ATM and Internet via satellite

During the last decade, the European Union (EU) created the RACE programme (Research and Development in Advanced Communications Technologies for Europe) and the ACTS programme (Advanced Communications Technologies and Services). These programmes played a key role in developing the crucial technology for networking with asynchronous transfer mode (ATM) and Internet protocol (IP). ATM promised to provide a high performance networking platform for new broadband multimedia communications while allowing simultaneous conveyance of existing voice, data and broadcasting services. IP provided the flexibility and pervasiveness to impose itself as a common, necessary, networking standard. European collaboration through the RACE programme resulted in world standards for the ATM system in the early 1990s. "Operational Trials" of high performance networks were performed as part of the ACTS projects and the TEN-IBC programme, which involved different types of users, applications, network operators (national hosts) and the European ATM network JAMES. The current ACTS projects are focusing on IP/ATM integration and next generation IP technologies which will be strongly promoted in the coming 1999-2002 Information Society Technologies (IST) programme.

While the transmission control protocol (TCP) generally provides robust performance across many network environments, several researchers have identified the poor end-to-end performance achieved by TCP on asynchronous transfer mode (ATM) networks. The performance problems arise for several reasons: (1) a size mismatch between TCP segments and ATM cells; (2) the simple protocols used for segmentation and reassembly in ATM, and for retransmission in TCP; (3) specific optimizations in TCP, made primarily for low-bandwidth Internet environments which do not work well in high speed ATM networks; (4) features (or misfeatures) in most TCP protocol implementations; and (5) subtle interactions between all of these factors. This paper describes a simulation model that we have constructed to study TCP performance on ATM networks, as well as a set of simulation experiments conducted using the model. The TCP model is detailed enough to recreate many of the performance problems identified by other researchers, as well as to evaluate potential solutions to the performance problems. The TCP model adds to the traffic modeling toolkit available in our existing ATM network simulator, and enables the further study of performance issues in TCP over ATM.

Performance of TCP in IP/ATM internetworks

Internetwork bridge connects Ethernet and broadband networks

The number of Internet users continues to increase due to the popularity of the WWW (World Wide Web). Intranets and extranets have also become very popular as they enable the efficient use of data within companies and enhance business processing speed. IP (Internet protocol) packets are used to realize most of these computer communication services. IP belongs to the network layer in the OSI reference model, so the transfer performance of IP is influenced by the technology used in the data link layer under the network layer. One communication technology for the data link layer is ATM (asynchronous transfer mode). ATM technology was researched and recommended for B-ISDN (broadband integrated services digital network). We have been tackling an Internet/intranet/extranet backbone system that offers high speed, high throughput, small delay and low cost by IP/MAC (media access control) over ATM. However we faced the problem that ATM does not completely suit IP packet and MAC frame transfer. For example, there is the "dead cell problem" in which the loss of even one of the ATM cells forming the IP packet causes the loss of the entire packet. There is also the "cell tax problem", in which the overhead of ATM cells is much larger than those of other long distance transfer techniques. Perfect EPD (early packet discard) is impossible because there is no indication bit that means a cell includes the head or tail part of a datagram in the payload. Moreover, intelligent and effective application use is difficult because the cell header has few CLP (cell loss priority) bits. This paper describes the main problems of datagram transfer across existing ATM networks and details a new cell structure that solves these problems. Other issues relating to this remodelling of the existing cell structure are also examined.

Communications over wide area networks are becoming a commonly used form of commercial interaction. Internet Protocol (IP) transfer of data packets has facilitated world-wide connectivity of employees who use computers as a daily tool. There is rapidly growing interest in Asynchronous Transfer Mode (ATM) networking as a means of increasing service, while reducing cost-per-bit for transmission. ATM can simultaneously carry IP data packets along with other data forms such as voice and video. In the commercial world, which has become aware of the need for security on its data transmissions and is just beginning to acquire products individually for IP, or voice, or video data security, there now arises the potentially unifying transfer mechanism of ATM, and with it the prospect of a seemingly more unified ATM security process as well. As first applications of ATM security are emerging, we enter an era of complex requirements and issues that must be addressed if these security products are to be genuinely used. This paper will begin with a brief introduction to ATM encryption as a process. However, its primary focus will be upon the issues and technical challenges that face potential developers of ATM encryption products. This is useful because the type of encryption a designer selects and the details of its implementation are influenced by the threat to be addressed as well as the communication environment. These decisions will be influenced particularly heavily for ATM by the initial investment required to develop an encryptor. A summary of the state-of-the-art will be provided in conclusion.

Medical information systems are acquiring the ability to collect and deliver many different types of medical information. In support of the increased network demands necessitated by these expanded capabilities, asynchronous transfer mode (ATM) based networks are being deployed in medical care systems. While ATM supplies a much greater line rate than currently deployed networks, the management and standards surrounding ATM are yet to mature. This paper explores the management and control issues surrounding an ATM network supporting medical information systems, and examines how management impacts network performance and robustness. A multivendor ATM network at the BJC Health System/Washington University and the applications using the network are discussed. Performance information for specific applications is presented and analyzed. Network management's influence on application reliability is outlined. The information collected is used to show how ATM network standards and management tools influence network reliability and performance. Performance of current applications using the ATM network is discussed. Special attention is given to issues encountered in implementation of hypertext transfer protocol over ATM internet protocol (IP) communications. A classical IP ATM implementation yields greater than twenty percent higher network performance over LANE. Maximum performance for a host's suite of applications can be obtained by establishing multiple individually engineered IP links through its ATM network connection.

Chapter 2 - Networks Supported—Keeping Existing Infrastructures in Place

Because Transmission Control Protocol (TCP) is widely used to reliably transport data, there is considerable interest in its performance over Asynchronous Transfer Mode (ATM). Much research has been done in this area and results are available, mainly from computer simulations. However, simulation results do not contain the steps required by the user to optimize TCP performance. Nascom needed that information. This paper addresses different tests. It uses each test summary as an example for a specific issue. The summaries include configuration, results, and comments. The hardware and software used also are listed. Based on NASA Communications (Nascom) test results, this paper shows that existing router implementations degrade TCP over ATM performance, that unspecified bit rate (UBR) is preferred over variable bit rate (VBR) for a traffic contract, and that multiple streams fairly share one ATM network.

A performance study of the explicit congestion notification (ECN) mechanism in the transmission control protocol (TCP) over ATM (asynchronous transfer mode) networks is presented. TCP's congestion control is enhanced so that congestion is indicated by not only packet losses as is currently the case but an agent implemented at the ATM network's edge as well. Our simulation experiments show that TCP ECN achieves: significantly lower cell loss, packet retransmissions, buffer utilisation and exhibits better throughput than (non-ECN) TCP Reno.

SUMMARYApplications that use the reliable Transmission Control Protocol (TCP) have a significant degradation over satellite links. This degradation is mainly a consequence of the congestion control algorithm used by standard TCP, which is not suitable for overcoming the impairments of satellite networks. To alleviate this problem, two TCP Performance Enhancing Proxies (PEPs) can be deployed at the edges of the satellite segment. Then these PEPs can use different mechanisms such as snooping, spoofing and splitting to achieve a better TCP performance. In general, these mechanisms require the manipulation of the Internet Protocol (IP) and TCP headers that generates a problem when deploying the standard IP security (IPsec) protocol. The security services that IPsec offers (encryption and/or authentication) are based on the cryptographic protection of IP datagrams, including the corresponding IP and TCP headers. As a consequence, these cryptographic protections of IPsec conflict with the mechanisms that PEPs use to enhance the TCP performance in the satellite link. In this article, we detail the reasons that cause this conflict, and we propose three different approaches to deploy IPsec in a scenario with TCP PEPs. Our proposals provide different trade‐offs between security and TCP performance in some typical scenarios that use satellite networks. Copyright © 2012 John Wiley & Sons, Ltd.

ATM for legacy aircraft avionics

Asynchronous transfer mode (ATM) is a high speed computer network technology, a cell switching technique that uses asynchronous time division multiplexing. ATM is not completely compatible for existing higher layer protocols like transmission control protocol and Internet protocol that operate in internet environment. This document addresses the problems of bandwidth delay and also possible approaches to ATM interoperations like new protocol design especially for ATM, extension of existing protocols to add support for ATM, design special protocols to integrate ATM with below existing internetworking and transport layer protocol layers.

Soon the days of separate transmission facilities for video will be over, and video will be just another traffic type in amultipurpose network. These networks today employ a variety of transport mechanisms, for historical as well as technicalreasons, and, at least experimentally, enterprises, network operators, and service providers are sending video over thesenetworks with their associated transport mechanisms. But video is not just a random bit stream, so it is natural to ask howwell the transport mechanisms perform when transporting video. In this paper we examine what video needs from capture toplayback and how these can be provided by the end system or the network using the MPEG transport stream, asynchronoustransfer mode, and the Internet Protocol. We concentrate on the Internet Protocol because of the opportunity for networkedvideo applications that its pervasion provides.Keywords: IP Video, IP Multicast, IP Premium Service, MPEG, ATM Video 1. INTRODUCTION As video becomes increasingly represented in digital form, it enters the networked world, in which it shares network facilitieswith other types oftraffic. It does so at a time of upheaval and transition in networking, on severn! fronts. High-bandwidthdigital networks reach more and more homes, and most of these employ cable television facilities. For these, the MPEGtransport stream carries MPEG-2 video along with its associated audio channel and also data. Digital subscriber lines, whilenot as prevalent as digital CATV networks, allow a few megabits of traffic (downstream anyway) and most commonly relyon ATM for basic transport. In the Internet and most enterprise networks, the Internet Protocol (IP)' dominates, and legionsof engineers worldwide strive to make IP the foundation for all data, voice, and video traffic.New advances in [P networking allow high quality video services for both continuous playback and interactive applications.The IP technologies facilitating support of high quality video on IP networks are: 1) dynamic algorithms used by videoterminals for smoothing jitter and clock slippage; 2) extended IP transport services providing reduced jitter, and 3) IPmulticast services for distributing broadcast video to large populations. This paper outlines a model for video transmissionover IP then contrasts the service to video transmissions over MPEG transport and ATM transport. We also consider theimportant role ofthe end system in augmenting what the network can do.1.1 Differences in VideoTo make sure we do not compare apples to oranges, we must keep in mind that there are different forms ofvideo, and this hasa bearing on the network transport. We assume that entertainment video is coded natively using the MPEG-2 programstream, requires 1 .5-6 Mb/s for sufficient quality, lasts from several minutes to several hours, conforms to a standard imagesize, and is used in urndfrectional applications rather than interactive ones; thus delay jitter is more important than absolutedelay through a network. Moreover, viewers typically pay to receive entertainment video and so demand high quality.Conferencing video is coded using the H.32x family of standards, requires from around 30 kb/s to over 1 Mb/s, takes ondifferent image sizes and aspect ratios, and because of its interactivity suffers in usefulness from absolute delay as well asdelayjitter. Quality is important but the viewer typically does not pay to receive the video and is therefore less demanding ofquality; also, the audio quality is usually more important because of the nature of the communication between live people.Web streaming

To deyelop the broadband integrated services digital network (B‐ISDN) service on a national scale and to handle various media in a unified way economically from ‐ an early stage, it will be effective to construct a system combining the satellite link into the terrestrial communication network. the TDMA system is adequate as the transmission system in the satellite link in such a system which can contain efficiently users distributed over a country.When the satellite TDMA link, which is a synchronous system, and the terrestrial network, based on the asynchronous transfer mode (ATM), are to be connected, the deterioration of the ATM transmission quality such as the cell delay variation, is a serious problem. Then there must be a compensation method for the delay variation which can cope with the asynchronous transfer. In such a transformation between ATM and TDMA, it is required that the maximum delay variation should be kept below the specified value, the burstiness of the transferred cell sequence should not be increased, and the satellite link with limited network resources should efficiently be utilized.This paper assumes that the time‐stamp method, which is considered in the ground network, is applied to the satellite link as a method for the delay variation 38 compensation and summarizes the problems in the application. Then the cell‐numbering method is proposed and the performance is evaluated to solve the problems.