Pulse or digital communications – Repeaters
Reexamination Certificate
1997-10-08
2001-06-05
Bocure, Tesfaldet (Department: 2631)
Pulse or digital communications
Repeaters
Reexamination Certificate
active
06243411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to computer networks and, more particularly, to a repeater unit for use in a Local Area Network operating according to the IEEE 802.3 Standard (an Ethernet network) and which may be expandable to have an unlimited number of ports, yet operates as a single repeater as defined by IEEE 802.3.
2. Discussion of Related Art
Local Area Networks (LAN) are computer networks which allow a number of data terminal equipment (DTE) to share resources and communicate with each other, thus greatly expanding the usefulness of each DTE. Many types of LANs are known. One common LAN type is a Carrier Sense, Multiple Access Collision Detection (CSMA/CD) network, defined by the IEEE 802.3 Standard and commonly referred to as an Ethernet network. (Ethernet is a registered trademark of the XEROX corporation.) The contents of the IEEE 802.3 Standard are incorporated herein by reference.
Briefly, an Ethernet network operates in the following manner. As seen in
FIG. 1
, an Ethernet network
100
may include a number of DTEs
102
each connected to a port
103
of a central hub or repeater
104
. The DTEs and hub are arranged in a star topology. When a DTE
102
wishes to transmit data to other DTEs on the network, the DTE waits for a quiet period on the network, and then sends the intended message to the repeater
104
in bit-serial form. The repeater
104
then repeats the message to all of the DTEs connected to it. If, after initiating a transmission, another DTE also attempts to transmit a message at the same time, a “collision” is detected. If a collision is detected, then both transmitting stations send a few additional bytes to ensure propagation of the collision throughout the network. The transmitted messages are discarded. The DTEs that attempted to transmit remain silent for a random time (“back-off”) before attempting to transmit again. Because each DTE
102
selects its back-off time independently of the other DTEs, a second collision may be avoided.
As seen in
FIG. 2
, a number of repeaters
104
may be connected to create a series
200
of connected hubs or repeaters. To meet IEEE 802.3 timing requirements, the maximum number of repeaters
104
in any series (from any DTE to any other DTE) is four. Moreover, the star topology allows only one DTE to be connected to each port. Limited port availability on repeaters
104
limits the number of DTEs
102
which may connect to a repeater. The limited number of repeaters in any Ethernet series limits the number of DTEs
102
which may be included in a single Ethernet network series (called a collision domain). If each repeater, for example, has eight ports, only 32 DTEs may be connected to a single collision domain. (Note that
FIG. 2
shows a collision domain having 26 DTEs.)
A typical repeater comprises a single integrated circuit chip. Because an IC chip has limited drive current, each chip has a limited number of ports. Thus, each repeater is limited to a number of ports, thus limiting the total number of DTEs which may be connected to a single collision domain. Thus, it is desirable to have repeater units which may be expanded to have additional ports.
Expandable repeaters are known. For example, an expandable repeater is described in U.S. Pat. No. 5,265,123 issued on Nov. 23, 1993 to Vijeh, et al. The contents of this document are incorporated herein by reference. Vijeh, et al. disclose an expandable repeater which connects each repeater unit to an expansion bus. For a repeater unit to transmit on the expansion bus, it must seek permission to do so. An arbiter receives request signals from repeat units seeking to transmit onto the bus, determines which repeater unit may control the expansion bus, issues an acknowledgement signal to that repeater unit, and precludes other repeater units from simultaneously controlling the bus.
U.S. Pat. No. 5,517,520, described above, discloses an expandable repeater in which a number of repeater units are connected in a star topology to an integrator unit. Each repeater unit has an input/output for providing clock, data, control, and collision information to the integrator. A repeater unit issues a request-for-access signal when it wants to transmit to the integrator unit.
It is an object of the present invention to provide an expandable repeater which does not use request or acknowledge signals.
SUMMARY OF THE INVENTION
This and other objects of the present invention are provided by a repeater comprising two or more repeater units. The repeater units are connected to an integrator device which coordinates the repeater units to function as a single repeater according to the IEEE 802.3 Standard.
In a preferred embodiment of the present invention, an expandable repeater includes N repeater units connected to an integrator device and a bus. Each of the N repeater units has an input/output connected to the bus for exchanging clock, data, and to receive network status signals. Each repeater unit also provides status signals to the integrator device. The status signals indicate to the integrator whether the repeater unit is transmitting data, ready to receive data, or detecting a collision. The integrator receives N (where N is the number of repeater units to be combined by the integrator) sets of status signals, determines the network status, supplies network status information to the bus, and exchanges clock information and data with the bus. The integrator selectively executes the data and clock repetition, and provides a global network status signal in response to the status signals received from all of the repeater units connected to the integrator. A number of integrators may be combined in a similar fashion to further expand the repeater. The combinations may be continued, resulting in an hierarchical arrangement of integrators which provides an infinitely expandable repeater.
The expandable repeater permits a number of repeater units to be combined to operate as a single repeater, thus increasing the number of DTEs which may be connected to a single Ethernet collision domain. Also, the repeater operates without repeater units requesting access to transmit and does not need to receive an acknowledgment signal before transmitting data to the network.
REFERENCES:
patent: 5265123 (1993-11-01), Vijeh et al.
patent: 5430762 (1995-07-01), Vijeh et al.
patent: 5517520 (1996-05-01), Chi
patent: 5550803 (1996-08-01), Crayford et al.
patent: 5566160 (1996-10-01), Lo
patent: 5606664 (1997-02-01), Brown et al.
patent: 5754540 (1998-05-01), Liu et al.
Bocure Tesfaldet
Proskauer Rose LLP
Winbond Electronics Corp.
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