Network Working Group E. Oki Internet Draft NTT Category: Standards Track J-L Le Roux Created: February 18, 2008 France Telecom Expires: August 18, 2008 A. Farrel Old Dog Consulting Extensions to the Path Computation Element communication Protocol (PCEP) for Inter-Layer MPLS and GMPLS Traffic Engineering draft-ietf-pce-inter-layer-ext-00.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/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract The Path Computation Element (PCE) provides path computation functions in support of traffic engineering in Multi-Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. MPLS and GMPLS networks may be constructed from layered service networks. It is advantageous for overall network efficiency to provide end-to-end traffic engineering across multiple network layers through a process called inter-layer traffic engineering. PCE is a candidate solution for such requirements. The PCE communication Protocol (PCEP) is designed as a communication protocol between Path Computation Clients (PCCs) and PCEs. This document presents PCEP extensions for inter-layer traffic engineering. Oki, Le Roux, and Farrel [Page 1] PCEP Extensions for Inter-Layer TE February 2008 Table of Contents 1. Introduction.................................................2 2. Overview of PCE-Based Inter-Layer Path Computation...........3 3. Protocol Extensions..........................................4 3.1. INTER-LAYER Object.........................................4 3.2. SWITCH-LAYER Object........................................5 3.2.1. REQ-ADAP-CAP Object......................................6 4. Procedure....................................................7 4.1. Path Computation Request...................................7 4.2. Path Computation Reply.....................................8 5. Updated Format of PCEP Messages..............................8 6. Manageability considerations.................................9 7. IANA considerations..........................................9 8. Security Considerations.....................................10 9. Acknowledgments.............................................10 10. References.................................................10 10.1. Normative Reference......................................10 10.2. Informative Reference....................................11 11. Authors' Addresses.........................................11 12. Intellectual Property Statement............................11 Conventions used in this document 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 [RFC2119]. 1. Introduction The Path Computation Element (PCE) defined in [RFC4655] is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. A Path Computation Client (PCC) may make requests to a PCE for paths to be computed. A network may comprise multiple layers. These layers may represent separations of technologies (e.g., packet switch capable (PSC), time division multiplex (TDM), lambda switch capable (LSC)) [RFC3945], separation of data plane switching granularity levels (e.g., PSC-1 and PSC-2, or VC4 and VC12) [MLN-REQ], or a distinction between client and server networking roles (e.g., commercial or administrative separation of client and server networks). In this multi-layer network, Label Switched Paths (LSPs) in lower layers are used to carry upper-layer LSPs. The network topology formed by lower-layer LSPs and advertised to the higher layer is called a Virtual Network Topology (VNT) [MLN-REQ]. Oki, Le Roux, and Farrel [Page 2] PCEP Extensions for Inter-Layer TE February 2008 It is important to optimize network resource utilization globally, i.e., taking into account all layers, rather than optimizing resource utilization at each layer independently. This allows better network efficiency to be achieved. This is what we call inter-layer traffic engineering. This includes mechanisms allowing the computation of end-to-end paths across layers (known as inter- layer path computation), and mechanisms for control and management of the VNT by setting up and releasing LSPs in the lower layers [MLN-REQ]. PCE can provide a suitable mechanism for resolving inter-layer path computation issues. The framework for applying the PCE-based path computation architecture to inter-layer traffic engineering is described in [PCE-INTER-LAYER-FRWK]. The PCE communication protocol (PCEP) is designed as a communication protocol between PCCs and PCEs and is defined in [PCEP]. A set of requirements for PCEP extensions to support inter- layer traffic engineering is described in [PCE-INTER-LAYER-REQ]. This document presents PCEP extensions for inter-layer traffic engineering that satisfy the requirements described in [PCE-INTER- LAYER-REQ]. 2. Overview of PCE-Based Inter-Layer Path Computation [RFC4206] defines a way to signal a higher-layer LSP which has an explicit route that includes hops traversed by LSPs in lower layers. The computation of end-to-end paths across layers is called Inter- Layer Path Computation. A Label Switching Router (LSR) in the higher-layer might not have information on the lower-layer topology, particularly in an overlay or augmented model [RFC3945], and hence may not be able to compute an end-to-end path across layers. PCE-based inter-layer path computation consists of using one or more PCEs to compute an end-to-end path across layers. This could be achieved by relying on a single PCE that has topology information about multiple layers and can directly compute an end- to-end path across layers considering the topology of all of the layers. Alternatively, the inter-layer path computation could be performed using multiple cooperating PCEs where each PCE has information about the topology of one or more layers (but not all layers) and where the PCEs collaborate to compute an end-to-end path. [PCE-INTER-LAYER-FRWK] describes models for inter-layer path computation in more detail. Oki, Le Roux, and Farrel [Page 3] PCEP Extensions for Inter-Layer TE February 2008 3. Protocol Extensions This section describes PCEP extensions for inter-layer path computation. Three new objects are defined: the INTER-LAYER object, the SWITCH-LAYER object, and the REQ-ADAP-CAP object. 3.1. INTER-LAYER Object The INTER-LAYER object is optional and can be used in PCReq and PCRep messages. In a PCReq message, the INTER-LAYER object indicates whether inter- layer path computation is allowed, the type of path to be computed, and whether nested signaling is allowed. When the INTER-LAYER object is absent from a PCReq message, the receiving PCE SHOULD process as though inter-layer path computation had been explicitly disallowed (I-bit set to zero - see below). In a PCRep message, the INTER-LAYER object indicates whether inter- layer path computation has been performed, the type of path that has been computed, and whether nested signaling is used. When a PCReq message includes more than one request, an INTER-LAYER object is used per request. When a PCRep message includes more than one path per request, an INTER-LAYER object is used per path. INTER-LAYER Object-Class is to be assigned by IANA (recommended value=18) INTER-LAYER Object-Type is to be assigned by IANA (recommended value=1) The format of the INTER-LAYER object body is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |N|I| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I flag (1 bit): the I flag is used by a PCC in a PCReq message to indicate to a PCE whether an inter-layer path is allowed. When the I flag is set (one), the PCE MAY perform inter-layer path computation and return an inter-layer path. When the flag is clear (zero), the path that is returned MUST NOT be an inter-layer path. The I flag is used by a PCE in a PCRep message to indicate to a PCC whether the path returned is an inter-layer path. When the I flag is set (one), the path is an inter-layer path. When it is clear Oki, Le Roux, and Farrel [Page 4] PCEP Extensions for Inter-Layer TE February 2008 (zero), the path is contained within a single layer either because inter-layer path computation was not performed or because a mono- layer path was found notwithstanding the use of inter-layer path computation. N flag (1 bit): the N flag is used by a PCC in a PCReq message to indicate to a PCE whether nested signaling is allowed. When the N flag is set (one), nested signaling is allowed. When it is clear (zero), nested signaling is not allowed. The N flag is used by a PCE in a PCRep message to indicate to a PCC whether nested signaling is required to support the returned path. When the N flag is set (one), nested signaling is required. When it is clear (zero), nested signaling is not required. Note that nested signaling is used to support hierarchical [RFC4206] or stitched [LSP-STITCH] LSPs according to the physical attributes of the network layers. If the I flag is clear (zero), the N flag has no meaning and MUST be ignored. Reserved bits of the INTER-LAYER object SHOULD be transmitted as zero and SHOULD be ignored on receipt. A PCE that forwards a path computation request to other PCEs SHOULD preserve the settings of reserved bits in the PCReq messages it sends and in the PCRep messages it forwards to PCCs. 3.2. SWITCH-LAYER Object The SWITCH-LAYER object is optional on a PCReq message and specifies switching layers in which a path MUST, or MUST NOT be established. A switching layer is expressed as a switching type and encoding type. The SWITCH-LAYER object MUST NOT be used on a PCRep unless an INTER-LAYER object is also present on the PCReq message. The SWITCH-LAYER object is optional on a PCRep message, where it is used with the NO-PATH object in the case of unsuccessful path computation to indicate the set of constraints that could not be satisfied. SWTICH-LAYER Object-Class is to be assigned by IANA (recommended value=19) SWTICH-LAYER Object-Type is to be assigned by IANA (recommended value=1) Oki, Le Roux, and Farrel [Page 5] PCEP Extensions for Inter-Layer TE February 2008 The format of the SWTICH-LAYER object body is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LSP Enc. Type |Switching Type | Reserved |I| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . | // . // | . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LSP Enc. Type |Switching Type | Reserved |I| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Each row indicates the switching type and encoding type that MUST, or MUST NOT be used for specified layer(s) in the computed path. LSP Encoding Type (8 bits): see [RFC3471] for a description of parameters. Switching Type (8 bits): see [RFC3471] for a description of parameters. I flag (1 bit): the I flag indicates whether or NOT a layer with the specified switching type and encoding type MUST be used by the computed path. When the I flag is set (one), the computed path MUST traverse a layer with the specified switching type and encoding type. When the I flag is clear (zero), the computed path MUST NOT enter or traverse any layer with the specified switching type and encoding type. A PCC may want to specify only a Switching Type and not an LSP Encoding Type. In this case, the LSP Encoding Type is set to zero. 3.2.1. REQ-ADAP-CAP Object The REQ-ADAP-CAP object is optional and is used to specify a requested adaptation capability for both ends of the lower layer LSP. The REQ-ADAP-CAP object is used in inter-PCE communication, where the PCE that is responsible for computing higher layer paths acts as a PCC to request a path computation from a PCE that is responsible for computing lower layer paths. The REQ-ADAP-CAP object can be carried within a PCReq message and a PCRep message. It is used in a PCRep message in case of unsuccessful path computation (in this case, the PCRep message also contains a NO-PATH object and the REQ-ADAP-CAP object is used to indicate the set of constraints that could not be satisfied). Oki, Le Roux, and Farrel [Page 6] PCEP Extensions for Inter-Layer TE February 2008 The REQ-ADAP-CAP object MAY be used in a mono-layer network to specify a requested adaptation capability for both ends of the LSP. In this case, it MAY be carried without INTER-LAYER Object. REQ-ADAP-CAP Object-Class is to be assigned by IANA (recommended value=20) REQ-ADAP-CAP Object-Type is to be assigned by IANA (recommended value=1) The format of the REQ-ADAP-CAP object body is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Switching Cap | Encoding | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Switching Capability (8 bits): see [RFC4203] for a description of parameters. Encoding (8 bits): see [RFC3471] for a description of parameters. A PCC may want to specify a Switching Capability, but not an Encoding. In this case, the Encoding MUST be set zero. 4. Procedure 4.1. Path Computation Request A PCC requests inter-layer path computation in a PCReq message by including the INTER-LAYER object with the I flag set. The INTER- LAYER object indicates whether inter-layer path computation is allowed and whether nested signaling is allowed. The SWITCH-LAYER object, which MUST NOT be present unless the INTER-LAYER object is also present, is optionally used to specify the switching types and encoding types that define layers that MUST, or MUST NOT, be used in the computed path. The REQ-ADAP-CAP object is optionally used to specify the interface switching capability of both ends of the lower layer LSP. The REQ- ADAP-CAP object is used in inter-PCE communication, where the PCE that is responsible for computing higher layer paths makes a request as a PCC to a PCE that is responsible for computing lower layer paths. Oki, Le Roux, and Farrel [Page 7] PCEP Extensions for Inter-Layer TE February 2008 4.2. Path Computation Reply The requested PCE replies to the requesting PCC for the inter-layer path computation result in a PCRep message including the INTER- LAYER object. In the case of unsuccessful path computation, the PCRep message also contains a NO-PATH object, and the SWITCH-TYPE object and/or the REQ-ADAP-CAP MAY be used to indicate the set of constraints that could not be satisfied. 5. Updated Format of PCEP Messages The format of the PCReq message is updated as follows: ::= [] where: ::= [] ::=[] ::= [] [] [] [] [] [] [] [] [] [] where: ::=[] Oki, Le Roux, and Farrel [Page 8] PCEP Extensions for Inter-Layer TE February 2008 The format of the PCRep message is updated as follows: ::= where: ::=[] ::= [] [] ::=[] ::= [] [] [] [] [] [] [] [] where: ::=[] 6. Manageability considerations TBD Manageability of inter-layer traffic engineering with PCE must address the following consideration for section 5.1. - need for a MIB module for control and monitoring - need for built-in diagnostic tools - configuration implication for the protocol 7. IANA considerations TBD Oki, Le Roux, and Farrel [Page 9] PCEP Extensions for Inter-Layer TE February 2008 8. Security Considerations TBD Inter-layer traffic engineering with PCE may raise new security issues when PCE-PCE communication is done between different layer networks for inter-layer path computation. Security issues may also exist when a single PCE is granted full visibility of TE information that applies to multiple layers. It is expected that solutions for inter-layer protocol extensions will address these issues in detail using security techniques such as authentication. 9. Acknowledgments 10. References 10.1. Normative Reference [RFC2119] S. Bradner, "Key words for use in RFCs to indicate requirements levels", RFC 2119, March 1997. [RFC3471] L. Burger, "Generalized Multi-Protocol Label Switching (GMPLS)" RFC 3471, January 2003. [RFC3945] E. Mannie, "Generalized Multi-Protocol Label Switching Architecture", RFC 3945, October 2004. [RFC4203] K. Kompella and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC4206] K. Kompella, and Y. Rekhter, "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. [PCEP] JP. Vasseur et al, "Path Computation Element (PCE) Communication Protocol (PCEP)" draft-ietf-pce-pcep, work in progress. [PCE-INTER-LAYER-REQ] E. Oki et al., "PCC-PCE Communication Requirements for Inter-Layer Traffic Engineering", draft- ietf-pce-inter-layer-req, work in progress. [PCE-INTER-LAYER-FRWK] E. Oki et al., "Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic Engineering", draft- ietf-pce-inter-layer-frwk, work in progress. Oki, Le Roux, and Farrel [Page 10] PCEP Extensions for Inter-Layer TE February 2008 10.2. Informative Reference [RFC4655] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, September 2006. [MLN-REQ] K. Shiomoto et al., "Requirements for GMPLS-based multi- region and multi-layer networks (MRN/MLN)", draft-ietf- ccamp-gmpls-mln-reqs, work in progress. [LSP-STITCH] A. Ayyangar et al., "Label Switched Path Stitching with Generalized Multiprotocol Label Switching Traffic Engineering (GMPLS TE)", draft-ietf-ccamp-lsp-stitching, work in progress. 11. Authors' Addresses Eiji Oki NTT 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: oki.eiji@lab.ntt.co.jp Jean-Louis Le Roux France Telecom R&D, Av Pierre Marzin, 22300 Lannion, France Email: jeanlouis.leroux@orange-ftgroup.com Adrian Farrel Old Dog Consulting Email: adrian@olddog.co.uk 12. Intellectual Property Statement 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 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. Oki, Le Roux, and Farrel [Page 11] PCEP Extensions for Inter-Layer TE February 2008 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. Disclaimer of Validity 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. Copyright Statement Copyright (C) The IETF Trust (2008). 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. Oki, Le Roux, and Farrel [Page 12]