Lars Ramfelt

Fast circuit switching for the next generation of high performance networks

Dynamic synchronous transfer mode (DTM) is a broadband network architecture based on fast circuit-switching augmented with dynamic reallocation of resources. It provides a service based on multicast, multirate channels with short setup delay and supports applications with real-time requirements on quality of service as well as applications with bursty, asynchronous traffic. The paper describes the DTM architecture and its distributed resource management scheme. Performance analysis results from network simulations are presented. The analysis is performed with respect to throughput and access delay for two network topologies: a dual bus and a grid of dual buses. The effects of varying user requirements, internode distances and transfer size are studied for uniform traffic patterns. The results indicate that the overhead for establishing channels is low (a few hundred microseconds), which gives a high degree of utilization even for short transfers. The analysis also shows that when channels are established very frequently, the signaling capacity limits the performance.

The DTM Gigabit Network

DTM is a set of protocols for high-speed networks, based on bandwidth reservation and with support for dynamic reallocation of bandwidth. It is designed for real-time multimedia applications and for high-speed computer communication. DTM uses a novel medium-access technique and provides a multicast, fast circuit-switched service. Several DTM networks can be connected into one large network. A prototype implementation and testbed is being constructed.

Design and implementation of a prototype optical deflection network

We describe the design and implementation of a packet-switched fiber optic interconnect prototype with a ShuffleNet topology, intended for use in shared-memory multiprocessors. Coupled with existing latency-hiding mechanisms, it can reduce latency to remote memory locations. Nodes use deflection routing to resolve contention. Each node contains a processor, memory, photonic switch, and packet routing processor. Payload remains in optical form from source to final destination. Each host processor is a commercial workstation with FIFO interfaces between its bus and the photonic switch. A global clock is distributed optically to each node to minimize skew. Component costs and network performance figures are presented for various node configurations including bit-per-wavelength and fiber-parallel packet formats. Our efforts to implement and test a practical interconnect including real host computers distinguishes our work from previous theoretical and experimental work. We summarize obstacles we encountered and discuss future work.

Resource reservation in DTM

DTM is an optical network with bandwidth reservation and support for dynamic reallocation of bandwidth. DTM is designed for real-time multimedia applications and for high-speed computer communication. DTM provides a service with real-time guarantees: it allows reservation of bandwidth, and has constant delay between two nodes. DTM uses a novel medium-access technique and provides a multicast channel service. The paper describes how resources are reserved in DTM, and describes a DTM prototype implementation to demonstrate that the protocols can be implemented efficiently.<<ETX>>