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...roller. Moreover, the controller must take care to minimize network anomalies during update procedures, such as packet drops or misroutes caused by temporary inconsistencies. Time-based configuration =-=[1]-=- can be a useful tool that enables an entire class of coordinated and scheduled configuration procedures. Time-triggered configuration allows coordinated network updates in multiple devices; a control...

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...ons. The recent interest in Software-Defined Networks (SDN) in some of these environments (e.g., [1]) gives rise to the problem of distributing accurate time in an SDN. A recently introduced approach =-=[2, 3]-=- suggests that network devices can significantly benefit not only from transporting accurate time, but also from using accurate time; time can be used to trigger coordinated network updates, reducing ...

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.... Using Time in SDN. The most well-known SDN protocol is OpenFlow. OpenFlow, as defined in [1], [2] does not make explicit use of time and synchronized clocks. However, a recently introduced approach =-=[3]-=-, [4] suggests the usage of accurate time to coordinate network updates in a simple1 manner, reducing packet loss and anomalies during configuration or topology changes. Accurate time can be a useful ...

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...ets carrying the old version tag are drained from the network, garbage collection is performed on the switches, removing the duplicate entries and leaving only the new configuration. In previous work =-=[29]-=- we argued that time is a powerful abstraction for coordinating network updates. We defined an extension [33] to the OpenFlow protocol [39] that allows time-triggered operations. This extension has be...

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... Updates in SDN Tal Mizrahi, Yoram Moses∗ Technion — Israel Institute of Technology 1 Introduction The usage of accurate time to schedule updates in software defined networks was recently proposed in =-=[1]-=-; time can be a powerful tool for applying network updates in a relatively simple manner and with a very brief period of inconsistency during the update. In the current paper we introduce the flow-swa...

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...network devices. The concept of using accurate time to trigger policy and routing changes was briefly discussed in [34]. Preliminary versions of this paper briefly introduced the timed update concept =-=[35]-=- and the flow swapping scenario [36]. The use of time for consistent updates was discussed in [26]. To the best of our knowledge, the current work is the first to present accurate time as a generic to...

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...migrate as fast as possible in order to minimize the effects of capacity constraint violations. A related but algorithmically more intricate technique is proposed by Mizrahi, Rottenstreich, and Moses =-=[17, 18, 19]-=-: They schedule updates at synchronized time slots, instead of just applying them as fast as possible. In their work, they show that time-based updates can be a powerful mechanism in SDNs, and make a ...

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...nstallation may vary from a few milliseconds to a few seconds. ∗This work was supported in part by the ISF grant 1520/11. †The Israel Pollak academic chair at Technion. A recently introduced approach =-=[6]-=-, [7] proposes to use accurate time and local clocks as a means to coordinate network updates. By using synchronized clocks, configuration changes can be scheduled in a way that guarantees a coordinat...