William E. Stephens

Building autonomic systems via configuration

Large classes of autonomic (self-managing, self-healing) systems can be created by logically integrating simpler autonomic systems. The configuration method is widely used for such integration. However, there are few formalized tools in support of this method for specification, compilation, diagnosis, reasoning, and distributed provisioning. As a result, the practice of this method is very costly and can lead to security failures. This paper presents a technique called Service Grammar for building these tools based on a novel analysis of protocols and distributed algorithms in a domain of interest. The technique is illustrated in the context of a realistic adaptive virtual private network. We show how lower-layer adaptive protocols can be composed to create adaptive behavior at a higher layer.

Demonstration of a photonic space switch utilizing acousto-optic elements

A multicasting photonic space switch is proposed and demonstrated utilizing acousto-optic Bragg cells in a free-space active splitting, passive combining optical architecture. A 4 x 4 switch is demonstrated at optical wavelength X = 0.83pm using Te02 Bragg cells. Fiber-to-fiber insertion loss of 15 dB, crosstalk of -20 dB, extinction ratio of >30 dB, and polarization sensitivity of 0.8 dB has been measured. Feasibility of switch operation at 1.3 m is also shown for Te02. Although this design was fabricated as a 4x4, expansion to 14x 14 can be accommodated with modifications to the optical element design. Calculations indicate that a maximum switch size of 20 x 20 and an insertion loss of 11 dB is possible, with crosstalk and extinction ratios greater than 30 dB.

Ad hoc mobility protocol suite for the MOSAIC ATD

An ad hoc mobility protocol suite (AMPS) aimed at providing rapidly deployable, secure, robust IP-based communications among tactical mobile ad hoc nodes is presented in this paper. AMPS is an integrated networking solution for the MOSAIC ATD in that it provides the following capabilities: autoconfiguration, mobility management, unicast and multicast routing, reliable transport, quality of service, security and network visualization tools. This paper describes the architecture and implementation of AMPS for the MOSAIC ATD. Both laboratory and field experiments to measure AMPS functionality and performance were conducted in 2002 and 2003. This paper reports on the results of those experiments and their impact on future AMPS design and operation.

Line Code Selection for 155.52 Mb/s Data Transmission on Category 5 Cable Plant(002) 19960205

EMI/EMC is a dominant problem encountered in high bit-rate (>100 Mb/s) transmission over unshielded twisted-pair cable (UTP) which leads to a novel set of line-code dependent tradeoffs affecting transceiver and cable plant complexity. To understand the tradeoffs, the authors examined the factors affecting RF emissions and susceptibility in both trellis-configured cable plant models and installed cable plant. An analytical model is presented that describes mode conversion by discontinuities in multi-pair UTP cable plant. Termination of the three dominant propagating modes produces consistently lower radiated emissions than other standard cable termination procedures. Cable plant parameters which predict good transmission do not assure satisfactory EMI performance. Radiated emissions from the trellis model occur in broad bands at 43, 53, 60, 70, and 80 MHz, and show a positive correlation with the transmit signal spectrum. For a given transmit level at 155 Mb/s, the emissions with MLT3 and BPR1 were 8-13 dB (10 dB typ) and 4-20 dB (13 dB typ) below NRZ levels, respectively. The authors also compared the performance of NRZ, MLT3, BPR1, and BPR4 line codes in an experimental 155 Mb/s link with 100 m of UTP5 by measuring the BER sensitivity to both injected noise and pseudo-random data sequence length. When the measured receiver penalty associated with three levels is included, MLT3, BPR1, and BPR4 offer 5-15 dB better performance over NRZ at 155 Mb/s, although implementation complexity is greater.

Terabit-per second throughput switches for broadband central offices: an overview

The design of a broadband central office (CO) switch based on the SONET standard and the asynchronous transfer mode (ATM) protocol is addressed. An overview is given of the next generation switch (NGS), which has been proposed as a functional architecture for broadband networks and switching systems. The NGS consists of a number of different functional modules (interface, control, operations, service, and fabric), interconnected by open interfaces, that together form a high-speed large-throughput switching system. The interface modules and fabric modules, which embody some of the more difficult technological problems encountered in realizing terabit-per-second switches, are examined in detail.<<ETX>>

Network architecture for mission critical communications using LEO satellites

Use of Low Earth Orbit (LEO) satellite networks is a promising approach for global mission communications in view of their low delay and bit error characteristics. This paper describes the network architecture for an LEO environment where payloads have severe size, weight, and power (SWaP) constraints. In this architecture, payloads perform adaptive Layer 2 switching using routes computed by the central network operations center in the ground. Routes are computed considering traffic bandwidth, priority, and duration requirements, and time deterministic network topology changes. If necessary, lower priority traffic is preempted to accommodate higher priority traffic. Based on the routes computed for different snapshots, the planning system generates forwarding rules for payloads and uploads them via management centers that are deployed in different geographical locations in the ground. The architecture employs a distributed management scheme that reduces latency of critical management data such as alarms while avoiding the use of crosslinks for noncritical management communication.

MOSAIC ad hoc mobility protocol suite (AMPS) enhancements

The multifunctional on-the-move secure adaptive integrated communications (MOSAIC) ad hoc mobility protocol suite (AMPS) is designed to provide rapidly deployable, secure, robust IP-based communications among tactical mobile ad hoc nodes. AMPS is an integrated networking solution It combines several important capabilities: autoconfiguration, mobility management, unicast and multicast routing, reliable transport, quality of service, security and network visualization tools. These technologies were successfully tested in a field demonstration in 2003. Since then several enhancements have been made to improve the functionality, scalability and robustness of AMPS. This paper describes these enhancements.

DiffServ QoS and OLSR MANET Outdoor Demonstration

The CECOM MOSAIC ATD encompasses an integrated set of diverse technologies to demonstrate rapidly deployable, secure, robust, assured-QoS communications among mobile ad hoc nodes. The assured IP QoS technology solution integrates DiffServ based QoS resource management with centralized admission control over a dynamic tactical network environment. We describe an outdoor demonstration of our QoS technology prototype over an on-the-move MANET running OLSR. This demonstration does not include IP mobility support, however provides an alternate route between the ad hoc nodes through the use of two distinct wireless networks. The demonstration exhibits route changes between single and multiple IP hops as the nodes drive, and shows handoff between wireless networks as they move out of range of one radio network to the other. We summarize our observations and empirical performance results for real-time traffic

A toolkit for building secure, fault-tolerant virtual private networks

Dynamic coalition networks connect multiple administrative domains. The domains have a need to communicate, but have limited mutual trust. To establish communication services, these networks must be configured consistently with respect to global service requirements and security policies. The configuration must also be done in a way that respects the autonomy of the separate domains. Commercial network configuration tools do not provide sufficient functionality for this purpose. This document outlines a toolkit for solving these problems and reports on its deployment over a wide area network between Telcordia Technologies and BBNs TIC.