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IETF RFC 4003

GMPLS Signaling Procedure for Egress Control

Last modified on Wednesday, February 9th, 2005

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Network Working Group                                          L. Berger
Request for Comments: 4003                                Movaz Networks
Updates: 3473                                              February 2005
Category: Standards Track 


              GMPLS Signaling Procedure for Egress Control

 Status 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 © 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 in Section 6
   of [RFC 3471] and Section 5.1 of [RFC 3473].  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 top


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 Sections 5.1.1 and 5.2.1 of [RFC 3473]. 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 top

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 [RFC 2119]. 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 [RFC 3473], 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 [RFC 3473] but does not define any new procedures. As such, no new security considerations are introduced. Berger Standards Track PAGE 3 top

RFC 4003 GMPLS Signaling Procedure for Egress Control February 2005 4. Acknowledgments Valuable comments and input were received from Adrian Farrel, Alan Kullberg, and Dimitri Papadimitriou. 5. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 3471] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC 3473] 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.com Berger Standards Track PAGE 4 top

RFC 4003 GMPLS Signaling Procedure for Egress Control February 2005 Full Copyright Statement Copyright © The Internet Society (2005). 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. 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 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Berger Standards Track PAGE 5 top

GMPLS Signaling Procedure for Egress Control RFC TOTAL SIZE: 10306 bytes PUBLICATION DATE: Wednesday, February 9th, 2005 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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