Buffered fixed routing: a routing protocol for real-time transportin grid networks

We propose a new routing protocol called buffered fixed routing (BFR) for real-time applications on grid networks. While previous routing protocols for grid networks have been designed to improve network throughput, the BFR scheme is proposed to guarantee the end-to-end packet delay and sequencing without loss by using finite buffers at each node. Thus the proposed scheme can satisfy quality-of-service (QoS) requirements of real-time applications. The BFR scheme uses the token on the row ring to provide QoS guarantees. The performance of the BFR scheme is analyzed by using the Geom/Geom/1 queueing system under uniform traffic. In the simulation, the BFR scheme shows the zero-loss, high-throughput performance with the minimum delay variation compared to other routing protocols such as store and forward routing, deflection routing and vertical routing. In addition, it has shown the smallest average delay at intermediate and heavy loads     

Mixed time-constrained and non-time-constrained communications inlocal area networks

It is well known that some time-token medium access protocols for local area networks (LANs) like the IEEE 802.4 token bus and the FDDI token ring can guarantee the medium access delay for time-constrained packets. However, a problem which has been largely overlooked is how these protocols can be made to provide a maximum throughput for nontime-constrained packets while guaranteeing the delay bound of time-constrained packets. The authors first show how the parameters of the IEEE 802.4 token bus and the FDDI token ring can be set to solve the above problem. Then, they design a new timer mechanism for the timed-token protocols which provides the highest guaranteed throughput of nontime-constrained packets among a set of medium access protocols called the token passing protocol, to which most of the existing non-contention LAN protocols belong. They present numerical examples to compare different protocols, all of which have shown the superiority of the proposed protocol to the others     

Are priorities useful in an 802.5 token ring?

The IEEE standard 802.5 token ring protocol defines eight packet priorities. The intent is that high-priority packets should be delivered prior to low-priority packets. A series of simulations shows that this expected behavior occurs when there are very few network stations, very short data packets (but still long relative to ring latency), very short token hold times, and very high network loads. In the general case, priorities did not markedly influence packet delivery time. Use of the priority system generally resulted in more overhead and longer average packet delays than when all packets were carried as a single priority. The features of the protocol operation that are the cause of this increased delay and lack of priority discrimination are described mathematically     

Contention protocols for ring networks with large bandwidth-delay products

As the bandwidth-delay product of ring networks increases, conventional access protocols, such as the gated token protocol, become less efficient. We propose overcoming this problem with contention-based access protocols. We discuss the necessary properties of any contention ring access protocol and present two specific proposals. Some simple analysis and simulation is done to determine the performance of these protocols. Our protocols are shown to have better end-to-end delay than a gated token protocol. We also simulate another contention protocol called the hybrid protocol, proposed by Bhargava, et al. It is shown that the simple protocols described in this paper have performance comparable to that of the more complex hybrid protocol on networks with high bandwidth-delay products.     

The token grid network

An overwhelming majority of local and metropolitan area network products (LANs and MANs) are based upon linear topologies such as buses and rings. Such networks are economical for high speed operation since the station interfaces are simple and require very little transit buffering. However because of their linear structure, the total throughput is restricted by the transmission rate of the media access channels. In the paper, a token grid network is introduced where media access is performed over a two-dimensional mesh. In the resulting system, each station is two-connected and has the same transmission hardware and small station latency as in a dual token ring. In the token grid however, the total system throughput may be many factors larger than that which is possible in a dual token ring. In a large √N×√N network, the uniform load capacity is approximately √N/2 times that of an N station dual token ring. In addition, the token grid can take advantage of communities-of-interest amongst the stations. It is possible to implement the system in such a way as to achieve robust operation in the presence of station and link failures     

Performance evaluation of CSMA/ID MAC protocol for IP over WDM ring networks

In this paper, a packet pre‐classification media access control protocol based on a carrier sense multiple access with idle detection (CSMA/ID) scheme is investigated for supporting IP packets over all‐optical WDM ring networks. The purpose of the protocol is to increase throughput and to decrease the packet transmission delay of IP packets over optical networks in a metropolitan area network. This protocol avoids both packet collision and packet fragmentation. In order to improve the utilization of the network, the packets transmitted from a local area network are first pre‐classified into various class queues of an access point (AP) according to their length. After checking the available space based on the wavelength received by the receivers of the AP, the packets in the queues are transmitted. An analytical model is developed to evaluate the performance of the protocol, with simulation results showing good network efficiency. The proposed network has short‐term variations that introduce unfairness conditions. This problem could be overcome by assigning a quota on individual queues to allow all queues fair access. Copyright © 2008 John Wiley & Sons, Ltd.     

The pi-persistent protocol for unidirectionalbroadcast bus networks

A protocol for multiaccess communication over unidirectional bus networks is proposed, and its performance capabilities are determined. Under this protocol, time is slotted with a slot equaling a packet's transmission time. A station with a packet to send persists in transmitting its packet in an empty slot with probability p_i until it is successful. Three criteria for fairness in selection of the p_i are modeled using Markov chains, which are solved to obtain the proper p_i that satisfy each fairness criterion. Unlike previous studies of unidirectional bus networks, stations are allowed to buffer more than one packet. The average packet delay for this protocol is bounded, and the maximum achievable throughput approaches unity with increasing buffer size. Further, the protocol provides better delay versus throughput behavior for fixed packet lengths than previous round-robin schemes, its performance is insensitive to bus characteristics, and it appears to be particularly well suited for fiber-optic network applications requiring long distances and high bandwidths. Simulation results that confirm the predicted performance are included     

WTRP - wireless token ring protocol

The wireless token ring protocol (WTRP) is a novel medium access control (MAC) protocol for wireless local area networks (WLANs). In contrast with IEEE 802.11 networks, WTRP guarantees quality of service (QoS) in terms of bounded latency and reserved bandwidth, which are critical in many real-time applications. Compared to 802.11, WTRP improves efficiency by reducing the number of retransmissions due to collisions, and it is more fair as all stations use the channel for the same amount of time. Stations take turns transmitting and give up the right to transmit after a specified amount of time. WTRP is a distributed protocol that supports many topologies, as not all stations need to be connected to each other or to a central station. WTRP is robust against single node failures, and recovers gracefully from multiple simultaneous faults. WTRP is suitable for interaccess point coordination in ITS DSRC, safety-critical vehicle-to-vehicle communications, and home networking, and provides extensions to other networks and Mobile IP.     

Performance analysis of rate-adaptive cooperative MAC based on wireless local area networks

Bi-dimensional Markov chain model based on cooperative medium access control (MAC) of wireless local area networks (WLAN) is considered to reflect system performance accurately. Two basic factors that affect the analysis results are station retry limits and non-saturated transmit probability. A uniform solution considering both factors is proposed. To prove the theoretical analysis, a cooperative MAC (CoopMAC) topology is established and the simulation model is enhanced by changing the cooperative table to the nodes' memory with more information added. Meanwhile, the three-way handshake scheme is modified and a handshake threshold is set based on the packet size. Simulation results show the performance analytical model is accurate, and the rate-adaptive cooperative MAC protocol significantly improves the network performance in terms of non-saturated system throughput and delay.     

A reservation protocol for packet voice and data integration inunidirectional bus networks

A movable boundary protocol is proposed for integrating packet voice and data in unidirectional bus networks. The head station on the bus learns the number of ready-to-transmit voice stations by reading a `request' bit in the header of the received packets and allocates the exact number of voice slots needed in each frame. The protocol guarantees that the maximum delay to transmit a voice packet will be less than the round-trip propagation delay at the head station plus twice the time needed to form the packet. The average data packet delay is evaluated via approximate analysis and simulation, for the case in which the voice-reserved slots in a frame are contiguous and for the case in which they are evenly distributed     

Metro WDM networks: performance comparison of slotted ring and AWG star networks

Both wavelength-division-multiplexing (WDM) networks with a ring architecture and WDM networks with a star architecture have been extensively studied as solutions to the ever increasing amount of traffic in the metropolitan area. Studies typically focus on either the ring or the star and significant advances have been made in the protocol design and performance optimization for the WDM ring and the WDM star, respectively. However, very little is known about the relative performance comparisons of ring and star networks. In this paper, we conduct a comprehensive comparison of a state-of-the-art WDM ring network with a state-of-the-art WDM star network. In particular, we compare time-slotted WDM ring networks (both single-fiber and dual-fiber) with tunable-transmitter and fixed-receiver (TT-FR) nodes and an arrayed-waveguide grating-based single-hop star network with tunable-transmitter and tunable-receiver (TT-TR) nodes. We evaluate mean aggregate throughput, relative packet loss, and mean delay by means of simulation for Bernoulli and self-similar traffic models for unicast traffic with uniform and hot-spot traffic matrices, as well as for multicast traffic. Our results quantify the fundamental performance characteristics of ring networks versus star networks and vice versa, as well as their respective performance limiting bottlenecks and, thus, provide guidance for directing future research efforts.     

一种有效的水声通信网络中用于半双工信道的ARQ协议

自动重传请求(ARQ)在保证通信网络可靠传输中起着关键的作用。但是，在水声通信网络中，由于水声信道的半双工以及信道的长传播时延特性，使得水声通信网络的吞叶性能受到极大的制约。本文针对水声信道长传播时延这一特点，利用扩频通信技术，将单个信道分成两个子信道；一个用于前向信道(从发送方到接收方)，另一个用于反向信道(从接收方到发送方)，从而使得对每个分组数据的响应时间大大缩短，提出了一种有效的适合于半双工特性的ARQ协议。理论分析和仿真结果表明，相对于传统的SW ARQ协议而言，该协议在水声信道下具有更优的吞吐性能。     

Performance measures and scheduling policies in ring networks

A unidirectional ring network is considered. A node may transmit at most one packet per slot to its downstream neighbor. Potentially all nodes may transmit at the same slot. The achievable performance is studied and policies are proposed for both the evacuation mode and continual operation. In the evacuation mode each node has initially an amount of packets destined for every other node of the ring, and no more packets are generated later. It is shown that the furthest destination first (FDF) policy, that gives priority to the packet with the longest way to go at each node, minimizes the time until every packet reaches its destination. Furthermore it is shown that the closest destination first (CDF) policy, that gives priority to the packet with the shortest way to go at each node, minimizes the average packet delivery time. A formula for the optimal evacuation time is obtained. The continual operation of the ring is considered then where packets are generated according to some arrival process. For any arrival sample path, the PDF maximizes the fraction of the time at which the ring is empty. The performance analysis of individual origin-destination traffic streams under FDF is facilitated based on the following. For each traffic stream, a single server priority queue is identified such that the average sojourn time of the traffic stream in the ring is equal to the aggregate transmission time plus the queueing delay of the low priority stream in the queue. Formulas for the sojourn time are obtained for iid arrivals. The performance of CDF and FIFO in continual operation is studied by simulation. It turns out that the CDF, minimum delay policy for the evacuation, has the worst performance in continual operation     

Performance Evaluation of Wireless Controller Area Network (WCAN) Using Token Frame Scheme

In this paper, a proposed new wireless protocol so-called wireless controller area network is introduced. WCAN is an adaptation of its wired cousin, controller area network protocol. The proposed WCAN uses token frame scheme in providing channel access to nodes in the system. This token frame method follows the example used in wireless token ring protocol which is a wireless network protocol that reduces the number of retransmissions as a result of collisions. This scheme based on CAN protocol allows nodes to share a common broadcast channel by taking turns in transmitting upon receiving the token frame that circulates around the network for a specified amount of time. The token frame allows nodes to access the network one at a time, giving ‘fair’ chance to all nodes instead of competing against one another. This method provides high throughput in a bounded latency environment. The proposed WCAN protocol has been developed and simulated by means of QualNet simulator. The performances of this proposed protocol are evaluated from the perspective of throughput, end-to-end delay and packet delivery ratio, and are compared against the IEEE 802.11 protocol. Simulation results show that the proposed WCAN outperforms IEEE 802.11 based protocol by 62.5 % in terms of throughput with increasing network size. Also, it shows an improvement of 6 % compared to IEEE 802.11 standard at a higher data interval rate.     

Simultaneous Burst and Burst Control Packet Transmission Protocol for Optical Burst Switching Ring Networks

In this letter, we design a collision resolution protocol for optical burst switching ring networks to avoid burst collision. We define the offset time condition for no burst transmission collision and manage the free time list of nodes for no burst reception collision. In order to improve the throughput, we use a fiber delay line, void‐filling, and void‐compression. This protocol does not require any additional procedures for bandwidth reservation such as centralized assignment of bandwidth, lightpath setup of WDM ring networks, or token capturing for the burst transmission. The simulation results show that the proposed protocol can achieve high throughput while saving 70% of wavelengths when compared to round robin with random selection, round robin with persistent, and round robin with non‐persistent with only destination delay.     

一种新型的光分组交换环网体系结构

提出了一种以波长为标签的新型全光变长分组交换环网的体系结构、网络节点的光分组数据包收发模型,以及防止光分组冲突的多令牌协议。使用多令牌协议的环网在进行光分组交换时,不需要高速的光子器件,无需使用延迟线、电中继以及解决光分组的冲突问题。通过数值仿真,分析了4节点、8节点和16节点环网巾光分组各种的时延特性以及网络的吞吐量特性。结果表明,当网络负载增大时,数据包的平均时延增大,同时网络节点的吞吐量和资源利用率也随之增大;网络节点数目越多,网络的吞吐率也越大。     

The helical window token ring

An access rule for token ring local-area networks called the helical-window token-ring protocol is introduced. It features the use of a window that limits the allowable messages a token-holding station can send. With the window, the operation of the protocol approaches that of a central single-server queuing system in the sense that messages are delivered in near first-come-first-served order on a network-wide basis. The introduction of the window also makes analysis of the networks tractable. Exact analytical formulas for the capacity and for the mean, variance, and moment-generating function of the message waiting time are derived. Numerical simulation is used to verify the results. Comparisons with continuous polling systems show that the imposition of the windowed access rule can lead to significant reductions in the delay variance (at the cost of increasing the mean system time) when the traffic is heavy and/or the message transmission time is large with respect to the walk time of the ring     

Performance comparison of two input access methods for a multicastswitch

A comparison of the performance of two input access mechanisms for multicast switching is presented. The first of these-a cyclic priority input access method-is a derivative of the ring token reservation method which eliminates the unfairness of the ordinary ring token reservation. It has the advantage of being relatively simple and easy to implement. A second approach employs a neural network to resolve output port conflict. While more difficult to implement, it has a delay-throughput performance advantage over the cyclic priority approach. The primary performance measurements are the switch throughput and the packet delay. A key assumption is that all copies of the same packet must be switched in the same slot     

Extended sliding frame R-Aloha: Medium access control (MAC) protocol for mobile networks

Proliferation of mobile communication devices necessitates a reliable and efficient medium access control (MAC) protocol. In this paper, A MAC protocol, called extended sliding frame reservation Aloha (ESFRA), based on sliding frame R-Aloha (SFRA) is proposed for network access technique. ESFRA is particularly designed to solve the mobile hidden station (MHS) problem in a mobile ad hoc network (MANET) by including relative locations of transmitting stations in the packet frame information header. The MHS problem is unique in mobile networks and occurs if a mobile station enters in a collision free zone of any ongoing communication and disturbs this communication with its transmission. In addition to the MHS problem, ESFRA simultaneously solves hidden station, exposed station, and neighborhood capture problems typically observed in wireless networks. A Markov model of ESFRA is developed and provided here to estimate throughput, delay and collision probabilities of the proposed protocol. The Markov modeling is extended to the analysis of SFRA and IEEE 802.11 to compare these competing MAC protocols with ESFRA. The analysis shows that ESFRA decreases frame transmission delay, increases throughput, and reduces collision probabilities compared to IEEE 802.11 and SFRA. ESFRA improves the network throughput 28 percent compared to that of IEEE 802.11, and 33 percent compared to that of SFRA. The improved performance is obtained at the expense of the synchronization compared to IEEE 802.11, but there is virtually no extra cost compared to SFRA.     

Fair MAC protocol for optical ring network of wavelength-shared access nodes

In this paper, a WDM optical ring consisting of access nodes with fixed transmitter-n fixed receivers (FT—FR ⁿ ) is considered. As access nodes share a wavelength channel there is trade-off between node throughput and fairness among them. In order to abbreviate the transmission unfairness and to increase the throughput, we propose p-persistent medium access control (MAC) protocol. Each node uses the carrier sense multiple access with collision avoidance (CSMA/CA) protocol to transmit packets, and decides whether to use a local empty slot with probability p when a transferred packet based on source-stripping is dropped and emptied. Numerical prediction for the proposed MAC protocol is introduced to compute the maximum node throughput under uniform traffic condition. For more detail results, we use network simulation with self-similar traffic and introduce various results. The proposed MAC protocol gives better node throughput than non-persistent protocol and shows an improved fairness factor than 1-persistent protocol. Through simulation, we also find the reasonable probability of p-persistent protocol for a given architecture.