Load-balanced Switch Architectures Research Articles

Safe Randomized Load-Balanced Switching by Diffusing Extra Loads

Load-balanced switch architectures are known to be scalable in both size and speed, which is of interest due to the continued exponential growth in Internet traffic. However, the main drawback of load-balanced switches is that packets can depart out of order from the switch. Randomized load-balancing of application flows by means of hashing on the packet header is a well-known simple solution to this packet reordering problem in which all packets belonging to the same application flow are routed through the same intermediate port and hence the same path through the switch. Unfortunately, this method of load-balancing can lead to instability, depending on the mix of flow sizes and durations in the group of flows that gets randomly assigned to route through the same intermediate port. In this paper, we show that the randomized load-balancing of application flows can be enhanced to provably guarantee both stability and packet ordering by extending the approach with safety mechanisms that can uniformly diffuse packets across the switch whenever there is a build-up of packets waiting to route through some intermediate port. Although simple and intuitive, our experimental results show that our extended randomized load-balancing approach outperforms existing load-balanced switch architectures.

Safe Randomized Load-Balanced Switching By Diffusing Extra Loads

Load-balanced switch architectures are known to be scalable in both size and speed, which is of interest due to the continued exponential growth in Internet traffic. However, the main drawback of load-balanced switches is that packets can depart out of order from the switch. Randomized load-balancing of application flows by means of hashing on the packet header is a well-known simple solution to this packet reordering problem in which all packets belonging to the same application flow are routed through the same intermediate port and hence the same path through the switch. Unfortunately, this method of load-balancing can lead to instability, depending on the mix of flow sizes and durations in the group of flows that gets randomly assigned to route through the same intermediate port. In this paper, we show that the randomized load-balancing of application flows can be enhanced to provably guarantee both stability and packet ordering by extending the approach with safety mechanisms that can uniformly diffuse packets across the switch whenever there is a build-up of packets waiting to route through some intermediate port. Although simple and intuitive, our experimental results show that our extended randomized load-balancing approach outperforms existing load-balanced switch architectures.

Safe Randomized Load-Balanced Switching by Diffusing Extra Loads

Load-balanced switch architectures are known to be scalable in both size and speed, which is of interest due to the continued exponential growth in Internet traffic. However, the main drawback of load-balanced switches is that packets can depart out of order from the switch. Randomized load-balancing of application flows by means of hashing on the packet header is a well-known simple solution to this packet reordering problem in which all packets belonging to the same application flow are routed through the same intermediate port and hence the same path through the switch. Unfortunately, this method of load-balancing can lead to instability, depending on the mix of flow sizes and durations in the group of flows that gets randomly assigned to route through the same intermediate port. In this paper, we show that the randomized load-balancing of application flows can be enhanced to provably guarantee both stability and packet ordering by extending the approach with safety mechanisms that can uniformly diffuse packets across the switch whenever there is a build-up of packets waiting to route through the some intermediate port. Although simple and intuitive, our experimental results show that our extended randomized load-balancing approach significantly outperforms existing load-balanced switch architectures.

A single-stage optical load-balanced switch for data centers

Load balancing is an attractive technique to achieve maximum throughput and optimal resource utilization in large-scale switching systems. However current electronic load-balanced switches suffer from severe problems in implementation cost, power consumption and scaling. To overcome these problems, in this paper we propose a single-stage optical load-balanced switch architecture based on an arrayed waveguide grating router (AWGR) in conjunction with fast tunable lasers. By reuse of the fast tunable lasers, the switch achieves both functions of load balancing and switching through the AWGR. With this architecture, proof-of-concept experiments have been conducted to investigate the feasibility of the optical load-balanced switch and to examine its physical performance. Compared to three-stage load-balanced switches, the reported switch needs only half of optical devices such as tunable lasers and AWGRs, which can provide a cost-effective solution for future data centers.

Research of a Load-Balanced Algorithm Based on Flow Mapping

Network operators would like high capacity router architectures that can offer guaranteed throughput,scalability and maintain packet ordering.However,current centralized crossbar-based architectures cannot scale to higher performance and port counts.The load-balanced switch architectures rely on two identical stages of fixed configuration meshes appear to be an effective way to scale Internet routers to very high capacities,they have the critical problem of packet mis-sequence with reordering complexity of O(N2).In this paper,we propose a region equalization architecture,in which every k consecutive intermediate inputs are organized as a region and each input port adopts a Uniform Fine-grain Frame Spreading(UFFS-k,where k is the aggregate factor) algorithm assigning k cells of the same flow to the fixed mapping region in a fine-grain manner during k successive external time slots.We give theoretical proofs that 100% throughput and packet ordering can be achieved by using UFFS-k algorithm at each input.To avoid traffic concentration in regions,a dual-rotation mapping algorithm is used to construct a mapping relationship between flows from different inputs and regions.Furthermore,in order to distribute input traffic equally among the intermediate inputs,the UFFS-k algorithm dispatches each unit frame according to a global traffic distribution matrix maintained at each input.It is proofed that for each output port j,the lengths of OQj are equal for the same region and the lengths OQj differ by at most 1 for any two different regions,thus achieving 100% load balancing degree.The UFFS-k algorithm is distributed and can operate independently in each input.It spreads each flow to intermediate inputs according to the mapping relationship between flows to regions as well as traffic distribution state.As the simulation results demonstrate,when k=2,UFFS-k offers improved delay performance among existing scheduling algorithms that guarantee packet ordering.

The Concurrent Matching Switch Architecture

Network operators need high-capacity router architectures that can offer scalability, provide throughput guarantees, and maintain packet ordering. However, current centralized crossbar-based architectures cannot scale to fast line rates and high port counts. On the other hand, while load-balanced switch architectures that rely on two identical stages of fixed configuration meshes appear to be an effective way to scale Internet routers to very high capacities, they incur a large worst-case packet reordering that is at best quadratic to the switch size. In this paper, we introduce the concurrent matching switch (CMS) architecture, which also uses two identical stages of fixed configuration meshes with the same scalability properties as current load-balanced routers. However, by adopting a novel contention-resolution architecture that is scalable and distributed, the CMS architecture enforces packet ordering throughout the switch. Using the CMS architecture, we show that scalability, 100% throughput, packet ordering, and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> (1) amortized time complexity with sequential hardware per linecard can all be achieved. We further demonstrate a delay analysis for the CMS architecture.

Feedback-Based Scheduling for Load-Balanced Two-Stage Switches

A framework for designing feedback-based scheduling algorithms is proposed for elegantly solving the notorious packet missequencing problem of a load-balanced switch. Unlike existing approaches, we show that the efforts made in load balancing and keeping packets in order can complement each other. Specifically, at each middle-stage port between the two switch fabrics of a load-balanced switch, only a single-packet buffer for each virtual output queueing (VOQ) is required. Although packets belonging to the same flow pass through different middle-stage VOQs, the delays they experience at different middle-stage ports will be identical. This is made possible by properly selecting and coordinating the two sequences of switch configurations to form a joint sequence with both <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">staggered symmetry property</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-order packet delivery property</i> . Based on the staggered symmetry property, an efficient feedback mechanism is designed to allow the right middle-stage port occupancy vector to be delivered to the right input port at the right time. As a result, the performance of load balancing as well as the switch throughput is significantly improved. We further extend this feedback mechanism to support the multicabinet implementation of a load-balanced switch, where the propagation delay between switch linecards and switch fabrics is nonnegligible. As compared to the existing load-balanced switch architectures and scheduling algorithms, our solutions impose a modest requirement on switch hardware, but consistently yield better delay-throughput performance. Last but not least, some extensions and refinements are made to address the scalability, implementation, and fairness issues of our solutions.

The interleaved matching switch architecture

Operators need routers to provide service guarantees such as guaranteed flow rates and fairness among flows, so as to support traffic engineering and real-time traffic. However, current centralized input-queued router architectures cannot scale to fast line rates while providing these service guarantees. On the other hand, while load-balanced switch architectures that rely on two identical stages of fixed-configuration switches appear to be an effective way to scale Internet routers to very high capacities, there is currently no practical and scalable solution for providing service guarantees in these architectures. In this paper, we introduce the interleaved matching switch (IMS) architecture, which relies on a novel approach to provide service guarantees using load-balanced switches. The approach is based on emulating a Birkhoff-von Neumann switch with a load-balanced switch architecture and is applicable to any known admissible traffic. We show that service guarantees, 100% throughput, and packet ordering can be achieved with O(1) online complexity. In cases where fixed frame sizes are applicable, we also present an efficient offline frame-based decomposition method. More generally, we show that the IMS architecture can be used to emulate any input queued or combined input-output queued switch, leveraging a large body of known results for ensuring stability.