Token Ring Protocol Research Articles

Bounds for performance measures of token rings

In polling systems that have been studied in the literature, one usually asserts independent Poisson arrivals. This assumption is, however, unrealistic when dealing with many applications, e.g., local area networks (LANs) using token-ring protocols. The arrival processes there may be quite irregular, highly bursty, and correlated. We use the new approach for modeling such arrival streams proposed by Cruz (1991), to obtain strict upper bounds on several performance measures. It is based on characterizing the inputs by bounds on the average arrival rate and the burstiness, and is especially useful in describing the arrival streams that are filtered (policed) by leaky buckets. We first obtain bounds for the gated, exhaustive, and globally-gated service disciplines, and then consider timed token rings (such as the FDDI). The results for the first three disciplines improve the general bounds obtained by Altman, Foss, Riehl and Stidham (see Proceedings of the 14th International Teletraffic Congress, France, p.811-20, June 1994). We further obtain improved exponential bounds of the type introduced by Chang (see IEEE Trans. Automat. Contr., vol.34, no.5, p.913-31, 1994), and Yaron and Sidi (see ibid., vol.1, no.3, p.372-85, 1993) for the globally-gated discipline.

High-performance protocols for ring LAN and MAN computer networks

This paper presents an adaptive token release mechanism that can be used in both basic token ring protocols (e.g., IEEE 802.5) and timed token protocols (e.g., FDDI). The essence of the mechanism is to allow stations to share current state information that enables the token-holding station to decide whether to release the token or to keep it for another token-holding period. Simulation results show that using the adaptive token release mechanism, token ring protocols are able to support a large spectrum of real-time applications without sacrificing efficiency.

The multi-token ring network protocol

Abstract High speed networks require that bandwidth management be as less dependent on the medium propagation delay as possible. Token rings, although usually very efficient at high load, are less efficient at light and moderate loads, especially in the short packet environment. This paper proposes a solution to the token ring inefficiency under the aforementioned conditions: a medium access protocol using multiple tokens. The paper first shows how the medium access can be managed in a distributed way, using two tokens. The overhead is kept to a minimum. It is shown that the performance of this protocol is superior to that of the single-token ring protocol under light to medium loads, while it is slightly worse at higher loads. The protocol is then extended to an arbitrary number of tokens. It is shown that increasing the number of tokens improves the performance at light load, but degrades the performance at high load. This protocol is not just an improvement over the token ring protocol, but is a general suite of protocols of which the well known token ring is a special case.

Conventional and early token release scheduling models for the IEEE 802.5 token ring

We develop analyticalscheduling models for both the original IEEE 802.5 token ring protocol and a recent extension to the original protocol that allows early token release (ETR). A scheduling model is an abstraction that supports reasoning about the timing correctness of a given set of real-time messages scheduled on the network. Scheduling analysis of the original IEEE 802.5 token ring protocol has previously been discussed in Strosnider and Marchok (1989) and Pleinevaux (1992) in the context of improving responsiveness of soft deadline aperiodic messages. In contrast, this paper develops schedulability conditions for arbitrary periodic message sets. The main contributions of this work are: Scheduling models for both the original protocol and ETR protocol; comparison for maximum achievable utilizations for the two protocols; comparison between the original protocol and ETR from a schedulability viewpoint. We also demonstrate the utility of our scheduling models to select network operating parameters such as maximum packet size, and to quantify effects of parameters such as the number of stations, and network size on schedulability.

802.5 priority mechanism in hard real-time RMS applications

The 802.5 Token Ring protocol is firmly established as an international standard. In this research note, its priority mechanism is analysed in the context of real-time environments, and it is shown that although unable to implement a strict rate monotonic discipline, it is still schedulable if certain (proven) necessary and sufficient conditions, expressed in the form of inequalities, hold. These conditions also allow the treatment of problems related to coarse granularities and to mixed traffic.

A new token ring protocol and its performance for single and dual ring lan systems

AbstractThis paper presents a new protocol for token ring local computer networks and its performance for single and dual ring networks using simulation modelling. The proposed protocol is a modification of the IEEE 802·5 token ring standard. In this protocol, a station can start transmission if it receives a free token or a data packet passing its interface logic. Idle stations are skipped whenever there is at least one station that has a ready packet to transmit. This is achieved by using two of the reserved bits in the frame status (FS) field. The bits used are called transmission reservation bits (TR‐bits). The TR‐bits are reset by the sending station and set by the first station that has data to transmit during the round trip of the associated packet along the ring. It is found that the proposed modified token ring (MTR) protocol provides better throughput and delay performance for both the single and dual ring networks. The reduction in mean delay of the MTR as compared to the standard token ring (STR) reaches about 45 per cent under heavy traffic conditions. Moreover, it is found that the performance of the MTR decreases as the packet size increases but remains higher than the corresponding performance of the STR for both the single and dual ring networks. The MTR provides a maximum throughput improvement of about 6 per cent over the STR for both dual and single ring cases. Finally, the proposed protocol (MTR) is easy to implement, with no extra hardware and has low cost/performance characteristics.

A performance comparison of event calendar algorithms: An empirical approach

AbstractWe propose a suite of tests based on two‐state Markov chains for experimentally assessing the dynamic performance of a variety of simulation event calendar implementations. In contrast to previous studies based on the standard hold model for evaluation of performance statically, the proposed Markov hold model is more general and can be used to examine how different implementations respond dynamically to dependent sequences of insertion and deletion requests. The Markov hold model is used to conduct tests based on random, stressed, and correlated input sequences of requests, with performance measures including completion times, sensitivity to correlations, sensitivity to duplication, and efficiency of data‐handling. We apply these tests to fourteen different event calendar implementations. To demonstrate the utility of the proposed model, we also include a comparison of the event calendar algorithms on a token ring protocol with bursty Markovian packet‐traffic.

Specification and analysis of the FDDI MAC protocol using systems of communicating machines

A model designed for the specification of communication protocols called systems of communicating machines is used to specify the FDDI token ring protocol, and to analyse its safety and ‘liveness’ properties. This model specifies each node as a finite state machine which has a set of local variables. With each transition is an enabling predicate and action. The predicates determine whether transitions may be taken, and actions alter the variable values as the transition executes. Communication between nodes is through shared variables. Our contributions include the specification of the basic FDDI protocol using a formal description technique; the use of this specification to analyse the safety and liveness properties of the network; the extension of the formal model to include the timing of transitions; and confirmation of the timing properties of the protocol.

Isolating Problems in a Token-Ring Network

The basis for a very efficient network management implementation is found in the way the Token-Ring protocol works. Management reporting procedures are integrated into the Token-Ring data flow by being part of the idle running traffic in every ring.

Protocol for token ring local computer networks and its performance

A new modified token ring (MTR) protocol is presented. The performance of the new protocol is studied using simulation analysis and it is compared with the performance of the IEEE 802.5 standard token ring (STR) protocol. The results show that the MTR protocol provides shorter average packet delay and higher ring throughput than that of the STR protocol. A 45% reduction in the average packet delay is achieved by the MTR protocol over the STR protocol, under heavy traffic conditions.

FDDI- A LAN among MANS

FDDI (Fiber Distributed Data Interface) is a 100 Mbit/sec local area network (LAN) based on a token ring protocol operating over an optical fiber medium. Though not a metropolitan area network (MAN), FDDI can operate over distances normally considered as the province of MANs. With the addition of FDDI-II capabilities, and the newly defined mapping for FDDI over SONET, FDDI now offers MAN functionality for large organizations needing to provide integrated services over a widely based high performance private network. This paper updates earlier efforts on this subject, giving an up-to-date overview of FDDI, FDDI-II and SONET mapping. At the end of the paper a brief look at the possible future for FDDI technology is given.

The helical window token ring

An access rule for token ring local-area networks called the helical-window token-ring protocol is introduced. It features the use of a window that limits the allowable messages a token-holding station can send. With the window, the operation of the protocol approaches that of a central single-server queuing system in the sense that messages are delivered in near first-come-first-served order on a network-wide basis. The introduction of the window also makes analysis of the networks tractable. Exact analytical formulas for the capacity and for the mean, variance, and moment-generating function of the message waiting time are derived. Numerical simulation is used to verify the results. Comparisons with continuous polling systems show that the imposition of the windowed access rule can lead to significant reductions in the delay variance (at the cost of increasing the mean system time) when the traffic is heavy and/or the message transmission time is large with respect to the walk time of the ring.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Are priorities useful in an 802.5 token ring?

The IEEE standard 802.5 token ring protocol defines eight packet priorities. The intent is that high-priority packets should be delivered prior to low-priority packets. A series of simulations shows that this expected behavior occurs when there are very few network stations, very short data packets (but still long relative to ring latency), very short token hold times, and very high network loads. In the general case, priorities did not markedly influence packet delivery time. Use of the priority system generally resulted in more overhead and longer average packet delays than when all packets were carried as a single priority. The features of the protocol operation that are the cause of this increased delay and lack of priority discrimination are described mathematically. >

Cycle time properties of the FDDI token ring protocol: Kenneth C. Sevcik and Marjory J. Johnson: Computer Systems Research Institute, University of Toronto, Toronto, April 1986

Cycle time properties of the FDDI token ring protocol: Kenneth C. Sevcik and Marjory J. Johnson: Computer Systems Research Institute, University of Toronto, Toronto, April 1986

Proof that Timing Requirements of the FDDI Token Ring Protocol are Satisfied

The fiber distributed data interface (FDDI) is an ANSI draft proposed standard for a 100 Mbit/s fiber-optic token ring. The FDDI timed token access protocol provides dynamic adjustment of the load offered to the ring, with the goal of maintaining a specified token rotation time and of providing a guaranteed upper bound on time between successive arrivals of the token at a station. FDDI also provides automatic recovery when errors occur. The bound on time between successive token arrivals is guaranteed only if the token rotates quickly enough to satisfy timer requirements in each station when all ring resources are functioning properly. Otherwise, recovery would be initiated unnecessarily. The purpose of this paper is to prove that FDDI timing requirements are satisfied, i.e., the token rotates quickly enough to prevent initiation of recovery unless there is failure of a physical resource or unless the network management entity within a station initiates the recovery process.

Cycle Time Properties Of The FDDI Token Ring Protocol

The FDDI Token Ring Protocol controls communication over fiber optic rings with transmission rates in the range of 100 megabits per second. It is intended to give guaranteed response to time-critical messages by using a timed protocol, in which non-critical messages may be transmitted only if recent movement of the token among stations has been sufficiently fast relative to a target token rotation time (TTRT).

Lore of the token ring

Token-ring LANs defined by the IEEE 802.5 and American National Standards Institute X3T9.5 Committees are considered. The author addresses several myths surrounding token-ring networks and offers supporting technical evidence to the contrary. He discusses token-ring protocols, the star-wired configuration, ring access via tokens, multiplexing of ring connections, and the significant recovery mechanisms allowed by the ring.

Cycle time properties of the FDDI token ring protocol (extended abstract)

Communication technology now makes it possible to support high data transmission rates at relatively low cost. In particular, optical fiber can be used as the medium in local area networks with data rates in the range of 100 megabits per second. Unfortunately, local area network topologies and communication protocols that work well with lower speed media are not necessarily appropriate when the data transmission rate is scaled up by approximately an order of magnitude. Recognizing this fact, an ANSI sub-committee (ANSIX3T9) has been working for the past two years on a proposed standard for a token ring protocol tailored to a transmission medium with transmission rate in the 100 megabits per second range. The protocol is referred to as the FDDI (Fiber Distributed Data Interface) Token Ring protocol. The proposal for the standard is now quite mature and nearly stable.

Reliability mechanisms of the FDDI high bandwidth token ring protocol

Abstract The Fiber Distributed Data Interface (FDDI) is an ANSI draft proposed standard for a 100 megabit per second token ring using fiber optics as the transmission medium. The FDDI design represents an extensive effort to incorporate reliability mechanisms as an integral part of the design. These mechanisms provide fault detection and isolation functions, monitoring functions, and configuration functions. The purpose of this paper is to discuss these reliability mechanisms, and to compare and contrast them with reliability mechanisms which have been incorporated in other local area network architectures.

Distributed computation via active messages

An extension to the token ring protocol which allows a special type of arithmetic, called shift arithmetic, to be performed directly on the node's interfaces is proposed. The new protocol is based on an approach in which the communication channel and the interfaces form an environment in which simple commands can be executed. Each command operates on operands located at the interfaces, and places the result at the interface which initiated the command. The commands utilize the mandatory 1-bit delay of the token ring protocol to implement arithmetic and logical operations on the operands without further delay. The goal of this protocol is to enhance the performance of distributed algorithms on ring networks by performing many simple tasks in the lowest possible level. The authors show that this protocol is especially useful for load sharing in local area networks. Other potential application areas include parallel algorithms, distributed simulation, distributed operating systems, distributed databases and real-time computations.