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05 Dec 2015

High fidelity switch models for software defined network emulation

http://dl.acm.org/citation.cfm?id=2491188

… this split design can make planning and designing large SDNs even more challenging than traditional networks. While existing network emulators allow operators to ascertain the behavior of traditional networks when subjected to a given workload, we find that current approaches fail to account for significant vendor-specific artifacts in the SDN switch control path. We benchmark OpenFlow-enabled switches from three vendors and illustrate how differences in their implementation dramatically impact latency and throughput. We present a measurement methodology and emulator extension to reproduce these control-path performance artifacts, restoring the fidelity of emulation.

The performance of applications and services running in a network is sensitive to changing configurations, protocols, software, or hardware…

Network emulation
allowing network operators to deploy the same end-system applications and protocols on the emulated network as on the real hardware [8, 13, 15].

We argue that high-fidelity, vendor-specific emulation of SDN (specifically, OpenFlow) switches is required to provide accurate and repeatable experiments. … architectural choices made by switch vendors impact the end-to-end performance of latency-sensitive applications, such as webpage load times, database transactions, and some scientific computations.

… find two general ways in which switch design affects network performance: ✓ control path delays and flow table designs.

2 motivation

2.1 Variations in control path delays

the sequence of events that occurs when a new flow arrives that leads to the installation of a new forwarding rule in the switch… Packets from unmatched flows, on the other hand, are sent along the control path, which is often orders-of-magnitude slower.

… we verify that all Redis queries complete well within 1 ms when the required flow rules have been installed in advance.

Mininet is a popular option for emulating SDN-based networks [7, 11]. To emulate an OpenFlow network, it houses OVS instances on a single server on a virtual network topology that runs real application traffic.

reference