Path Computation Element Working Group O. Dugeon Internet-Draft J. Meuric Intended status: Informational Orange Labs Expires: September 10, 2012 R. Douville Alcatel-Lucent R. Casellas CTTC O. Gonzalez de Dios Telefonica Investigacion y Desarrollo March 9, 2012 Path Computation Element (PCE) Traffic Engineering Database (TED) Requirements draft-dugeon-pce-ted-reqs-01 Abstract The Path Computation Element (PCE) working group (WG) has produced a set of RFCs to standardize the behavior of the Path Computation Element as a tool to help MPLS-TE and GMPLS LSP tunnels placement. In the PCE architecture, a main assumption has been done concerning the information that the PCE needs to perform its computation: the Traffic Engineering Database (TED) contains all pertinent and suitable information regarding the network that is in the scope of a PCE. Nevertheless, the TED requirements as well as the TED information have not yet been formalized. In addition, some recent RFC (like the Backward Recursive Path Computation procedure) or WG draft (like draft-ietf-pce-hierarchy ...) suffer from a lack of information in the TED, leading to a non optimal result or to some difficulties to deploy them. This memo tries to identity some TED requirements for the PCE. It is split in two main section: the identification of the specific information to be stored in the TED and how it may be populated. 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 RFC 2119 [RFC2119]. 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 Dugeon, et al. Expires September 10, 2012 [Page 1] Internet-Draft PCE TED Req. March 2012 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 September 10, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. 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. Dugeon, et al. Expires September 10, 2012 [Page 2] Internet-Draft PCE TED Req. March 2012 Table of Contents 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 1.1. PCE Assumption and Hypothesis . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. TED Requirements . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Intra-Domain . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.2. GMPLS . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. Inter-Domain . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Operational Information . . . . . . . . . . . . . . . . . 7 3. TED Population . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Intra-domain . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.2. GMPLS . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2. Inter-Domain . . . . . . . . . . . . . . . . . . . . . . . 8 3.3. Operational information . . . . . . . . . . . . . . . . . 9 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5.1. Intra-domain information . . . . . . . . . . . . . . . . . 9 5.2. Inter-domain information . . . . . . . . . . . . . . . . . 9 5.3. Operational information . . . . . . . . . . . . . . . . . 10 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . . 10 7.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Dugeon, et al. Expires September 10, 2012 [Page 3] Internet-Draft PCE TED Req. March 2012 1. Problem Statement Looking to the different RFCs that describe the PCE architecture and in particular RFC 4655 [RFC4655], RFC 5440 [RFC5440] and RFC 5441 [RFC5441] as well as the draft H-PCE [I-D.ietf-pce-hierarchy-fwk], the Path Computation Element (PCE) needs to acquire a set of information that is usually store in the Traffic Engineering Database (TED) in order to perform its path computation. Even if intra-domain topology acquisition is well documented and known (e.g. by listening to the IGP-TE protocol that runs inside the network), inter-domain topology information, PCE peer address, neighbor AS ... that are necessary for the Backward Recursive Path Computation (BRPC) and the Hierarchical PCE are not documented and not completely standardized. The purpose of this memo is to inventory the required information that should be part of the PCE TED and the different mechanisms that allow an operator to populate it. 1.1. PCE Assumption and Hypothesis In some cases, both the path computation and the TED operations are slightly coupled: border node identification, endpoint localization and topology aggregation for domain sequence selection... to name a few in which an IGP-based TED may not be sufficient. It is also important to differentiate several environments with different requirements, especially for the multi-domain problem. The PCE is scoped for any kind of network, from transport networks (TDM/WDM) with a rather limited number of domains, few interconnections, and few confidentiality issues; transport networks with a large number of domains; MPLS networks with several administrative domains; and big IP/MPLS networks with a large number of domains with peering agreements. For each of them, a different solution for the multi- domain path computation may apply. A solution may not be scalable for one, but perfectly suitable for another. Up to now, PCE WG has based its work and standard on the assumption and hypothesis that the TED contains all pertinent information suitable for the PCE to compute an optimal TE-LSP placement, over one or several domains a PCE has visibility on or over a set of PCE- capable domains (e.g. using BRPC procedure). We could identify two major sources of information for the TED: o The intra-domain routing protocol like OSPF-TE or IS-IS-TE (including extensions for border links), o The inter-domain routing protocol, i.e. BGP for the inter-AS case. Dugeon, et al. Expires September 10, 2012 [Page 4] Internet-Draft PCE TED Req. March 2012 If the first source gives a precise and synchronize view of the controlled network, BGP typically just provides network reachability with only one AS path (unless using recent add path option). Nevertheless, to optimize inter-domain path computation, route diversity and a minimum set of Traffic Engineering information about the foreign domains could be helpful. Another source of information, mainly static information can be the management plane, e.g. using SNMP, CLI... So, it is necessary to classify the source of information by their frequency of update: static or dynamic, e.g. a domain ID is unlikely to change, while unreserved bandwidth of a link may be continuously changing. 1.2. Terminology ABR: Area Border Routers. Routers used to connect two IGP areas (areas in OSPF or levels in IS-IS). ASBR: Autonomous System Border Router. Router used to connect together ASes of the same or different service providers via one or more inter-AS links. AS: Autonomous System Boundary Node (BN): a boundary node is either an ABR in the context of inter-area Traffic Engineering or an ASBR in the context of inter-AS Traffic Engineering. Domain: an Autonomous System Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along a determined sequence of domains. Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along a determined sequence of domains. Inter-area TE LSP: A TE LSP that crosses an IGP area boundary. Inter-AS TE LSP: A TE LSP that crosses an AS boundary. IGP-TE: Interior Gateway Protocol with Traffic Engineering support. Both OSPF-TE and IS-IS-TE are indentified in this category. 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. PCE(i) is a PCE with the scope of domain(i). Dugeon, et al. Expires September 10, 2012 [Page 5] Internet-Draft PCE TED Req. March 2012 TED: Traffic Engineering Database. 2. TED Requirements This section made a first inventory of the main requirements of the PCE TED in term of information that the database should contains. 2.1. Intra-Domain This section describes the Intra-domain information that are suitable for the PCE TED including both MPLS and GMPLS. 2.1.1. MPLS A PCE is allowed to compute paths in one or several domains. Such PCE MUST be aware of the precise details of the network topology (or topologies) in order to compute optimal TE-LSP placements. The information needed in this case includes: o List of Internal Nodes identified by a reachable address: All nodes of the networks that are not border node, o List of Internal Links that rely nodes (both internal and border nodes), o Traffic Engineering information of the different links i.e. RFC 3630 [RFC3630] and RFC 5305 [RFC5305](with e.g. recent metric extensions proposal OSPF Traffic Engineering (TE) Metric Extensions [I-D.ietf-ospf-te-metric-extensions]) o Traffic Engineering information with GMPLS extensions of the different links i.e. RFC 4203 [RFC4203] and RFC 5307 [RFC5307], o Traffic Engineering information of the nodes. The information above mentioned is usually exchanged using the IGP-TE protocol (OSPF-TE or IS-IS-TE). 2.1.2. GMPLS To be provided later 2.2. Inter-Domain A PCE can also be allowed to take part to inter-domain path computation (e.g in per-domain path computation, BRPC or H-PCE relationship). Some inter-domain information is mandatory when Dugeon, et al. Expires September 10, 2012 [Page 6] Internet-Draft PCE TED Req. March 2012 operator intend to use the PCE to compute Inter-AS TE LSP path that cross AS boundary. For that purpose, the TED SHOULD contains all information that allow the PCE to determine the optimal AS path for the TE-LSP computation, which includes: o ASBR of the foreign domain, o Links between border nodes, i.e. links between Border Node (n) to Border node (n+1), inlcuding Traffic Engineering information as describe in and in , o Traffic Engineering performance between Border Nodes (n) to give performance indication on foreign domain n, o PCE (i) peer address associated with the AS number of the foreign domain (i), RFC 5316 [RFC5316] and RFC 5392 [RFC5392] help to provide required TED information in the case of inter-domain. TED can also contain information about virtual links and abstract information. 2.3. Operational Information This part of the TED contains all others information pertinent for the PCE to compute TE LSP path but that are provided through the management system. 3. TED Population This section aims to provide best current practices when mechanisms are well-known and some hints when standard solutions exist to populate the PCE TED, and so give directions to extend them. In particular, we aim at providing input on whether the TED gets the information from the routing protocol and how it gets it, which specific routing protocols are suited, whether it gets it from an NMS, at what frequency the TED is updated... and if it needs extra information. 3.1. Intra-domain 3.1.1. MPLS As the TED mainly contains the intra-domain topology graph, it is RECOMMENDED to link the PCE with the underlying IGP-TE (OSPF-TE or IS-IS-TE routing protocol). By adding the PCE into the IGP-TE routing intra-domain, it is possible to listen to the routing protocol and then acquired the complete topology graph as well as let Dugeon, et al. Expires September 10, 2012 [Page 7] Internet-Draft PCE TED Req. March 2012 the PCE announce itself (see RFC5088 and RFC5089). In addition, the TED will synchronize as fast as the routing protocol converges like any router in the domain. Best current practices are also of interest when a PCE compute path that spawn to several area / region. In that case, the PCE must be aware of the topology details of each area / region and not only the backbone area / region 1 with the summary of stub area / region 2. In addition, management tools may be used to complement the topology graph provided by the routing protocol. 3.1.2. GMPLS To be provided later. 3.2. Inter-Domain First of all, RFC 5316 or RFC 5392 MUST be activated in the IGP-TE (respectively in IS-IS-TE or OSPF-TE) in order to advertise TE information on the inter-domain links. This give the advantage for the PCE to determine what could be feasible, during path computation, on the peering links. In MPLS, AS path and network reachability are obtained from BGP and routing tables. However, it is not straightforward to collect route diversity or TE information (i.e. bandwidth, transit delay, packet loss ratio, jitter ...) on a foreign domain. Right now, we have identified several methods, which have been tested to fill in the TED with this kind of information: o Use of the management plane; o Use of the "north bound distribution of Link-State and TE Information using BGP" [I-D.gredler-idr-ls-distribution] proposal to exchange TE information about the foreign domain; o Use of PCNtf message to convey, inside vendor attribute (but in a non standardized way), TE information of foreign domain between PCE As well as some potential alternative mechanisms that would need more standardization effort: o A hierarchical TE that could help to advertise, at the AS level, TE information on an abstract/aggregate view of the foreign AS topology; Dugeon, et al. Expires September 10, 2012 [Page 8] Internet-Draft PCE TED Req. March 2012 o A PCEP extension to convey such TE information to the foreign PCE. 3.3. Operational information Most of the time operationals information are provided through the management system of the operator, but some could be automatically discovered. In particular, in intra-domain, PCCs and PCEs can discover automatically reachable PCEs (as well as computation domains) through the deployment of RFC 5088 [RFC5088], for OSPF- controlled networks, and RFC 5089 [RFC5089] for IS-IS-controlled networks. However, for the inter-PCE discovery at the inter-AS level, no mechanism has been standardized (unless ASes are owned by the same ISP). 4. IANA Considerations This document makes no request of IANA for the moment. Note to RFC Editor: this section may be removed on publication as an RFC. 5. Security Considerations Acquisition of information for the PCE TED is of course sensible from a security point of view, especially when acquiring information from others AS. This section aims at providing best practices to prevent some security threat when the PCE try to acquire TED information. 5.1. Intra-domain information Same security considerations must be applied to the PCE when it is connected to an IGP-TE protocol as the routing protocol itself. Best practices observed and deployed by operators must also be taken into account when installing some PCEs. Indeed, even when deployed as a standalone server, PCEs must be considered as a typical router from the IGP-TE perspective. As a result, beyond OSPF or IS-IS tehmselves, the usual security rules must be applied, e.g. login/ passwd, authentication/digest... to protect the connectivity. 5.2. Inter-domain information Inter-domain relation and so information exchange are subject to high potential hijack and so need attention from the security point of view. To avoid disclosing or expose confidential information that two operators would exchange to fill in the TEDs of their respective PCEs, the relation SHOULD be protected by standard cryptography Dugeon, et al. Expires September 10, 2012 [Page 9] Internet-Draft PCE TED Req. March 2012 mechanism. E.g. using IPsec tunnel is RECOMMENDED to protect the connectivity between PCEs and the TED exchanges. 5.3. Operational information All operational information like PCE peer addresses are generally added manually to the TED and so do not need any particular protection nor subject to security. But, as this basic information is needed to connected the PCEs to their peers, it could potentially be associated to sensitive parameters like login and password. So, standard Best Practices are RECOMMENDED to avoid basic security exposition. 6. Acknowledgements The authors want to thanks PCE's WG members and in particular Daniel King for their inputs of this subject. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [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. 7.2. Informative References [I-D.gredler-idr-ls-distribution] Gredler, H., Medved, J., Farrel, A., and S. Previdi, "North-Bound Distribution of Link-State and TE Information using BGP", draft-gredler-idr-ls-distribution-00 (work in progress), September 2011. [I-D.ietf-ospf-te-metric-extensions] Dugeon, et al. Expires September 10, 2012 [Page 10] Internet-Draft PCE TED Req. March 2012 Atlas, A., Drake, J., Giacalone, S., Previdi, S., and D. Ward, "OSPF Traffic Engineering (TE) Metric Extensions", draft-ietf-ospf-te-metric-extensions-00 (work in progress), November 2011. [I-D.ietf-pce-hierarchy-fwk] Farrel, A. and D. King, "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", draft-ietf-pce-hierarchy-fwk-00 (work in progress), October 2011. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008. [RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5307] Kompella, K. and Y. Rekhter, "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008. [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, December 2008. [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5392, January 2009. Dugeon, et al. Expires September 10, 2012 [Page 11] Internet-Draft PCE TED Req. March 2012 Authors' Addresses Olivier Dugeon Orange Labs 2, Avenue Pierre Marzin Lannion 22307 France Email: olivier.dugeon@orange.com Julien Meuric Orange Labs 2, Avenue Pierre Marzin Lannion 22307 France Email: julien.meuric@orange.com Richard Douville Alcatel-Lucent Route de Villejust Nozay, 91620 France Email: richard.douville@alcatel-lucent.com Ramon Casellas CTTC Av. Carl Friedrich FGauss n7 Castelldefels, Barcelona 08860 Spain Email: ramon.casellas@cttc.es Oscar Gonzalez de Dios Telefonica Investigacion y Desarrollo C/ Emilio Vargas 6 Madrid Spain Email: ogondio@tid.es Dugeon, et al. Expires September 10, 2012 [Page 12]