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Network Working Group                                          L. BergerRequest for Comments: 4003                                Movaz NetworksUpdates:3473                                              February 2005Category: Standards TrackGMPLS Signaling Procedure for Egress ControlStatus 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 (2005).Abstract   This document clarifies the procedures for the control of the label   used on an output/downstream interface of the egress node of a Label   Switched Path (LSP).  This control is also known as "Egress Control".   Support for Egress Control is implicit in Generalized Multi-Protocol   Label Switching (GMPLS) Signaling.  This document clarifies the   specification of GMPLS Signaling and does not modify GMPLS signaling   mechanisms and procedures.1.  Background   The ability to control the label used on the output/downstream   interface of an egress node was one of the early requirements for   GMPLS.  In the initial GMPLS documents, this was called "Egress   Control".  As the GMPLS documents progressed, the ability to control   a label on an egress interface was generalized to support control of   a label on any interface.  This generalization is seen inSection 6   of [RFC3471] andSection 5.1 of [RFC3473].  When this functionality   was generalized, the procedures to support control of a label at the   egress were also generalized.  Although the result was intended to   cover egress control, this intention is not clear to all.  This note   reiterates the procedures to cover control of a label used on an   egress output/downstream interface.Berger                      Standards Track                     [Page 1]

RFC 4003      GMPLS Signaling Procedure for Egress Control February 2005   For context, the following is the text from the GMPLS signalling   document dated June 2000 about how ERO (Explicit Route Object) for   egress control:      6. Egress Control      The LSR at the head-end of an LSP can control the termination of      the LSP by using the ERO.  To terminate an LSP on a particular      outgoing interface of the egress LSR, the head-end may specify the      IP address of that interface as the last element in the ERO,      provided that interface has an associated IP address.      There are cases where the use of IP address doesn't provide enough      information to uniquely identify the egress termination.  One case      is when the outgoing interface on the egress LSR is a component      link of a link bundle.  Another case is when it is desirable to      "splice" two LSPs together, i.e., where the tail of the first LSP      would be "spliced" into the head of the second LSP.  This last      case is more likely to be used in the non-PSC classes of links.      6.2. Procedures      The Egress Label subobject may appear only as the last subobject      in the ERO/ER.  Appearance of this subobject anywhere else in the      ERO/ER is treated as a "Bad strict node" error.      During an LSP setup, when a node processing the ERO/RR performs      Next Hop selection finds that the second subobject is an Egress      Label Subobject, the node uses the information carried in this      subobject to determine the handling of the data received over that      LSP.  Specifically, if the Link ID field of the subobject is non      zero, then this field identifies a specific (outgoing) link of the      node that should be used for sending all the data received over      the LSP.  If the Label field of the subobject is not Implicit NULL      label, this field specifies the label that should be used as an      outgoing label on the data received over the LSP.      Procedures by which an LSR at the head-end of an LSP obtains the      information needed to construct the Egress Label subobject are      outside the scope of this document.2.  Egress Control Procedures   This section is intended to complement Sections5.1.1 and5.2.1 of   [RFC3473].  The procedures described in those sections are not   modified.  This section clarifies procedures related to the label   used on an egress output/downstream interface.Berger                      Standards Track                     [Page 2]

RFC 4003      GMPLS Signaling Procedure for Egress Control February 2005   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 [RFC2119].2.1.  ERO Procedures   Egress Control occurs when the node processing an ERO is the egress   and the ERO contains one or more subobjects related to the   output/downstream interface.  In this case, the outgoing/downstream   interface is indicated in the ERO as the last listed local interface.   Note that an interface may be numbered or unnumbered.   To support Egress Control, an egress checks to see whether the   received ERO contains an outgoing/downstream interface.  If it does,   the type of the subobject or subobjects following the interface is   examined.  If the associated LSP is unidirectional, one subobject is   examined.  Two subobjects are examined for bidirectional LSPs.  If   the U-bit of the subobject being examined is clear (0), then the   value of the label MUST be used for transmitting traffic associated   with the LSP on the indicated outgoing/downstream interface.   If the U-bit of the subobject being examined is set (1), then the   value of the label is used for upstream traffic associated with the   bidirectional LSP.  Specifically, the label value will be used for   the traffic associated with the LSP that will be received on the   indicated outgoing/downstream interface.   Per [RFC3473], any errors encountered while processing the ERO,   including if the listed label(s) are not acceptable or cannot be   supported in forwarding, SHOULD result in the generation of a PathErr   message with the error code "Routing Error" and error value of "Bad   Explicit Route Object".2.2.  RRO Procedures   If an ERO is used to specify outgoing interface information at the   egress and label recording is indicated for the LSP, the egress   should include the specified interface information and the specified   label or labels in the corresponding RRO (Route Record Object).3.  Security Considerations   This document clarifies procedures defined in [RFC3473] but does not   define any new procedures.  As such, no new security considerations   are introduced.Berger                      Standards Track                     [Page 3]

RFC 4003      GMPLS Signaling Procedure for Egress Control February 20054.  Acknowledgments   Valuable comments and input were received from Adrian Farrel, Alan   Kullberg, and Dimitri Papadimitriou.5.  Normative References   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate             Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching             (GMPLS) Signaling Functional Description",RFC 3471,             January 2003.   [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching             (GMPLS) Signaling Resource ReserVation Protocol-Traffic             Engineering (RSVP-TE) Extensions",RFC 3473, January 2003.Author's Address   Lou Berger   Movaz Networks, Inc.   7926 Jones Branch Drive   Suite 615   McLean VA, 22102   Phone:  +1 703 847-1801   EMail:  lberger@movaz.comBerger                      Standards Track                     [Page 4]

RFC 4003      GMPLS Signaling Procedure for Egress Control February 2005Full Copyright Statement   Copyright (C) The Internet Society (2005).   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 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 IETF's procedures with respect to rights in IETF 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.Berger                      Standards Track                     [Page 5]