TCP over ATM: simulation model and performance results

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.

With networks increasingly moving into virtually every aspect of our daily life, security is gaining importance, not only from the traditional perspective of communication but the network's growing role in modern automation and control. The traditional, certification based approach attempts to guarantee the security of a network through certification. Certified networks are generally confined to a limited domain and, as a result, they are isolated, costly, and under-utilized. In contrast, this paper presents a new principle – user-level, security-on-demand system, wherein the network allocates, where possible, the security resources commensurate with the user's request for transporting message(s) through the network securely. This principle is successfully demonstrated for the current Asynchronous Transfer Mode (ATM) networks, and is the result of an integration of the fundamental framework for network security, recently proposed by the authors in the literature, with the unique characteristics of ATM networks. The framework encapsulates the fundamental knowledge and set of relationships in network security and permits scientific and systematic reasoning about network security. It also enables all user groups – military, government, industry, and academia, to define their security requirements in a uniform manner. The security-on-demand approach promises the development of a "mixed use" class of networks in the future that may be simultaneously shared by different groups of users, with the system sustaining the diverse security requirements of each user. A unique characteristic in ATM network design is the dynamic call setup process. Under it, a network first establishes a virtual path or route for a user's call, guided by the user's requirements, and then transports the messages when a route has been successfully determined. This unique ATM characteristic is integrated with the framework to yield a successful demonstration of the proposed, user-level, security-on-demand approach. Utilizing the security framework as the foundation, every element of the network – node and link, is characterized by a security matrix that reflects its security resources. Every user is permitted to specify the security requirement for the call through a matrix, which expresses the limits of the security resources that the traffic cells must encounter during their transport through the network. Thus, during the dynamic establishment of the virtual path, every node and link is examined to ensure that the user-specified security is met, in addition to bandwidth and other Quality of Service (QoS) requirements. Traffic is launched when the call setup succeeds, otherwise, the call fails. Like all networks, the ATM network inherently consists of geographically dispersed entities and, as a result, the resource allocation strategy is necessarily distributed. Furthermore, as the network operation progresses, the resource availability scene changes dynamically. This paper proposes a unique function that reduces the key network resource parameters at a node to a single value, termed Node Status Indicator (NSI). The NSI value is computed dynamically at every node and disseminated across the network to be utilized by a node to refine its determination of a virtual path for a user call. The aim of the NSI is to improve the resource utilization in the network. The proposed approach is modeled for a large-scale, representative, 40-node ATM network. Utilizing stochastic input traffic that is synthesized to reflect realistic operating conditions, the model is simulated extensively on a testbed of 35+ Pentium workstations, under Linux, configured as a loosely-coupled parallel processor, utilizing an accurate, asynchronous, distributed simulator. The simulator implements the key characteristics of the ATM Forum proposed P-NNI 1.0 and UNI 3.0 standards. While the simulation results reflect a successful realization of the proposed approach, analysis reveals minimal impact of incorporating security on ATM network performance, as measured through call success rates and call setup times. In contrast, the tradition has been to incorporate security into large-scale systems and networks as an afterthought, i.e. adding hardware and software devices after the design has been completed, resulting in performance degradation. Also, while the use of NSI is observed to yield slightly lower average call setup rates and slightly higher average call setup times, a careful analysis of the trace of the calls as they progress through the system, reveals that, in general, calls are dispersed throughout the network, seeking to utilize all available resources of the network more evenly.

Performance of TCP in IP/ATM internetworks

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.

This paper considers the influence of switch fabric design on the performance of resource allocation and connection admission algorithms for asynchronous transfer mode (ATM) networks. In particular, the goal of predictable and guaranteed quality of service (QoS) can be achieved within an ATM network by considering the above factors in the design of the ATM switch fabric. The paper focuses on the identification of the functional requirements of the switch fabric at the ATM layer, and develops an improved architecture which considers QoS at the switch fabric, along with an interface to the resource management. The resultant switch results in ATM networks which have reliable and predictable parameters and which have reduced complexity in connection admission control.

An asynchronous transfer mode (ATM) network is a high-speed multimedia network which handles various kinds of traffic with different bit-rates and different qualities of service (QoS). In order to maintain the QoS for each traffic source and to avoid possible congestion problems, an ATM network requires highly sophisticated and flexible controllers to insure that this demanding performance can be achieved under unexpected changes in traffic conditions. In this paper, we propose an intelligent architecture using recurrent neural networks and an expert system for traffic control in ATM networks. This traffic control using neural networks is suitable for ATM because neural networks can learn the traffic characteristics and the dynamic changes in the traffic. The proposed mechanism is based on the adaptive prediction of the future values of the traffic and the flow rate for each traffic source. At every given time slot, the controllers in the proposed architecture predict whether the congestion will happen or not and regulate the volume of input traffic for each traffic source before the congestion happens, maintaining the user-required QoS for each traffic source based on the predefined rules. Consequently, the mechanism guarantees the QoS for each traffic source and efficiently prevents congestion.

We propose a congestion control algorithm and design a state feedback controller for regulating the congestion of available bit rate (ABR) traffic in asynchronous transfer mode (ATM) networks. ABR service is specified as the rate-based feedback mechanism for congestion control and provides a control signal to throttled sources from a bottleneck node in order to adjust the throttled source rates based on available capacity. Our main purposes are as follows: (1) to design a state feedback controller; (2) to place the closed-loop poles in any desired regions based on a pole placement constraint; (3) to use the LMI (linear matrix inequalities) approach for finding the optimal state feedback gain K. The simulation results show that, under pole placement and LMI approaches, our state feedback congestion controller for ABR traffic in ATM networks can possibly guarantee the system stability, provide no buffer overflow, determine the optimal source traffic rates and place the closed-loop poles in any desired regions as well.

The Communications Research Laboratory (CRL), Tokyo, Japan, and the Telecommunication Network Laboratory Group, Nippon Telegraph and Telephone Corp., Tokyo, Japan, have developed a highly precise, very long baseline interferometry (VLBI) system using a high speed asynchronous transfer mode (ATM) network. The observed data is transmitted through a 2.488-Gbps ATM network [STM-16/OC-48] instead of being recorded onto magnetic tape. The system was specially designed for the Key Stone Project (KSP), a project begun in 1994 to measure crustal deformation in the Tokyo metropolitan area. Cross-correlation processing and data observations are carried out simultaneously by one operator. It takes about one hour to analyze the data after the observations and correlations are completed. In regular geodetic VLBI experiments run every other day for 24 h, a horizontal position uncertainty of about 2 mm and a vertical position uncertainty of about 10 mm were achieved. The system was designed to enable automated operation throughout the entire process. The results obtained are available to the public via the Internet at http:ksp.crl.go.jp. This system is a significant advance in VLBI and should provide more precise information about crustal deformation in the Tokyo metropolitan area.

In this paper, we study the possibility of using Evolvable Hardware (EHW) for scheduling real-time traffic in Asynchronous Transfer Mode (ATM) networks. EHW is hardware which is built on programmable logic devices and whose architecture can be reconfigured by using genetic learning to adapt to new environments. A novel design is the function-level EHW [5, 9] based on Field Programmable Gate Array (FPGA) chips, where a number of Programmable Floating processing Units (PFUs) are embedded in one chip. The selectable high-level hardware functions of each PFU make the function-level EHW to be suitable for a wide variety of applications in practice. In our experiment, a statistical multiplexer at an ATM node is modeled for the purpose of generating training data. Superposed bursty cell streams are applied to the model of the multiplexer. The EHW is trained by the collected data in the learning phase. After learning is complete, the best chromosome is tested with respect to various traffic characteristics and the Quality Of Service (QOS) requirements of the cell traffic. Simulation results show that the function-level EHW performs the control well for cell scheduling problem in ATM networks.

ATM(Asynchronous transfer mode) network was introduced in this paper. It has high transmission speed. It's transmission distance is not limited. It gathers voice transmission, image transmission and audio transmission in integral whole. China map was selected as network background and 10 cities (Wuhan, Beijing, ect.) were selected as nodes. The simulation of ATM network was established to study on the throughput and the average utilization of ATM network. Study on the survivability and the extending feasibility of ATM network. Analyzing the bottleneck of the network and optimizing ATM network.

This paper presents a systems view of video transport issues in asynchronous transfer mode (ATM) networks. Since video is a critical component of future distributed multimedia applications, we consider technical approaches necessary to realize a flexible, robust, and efficient ATM framework for video delivery. The overall system-design problem is discussed for a general distributed multimedia computing scenario, and key video-related design issues are identified. This is followed by a more detailed discussion of selected ATM video topics, including: (1) variable bit-rate (VBR) statistical multiplexing and dynamic usage parameter control (VBR+), (2) ATM cell-loss concealment in MPEG decoders, and (3) new transport protocols (“MTP”) for video and multimedia. Supporting simulation or experimental results from ongoing research are given where available.

Admission control in asynchronous transfer mode (ATM) networks is considered. An ATM switch is modeled as a discrete-time single-server queue at which the following three different kinds of arrival processes are allowed to join together: arrivals of cells with a general interarrival time distribution; Bernoulli arrivals of cells in batches; and interrupted Poisson processes. An exact analysis is given to derive the waiting-time distributions and interdeparture-time distributions for arriving cells subject to admission control in ATM networks. The model is extended to approximately obtain the end-to-end delay distributions for the designated traffic stream. Such an analysis is important for voice or coded video because they require a playout mechanism at the destination. Since the analysis is approximate, the simulation results needed to assess its accuracy are provided. Numerical examples show how the traffic characteristics of the designated traffic stream are affected by the total traffic load at the switching node, the number of other bursty traffic sources, and the degree of burstiness of the traffic source itself.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Various communications services are provided over asynchronous transfer mode (ATM) networks, and traffic produced by these various services has various characteristics. Thus, in attempting to utilize circuits effectively by statistical multiplexing effects as in ATM networks, band management control reserving bands necessary to ensure communications quality in terms of cell loss probability, etc., is necessary when a call occurs. In addition, since communications quality required by various services differ, band management considering priority processing is effective. In addition, since a number of switching machines exist between transmission and reception nodes and a number of channels exist in links between each ATM switching machine, control to select one of these channels at the time of call setup is important. It is necessary even in this case to sufficiently consider traffic characteristics of calls for each service.In this paper, channel selection methods for such multichannel links are studied. For this purpose, the multiplicity of traffic establishable for a set of channels is obtained analytically following a step‐modeling technique and the efficiencies of various channel selection methods for a number of channels are studied. The characteristics and efficiency of each method are clarified by analyses and simulation using channel utilization rate and call loss rate as efficiency parameters for designing the efficiency of channel selection systems.

A variable-bit-rate voice coding suitable for asynchronous transfer mode (ATM) networks is described. The method uses an ADPCM coder that can operate at 2, 3, 4, or 5 b/sample, depending on parameters such as incoming signal power and prediction gain. It aims at processing simplicity and high quality when applied to ATM cell assembly/disassembly equipment. Experiments with several voice samples show that average rates are one third to one half of 64 kb/s with quality almost equivalent to PCM coding. >

This paper proposes an implementation scheme for the self-healing function in ATM (Asynchronous Transfer Mode) networks and assesses its performance in a developed experimental system. First, our proposed ATM self-healing scheme is described. This scheme realizes more rapid restoration of failed Virtual Paths than other self-healing algorithms, supports the node failure case, and minimizes the spare resources required. Next, an implementation scheme is proposed. We propose that the self-healing function can be implemented as a software process, and that OAM (Operation, Administration, and Maintenance) cells be utilized for fast message transmission. Next, results of a prototype system that we implemented on an ATM cross-connect system are discussed. The fundamental characteristics of restoration performance are measured using the experimental system. Based on these results, restoration characteristics of real world scale networks are estimated by computer simulations. The simulation results indicate that any-one link failure is completely restored within 2 seconds.