Hitless Reconfiguration Research Articles

Design and implementation of P4 virtual switches and P4 virtual networks

This paper introduces the design and implementation of P4 virtual switches (VSWs) and P4 virtual networks (VNs). The proposed switch virtualization supports multiple VSWs embedded in a single P4 physical switch (PSW). Similar to a PSW, users use standard P4 language to program their VSWs. Given a set of VSWs and their target PSW, our hypervisor integrates all the VSW programs to generate configuration files that enable the target PSW to become a platform to realize switch virtualization. Users can define customized header types and metadata for their VSWs. In addition, our system supports live reconfiguration. Reconfiguring a VSW in a PSW will not interrupt the other VSWs in the PSW. Based on the proposed switch virtualization scheme, we present the way to share multiple VNs in a P4 physical network to provide multitenant services. A VN is composed of multiple VSWs and multiple virtual links (VL), and each VN is provisioned with guaranteed bandwidth for their VLs. Each tenant can control and manage its own VN—similar to a dedicated P4 network. In addition, each tenant can assign a priority to its traffic. The proposed network virtualization guarantees traffic isolation, preventing inter-VN interference. Results on an experimental network used for performance evaluation show that our system can successfully generate VSWs and VNs. The proposed hitless reconfiguration method can prevent service interruptions between VSWs during VSW reconfiguration. The experimental results also show that our network virtualization can accurately guarantee the provisioned bandwidths of VNs in a physical P4 network.

Elastic Optical Interface With Variable Baudrate: Architecture and Proof-of-Concept

Varying the symbol rate is an alternative or complementary approach to varying the modulation format or the channel spacing to turn optical networks into elastic networks. We propose to allocate just-enough bandwidth for each optical connection by adjusting the symbol rate such that the penalty originating from long cascades of optical filters is contained. This helps reduce overprovisioning for lightpaths where full capacity is not needed, by (i) eliminating unnecessary regenerators and (ii) reducing the power consumption of terminals, when the clock rate of electronics is reduced along with the baudrate. We propose a novel architecture for an elastic optical interface by combining a variable bitrate transceiver, paired with an elastic aggregation stage, with software-defined control. We then report a real-time field-programmable-gate-array-based prototype that delivers flexible transport frames to be sent with a polarization-division multiplexed quadrature phase-shift keying modulation format. We interconnect this prototype with a commercial optical transport network switch and a centralized controller. We demonstrate fast and hitless reconfiguration of the interface and measure the reconfiguration time of hardware logic (<450 μs), as well as end-to-end control and the data plane (<0.9 s).

Hitless Reconfiguration of a PPLN-Based Multiwavelength Source for Elastic Optical Networks

Elastic optical networks may significantly take advantage of reconfigurable multiwavelength sources in order to maximize spectral efficiency and throughput. A multiwavelength source based on the line multiplication process taking place in a periodically poled lithium niobate waveguide has been recently proposed as a generator of tunable frequency combs. This source is stable and compact with respect to fiber-based solutions and does not require high radio frequency power. A transmitter employing the multiwavelength source is implemented and characterized in the static and dynamic regime, thus demonstrating hitless reconfiguration. The source also is tested within a three-node testbed employing commercial transceiver cards.