GCMI: A Generic Approach for SDN Control Message Interception
Robert Bauer, Addis Dittebrandt, Martina Zitterbart · 2019
This paper presents GCMI, a novel API for generic control message interception that can be used to programmatically access control messages exchanged between controllers and switches in a software-defined network. The approach allows it to program GCMI apps that register for specific control messages, e.g., all monitoring replies or flow table modification requests for a certain subnet. If such a control message is sent, it is redirected to the GCMI app where it may (or may not) be altered prior to forwarding to the original destination. This intermediate processing is widely used in the SDN domain, e.g., for transparent optimizations, verification or debugging purposes. In practice, however, the same interception functionality is re-implemented over and over again because there currently is no generic solution to access control messages. In this paper, we show that there is a strong demand for GCMI, present a proxy-based OpenFlow prototype and demonstrate the features and benefits of our approach by re-implementing different use cases that rely on control message interception.