SDN Partitioning: A Centralized Control Plane for Distributed Routing Protocols

Abstract

Hybrid IP networks that use both control paradigms -distributed and centralized -promise the best of two worlds: programmability of SDN, and reliability and fault tolerance of distributed routing protocols, like OSPF. Typically, a hybrid network deploys SDN to control prioritized traffic and OSPF to assure care-free operation of best effort traffic. We propose a new hybrid network architecture, called SDN Partitioning (SDNp), which establishes centralized control over the distributed routing protocol by partitioning the topology into sub-domains with SDN-enabled border nodes. In our approach, OSPF's routing updates have to traverse SDN border nodes to reach neighboring sub-domains. This allows the central controller to modify how sub-domains view one another, which in turn allows to steer inter-subdomain traffic. The degree of dynamic control against simplicity of OSPF can be traded off by adjusting the size of the sub-domains. This paper studies the technical requirements, presents a novel scheme for balanced topology partitioning, and provides the corresponding network management models for SDNp. Our performance evaluation shows that -already in its minimum configuration with two sub-domains -SDN Partitioning provides significant improvements in all respects compared to legacy routing protocols, whereas smaller sub-domains provide network control capabilities comparable to full SDN deployment.

Link Capacity Planning for Fault Tolerant Operation in Hybrid SDN/OSPF Networks

“…"Fibbing", proposed in [15] and [16], shares with SDN Partitioning the idea of steering the legacy routing protocol by introducing fake information, but differs significantly from our approach regarding the mode of operation. This paper is the first to extend our previous work on SDN Partitioning [10], [17], [18] with an analysis of the required link capacities for fault tolerant operation.…”

“…In graph theory parlance, this means that the SDN-enabled routers must constitute a vertex separator. The three example networks used in the numerical evaluation have been partitioned with the algorithm that we introduced in [18].…”

Exploiting the control power of SDN during the transition from IP to SDN networks

“…9 This replacement method therefore considers different areas where, by turns, the most suitable node to become SDN is added to the area with the token at each iteration. In fact, the hybrid IP/SDN scenario again presents opportunities to exploit the partition of a network topology into subdomains with the aim of improving network performance.…”

“…In fact, the hybrid IP/SDN scenario again presents opportunities to exploit the partition of a network topology into subdomains with the aim of improving network performance. 9 This replacement method therefore considers different areas where, by turns, the most suitable node to become SDN is added to the area with the token at each iteration. Nodes suitability is assessed according to the number of non-controllable links each node has in a similar way than in the previously explained MNL approach.…”

Increased network routing efficiency through coordinated Fibbing

“…Another study partitions a network into some subdomains. 16 The border nodes of the subdomains are controlled by SDN, and the nodes in the subdomains are controlled by distributed routing, such that OSPF's LSAs have to traverse SDN border nodes to reach neighboring subdomains. When the LSAs cross the border nodes, the controller can do some operations and configurations to the network through the border nodes.…”