On the IP Traffic Matrix Problem in Hybrid SDN/OSPF Networks
  IP networks with a hybrid control plane deploy a distributed routing protocol like OSPF and the centralized paradigm of SDN in parallel. The advantages and disadvantages of a hybrid control plane have already been extensively discussed in the literature. This paper examines to what extent hybrid SDN/OSPF can solve the IP traffic matrix and related monitoring problems, inherent to the IP layer. The problem persists in hybrid networks, as the required SDN byte counters for a complete traffic matrix may not be sufficiently implemented (or even not at all), or the deployed SDN nodes may be too few, or not adequately located in the network. For such cases, we propose to augment the SDN traffic statistics with SNMP-based measurements on IP backup links. We address implementation and network function virtualization aspects of the required hybrid monitoring infrastructure and discuss the timing issues of the measurements based on hands-on experiences in our lab. We furthermore provide a placement algorithm for SDN nodes and backup links that can guarantee a complete IP traffic matrix. 
Marcel Caria and Admela Jukan
cs.NI