C-LLDP-monitoring: Latency Monitoring across Large-scale Software Defined Networks

This paper presents a network-wide latency monitoring method, called C-LLDP-monitoring, for large-scale Software Defined Networks (SDNs) with multiple controllers constructing a hierarchical control plane. C-LLDP-monitoring first uses each local controller in the lower layer to repeatedly inject Link Layer Discovery Protocol (LLDP) packets into its managed network domain to obtain the round-trip time (RTT) of links within the domain, and uses the root controller to receive the packets from the border switch in the neighboring domain to obtain the RRT of links between two neighboring domains, and then calculates the total network-wide path latency over the entire network. It avoids uncertainties introduced by the control channel and clock frequencies of different devices, requires no dedicated network infrastructure, and achieves continuous and accurate network-wide latency monitoring across large-scale multi-domain SDNs.