An X.25-compatible protocol for packet voice communications

Developments in packet-switched networks have generated interest in how to integrate voice and data traffic in such networks. The paper deals with a proposed communications protocol for voice transmission within X.25 packet-switched networks. Basic protocol procedures for handling voice communications are examined, and possible formats for the identified types of voice frame and packet fitting for current CCITT standards governing packet data communications are presented.     

The HDLC/VS protocol for satellite communications

The HDLC protocol has proven to be unsuitable for satellite communications where the propagation delay is very large. The paper describes a modification of the HDLC protocol, based on the virtual subchannel concept, that is more suitable for satellite communications. The satellite link is organized into several sub-channels, each operating under the standard HDLC protocol. The performance of this modified protocil is examined, using simulation techniques.     

Protocol implementation for Universe

The communications protocols used on the Universe network and the implementor's experiences with them are described. By examining ‘lightweight’ and ‘heavyweight’ protocols, the paper examines the problems of protocols for mixed networks.     

Systems programming for data communications on minicomputers

This paper examines some of the special considerations which apply to the development of such software for minicomputers. These are treated under the following general categories:

• loading and throughput
• the external interfaces of the system software
• the internal structure of the system software
• developing the software

.     

SHAPA: an interactive software environment for protocol analysis

This paper briefly reviews work on verbal report and describes SHAPA, an interactive program for performing both verbal and non-verbal protocol analysis. To a certain extent, SHAPA is to protocol data what a spreadsheet program is to numerical data or what a word processor is to text it is intelligent about the sorts of things a researcher might want to do with verbal or non-verbal protocols, while being blind to particular domains, contexts, or theories. It has been developed with the idea of affording the researcher the closest possible degree of engagement with protocol data. The researcher can configure SHAPA to encode protocols using a wide variety of theoretical frameworks or vocabularies. SHAPA allows protocol analysis to be performed at any level of analysis, and it supplies many tools for data aggregation, manipulation and analysis. Some of these tools have been imported from a tradition of work on non-verbal protocol analysis that has developed very strong analytical tools. The output generated by SHAPA can be used alone or in combination with other performance variables to get a rich picture of the influences on sequences of verbal or non-verbal behaviour.     

多跳无线移动Ad Hoc网络路由协议的研究分析

无线移动Ad Hoe网络(MANET)作为可移动分布式多跳无线网络，没有预先确定的网络拓扑或网络基础设施以及集中控制．为了在如此的网络中促进通信，路由协议主要用于在节点之间发现路径．Ad Hoe网络路由协议的主要目的是网络拓扑的动态变化、任意两个节点之间建立一个使得通信总费用和带宽消费最少的正确和有效的通信路径．描述了设计移动Ad Hoe网络路由协议所面临的问题以及对它们的评价，详细比较了七种典型无线移动AdHoe网络路由协议的特性和功能，即DSDV，CGSR，WRP，AODV，DSR，TORA和ABR，为进一步的研究提出了新的课题．     

多跳Ad Hoc网络基于路由协议的拥塞控制

为解决Ad Hoc网络的DSR路由协议在通信过程中存在拥塞问题,提出了改进DSR路由协议的思想,即联合“最短路径”和节点发送接收数据包时的“传输状态”来避免拥塞。仿真结果表明,改进后的路由协议有效地减少了发生拥塞的几率,从而提高了无线多跳Ad Hoc网络环境下Web通信的性能。     

A wireless sensor networks MAC protocol for real-time applications

Wireless sensor networks (WSN) are designed for data gathering and processing, with particular requirements: low hardware complexity, low energy consumption, special traffic pattern support, scalability, and in some cases, real-time operation. In this paper we present the virtual TDMA for sensors (VTS) MAC protocol, which intends to support the previous features, focusing particularly on real-time operation. VTS adaptively creates a TDMA arrangement with a number of timeslots equal to the actual number of nodes in range. Thus, VTS achieves an optimal throughput performance compared to TDMA protocols with fixed size of frame. The frame is set up and maintained by a distributed procedure, which allows sensors to asynchronously join and leave the frame. In addition, duty cycle is increased or decreased in order to keep latency constant below a given deadline. Therefore, a major advantage of VTS is that it guarantees a bounded latency, which allows soft real-time applications.

浅谈计算机网络与数据通信的发展

计算机网络与数据通信,给人们的生产生活提供了极多的便利和帮助;已成为信息技术和电信技术的主要发展方向之一。本文简单回顾了计算机网络与数据通信发展的历史,着重分析了其现状,并展望了未来的发展趋势。     

一种基于水声信道的无线传感器网络路由协议

以无线传感器网络的水下应用所面对的挑战为背景,针对水声信道的传输特点,在最小代价算法和目的节点序列距离矢量DSDV(Destination-Sequenced Distance-Vector)路由协议的基础上,提出了一种均衡节点能耗的路由协议算法.该协议按照最小能量代价建立多跳路由表,从而在数据传送时能够均衡各节点的能量消耗,达到延长网络生命周期的目的.仿真结果表明,相对于DSDV协议,本文提出的协议能够实现能量均衡,有效的延长网络生存周期.     

Design and implementation of a QoS-aware MAC protocol for Wireless Multimedia Sensor Networks

Wireless Multimedia Sensor Networks (WMSNs) have entered the class of Wireless Sensor Networks (WSNs) to meet the multimedia requirements of new emerging applications, such as surveillance and telepresence. Combining the traditional scalar sensors used in WSN nodes with tiny cameras and microphones, WMSNs commonly carry heterogeneous traffic with different Quality of Service (QoS) requirements. In order to deliver heterogeneous traffic with different requirements in highly resource constrained sensor networks, QoS provisioning and service differentiation become unavoidable. In this paper first we discuss the QoS-provisioning in sensor networks and evaluate the efficiency of existing QoS-aware MAC protocols. As a result of this evaluation, next we design and implement a QoS-aware MAC protocol for WMSNs, Diff-MAC, which integrates different methods to meet the requirements of QoS provisioning to deliver heterogeneous traffic and provides a fair all-in-one QoS-aware MAC protocol. Diff-MAC aims to increase the utilization of the channel with effective service differentiation mechanisms while providing fair and fast delivery of the data. Performance evaluation results of Diff-MAC, obtained through extensive simulations, show significant improvements, in terms of latency, data delivery and energy efficiency, compared to two other existing protocols. Implementation of Diff-MAC on Imote2 platform also reveals that the protocol with moderate complexity can be easily implemented on the resource constrained motes.     

A practical study of semi-automatic OSI protocol implementation

Communication protocols form a language which can be recognized by extended finite automata, and compiler generating tools can help with its implementation. This paper presents a project for implementing the ISO OSI layers which are most relevant to LANs. Taking advantage of modular and repetitive OSI architecture, a layer implementation model is proposed, introducing sharp distinctions between protocol layer-dependent and independent modules, so that the implementation effort can be largely reduced. It is also shown that layer-dependent modules can be generated automatically by using software tools developed for compiler construction. It is assumed that the protocols to be implemented have already been verified and validated in their abstract forms using other techniques, since these aspects are not covered by the method proposed. Measures of program sizes and execution speeds obtained following the approach proposed are reported; they show that most of the layer code can be produced by automatic tools and the overall software complexity enables the OSI architecture to be implemented for single-board microcomputers.     

Performance of stop-and-wait protocols over high-delay links

The performance of stop-and-wait protocols over links with high propagation delay such as satellite links is discussed. Primary focus is placed on situations where a large block size is employed to compensate for the loss of throughput caused by the large propagation delay. Possible loss in data intergrity due to undetected errors is investigated. The results show that in most environments, acceptably high throughput can be obtained without sacrificing data integrity.     

.应用于中等负载无线传感器网络的节能型MAC协议

基于网络负载的大小,提出了适用于中等负载的无线传感器网络的节能MAC协议——EC-MAC协议。该协议引入概率p,采用TDMA方式和减少节点的空闲侦听时间来节能,提高了信道的利用率,延长了网络的生命周期。仿真结果表明,该协议在节省能量方面要优于传统TDMA和BMA协议。     

Analysing a stream authentication protocol using model checking

In this paper, we consider how one can analyse a stream authentication protocol using model checking techniques. In particular, we will be focusing on the Timed Efficient Stream Loss-tolerant Authentication Protocol, TESLA. This protocol differs from the standard class of authentication protocols previously analysed using model checking techniques in the following interesting way: an unbounded stream of messages is broadcast by a sender, making use of an unbounded stream of keys; the authentication of the n-th message in the stream is achieved on receipt of the n+1-th message. We show that, despite the infinite nature of the protocol, it is possible to build a finite model that correctly captures its behaviour.     

Security mechanisms in a transport layer protocol

This paper describes how the error detection and recovery mechanisms of the proposed National Bureau of Standards (NBS) transport layer protocol can be easily extended to provide secure transmission of information. The security mechanisms are based on the Data Encryption Standard (DES) of the NBS. Two distinct security architectures are described. In the first, the DES hardware is a peripheral I/O device of the computer in which the transport layer resides. In the other, encryption is performed by a hardware device located in the data path between the transport layer and the network layer. The paper argues that, in the long run, the transport layer should be implemented in a front end computer equipped with a DES peripheral. This isolates it from (possibly untrustworthy) host software, and greatly simplifies the job of certifying its correct behavior.     

计算机网络与数据通信的发展探究

信息技术的发展推动了计算机网络与数据通信的飞速发展，随着许多新技术和新型网络的研发，使得网络和人们的生活更加贴近。本文在探讨计算机网络与数据通信发展现状的基础上，为下一步的发展趋势指明了方向。     

Open systems interconnection — the teletex-based session protocol: Part 1

Two draft proposals for an international standard for the teletex-based session protocol have now been considered by the ISO. The ECMA 75 protocol has been found to be relatively complex as a result of ECMA having to sort out some weak points within the protocol. S.62, proposed by the CCITT, is quite suitable for the kernel of the session service, but not for the entire service. The paper suggests possible developments towards an international standard, and discusses the specification of the BAS subset. It then examines the services available, and how they operate. A proposal for a standard for service conventions is presented, along with a summary of the parameters of the service elements.     

Open systems interconnection — the teletex-based session protocol: Part 2

The development of an international standard for the teletex-based session protocol has involved combining the best points of two draft proposals, ECMA 75 and S.62. Recently, the ISO has completed a specification comprising three subsets: the ISO/ECMA subset, the ISO/CCITT subset and the null functionality subset. The paper discusses the development of the standard, lays out the specification and describes the operation of each of the protocol phases. Three appendices describe the conformance problem and the BAS subset, protocol machines and the interworking problem.     

A survey on routing techniques in underwater wireless sensor networks

Underwater Wireless Sensor Networks (UWSNs) are finding different applications for offshore exploration and ocean monitoring. In most of these applications, the network consists of significant number of sensor nodes deployed at different depths throughout the area of interest. The sensor nodes located at the sea bed cannot communicate directly with the nodes near the surface level; they require multi-hop communication assisted by appropriate routing scheme. However, this appropriateness depends not only on network resources and application requirements but also on environmental constraints. All these factors provide a platform where a resource-aware routing strategy plays a vital role to fulfill the different application requirements with dynamic environmental conditions. Realizing the fact, significant attention has been given to construct a reliable scheme, and many routing protocols have been proposed in order to provide an efficient route discovery between the sources and the sink. In this paper, we present a review and comparison of different algorithms, proposed recently in order to fulfill this requirement. The main purpose of this study is to address the issues like data forwarding, deployment and localization in UWSNs under different conditions. Later on, all of these are classified into different groups according to their characteristics and functionalities.