A survey of high-performance switch fabric architectures which incorporate fast packet switching as their underlying switching technique to handle various traffic types is presented. A descriptive overview of the major activities in this rapidly evolving field of telecommunications is given. The switch fabrics are classified into the following categories: banyan and buffered banyan-based fabrics, sort-banyan-based fabrics fabrics with disjoint-path topology and output queuing, crossbar-based fabrics, time division fabrics with common packet memory, and fabrics with shared medium. >

A survey of modern high-performance switching techniques

For reasons of economy and flexibility, BISDN (Broadband Integrated Services Digital Network) is expected to replace existing application-oriented communication networks. ATM (Asynchronous Transfer Mode) is a high-speed packet-switching technique that has emerged as the most promising technology for BISDN. Since early 1980s, a large number of architectures have been proposed for ATM switching. In this paper, we present a descriptive survey of ATM switch architectures, with emphasis on electronic space-division point-to-point switches.

Survey of ATM switch architectures

A ATM communication system can satisfy various requests from a node system, a link system, and the like, by performing a self-format transform between a format to be transmitted and a format receiving an ATM switch, and using a cell processing function for performing polishing/shaping, counting of passed cells, counting of discarded cells, drop/insertion of OAM cell, and the like.

ATM communication system

A high capacity metropolitan area network (MAN) is described. Data traffic from users is connected to data concentrators at the edge of the network, and is transmitted over fiber optic data links to a hub where the data is switched. The hub includes a plurality of data switching modules, each having a control means, and each connected to a distributed control space division switch. Advantageously, the data switching modules, whose inputs are connected to the concentrators, perform all checking and routing functions, while the 1024×1024 maximum size space division switch, whose outputs are connected to the concentrators, provides a large fan-out distribution network for reaching many concentrators from each data switching module. Distributed control of the space division switch permits several million connection and disconnection actions to be performed each second, while the pipelined and parallel operation within the control means permits each of the 256 switching modules to process at least 50,000 transactions per second. The data switching modules chain groups of incoming packets destined for a common outlet of the space division switch so that only one connection in that switch is required for transmitting each group of chained packets from a data switching module to a concentrator. MAN provides security features including a port identification supplied by the data concentrators, and a check that each packet is from an authorized source user, transmitting on a port associated with that user, to an authorized destination user that is in the same group (virtual network) as the source user.

Architecture and organization of a high performance metropolitan area telecommunications packet network

The rapid development of Asynchronous Transfer Mode technology in the last 10-15 years has stimulated renewed interest in the design and analysis of switching systems, leading to new ideas for system designs and new insights into the performance and evaluation of such systems. As ATM moves closer to realizing the vision of ubiquitous broadband ISDN services, the design of switching systems takes on growing importance. This paper seeks to clarify the key architectural issues for ATM switching system design and provides a survey of the current state-of-the-art.

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Architectural choices in large scale ATM switches

Being the communication core of future broadband products, the ATM based switching network architecture must comply with a challenging set of future safe requirements and objectives, which are tentatively defined first. After some period of research work, a number of different solutions for fast packet switching or ATM switching are still proposed. It is thus interesting to discuss the respective attributes of key architecture options for asynchronous switch fabrics. As an illustration, the paper then describes a new ATM based switching architecture for asynchronous communications based on the advantageous combination of a multiple-path self-routing principle with an internal transfer mode using multi-slot cells. These principles are the foundation for a flexible and fault tolerant switching network configuration built with two Weis of standard switching components: the Switch Module board equivalent to a 128 x 128 single-stage matrix operating at 150 Mbit/s, and the Integrated Switching Element LSI circuit realizing an elementary, fully featured, 32 x 32 switching matrix.

Switching network architecture for atm based broadband communications

This paper describes a switching network which is service independent and able to transport services of any bit rate, based on the fast packet switching concept. The control of the switching network is completely distributed; the path select is not centrally controlled, but gradually performed as the control packet is passing through the switching network. The switching network is a multistage network constructed with independent switching elements. The self-routing principle is applied. The load control of the different links between the switching elements in the network is provided by a static load control mechanism, applied to the logical connections granted on these links. Logical connections are accepted or rejected according to the already present load on each link. Possible overload caused by bursty traffic is solved by buffers within the switching elements. Simulation results are discussed, both for the static and dynamic behavior of the exchange. For both simulations, a large mix of different services is evaluated and conclusions are described.

Performance of a Service Independent Switching Network with Distributed Control

This article presents a mechanism of action hypothesis to explain the rapid antidepressant effects of esmethadone (REL-1017) and other uncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonists and presents a corresponding mechanism of disease hypothesis for major depressive disorder (MDD). Esmethadone and other uncompetitive NMDAR antagonists may restore physiological neural plasticity in animal models of depressive-like behavior and in patients with MDD via preferential tonic block of pathologically hyperactive GluN2D subtypes. Tonic Ca2+ currents via GluN2D subtypes regulate the homeostatic availability of synaptic proteins. MDD and depressive behaviors may be determined by reduced homeostatic availability of synaptic proteins, due to upregulated tonic Ca2+ currents through GluN2D subtypes. The preferential activity of low-potency NMDAR antagonists for GluN2D subtypes may explain their rapid antidepressant effects in the absence of dissociative side effects.

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Esmethadone (REL-1017) and Other Uncompetitive NMDAR Channel Blockers May Improve Mood Disorders via Modulation of Synaptic Kinase-Mediated Signaling

ATM has been selected as the transer mode for future integrated broadband networks. It has already been highlighted in numerous papers that ATM is capable of transferring voice, video and data. This paper describes the capability of ATM to transfer also signalling information and the impact of ATM on signalling as well as the capability of ATM to build a very powerful maintenance concept which can be used ubiquitous; i.e. as well in the transmission as in the switching systems. First this paper will describe the impact of ATM on signalling. This impact can be seen on all levels of the protocol stack. On level one the disappearance of a fixed D channel as in NISDN introduces the need for a meta-signalling concept for multidrop environments. The opportunities generated by this meta-signalling are described here. The impact on level 2 is the need to introduce a segmentation and reassembly layer On level 3 the impact of ATM is mostly reflected through the deftnition of the ATM bearer service. The maintenance philosophy of a future broadband network is also a keypoint to its success. Since ATM can be considered as a switching as well as a transmission principle, a universal maintenance concept can be defined This maintenance philosophy includes where and what sort of maintenance information and how this is gathered. Secondly, how this information is then transported to the maintenance centers and finally how this information is interpreted.

M. De Somer

Papers

Switching network architecture for atm based broadband communications

Performance of a Service Independent Switching Network with Distributed Control

Esmethadone (REL-1017) and Other Uncompetitive NMDAR Channel Blockers May Improve Mood Disorders via Modulation of Synaptic Kinase-Mediated Signaling

ATM as a universal transfer medium for user information, signalling and operation and maintenance