Competitive FIB Aggregation for Independent Prefixes: Online Ski Rental on the Trie

Wuttke

2014 IEEE Global Communications Conference

et al. 2014

Self Cite

Abstract-Snapshots of the Forwarding Information Base (FIB) in Internet routers can be compressed (or aggregated) to at least half of their original size, as shown by previous studies. However, the permanent stream of updates to the FIB due to routing updates complicates FIB aggregation in practice: keeping a (near-)optimally aggregated FIB in face of these routing updates is algorithmically challenging. A sensible trade-off has to be found between the aggregation gain and the complexity of handling routing updates. This paper investigates whether the spatial and temporal locality properties of routing updates conceal opportunities for improving this trade-off in online FIB aggregation.Our contributions include an empirical study of the locality of updates in public Internet routing data. To facilitate this study, we design the Locality-aware FIB Aggregation (LFA) algorithm. We show, that an algorithm as simple as LFA can effectively leverage the locality of FIB churn to keep low the number of updates to the aggregated FIB, as within time periods of a few seconds or minutes, routing updates affect only a limited number of regions in the FIB. I. INTRODUCTIONAt a high level, Internet routers are built around a route processor which runs routing protocols and makes routing decisions, and a forwarding plane which forwards packets according to the decisions of the route processor. The crucial link between the two components is the Forwarding Information Base (FIB), containing the forwarding rules. The route processor inserts and deletes FIB entries according to its route computations. The forwarding plane uses the FIB to perform an IP destination lookup on each incoming packet. This requires the FIB to support very fast IP destination lookups so that packets can be forwarded at line-rate. In addition, the FIB needs to support frequent updates to the forwarding rules due to the churn in the BGP routing table. Finally, the number of forwarding rules that a FIB needs to keep is growing over time, putting extra pressure on the FIB memory capacity. 1 To fulfill all these requirements, FIB memory used in today's enterprise-grade to high-end routers is a highly specialized component, expensive, and power-hungry. It is also considered a main limiting factor in terms of a router's lifetime [12].A natural and local solution to mitigate the problembefore possible long-term solutions are deployed -is the aggregation (or compression) of the FIB, i.e., the replacement of the existing set of rules by an equivalent but smaller set. The aggregation of FIB rules has the appealing property that it is a purely local solution, in the sense that it does not affect neighboring routers and it can be realized by the route processor through only software modifications.

Section: Terminology Related Worksupporting

confidence: 70%

Leveraging locality for FIB aggregation

Wuttke

2014 IEEE Global Communications Conference

et al. 2014

Self Cite

“…They also do not consider to exploit the (temporal and spatial) locality of churn for their benefit. The paper closest to ours is [2]. The authors study online algorithms for FIB compression under the assumption of independent prefixes (both in U-FIB and in FIB).…”

Section: B Related Workmentioning

confidence: 99%

Competitive FIB Aggregation without Update Churn

Bieńkowski

2014 IEEE 34th International Conference on Distributed Computing Systems

et al. 2014

Self Cite

Abstract-This paper attends to the well-known problem of compressing the Forwarding Information Base of a router or switch, while preserving a correct forwarding. In contrast to related work, we study an online variant of the problem where BGP routes can change over time, and where the number of updates to the FIB are taken into account explicitly. Minimizing the number of FIB updates is important, especially when they are sent across the network (e.g., from the network-attached SDN controller).This paper pursues a competitive analysis approach and introduces a formal model which is an interesting generalization of several classic online aggregation problems. The main contribution is a O(w)-competitive algorithm, where w is the length of an IP address. We also derive a lower bound which shows that our result is asymptotically optimal within a natural class of algorithms.

“…In this light, the paper closest to ours is [4], which studies online algorithms for FIB compression under the assumption of independent prefixes (both in U-FIB and in FIB). Without prefix dependencies, the nature of the problem is more related to online ski rental and technically different: achieving a constant competitive ratio is simple, but what the optimal constant is remains an open question.…”

Section: B Related Workmentioning

confidence: 99%

“…We omit the delete procedure as it is similar to the insert one, except for Lines 2 and 10 where TrieInsert() should be replaced with TrieDelete(). After S2 remains unchanged for β seconds, S2 is aggregated again in Step (4).…”

Section: A Spatial and Temporal Locality Of Fib Aggregationmentioning

confidence: 99%

Online Aggregation of the Forwarding Information Base: Accounting for Locality and Churn

Bieńkowski

IEEE/ACM Trans. Networking

et al. 2018

Self Cite

This paper studies the problem of compressing the Forwarding Information Base (FIB), but taking a wider perspective. Indeed, FIB compression goes beyond sheer compression, as the gain in memory use obtained from the compression has consequences on the updates that will have to be applied to the compressed FIB. We are interested in the situation where forwarding rules can change over time, e.g., due to BGP route updates. Accordingly, we frame FIB compression as an online problem, and design competitive online algorithms to solve it. In contrast to prior work which mostly focused on static optimizations, we study an online variant of the problem where routes can change over time, and where the number of updates to the FIB are taken into account explicitly. The reason to consider this version of the problem is that leveraging temporal locality while accounting for the number of FIB updates helps to keep routers CPU load low and reduces the number of FIB updates to be transferred, e.g., from the network-attached Software-Defined Network (SDN) controller to a remote switch. This paper introduces a formal model which is an interesting generalization of several classic online aggregation problems. Our main contribution is an O(w)-competitive algorithm, where w is the length of an IP address. We also derive a lower bound which shows that our result is asymptotically optimal within a natural class of algorithms, based on so-called sticks.