Group replica caching scheme for optical grid networks

This paper proposes a cache replacement scheme named group replica caching for optical grid networks. In optical grid networks, data files for job execution are replicated at multiple servers in order to distribute loads. Clients download these files via lightpaths and store them as necessary. File downloading is blocked when the corresponding lightpath cannot be established. The blocking probability of file downloading depends on location of files. The case where a file is stored in a client is ideal because blocking of lightpath establishments does not occur. However, the storage size of the client is limited. In order to efficiently use storage resources of clients, our proposed scheme focuses on the fact that clients can download files stored in surrounding servers with low blocking probability. The proposed scheme regards a group of storages of a client and its surrounding servers as one storage. In particular, they preferentially store different files. By doing so, the probability that a file is stored at the client or its surrounding servers increases. Through simulation experiments, we show that the proposed scheme improves the blocking probability of file downloading efficiently.     

Performance of split routing algorithm for three-stage multicastnetworks

This paper studies three-stage Clos (1953) switching networks for multicast communications in terms of their blocking probabilities on a random traffic model. Even though the lack of multicast capability in input-stage switches requires a prohibitively large number of middle switches to provide compatible requests with nonblocking paths, the probabilistic model gives an observation that the blocking probability decreases drastically and then approaches zero as the number of middle switches is far less than the theoretical bound. The S-shaped curves of blocking probability versus degree of fanout indicate that high fanout requests are mostly blocked at some given reference network utilization. A split routing algorithm and its blocking probability are introduced to enhance the routability of the high fanout requests. We also corroborate the analytic model by performing network simulations based on a random request generator and a random routing strategy     

Fault tolerance design for large-scale optical switches

In this paper, we present an enhanced fault tolerance in large-scale optical switches through innovations in architecture and control logic design. A large-scale switch is constructed from a network of 2×2 optical switch elements (SEs). Classic switch network architectures, such as the Benes, are not designed with fault tolerance in mind. There are three major contributions in this paper: (1) we developed an analytical method, referred to as the probability accumulation method, to calculate the average connection blocking probability in a faulty switch network; (2) we provided a failure-aware routing algorithm to effectively circumvent connections from defected SEs in a dilated Benes switch; and (3) we improved the connectivity pattern of the Benes network to further reduce the blocking probability, especially when the SE failure rate is low.     

Design of node configuration for all-optical multi-fiber networks

It is cost-effective to install multiple fibers in each link of an all-optical network, because the cost of fibers is relatively low compared with the installation cost. The resulting network can provide a large capacity for good quality of service, future growth, and fault tolerance. If a node has more incoming/outgoing fibers, it requires larger optical switches. Using the current photonic technology, it is difficult to realize large optical switches. Even if they can be realized, they are expensive. To overcome this problem, we design a node configuration for all-optical networks. We exploit the flexibility that, to establish a lightpath across a node, we can select any one of the available channels in the incoming link and any one of the available channels in the outgoing link. As a result, the proposed node configuration requires significantly smaller optical switches while it can result in nearly the same blocking probability as the existing one. We demonstrate that a good network design is to adopt the proposed node configuration and slightly more fibers in each link, so that the network requires small optical switches while it has a small blocking probability     

The Effect of Idle Server First Random Routing on the Behavior of a Finite Queue

This paper studies the effect of routing on the behavior of a finite queue which accepts batch Poisson inputs and receives service from multiple synchronous servers. Upon the arrival of a group of customers idle or pseudoidle servers will be considered first in routing decisions. Otherwise routing will be determined randomly in accordance with a preset probability distribution. Results obtained include state probability, blocking probability, delay, and throughput. Validity of analysis has been verified by computer simulations. These results can he used in evaluating the performance of a computer communication network.     

Calculation of Some Functions Arising in Problems of Queueing and Communications Traffic

Useful formulas are developed for the iterative calculation of the inverse of blocking probability for Erlang loss and Erlang delay systems, and for the determination of offered traffic and blocking probability for Erlang loss systems when the carried traffic and number of servers are given. These formulas which arise in many problems of queueing and communications traffic can be easily programmed. In tests they gave rapid convergence to high accuracy over a broad range of parameter values much greater than the range of usual display.     

To Burst or Circuit Switch?

We develop, analyze and then numerically compare performance models of a fast-adapting and centrally controlled form of optical circuit switching (OCS) with a conservative form of optical burst switching (OBS). For the first time, we consider a unified model comprising both: edge buffers at which arriving packets are aggregated and enqueued according to a vacation-type service discipline with nondeterministic set-up times, together with a core network comprising switches arbitrarily interconnected via fibers to allow transmission of packets from an edge buffer to their desired egress point through use of a dynamic signaling process to establish a lightpath, and in the case of OCS, also acknowledge its establishment. As such, edge buffers dynamically issue requests for wavelength capacity via a two or one-way reservation signaling process. Previously analyzed models of OCS and OBS have either been for a stand-alone edge buffer or a core network without edge buffering. We compare OCS with OBS in terms of packet blocking probability due to edge buffer overflow and blocking at switches in the case of OBS; mean packet queueing delay at edge buffers; and, wavelength capacity utilization. Also for the first time, we derive the exact blocking probability for a multi-hop stand-alone OBS route, assuming Kleinrock's independence, which is not simply a matter of summing the stationary distribution of an appropriate Markov process over all blocking states, as shown to be the case for an OCS route.      

Optimal video placement scheme for batching VOD services

Advances in broadband technology are generating an increasing demand for video-on-demand (VOD) applications. In this paper, an optimal video placement scheme is proposed for a batching VOD system with multiple servers. Given a specified requirement of the blocking probability, an optimal batching interval is derived and the corresponding file placement is obtained by hybrid genetic algorithm. It is demonstrated that the specified requirement on blocking probability is satisfied, while both batching interval and server capacity usage are minimized simultaneously.     

DServ‐LB: Dynamic server load balancing algorithm

In recent years, web services have been largely accessed by the customer, and it increases the network traffic on the internet. To provide the services for the large number of customer, dynamic clustering concept has been implemented that provides the ability to add or remove the servers on demand. But managing and processing the large set of traffic are very complicated. Load balancing technic helps to resolve the problems of network traffic and give efficient network management. In this paper, we proposed a dynamic server load balancing algorithm (DServ‐LB) using OpenFlow switches in software‐defined networking. The OpenFlow switches support the dynamic programmability. Also, we used the sFlow protocol, which is used to monitor the servers resource information periodically and the controller. Based on the server resource availability, the controller installs forwarding rules in the OpenFlow switches. For implementation, we used Mininet for network emulation, POX controller, and Docker container as Mininet hosts. The result shows that the proposed DServ‐LB improves the overall network performance and efficiently utilizes the server resources if compared with existing load balancing algorithms.     

Layered switch architectures for high-capacity optical transportnetworks

We propose and analyze layered switch architectures that possess high design flexibility, greatly reduced switch size, and high expandability. The improvement in loss and crosstalk due to the reduced switch size is also discussed. Theoretical models have been developed to compute the network blocking probability using these architectures. Low blocking probability and high network utilization are achieved because of the capability of communication between layers in adjacent switches. The results show that the proposed layered switch architectures are very attractive for high-capacity optical transport networks     

The performance of a link with multipriority traffic

This letter discusses the performance of a link carrying calls of preemptive priorities. General κ-dimensional steady-state balance equations are deduced and the computational complexity of two solution methods are compared through an example of three priorities. The performance of the link is studied through two conventional metrics for blocking probabilities and preempting probabilities. The “peaking” phenomenon of the preempting line discussed can be used in the design of switches and networks. The coincidence of the preempting probability line with the blocking probability line, displayed in the discussion of numerical results, suggests that better metrics for preemptive performance must be found     

Multicast routing strategies for zoned VP-based ATM networks

In ATM networks, the concept of virtual path (VP) greatly simplifies cell processing in switches. The virtual channel connection (VCC) can be more quickly and efficiently established by good strategies of resource management. The method of constructing virtual path and the strategies of managing and allocating resources greatly affect the performance of the system operation. We propose a new architecture and the corresponding methods of constructing virtual paths; various methods and strategies, such as bandwidth control, rerouting, resource management, and fault recovery, are studied (Lee and Shie 2000). This paper focuses on multicast routing and analyzes some algorithms for this model. Simulation results show the good performance in bandwidth utilization, blocking probability, and loss probability     

一种VOD系统的分析模型

对全连网络的分布式视频点播系统进行了性能分析，提出了一种VOD系统的分析模型，可以利用这一模型计算视频请球发生拥塞的概率以及网络的带宽要求，同时还可以得到在通信和存储费用两者之间的一个折衷方案。     

An Analysis of Blocking Switches Using Error Control Codes

We study the relationship between the degree of blocking and the amount of resource speedup necessary for blocking switches to possess the capabilities of nonblocking switches. We construct an analogy between switch configurations and the codewords of certain error control codes for which we use space covering ideas to derive relations between speedup and number of switch configurations. To derive the necessary speedup for nonblocking, we use two sphere packing bounds: the Hamming bound and the Gilbert-Varshamov bound. To construct nonblocking switches with a given speedup we use maximum distance separable codes. We consider both multicast and point to point scenarios.     

Multicast contention resolution with single-cycle windowing usingcontent addressable FIFO's

Asynchronous transfer mode (ATM) has been designated as the switching environment for future broadband integrated services digital networks (BISDN) networks and services. Although input-buffered space switches are more economical and simpler to implement than output-buffered space switches, they suffer from external blocking because of destination port contention. We review contention resolution methods used to avoid external blocking, and choose a solution based on ring reservation, resulting in an elegant and efficient mechanism requiring only nearest-neighbor communications. In addition to external blocking, space switches suffer from head-of-line (HOL) blocking, and our technique alleviates HOL blocking without arbitration time overhead. This method makes use of a novel content addressable first in/first out (CAFIFO) to achieve single-cycle windowing, and the CAFIFO design and operation are described in detail. High multicast throughput is achieved by employing call-splitting. Multiple latency priorities can also be supported. Simulation results, for both unicast and multicast switching, and both random and bursty traffic, highlight the versatility and excellent performance of the CAFIFO-based switch     

The Effect of Choosing the Switches for Rearrangements in Switching Networks

Known rearrangement algorithms proposed by Slepian and Paull (method 1) involve two middle switches of the three-stage Clos network. These switches are chosen arbitrarily. However, the middle switches selection rules affect the rearrangement process. In this paper four methods for choosing the switches were studied. Simulation results and analysis have shown that the allocation of the least used switches can decrease the volume of computation required for rearrangements. In the case of limited rearrangement, this method improves the blocking performance of a network.     

Blocking and nonblocking multirate Clos switching networks

This paper investigates in detail the blocking and nonblocking behavior of multirate Clos switching networks at the connection/virtual connection level. The results are applicable to multirate circuit and fast-packet switching systems. Necessary and sufficient nonblocking conditions are derived analytically. Based on the results, an optimal bandwidth partitioning scheme is proposed to reduce switch complexity while maintaining the nonblocking property. The blocking behavior of blocking switches supporting multicast connections is investigated by means of simulation. We propose a novel simulation model that filters out external blocking events without distorting the bandwidth and fanout (for multicasting) distributions of connection requests. In this way, the internal blocking statistics that truly reflect the switch performance can be gathered and studied. Among many simulation results, we have shown that for point-to-multipoint connections, a heuristic routing policy that attempts to build a narrow multicast tree can have relatively low blocking probabilities compared with other routing policies. In addition, when small blocking probability can be tolerated, our results indicate that situations with many large-fanout connection requests do not necessarily require a switch architecture of higher complexity compared to that with only point-to-point requests     

Circular sequential k-out-of-n congestion system

A circular sequential k-out-of-n congestion (CSknC) model is presented. This model finds use in reliable systems to prevent single-point failure, such as (k,n) secret key sharing systems. The model assumes that each of the n servers has a known congestion probability. These n servers are arranged in a circle, and are connected sequentially. A server is connected successfully if it is not congested. Previously connected servers are blocked from reconnecting. Congested servers have to be reconnected until k servers are connected successfully. We present the recursive, and marginal formulas for the probability of success, as well as the average number of connection attempts needed with k successfully connected servers. The optimal arrangement of servers is specified to minimize the average number of connection attempts. These formulas can be used to rearrange the servers adaptively when the initial congestion probabilities are not known. Compared to the circular CknG systems, the CSknC systems are shown to have a higher success probability, and require less connection attempts with k successfully connected servers.     

Preventing internal and external conflicts in an input buffering reverse baseline ATM switch

When two or more packets that are destined to the same output of an ATM switch arrive at different inputs, buffers at inputs or outputs are used to queue all but one of these packets so that external conflict is prevented. Although input buffering ATM switches are more economical and simpler than output buffering ATM switches, significant loss of throughput can occur in input buffering ATM switches due to head‐of‐line (HOL) blocking when first‐in–first‐out (FIFO) queueing is employed. In order to avoid both external conflict and alleviate HOL blocking in non‐blocking ATM switches, some window‐based contention resolution algorithms were proposed in the literature. In this paper, we propose a window‐based contention resolution algorithm for a blocking ATM switch based on reverse baseline network with content addressable FIFO (CAFIFO) input buffers. The proposed algorithm prevents not only external conflicts but also internal conflicts, in addition to alleviating HOL blocking. This algorithm was obtained by adapting the ring reservation algorithm used on non‐blocking ATM switches to a reverse baseline network. The fact that a non‐blocking network is replaced by a log₂ N‐stage reverse baseline network yields a significant economy in implementation. We have conducted extensive simulations to evaluate the performance of reverse baseline network using the proposed window‐based contention resolution algorithm. Simulation results show that the throughput of reverse baseline network can be as good as the throughput of non‐blocking switches if the window depth of input buffers is made sufficiently large. Copyright © 2000 John Wiley & Sons, Ltd.     

A New Method for Blocking Probability Evaluation in OBS/OPS Networks With Deflection Routing

In this paper, we present a new method for the estimation of blocking probabilities in bufferless optical burst or packet switched networks. In such networks, deflection routing is used to reduce blocking probability. However, it requires certain wastage due to trunk reservation that must be used to avoid instability. We provide a wide range of simulation and numerical results to validate our new approximation method and demonstrate various effects on blocking probability and utilization, such as network size, trunk size, the maximal number of allowable deflections, and burst/packet length.