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.     

Security Attack Safe Mobile and Cloud-based One-time Password Tokens Using Rubbing Encryption Algorithm

One-time Password (OTP) Token has become one of the main stream security products during the past few years. OTP Token can automatically generate a random password. It is especially popular to be used with the Two-factor Authentication (2FA) system. OTP Token has proliferated into many different form factors such as standalone token, PC, PDA, cellular phone and Cloud-based token. But most of the implementation has their short comings with high token cost, not easy to carry and high supporting or deployment cost. Certain implementations may also compromise the network security when the token is lost or stolen. Moreover, most of the tokens can be broken-in by Man-in-the-Middle Seed-tracing and Shoulder-surfing security attacks. To overcome such aforementioned issues, we propose a secure encryption algorithm – Rubbing Encryption Algorithm (REAL). We use REAL to implement a Mobile-based and a Cloud-based OTP Token as design examples. Both of them are of high security level, lower total token cost and can resist the aforementioned security attacks as well.     

Traffic Analysis of a Token Ring PBX

A new approximation is described for the calculation of the transmission delay distribution experienced by voice subscribers connected to a token ring PBX. Together with simulation, the new technique is used to explore the dependence of delays to transmission on ring latency, voice packet length, and number of active subscribers for a 20 Mbit/s ring. Transmission delays are found to be relatively insensitive to the exact values of ring latency and voice packet length for the systems studied. The overall time between the generation and replay of speech samples is determined primarily by the voice packet length, and the use of short packets is recommended.     

一种多信道的分簇式短波令牌协议

传统的短波令牌协议( HFTP)调度方式单一,在没有数据传送时,信道资源会被各节点间的令牌传递所占用,且令牌在通信质量较差时易丢失。基于此,提出一种多信道的分簇式短波令牌协议( CHFTP),通过以通信质量评估为标准的分簇算法和基于预约的动态令牌调度,减小了令牌丢失的概率和令牌传递、处理的开销,并给出了仿真分析。仿真结果表明,该协议的端到端平均时延和网络吞吐量明显优于短波令牌协议, CHFTP 的平均时延最多可减少75%,网络吞吐量最多可增加66.7%,适合在短波通信网络中使用。     

A novel fault tolerant token ring network

Token Ring Networks have gained popularity due to their simplicity and ease of maintenance. However, the functioning of the entire network is dependent on the well being of an entity called “token”. The network ceases to function if the token is lost. There are algorithms suggested for improving the fault tolerant capabilities of the network with respect to the token.This paper proposes an algorithm to achieve fault tolerance. The algorithm is implemented on a simulated token ring network.     

A 200 Mbit/s Synchronous TDM Loop Optical LAN Suitable for Multiservice Integration

This paper describes a 200 Mbit/s multiservice optical local area network (LAN) using a synchronous TDM loop structure. The LAN consists of a central supervisory node and multiple service nodes connected by an optical fiber loop. Each service node supports communication channels which have access to allocated time slots in TDM frames continuously circulating on the loop. Multiple independent communication paths of various speeds up to 140 Mbits/s and various modes including point-to-point, ring, and multicast, can be provided between the channels on the loop. The ring will be useful to support ring networks, such as a token ring. The structure of this LAN is quite suitable for integration of multiple services, including video, image, data, and voice, since each service can independently choose its own speed, access method, and mode. In this development, various LSI-based high-speed hardware technologies including compact E/O and O/E modules, GaAs 4 × 4 matrix switch LSI's, and high-speed TDM-processor LSI's, which are versatilely applicable to high-speed LAN's ranging from 100 Mbits/s up to 560 Mbits/s, have been successfully introduced and compact LAN equipment has been obtained. This paper deals mainly with the system and hardware structure of this LAN, together with high-speed hardware technologies. An outline of firmware and network operation, and an application example are also described.     

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

This 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.     

无线动态令牌协议及性能分析

 本文在无线令牌环协议(WTRP)的基础上,提出了一种无线动态令牌协议(WDTP),以解决其网络拓扑适应能力差和管理控制复杂的问题.本文首先介绍了WDTP协议的工作原理,然后详细阐述了令牌的动态传递算法、子网的建立过程和令牌的管理维护技术,对WDTP协议和WTRP协议的性能进行了分析比较,并通过模拟仿真比较了两种协议对网络拓扑结构的适应能力.仿真结果表明,WDTP具有良好的网络拓扑适应能力,并因此提高了频率资源的利用率.     

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     

VTP-CSMA: A Virtual Token Passing Approach for Real-Time Communication in IEEE 802.11 Wireless Networks

Currently, there is a trend towards the implementation of industrial communication systems using wireless networks. However, keeping up with the timing constraints of real-time traffic in wireless environments is a hard task. The main reason is that real-time devices must share the same communication medium with timing unconstrained devices. The VTP-CSMA architecture has been proposed to deal with this problem. It considers an unified wireless system in one frequency band, where the communication bandwidth is shared by real-time and non-real-time communicating devices. The proposed architecture is based on a virtual token passing (VTP) procedure that circulates a virtual token among real-time devices. This virtual token is complemented by an underlying traffic separation mechanism that prioritizes the real-time traffic over the non-real-time traffic. This is one of the most innovative aspects of the proposed architecture, as most part of real-time communication approaches are not able to handle timing unconstrained traffic sharing the same communication medium. A ring management procedure for the VTP-CSMA architecture is also proposed, allowing real-time stations to adequately join/leave the virtual ring.     

FDDI: current issues and future plans

Fiber Distributed Data Interface (FDDI), a set of standards developed by the American National Standards Institute (ANSI) X3T9.5 Task Group, is reviewed. The timed token access method, used to share the medium among stations in this 100-Mbit/s local area network (LAN), differs from the traditional token access method in that the time for the token to walk around the ring is accurately measured by each station and used to determine the usability of the token. FDDI-II, which provides support for isochronous service in addition to the asynchronous and synchronous service provided by FDDI, the media-dependent physical layer (PMD) standard called low-cost fiber PMD (LCF-PMD), and the implementation of FDDI on the synchronous optical network (SONET) are discussed     

The token grid network

An overwhelming majority of local and metropolitan area network products (LANs and MANs) are based upon linear topologies such as buses and rings. Such networks are economical for high speed operation since the station interfaces are simple and require very little transit buffering. However because of their linear structure, the total throughput is restricted by the transmission rate of the media access channels. In the paper, a token grid network is introduced where media access is performed over a two-dimensional mesh. In the resulting system, each station is two-connected and has the same transmission hardware and small station latency as in a dual token ring. In the token grid however, the total system throughput may be many factors larger than that which is possible in a dual token ring. In a large √N×√N network, the uniform load capacity is approximately √N/2 times that of an N station dual token ring. In addition, the token grid can take advantage of communities-of-interest amongst the stations. It is possible to implement the system in such a way as to achieve robust operation in the presence of station and link failures     

Exact Results for Nonsymmetric Token Ring Systems

This paper derives exact results for a token ring system with exhaustive or gated service. There areNnodes on the ring and control is passed sequentially from one to the next. Messages with random lengths arrive at each node and are placed on the ring when the control arrives at that node. Exhaustive service means that the queue at a node is empty before the token is released and gated means that only those messages in the queue at the arrival of the token are served at that cycle. Generating function recursions for the terminal service time (the total sojourn time of a token at a node) and, from this, joint cycle and intervisit times are derived. Using known results relating the marginal generating functions of the waiting time and the cycle and intervisit time, it is shown that theNmean waiting times at the nodes require the solution ofN(N - 1)and N²equations for the exhaustive and gated cases, respectively. The arrival processes are assumed to be Poisson with different rates and the service processes are general and different at each node. In addition the token overhead is allowed to have an arbitrary but independent distribution at each node. Explicit, simply programmed equations are given. It is shown, arguing from the form of the equations, that there is a conservation law in effect in this system. If the nodal mean waiting times are weighted by the relative intensity, defined here as the intensity weighted mean, then the sum takes on a particularly simple form and is independent of the placement of the nodes on the ring. When the service means at each node are equal, this quantity is just the system mean waiting time.     

Transmission experiments through 101 km and 84 km of single-mode fibre at 274 Mbit/s and 420 Mbit/s

Four transmission experiments through low-loss single-mode optical fibre at 1.3 ?m have been performed at 274 Mbit/s and 420 Mbit/s with different objectives. The first demonstrates transmission through 101 km of single-mode fibre at 274 Mbit/s with negligible dispersion penalty. The second experiment at 274 Mbit/s and 84 km uses only components suitable for use in an undersea cable system. Two additional experiments, both at 420 Mbit/s, accomplish a bitrate × distance product of 35 GHzkm with 84 km of fibre and show no dispersion penalty with 63 km and 2.4 ps/km nm dispersion.     

300Mbit/s串行高速数据的可靠接收结构

针对高速串行数据可靠接收问题,设计了一种高速串行接收电路结构。对比以往文献中的电路,它的适应条件更加宽松,同时性能提高了50%。经过软件仿真和硬件实测,它能在高达310Mbit/s的串行数据速率下稳定工作。这在实际高速数据传输系统中具有广泛的应用价值。     

A scalable and energy‐efficient MAC protocol for sensor and actor networks

A scalable energy‐efficient MAC protocol is proposed for wireless sensor and actor networks (WSAN) to improve the network performance. Actor's placement has computed using midpoint K‐mean technique. These actors perform as the cluster heads and collect the information from its members. Cluster head computes the shortest path to all of its cluster members. Further, it divides the cluster into multiple subtrees and assigns a noninterference channel to every subtree. A token is assigned to each subtree for intracluster communication. Token handling and token processing mechanisms are proposed to transfer token from one node to next eligible node. Finally, a throughput‐based channel selection mechanism has proposed for actor‐actor communication. The proposed protocol is simulated in NS2 and compared with its competitive MAC protocols. The results describe that the existing protocols are out beaten by the proposed mechanism.     

Lookahead Network

This paper formalizes and extends a tree-based local area network, called the lookahead network, proposed by Lipovski, Goyal, and Malek. The leaf nodes in the network are workstations, and the nonleaf nodes consist of pure combinational logic used in carry lookahead circuits of binary adders. Any of the ring or bus access protocols (token passing, contention, etc.) can be used on this network. The first objective of this paper is to give a formal definition of the lookahead logic and show that it can be operated in either a bus or a ring mode. The advantage of using the lookahead logic is that it makes the network operation fail-soft, and since this logic is recursively defined, it simplifies network installation, expansion, and partitioning procedures. The second objective of this paper is to define a new round-robin access protocol on the lookahead network, which has much better throughputdelay characteristics than that of a token ring when the number of active nodes on the network is increased and/or the transmission speed is increased, and/or the average packet size is decreased. Moreover, this new protocol can implement a message-based priority scheme, which makes it useful in integrated voice and data networks.     

An Experimental 800 Mbit/s Four-Level Repeater Compatible with the 60 MHz Analog System

The design and performance of an experimental 800 Mbit/s repeater for four-level digital transmission over a coaxial cable is described in this paper. The 800 Mbit/s digital system exceeds the 60 MHz analog system, both in capacity and in economy. The repeater is designed to operate in repeater housings located at 1.6 km maximum spacing to be compatible with the 60 MHz analog sytsem. A nonredundant four-level line code has been employed, using a newly developed quantized feedback dc restoration technique. The most important item in realizing the high-speed multilevel repeater is the reduction of intersymbol interference. A simple quantized feedback scheme and an adjustable three-tap transversal equalizer have been used to compensate for intersymbol interference. The experimental repeater has been tested for 1.1-1.7 km repeater spacings using 2.6/9.5 mm coaxial cable. The results show that an 800 Mbit/s repeater with 1.6 km maximum repeater spacing is feasible.     

Surface-acoustic-wave multiplexing techniques

Two approaches to frequency division multiplexing using SAW devices are described. The first one uses a 9-channel filter array, where the signal combining and splitting is performed using wide-band power splitters. Two of these filter arrays were used in a data link, with data rates up to 7.5 Mbit/s for a total data rate of 67.5 Mbit/s. The second approach uses offset multistrip couplers to channel a wide-band signal into various narrow-band outputs according to frequency. Consequently, this approach exhibits lower insertion loss and is especially suitable for a large number of channels. An 8-channel MSC multiplexer has been constructed with less than 10-dB insertion loss.     

Computation of the Variance of the Waiting Time for Token Rings

The main new result in this paper is a simple expression for the variance of the waiting time for a token ring with an infinite number of stations, nonsymmetric Poisson traffic, deterministic ring delays, and virtually identical service distributions. These results can be considered as an approximation to the large ring where no individual station dominates the traffic. In the process, the exact equations for obtaining the variance of the waiting time for arbitrary traffics and service densities are found. In general, if there arennonsymmetric stations, about n³equations need to be solved.