PAC.C [electronic resource] : a unified control architecture for packet and circuit network convergence
Keywords: Electrical Engineering

Service providers today face several challenges. By all accounts Internet traffic is growing at 40-50% per year, necessitating costly upgrades to carrier infrastructure. Yet carriers do not see a commensurate increase in revenue, nor do they see relative reductions in capital and operational expenditures (Capex and Opex). Part of the problem is that service providers today separately own and operate two distinct networks: packet-switched IP/MPLS networks and circuit-switched TDM/WDM Transport networks. These networks are typically planned, designed and managed by separate divisions even within the same organization, leading to substantial management overhead, functionality/resource duplication, and increased Capex/Opex. This is clearly an expensive and inefficient way to run networks. There have been other attempts to unify the control and management of circuit and packet switched networks -- essentially run one converged network instead of two -- but none have taken hold. In this thesis, we propose a simple way to unify both types of network using an emerging concept called Software Defined Networking (SDN). SDN advocates the separation of data and control planes in networks; where the data-plane can be abstracted and represented to external software-controllers running a Network Operating System (NetOS). All network control functions are implemented as applications on top of the NetOS. The applications make control decisions that manipulate an annotated-map of the network presented to them and kept consistent by the NetOS. In turn the NetOS translates the map-manipulations into data-plane reality by programming the data-plane switch flow-tables via a switch-API like OpenFlow. As circuits can readily be defined as flows, the basic idea is that a common-flow abstraction fits well with both packet and circuit switches; provides a common paradigm for control using a common-map abstraction; and makes it easy to control, jointly optimize, and insert new functionality into the network. We call our SDN based solution pac.c for packet and circuit .network convergence. We defined the common-flow abstraction as flow-tables that take the form of lookup-tables in packet switches and cross-connect tables in circuit switches. Together with a switch-API like OpenFlow, which we extended for circuit switches, it abstracts away layer and vendor specific hardware and interfaces, while providing a flexible forwarding plane for manipulation by a common control plane. The common-map abstraction was defined as one which provides full visibility into both packet and circuit switched networks, while abstracting away the complexity of state-dissemination from applications, allowing the latter to be implemented in a centralized manner. We built several prototypes to demonstrate and verify our architectural constructs. Our complete pac.c prototype emulates an inter-city carrier network, with access packet-switches in three cities, interconnected by hybrid packet-optical switches in the backbone, all under OpenFlow/SDN control. With this prototype, we verified the simplicity and extensibility of our architectural solution, compared to current state-of-the-art industry practice. More importantly, we presented qualitative architectural insights into why our solution fares better; and gave reasons why our control solution can succeed where GMPLS - the only previous attempt at unified control over packets and circuits - failed. Finally, we identified and demonstrated several new networking capabilities enabled at the packet-circuit interface, and offered architectural solutions to a number of deployment challenges faced by any new control solution. To demonstrate the benefits of reduced Total Cost of Ownership (TCO), we designed and analyzed today's IP networks and contrasted it with a converged packet-circuit network based on our control architecture. We found nearly 60% Capex savings and 40% Opex savings. More importantly the savings are insensitive to varying traffic matrices and grow as we dimension the network for increasing traffic demand. And finally, we introduced the map-abstraction in MPLS networks and demonstrated how existing packet services like traffic engineering can be replicated in an SDN based network, without the complexities of the IP/MPLS control plane. In doing so we drew parallels with SDN based control for packets and circuits. To summarize, we have proposed, designed, analyzed and demonstrated a converged IP/MPLS/Optical network architecturally based on SDN. The common platform helps reduce expenditures, provides existing services, and helps carriers innovate by easing the introduction of new revenue-generating services that differentiate them from other carriers. Our work is in the early stages but with further development, if these ideas are adopted by service providers, its main impact would be that they can remain profitable as the Internet grows. As a result they would then have greater incentive to invest in their networks, which in-turn could benefit society immensely.