On the Feasibility of Perfect Resilience with Local Fast Failover

Klaus Tycho Foerster, Juho Hirvonen, Yvonne-Anne Pignolet, Stefan Schmid, Gilles Tredan

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


In order to provide a high resilience and to react quickly to link failures, modern computer networks support fully decentralized flow rerouting, also known as local fast failover. In a nutshell, the task of a local fast failover algorithm is to pre-define fast failover rules for each node using locally available information only. These rules determine for each incoming link from which a packet may arrive and the set of local link failures (i.e., the failed links incident to a node), on which outgoing link a packet should be forwarded. Ideally, such a local fast failover algorithm provides a perfect resilience deterministically: a packet emitted from any source can reach any target, as long as the underlying network remains connected. Feigenbaum et al. (ACM PODC 2012) and also Chiesa et al. (IEEE/ACM Trans. Netw. 2017) showed that it is not always possible to provide perfect resilience. Interestingly, not much more is known currently about the feasibility of perfect resilience.

This paper revisits perfect resilience with local fast failover, both in a model where the source can and cannot be used for forwarding decisions. We first derive several fairly general impossibility results: By establishing a connection between graph minors and resilience, we prove that it is impossible to achieve perfect resilience on any non-planar graph; furthermore, while planarity is necessary, it is also not sufficient for perfect resilience. In some scenarios, a local failover algorithm cannot even guarantee that a packet reaches its target, even if the source is still highly connected to the target after the failures.

On the positive side, we show that graph families closed under link subdivision allow for simple and efficient failover algorithms which simply skip failed links. We demonstrate this technique by deriving perfect resilience for outerplanar graphs and related scenarios, as well as for scenarios where the source and target are topologically close after failures.
Original languageEnglish
Title of host publicationProceedings of SIAM-ACM Symposium on Algorithmic Principles of Computer Systems, APOCS 2021)
Number of pages15
ISBN (Electronic)978-1-61197-648-9
Publication statusPublished - 2021
MoE publication typeA4 Article in a conference publication
EventSymposium on Algorithmic Principles of Computer Systems - Virtual, Online
Duration: 13 Jan 202113 Jan 2021


ConferenceSymposium on Algorithmic Principles of Computer Systems
Abbreviated titleAPOCS
CityVirtual, Online
Internet address


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