Cloud computing is becoming popular as the next infrastructure of computing platform. Despite the promising model and hype surrounding, security has become the major concern that people hesitate to transfer their applications to clouds. Concretely, cloud platform is under numerous attacks. As a result, it is definitely expected to establish a firewall to protect cloud from these attacks. However, setting up a centralized firewall for a whole cloud data center is infeasible from both performance and financial aspects. In this paper, we propose a decentralized cloud firewall framework for individual cloud customers. We investigate how to dynamically allocate resources to optimize resources provisioning cost, while satisfying QoS requirement specified by individual customers simultaneously. Moreover, we establish novel queuing theory based model M/Geo/1 and M/Geo/m for quantitative system analysis, where the service times follow a geometric distribution. By employing Z-transform and embedded Markov chain techniques, we obtain a closed-form expression of mean packet response time. Through extensive simulations and experiments, we conclude that an M/Geo/1 model reflects the cloud firewall real system much better than a traditional M/M/1 model. Our numerical results also indicate that we are able to set up cloud firewall with affordable cost to cloud customers.

Cloud computing is becoming popular as the next infrastructure of computing platform. However, with data and business applications outsourced to a third party, how to protect cloud data centers from numerous attacks has become a critical concern. In this paper, we propose a clusterized framework of cloud firewall, which characters performance and cost evaluation. To provide quantitative performance analysis of the cloud firewall, a novel M/Geo/1 analytical model is established. The model allows cloud defenders to extract key system measures such as request response time, and determine how many resources are needed to guarantee quality of service (QoS). Moreover, we give an insight into financial cost of the proposed cloud firewall. Finally, our analytical results are verified by simulation experiments.

Delay/disruption tolerant networking (DTN) offers a new solution to highly stressed communications in space environments. It is considered one of the most suitable technologies to be employed in space internetworking. To date, little work has been done in investigating how to achieve the best performance of DTN transmission over lossy, long-delay space channels. In this paper, we present an experimental investigation of how the throughput performance of Licklider transmission protocol (LTP)-based DTN is affected by the LTP flow control “window” size, established by the Number of Sessions (NOS) and Number of Bytes per Session (NBS) characterizing the LTP channel. The intent of the work is, in particular, to find a relationship between the window size and throughput performance of DTN in a typical lossy and long delay cislunar communications infrastructure. One major conclusion is that a bigger NOS generally results in higher throughput than a low NOS, and NBS does not affect the throughput significantly.

In this paper, we consider the neighbor discovery problem in wireless ad hoc networks with directional antennas. One key performance measure is how long it takes to discover all the neighbors given that nodes do not have priori knowledge where their neighbors are. One common impression is that algorithms using directional transmission/receive take longer time than those algorithms using omni-antennas. In this paper, we prove that this is not the case. Furthermore, most of the proposed algorithms are 1-way only, which is not suitable for networks with directional antennas. We first propose three 2-way random neighbor discovery algorithms (based on the algorithms in [Vasuden et al., 2005]), two of which may still use omni-antennas in certain stages of the algorithms and a new scan based algorithm. Then we derive analytical expressions for the average number of slots required to discover all the neighbors for the three 2-way random algorithms and for two scan based algorithms. Analytic and simulation results are presented to compare 4 of the algorithms. From the numerical results, we conclude that scan-based all-directional algorithms give the best performance among all the algorithms considered. If designed properly, all-directional algorithms can discover neighbors in less time than those algorithms using omni-directional antennas.

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Abstract There is much research activity in the emerging area of delay/disruption tolerant networks (DTN) in the past few years. DTNs pose many new challenges, and protocols designed for wired Internet or wireless mobilead hocnetworks do not work properly in DTNs. Routing is one of the key components in DTNs and the message ferry (MF) approach has been drawn a lot of attention to support routing in DTNs. Besides the underlying routing protocols, issues in transport layer are also very important and need to be addressed for DTNs. Recently, many new routing protocols, including unicast using the MF approach, inter‐region routing and multicast, have appeared in the literature. There are also a few works addressing issues in the transport layer. This paper provides an overview on recent developments including message ferrying, multicast support, inter‐region routing, and transport layer issues. It also points out some open research issues and intends to motivate new research and development in this area. Copyright © 2007 John Wiley & Sons, Ltd.

Anycast routing is very useful for many applications such as resource discovery in delay tolerant networks (DTNs). In this paper, based on a new DTN model, we first analyze the any-cast semantics for DTNs. Then we present a novel metric named EMDDA (expected multi-destination delay for anycast) and a corresponding routing algorithm for anycast routing in DTNs. Extensive simulation results show that the proposed EMDDA routing scheme can effectively improve the efficiency of anycast routing in DTNs. It outperforms another algorithm, minimum expected delay (MED) algorithm, by 11.3% on average in term of routing delays and by 19.2% in term of average max queue length.

Overlay multicast is becoming increasingly popular for multimedia delivery over Internet. The available bandwidths between sender and different receivers are generally heterogeneous. In this paper, we propose a scheme to improve the throughput of a media delivery session with heterogeneous receivers by organizing the receivers into layered data distribution meshes and sending substreams to each mesh using layered coding. Our solution utilizes alternative paths and network coding in each mesh. We first formulate the problem into a mathematical programming, whose optimal solution requires global information. We therefore present a distributed heuristic algorithm. The heuristic progressively organizes the receivers into layered meshes. Each receiver can subscribe to a proper number of meshes to maximize its throughput by fully utilizing its available bandwidth. The benefits of organizing the topology into layered mesh and using network coding are demonstrated through extensive simulations. Numerical results indicate that the average throughput of a media delivery session is significantly improved.

A number of power control algorithms have been proposed for mobile ad hoc networks. However, most of them either assume omni-directional antennas or mixture of omni-directional and directional antennas. Besides, there lack work that study the impact of power control on purely directional antenna-based protocols. In this paper, we evaluate the impact of power control on a purely directional antenna-based MAC protocol, LiSL/D MAC. Simulation results show that the proposed power control algorithm improves the system performance by 30% to 80% in terms of energy consumption while preserving network throughput and end-to-end delay.

Wireless Delay Tolerant Networks (DTNs) are intermittently connected mobile wireless networks. Some well-known assumptions of traditional networks are no longer true in DTNs, which makes routing in DTNs a challenging problem. We observe that mobile nodes in realistic wireless DTNs may always have some mobility pattern information which can be used to estimate one node's ability to deliver a specific message. This estimation can greatly enhance the routing performance in DTNs. Furthermore, we adopt an alternative way to generate redundancy using erasure coding. With a fixed overhead, the erasure coding can generate a large number of message-blocks instead of a few replications, and therefore it allows the transmission of only a portion of message to a relay. This can greatly increase the routing diversity when combined with estimation-based approaches. We have conducted extensive simulations to evaluate the performance of our scheme. The results demonstrate that our scheme outperforms previously proposed schemes.

In this paper, we first identify several challenges in designing a joint channel assignment and routing (JCAR) protocol in heterogeneous multiradio multichannel multihop wireless networks (M3WNs) using commercial hardware [e.g., IEEE 802.11 Network Interface Card (NIC)]. We then propose a novel software solution, called Layer 2.5 JCAR, which resides between the MAC layer and routing layer. JCAR jointly coordinates the channel selection on each wireless interface and the route selection among interfaces based on the traffic information measured and exchanged among the two-hop neighbors. Since interference is one of the major factors that constrain the performance in a M3WN, in this paper, we introduce an important channel cost metric (CCM) which actually reflects the interference cost and is defined as the sum of expected transmission time weighted by the channel utilization over all interfering channels (for each node). In CCM, both the interference and the diverse channel characteristics are taken into account. An expression for CCM is derived in terms of equivalent fraction of air time by explicitly taking the radio heterogeneity into consideration. Using CCM as one of the key performance measures, we propose a distributed algorithm (heuristic) that produces near-optimal JCAR solution. To evaluate the efficacy of our heuristics, we conduct extensive simulations using the network simulator NS2. To demonstrate implementation feasibility, we conducted various experiments for the proposed distributed JCAR algorithm on a multihop wireless network testbed with nine wireless nodes, each is equipped with single/multiple 802.11a/g cards. Both experimental and simulation results demonstrate the effectiveness and implementation easiness of our proposed software solution

Recent advances in information theory show that the throughput of a multicast session can be improved using network coding. In overlay networks, the available bandwidth between sender and different receivers are different. In this paper, we propose a solution to improve the throughput of an overlay multicast session with heterogeneous receivers by organizing the receivers into layered data distribution meshes and sending substreams to each mesh using layered coding. Our solutions utilize alternative paths and network coding in each mesh. We first formulate the problem into a mathematical programming, whose optimal solution requires global information. We therefore present a distributed heuristic algorithm. The heuristic progressively organizes the receivers into layered meshes. Each receiver can subscribe to a proper number of meshes to maximize its throughput by fully utilizing its available bandwidth. The benefits of organizing the topology into layered mesh and using network coding are demonstrated through extensive simulations. Numerical results indicate that the average throughput of a multicast session is significantly improved (up to 50% to 60%) with only slightly higher delay and network resource consumption

We propose a novel medium access control (MAC) algorithm using pure directional transmission and reception for mobile wireless ad hoc networks with directional antennas. Recent research results show that there are significant gains in throughput to be realized with directional transmission and reception (compared with omnidirectional) (Su Yi et al., MobiHoc, 2003), however; no specific reservation/scheduling algorithms are presented. To the best of our knowledge, all previous work assumed omnidirectional reception at certain stages of the algorithms. However, the omni-receive requirement makes the protocol vulnerable to jamming. We assume no omni-antennas or omni-directional reception capability at all. The proposed algorithm exploits the beamforming capabilities of smart antennas to tailor resource access according to the services desired for individual traffic flows while limiting interference, probability of detection and jamming in the network. Specifically, we present a TDMA-based MAC algorithm for load-dependent negotiation of slot reservations. Our new protocol offers four significant advantages: (1) it assumes directional transmission/reception; (2) it is distributed, that is, it relies on local information only; (3) it allocates slots to different links dynamically based on demand; (4) power control is easily carried out during neighbor discovery and reservation, as well as the data transmission period, with very little overhead. We believe that it is the first work on pure directional transmission and reception in ad hoc networks. The algorithm can be used in many commercial and military applications.

One important aspect of constructing an overlay network is how to exploit network locality in the underlying network. In this paper, we propose a scalable protocol for constructing an overlay network that takes account of locality of network hosts. The constructed overlay network can significantly decrease the communication cost between end-hosts. Our simulation results show that the average distance between a pair of hosts in the constructed overlay network is only about 11% of the one in a traditional, randomly connected overlay network. Furthermore, our proposed overlay considered to be more scalable than tree-based or mesh-based overlays.

Wavelength conversion has been shown as one of the key techniques to improve blocking performance in a wavelength-routed all-optical network. Given that wavelength converters nowadays remain very expensive, how to make effective use of a limited number of wavelength converters becomes an important issue. We propose sparse-partial wavelength conversion (SPWC) network architecture with the inherent flexibility that can facilitate network carriers to migrate the optical backbone to support wavelength conversion. We demonstrate that this network architecture can significantly save the number of wavelength converters, yet achieving excellent blocking performance. Theoretical and simulation results indicate that, the performance of a wavelength-routed WDM network with only 1-5%of wavelength conversion capability is very close to that with full-complete wavelength conversion capability.

There are many research interests in peer-to-peer (P2P) overlay architectures. Most widely used unstructured P2P networks rely on central directory servers or massive message flooding, clearly not scalable. Structured overlay networks based on distributed hash tables (DHT) are expected to eliminate flooding and central servers, but can require many long-haul message deliveries. An important aspect of constructing an efficient overlay network is how to exploit network locality in the underlying network. We propose a novel mechanism, mOverlay, for constructing an overlay network that takes account of the locality of network hosts. The constructed overlay network can significantly decrease the communication cost between end hosts by ensuring that a message reaches its destination with small overhead and very efficient forwarding. To construct the locality-aware overlay network, dynamic landmark technology is introduced. We present an effective locating algorithm for a new host joining the overlay network. We then present a theoretical analysis and simulation results to evaluate the network performance. Our analysis shows that the overhead of our locating algorithm is O(logN), where N is the number of overlay network hosts. Our simulation results show that the average distance between a pair of hosts in the constructed overlay network is only about 11% of the one in a traditional, randomly connected overlay network. Network design guidelines are also provided. Many large-scale network applications, such as media streaming, application-level multicasting, and media distribution, can leverage mOverlay to enhance their performance.

Recently, there are many research interests in providing efficient and scalable multimedia distribution service. However, stringent quality-of-service (QoS) requirements for media distribution, as well as dynamically changing and heterogeneous network capacity in today's best effort Internet, bring many challenges. In this paper, we introduce a novel framework for multimedia distribution service based on peer-to-peer (P2P) networks. A topology-aware overlay is proposed in which hosts self-organize into groups. End hosts within the same group have similar network conditions and can easily collaborate with each other to achieve QoS awareness. In order to improve media delivery quality and provide high service availability, we further propose two distributed heuristic replication strategies, intergroup replication and intragroup replication, based on this topology-aware overlay. Specifically, intergroup replication is aimed to improve the efficiency of media content delivery between the group where a request is issued and the group where the content is stored. Also, intragroup replication is targeted at improving the availability of the content. Extensive simulation results show that the latency in our proposed architecture is 20% less than that of the FreeNet and 50% less than that of the randomly replication system. Simulation results also show that the video quality in our system is much better than that in the other two systems. Our P2P-based approach is also distributed, scalable, cost effective, and aware of the performance.

In this paper, we propose a performance analysis model to study the reach-ability in unstructured overlay networks. Given a node's degree distribution and a network size, n, the model describes the flooding query pattern in a P2P network accurately. Also, we prove that in such an overlay network, the average distance between any two hosts is limited by O(log N). This model is simple and accurate, and therefore is a very useful tool in exploring many properties of massive overlay networks. It can be applied to P2P based content distribution networks and ad hoc wireless networks, for example.

Peer-to-peer based multimedia distribution service draws great attention in recent years. In order to improve system performance and provide high service availability, we propose a hierarchy replication strategy based on the topology-aware overlay, which can achieve the scalable and QoS-awareness. Specifically, we propose two distributed heuristic replication strategies: inter-group replication and intra-group replication, both strategies are simple and based on theoretic analysis. Simulation results show that, the latency in our proposed scheme is up to 20% less than that of the FreeNet and up to 50% less than that of the randomly replication system.

We propose a novel integrated optical network switching architecture. The proposal offers an approach to signaling for the purpose of transport on an all-optical network of optical and nonoptical legacy network traffic. In order to provide effective end-to-end control and efficient transport services, new signaling and control techniques are required. Standard organizations such as Optical Interworking Forum (OIF) and Internet Engineering Task Force have developed interface methods between client and transport networks, as well as signaling processes for resource allocation. We propose a network controller, which implements interfaces for such integration in the intermediate future, as well as provides a feasible path for the long-term objective of all optical networking. Performance and capacity issues for these systems introduce new dimensions to the existing set of networking problems, since optical paths can now be set up in real-time. There are two main contributions in this paper: (1) functional composition of a network controller, which translates legacy signaling to optical connection signaling and path establishment and (2) determining when to issue an optical connection request based on the current network conditions such as link utilization, so that the integrated optical network can operate efficiently. Analytical approximations, as well as simulation results for call blocking performance are also presented.

Existing research demonstrates that an effective routing and wavelength assignment (RWA) strategy and a proper wavelength converter placement algorithm are the two primary vehicles for improving the blocking performance of wavelength-routed network. However, these two issues have largely been investigated, separately in that the existing RWA algorithms seldom consider the presence of wavelength conversion. We argue in this paper that any RWA algorithm needs to take into account the underlying wavelength conversion for two reasons: (1) wavelength converter placement is usually done at a much earlier stage during capacity planning; and (2) one of the key advantages of an all-optical network is its reconfigurability in that the network topology can be changed through routing and wavelength assignment. We propose a weighted least-congestion routing and first-fit wavelength assignment (WLCR-FF) RWA algorithm in conjunction with a heuristic wavelength converter placement algorithm called minimum blocking probability first (MBPF) that considers both the distribution of free wavelengths and the lengths of each route jointly. Using both analysis and simulation, we carry out extensive studies to compare the performance of the proposed algorithms over a variety of topologies. The results demonstrate that the proposed WLCR-FF algorithm can achieve much better blocking performance than static routing, fixed-alternate routing and least-loaded routing algorithms, in the environment of sparse or/and full wavelength conversion.

The emerging next generation of wireless cellular networks has to provide the quality-of-service (QoS) for a variety of applications. This paper addresses bandwidth allocation for a voice and data integrated mobile wireless network. Specifically, we propose a new bandwidth allocation scheme called dual-threshold reservation (DTR) scheme, which is a natural extension from well-known guarded channel (GC) scheme used in cellular networks supporting voice traffic. The basic idea is to use two thresholds, one for reserving channels for voice handoff, while the other is used to block data traffic into the network in order to preserve the voice performance in terms of handoff dropping and call blocking probabilities. We develop an analytical model which can obtain its performance using an iterative technique. Results obtained from the analytical model are used to illustrate the system tradeoff.

Presents a heuristic algorithm for effectively assigning a limited number of wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect wavelength-selective optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offering very high aggregate capacity. Although the optical connectivity among the access station can be altered by changing the states of the various optical switches, the resulting optical connectivity pattern is constrained by the limitation imposed at the physical level. The authors also study two routing schemes, used to route requests for virtual connections. The heuristic is tested on a realistic traffic model, and the call blocking performance of new requests for virtual connections is studied through extensive simulations and compared against the blocking performance of an ideal infinite capacity centralized switch (lowest possible call blocking caused exclusively by congestion on the finite capacity user input/output links, never by the switch fabric itself). Surprisingly, the authors find that, for a wide range of parameters, the blocking performance of the lightwave network is almost the same as that of the ideal centralized switch. From these results, they conclude that the heuristic algorithm is effective and the routing scheme is efficient.>

This paper proposes scalable conflict-free media-access protocols with a novel architecture called parallel queueing for WDM optical passive star networks. The processing and hardware resource requirements are low and the control signalling demand is significantly reduced by using a small number of parallel queues in each station. A new scheme called wormhole scheduling is introduced to compensate the relatively slow laser-filter tuning speed. The protocol using wormhole scheduling decreases the overhead of tuning (thus increases the throughput) and relieves the electronic processing bottleneck. The key ideas are: (1) to associate several parallel queues with a data channel, rather that one deep queue (as in DT-WDMA) of N static queues, N is the number of stations; and (2) to schedule multiple successive packets which are destined to the same receiver at one time. An analytical model is presented and verified through simulation. Numerical results from analysis and simulation indicate that with only 5-6 parallel queues, the protocols are capable of achieving high throughput. Thus the protocols can be scaled up for networks with a large number of stations and could lead to potential implementation.>

The authors present a heuristic algorithm for effectively assigning a limited number of wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect wavelength-selective optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offering very high aggregate capacity. Although the optical connectivity among the access station can be altered by changing the states of the various optical switches, the resulting optical connectivity pattern is constrained by the limitation imposed at the physical level. They also present and study two admission control schemes, used to admit or reject requests for virtual connections. The heuristic is tested on a realistic traffic model, and the call blocking performance of new requests for virtual connections is studied through extensive simulations and compared against the blocking performance of an ideal infinite capacity centralized switch (lowest possible call blocking caused exclusively by congestion on the finite capacity user input/output links, never by the switch fabric itself). Surprisingly, they find that, for a wide range of parameters, the blocking performance of the lightwave network is almost the same as that of the ideal centralized switch. From these results, they conclude that the heuristic algorithm is effective and the admission control scheme is efficient.>

Multihop lightwave networks with hot potato routing offer the potential for significantly higher aggregate capacity as compared against minimum distance routing since each interconnecting link can be operated at a rate much higher than the electro-optic constraint forced by store-and-forward buffering. If the links can be operated at a speed sufficiently high as to offset the hot potato misrouting inefficiency, then a net capacity gain will be enjoyed. In this paper, we study such a network in which contention for an outbound link is resolved by assigning to each packet a priority based on its distance to destination and its age (number of misroutes previously suffered). An approximate analysis based on a reasonable set of assumptions is presented, queueing delay, packet loss performance, and network aggregate capacity (saturation throughout) are compared for distance-age prioritization, age-distance prioritization, and no prioritization. Results suggest that the lowest delay, lowest packet loss performance, and highest saturation throughput are offered by distance-age prioritization (priority given first to a packet closest to its destination and second to the oldest of multiple packets of the same distance to destination). The tails of the probability distribution for the number of hops taken by a representative packet are, however, shorter for age-distance routing. The capacity gain with link speed-up and hot potato routing can be quite significant compared to link speed-constrained store and forward buffering, and grows with both link speed-up factor and network size.>

A multiaccess communications channel which is shared on an integrated circuited-switched and packet-switched basis is considered. Applications include time-division multiplexing and demand-assigned/TDMA communication channels which are shared by circuit-switched services (such as isochronous voice) and packet-switched services (such as data). Frames of fixed duration are established and divided into two parts: one part is used for voice transmissions while the other part serves to accommodate packetized data traffic. These two parts are separated by a movable boundary, so that data traffic can use the frame capacity which is temporarily unoccupied by voice transmissions. An exact expression is derived for the mean packet queue-size and delay. To reduce the computational complexity involved in using this expression, simpler expressions for upper and lower bounds are derived for the mean packet queue-size and packet delay. Examples demonstrating the tightness of these numerically efficient bounds are presented. >

The performance of a direct-sequence/code-division multiple-access (DS CDMA) spreading ALOHA access protocol, which can be applied to wireless data network and personal communications services, is investigated. A Markov model is used to derive upper and lower bounds of the throughput of the underlying system. Time-driven simulation is also performed to investigate the tightness of the bounds. The results indicate that the upper bound is very tight. Numerical results also show that, unlike the conventional ALOHA system, the DS/CDMA spreading mainslotted ALOHA system provides better delay and throughput performance than the DS/CDMA spreading-slotted ALOHA system.>

The efficiency of protocols coordinating the data transmission between the transmitter and receivers in a network of stations connected using a passive star coupler, equipped with fixed transmitters and tunable receivers, and using wavelength-division multiplexing is discussed. Two reservation-based protocols with varying degrees of signaling complexity are proposed: the dynamic allocation scheme (DAS), which dynamically assigns slots on a packet-by-packet basis, and the hybrid time-division-multiplexing (TDM) scheme (HTDM), which combines the TDM and the DAS scheme and allows both preassigned and dynamic slot assignment. Analytical results are derived for the delay performance of the two schemes and compared with that of TDM. It is shown that the performance of DAS under ideal conditions is close to optimal, but its signaling costs are exorbitantly high. On the other hand, HTDM has lower signaling needs, but has higher delays when compared to DAS.>

The commenters offer a counterexample to the results presented by W. Yue (see ibid., vol.39, no.6, p.818-22, June 1991) concerning the effect of capture on multichannel slotted ALOHA. A simplified deterministic capture is assumed by Yue. Numerical results show that the actual average throughput is much higher than that obtained by Yue for the same parameters. >

The authors present an analytical approach to the performance analysis of multihop lightwave networks with hot-potato routing and multiclass traffic. Explicit closed-form expressions are derived for the hop distribution and the probability of 'don't care'. The computational complexity is thus reduced as compared to previous approaches, and priorities are readily handled. Results for two different classes of traffic are given. The probability of a packet belonging to a particular class of traffic existing on a preferred path is calculated by finding the fixed point of a scale function. The throughput and network delay as well as queuing delay of a particular class are then calculated using the expressions derived for them.>

A network with N stations connected via a passive star coupler using wavelength division multiplexing (WDM) is considered. Each station is equipped with a transmitter, transmitting at a fixed frequency, and a tunable receiver, capable of receiving frequencies over the entire transmitting spectrum. Two reservation-based protocols are proposed for a local area network (LAN) environment: the dynamic allocation scheme (DAS), which dynamically assigns slots on a packet-by-packet basis, and the hybrid TDM scheme (HTDM) which is a combination of TDM and the DAS, allowing both preassigned slot and dynamic slot assignment. Analytical results are derived for the delay performance of the two schemes and these results are compared with that of the TDM. It is shown that the performance of DAS is close to optimal when the propagation delay is zero. However, it requires a large signaling bandwidth. On the other hand, HTDM has lower signaling needs, provides lower delays when compared to TDM (particularly under nonuniform traffic conditions), and is capable of handling bursty data traffic. Thus, HTDM offers a more practical solution for implementation for LANs.>

An efficient computational procedure to calculate the queue size distribution in a finite buffer queuing system with a number of independent sources is presented. Each source is characterized by a finite state discrete-time Markov chain. An explicit expression for the queue size distribution is obtained directly. The method is based on computing the modified spectral expansion of the state distribution of the system. This representation requires evaluating the roots of the entire system characteristic function and solving a set of linear system equations. Exact results show that the cell loss probability depends only on the ratio of the buffer capacity to burst length. An approximation expression for the cell loss probability based on asymptotic analysis is also presented. Numerical results show that the approximation is accurate, especially when the system load is heavy. The effect of burst length on the cell loss probability is investigated.>

Under a TDMA (time-division multiple-access) scheme, a station shares a multiple-access communications channel by transmitting its messages during its dedicated time slots. An exact result concerning the queue-sizer and message delay analysis of TDMA systems in which a station is allocated multiple consecutive slots per frame is presented. The generating function of the system queue-size for a general independent arrival message process is obtained. Messages consist of a random number of packets, following a geometric distribution. An exact result for the generating function of the message delay for various common message arrival processes and light bounds for the mean message queue-size and delay are then derived. The results are compared to previously derived approximations. It is also proved that a slot allocation scheme which distributes station slots uniformly over the frame yields a message-delay lower bound. The results also apply to the analysis of time-shared reservation schemes.>

The Nash equilibrium point for optimum flow control in a noncooperative multiclass environment is studied. Convergence properties of synchronous and asynchronous greedy algorithms are investigated in the case where several users compete for the resources of a single queue using power as their performance criterion. A proof of the convergence of a synchronous greedy algorithm for the n users case is given, and the necessary and sufficient conditions for the convergence of asynchronous greedy algorithms are obtained. Another important contribution is the introduction to the literature and the extension of a not very widely known theorem for the convergence of Gauss-Seidel algorithms in the linear systems theory.>

A network is studied in which contention for an outbound link is resolved by assigning to each packet a priority based on its distance to destination and its age (number of misroutes previously suffered). Queueing delay, lost packet performance and network aggregate capacity (saturation throughput) are compared for distance-age prioritization, age-distance prioritization and no prioritization. Results suggest that the lower delay, lower lost packet performance, and high saturation throughputs are offered by distance prioritization. The tails of the probability distribution for the number of hops taken by a representative packet are, however, shorter for age-distance routing. Typical results show that, for a multihop shuffle network with 10240 nodes, the saturation throughput is about 40% higher for distance-age prioritization. For a smaller network with 384 nodes, the improvement falls to 25%.>

The Nash equilibrium point for optimum flow control in a noncooperative multiclass environment is studied. Convergence properties of asynchronous as well as synchronous algorithms are investigated. The convergence of a greedy algorithm for the n users case is proved, and necessary and sufficient conditions for the convergence of asynchronous algorithms are obtained. Since asynchronous algorithms do not converge for all values of the weighting factors, one must be careful in their choice. An introduction to the literature and an extension of a not very widely known theorem for the convergence of Gauss-Seidel algorithms in the linear systems theory are given.>

Article Free Access Share on Queueing analysis of a statistical multiplexer with multiple slow terminals Author: Zhensheng Zhang Center for Telecommunications Research, Columbia University, New York, NY Center for Telecommunications Research, Columbia University, New York, NYView Profile Authors Info & Claims SIGCOMM '91: Proceedings of the conference on Communications architecture & protocolsAugust 1991 Pages 81–88https://doi.org/10.1145/115992.116001Published:01 August 1991Publication History 1citation1,503DownloadsMetricsTotal Citations1Total Downloads1,503Last 12 Months14Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

A multiple-access communications channel which is shared among network stations using a circuit-switched time-division multiple-access (CS-TDMA) scheme is examined. Each station is allocated a fixed number of slots (N) during each frame. The authors carry out queue-size message delay analysis for CS-TDMA systems. They derive the generating function of the queue size and of the waiting time distribution for a discrete-time Geom/sup (x)//Geom/N queuing system. This result is used to obtain the generating function of the system size for the CS-TDMA scheme. The associated computation requires the solution of (N+1)2/sup N/ linear equations. To derive a more computationally effective procedure, tight lower and upper bounds are obtained, requiring the solution of at most 3N linear equations. The authors prove that a slot allocation scheme which distributes station slots uniformly over the frame yields a message delay lower bound. The application of the results to the analysis of demand-assigned CS-TDMA systems is also discussed.>

Consideration is given to a multiaccess communications channel which is shared on an integrated circuit-switched and packet-switched basis. Applications include time-division multiplexing and demand-assigned/TDMA (time-division multiaccess) communication channels which are shared by circuit-switched services (such as isochronous voice) and packet-switched services (such as data). Frames of fixed duration are established and divided into two parts: one part is used for voice transmissions while the other part serves to accommodate packetized data traffic. These two parts are separated by a movable boundary, so that data traffic can use the frame capacity which is temporarily unoccupied by voice transmissions. An exact expression is derived for the mean packet system size and delay. To reduce the computational complexity involved in using this expression, simpler expressions for upper and lower bounds are derived for the mean packet system size and packet delay. Examples that demonstrate the tightness of these numerically efficient bounds are presented.>