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     

An optimal synchronous bandwidth allocation scheme for guaranteeingsynchronous message deadlines with the timed-token MAC protocol

This paper investigates the inherent timing properties of the timed-token medium access control (MAC) protocol necessary to guarantee synchronous message deadlines in a timed token ring network such as, fiber distributed data interface (FDDI), where the timed-token MAC protocol is employed. As a result, an exact upper bound, tighter than previously published, on the elapse time between any number of successive token arrivals at a particular node has been derived. Based on the exact protocol timing property, an optimal synchronous bandwidth allocation (SBA) scheme named enhanced MCA (EMCA) for guaranteeing synchronous messages with deadlines equal to periods in length is proposed. This scheme is an enhancement on the previously published MCA scheme     

Performance Evaluation of Wireless Controller Area Network (WCAN) Using Token Frame Scheme

In this paper, a proposed new wireless protocol so-called wireless controller area network is introduced. WCAN is an adaptation of its wired cousin, controller area network protocol. The proposed WCAN uses token frame scheme in providing channel access to nodes in the system. This token frame method follows the example used in wireless token ring protocol which is a wireless network protocol that reduces the number of retransmissions as a result of collisions. This scheme based on CAN protocol allows nodes to share a common broadcast channel by taking turns in transmitting upon receiving the token frame that circulates around the network for a specified amount of time. The token frame allows nodes to access the network one at a time, giving ‘fair’ chance to all nodes instead of competing against one another. This method provides high throughput in a bounded latency environment. The proposed WCAN protocol has been developed and simulated by means of QualNet simulator. The performances of this proposed protocol are evaluated from the perspective of throughput, end-to-end delay and packet delivery ratio, and are compared against the IEEE 802.11 protocol. Simulation results show that the proposed WCAN outperforms IEEE 802.11 based protocol by 62.5 % in terms of throughput with increasing network size. Also, it shows an improvement of 6 % compared to IEEE 802.11 standard at a higher data interval rate.     

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     

ISO 8802/5 token ring local-area networks

Token ring networks are the second most commonly used type of local-area network (LAN). The second version of the formal token ring multiple access mechanism, ISO 8802/5, was released in late 1995 and this rationalised many of the new developments, e.g. the 16 Mbit/s solutions. The latest innovations are the full duplex dedicated token ring and the development of a 100 Mbit/s high-speed token ring solution. To many people's surprise there is an extensive legacy of token ring installations and the latest innovations, such as token ring switching, are an attempt to maintain and support this significant market presence. Token ring is designed to provide high throughput under heavy loads (something which is normally impossible for Ethernet to sustain) but in most cases it is used in typical office environments where there is infrequent occurrence of heavy loads     

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.     

Mixed time-constrained and non-time-constrained communications inlocal area networks

It is well known that some time-token medium access protocols for local area networks (LANs) like the IEEE 802.4 token bus and the FDDI token ring can guarantee the medium access delay for time-constrained packets. However, a problem which has been largely overlooked is how these protocols can be made to provide a maximum throughput for nontime-constrained packets while guaranteeing the delay bound of time-constrained packets. The authors first show how the parameters of the IEEE 802.4 token bus and the FDDI token ring can be set to solve the above problem. Then, they design a new timer mechanism for the timed-token protocols which provides the highest guaranteed throughput of nontime-constrained packets among a set of medium access protocols called the token passing protocol, to which most of the existing non-contention LAN protocols belong. They present numerical examples to compare different protocols, all of which have shown the superiority of the proposed protocol to the others     

Design and performance comparison of multiple-token based MAC protocols for optical burst switched ring networks

Optical burst switching (OBS) has been proposed as a new optical switching paradigm for the next generation Internet due to its flexibility and feasibility compared to OCS and OPS. Moreover, serving as a backbone that interconnects a number of access networks, OBS ring topologies have been a good choice for solving the current metro gap problem between core network and access network owning to its simplicity and scalability. In this paper, we provide an insight into the OBS ring network that consists of nodes using TT–TR (Tunable Transmitter–Tunable Receiver). The node architectures with TT–TR may make efficient use of network resources even though traffic pattern, such as IP traffic with self-similarity dynamically change, and can support good expandability. However, all nodes share the limited network resources. This may result in contention such as wavelength contention and transceiver contention leading to burst loss. In order to use the shared network resources fairly and efficiently as well as reducing the resource contention, we focus on the design of medium access control (MAC) protocols based on multiple tokens. Each token is allocated to one wavelength to denote the accessibility of that wavelength, i.e., once the token is captured, the corresponding wavelength can be used to transmit a burst. As tokens hold the key for using wavelengths to transmit bursts, token management including the token release time is crucial in the proposed MAC protocols. Thus, two kinds of multiple-token based MAC protocols with different token release times are proposed: token release after transmitting burst (TRTB) and token release after transmitting control header (TRTC). Each of them is classified into two schemes called TRTB/TRR and TRTB/RCA and correspondingly TRTC/TRR and TRTC/ RCA. RCA stands for receive collision avoidance. The target is to increase the performance while reducing the processing overhead at each node. The performance of the TRTB and TRTC protocols are evaluated and compared in terms of queuing delay, burst loss rate, and channel utilization by OPNET simulation. The effects of various design parameters are also investigated through simulation in order to evaluate their scalability. In all the proposed schemes, tokens are just used to denote the accessibility of each wavelength. Finally, as an alternative, we also propose a new scheme based on the TRTC protocol called TRTC/CAT (collision avoidance by tokens) to avoid contention by using tokens.

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.     

A Study on Adaptive Time Token Priority-Based Queuing Scheme

Several famous priority-based queuing schemes operated in a gateway to support differentiated services among internet traffic. Examining packet forwarding operations in these queueing schemes, they only support a priority-based service either in a packet enqueuing process or in a packet dequeuing process. If a queuing scheme can support priority-based services in both packet enqueuing/dequeuing processes; it would enhance differentiated service performance for internet traffic. This study proposes a priority-based queuing scheme with an adaptive time token allotment measure to support a differentiated packet forwarding process for different types of IP traffic both in packet enqueuing/dequeuing processes. Depending on packet sizes and packet forwarding priorities of IP traffic, the proposed queuing scheme assigns fix and adaptive time token thresholds dynamically to logical queuing buffers separately. With assigned time tokens, logical queuing buffers allow arrival IP packets to be enqueued in a differentiated way. Moreover, the proposed queuing scheme uses a transferred WRR dequeuing measure to enhance a differentiated packet forwarding process. The simulation results show that the proposed queuing scheme supports a differentiated packet forwarding process for different types of IP traffic. The differentiated packet forwarding performance supported by the proposed scheme is close to the IETF DiffServ scheme; this result shows that the proposed scheme can support differentiated packet forwarding performance for different types of IP traffic with a lower operation cost.     

Setting target rotation times in an IEEE token bus network

The IEEE standard 802.4 token bus protocol requires each network station to implement a synchronous (highest priority) message class, and permits a station to implement three lower priority classes: urgent asynchronous, normal asynchronous, and time available. Each of the lower three priorities (called access classes) is assigned a target token rotation time that limits the amount of time that a station can use to service lower priority traffic. A formulation of the problem is presented in which messages are transmitted from an access class as long as network throughput remains below a user-specified threshold. Formulas are derived that transform this priority scheme, based on network throughput limits, into the proper target rotation time settings that the token bus protocol actually requires. The analytical model is compared with a computer simulation of the token bus protocol and shows close agreement     

A token circulation scheme for code assignment and cooperative transmission scheduling in CDMA-based UAV ad hoc networks

Code division multiple access (CDMA) ad hoc networks have been considered a promising multiple-channel networking architecture for connecting tactical platforms in battle fields. In this paper we consider a network of a swarm of unmanned aerial vehicles (UAVs) that are used in a tactical surveillance mission. The UAVs are assumed to have multiuser detection capability and form a CDMA-based ad hoc network. A token circulation scheme is proposed to conduct functions required at the medium access control layer including detection of hidden/lost neighbors, code assignment and schedule-based cooperative transmission scheduling. In the proposed scheme, a token continuously circulates around the network based on the “receive-forward” module. Through circulation of the token, each UAV can detect its hidden and/or lost neighbors in near real-time, assign codes enabling the spatial reuse of code channels without incurring code collision, and schedule data transmissions in a cooperative and distributed manner. In addition, the proposed scheme is able to take advantage of multiuser detection functionality and allows for simultaneous transmissions from multiple transmitters to a same receiver. The performance of the proposed token circulation scheme is evaluated, both analytically and through simulations. It is shown that the latency of the token is at most linearly proportional to the network size, and the average delay of a data packet increases with either the packet generation rate or the network size. The results also show that the proposed token circulation scheme is suitable for large-scale CDMA-based UAV ad hoc networks with even heavy network traffic load.     

ATM LAN emulation

Many of the most common protocols at layers two (media access), three (network), and above expect to operate over broadcast media such as IEEE 802.3/Ethernet or IEEE 802.5/token ring. LAN emulation provides a widely applicable means for transitioning these protocols to the connection-oriented ATM environment. A combination of centralized and distributed intelligence allows a star-plus-mesh topology of ATM virtual circuits to emulate broadcast media, while providing most of the advantages of connection-oriented media     

Comparative performance of voice/data local area networks

Using simulation, a network-independent framework compares the performance of contention-based Ethernet and two contention-free round-robin schemes, namely Expressnet and the IEEE 802.4 token bus. Two priority mechanisms for voice/data traffic on round-robin networks are studied: the alternating-rounds mechanism of the Expressnet, and the token rotation timer mechanism of the token bus, which restricts access rights based on the time taken for a token to make one round. It is shown that the deterministic schemes almost always perform better than the contention-based scheme. Design issues such as the choice of minimum voice packet length, priority parameters, and voice encoding rate are investigated. An important aspect that is noted is the accurate characterization of performance over a wide region of the design space of voice/data networks     

Contention protocols for ring networks with large bandwidth-delay products

As the bandwidth-delay product of ring networks increases, conventional access protocols, such as the gated token protocol, become less efficient. We propose overcoming this problem with contention-based access protocols. We discuss the necessary properties of any contention ring access protocol and present two specific proposals. Some simple analysis and simulation is done to determine the performance of these protocols. Our protocols are shown to have better end-to-end delay than a gated token protocol. We also simulate another contention protocol called the hybrid protocol, proposed by Bhargava, et al. It is shown that the simple protocols described in this paper have performance comparable to that of the more complex hybrid protocol on networks with high bandwidth-delay products.     

Secure and efficient token based roaming authentication scheme for space-earth integration network

Aiming at the problem of prolongation and instability of satellite and terrestrial physical communication links in the space-earth integration network,a two-way token based roaming authentication scheme was proposed.The scheme used the characteristics of the computing capability of the satellite nodes in the network to advance the user authentication process from the network control center (NCC) to the access satellite.The satellite directly verified the token issued by the NCC to verify the user's identity.At the same time,the token mechanism based on the one-way accumulator achieved the user's dynamic join,lightweight user self-service customization and billing,and the introduction of Bloom Filter enabled effective user revocation and malicious access management.Compared with the existing scheme,the scheme can guarantee the security of roaming authentication and significantly reduce the calculation and communication overhead of the authentication and key negotiation process.     

Improved priority access, bandwidth allocation and traffic scheduling for DOCSIS cable networks

The Data Over Cable Service Interface Specifications (DOCSIS) is intended to support IP flows over HFC (hybrid fiber/coax) networks with significantly higher data rates than analog modems and Integrated Service Digital Network (ISDN) links for high quality audio, video and interactive services. To support quality-of-service (QoS) for such applications, it is important for HFC networks to provide effective media access and traffic scheduling mechanisms. In this paper, we first present a multilevel priority collision resolution scheme with adaptive contention window adjustment. The proposed collision resolution scheme separates and resolves collisions for different traffic priority classes (such as delay-sensitive and best effort streams), thus achieving the capability for preemptive priorities. Second, a novel MAC (media access control) scheduling mechanism and a new bandwidth allocation scheme are proposed to support multimedia traffic over DOCSIS-compliant cable networks. It is shown through simulation results that throughput and delay performance have been improved for the transmission of real-time VBR (variable bit rate) traffic as compared to current DOCSIS specifications.     

A 100% efficient media-access protocol for multichannel LAN

This article introduces a slotted protocol for multi-user access to a LAN over parallel OR-type channels. An OR-type channel is defined as a digital communication channel such that, when a bit signal is injected into the channel, the channel content m at the bit position becomes logically ORed with the injected bit. The protocol applies a dynamic coding scheme to achieve 100% channel efficiency in the sense that, in each transmission session, an intended messages, or at least as many as the number of channels, are successfully broadcast. Message reception is through decoding from the OR composition of user injected bits. The coding scheme is a substitute for such approaches as slot reservation, permission token, and collision resolution that are used in most media access protocols     

Selection of timed token protocol parameters to guarantee messagedeadlines

Networks that use the timed token protocol (such as the 100 Mbit/s FDDI network) are well suited for real-time applications because they guarantee, to each node, an average bandwidth and a bounded access time to the communication network. This guarantee is necessary but not sufficient for the timely delivery of deadline-constrained messages; protocol parameters must be carefully selected to ensure that these messages meet their deadlines. This paper addresses the issue of selecting the protocol parameters TTRT (target token rotation time) and the synchronous capacities assigned to each node. The objective is to guarantee that each synchronous message is transmitted before its deadline. An upper bound is derived on the worst case achievable utilization (WCAU) of any parameter selection scheme. The WCAU of a scheme is defined as the maximum utilization U such that the scheme guarantees all synchronous messages as long as their utilization is less than U. An algorithm for selecting the above parameters is proposed, The algorithm is shown to have a WCAU that is very close to the upper bound     

Simple Approximations for Token Rings

Recently, a conservation law for the waiting times at a token ring has been derived. This conservation law is used here to develop simple approximations to the waiting times at individual queues on a token ring. Although exact algorithms are available, they may require significant computation time. In contrast, the approximation developed here is easily calculated on a pocket calculator, and is more accurate than earlier approximations.