Network Working Group Pierre Francois Internet-Draft IMDEA Networks Intended status: Standards Track Clarence Filsfils Expires: October 3, 2014 Cisco Systems, Inc. Bruno Decraene Orange Rob Shakir BT April 1, 2014 Use-cases for Resiliency in SPRING draft-francois-spring-resiliency-use-case-01 Abstract This document describes the use cases for resiliency in SPRING networks. 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 October 3, 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 Pierre Francois, et al. Expires October 3, 2014 [Page 1] Internet-Draft SPRING Resiliency use-cases April 2014 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Path protection . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Management-free local protection . . . . . . . . . . . . . . . 4 4. Managed local protection . . . . . . . . . . . . . . . . . . . 4 5. Co-existence . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Pierre Francois, et al. Expires October 3, 2014 [Page 2] Internet-Draft SPRING Resiliency use-cases April 2014 1. Introduction SPRING aims at providing a network architecture supporting services with tight SLA guarantees [1]. This document reviews various use cases for Fast Reroute (FRR) of services in a SPRING network. Note that these use cases are in particular applicable to existing LDP based and pure IP networks. A FRR technique involves the pre-computation and dataplane pre- installation of backup paths so as to repair traffic in 50msec upon failure detection. The term "protection" is often used as a synonym for FRR. Such techniques suppose the existence of a sub-10msec failure detection mechanism. Three key alternatives are described: path protection, local protection without operator management and local protection with operator management. The purpose of this document is to illustrate the different techniques and explain how an operator could combine them in the same network. Solutions are not defined in this document. PE1 / \ / \ B------C------D------E /| | \ / | \ / |\ / | | \/ | \/ | \ A | | /\ | /\ | Z \ | | / \ | / \ | / \| |/ \|/ \|/ F------G------H------I Figure 1: Reference topology We use Figure 1 as a reference topology throughout the document. We describe the various use-cases in the next sections. All link metrics are equal to 1, with the exception of the links of PE1 which are configured with a metric of 100. 2. Path protection A first protection strategy consists in excluding any local repair but instead use end-to-end path protection. For example, a Pseudo Wire (PW) from A to Z can be "path protected" in the direction A to Z in the following manner: the operator Pierre Francois, et al. Expires October 3, 2014 [Page 3] Internet-Draft SPRING Resiliency use-cases April 2014 configures two SPRING paths T1 and T2 from A to Z. The two paths are installed in the forwarding plane of A and hence are ready to forward packets. The two paths are made disjoint using the SPRING architecture. T1 is established over path {AB, BC, CD, DE, EZ} and T2 over path {AF, FG, GH, HI, IZ}. When T1 is up, the packets of the PW are sent on T1. When T1 fails, the packets of the PW are sent on T2. When T1 comes back up, the operator either allows for an automated reversion of the traffic onto T1 or selects an operator-driven reversion. The solution to detect the end-to-end liveness of the path is out of the scope of this document. From a SPRING viewpoint, we would like to highlight the following requirement: the two configured paths T1 and T2 MUST NOT benefit from local protection. 3. Management-free local protection An alternative protection strategy consists in management-free local protection. For example, a PW from C to E, transported over the shortest path to E provided by the SPRING architecture, benefits from management-free local protection by having each node along the path (e.g. C and D) automatically pre-compute and pre-install a backup path for the destination E. Upon local detection of the failure, the traffic is repaired over the backup path in sub-50msec. The backup path computation should support the following requirements: o 100% link, node, and SRLG protection in any topology o Automated computation by the IGP o Selection of the backup path such as to minimize the chance for transient congestion and/or delay during the protection period, as reflected by the IGP metric configuration in the network. 4. Managed local protection There may be cases where a management free repair does not fit the policy of the operator. For example, the operator may want the backup path to end at the next-hop (or next-next-hop for node failure) hence excluding IPFRR/LFA types of backup path. Also, the operator might want to tightly control the backup path to the next- hop: for the destination Z upon the failure of link CD, the backup Pierre Francois, et al. Expires October 3, 2014 [Page 4] Internet-Draft SPRING Resiliency use-cases April 2014 path CGHD might be desired while the backup paths CGD and CHD are refused. The protection mechanism must support the explicit configuration of the backup path either under the form of high-level constraints (end at the next-hop, end at the next-next-hop, minimize this metric, avoid this SRLG...) or under the form of an explicit path. 5. Co-existence The operator may want to support several very-different services on the same packet-switching infrastructure. As a result, the SPRING architecture SHOULD allow for the co-existence of the different use cases listed in this document, in the same network. Let us illustrate this with the following example. o Flow F1 is supported over path {C, C-D, E} o Flow F2 is supported over path {C, C-D, I) o Flow F3 is supported over path {C, C-D, Z) o It should be possible for the operator to configure the network to achieve path protection for F1, management free local protection for F2, and managed protection over path {C-H, H-D, Z} for F3. 6. References [1] 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 Architecture", draft-filsfils-rtgwg-segment-routing-01 (work in progress), October 2013. Authors' Addresses Pierre Francois IMDEA Networks Leganes ES Email: pierre.francois@imdea.org Pierre Francois, et al. Expires October 3, 2014 [Page 5] Internet-Draft SPRING Resiliency use-cases April 2014 Clarence Filsfils Cisco Systems, Inc. Brussels BE Email: cfilsfil@cisco.com Bruno Decraene Orange Issy-les-Moulineaux FR Email: bruno.decraene@orange.com Rob Shakir BT London UK Email: rob.shakir@bt.com Pierre Francois, et al. Expires October 3, 2014 [Page 6]