Optimal Virtual Slice Composition Toward Multi-Tenancy Over Hybrid OCS/OPS Data Center Networks

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

In optical packet switching (OPS)-based data center networks (DCNs), it is preferred to set up temporal optical circuit switching (OCS) paths for large-data transmission that requires high reliability. However, inappropriate OCS path selection could severely affect the original OPS traffic. This is because an OCS path may break the network topology and cause OPS packet circulations. We propose to maintain bypassing routes for every link of the OCS path when it is established. Then, the OPS packets can bypass the OCS links by being deflected to the bypassing routes. Therefore, this method facilitates the coexistence of OCS in OPS-based DCNs. Numerical simulations demonstrate the benefit achieved by our proposal compared with non-bypassing-route scenarios.

This paper presents performance evaluations and comparisons of different sharing approaches applied to the available optical bandwidth in data center networks. The recently proposed hybrid optical network concept, which combines multi-wavelength optical packet switching (OPS) and optical circuit switching (OCS) in WDM networks, is compared with a service-specific sharing model. Simulation results show that a careful design of dedicated channel allocation gives similar performance to a complete channel sharing with prioritized scheduling, which is however more flexible.

Data center networks (DCNs) are at the forefront of a radical transformation, fueled by the rapid rise of artificial intelligence (AI), cloud-native adoption, and enterprise digitalization, which together place unprecedented demands on their design and performance. From healthcare AI and intelligent transportation to business analytics, modern DCNs are expected to support a diverse and evolving mix of bandwidth-demanding applications, each with distinct quality of service (QoS) requirements. Yet, most state-of-the-art DCN solutions rely on oversimplified DCN data traffic models, failing to address the required application-level differentiation in terms of end-to-end (E2E) latency demands. In response, we propose ALAS-DCN, a novel, to our knowledge, application-aware, low-latency, scalable DCN architecture, based on optical packet switching in the intra-rack and inter-rack domains that is both designed and rigorously evaluated using commercial QoS specifications and realistic traffic patterns of different applications coexisting within the same DCN. ALAS-DCN integrates three hierarchical optical sub-networks: intra-rack, inter-rack, and bridge, each governed by a custom wavelength division multiplexing (WDM) medium access control (MAC) protocol that dynamically prioritizes critical traffic packets, according to the specific application E2E latency demands. Unlike prior approaches, our evaluation leverages realistic workload traces generated by established traffic generators, capturing the application diversity within modern data center (DC) environments. Extensive experimental simulations across five representative DC categories, each hosting a different mix of modern applications, demonstrate that ALAS-DCN consistently achieves up to 95% throughput efficiency and sub-µs latency for high priority traffic across a variety of applications, consistently meeting their differentiated latency constraints. Scalable up to 20,000 servers, ALAS-DCN redefines the DCN as not just a transport layer but an intelligent enabler of next-generation application performance.

We develop an integrated optical packet and circuit switching node in which signaling via optical packet switching is implemented. We demonstrate 80 (8λ × 10) Gbit/s optical packet switching with <;1E-4 packet-loss-rate, 8-lightpaths establishment, and dynamic wavelength-resources control.

Optical Circuit Switching (OCS) provides a good support for the services requiring high bandwidth and Quality of Service (QoS). When the character of network traffic changes from voice-oriented to data-oriented, OCS must cooperate with new switching mechanisms such as Optical Burst Switching (OBS) to improve performance. So a Hybrid Optical Switching (HOS) system is proposed. In HOS, different traffics are classified and both OBS and OCS can be processed. At the same time, delay buffer mechanisms, which are Fiber Delay Line (FDL) and electronic buffering, are introduced in HOS to solve the contention of OBS bursts. And a wavelengths classification mechanism, which assigns some wavelengths dedicated to OCS traffics, is provided to guarantee the QoS of OCS. To analyze the performance in theory, models based on Markovian theory and iterative method are provided. The results got by theory are accurate compared with simulations. The use of delay buffer can decrease the blocking probability of OBS and increase resource utilization. Wavelength classification mechanism benefits to improve OCS's performance.

We present a control plane architecture to enable software-addressable optical acceleration from the application layer. The architecture is experimentally examined on a cluster-computing test-bed by enabling physical layer optical multicasting on-demand for the application layer to achieve non-blocking performance.

Optical circuit switching may be instrumental in meeting the cost, energy, and aggregate bandwidth requirements of future data center networks. However, conventional MEMS beam-steering cross-connects cannot provide submillisecond switching with the port count necessary for data centers. Here, we investigate a novel noncrossbar selector switch architecture and pupil-division switching layout to improve optical switching performance by relaxing the requirement of arbitrary switch configurability. This architecture and switch design enable MEMS beam-steering micromirrors to scale to microsecond response speeds while supporting high port count and low loss switching, and can realize a number of useful interconnection topologies. We present the design, fabrication, and experimental characterization of a proof-of-principle prototype using a single comb-driven MEMS mirror to achieve 150 μs switching of 61 ports between four preprogrammed interconnection mappings. We demonstrate the scalability of this switch architecture with a detailed optical design of a 2048-port selector switch with 20 μs switching time.

All optical or hybrid electrical/optical switching data center network (DCN) architectures are capable of adapting the optical-layer topology to various network traffic demands based on the flexibility of optical switching technology. The topology reconfiguration strategies in previous research simply attempt to reconfigure optical circuit switching (OCS) links to offload heavier rack-to-rack traffic. However, due to the complex multi-layer interconnections and the various network traffic patterns in DCNs, the OCS links will not only offload the network traffic between its source and destination racks, but also forward the network traffic that belongs to the adjacent racks of the source and destinations racks. Previous strategies ignore the forwarding traffic and result in sub-optimal solutions. In order to overcome the shortcomings of previous methods and make full use of the OCS link resources in DCNs, an effective topology reconfiguration strategy named optical circuit bridge (OCBridge) has been proposed in our recent work. The main idea of our OCBridge is to take into account the traffic demands between the source and destination regions of each OCS link. In this paper, we first review our OCBridge, and then in simulation, we evaluate the performance of our OCBridge by testing it in two typical OCS-based DCNs, including OpenScale and Helios. Under our OCBridge, we analyze the outstanding network throughput performance of the DCNs and investigate the communication distance of traffic demands. Finally, in experiment, we deploy our OCBridge to a small prototype of OpenScale and verify that our OCBridge is capable of accelerating the distributed computing applications compared with previous topology reconfiguration strategies.

Hybrid Optical Packet Switching is a prominent solution for boosting a Data Centers' performance. We reaffirm this hypothesis by studying network latencies and showing that hybrid switching delivers the best performance compared to all-electronic one.

A hybrid optical/electrical datacenter network (HOE-DCN) integrates the benefits of electrical packet switching (EPS) and optical circuit switching (OCS) for better architectural scalability. Meanwhile, as each network service usually involves multiple virtual machines (VMs) that form a virtual network (VNT), how to reconfigure the VNTs in an HOE-DCN to adapt to the dynamic network environment becomes an interesting and important problem to tackle. In this work, we optimize the procedure of VNT reconfigurations that remap VNTs to given virtual network embedding (VNE) schemes, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> , scheduling the required VM migrations and optical cross-connect (OXC) reconfiguration properly such that the overall VNT reconfiguration latency can be minimized. We first assume that all the VM migrations should be scheduled before the OXC reconfiguration to minimize service interruptions, and formulate a mixed integer linear programming (MILP) model to solve the scheduling problem exactly. Then, with the same assumption, we propose a time-efficient heuristic to schedule parallel VM migrations in batches such that the bandwidth competition can be significantly relieved. Finally, we divide the OXC reconfiguration into several progressive steps, and design a joint scheduling algorithm to arrange VM migrations together with the OXC reconfiguration steps.

Many proposals have demonstrated the efficiency advantages of software-defined networking (SDN) in managing data center networks. Common practices employ centralized traffic engineering (TE) in the SDN control plane to optimize load balancing and throughput. Meanwhile, for high availability purposes, the control plane is partitioned to ensure the impact of a single faulty controller is contained. However, the interaction between these two aspects is often overlooked. In particular, we show that the current control plane partitioning approach leads to imbalanced link loads and degraded application performance. To address this issue, we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">virtual slicing</i>, a new control plane partitioning scheme. Virtual slicing achieves desirable traffic engineering performance while retaining the availability guarantees from the current approach. Virtual slicing is implemented and evaluated with real-world and synthetic traffic traces on production spine-free data center networks. Results show that virtual slicing reduces tail link utilizations by up to 28.4%, and improves flow completion times by up to 36%.

Increasing demands for distributed machine learning (DML) have posed significant pressure on data-center networks (DCNs). This promotes the adoption of reconfigurable all-optical interconnects (AOI) in DCNs leveraging optical circuit switching (OCS) for better performance on throughput, energy efficiency, and data transfer latency. Despite their benefits, these OCS-based DCNs (ODCNs) still bear limited flexibility due to the larger switching granularity and longer reconfiguration latency of OCS. To address this issue, this work introduces in-network computing (INC) in an ODCN to realize P4INC-AOI, which can orchestrate INC and AOI to explore their mutual benefits for accelerating the training of DML jobs with less AOI reconfigurations. In the control plane of P4INC-AOI, we address the scheduling of concurrent DML jobs by formulating a mixed integer linear programming (MILP) model and proposing a time-efficient heuristic, to allocate multi-dimensional resources and configure AOI for minimizing the longest job completion time (JCT) across workloads. For the data plane, we extend existing in-network gradient aggregation schemes to accelerate DML jobs more efficiently. We first implement P4INC-AOI and verify its performance in a small-scale ODCN testbed, and further justify its effectiveness with large-scale simulations. Our experimental results demonstrate that compared with an ODCN without INC, P4INC-AOI not only cuts down AOI reconfigurations effectively but also reduces the average JCT of DML jobs in ResNet50 and VGG16 by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$46.66\%$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$56.34\%$</tex-math> </inline-formula> , respectively.

Data center networks, using a reliable, high speed communication network, is a core component of cloud computing. Recently, optical networks using Space Division Multiplexing has been proposed as a solution to the speed bottleneck anticipated in data center networks. To our knowledge the new challenges of designing such communication systems have not been addressed yet. In this paper we have proposed an optimal approach to the problem of developing a path-protection scheme to handle communication requests in data center (DC) networks using elastic optical networking and space division multiplexing. We have formulated our problem as an Integer Linear Program (ILP). We have also proposed a heuristic that can handle problems of practical size. Our simulations explore important features of our approach.

The dynamic traffic changes in an optical circuit switching based data-center network (ODCN) can make the utilization of its optical connections fragmented, degrading the efficiency of service provisioning in the ODCN. Consequently, connection defragmentation becomes imperative. However, consolidating traffic onto fewer connections may unilaterally add the risk of bandwidth contention and undermine ODCNs’ robustness against unexpected traffic bursts. To address this issue, we propose risk-aware connection defragmentation (RA-cDF), which explores the topology flexibility of ODCN to consolidate traffic such that the active optical connections through optical circuit switching (OCS) switches can be minimized together with the risk of future bandwidth contention on remaining connections. We formulate a mixed integer linear programming (MILP) model to address the RA-cDF problem exactly, followed by a heuristic to solve it time-efficiently. Extensive simulations confirm the effectiveness of our proposals.