Guaranteeing synchronous message deadlines with the timed token medium access control protocol

We study the problem of guaranteeing synchronous message deadlines in token ring networks where the timed token medium access control protocol is employed. Synchronous capacity, defined as the maximum time for which a node can transmit its synchronous messages every time it receives the token, is a key parameter in the control of synchronous message transmission. To ensure the transmission of synchronous messages before their deadlines, synchronous capacities must be properly allocated to individual nodes. We address the issue of appropriate allocation of the synchronous capacities. Several synchronous capacity allocation schemes are analyzed in terms of their ability to satisfy deadline constraints of synchronous messages. We show that an inappropriate allocation of the synchronous capacities could cause message deadlines to be missed even if the synchronous traffic is extremely low. We propose a scheme called the normalized proportional allocation scheme which can guarantee the synchronous message deadlines for synchronous traffic of up to 33 percent of available utilization. To date, no other synchronous capacity allocation scheme has been reported to achieve such substantial performance. Another major contribution of this paper is an extension to the previous work on the bounded token rotation time. We prove that the time elapsed between any consecutive visits to a particular node is bounded by upsilon TTRT, where TTRT is the target token rotation time set up at system initialization time. The previous result by Johnson and Sevcik is a special case where upsilon = 2. We use this result in the analysis of various synchronous allocation schemes. It can also be applied in other similar studies

Telemetry downlink interfaces and level-zero processing

The technical areas being investigated are as follows: (1) processing of space to ground data frames; (2) parallel architecture performance studies; and (3) parallel programming techniques. Additionally, the University administrative details and the technical liaison between New Mexico State University and Goddard Space Flight Center are addressed

A method for analyzing the performance aspects of the fault-tolerance mechanisms in FDDI

The ability of error recovery mechanisms to make the Fiber Distributed Data Interface (FDDI) satisfy real-time performance constraints in the presence of errors is analyzed. A complicating factor in these analyses is the rarity of the error occurrences, which makes direct simulation unattractive. Therefore, a fast simulation technique, called injection simulation, which makes it possible to analyze the performance of FDDI, including its fault tolerance behavior, was developed. The implementation of injection simulation for polling models of FDDI is discussed, along with simulation result

Optimal Guaranteed Services Timed Token (OGSTT) Media Access Control (MAC) Protocol for Networks That Support Hard Real-Time and Non Real-Time Traffic

In networks that support real-time traffic and non-real-time traffic over the same physical infrastructure, the challenge to the Media Access Control (MAC) protocol of such network is the ability to support  the different traffic without compromising quality of service (QoS) for any of them. Generally, timed-token MAC protocols group the diverse real-time traffic into one category and then dedicate certain portion of the available bandwidth to them. At the same time, some bandwidth are left unassigned but available to the non real-time traffic. The unassigned bandwidth, and in some cases, the unused bandwidth left by the real-time traffic are assigned to the non-real-time traffic on best effort basis. In this paper, Optimal Guaranteed Services Timed Token (OGSTT) MAC protocol is developed and analyzed. In order to provide better support for both real-time traffic and non-real-time on the same local area network, OGSTT employs the timed-token mechanisms in the Timely-Token protocol along with that of Budget Sharing Token (BuST) protocol. Some bounds on the behavior of OGSTT protocol are discussed along with the ability of OGSTT protocol to support real-time and non-real time traffic. In particular, the paper demonstrated that the performance achieved by OGSTT is better than the Timely-Token and BuST. Furthermore, OGSTT protocol can be incorporated into the Ethernet network to provide real-time performance guarantees to multimedia applications and hard and soft real-time traffic

Performance analysis of Gb/s WDM FDDI network

In this paper, we propose a time-token multi-Gb/s Wavelength Division Multiplexing Fibre Distributed Data Interface (WDM/FDDI) architecture and examine its throughput efficiency and delay under heavy load for different network configuration using discrete event simulator

Simulation analysis of FDDI network using NETWORK II.5 software package

In recent years, one of the most exciting advances in media has been the use of fiber optics in LANs. The bandwidth provided by Fiber Optic Technology has drastically increased the number of new applications that can be supported by communication networks. In order to support a variety of services, in 1986, the American National Standard Institute (ANSI) Accredited Standards Committee (ASC) X3, and the ASC X3T9.5 Task Group developed a new standard; the Fiber Distributed Data Interface (FDDI) [1]. This is a high speed (100 Mbps) optical communication network based on a token passing mode of operation. The Medium Access Control (MAC) Protocol selected for this network attempts to provide priority services, as well as bounded delay transmission for real time applications [2]. This thesis presents results for the Voice-Data performance of the Medium Access Control (MAC) protocol, selected for the FDDI network, using the NETWORK 11.5 [6] software package. This protocol can provide priority services to different types of traffic, as well as guarantee bounded delays for real-time applications. The effect of various system parameters on performance is investigated

Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)

An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined

Spacelab system analysis: A study of communications systems for advanced launch systems

An analysis of the required performance of internal avionics data bases for future launch vehicles is presented. Suitable local area networks that can service these requirements are determined

Static-Threshold-Limited on-Demand Guaranteed Service for Asynchronous Traffic in Timely-Token Protocol

In this paper, an improved Timely-Token protocol with enhanced best-effort service for improved capacity allocation to the asynchronous (that is, non real-time) traffic is proposed. Through analytical approach and the use of computer simulations, the improved Timely-Token protocol is compared with the existing Timely-Token protocol. In particular, if AT denotes a threshold value, then, when compared to the existing Timely-Token protocol, the improved protocol will allocate additional average of AT time units to the asynchronous traffic in every cycle