A combination of two new access methods for ring and unidirectional bus networks supports high data rate integrated traffic The first access method provides access for asynchronous traffic When a node senses the channel idle, it can begin to transmit When it senses an incoming signal, it must stop transmitting in order to avoid a collision But unlike other access protocols which abort the transmission when a collision occurs or is imminent, the process truncates the message in a fashion such that it can be resumed later when the channel again is idle The system is called Carrier Sensed Multiple Access-Ring Network (CSMA/RN) The second access method provides support for synchronous traffic This method implements one or more circulating reservation packets which permit a node to have reserved space when the special packet returns The media access system is called Circulating Reservation Packet (CRP) system Both access protocols operate simultaneously on the network with minimal interference The CRP system is preferably used with the CSMA/RN protocol but is applicable to other fixed length, non-corrupting, circulating network structures to enable the nodes in a network to reserve space for synchronous traffic and guaranteed access

Control of access through local carrier sensing for high data rate networks and control of access of synchronous messages through circulating reservation packets

This paper presents a significant extension of the CSMA network access protocol. The protocol is based on the facts that, at high data rates, networks can contain multiple messages simultaneously over their span, and that in a ring, nodes needs only to detect the presence of a message arriving from the immediate up stream neighbor. When an incoming signal is detected, the node truncates the message it is presently sending instead of aborting it. The system has been named Carrier Sensed Multiple Access Ring Network, CSMA/RN.Analytical studies using three performance factors, wait or access time, service time and response or end-to-end travel time are presented. The service time is basically a function of the network rate; it changes by a factor of 4 between no load and full load. Wait time, which is zero for no load, remains small for load factors up to 70% of full load. Response time, which adds travel time while on the network to wait and service time, is mainly a function of network length, especially for longer distance networks.Simulation results are shown for CSMA/RN where messages are removed at the destination. Destination removal on an average increases network load capacity by a factor of 2, i.e., a 1 Gbps network can handle a 2 Gbps load. A wide range of local and metropolitan area network parameters including variations in message size, network length and node count are studied. In all cases performance is excellent, and message fracture usually remains less than a factor of 4. Throughput, even at overload conditions, remains high for the protocol. The nominal network rate is 1 Gbps; however, performance remains good for data rates as low as 200 Mbps. Finally, a scaling factor based upon the ratio of message to network length demonstrates that the results of this paper, and hence, the CSMA/RN protocol, are applicable to wide area networks.

A carrier sensed multiple access protocol high data rate ring networks

The Collision Avoidance Tree is a local area network based on a hardware device called the collision avoidance switch. The collision avoidance switch arbitrates random access to a shared communication channel and avoids the penalty of collisions among packets. This network combines the benefits of random access (low delay when traffic is light; simple, distributed, and robust protocols) with concurrency of transmission, excellent network utilization and suitability for the domain of high-speed optical networking. The Collision Avoidance Tree is classified in two groups: the Collision Avoidance Single Broadcast (CASB) Tree and the Collision Avoidance Multiple Broadcast (CAMB) Tree. The CASB Tree allows only a single transmission on the network at a given time, while the CAMB Tree allows concurrent transmissions on the network. This paper describes network architectures (station and switch protocols) as well as designs and implementations. Performance results derived from analyses, simulations, and measurements of experimental networks are also presented.

Collision avoidance tree networks

The design is presented of a broadcast star network that uses a collision-avoidance switch. This network combines the benefits of random access (low delay when traffic is light; simple, distributed, and therefore robust protocols) with excellent network utilization. Performance analyses of a slotted broadcast star network are then presented to obtain distributions of the transmission delay: an exact analysis for a network with an infinite number of stations, and an approximate analysis for a network with a finite number of stations. >

Performance study of a tree LAN with collision avoidance

Presents a design of a collision avoidance switch for the collision avoidance multiple broadcast (CAMB) tree using transistor-transistor logic (TTL) devices. A simulation study exploring the performance of the broadcast star network in both synchronous and asynchronous operations is also presented. Simulation results show that the slotted broadcast star achieves better performance than the unslotted broadcast star, especially when the traffic load is heavy. >

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LAN with collision avoidance: switch implementation and simulation study

Packet collisions and their resolution create a performance bottleneck in random access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the im...

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Papers

Tree LANs with collision avoidance: protocol, switch architecture, and simulated performance