Communications: electrical – Continuously variable indicating – With meter reading
Patent
1986-07-11
1990-05-01
Yusko, Donald J.
Communications: electrical
Continuously variable indicating
With meter reading
34082505, 370 851, 370 941, H04Q 900
Patent
active
049222449
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a queueing protocol for controlling access of communication devices to a distributed local network, a centralised switch, or a system which comprises a number of network interconnected switches.
In recent years there has been interest in providing communications networks which are capable of handling a wide mix of traffic such as data, voice, video and facsimile. One proposal suggests the use of a number of stations connected between a pair of unidirectional links, this proposal being published in the Bell System Technical Journal, Sept. 1982 under the title: Description of Fastnet --A Unidirectional Local-Area Communications Network.
Another system is described in a paper entitled "A Packet/Circuit Switch" by Z.L. Budrikis and A.N. Netravali, published in the AT & T Bell Laboratories Technical Journal Vol. 63, No. 8, Oct. 1984. This paper proposes a local network which has access units (AUs) connected between unidirectional buses. An access unit (AU) simply refers to any apparatus which permits communications to and from the unidirectional buses. The AUs are arranged to handle data communications in single length packets as described in Chapter 3.2 of that paper. The same format is proposed for circuit switched packets which refers to synchronous communications such as telephone communications which desirably do not have variable delays in the transmission paths.
Generally speaking, the principal object of the invention is to provide a novel queueing protocol which can be used in a system similar to that proposed by Budrikis and Netravali. As will be apparent from the following description the novel queueing system has very substantial advantages.
According to the present invention there is provided a method of transmitting data on a communications network having first and second unidirectional buses which are oppositely directed and a plurality of access units coupled between the buses, said method including the step of arranging the data to be transmitted from the access units in data packets, and establishing a distributed queue in the network to control the order of data packet transmissions from said access units.
Preferably, the method includes the steps of determining, according to destination upon which one of the buses a data packet is to be transmitted from one access unit, transmitting a request flag on the second bus when said one access unit has a data packet for transmission on said first bus, incrementing a request flag counter at said one access unit each time a request flag is detected by said one access unit on said second bus from access units upstream of said one access unit on said second bus decrementing said counter each time an empty data packet is detected by said one access unit on said first bus and transmitting said data packet from said one access unit on said first bus in accordance with the count of said counter.
Preferably further, separate distributed queues are established for data packet transmissions in the respective buses.
Preferably further, each data packet includes a preselected priority flag indicative of N preselected priority levels for data packet transmission and wherein the method includes the step of establishing N separate queues for the respective priority levels, where N is any positive integer.
The invention also provides a communications network for transmission of information in data packets comprising: first and second unidirectional buses which are oppositely directed, a plurality of access units coupled between the buses, each of said access units having at least one counter means therein, the arrangement being such that the contents of the respective counters means are used as a distributed queue to control transmission of data packets on the buses.
Preferably each access unit includes means for determining upon which one of the buses the data packet is to be transmitted according to destination, and wherein the access units includ request flag generating means for generating a request flag on the second bus when said acce
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Hullett John L.
Newman Robert M.
Holloway III Edwin C.
The University of Western Australia
Yusko Donald J.
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