  Software Defined Networking (SDN) not only enables agility through the
realization of part of the network functionality in software but also
facilitates offering advanced features at the network layer. Hence, SDN can
support a wide range of middleware services; network performance monitoring is
an example of these services that are already deployed in practice. In this
paper, we exploit the use of SDNs to efficiently provide application monitoring
functionality. The recent rise of complex cloud applications has made
performance monitoring a major issue. We show that many performance indicators
can be inferred from messages exchanged among application components. By
analyzing these messages, we argue that the overhead of performance monitoring
could be effectively moved from the end hosts into the SDN middleware of the
cloud infrastructure which enables more flexible placement of logging
functionality. This paper explores several approaches for supporting
application monitoring through SDN. In particular, we combine selective
forwarding in SDN to enable message filtering and reformatting, and propose a
customized port sniffing technique. We describe the implementation of the
approach within the standard SDN software, namely OVS. We further provide a
comprehensive performance evaluation to analyze advantages and disadvantages of
our approach, and highlight the trade-offs.
