Design and analysis of a new self-routing network

A new self-routing network constructed from the sorting and the routing cells is proposed. The complexity of the new network is roughly twice as much as that of a pure banyan network. The new network can be viewed as an implementation of the load-sharing network which requires a very simple management. Its performance under uniform and nonuniform traffic models is analyzed for the unbuffered case. It is found that a higher degree of nonuniformity results in a better performance for certain forms of nonuniform traffic matrices. Simulations are performed to obtain the normalized throughputs and mean packet delays for the single-buffered case. Different from single-buffered pure banyan networks, the mean delay of high-traffic packets is smaller than that of low-traffic packets for a particular form of nonuniform traffic matrices. In addition to performance improvement, the new network is easy to diagnose. Some variations of the proposed network are also studied     

Sliding Banyan network

The sliding Banyan network is described and evaluated. The novel three-dimensional (3-D) multistage network topology employs a macro-lenslet array in a retroreflective configuration to effect the required shuffle link patterns across a single two-dimensional (2-D) multichip array of “smart pixels”. An electronic deflection routing scheme, based on simple destination tag self-routing, is employed within the smart pixels, Internal packet blocking is efficiently avoided because deflected packets are routed through individualized banyan networks that have “slid” in the time dimension to accommodate each packet's routing needs. Simulations show that this self-routing approach reduces the number of stages, and hence the number of switching and interconnection resources necessary to achieve a specified blocking probability. Experimental focusing and registration results, using arrays of vertical cavity surface emitting lasers, show that conventional optical imaging technology is suitable for this architecture. The results indicate that the sliding banyan approach will overcome the current performance constraints of conventional metallic interconnections and be scalable to ATM switching applications with aggregate throughputs in the Tb/s regime     

Buffered or unbuffered: a case study based onlogd(N,e,p) networks

Two implementation styles (buffered and unbuffered) have been used for constructing multistage interconnection networks for ATM switching. Conventional studies have shown that an unbuffered network, while having a simpler design, produces a lower throughput than a buffered network. But most of these studies, based on the assumption that each cell is routed independently (i.e. per-cell routing), ignored the out-of-sequence transmission problem of a buffered network in a virtual-channel environment. One way to keep the packet sequence for a buffered network without adding additional hardware is to fix the path for each virtual channel. We compute the throughput of this approach in designing nonblocking networks and compare it with that of the unbuffered approach. The base of our comparison is log_d(N,e,p) networks. The results show that a fixed-path-routing buffered network will have a throughput even lower than that of an unbuffered network     

面向动态拓扑网络的深度强化学习路由技术

针对现有智能路由技术无法适用于动态拓扑的不足,提出了一种面向动态拓扑的深度强化学习智能路由技术,通过使用图神经网络近似PPO(Proximal Policy Optimization)强化学习算法中的策略函数与值函数、策略函数输出所有链路的权值、基于链路权值计算最小成本路径的方法,实现了路由智能体对不同网络拓扑的泛化....     

PR-banyan: a packet switch with a pseudorandomizer for nonuniformtraffic

Buffered banyan networks are highly vulnerable to nonuniform traffic, due to the path sharing as well as the existence of only a single path per network input-output pair. Improving on an earlier packet distribution network which is a banyan network itself, a single-stage packet-scattering hardware, called the pseudo-randomizer (PR), is proposed. The PR-banyan, the PR followed by a buffered banyan, is analyzed under nonuniform traffic, and is shown to be highly effective under nonuniform traffic. The analytic results are shown to match the simulation results very closely     

Evaluation of pipelined dilated banyan switch architectures for ATMnetworks

In the pipeline banyan (PB), the reservation cycle in the control plane is made several times faster than payload transmission in data plane. This enables pipelining multiple banyans. It is observed that the ratio of throughput to switching delay (service rate) is relatively low in the PB due to the banyan. For this, we present a scalable pipelined asynchronous transfer mode (ATM) switch architecture employing a family of dilated banyan (DB) networks together with their complexity analysis and performance. A DB can be engineered between two extremes: (1) a low-cost banyan with internal and external conflicts, or (2) a high-cost conflict-free fully connected network with multiple outlets. Between the two extremes lies a family of DBs having different switching delays and throughputs. Increasing the dilation degree reduces path conflicts, which produces noticeable increase in service rate due to increase in throughput and decrease in path delay. Compared to PB, the pipelined dilated banyan (PDB) requires smaller number of data planes for the same throughput, or provides higher throughput for a given number of data planes. Simulation of PDB is carded out under uniform traffic and simulated ATM traffic. We study the switch performance while varying the load, buffer size, and number of data planes. To analyze the robustness of the switch, we show that performance is not degradable under ATM traffic with temporal and spatial burstiness generated using the on-off model. The PDB is scalable with respect to service rate and can be engineered with respect to: (1) cell loss rate; (2) hardware resources; (3) size of buffers; (4) switching delays; and (5) delay incurred to higher priority traffic. The PDB can deliver up to 3.5 times the service rate of the PB with only linear increase in hardware cost     

CAPACITY EVALUATION OF MULTI-CHANNEL WIRELESS AD HOC NETWORKS

In this paper, the capacity of multi-channel, multi-hop ad hoc network is evaluated.In particular, the performance of multi-hop ad hoc network with single channel IEEE 802.11 MAC utilizing different topologies is shown. Also the scaling laws of throughputs for largescale ad hoc networks and the theoretical guaranteed throughput bounds for multi-channel grid topology systems are proposed. The results presented in this work will help researchers to choose the proper parameter settings in evaluation of protocols for multi-hop ad hoc networks.     

Maximum achievable throughputs for uncoded OPPM and MPPM in opticaldirect-detection channels

Tight upper and lower bounds on the maximum throughputs for both overlapping and multipulse pulse position modulation (OPPM and MPPM) in optical direct-detection channels are derived. The corresponding pulse-position multiplicities are estimated. Simple lower bounds for the maximum achievable throughput (with the error rate not exceeding a certain threshold) are obtained for OPPM. A comparison between the maximum achievable throughputs for both OPPM and MPPM is also considered. Our results suggest using MPPM for high efficient transmission and OPPM for low efficient transmission. Namely, MPPM should be used when the transmission efficiency exceeds 0.027 nats/photon     

Architecture of a packet switch based on banyan switching networkwith feedback loops

The authors propose and describe an original feedback banyan switching network topology and control algorithm. This feedback banyan network prevents congestion even at high throughput. It does so by establishing a feedback route for the output packets from the output port to the input port of the banyan switching network. Input accommodated logical channels that do not encounter congestion within the switching network are output directly from the intended output port. Other packets are returned to the input port via the feedback route, then rerouted     

PCE-based fast path control in multi-domain photonic networks

We discuss issues for controlling an optical path in large-scale photonic networks, and introduce an inter-domain path control system based on Path Computation Elements (PCEs). In the system, maximum flow information enables the load balancing of traffic, and Path Key scheme preserve the confidentiality of internal topology information among carrier networks. Based on the experimental results, we show the path setup in the introduced system is significantly faster than the manual path setup among domains in current carriers' networks. For the additional reduction of the path setup time, we propose the domain-wise paralleled signaling method. We also show that decreasing the number of nodes per domain makes path setup faster in the introduced system with deployment of the proposed signaling method.     

FB-banyans and FB-delta networks: Fault-tolerant networks for broadband packet switching

Many fast packet switches for the broadband integrated services digital network (BISDN) in the literature are based on banyan networks. Although banyan networks possess nice properties such as a simple control and a low hardware cost, they are unique-path networks. Since there is a unique path from an input to an output in a banyan network, a single component failure may disrupt services of some nodes connected to such a network. Moreover, banyan networks are also blocking networks; packets can be lost within the networks. To reduce the packet loss, buffered banyan networks can be used. In an earlier work we have proposed the addition of backward links to otherwise unidirectional banyan networks to create B-banyans (and B-delta networks). Backward links not only function as implicit buffers for blocked packets, but also provide multiple paths for each input-output connection. However, the multiple paths in B-banyans may not be disjoint. In this paper, we enhance B-banyans and B-delta networks in such a way that the resulting networks can provide disjoint multiple paths for each input-output pair. The existence of disjoint multiple paths has a significant effect on the network fault-tolerance. The new networks, called FB-banyans and FB-delta networks, are k fault-tolerant, where k is the number of backward links per switch and is less than the switch size. They are also robust to more than k faults, depending on the locations of faults. The maximal fault-tolerance is achieved when k is the switch size minus 1. The performance of the new networks is analysed and compared to that of other networks of interest. FB-banyans and FB-delta networks can be used as a switch fabric for fast packet switches to provide performance comparable to that of buffered banyan networks and good fault tolerance.     

Design and analysis of a novel fast packet switch-pipeline banyan

Proposes a new fast packet switch architecture-pipeline banyan. It has a control plane and a number of parallel data planes which are of the same banyan topology. Packet headers are self-routed through the control plane to their destinations. As a result, they establish the corresponding routing paths in the data planes. The data planes do not need to do routing decisions, hence their complexity can be significantly reduced. Pipeline banyan can give a close to 100% maximum throughput and can deliver packets in a sequential order. Through analysis and simulation, the authors show that pipeline banyan has a better throughput and packet loss performance when compared with other banyan-type switch architectures     

Localized and configurable topology control in lossy wireless sensor networks

Wireless sensor networks (WSNs) introduce new challenges to topology control due to the prevalence of lossy links. We propose a new topology control formulation for lossy WSNs. In contrast to previous deterministic models, our formulation captures the stochastic nature of lossy links and quantifies the worst-case path quality in a network. We develop a novel localized scheme called configurable topology control (CTC). The key feature of CTC is its capability of flexibly configuring the topology of a lossy WSN to achieve desired path quality bounds in a localized fashion. Furthermore, CTC can incorporate different control strategies (per-node/per-link) and optimization criteria. Simulations using a realistic radio model of Mica2 motes show that CTC significantly outperforms an representative traditional topology control algorithm called LMST in terms of both communication performance and energy efficiency. Our results demonstrate the importance of incorporating lossy links of WSNs in the design of topology control algorithms.     

Impact of Interference on Multi-Hop Wireless Network Performance

In this paper, we address the following question: given a specific placement of wireless nodes in physical space and a specific traffic workload, what is the maximum throughput that can be supported by the resulting network? Unlike previous work that has focused on computing asymptotic performance bounds under assumptions of homogeneity or randomness in the network topology and/or workload, we work with any given network and workload specified as inputs.A key issue impacting performance is wireless interference between neighboring nodes. We model such interference using a conflict graph, and present methods for computing upper and lower bounds on the optimal throughput for the given network and workload. To compute these bounds, we assume that packet transmissions at the individual nodes can be finely controlled and carefully scheduled by an omniscient and omnipotent central entity, which is unrealistic. Nevertheless, using ns-2 simulations, we show that the routes derived from our analysis often yield noticeably better throughput than the default shortest path routes even in the presence of uncoordinated packet transmissions and MAC contention. This suggests that there is opportunity for achieving throughput gains by employing an interference-aware routing protocol.     

Design and performance evaluation of unbuffered self-routingnetworks for wide-band packet switching

The design of several unbuffered self-routing networks for wideband packet switching is presented. These networks possess many attractive characteristics, including simple node design, simple fault diagnosis, tolerance of faults, tolerance of unbalanced load, and packets delivered in sequence. It is shown, through analysis and simulation, that the maximum throughput of an unbuffered self-routing network is greater for fixed packet lengths than for exponentially distributed packet lengths. This means that the maximum throughput of an unbuffered self-routing network will be different for such applications as ATM (asynchronous transfer mode) and frame-relay, if they do not have the same packet length distribution     

Architecture, performance, and implementation of the tandem banyanfast packet switch

The authors propose a new space-division fast packet switch architecture based on banyan interconnection networks, called the tandem banyan switching fabric (TBSF). It consists of placing banyan networks in tandem, offering multiple paths from each input to each output, thus overcoming in a very simple way the effect of conflicts among packets (to which banyan networks are prone) and achieving output buffering. From a hardware implementation perspective, this architecture is simple in that it consists of several instances of only two VLSI chips, one implementing the banyan network and the other implementing the output buffer function. The basic structure and operation of the tandem banyan switching fabric are described, and its performance is discussed. The authors propose a modification to the basic structure which decreases the hardware complexity of the switch while maintaining its performance. An implementation of the banyan network using a high-performance BiCMOS sea-of-gates on 0.8-μm technology is reported     

ATM-based routing in LEO/MEO satellite networks with intersatellitelinks

An asynchronous transfer mode (ATM)-based concept for the routing of information in a low Earth orbit/medium Earth orbit (LEO/MEO) satellite system including intersatellite links (ISLs) is proposed. Specific emphasis is laid on the design of an ATM-based routing scheme for the ISL part of the system. The approach is to prepare a virtual topology by means of virtual path connections (VPCs) connecting all pairs of end nodes in the ISL subnetwork for a complete period in advance, similar to implementing a set of (time dependent) routing tables. The search for available end-to-end routes within the ISL network is based on a modified Dijkstra (1959) shortest path algorithm (M-DSPA) capable of coping with the time-variant topology. With respect to the deterministic time variance of the considered ISL topologies, an analysis of optimization aspects for the selection of a path at call setup time is presented. The performance of the path search in combination with a specific optimization procedure is-by means of extensive simulations-evaluated for example LEO and MEO ISL topologies, respectively     

Utilizing Redundancy for Timing Critical Interconnect

Conventionally, the topology of signal net routing is almost always restricted to Steiner trees, either unbuffered or buffered. However, introducing redundant paths into the topology (which leads to non-tree) may significantly improve timing performance as well as tolerance to open faults and variations. These advantages are particularly appealing for timing critical net routings in nanoscale VLSI designs where interconnect delay is a performance bottleneck and variation effects are increasingly remarkable. We propose Steiner network construction heuristics which can generate either tree or non-tree with different slack-wirelength tradeoff, and handle both long path and short path constraints. We also propose heuristics for simultaneous Steiner network construction and buffering, which may provide further improvement in slack and resistance to variations. Furthermore, incremental non-tree delay update techniques are developed to facilitate fast Steiner network evaluations. Extensive experiments in different scenarios show that our heuristics usually improve timing slack by hundreds of pico seconds compared to traditional approaches. When process variations are considered, our heuristics can significantly improve timing yield because of nominal slack improvement and delay variability reduction.     

The Maximum Throughput of A Wireless Multi-Hop Path

In this paper, the maximum end-to-end throughput that can be achieved on a wireless multi-hop path is investigated analytically. The problem is modeled using the conflict graph, where each link in the multi-hop path is represented uniquely by a vertex in the conflict graph and two vertices are adjacent if and only if the associated links mutually interfere. Using the conflict graph and the linear programming formulations of the problem, we analyzed the maximum end-to-end throughput of a wireless multi-hop path a) in a simple scenario where nodes are optimally placed and each node can only interfere with the transmission of its adjacent nodes along the path, and b) in a more complicated scenario where nodes are randomly placed and each node can interfere with the transmission of any number of nearby nodes along the path in both a) an error free radio environment and b) an erroneous radio environment. The maximum end-to-end throughputs for each of the above four scenarios are obtained analytically. We show that the maximum achievable end-to-end throughput is determined by the throughput of its bottleneck clique, where a clique is a maximal set of mutually adjacent vertices in the associated conflict graph. Further our analysis suggests the optimum scheduling algorithm that can be used to achieve the maximum end-to-end throughput and that it is convenient to use the (maximal) independent sets as the basic blocks for the design of scheduling algorithms. The findings in this paper lay guidelines for the design of optimum scheduling algorithms. They can be used to design computationally efficient algorithms to determine the maximum throughput of a wireless multi-hop path and to design a scheduling algorithm to achieve that throughput.     

Channel Adaptive Shortest Path Routing for Ad Hoc Networks

1　IntroductionAdhocnetworksareformedwithoutrequiringthepreexistinginfrastructureorcentralizedadminis tration ,incontrasttocellularnetworks.Asidefromtheoriginalmilitaryapplication ,ithasapplicationinpublicsafetyandcommercialareas,butadaptiveprotocolsarerequiredinorderforthemtodoso .Twoimportantcharacteristicsofacommunicationlinkinadhocnetworksareitsunreliabilityanditsvariability .Thelinksinsuchanetworkareunreli ablebecauseoffading ,interference,noise,andper hapsthefailureofthetransmittingorrec…