On the Feasibility and Efficacy of Protection Routing in IP Networks

Abstract

With network components increasingly reliable, routing is playing an ever greater role in determining network reliability. This has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. Centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. However, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. This paper leverages the flexibility afforded by centralized routing to address these challenges. Specifically, we explore when and how standby backup forwarding options can be activated, while waiting for an update from the centralized server after the failure of an individual component (link or node). We provide analytical insight into the feasibility of such backups as a function of network structure, and quantify their computational complexity. We also develop an efficient heuristic reconciling protectability and performance, and demonstrate its effectiveness in a broad range of scenarios. The results should facilitate deployments of centralized routing solutions. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/ese_papers/521 On the Feasibility and Efficacy of Protection Routing in IP NetworksKin-Wah Kwong * , Lixin Gao † , Roch Guérin * , and Zhi-Li Zhang ‡ * University of Pennsylvania, † University of Massachusetts, ‡ University of Minnesota kkw@seas.upenn.edu, lgao@ecs.umass.edu, guerin@ee.upenn.edu, zhzhang@cs.umn.edu Abstract-With network components increasingly reliable, routing is playing an ever greater role in determining network reliability. This has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. Centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. However, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. This paper leverages the flexibility afforded by centralized routing to address these challenges. Specifically, we explore when and how standby backup forwarding options can be activated, while waiting for an update from the c...

Optimization methods for improving IP-level fast protection for local shared risk groups with Loop-Free Alternates

“…Protection routing [25] is different from the others in the sense that routers are only responsible for packet forwarding but routing information is stored in a central server. The server calculates a set of different routing trees, not necessarily coincident with shortest paths, accompanied with a carefully chosen set of secondary next-hops for each node that can be used when the primary next-hop disappears.…”

High Availability in the Future Internet

“…On the other hand, there are methods, which use explicit tunneling to avoid the failed components [7,17,36,6]. Proposals in [43,37] have topological requirements, whilst the mechanism proposed in [29] uses a central server to pre-compute forwarding decisions for common failure scenarios and download them into the routers. Accordingly, at the moment none of these proposals is available in IP routers, since they need modifications to the existing protocols, making LFA the only deployable option for ISPs.…”

Optimizing IGP link costs for improving IP-level resilience

“…Such analysis is crucial, as it helps uncover the graph theoretical ingredients needed for good LFA coverage. Possibly the closest to ours is the study in [12], where the authors perform a qualitative protectability analysis for a fast resilience scheme they call IP protection routing. Protection routing is appealing for such an analysis as it is theoretically much easier to approach than LFA, however, in practice it is somewhat less attractive as implementing it requires centralized control over the routing tables.…”

“…In the first part, we give new graph theoretical tools for analyzing LFA failure case coverage in operational networks. Similar protectability analyses are already available for some non-standardized IPFRR mechanisms: [11] considers the O2 method and [12] discusses a centralized destinationbased routing scheme. For LFA, only simulation-based reports have been available this far [13]- [16], but a mathematical apparatus for LFA coverage analysis is still missing.…”

“…Although many operators have important operational preferences to reflect in the link costs [18], [19], we still believe that an in-depth analysis of the extent of fast resilience achievable with LFA can prove valuable to anyone considering IPFRR deployment. And while improving IP resilience is a recurring theme in the literature (see [20] for deflection routing, [11] for O2, or [12] for a review), for the specific case of LFA only the joint optimization task of network performance and resilience has been investigated previously [21], [22]. Thus, at the moment very little understanding is available as to how much LFA-based IP Fast ReRoute is suitable to protect an IP network and to what extent this can be improved by optimizing link costs.…”