Communications: electrical – Continuously variable indicating – With meter reading
Patent
1993-01-29
1995-07-25
Yusko, Donald J.
Communications: electrical
Continuously variable indicating
With meter reading
34082552, 370 601, 370 8513, 370 943, H04Q 900, H04Q 1104, H04L 1256, H04J 324
Patent
active
054366178
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to multiport repeaters for digital data networks operating on "CSMA" or more especially "CSMA/CD" (carrier sensing multiple access with or without collision detection) protocols, such as the widely-used Ethernet protocol for local area networks. In such networks, individual stations are linked (normally via a "transceiver" or "media access unit" (MAU)) to network hardware that includes at least one "multiport repeater" (MPR) and may also include one or more than one "router" and/or one or more than one "bridge".
The links may be formed by electrical connections through wires or coaxial cables, by optical links through fibres or free space, or in any other appropriate way.
2. Description of Related Art
Data for transmission through such a network is assembled at the source location into digital packets of pre-arranged format. The format includes (among other things) a destination address segment that identifies the station intended to receive the packet and a source address segment identifying the station from which it originated, both of which are normally located near the beginning of the frame. Normally each station is allocated a unique sequence of digits (its "address") which is used to identify it whether in the destination address segment or the source address segment.
In the CSMA/CD protocol, any station that has data ready to transmit will attempt to do so provided it is not currently receiving data from the network, and if a second station begins to transmit in the short interval after the first has begun to transmit but before the second has become aware of it, a "collision" signal is generated and both stations stop transmitting and wait, before trying again, for a length of time that is either randomised or pre-allocated so as to be different for each station, so that repeated collisions between signals from the same two sources are avoided or minimised.
It is in the interest of both the speed and the capacity of the network to minimise the occurrence of data collisions, and in small basic networks data frames are distributed to all stations as rapidly as possible by at least one MPR which (or each of which) regenerates incoming signals and distributes them indiscriminately to all the stations and/or other MPR's that are directly connected to it with a time delay that is only a fraction of the length of a data-frame.
In larger networks, this approach gradually becomes unsatisfactory, as the number of stations seeking access increases and the aggregate time delay through a chain of MPR's also increases, and even in relatively small networks there may be unacceptable security implications in transmitting all the frames to every station. Some networks are therefore divided into sections linked not by MPR's but by "bridges" or "routers". The difference between a bridge and a router is irrelevant to understanding of this invention; each of these stores an incoming frame while it reads at least the destination address and compares it with stored data to determine which part(s) of the network need to receive it. Once this is done, the frame is retransmitted only to that part (or parts) of the network. Bridges and routers are complex and expensive, and they necessarily introduce a delay which will often be substantially longer than a frame length. On the other hand, they increase the capacity of the system by allowing separate control of collisions in the pre-arranged sections of the network and by reducing the overall amount of traffic on some elements of the network.
SUMMARY OF THE INVENTION
The present invention provides an MPR that increases the capacity of a CSMA/CD network for comparatively little extra cost and that operates with no more delay than an ordinary MPR (that is, the multiport repeater executes its repeater function within the time delay established for the repeater by the selected protocol corresponding to the selected local area network (LAN) technology, such as an Ethernet CSMA/CD) and without requirin
REFERENCES:
patent: 4191941 (1980-03-01), Springer et al.
patent: 4633245 (1986-12-01), Blount et al.
patent: 4646296 (1987-02-01), Bartholet et al.
patent: 4991171 (1991-02-01), Teraslinna et al.
patent: 4999833 (1991-03-01), Lee
patent: 5095480 (1992-03-01), Fenner
patent: 5107489 (1992-04-01), Brown et al.
patent: 5119370 (1992-06-01), Terry
patent: 5127067 (1992-06-01), Delcoco et al.
patent: 5136580 (1992-08-01), Videlock et al.
patent: 5140585 (1992-08-01), Tomikawa
patent: 5144293 (1992-09-01), Rouse
patent: 5144622 (1992-09-01), Takiyasu et al.
patent: 5204858 (1993-04-01), Kinashi et al.
patent: 5309437 (1994-05-01), Perlman et al.
Adams Martin C.
Soni Dipak M.
3Com Corporation
Rinehart Mark H.
Yusko Donald J.
LandOfFree
Repeaters for digital data networks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Repeaters for digital data networks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Repeaters for digital data networks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-742618