Extended indirect controller-legacy switch forwarding for link discovery in hybrid multi-controller SDN

Though widely perceived as a promising network architecture, Software Defined Networks (SDN) have inherent deployment issues, particularly in terms of a full SDN deployment paving the path for Hybrid Software Defined Networks (hSDN) and subsequently Multi-Controller h-SDN (MC-hSDN) to address limited scalability of the former. Networks allocate resources to applications based on their requirements which are taken care of by the controller. Existing link discovery protocols such as Link Layer Discovery Protocol (LLDP) and Broadcast Domain Discovery Protocol (BDDP) are able to detect links only for OpenFlow switch (OFS) in direct and indirect manners while Indirect Controller Legacy Forwarding (ICLF) scheme detects all links in h-SDN only for a single-controller environment, thus rendering link detection in MC-hSDN incomplete. This paper proposes a novel Extended ICLF (E-ICLF) scheme to fetch the topology in a multi-controller environment. A solitary PACKET_OUT (Pout) is emanated from every domain controller which circulates across the domain’s as nodes appending information which gets dispatched to the initiating controller. Experiments performed with Mininet indicate ports detection improvement and PACKET_ IN (Pin) message exchange reduction by an average of about (0.8%–44.8%) and (56.8%–93.2%) respectively with a fewer overhead of forwarded messages and convergence time to build the topology.