Optimal Consistent Network Updates in Polynomial Time

TL;DR

This paper introduces a polynomial-time algorithm for computing optimal consistent network updates in SDN, ensuring per-packet consistency with maximal parallelism, contrasting with NP-complete cases for other properties.

Contribution

It provides the first polynomial-time solution for optimal consistent order updates in SDN, enabling efficient and safe network reconfigurations.

Findings

Polynomial-time algorithm for optimal updates

Maximal parallelism in network reconfiguration

Contrasts with NP-completeness of other properties

Abstract

Software-defined networking (SDN) allows operators to control the behavior of a network by programatically managing the forwarding rules installed on switches. However, as is common in distributed systems, it can be difficult to ensure that certain consistency properties are preserved during periods of reconfiguration. The widely-accepted notion of PER-PACKET CONSISTENCY requires every packet to be forwarded using the new configuration or the old configuration, but not a mixture of the two. If switches can be updated in some (partial) order which guarantees that per-packet consistency is preserved, we call this order a CONSISTENT ORDER UPDATE. In particular, switches that are incomparable in this order can be updated in parallel. We call a consistent order update OPTIMAL if it allows maximal parallelism. This paper presents a polynomial-time algorithm for finding an optimal consistent order update. This contrasts with other recent results in the literature, which show that for other classes of properties (e.g., loop-freedom and waypoint enforcement), the optimal update problem is NP-complete.