Autonet is a self-configuring local area network composed of switches interconnected by 100 Mb/s, full-duplex, point-to-point links. The switches contain 12 ports that are internally connected by a full crossbar. Switches use cut-through to achieve a packet forwarding latency as low as 2 ms/switch. Any switch port can be cabled to any other switch port or to a host network controller. A processor in each switch monitors the network's physical configuration. A distributed algorithm running on the switch processor computes the routes packets are to follow and fills in the packet forwarding table in each switch. With Autonet, distinct paths through the set of network links can carry packets in parallel, allowing many pairs of hosts to communicate simultaneously at full link bandwidth. A 30-switch network with more than 100 hosts has been the service network for Digital's Systems Research Center since February 1990. >

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Autonet: a high-speed, self-configuring local area network using point-to-point links

Future routers must not only forward packets at high speeds, but also deal with nontrivial issues such as scheduling support for differential services, heterogeneous link technologies, and backward compatibility with a wide range of packet formats and routing protocols. The authors outline the design issues facing the next generation of backbone, enterprise, and access routers. The authors also present a survey of advances in router design, identifying important trends, concluding with a selection of open issues.

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Issues and trends in router design

This letter proposes a combined inputand crosspoint-queued (CIC) switch in which virtual output queuing (VOQ) is used at each input port. This CIC switch has a large buffer at each input port and a small buffer at each crosspoint. It does not require high-speed memory access or high-speed internal cell transmission lines. Since the performance of the CIC switch depends on the scheduling algorithms, we propose new scheduling algorithms for the CIC switch. Numerical results show that the mean cell delay time performance of the CIC switch using the proposed scheduling algorithms is better than that of an inputqueued ATM switch. In addition, the required buffer size for the CIC switch using the proposed scheduling algorithms is smaller than that for a crosspoint-queued ATM switch. key words: input-queued ATM switch, crosspoint-queued ATM

Performance Evaluation of a Combined Input- and Crosspoint-Queued Switch

The authors propose a single way to dramatically improve the performance of input-queued ATM packet switches beyond the 82% saturation point obtained in previous work. The method is an extension of the independent output-port schedulers technique and is based on the notion of recycled time slots, i.e. reusing time slots normally wasted due to scheduling conflicts. In contrast to previous results, the technique yields a throughput improvement from 65% to 92% without speedup, trunking, or complicated hardware. If input grouping with a group size of four is also employed, then the method can yield up to 95% throughput. >

Improving the performance of input-queued ATM packet switches

The authors survey networking solutions that have been proposed for high-speed packet-switched applications. Using these solutions as examples, they identify the specific problems resulting from very high transmission rates and explain how these problems influence the design of high-speed networks and protocols. They conclude that the solutions based on deflection routing are the most promising ones and suggest a number of directions for their evolution. By a packet-switching protocol we mean the network-specific portion of the third OSI layer (i.e., the network layer) of the protocol stack. One part of a packet-switching protocol (according to our definition) is the routing scheme, i.e., the set of rules that assign incoming packets to output links. In general, we can talk about the following three components of the communication subnetwork which are relevant from our point of view: the routing protocol; the congestion-control mechanisms that can be effectively incorporated into the routing protocol; and the network topology. These components are closely related to each other and together offer a single functionality. We discuss routing protocols and congestion-control mechanisms employed in contemporary packet-switched networks, not necessarily in networks operating at very high transmission rates. Then, following some basic definitions related to the topology component, we investigate the challenges posed by the Gb/s transmission rates. >

Routing in multihop packet switching networks: Gb/s challenge

The major ATM switch architectures and their improvement techniques are categorized and discussed, focusing on performance issues. The performance measures of interest are the maximum throughput, the delay time, and the cell loss probability. The major assumptions and notations used are summarized. A survey is presented of nonblocking switches and their improvement techniques. The performances of a variety of nonblocking switches are compared. >

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D. Kolson

Papers

Survey of switching techniques in high-speed networks and their performance