PCE Working Group D. Dhody Internet-Draft F. Zhang Intended status: Standards Track X. Zhang Expires: August 2, 2014 Huawei Technologies V. Lopez O. Gonzalez de Dios Telefonica I+D January 29, 2014 PCEP Extensions for Receiving SRLG Information draft-dhody-pce-recv-srlg-00 Abstract The Path Computation Element (PCE) provides functions of path computation in support of traffic engineering in networks controlled by Multi-Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS). This document provides extensions for the Path Computation Element Protocol (PCEP) to receive Shared Risk Link Group (SRLG) information during path computation via encoding this information in the path computation reply message. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on August 2, 2014. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. Dhody, et al. Expires August 2, 2014 [Page 1] Internet-Draft PCE-SRLG January 2014 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 4 4. Extension to PCEP . . . . . . . . . . . . . . . . . . . . . . 4 4.1. The Extension of the RP Object . . . . . . . . . . . . . 4 4.2. SRLG Subobject in ERO . . . . . . . . . . . . . . . . . . 4 5. Other Considerations . . . . . . . . . . . . . . . . . . . . 5 5.1. Backward Compatibility . . . . . . . . . . . . . . . . . 5 5.2. Confidentiality via PathKey . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Manageability Considerations . . . . . . . . . . . . . . . . 6 7.1. Control of Function and Policy . . . . . . . . . . . . . 6 7.2. Information and Data Models . . . . . . . . . . . . . . . 6 7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 6 7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 6 7.5. Requirements On Other Protocols . . . . . . . . . . . . . 6 7.6. Impact On Network Operations . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8.1. New Subobjects for the ERO Object . . . . . . . . . . . . 7 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 9 1. Introduction As per [RFC4655], PCE based path computation model is deployed in large, multi-domain, multi-region, or multi-layer networks. In such case PCEs may cooperate with each other to provide end to end optimal path. It is important to understand which TE links in the network might be at risk from the same failures. In this sense, a set of links may constitute a 'shared risk link group' (SRLG) if they share a resource Dhody, et al. Expires August 2, 2014 [Page 2] Internet-Draft PCE-SRLG January 2014 whose failure may affect all links in the set [RFC4202]. H-LSP (Hierarchical LSP) or S-LSP (Stitched LSP) can be used for carrying one or more other LSPs as described in [RFC4206] and [RFC6107]. H-LSP and S-LSP may be computed by PCE(s) and further form as a TE link. The SRLG information of such LSPs can be obtained during path computation itself and encoded in the PCEP Path Computation Reply (PCRep) message. [I-D.zhang-ccamp-gmpls-uni-app] describes the use of a PCE for end to end User-Network Interface (UNI) path computation. Note that [I-D.ietf-ccamp-rsvp-te-srlg-collect] specifies a extension to Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) where SRLG information is collected at the time of signaling. But in case a PCE or cooperating PCEs are used for path computation it is recommended that SRLG information is provided by the PCE(s). [I-D.farrel-interconnected-te-info-exchange] describes a scaling problem with SRLGs in multi-layer environment and introduce a concept of Macro SRLG. Lower layer SRLG is received at the time of path computation and can be the basis to generate such a Macro SRLG at the PCE. 1.1. Requirements Language 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. Terminology The following terminology is used in this document. CPS: Confidential Path Segment. A segment of a path that contains nodes and links that the policy requires not to be disclosed outside the domain. PCE: Path Computation Element. An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints. SRLG: Shared Risk Link Group. UNI: User-Network Interface. Dhody, et al. Expires August 2, 2014 [Page 3] Internet-Draft PCE-SRLG January 2014 3. PCEP Requirements Following key requirements are identified for PCEP to receive SRLG information during path computation: SRLG Indication: The PCEP speaker must be capable of indicating whether the SRLG information of the path should be received during the path computation procedure. SRLG: If requested, the SRLG information should be received during the path computation and encoded in the PCRep message. Cooperating PCEs [RFC4655] with inter-PCE Communication work together to provide the end to end optimal path as well as the SRLG information of this path. During inter-domain or inter-layer path computation, the aggregating PCE (Parent PCE [RFC6805] or Ingress PCE(1) [RFC5441] or Higher-Layer PCE [RFC5623]) should receive the SRLG information of path segments from other PCEs and provide the end to end SRLG information of the optimal path to the Path Computation Client (PCC). 4. Extension to PCEP This document extends the existing RP (Request Parameters) object [RFC5440] so that a PCEP speaker can request SRLG information during path computation. The SRLG subobject maybe carried inside the Explicit Route Object (ERO) in the PCRep message. 4.1. The Extension of the RP Object This document adds the following flags to the RP Object: S (SRLG - 1 bit): when set, in a PCReq message, this indicates that the SRLG information of the path should be provided in the PCRep message. Otherwise, when cleared, this indicates that the SRLG information should not be included in the PCRep message. In a PCRep message, when the S bit is set this indicates that the returned path in ERO also carry the SRLG information; otherwise (when the S bit is cleared), the returned path does not carry SRLG information. 4.2. SRLG Subobject in ERO As per [RFC5440], ERO is used to encode the path and is carried within a PCRep message to provide the computed path when computation was successful. Dhody, et al. Expires August 2, 2014 [Page 4] Internet-Draft PCE-SRLG January 2014 The SRLG of a path is the union of the SRLGs of the links in the path [RFC4202]. The SRLG subobject is defined in [I-D.ietf-ccamp-rsvp-te-srlg-collect], as shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SRLG ID 1 (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ...... ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SRLG ID n (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The meaning and description of Type, Length and SRLG ID can be found in [I-D.ietf-ccamp-rsvp-te-srlg-collect]. Bits in the Flags field are ignored. The SRLG subobject should be encoded inside the ERO object in the PCRep message when the S-Bit (SRLG) is set in the PCReq message. 5. Other Considerations 5.1. Backward Compatibility If a PCE receives a request and the PCE does not understand the new SRLG flag in the RP object, then the PCE SHOULD reject the request. If PCEP speaker receives a PCRep message with SRLG subobject that it does not support or recognize, it must act according to the existing processing rules. 5.2. Confidentiality via PathKey [RFC5520] defines a mechanism to hide the contents of a segment of a path, called the Confidential Path Segment (CPS). The CPS may be replaced by a path-key that can be conveyed in the PCEP and signaled within in a RSVP-TE ERO. When path-key confidentiality is used, encoding SRLG information in PCRep along with the path-key could be useful to compute a SRLG disjoint backup path at the later instance. Dhody, et al. Expires August 2, 2014 [Page 5] Internet-Draft PCE-SRLG January 2014 6. Security Considerations This document does not add any new security concerns beyond those discussed in [RFC5440]. 7. Manageability Considerations 7.1. Control of Function and Policy Mechanisms defined in this document do not imply any new control of function and policy requirements. 7.2. Information and Data Models [I-D.ietf-pce-pcep-mib] describes the PCEP MIB, there are no new MIB Objects for this document. 7.3. Liveness Detection and Monitoring Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in [RFC5440]. 7.4. Verify Correct Operations Mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [RFC5440]. 7.5. Requirements On Other Protocols Mechanisms defined in this document do not imply any new requirements on other protocols. 7.6. Impact On Network Operations Mechanisms defined in this document do not have any impact on network operations in addition to those already listed in [RFC5440]. 8. IANA Considerations IANA assigns values to PCEP parameters in registries defined in [RFC5440]. IANA is requested to make the following additional assignments. Dhody, et al. Expires August 2, 2014 [Page 6] Internet-Draft PCE-SRLG January 2014 8.1. New Subobjects for the ERO Object IANA has previously assigned an Object-Class and Object-Type to the ERO carried in PCEP messages [RFC5440]. IANA also maintains a list of subobject types valid for inclusion in the ERO. IANA is requested to assign one new subobject types for inclusion in the ERO as follows: Subobject Meaning Reference 34 (TBD) SRLG sub-object This document 9. Acknowledgments TBD. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. 10.2. Informative References [RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005. [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths", RFC 5441, April 2009. [RFC5520] Bradford, R., Vasseur, JP., and A. Farrel, "Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Path-Key-Based Mechanism", RFC 5520, April 2009. Dhody, et al. Expires August 2, 2014 [Page 7] Internet-Draft PCE-SRLG January 2014 [RFC5623] Oki, E., Takeda, T., Le Roux, JL., and A. Farrel, "Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic Engineering", RFC 5623, September 2009. [RFC6107] Shiomoto, K. and A. Farrel, "Procedures for Dynamically Signaled Hierarchical Label Switched Paths", RFC 6107, February 2011. [RFC6805] King, D. and A. Farrel, "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", RFC 6805, November 2012. [I-D.ietf-ccamp-rsvp-te-srlg-collect] Zhang, F., Li, D., Dios, O., Margaria, C., and M. Hartley, "RSVP-TE Extensions for Collecting SRLG Information", draft-ietf-ccamp-rsvp-te-srlg-collect-03 (work in progress), September 2013. [I-D.ietf-pce-pcep-mib] Koushik, K., Stephan, E., Zhao, Q., King, D., and J. Hardwick, "PCE communication protocol (PCEP) Management Information Base", draft-ietf-pce-pcep-mib-06 (work in progress), January 2014. [I-D.farrel-interconnected-te-info-exchange] Farrel, A., Drake, J., Bitar, N., Swallow, G., and D. Ceccarelli, "Problem Statement and Architecture for Information Exchange Between Interconnected Traffic Engineered Networks", draft-farrel-interconnected-te-info- exchange-02 (work in progress), October 2013. [I-D.zhang-ccamp-gmpls-uni-app] Zhang, F., Dios, O., Farrel, A., Zhang, X., and D. Ceccarelli, "Applicability of Generalized Multiprotocol Label Switching (GMPLS) User-Network Interface (UNI)", draft-zhang-ccamp-gmpls-uni-app-04 (work in progress), July 2013. Dhody, et al. Expires August 2, 2014 [Page 8] Internet-Draft PCE-SRLG January 2014 Appendix A. Contributor Addresses Udayasree Palle Huawei Technologies Leela Palace Bangalore, Karnataka 560008 INDIA EMail: udayasree.palle@huawei.com Avantika Huawei Technologies Leela Palace Bangalore, Karnataka 560008 INDIA EMail: avantika.sushilkumar@huawei.com Authors' Addresses Dhruv Dhody Huawei Technologies Leela Palace Bangalore, Karnataka 560008 INDIA EMail: dhruv.ietf@gmail.com Fatai Zhang Huawei Technologies Bantian, Longgang District Shenzhen, Guangdong 518129 P.R.China EMail: zhangfatai@huawei.com Xian Zhang Huawei Technologies Bantian, Longgang District Shenzhen, Guangdong 518129 P.R.China EMail: zhang.xian@huawei.com Dhody, et al. Expires August 2, 2014 [Page 9] Internet-Draft PCE-SRLG January 2014 Victor Lopez Telefonica I+D Don Ramon de la Cruz 82-84 Madrid 28045 Spain EMail: vlopez@tid.es Oscar Gonzalez de Dios Telefonica I+D Don Ramon de la Cruz 82-84 Madrid 28045 Spain EMail: ogondio@tid.es Dhody, et al. Expires August 2, 2014 [Page 10]