Movatterモバイル変換

Network Working Group                                         L. MartiniRequest for Comments: 4863                                    G. SwallowCategory: Standards Track                            Cisco Systems, Inc.                                                                May 2007Wildcard Pseudowire TypeStatus 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 IETF Trust (2007).Abstract   Pseudowire signaling requires that the Pseudowire Type (PW Type) be   identical in both directions.  For certain applications the   configuration of the PW Type is most easily accomplished by   configuring this information at just one PW endpoint.  In any form of   LDP-based signaling, each PW endpoint must initiate the creation of a   unidirectional LSP.  In order to allow the initiation of these two   LSPs to remain independent, a means is needed for allowing the PW   endpoint (lacking a priori knowledge of the PW Type) to initiate the   creation of an LSP.  This document defines a Wildcard PW Type to   satisfy this need.Table of Contents1. Introduction ....................................................21.1. Conventions and Terminology ................................22. Wildcard PW Type ................................................33. Procedures ......................................................33.1. Procedures When Sending the Wildcard FEC ...................33.2. Procedures When Receiving the Wildcard FEC .................34. Security Considerations .........................................45. IANA Considerations .............................................46. References ......................................................46.1. Normative References .......................................46.2. Informative References .....................................4Martini & Swallow           Standards Track                     [Page 1]

RFC 4863                Wildcard Pseudowire Type                May 20071.  Introduction   Pseudowire signaling requires that the Pseudowire Type (PW Type) be   identical in both directions.  For certain applications the   configuration of the PW Type is most easily accomplished by   configuring this information at just one PW endpoint.  In any form of   LDP-based signaling, each PW endpoint must initiate the creation of a   unidirectional LSP.   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 PW endpoint   that lacks configuration must wait to receive a Label Mapping message   in order to learn the PW Type, prior to signaling its unidirectional   LSP.   For certain applications this can become particularly onerous.  For   example, suppose that an ingress Provider Edge (PE) is serving as   part of a gateway function between a layer 2 network and layer 2   attachment circuits on remote PEs.  Suppose further that the initial   setup needs to be initiated from the layer 2 network, but the layer 2   signaling does not contain sufficient information to determine the PW   Type.  However, this information is known at the PE supporting the   targeted attachment circuit.   In this situation, it is often desirable to allow the initiation of   the two LSPs that compose a pseudowire to remain independent.  A   means is needed for allowing a PW endpoint (lacking a priori   knowledge of the PW Type) to initiate the creation of an LSP.  This   document defines a wildcard PW Type to satisfy this need.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 inRFC 2119 [KEYWORDS].   This document introduces no new terminology.  However, it assumes   that the reader is familiar with the terminology contained in   [CONTROL] andRFC 3985, "Pseudo Wire Emulation Edge-to-Edge (PWE3)   Architecture" [ARCH].Martini & Swallow           Standards Track                     [Page 2]

RFC 4863                Wildcard Pseudowire Type                May 20072.  Wildcard PW Type   In order to allow a PE to initiate the signaling exchange for a   pseudowire without knowing the pseudowire type, a new PW Type is   defined.  The codepoint is 0x7FFF.  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       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.  Procedures3.1.  Procedures When Sending the Wildcard FEC   When a PE that is not configured to use a specific PW Type for a   particular pseudowire wishes to signal an LSP for that pseudowire, it   sets the PW Type to "wildcard".  This indicates that the target PE   should determine the PW Type for this pseudowire.   When a Label Mapping message is received for the pseudowire, the PE   checks the PW Type.   If the PW Type can be supported, the PE uses this as the PW Type for   both directions.   If the PW Type cannot be supported or is "wildcard", it MUST respond   to this message with a Label Release message with an LDP Status Code   of "Generic Misconfiguration Error".  Further actions are beyond the   scope of this document, but could include notifying the associated   application (if any) or notifying network management.3.2.  Procedures When Receiving the Wildcard FEC   When a targeted PE receives a Label Mapping message indicating the   wildcard PW Type, it follows the normal procedures for checking the   Attachment Group Identifier (AGI) and Target Attachment Individual   Identifier (TAII) values.  If the targeted PE is not configured to   use a specific, non-wildcard PW Type, it MUST respond to this message   with a Label Release message with an LDP Status Code of "Generic   Misconfiguration Error".   Otherwise, it treats the Label Mapping message as if it had indicated   the PW Type it is configured to use.Martini & Swallow           Standards Track                     [Page 3]

RFC 4863                Wildcard Pseudowire Type                May 20074.  Security Considerations   This document has little impact on 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   security considerations of [CONTROL], in general, and those   pertaining to the Generalized PWid FEC Element, in particular.5.  IANA Considerations   IANA has made the following allocation from the IETF consensus range   of the "Pseudowire Type" registry as defined in [IANA].         PW Type        Description         0x7FFF         Wildcard6.  References6.1.  Normative References   [KEYWORDS]   Bradner, S., "Key words for use in RFCs to Indicate                Requirement Levels",BCP 14,RFC 2119, March 1997.   [CONTROL]    Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T.,                and G. Heron, "Pseudowire Setup and Maintenance Using                the Label Distribution Protocol (LDP)",RFC 4447, April                2006.   [IANA]       Martini, L., "IANA Allocations for Pseudowire Edge to                Edge Emulation (PWE3)",BCP 116,RFC 4446, April 2006.6.2.  Informative References   [ARCH]       Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire                Emulation Edge-to-Edge (PWE3) Architecture",RFC 3985,                March 2005.Martini & Swallow           Standards Track                     [Page 4]

RFC 4863                Wildcard Pseudowire Type                May 2007Authors' 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.comMartini & Swallow           Standards Track                     [Page 5]

RFC 4863                Wildcard Pseudowire Type                May 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights 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; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 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 athttp://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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Martini & Swallow           Standards Track                     [Page 6]