Efficient topology discovery in OpenFlow-based Software Defined Networks

Abstract

Software Defined Networking (SDN) is a new networking paradigm, with a great potential to increase network efficiency, ease the complexity of network control and management, and accelerate the rate of technology innovation. One of the core concepts of SDN is the separation of the network's control and data plane. The intelligence and the control of the network operation and management, such as routing, is removed from the forwarding elements (switches) and is concentrated in a logically centralised component, i.e. the SDN controller. In order for the controller to configure and manage the network, it needs to have up-to-date information about the state of the network, in particular its topology. Consequently, topology discovery is a critical component of any Software Defined Network architecture. In this paper, we evaluate the efficiency of the de facto standard approach to topology discovery currently implemented by the major SDN controller frameworks, and propose simple and practical modifications, which achieve a significantly improved efficiency and reduced control overhead. We have implemented our new topology discovery approach on the widely used POX controller platform, and have evaluated it for a range of network topologies via experiments using the Mininet network emulator as well as a specific topology in the OFELIA SDN testbed. Our results show that our proposed modifications achieve an up to 40% reduction in controller load compared to the current state-of-the-art approach, while delivering identical discovery functionality.

Self-Healing Topology Discovery Protocol for Software-Defined Networks

“…As no study shows the OFDP operation for several SDNCs, we assume the switch distribution among SDNCs obtained from SHTD protocol. In contrast with [3], [4], in SHTD protocol each SDNC has to send and receive only one packet from each of its active interfaces which decrease the burden on SDNCs.…”

“…3(c) the reduction in the average number of packets managed by SDNCs considering two existing approaches as baseline, namely OpenFlow Discovery Protocol (OFDP) [3] and OFDPv2 [4], derived from equation (NumPkt baseline − NumPkt SHT D )/NumPkt baseline . As no study shows the OFDP operation for several SDNCs, we assume the switch distribution among SDNCs obtained from SHTD protocol.…”

“…Unlike conventional mechanisms [4], [3], the proposed protocol uses layer 2 messages to create a control tree rooted at SDNCs and it discovers the network topology before the establishment of the initial control connection. Once the control tree is created, each network device can establish a secure control channel to the SDNCs.…”

“…Given their topological nature, if the parent ports of leaf and v-leaf nodes fail, they cannot provide an alternative control path to the SDNCs. Hence, a one-bit field is used in the topoReply message in order to prune their neighbouring Send echoRepl y to node u association bit set 4:…”

“…Otherwise, SDNCs will not be able to discover the OpenFlow switches in the network. Additionally, these mechanisms also require a previous knowledge of network devices' characteristics such as number of active ports and MAC addresses [4]. This information is requested by SDNCs after the establishment of an initial control connection with each device.…”