Network Working Group S. Previdi, Ed. Internet-Draft C. Filsfils, Ed. Intended status: Standards Track Cisco Systems, Inc. Expires: August 17, 2014 B. Decraene S. Litkowski Orange M. Horneffer R. Geib Deutsche Telekom February 13, 2014 SPRING Problem Statement and Requirements draft-previdi-spring-problem-statement-00 Abstract The ability for a node to specify a forwarding path, other than the normal shortest path, that a particular packet will traverse, benefits a number of network functions. Source-based routing mechanisms have previously been specified for network protocols, but have not seen widespread adoption. In this context, the term 'source' means 'the point at which the explicit route is imposed'. This document outlines various use cases, with their requirements, that need to be taken into account by the Source Packet Routing in Networking (SPRING) architecture. 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 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." Previdi, et al. Expires August 17, 2014 [Page 1] Internet-Draft SPRING Problem Statement February 2014 This Internet-Draft will expire on August 17, 2014. Copyright Notice Copyright (c) 2014 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. Previdi, et al. Expires August 17, 2014 [Page 2] Internet-Draft SPRING Problem Statement February 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Dataplanes . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. IGP-based MPLS Tunneling . . . . . . . . . . . . . . . . . . . 4 4. Fast Reroute . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Traffic Engineering . . . . . . . . . . . . . . . . . . . . . . 5 6. Interoperability with non-SPRING nodes . . . . . . . . . . . . 6 7. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 10. Manageability Considerations . . . . . . . . . . . . . . . . . 7 11. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 13.1. Normative References . . . . . . . . . . . . . . . . . . . 8 13.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Previdi, et al. Expires August 17, 2014 [Page 3] Internet-Draft SPRING Problem Statement February 2014 1. Introduction The ability for a node to specify a forwarding path, other than the normal shortest path, that a particular packet will traverse, benefits a number of network functions, for example: Some types of network virtualization, including multi-topology networks and the partitioning of network resources for VPNs Network, link, path and node protection such as fast re-route Network programmability OAM techniques Simplification and reduction of network signaling components Load balancing and traffic engineering The term 'source' means 'the point at which the explicit route is imposed'. In this context, Source Packet Routing in Networking (SPRING) architecture is being defined so as to address the use cases and requirements described in this document. 2. Dataplanes The SPRING architecture should be general in order to ease its applicability to different dataplanes. MPLS dataplane doesn't require any modification in order to apply a source-based routed model (e.g.: [I-D.filsfils-spring-segment-routing-mpls]). IPv6 specification [RFC2460] defines the Routing Extension Header which provides IPv6 source-based routing capabilities. The SPRING architecture should leverage existing MPLS dataplane without any modification and leverage IPv6 dataplane with minor modifications. 3. IGP-based MPLS Tunneling The source-based routing model, applied to the MPLS dataplane, offers the ability to tunnel services (VPN, VPLS, VPWS) from an ingress PE Previdi, et al. Expires August 17, 2014 [Page 4] Internet-Draft SPRING Problem Statement February 2014 to an egress PE, without any other protocol than IGPs (ISIS or OSPF). LDP and RSVP-TE signaling protocols are not required. The SPRING architecture should allow PE to PE forwarding according to the IGP shortest path without the addition of any other signaling protocol. The packet each PE forwards across the network will contain (within their label stack) the necessary information derived from the topology database in order to deliver the packet to the remote PE. 4. Fast Reroute FRR technologies have been deployed by network operators in order to cope with link or node failures through pre-computation of backup paths. The SPRING architecture should address following requirements: o support of FRR on any topology o pre-computation and setup of backup path without any additional signaling (other than the regular IGP/BGP protocols) o support of shared risk constraints o support of node and link protection o support of microloop avoidance Further illustrations of the problem statement for FRR are to be found in [I-D.francois-sr-resiliency-use-case]. 5. Traffic Engineering Traffic Engineering has been widely addressed using IGP protocol extensions (for resources information propagation) and RSVP-TE for signaling explicit paths. Different contexts and modes have been defined (single vs. multiple domains, with or without bandwidth admission control, centralized vs. distributed path computation, etc). In all cases, one of the major components of the TE architecture is the signaling protocol (RSVP-TE) which is used in order to signal and establish the explicit path. Each path, once computed, need to be signaled and state for each path must be present in each node traversed by the path. This incurs a scalability problem especially Previdi, et al. Expires August 17, 2014 [Page 5] Internet-Draft SPRING Problem Statement February 2014 in the context of SDN where traffic differentiation may be done at a finer granularity (e.g.: application specific). Also the amount of state needed to be carried in all involved nodes contributes significantly to complexity and the number of failures cases, and thus increases operational effort while decreasing overall network reliability. The source-based routing model allows traffic engineering to be implemented without the need of a signaling component. The SPRING architecture should support traffic engineering, including: o loose or strict options o bandwidth admission control o distributed vs. centralized model (PCE, SDN Controller) o disjointness in dual-plane networks o egress peering traffic engineering o load-balancing among non-parallel links o Limiting (scalable, preferably zero) per-service state and signaling on midpoint and tail-end routers. o ECMP-awareness o node resiliency property (i.e.: the traffic-engineering policy is not anchored to a specific core node whose failure could impact the service. 6. Interoperability with non-SPRING nodes SPRING must inter-operate with non-SPRING nodes. An illustration of interoperability between SPRING and other MPLS Signalling Protocols (LDP) is described here in [I-D.filsfils-spring-segment-routing-ldp-interop]. Interoperability with IPv6 non-SPRING nodes will be described in a future document. Previdi, et al. Expires August 17, 2014 [Page 6] Internet-Draft SPRING Problem Statement February 2014 7. OAM The SPRING WG should provide OAM and the management needed to manage SPRING enabled networks. The SPRING procedures may also be used as a tool for OAM in SPRING enabled networks. OAM problem statement and requirements will be described in a separate document.. Interoperability with IPv6 non-SPRING nodes will be described in a future document. 8. Security There is an assumed trust model such that any node imposing an explicit route on a packet is assumed to be allowed to do so. In such context trust boundaries should strip explicit routes from a packet. For each data plane technology that SPRING specifies, a security analysis must be provided showing how protection is provided against an attacker disrupting the network by for example, maliciously injecting SPRING packets. 9. IANA Considerations TBD 10. Manageability Considerations TBD 11. Security Considerations TBD 12. Acknowledgements TBD 13. References Previdi, et al. Expires August 17, 2014 [Page 7] Internet-Draft SPRING Problem Statement February 2014 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. 13.2. Informative References [I-D.filsfils-spring-segment-routing-ldp-interop] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, "Segment Routing interoperability with LDP", draft-filsfils-spring-segment-routing-ldp-interop-00 (work in progress), October 2013. [I-D.filsfils-spring-segment-routing-mpls] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, "Segment Routing with MPLS data plane", draft-filsfils-spring-segment-routing-mpls-00 (work in progress), October 2013. [I-D.francois-sr-resiliency-use-case] Francois, P., Filsfils, C., Decraene, B., and R. Shakir, "Use-cases for Resiliency in Segment Routing", draft-francois-sr-resiliency-use-case-00 (work in progress), January 2014. Authors' Addresses Stefano Previdi (editor) Cisco Systems, Inc. Via Del Serafico, 200 Rome 00142 Italy Email: sprevidi@cisco.com Previdi, et al. Expires August 17, 2014 [Page 8] Internet-Draft SPRING Problem Statement February 2014 Clarence Filsfils (editor) Cisco Systems, Inc. Brussels, BE Email: cfilsfil@cisco.com Bruno Decraene Orange FR Email: bruno.decraene@orange.com Stephane Litkowski Orange FR Email: stephane.litkowski@orange.com Martin Horneffer Deutsche Telekom Hammer Str. 216-226 Muenster 48153 DE Email: Martin.Horneffer@telekom.de Ruediger Geib Deutsche Telekom Heinrich Hertz Str. 3-7 Darmstadt 64295 DE Email: Ruediger.Geib@telekom.de Previdi, et al. Expires August 17, 2014 [Page 9]