Relay-Based iBGP Multicasting in Software Defined Networks

In the Internet today, learnt prefixes are forwarded within autonomous systems (ASs) over internal Border Gateway Protocol (iBGP) sessions. Existing schemes for iBGP routing include the full-mesh (FM) solution, route reflection (RR) solution and confederation. Optimal prefix routing and route diversity are the main strength of the FM solution. However, it is rarely employed in a large networks due to its poor scalability. The RR scheme solves the scalability challenge at the cost of FM optimality due to Route Reflector's partial view of the network. The concept of Software Defined Networking (SDN) entails decoupling of the control plane from the forwarding plane such that the control plane is logically centralized benefiting from an overall knowledge of the network for decision making. In this work, we propose a solution based on multicasting which employs relay nodes in the iBGP message dissemination. The relay nodes are elected and act as boundaries of multicast groups, relaying and filtering prefixes into other multicast groups. We evaluate the use of single and multiple relay nodes per multicast group. Our solution brings session management scalability and minimization of duplicate prefix announcement through elimination of peer sessions deemed unnecessary. SDN controller is employed to configure and coordinate the multicast tree.