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在三层交换机中正确及时地收发处理协议报文是交换机工作的关键。在某些情况下,协议报文会被淹没在大量的数据包中导致被丢失,从而引发相应功能模块不能正常工作。文章介绍了几种保护协议报文的方法和注意的事项,并提供了两个在测试中出现的故障案例。 相似文献
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The staggered multicast protocol for multihop spread spectrum packet radio networks is suitable for unicasting and broadcasting as well as multicasting. The common-header/transmitter-based spreading code is used for data packet transmission and the receiver-based code is used for acknowledgement packet transmission. By staggering packet transmission the protocol can significantly reduce broadcasting delay. A special addressing method and packet format are also designed to achieve collision-free acknowledgement and multicast capability. Simulation results show that the protocol provides better throughput-delay performance than the common-header/transmitter-based slotted ALOHA protocol. 相似文献
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Steven W. Boyd Jason D. Ellis Michael B. Pursley 《International Journal of Wireless Information Networks》2013,20(2):103-119
A low-complexity protocol is described and evaluated for adaptation of the modulation and coding for multicast transmission in half-duplex packet radio networks. The adaptive multicast transmission protocol is designed to compensate for changes in propagation conditions that occur from packet to packet during a session with one sender and multiple receivers. The protocol relies on simple receiver statistics to obtain the control information for adapting the modulation and coding, and it also provides scheduling to avoid collisions among acknowledgments from the receivers. The throughput provided by the protocol is compared with performance results for hypothetical ideal adaptive multicast transmission protocols that are given perfect channel state information. We illustrate the importance of adaptive modulation and channel coding in systems that employ fountain coding for packet erasure correction. 相似文献
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We propose a channel access protocol for single-hop wavelength division multiplexing (WDM) optical networks. Each node is equipped with a fixed-tuned transmitter, a tunable transmitter, a fixed-tuned receiver, and a tunable receiver. The proposed protocol alleviates the drawbacks of a previous protocol [1], e.g., invalid data transmissions that follows receiver collisions and possible acknowledgment packet collisions with header/data packets, while retaining many advantages. As a result, the network performance in terms of throughput and packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the proposed protocol, and are validated through event-driven simulation. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Through numerical results and simulation studies, we show that the proposed protocol achieves better channel utilization and incurs lower packet delays. 相似文献
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针对网络协议教学实验中存在的问题或不足,本文在分析网络协议学习难点的基础上,设计并实现了一款功能完善的网络协议辅助学习软件,总结了软件开发中的关键技术问题。该网络协议辅助学习软件能从协议层次结构及协议格式定义、协议参数编辑、报文构造、报文发送、报文接收、报文解释与统计分析、报文内容的多视角直观显示、协议之间的协同工作及会话流程等方面辅助学生的协议学习,提高了学生学习网络协议的兴趣和学习效率。 相似文献
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Improving protocol robustness in ad hoc networks through cooperative packet caching and shortest multipath routing 总被引:1,自引:0,他引:1
A mobile ad hoc network is an autonomous system of infrastructure-less, multihop, wireless mobile nodes. Reactive routing protocols perform well in this environment due to their ability to cope quickly against topological changes. This paper proposes a new routing protocol named CHAMP (caching and multiple path) routing protocol. CHAMP uses cooperative packet caching and shortest multipath routing to reduce packet loss due to frequent route failures. We show through extensive simulation results that these two techniques yield significant improvement in terms of packet delivery, end-to-end delay and routing overhead. We also show that existing protocol optimizations employed to reduce packet loss due to frequent route failures, namely local repair in AODV and packet salvaging in DSR, are not effective at high mobility rates and high network traffic. 相似文献
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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 相似文献
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In this paper, we present a diagonal-intersection-based routing (DIR) protocol for vehicular ad hoc networks. The DIR protocol
constructs a series of diagonal intersections between the source and destination vehicles. The DIR protocol is a geographic
routing protocol. Based on the geographic routing protocol, source vehicle geographically forwards data packet toward the
first diagonal intersection, second diagonal intersection, and so on, until the last diagonal intersection, and finally geographically
reach to the destination vehicle. For given a pair of neighboring diagonal intersections, two or more disjoint sub-paths exist
between them. The novel property of DIR protocol is the auto-adjustability, while the auto-adjustability is achieved that
one sub-path with low data packet delay, between two neighboring diagonal intersections, is dynamically selected to forward
data packets. To reduce the data packet delay, the route is automatically re-routed by the selected sub-path with lowest delay.
The proposed DIR protocol allows the mobile source and destination vehicles in the urban VANETs. Experimental results show
that the DIR protocol outperforms existing solutions in terms of packet delivery ratio, data packet delay, and throughput. 相似文献
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The issues that are specific to heterogeneous networks are addressed. Some background on both the current ARPA internet model and high-speed packet switching is provided. This discussion includes: the internet components; the internet protocol hierarchy, popularly known as the transmission control protocol/internet protocol (TCP/IP) protocol suite; and the internet strengths and weaknesses. The major elements of an extended internet model that allows internetworking of new high-speed packet networks with a wide range of other networks, including current data networks and national telephone networks, are outlined. Some end-to-end and host interface issues are examined 相似文献
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Michael B. Pursley Harlan B. Russell Jeffrey S. Wysocarski 《International Journal of Wireless Information Networks》2004,11(3):147-159
The use of adaptive-transmission protocols in wireless, store-and-forward, packet communication networks may result in large differences in the energy requirements of the alternative paths that are available to the routing protocol. Routing metrics can provide quantitative measures of the quality and energy efficiency of the paths from the source to the destination. Such measures are required if the routing protocol is to take advantage of the potential energy savings that are made possible by an adaptive-transmission protocol. An energy-efficient protocol suite for routing and adaptive transmission in frequency-hop wireless networks is described and evaluated, several routing metrics are compared, and tradeoffs among energy efficiency, delay, and packet success probability are investigated. 相似文献
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System Level Design for Clustered Wireless Sensor Networks 总被引:1,自引:0,他引:1
Bonivento A. Fischione C. Necchi L. Pianegiani F. Sangiovanni-Vincentelli A. 《Industrial Informatics, IEEE Transactions on》2007,3(3):202-214
We present a system level design methodology for clustered wireless sensor networks based on a semi-random communication protocol called SERAN, a mathematical model that allows to optimize the protocol parameters, and a network initialization and maintenance procedure. SERAN is a two-layer (routing and MAC) protocol. At both layers, SERAN combines a randomized and a deterministic approach. While the randomized component provides robustness over unreliable channels, the deterministic component avoids an explosion of packet collisions and allows our protocol to scale with network size. The combined result is a high reliability and major energy savings when dense clusters are used. Our solution is based on a mathematical model that characterizes performance accurately without resorting to extensive simulations. Thanks to this model, the user needs only to specify the application requirements in terms of end-to-end packet delay and packet loss probability, select the intended hardware platform, and the protocol parameters are set automatically to satisfy latency requirements and optimize for energy consumption. 相似文献
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Tsan-Pin Wang Chien-Chao Tseng 《Electronics letters》1997,33(10):841-842
The RAMA (resource auction multiple access) protocol and its variations use a collision resolution protocol based on subscriber IDs to allocate available communication resources. However, these protocols suffer from unfairness or high packet dropping probability. The authors propose and analyse a novel deterministic packet access protocol, Q-RAMA, to improve the quality of service in PCS networks. Simulation results show that Q-RAMA has the lowest packet dropping probability and better overall performance 相似文献
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介质访问控制协议(Medium Access Control , MAC)是水声通信网络中的一种关键技术。与陆地无线通信系统使用无线电波有所不同,水声通信网络依靠水声进行通信。水声通信网络中的MAC协议设计面临许多挑战面,如:传播延迟大、带宽窄、电池不易更换或充电、节点发射功率受限等。因此,陆地无线通信系统的各MAC协议不能直接应用到水声通信网络。本文提出了一种适用于水声通信网络的MACA(MACA-C)协议,该协议主要将传输数据包和控制包结合使用,在每轮握手的过程中,该协议通过发送列的首数据包和RTS控制包来改善信道利用率。仿真结果也表明MACA-C能够达到较高的和稳定的吞吐量性能,同时在保持低碰撞率的前提下增加信道利用率。 相似文献
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Hara S. Ogino A. Araki M. Okada M. Morinaga N. 《Vehicular Technology, IEEE Transactions on》1996,45(3):561-569
In a noncellular or large cell-size mobile radio communication system, log-normal shadowing as well as Rayleigh fading becomes the predominant source of system degradation. This paper proposes an efficient stop and wait automatic repeat request (SAW-ARQ) protocol with adaptive packet length to provide reliable mobile data packet transmission. The adaptive SAW-ARQ protocol controls the transmitting packet length according to the time-varying channel condition estimated with the number of ACK (acknowledgment packet) and NACK (negative-acknowledgment packet). Computer simulation results show that the proposed protocol can achieve high throughput and reduce the number of retransmission effectively for slow and fast Rayleigh fading/log-normal shadowing conditions 相似文献
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本文讨论了一种用于分组话音/数据综合的混合多址协议,该协议是固定分配与随机访问的混合,并且赋予话音分组优先传输权,从而保证了无重传话音分组有较小的丢失概率。本文进行了详细的理论分析,并得出了性能比较特性,所得结果认为这是一个兼顾话音/数据综合的较好协议,且具有一定的灵活性。 相似文献