The evolving art of packet switching

Rapid developments in computer and information technology continue to expose new requirements for switched data services, e.g. teletext, electronic funds transfer, electronic mail. The features of packet switching make it attractive for many of these new services, and many countries, including the UK, now operate or plan to introduce public packet-switched data networks. But packet switching is a relatively new art, particularly in the realm of public-switched networks, and is itself developing rapidly, driven both by the increasing demand for switched data services and by advances in semiconductor technology. It tends therefore to be the preserve of a relatively small band of specialists. This paper reviews the principles, origins and evolution of packet switching, with particular reference to public-switched networks. The picture emerges of well laid foundations and the prospect of rapid expansion in public packet-switched networks throughout the world. The development of large switches, such as those being developed at BTRL, will play an important part in this.     

Photonic fast packet switching

Several approaches to photonic fast packet switching systems are presented. The wavelength-, time-, code-, and space-division approaches, including free-space photonic fast packet switching, are discussed. These approaches to photonic fast packet switching systems show that the research in this area is still in its infancy. Among various solutions, those based on a wavelength-division transport network and an electronic controller are most mature     

The bypass queue in fast packet switching

The telecommunications networks of the future are likely to be packet switched networks consisting of wide bandwidth optical fiber transmission media, and large, highly parallel, self-routing switches. Recent considerations of switch architectures have focused on internally nonblocking networks with packet buffering at the switch outputs. These have optimal throughput and delay performance. The author considers a switch architecture consisting of parallel plans of low-speed internally blocking switch networks, in conjunction with input and output buffering. This architecture is desirable from the viewpoint of modularity and hardware cost, especially for large switches. Although this architecture is suboptimal, the throughput shortfall may be overcome by adding extra switch planes. A form of input queuing called bypass queuing can improve the throughput of the switch and thereby reduce the number of switch planes required. An input port controller is described which distributes packets to all switch planes according to the bypass policy, while preserving packet order for virtual circuits. Some simulation results for switch throughput are presented     

Queueing in high-performance packet switching

The authors study the performance of four different approaches for providing the queuing necessary to smooth fluctuations in packet arrivals to a high-performance packet switch. They are (1) input queuing, where a separate buffer is provided at each input to the switch; (2) input smoothing, where a frame of b packets is stored at each of the input line to the switch and simultaneously launched into a switch fabric of size Nb×Nb; (3) output queuing, where packets are queued in a separate first-in first-out (FIFO) buffer located at each output of the switch; and (4) completely shared buffering, where all queuing is done at the outputs and all buffers are completely shared among all the output lines. Input queues saturate at an offered load that depends on the service policy and the number of inputs N, but is approximately 0.586 with FIFO buffers when N is large. Output queuing and completely shared buffering both achieve the optimal throughput-delay performance for any packet switch. However, compared to output queuing, completely shared buffering requires less buffer memory at the expense of an increase in switch fabric size     

The application of optical packet switching in future communicationnetworks

Telecommunication networks are experiencing a dramatic increase in demand for capacity, much of it related to the exponential takeup of the Internet and associated services. To support this demand economically, transport networks are evolving to provide a reconfigurable optical layer which, with optical cross-connects, will realize a high-bandwidth flexible core. As well as providing large capacity, this new layer will be required to support new services such as rapid provisioning of an end-to-end connection under customer control. The first phase of network evolution, therefore, will provide a circuit-switched optical layer characterized by high capacity and fast circuit provisioning. In the longer term, it is currently envisaged that the bandwidth efficiency associated with optical packet switching (a transport technology that matches the bursty nature of multimedia traffic) will be required to ensure economic use of network resources. This article considers possible network application scenarios for optical packet switching. In particular, it focuses on the concept of an optical packet router as an edge network device, functioning as an interface between the electronic and optical domains. In this application it can provide a scalable and efficient IP traffic aggregator that may provide greater flexibility and efficiency than an electronic terabit router with reduced cost. The discussion considers the main technical issues relating to the concept and its implementation     

The beginnings of packet switching: some underlying concepts

This article was written for a seminar held on the occasion of the Franklin Institute's 2001 Bower Award and Prize for the Achievement in Science to the author "for his seminal invention of packet switching - the foundation of modern communications networks and, in particular the Internet." It describes the author's work 40 years ago focusing on the rationale creating the key concepts of packet switching. The article considers the development of each of a series of about 20 essential concepts. For example, it examines such subjects as the degree of redundancy to achieve any desired level of survivability; the necessity to chop data streams into small blocks; what information had to be appended to these blocks to allow the each block to find its own way through the network; why it was necessary for each network element to operate at an independent data rate; why all signals had to be converted to digital, and so on. It describes the "why" as well as the "how" of packet switching works     

基于OTN的分组交换技术的研究

针对现阶段网络融合的趋势,介绍了如何通过SRA技术来实现OTN的分组交换.先介绍SAR技术的要求和OTN Over Packet Fabric Protocol标准的帧格式,在对功能模块的研究下,提出实现SAR的功能模型.     

Techniques for optical packet switching and optical burst switching

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic     

Technical issues regarding satellite packet switching

Many concepts for advanced communication satellite networks have recently been proposed. Critical technical issues relating to satellite packet switching for meshed very small aperture terminal networks and broadband networks are addressed. Hardware considerations, networking and testing issues are discussed.     

Neural scheduler for real-time packet switching

To resolve transmission conflict in space-division packet switches, it is necessary to find a conflict-free switching schedule with a fixed and short duration. A neural scheduler is proposed for real-time conflict resolution in space-division packet switches. This neural scheduler has smaller mean and variance of the number of iterations compared to existing ones, and can guarantee that P [required number of iterations ⩽n] ⩾P* where n and P* are the requirements specified by the user     

Access control in multicast packet switching

Access control and performance for multicast packet switching in a broadband network environment are studied. In terms of scheduling the transmission of the copies of the packet onto output ports, two basic service disciplines are defined: one-shot scheduling (all the copies transmitted in the same time slot) and call splitting (transmission over several time slots). As subcategories of call splitting, SS (strict-sense) specifies that each packet can send at most one copy to the destination per time slot, whereas WS (wide-sense) does not carry this restriction. A scheme called revision scheduling, which mitigates the head-of-line (HOL) blocking effect by sequentially combining the one-shot scheduling and the call splitting disciplines, is proposed. Output contention resolution implementations, in the form of combinational logic circuits designed to resolve output contentions arising in each of the call scheduling disciplines, are introduced. A neural-network-based contention resolution algorithm is proposed to demonstrate the improvement of the optimal scheduling     

Voice synchronization in packet switching networks

An algorithm for voice synchronization for packet switching networks is presented. The algorithm has been tested both in simulation and on a real network. The algorithm runs on the TRAME packet switching network for both the Vocoder and CELP DoD voice coding standards. Some results of these tests are presented. Some details of the algorithm development and implementation are given as well     

Wavelength conversion in optical packet switching

A detailed traffic analysis of optical packet switch design is performed. Special consideration is given to the complexity of the optical buffering and the overall switch block structure is considered in general. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and bursty traffic. Furthermore, the traffic performance of switch blocks with add-drop switches has been assessed in a Shufflenetwork showing the advantage of having converters at the inlets. Finally, the aspect of synchronization is discussed through a proposal to operate the packet switch block asynchronously, i.e. without packet alignment at the input     

Approaches to optical Internet packet switching

Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer     

A broadband optoelectronic packet switching system

A novel architecture is presented for a optoelectronic hybrid packet-switching system (HYPASS) for the distribution of multiple-bit-rate broadband services. HYPASS is based on an input-buffered/output-controlled arbitration protocol. This packet switch uses novel multiwave-length optical networks to accomplish routing and transmission of the packets. This system is specifically adapted to utilize the strengths of both optical and electronic technologies     

光分组交换的关键技术

在电域内,有电路交换与分组交换之分,随着语音、数据、视频等通信业务正朝着综合的方向发展,数据流量逐渐超过话音流量。这就意味着面向连接的电路交换需要被升级到能支持数据业务的分组交换。分组交换保留电路交换传输时延小的优点,同时克服了线路利用率差的缺点。客观而言,在电域可望取得的进展在一段时间内能满足分组交换的需求,但是研究显示光开发技术的潜力能满足网络的长期需求。互联网快速增长是驱动光分组交换及网络快速发展的动力,得到WDM光传输基础设施的支持。电域TDM技术的增长系数是每年1.5,而每年的带宽需求增长系…     

Design of a broadcast packet switching network

An overview is given of a system designed to handle a heterogeneous and dynamically changing mix of applications. It is based on fiber-optic transmission systems and high-performance packet switching and can handle applications ranging from low-speed data to voice to full-rate video. A novel feature is a flexible multipoint connection capability suitable for broadcast and conferencing applications. The architecture of a switching systems that can be used to support this network is described     

Frequency-hop transmission for satellite packet switching and terrestrial packet radio networks

The performance of frequency-hop transmission in a packet communication network is analyzed. Satellite multiple-access broadcast channels for packet switching and terrestrial packet radio networks are the primary examples of the type of network considered. An analysis of the effects of multiple-access interference in frequency-hop radio networks is presented. New measures of "local" performance are defined and evaluated for networks of this type, and new concepts that are important in the design of these networks are introduced. In particular, error probabilities and local throughput are evaluated for a frequency-hop radio network which incorporates the standard slotted and unslotted ALOHA channel-access protocols, asynchronous frequency hopping, and Reed-Solomon error-control coding. The performance of frequency-hop multiple access with error-control coding is compared with the performance of conventional ALOHA random access using narrow-band radios.