Pseudowire signaling is defined in "Pseudowire Setup and Maintenance using the Label Distribution Protocol" [CONTROL]. The Generalized PWid FEC permits a procedure know as single-sided signaling as docu- mented in "Provisioning, Autodiscovery, and Signaling in L2VPNs" [L2VPNSIG]. In this procedure, one end of the pseudowire always ini- tiates the pseudowire setup. The target router of that initial label mapping message only signals in response. For certain applications of pseudowires it is advantages to configure the pseudowire type (PW_Type) at the target of the initial label mapping message. For certain applications where an ingress PE is serving as part of a gateway function between a layer two network and layer two attachment circuits on remote PEs, the initial setup may be caused by signaling from the layer 2 network. However, the layer 2 signaling may not contain sufficient information to determine the PW type. This infor- mation, however would be known at the PE supporting the targeted attachment circuit. By the procedures of [CONTROL] both label mapping messages must carry the PW type and the two unidirectional mapping messages must be in agreement. Thus within the current procedures the initiator must specify the PW_Type. 1.1. Conventions and Terminology 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 RFC 2119 [KEYWORDS]. This document introduces no new terminology. However it assumes that the reader is familiar with the terminology contained in [CONTROL] and RFC 3985, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architec- ture" [ARCH]. 2. Wildcard PW Type In order to allow a PE to initiate the signaling exchange for a pseu- dowire without knowing the pseudowire type, a new PW type is defined. The codepoint is 0x7fff [to be assigned by IANA]. The semantics are the following: 1. To the targeted PE, this value indicates that it is to determine the PW type (for both directions) and signal that in a label Martini & Swallow Standards Track [Page 3] Internet Draft draft-ietf-pwe3-wildcard-pw-type-01.txt March 2006 mapping message back to the initiating PE. 2. For the procedures of [CONTROL] this PW type is interpreted to match any PW type other than itself. That is the targeted PE may respond with any valid PW type other than the Wildcard PW type. 3. Procedures The initiating PE indicates a PW type of "wildcard" to indicated to the target PE that it should determine the type for this pseudowire. When the targeted PE receives the wildcard PW type, it follows the normal procedures in checking the AGI and TAII values. If a label mapping message has already been issued, it MUST respond to this mes- sage with a Label_Release message. If PE2 cannot map the TAI to one of its Forwarders, then PE2 sends a Label Release message to PE1, with a Status Code of "Unas- signed/Unrecognized TAI", and the processing of the Label Mapping message is complete. Otherwise, it responds with a Label_Mapping message with the configured PW type. When the initiating PE receives a Label_Mapping message from the tar- geted PE it uses this as the PW type for both directions. If it is unable to support the PW type it MUST send a Label_Release message for the label allocated in the Label_Mapping message which initiated the exchange. It also SHOULD respond to the received Label_Mapping message with a Label_Release message. Further actions are beyond the scope of this document but could include notifying the associated application (if any) or notifying network management. 4. Security Considerations This draft has little impact the security aspects of [CONTROL]. The message exchanges remain the same. However a malicious agent attempting to connect to an access circuit would require one less piece of information. To mitigate against this, a pseudowire control entity receiving a request containing the wildcard FEC type SHOULD only proceed with setup if explicitly configured to do so for the particular AI in the TAI. Further, the reader should note the secu- rity considerations of [CONTROL] in general and those pertaining to the Generalized ID FEC Element in particular. Martini & Swallow Standards Track [Page 4] Internet Draft draft-ietf-pwe3-wildcard-pw-type-01.txt March 2006 5. IANA Considerations This document requests the following allocation be made from the IETF consensus range of the "Pseudowire Type" registry as defined in [IANA]. PW type Description 0x7FFF (TBA) Wildcard 6. References Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [ARCH] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005 [CONTROL] Martini, L., et al., "Pseudowire Setup and Maintenance using the Label Distribution Protocol", draft-ietf-pwe3-control-protocol-17.txt, June 2005. [L2VPNSIG] Rosen, E., et al., "Provisioning, Autodiscovery, and Signaling in L2VPNs", draft-ietf-l2vpn-signaling-07.txt, March 2006. [IANA] Martini, L., and Townsley, M., "IANA Allocations for pseudo Wire Edge to Edge Emulation (PWE3)", draft-ietf-pwe3-iana-allocation-15.txt, June 2005. Authors' Addresses Luca Martini Cisco Systems 9155 East Nichols Avenue, Suite 400 Englewood, CO, 80112 Email: lmartini@cisco.com George Swallow Cisco Systems 1414 Massachusetts Ave, Boxborough, MA 01719 Email: swallow@cisco.com Martini & Swallow Standards Track [Page 5] Internet Draft draft-ietf-pwe3-wildcard-pw-type-01.txt March 2006 Copyright Notice Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Martini & Swallow Standards Track [Page 6]