Charles F. Barry

Implementation of STARNET: a WDM computer communications network

STARNET is a broadband backbone optical wavelength-division multiplexing (WDM) local area network (LAN). Based on a physical passive star topology, STARNET offers all users two logical subnetworks: a high-speed reconfigurable packet-switched data subnetwork and a moderate-speed fix-tuned packet-switched control subnetwork. Thus, STARNET supports traffic with a wide range of speed and continuity characteristics. We report the analysis and implementation of an entire STARNET two-node network, from the optical to the computer layer, at the Optical Communications Research Laboratory (OCRL) of Stanford University. To implement the two logical subnetworks, we designed and implemented two different techniques: combined modulation and multichannel subcarrier multiplexing (MSCM). OCRL has already demonstrated several combined modulation techniques such as phase shift-keyed and amplitude shift-keyed (PSK/ASK), and differential phase shift-keyed and amplitude shift-keyed (DPSK/ASK), yielding combined ASK/DPSK modulation receiver sensitivities better than -32 dBm. OCRL has designed and implemented a high-speed high-performance packet-switched STARNET computer interface which enables high-throughput transfer to/from host computer, low latency switching, traffic prioritization, and capability of multicasting and broadcasting. With this interface board, OCRL has achieved average transmit and receive throughputs of 685 Mb/s and 571 Mb/s, respectively, out of the 800 Mb/s theoretical maximum of the host computer bus. The incurred packet latency due to the interface for a specified multihop network configuration has been simulated to be 24 /spl mu/s. Using simulation and experimental results, it is shown that STARNET is highly suitable for high-speed multimedia network applications.

WDM local area networks

Services and possible network topologies are discussed. The technological issues related to the implementation of such topologies are investigated, covering optical transmitters and receivers, tunable lasers and filters, and polarization control. Some experimental implementations reported in the literature are described.<<ETX>>

Experimental PSK/ASK transceiver for the STARNET WDM computer communication network

STARNET is an optical wavelength-division-multiplexed computer communication network that offers each user both a circuit-switched subnetwork and a packer-switched subnetwork. The authors constructed an experimental STARNET node transceiver. The transceiver uses one integrated phase and amplitude modulator to transmit 125 Mb/s amplitude-modulated packet-switched data and 2.488 Gb/s phase modulated circuit-switched data using the same lightwave. The transmitter has an output power of 5 dBm at 1.32 mu m. The receiver recovers the circuit-switched and packet-switched data using heterodyne detection and has a sensitivity of -25 dBm. The resulting system power budget is 30 dB.<<ETX>>

Network Interface Design for Multi-Gbit/s WDM Optical Networks

We report on the design of a distributed, small, fast packet switched network interface that provides electronic buffering and switching for the data channel in reconfigurable multi-Gbps WDM optical networks. The high-speed interface has been constructed and tested in one such WDM network, STARNET, which is based on a physical passive star topology and is intended for backbone applications in Campus Networks. A two-node experimental STARNET is being implemented at the Optical Communications Research Laboratory at Stanford University. The interface prototype was completed in September 1993; the printed circuit board version of the interface has been operational without modification since January 1994. We have since developed software from the driver level to the applications layer.

Characterization, adaptive traffic shaping, and multiplexing of real-time MPEG II video

We obtain network traffic model for real-time MPEG-II encoded digital video by analyzing video stream samples from real-time encoders from NUKO Information Systems. MPEG-II sample streams include a resolution intensive movie, City of Joy, an action intensive movie, Aliens, a luminance intensive (black and white) movie, Road To Utopia, and a chrominance intensive (color) movie, Dick Tracy. From our analysis we obtain a heuristic model for the encoded video traffic which uses a 15-stage Markov process to model the I,B,P frame sequences within a group of pictures (GOP). A jointly-correlated Gaussian process is used to model the individual frame sizes. Scene change arrivals are modeled according to a gamma process. Simulations show that our MPEG-II traffic model generates, I,B,P frame sequences and frame sizes that closely match the sample MPEG-II stream traffic characteristics as they relate to latency and buffer occupancy in network queues. To achieve high multiplexing efficiency we propose a traffic shaping scheme which sets preferred 1-frame generation times among a group of encoders so as to minimize the overall variation in total offered traffic while still allowing the individual encoders to react to scene changes. Simulations show that our scheme results in multiplexing gains of up to 10% enabling us to multiplex twenty 6 Mbps MPEG-II video streams instead of 18 streams over an ATM/SONET OC3 link without latency or cell loss penalty. This scheme is due for a patent.

A multi-Gbit/s optical LAN utilizing a passive WDM star: towards an experimental prototype

The goals and basic node configuration of STARNET, an optical broadband local area network based on a physical passive star topology, are presented. Over a single physical network, STARNET offers all users both a moderate-speed packet network and a high-speed WDM circuit interconnect. Several topological and protocol solutions based on these two data transport facilities are available to the users. An ongoing experimental effort aimed at the realization of a STARNET prototype is described. The prototype nodes are FDDI and SONET OC-48 data-format-compatible. The first four network layers will be fully implemented and the nodes will serve high performance workstations.<<ETX>>

An experimental multi-Gb/s WDM broadband network

STARNET is an optical broadband network architecture based on a physical passive star topology. Over a single physical network, STARNET offers all users both a moderate-speed packet switched subnetwork and a high-speed wavelength division multiplexing (WDM) circuit switched subnetwork. Based on these two data transport facilities, several topological and protocol solutions are available to the users. As a result, STARNET supports traffic of widely different speed and continuity characteristics. An ongoing experimental effort aimed at the realization of a STARNET prototype at the Optical Communication Research Laboratory of Stanford University is described. The prototype nodes are fiber distributed data interface (FDDI) and synchronous optical network (SONET) OC-48 data rate compatible.<<ETX>>

STARNET-E: a broadband wavelength-division multiplexed optical local-area network

We propose enhancements to STARNET, a previously proposed wavelength division multiplexed broadband optical local area network. STARNET offers the users both a medium- speed packet-switched ring network, and a high-speed circuit interconnection. The enhanced architecture, STARNET-E, improves performance in both the packet and the circuit interconnect sections over the previous version. Performance analysis of the STARNET-E packet network shows that this data transport facility can be upgraded to Gb/s total throughput with little added complexity with respect to the original STARNET. Moreover, we show that STARNET nodes can be enhanced to allow reconfigurable multihop topologies with little added optical hardware. The throughput of multihop distributed switching over a passive star physical topology in STARNET-E is compared to the throughput of an active centralized switch. STARNET-E offers to all nodes a Gb/s total throughput packet transport facility and a high speed circuit interconnect, simultaneously and independently. In addition, a node can trade the high speed circuit interconnect service for a multihop broadband packet network without the need for any added optical hardware.

Combined PSK/ASK modulation format for the STARNET WDM local-area network

STARNET is a coherent optical wavelength division multiplexed (WDM) local area network. In STARNET, the use of low level amplitude modulation of phase modulated light has been proposed to implement a packet-switched ring network in addition to a high speed circuit- switched network. To verify the feasibility and characterize the effects of amplitude shift- keyed (ASK) modulation on a phase shift-keyed (PSK) receiver, we have measured the sensitivity of a 1.244 Gb/s PSK synchronous heterodyne receiver in the presence of 125 Mb/s ASK modulation. The experiments show that the unmodified (i.e., designed for no ASK modulation) PSK receiver successfully operates with a bit error ratio less than 10-9 and maintains phase-lock in the presence of ASK modulation for ASK modulation indexes less than 0.5.

MultiGbit/s optical LAN utilizing a passive WDM star: toward an experimental prototype

STARNET is an optical broadband local area network based on a physical passive star topology intended for backbone applications. Over a single physical network, STARNET offers all users both a moderate-speed packet switched subnetwork and a reconfigurable high- speed (up to 2.5 Gbps) Wavelength Division Multiplexed (WDM) circuit switched subnetwork. Based on these two data transport facilities, several topological and protocol solutions are available to the users. As a result, STARNET supports traffic of widely different speed and continuity characteristics. This paper describes an ongoing experimental effort aimed at the realization of a STARNET prototype network at the Optical Communication Research Laboratory of Stanford University. The prototype nodes are FDDI data rate and format compatible in the packet switched subnetwork and currently use 8B/10B encoded data at a rate of 1.25 Gbps in the circuit switched subnetwork. The STARNET network serves high performance workstations running distributed multimedia applications, including video- conferencing. In this paper, the electronic hardware which interfaces the workstation to the STARNET optics is described. The moderate-speed interface uses an off-the-shelf FDDI-on- copper module to interface to the STARNET optics; a custom high-speed interface module provides fast packet switching (electronic) over the circuit switched (wavelength) subnetwork.