Network Working Group Eiji Oki (Editor) Internet Draft NTT Category: Informational Expires: August 2006 February 2006 PCC-PCE Communication Requirements for Inter-Layer Traffic Engineering draft-ietf-pce-inter-layer-req-01.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 functions of path computation 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. PCE is a candidate solution for such requirements. Generic requirements for a communication protocol between Path Computation Clients (PCCs) and PCEs are presented in "PCE Communication Protocol Generic Requirements". This document complements the generic requirements and presents a detailed set of PCC-PCE communication protocol requirements for inter-layer traffic engineering. Oki et al. Expires August 2006 [Page 1] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 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]. Table of Contents 1. Contributors..................................................2 2. Terminology...................................................2 3. Introduction..................................................3 4. Motivation for PCE-Based Inter-Layer Path Computation.........4 5. PCC-PCE Communication Requirements for Inter-Layer Traffic Engineering.......................................................4 5.1. PCC-PCE Communication......................................4 5.1.1. Control of Inter-Layer Path Computation..................5 5.1.2. Control of The Type of Path to be Computed...............5 5.1.3. Communication of Inter-Layer Constraints.................5 5.1.4. Cooperation Between PCEs.................................6 5.1.5. Inter-Layer Diverse paths................................6 5.2. Supportive Network Models..................................6 6. Manageability considerations..................................6 7. Security Considerations.......................................6 8. Acknowledgments...............................................6 9. References....................................................7 9.1. Normative Reference........................................7 9.2. Informative Reference......................................7 10. AuthorsEAddresses..........................................7 11. Intellectual Property Statement.............................8 1. Contributors The following are the authors that contributed to the present document: Eiji Oki (NTT) Jean-Louis Le Roux (France Telecom) Kenji Kumaki (KDDI) Adrian Farrel (Old Dog Consulting) 2. Terminology LSP: Label Switched Path. LSR: Label Switching Router. PCC: Path Computation Client: any client application requesting a path computation to be performed by a Path Computation Element. Oki et al. Expires Auguest 2006 [Page 2] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 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. PCECP: PCE Communication Protocol, a protocol for communication between PCCs and PCEs. TED: Traffic Engineering Database which contains the topology and resource information of the domain. The TED may be fed by IGP extensions or potentially by other means. TE LSP: Traffic Engineering Label Switched Path. TE LSP head-end: head/source/ingress of the TE LSP. TE LSP tail-end: tail/destination/egress of the TE LSP. 3. Introduction The Path Computation Element (PCE) defined in [PCE-ARCH] is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. A network may comprise of 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, LSP 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) [MRN-REQ]. 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 achieving better network efficiency. This is what we call Inter- layer traffic engineering. This includes mechanisms allowing to compute end-to-end paths across layers, as 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 [MRN-REQ]. Inter-layer traffic engineering is included in the scope of the PCE architecture [PCE-ARCH], and PCE can provide a suitable mechanism for resolving inter-layer path computation issues. The applicability of the PCE-based path computation architecture to inter-layer traffic engineering is described in [PCE-INTER-LAYER- APP]. This document presents a set of PCC-PCE communication protocol (PCECP) requirements for inter-layer traffic engineering. It supplements the generic requirements documented in [PCE-COM-REQ]. Oki et al. Expires Auguest 2006 [Page 3] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 4. Motivation for PCE-Based Inter-Layer Path Computation [RFC4206] defines a way to signal a higher-layer LSP, whose explicit route includes hops traversed by LSPs in lower layers. The computation of end-to-end paths across layers is called Inter-Layer Path Computation. An LSR in the higher-layer might not have information on the lower- layer topology, particularly in an overlay or augmented model, and hence might not be able to compute an end-to-end path across layers. PCE-based inter-layer path computation, consists of relying on one or more PCEs to compute an end-to-end path across layers. This could rely on a single PCE path computation where the PCE 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 as a multiple PCE computation where each member of a set of PCEs has information about the topology of one or more layers, but not all layers, and collaborate to compute an end-to- end path. Consider a two-layer network where the higher-layer network is a packet-based IP/MPLS or GMPLS network and the lower-layer network is a GMPLS optical network. An ingress LSR in the higher-layer network tries to set up an LSP to an egress LSR also in the higher- layer network across the lower-layer network, and needs a path in the higher-layer network. However, suppose that there is no TE link between border LSRs, which are located on the boundary between the higher-layer and lower-layer networks, and that the ingress LSR does not have topology visibility in the lower layer. If a single- layer path computation is applied for the higher-layer, the path computation fails. On the other hand, inter-layer path computation is able to provide a route in the higher-layer and a suggestion that a lower-layer LSP be setup between border LSRs, considering both layers' TE topologies. Further discussion of the application of PCE to inter-layer path computation can be found in [PCE-INTER-LAYER-APP]. 5. PCC-PCE Communication Requirements for Inter-Layer Traffic Engineering This section sets out additional requirements not covered in [PCE- COM-REQ] specific to the problems of multi-layer TE. 5.1. PCC-PCE Communication The PCC-PCE communication protocol MUST allow requests and replies for inter-layer path computation. Oki et al. Expires Auguest 2006 [Page 4] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 This requires no additional messages, but implies the following additional constraints to be added to the PCC-PCE communication protocol. 5.1.1. Control of Inter-Layer Path Computation A request from a PCC to a PCE SHOULD indicate whether inter-layer path computation is allowed. In the absence of such an indication, the default is that inter-layer path computation is not allowed. Therefore, a request from a PCC to a PCE MUST support the inclusion of such an indication. 5.1.2. Control of The Type of Path to be Computed The PCE computes and returns a path to the PCC that the PCC can use to build a higher-layer or lower-layer LSP once converted to an Explicit Route Object (ERO) for use in RSVP-TE signaling. There are two options [PCE-INTER-LAYER-APP]. - Option 1: Mono-layer path. The PCE computes a "mono layer" path, i.e. a path that includes only TE-links from the same layer. - Option 2: Multi-layer path. The PCE computes a "multi-layer" path, i.e. a path that includes TE links from distinct layers [RFC4206]. A request from a PCC to a PCE MUST allow control of the type of the path to be computed by selection from the following list: - A mono-layer path that includes already established lower-layer LSPs - a mono-layer path that includes loose hop(s) - a multi-layer path that can include the complete path of one or more lower-layer LSPs not yet established. When multi-layer path computation is requested, a response from a PCE to a PCC MUST support the inclusion, as part of end-to-end path, of the path of the lower-layer LSPs to be established. If a response message from a PCE to PCC carries a mono-layer path that includes loose hop(s), or a multi-layer path that can include the complete path of one or more lower-layer LSPs not yet established, the signaling of the higher-layer LSP may trigger the establishment of the lower-layer LSPs (nested signaling). The nested signaling may increase the higher-layer connection setup latency. An ingress LSR for the higher-layer LSP, or a PCC, needs to know whether nested signaling is required or not. A request from a PCC to a PCE MUST allow indicating whether nested signaling is acceptable or not. A response from a PCE to a PCC MUST allow indicating whether the computed path triggers nested signaling or not. 5.1.3. Communication of Inter-Layer Constraints Oki et al. Expires Auguest 2006 [Page 5] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 A request from a PCC to a PCE MUST support the inclusion of constraints for multiple layers. This includes the switching type(s) and encoding type(s) that can, must, or must not be used in the computed path. 5.1.4. Cooperation Between PCEs When each layer is controlled by a PCE, which only has access to the topology information of its layer, the PCEs of each layer need to cooperate to perform inter-layer path computation. In this case, communication between PCEs is required for inter-layer path computation. A PCE that behaves as a client is defined as a PCC [PCE-ARCH]. The PCC-PCE communication protocol MUST allow requests and replies for multiple PCE inter-layer path computation. 5.1.5. Inter-Layer Diverse paths The PCE communication protocol MUST allow for the computation of diverse inter-Layer paths. A request from a PCC to a PCE MUST support the inclusion of multiple path request, with the desired level of diversity at each layer (link, node, SRLG). 5.2. Supportive Network Models The PCC-PCE communication protocol SHOULD allow several architectural alternatives for interworking between MPLS and GMPLS networks: overlay, integrated and augmented models [RFC3945]. 6. Manageability considerations 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. Security Considerations 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. 8. Acknowledgments Oki et al. Expires Auguest 2006 [Page 6] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 We would like to thank Kohei Shiomoto, Ichiro Inoue, and Dean Cheng for their useful comments. 9. References 9.1. Normative Reference [RFC2119] Bradner, S., "Key words for use in RFCs to indicate requirements levels", RFC 2119, March 1997. [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching Architecture", RFC 3945, October 2004. [RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. 9.2. Informative Reference [PCE-ARCH] A. Farrel, JP. Vasseur and J. Ash, "Path Computation Element (PCE) Architecture", draft-ietf-pce-architecture (work in progress). [PCE-COM-REQ] J. Ash, J.L Le Roux et al., "PCE Communication Protocol Generic Requirements", draft-ietf-pce-comm-protocol-gen- reqs (work in progress). [PCE-DISC-REQ] JL Le Roux et al., "Requirements for Path Computation Element (PCE) Discovery", draft-ietf-pce-discovery-reqs (work in progress). [MRN-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). [PCE-INTER-LAYER-APP] E. Oki et al., "PCE Applicability for Inter- Layer MPLS and GMPLS Traffic Engineering", draft-oki-pce-inter- layer-app (work in progress) 10. 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@francetelecom.com Oki et al. Expires Auguest 2006 [Page 7] Internet Draft draft-ietf-pce-inter-layer-req-00.txt February 2006 Kenji Kumaki KDDI Corporation Garden Air Tower Iidabashi, Chiyoda-ku, Tokyo 102-8460, JAPAN Phone: +81-3-6678-3103 Email: ke-kumaki@kddi.com Adrian Farrel Old Dog Consulting Email: adrian@olddog.co.uk 11. 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. 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 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 Internet Society (2006). 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 et al. Expires Auguest 2006 [Page 8]