Token-passing Protocol Research Articles

The WICKPro protocol with the Packet Delivery Ratio metric

Wireless mesh networks (WMNs) with chain topologies are very useful in road and railroad transportation or in tunnel and mine applications. The proposed protocols for WMNs usually support best-effort traffic or some kind of Quality of Service (QoS). However, some applications such as remote-controlled machines in industrial control networks have hard real-time (HRT) requirements, i.e., strict deadlines. For this reason, this paper incorporates the Packet Delivery Ratio (PDR) metric into the WICKPro (WIreless Chain networK Protocol) protocol, a HRT protocol for WMNs with chain topologies which uses a token-passing approach. WICKPro is a Medium Access Control (MAC) protocol based on the ideas of the Timed-token protocol and the cyclic executive. The incorporation of the PDR metric lets calculate the needed time to be reserved where packet retransmissions can be accommodated while satisfying HRT traffic constraints. Moreover, the feasibility of using the PDR metric in a token-passing protocol is shown. Since WICKPro has been designed to work on top of IEEE 802.11, we made a testbed using commercial 802.11 wireless cards and compared the WICKPro’s performance with the 802.11 protocol and three specific protocols for WMNs with chain topologies.

Ripple: a wireless token-passing protocol for multi-hop wireless mesh networks

This work presents a wireless token-passing protocol, named Ripple, for wireless mesh networks (WMNs). In contrast to existing random-access approaches, Ripple uses a decentralized controlled-access approach to protect nodes from unintentional packet collisions and maximize the spatial reuse. The performance of Ripple under an error-free wireless channel was investigated and the accuracy of the analysis was verified by simulation. Simulation results also indicated that Ripple achieved throughput, stability, and QoS enhancement than that of 802.11 DCF under a highly loaded situation.

Ring stability of the PROFIBUS token-passing protocol over error-prone links

The PROFIBUS is a well-known and widely used fieldbus. On the medium access control layer, it employs a token-passing protocol where all active stations form a logical ring on top of a broadcast medium. This protocol is designed to deliver real-time data transmission services in harsh industrial environments. A necessary prerequisite for timeliness and quality of service is the ring membership stability of the logical ring in the presence of transmission errors, since only ring members are allowed to transmit data. In this paper, the ring membership stability under high error rates and using different error models is analyzed. The choice of the error behavior is in turn inspired by properties of possible future transmission technologies, e.g., wireless LANs. It is shown that the protocol has serious stability problems. To attack these problems, two changes to the protocol and its parameters are proposed, which can be implemented in a purely local manner. We show that they significantly improve ring stability.

Communication network protocol for real-time distributed control and its LSI implementation

A new token-passing mechanism, priority token passing, which features real-time access and fast detection and recovery of transmission errors, is discussed in detail in comparison with standard token-passing protocols, and its large-scale integration (LSI)-oriented design concept is described. Priority token passing includes only a small performance overhead, due to its switching functions, which can change network topology from ring to broadcast medium. A token-holding node passes the token to another node after determining the successor through priority comparison. Errors occurring during token passing can, thus, be detected and corrected simply and promptly. Priority token passing has a simple hardware implementation, requiring only small additions to the frame control circuitry, and has a small implementation overhead. The priority token-passing protocol and two other important network communication functions, dual ring network reconfiguration and high-level data link control (HDLC) normal response mode-based message transmission, are designed as a single finite-state machine, and implemented into a compact LSI chip. This integrated instrument network (IINET) chip provides complete network communication services and requires only three additional external electronic components for operation.

Multiaccess mesh (multimesh) networks

This paper introduces the multiaccess mesh (or multimesh) network. Stations are arranged in a two-dimensional (2-D) mesh in which each row and column functions as a conventional linear local-area network (LAN) or metropolitan-area network (MAN) subnetwork. Full connectivity is achieved by enabling stations to merge their row and column subnetworks, under the coordination of a merge control protocol. A two-dimensional token-passing protocol is considered, and a more complex protocol motivated by max-min fairness is also presented. Like conventional LANs and MANs, the multimesh requires no transit routing or store-and-forward buffering. The multimesh is a generalization of the token grid network. Using analysis and simulation, we study the capacity of multimeshes constructed of token rings and slotted rings, under uniform and nonuniform loads. A multimesh can support much higher throughput than conventional linear LAN and MAN networks with the same transmission hardware. Moreover, the multimesh capacity grows with the number of stations, We also present a healing mechanism that ensures full network connectivity regardless of the number of failed stations.

Implementation of a MAC-layer protocol (GIT-CSMA/CD) for industrial LAN's and its experimental performance

This paper describes the pilot implementation of a local area network by using a hybrid medium access control (MAC) layer protocol, called group implicit token-carrier sense multiple access with collision detection (GIT-CSMA/CD) developed for hard real-time industrial local area networks (LANs). This protocol outperforms standard CSMA/CD and token-passing protocols, as well as other hybrid protocols, in terms of mean and maximum packet delays versus throughput. Also, GIT-CSMA/CD offers bounded packet delay and a great degree of adaptation to the varying requirements imposed by the user applications. A seven-node pilot network was set up and its experimental performance evaluated. The implementation of the network node is based on the existing microcontroller technology (INTEL 80C3152 Communication Controller) and field programmable gate array (FPGA) logic (XILINX XC3190). The measurements carried out in real time on a 1-Mb/s LAN yielded reproducible results. The comparison between the experimental and the simulation results showed excellent agreement.

Design and evaluation of real-time communication for FieldBus-based manufacturing systems

It is well known that the ability to support predictable interprocess communication is of great significance to computer-integrated manufacturing and process control systems. In this paper, we propose a strategy for an industrial standard, the SP-50 FieldBus, to support both intracell and intercell real-time communications. We first describe our strategy in detail and show that it is compatible with the current FieldBus draft standard. Under our strategy, the capacity of each link is divided into two parts, The first part is managed by the local link active scheduler for intracell (intralink) communication. The second part is managed by a proposed global network manager for intercell (interlink) communication. By dividing the link capacity in this way, our strategy allows for fast local intracell connection establishment, while supporting global intercell connections. Using two examples, one for typical manufacturing systems and the other for multimedia networking, we also demonstrate the power and utility of the proposed strategy as compared to token-passing protocols.

An alternative to FDDI: DPMA and the Pretzel ring

This paper proposes an efficient, fair, and simple capacity-1 protocol replacing FDDI. In the recent years, two network protocols gained predominance in very fast local and in metropolitan area networks: FDDI and DQDB. The FDDI ring-protocol combination is well-suited for large local ("campus") area networks. However, for larger networks, FDDI users suffer excessive access delays, even under very light traffic. Moreover, FDDI achieves full capacity only in special circumstances, and heavy load is not a sufficient condition for achieving it. We propose a network topology that is very similar to the dual ring and a token-passing protocol that yield a true capacity-1 network even for modest values of the TTRT. Its additional properties include total fairness and very small access delays under light load. This makes the proposed protocol a reasonable option to use in combination with the dual counter-rotating ring. The proposed network should not be difficult to implement using standard FDDI components.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The timed-token protocol for real-time communications

The timed-token protocol is a token-passing protocol in which each node receives a guaranteed share of the network bandwidth. Partly because of this property, the timed-token protocol has been incorporated into a number of network standards, including the IEEE 802.4 token bus, the Fiber Distributed Data Interface (FDDI), and the Survivable Adaptable Fiber Optic Embedded Network (Safenet). Networks based on these standards are becoming increasingly popular in new generation real-time systems. In particular, the IEEE 802.4 standard is included in the Manufacturing Automation Protocol (MAP), which has been widely used in computer-integrated manufacturing and industrial applications. Meeting message deadlines requires proper control of medium access. In the timed-token protocol, access to the communication medium is controlled by a token that is passed among the nodes in a circular fashion. Messages are segregated into two separate classes: synchronous and asynchronous. Synchronous messages, used for real-time communication, can have deadline constraints and thus are given a guaranteed share of the network bandwidth. The authors focus on meeting the deadlines of synchronous messages. >

Multigigabit, Multichannel Lightwave Networks Using Subcarrier Multiplexing

A novel multigigabit, multichannel lightwave network is described which uses subcarrier multiplexing to place multiple information channels and a baseband control channel on a single optical carrier. The control channel uses an FDDI-like token-passing access protocol and a 100 Mb/s control channel to provide efficient access to many Gb/s of information. The subcarrier multiplexed network (SCM-NET) can simultaneously transport many forms of information including variable-length data-grams, ATM-cells, and connection-oriented video traffic. By channelizing the total throughput, the reduction in utilization efficiency caused by propagation delay between nodes is significantly improved relative to conventional single-channel gigabit networks.

Decentralized token-CSMA/CD protocol for integrated voice/data LANs

In this paper we propose a decentralized protocol for integrated voice and data local area networks. This protocol is based on a hybrid token-CSMA/CD protocol which combines all the merits of the CSMA/CD network and the token-passing network. We apply the hybrid protocol to voice and data individually, and offer two implicit tokens, one voice token and one data token, to achieve the priorities requirements. The voice transmission follows the token-passing protocol with a contention-resolution mechanism. It enforces a bounded delay to guarantee the real-time delivery for voice. This hybrid protocol will serve data of the low priority as fairly as best. To evaluate the protocol's performance, analytical formulations are derived. Numerical results are obtained for the throughput as well as the mean packet delay.

Local communication networks for industrial automation

The author presents a study of the physical and data link layers of the dynamic token-passing bus protocol. This protocol is a variant of the IEEE 802.4 token-passing bus protocol and can therefore be applied to communication systems which support industrial automation. Simulation results have been used for operational validation and extensive evaluation of the communication network's performance. The complex process of allocating a portion of the channel bandwidth to scheduling control, in a completely distributed fashion, has been investigated. The protocol is capable of efficient operation for the full range of channel utilization, while its dual-phase behaviour provides for a reliable and flexible channel assignment scheme. Thresholds have been determined for switching between the modes, and a hardware unit has been proposed which monitors the bus activities and, using existing signals, generates the switch-over command. Two recommendation for modifications of the existing 802.4 standard are also proposed which increase the reliability and reduce the overheads of the logical ring maintenance functions.

Personal computer communications on intrabuilding power line LAN's using CSMA with priority acknowledgements

Intrabuilding power lines provide a readily available and easily accessed network for personal computer (PC) communications within buildings. The use and performance of carrier-sense multiple access with priority acknowledgements (CSMA/PA) on such networks is described. The communication characteristics of intrabuilding power-line channels are summarized and found to suffer from highly variable and unpredictable signal-to-noise ratios and bit-error rates. The advantages of CSMA/PA relative to polling and token-passing access protocols are discussed. The architecture of a CSMA/PA implementation is described. The choice of the best data-link packet length is determined from throughput measurements to be approximately 1000 bits. Delay-throughput performance is measured at 1.2, 2.4, 4.8, and 9.6 kb/s using a phase-shift-keyed (PSK) spread-spectrum modem. Results are included for the potentially difficult problem of transmission across power phases. A discussion of results obtained and their implications for PC intrabuilding communications is also included. >

Optical fibre LANs for mixed data traffic

This paper begins with a short review of the implications of using optical fibre communications technology for LANs. Traffic characteristics and the access requirements of a wide range of devices are then described, followed by the consideration of channel access protocols for optical fibre LANs. A novel, adaptive, hybrid token passing-CSMA/CD protocol designed for use with an optical fibre LAN serving a mixed data traffic environment is discussed. Its performance is compared with that of a purely token-passing protocol, demonstrating a significant improvement for the hybrid with both symmetrically and asymmetrically distributed traffic loads.

Active star coupler based fiber-optic local area network

A 50-MBd active star fiber optical Iocal area network (LAN) and its optical combiner and mixing rod splitter are presented. The limited power budget and relatively large tapping losses of lightwave technology, which limit the use of fiber optics in tapped bus LAn topologies, are examined and proven tolerable in optical star topologies. The optical combiner and splitter, compononets necessary for such a network, have been fabricated and evaluated. The optical combiner, consisting, of a fiber bundle couled to a large-area p-i-n photodetector, and the mixing rod splitter, which had an insertion lodd of 19.8dB±1.4dB (including splitting loss), are shown to have suitable characteristics for the 50-MBd 32-node active optical star network. This star topology. proposed as an internetwork gateway which uses token-passing or polling protocol for packet switched data transmission, could be enhanced with wavelength-division multiplexing to provide both packet switched data and frequency division circuit switched real-time video and voice services network. Applications suggested for such a gateway or netwrok include health car information systems and factory automation.

Experiences with a Layered Approach to Local Area Network Design

The Nestar Plan 4000 network was designed using the ISO Open Systems Interconnection model. The Xerox Network Systems Internet Transport Protocols (XNS) were chosen for the network and transport layers, a token-passing protocol (Arcnet) for the physical and datalink layers, and existing Nestar server software for the highest layers. The physical and datalink layers are supported by a VLSI chip and their implementation was straightforward. In spite of their detailed specification, implementing the network and transport layers presented some unanticipated challenges. This paper discusses details of our experience in implementing the network with emphasis on the problems encountered and how they were solved.