文摘
Software Defined Networking (SDN) is an emerging paradigm that is expected to revolutionize computer networks. Methods for measuring Quality of Service (QoS) parameters such as bandwidth utilization, packet loss, and delay have been recently introduced in literature for SDN-based scenarios, but they required almost invariably a completely different approach with respect to traditional network environments, thus facing new challenges and exploiting new opportunities. An important dynamic path characteristic is Available Bandwidth (ABW), that has strong impact on a wide range of applications, but is a metric very hard to estimate with traditional approaches. In this paper we focus our analysis on ABW measurement based on messages in the OpenFlow protocol. We present both analytical results and experimental evaluation (in Mininet emulation and using Floodlight, OpenDaylight and ONOS controllers) of measurement error due to network delay between the SDN switches and the controller. Based on our results we propose to extend the OpenFlow protocol with a local timestamping mechanism, providing and discussing two different implementations of this feature. The presented analysis and the proposed extension of OpenFlow protocol are not restricted to ABW, and can benefit measurement of other network metrics in SDN.
