Twisted pair ethernet hub for a star local area network

• US 5,351,241 A
• Filed: 12/24/1992
• Issued: 09/27/1994
• Est. Priority Date: 12/24/1992
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Yehonatan, Mivtza
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): VU, HUY DUY
• Application Number:
  US07/996,699
• Time in Patent Office: 642 Days
• Field of Search: 370/85.2, 370/94.3, 370/85.6, 370/85.7, 370/95.1, 370/85.3, 370/85.1, 370/60, 370/94.1, 340/825.02, 340/825.03, 340/825.06, 340/825.5, 340/825.51
• US Class Current: 370/446
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

A hub in a star local area network (LAN). A single station, called the preferred station, is dynamically selected to perform a transmission. When two or more stations attempt to transmit simultaneously, one currently preferred station goes through, while all others sense collisions. The currently preferred station is dynamically selected by performing a precedence algorithm which is a fairness and deterministic algorithm. If the station receiving from the preferred station also attempts to transmit, then it senses a collision and the hub lets it recover and enable itself for receiving before transmitting the frame. This is done by storing the preferred station frame in an internal small first-in first-out (FIFO) buffer. The hub resends the frame from the FIFO immediately after Inter Frame Spacing (IFS) while the receive station attempts to transmit later. If after a number of attempts the hub does not succeed in transmitting the frame successfully, then the hub generates a collision frame.

Claims

1. In a star local area network in which a plurality of stations are connected to a common hub, each one of said stations having a collision detect signal line connected to said hub, the improvement in said hub comprising:

selection means for selecting a preferred station and a preferred station frame from among ones of said plurality of stations that attempt to transmit a frame simultaneously.

said selecting means including means for performing a precedence algorithm, the ones of said plurality of stations that attempt to transmit a frame that are not selected being designated as non-preferred stations;

said preferred station frame including a destination address;

said destination address identifying a destination station;

switching means connected to said selection means for allowing said preferred station frame transmitted from said preferred station to pass through said common hub to said plurality of stations;

means for decoding said destination address of said preferred station frame;

collision detection means connected to each collision detect line and to said switching means for detecting a collision detect signal on collision detect lines from said non-preferred stations that attempt to transmit a frame;

said switching means including buffer means for storing said preferred station frame from said preferred station, upon a condition that said collision detection means detects a collision detect signal from said destination station;

boundary detection means for detecting a logical boundary between transmitted frames;

retransmission means connected to said boundary detection means and to said buffer means for retransmitting said preferred station frame from said buffer to said destination station immediately after detection of said logical boundary between transmitted frames; and

,

collision frame generating means connected to said buffer means for generating a collision frame upon a condition that said preferred station frame is not successfully retransmitted from said buffer after a predetermined number of attempts.

2. The combination in accordance with claim 1 wherein said buffer means for storing said preferred station frame from said preferred station is comprised of a first-in first-out buffer of a minimum depth equal to the number of preferred station frames that are receivable from said plurality of stations attached to said hub.

3. The combination in accordance with claim 1 wherein said buffer means for storing said preferred station frame from said preferred station is comprised of a first-in first-out buffer of a minimum depth sufficient to accommodate said predetermined number of frame retransmission attempts of said hub.

4. In a star local area network in which a plurality of stations are connected to a common hub, each of said stations including means for generating a collision detect signal, the improvement in said hub comprising:

selection logic for selecting a preferred station and a preferred station frame from among ones of said plurality of stations that attempt to transmit a frame simultaneously,

said selection logic including a precedence algorithm logic, the ones of said plurality of stations that attempt to transmit a frame that are not selected being designated as non-preferred stations;

said preferred station frame including a destination address;

a switching control connected to said selection logic for allowing said preferred station frame transmitted from said preferred station to pass through said common hub to said plurality of stations;

a destination address decoder for decoding said destination address of said selected frame to thereby identify a destination station of said preferred station;

a collision detector connected to said switching logic for detecting a collision detect signal from said non-preferred stations that attempt to transmit a frame;

said switching logic including a buffer for storing said preferred station frame from said preferred station, upon a condition that said collision detector detects a collision detect signal from said destination station;

boundary detection means for detecting a logical boundary between transmitted frames;

a retransmit logic connected to said boundary detection logic and to said buffer for retransmitting said preferred station frame from said buffer to said destination station immediately after detection of said logical boundary between transmitted frames; and

,

a collision frame generator connected to said buffer for generating a collision frame upon a condition that said preferred station frame is not successfully retransmitted from said buffer after a predetermined number of attempts.

5. The combination in accordance with claim 4 wherein said buffer is comprised of a first-in first-out buffer of a minimum depth equal to the number of preferred station frames that are receivable from said plurality number of stations attached to said hub.

6. The combination in accordance with claim 4 wherein said buffer means for storing said preferred station frame from said preferred station is comprised of a first-in first-out buffer of a minimum depth sufficient to accommodate said predetermined number of frame retransmission attempts of said hub.

7. A method of transmitting message frames within a star local area network in which a plurality of stations are connected to a common hub, comprising the steps of:

A. selecting a preferred station from among ones of said plurality of stations that attempt to transmit a frame simultaneously, said selecting being done by performing a precedence algorithm at said common hub, the ones of said plurality of stations that attempt to transmit a frame that are not selected being designated as non-preferred stations;

B. allowing a preferred station frame transmitted from said preferred station to pass through said common hub to said plurality of stations;

C. sensing collisions in all of said non-preferred stations that attempt to transmit a frame;

D. stopping transmission at all of said non-preferred stations that sense a collision;

E. storing said preferred frame from said preferred station in a buffer in said hub, upon a condition that a destination station receiving from said preferred station transmits a destination station frame;

F. retransmitting said preferred station frame from said buffer to said destination station immediately after a logical boundary between transmitted frames, upon a condition that a collision occurs between said preferred station and said destination station; and

,

G. generating a collision frame at said common hub upon a condition that said preferred station frame is not successfully retransmitted from said buffer after a predetermined number of attempts.