WO1997043843A1 - Procede et appareil permettant de reguler le flux de donnees dans un reseau ethernet - Google Patents

Procede et appareil permettant de reguler le flux de donnees dans un reseau ethernet Download PDF

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Publication number
WO1997043843A1
WO1997043843A1 PCT/US1997/008111 US9708111W WO9743843A1 WO 1997043843 A1 WO1997043843 A1 WO 1997043843A1 US 9708111 W US9708111 W US 9708111W WO 9743843 A1 WO9743843 A1 WO 9743843A1
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WO
WIPO (PCT)
Prior art keywords
nodes
data
hub
node
current node
Prior art date
Application number
PCT/US1997/008111
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English (en)
Inventor
Kenneth N. Fujimoto
Original Assignee
Medialink Technologies Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Medialink Technologies Corporation filed Critical Medialink Technologies Corporation
Publication of WO1997043843A1 publication Critical patent/WO1997043843A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/44—Star or tree networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/403—Bus networks with centralised control, e.g. polling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/407—Bus networks with decentralised control
    • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]

Definitions

  • This invention relates to Ethernet networks and, more particularly to method and apparatus for controlling the flow of data in an Ethernet network having a star configuration, i.e., a plurality of nodes connected to a centralized hub.
  • Ethernet is one of the most popular local area networking standards. Although traditionally developed to implement a bus topology, in which all nodes are connected to one another by a single coaxial cable, Ethernet networks have shifted to a star configuration, wherein each node of the network is connected to a centralized hub by a twisted-pair cable. When the hub receives the transmission from one of the nodes, the hub repeats the transmission to each of the other nodes.
  • Ethernet relies upon a form of network access protocol known as Carrier Sense Multiple Access with Collision Detection ("CSMA/CD”) to regulate communication via the network.
  • CSMA/CD Carrier Sense Multiple Access with Collision Detection
  • each node contends for access to the network.
  • the CSMA/CD network protocol requires that a node wait until the network has been quiet for a predetermined period of time (9.6 microseconds) before it begins to transmit a data packet via the network.
  • the hub then retransmits the packet to all of the other nodes. If more than one node attempts to transmit a packet at the same time, a collision occurs and the CSMA/CD protocol requires the nodes to wait a random back-off time interval before transmitting again.
  • a transmitting node successfully sends a data packet to the hub without a collision, that node will have a better chance statistically of being allowed to send another data packet, because the transmitting node will most likely calculate a random back-off time that is less than the random back-off time calculated by any other node of the network. If the transmitting node successfully transmits another packet or two, it becomes progressively more difficult for any of the other nodes to transmit. Consequently, the transmitting node may become the most favored node to transmit another packet. Eventually, the node may "capture" the network for the transmission of about sixteen data packets, during which time the remaining nodes are denied access to the network.
  • Ethernet should be able to carry all types of multimedia data, such as voice (64 Kbps), CD quality audio (1.4 Mbps) and MPEG video (1-2 Mbps).
  • voice 64 Kbps
  • CD quality audio 1.4 Mbps
  • MPEG video 1-2 Mbps
  • the present invention provides a method and apparatus that meet these criteria and solves other problems in the prior art.
  • a method and apparatus are provided for controlling the flow of data in an Ethernet network having a plurality of nodes connected to a centralized hub. Only one node is selected to transmit data via the Ethernet network at a time. During a first predetermined time interval, a traffic signal is transmitted by the hub to all nodes except the selected node so as to prevent those nodes from transmitting data to the hub. If the selected node transmits data to the hub during the first predetermined time interval, the hub retransmits the data to each node except the selected node.
  • the hub transmits a synchronization signal to each node including the selected node so as to synchronize the signals being received by each of the nodes.
  • a new node is then selected to transmit data and the process is repeated upon the expiration of a second predetermined time interval.
  • the hub when the hub receives the data from the selected node and retransmits the data to each of the nodes, the hub ceases transmitting the traffic signal to each of the other nodes and transmits the data to each of the other nodes immediately following the traffic signal such that the data is "spliced" onto the traffic signal.
  • the node selected to transmit data may be selected as a function of network bandwidth, time, or the number of ports included in the hub.
  • FIGURE 1 is a pictorial diagram of a plurality of computers, i.e., nodes, connected in a star Ethernet network to a centralized repeater hub implementing the present invention
  • FIGURE 2 is a block diagram of the hub shown in FIGURE 1 ;
  • FIGURES 3A and 3B are a flow diagram of the method of controlling the flow of data between the plurality of nodes connected to the hub shown in FIGURE 1; and
  • FIGURES 4A and 4B are waveform diagrams of the data transmissions into and out of the hub shown in FIGURE 1.
  • FIGURE 1 illustrates an Ethernet network 10 in a star configuration that connects a plurality of personal computers 12 to a hub 20.
  • Each of the computers connected to the star network 10 is hereinafter referred to as a node 0 through 3.
  • any number of computers i.e., nodes
  • any type of computer including but not limited to portable computers, personal digital assistants, etc. that is equipped with the necessary interface hardware may be connected to the star network 10.
  • other electronic devices may also be connected to the star network 10, if equipped with the necessary interface hardware. Suitable electronic devices may include video cameras, speakers, television sets, telephones, lamps, etc.
  • the present invention provides a method and apparatus that control the flow of data via the Ethernet network 10. Specifically, the present invention determines which node will be granted access to the network so that it may transmit a data packet to the hub 20, and when the hub will repeat that data packet to the remaining nodes within the confines of the Ethernet network standard.
  • the hub 20 interconnecting the nodes 0, 1, 2 and 3 is a repeater hub. Consequently, when the hub 20 receives a data packet from any one of the nodes 0, 1, 2 or 3, the hub retransmits or "repeats" the data packet to each of the other nodes. For example, if node 1 transmits a data packet to the hub 20, the hub will repeat the data packet to each of the remaining nodes 0, 2 and 3.
  • FIGURE 2 illustrates in greater detail the hub 20 shown in FIGURE 1.
  • the hub 20 includes a microprocessor 14 and a data loopback and preamble generation state machine 16 that control the flow of data packets via the network 10 as will be described in more detail below.
  • the microprocessor determines which one of the nodes will be granted access to the network; determines the time at which a received data packet will be sent to the other nodes; and selects which nodes will be sent the data packet.
  • the state machine 16 is a collection of flip flops, NAND, AND and OR gates that generate a series of signals based on instruction received from the microprocessor, that control the flow of data packets from the node granted access, to the other nodes.
  • the hub 20 receives data packets from the nodes 12 via a plurality of ports 18. More specifically, each node O, 1, 2 and 3 transmits and receives data through ports 0, 1, 2 and 3, respectively.
  • the hub also includes a plurality of decoders 22 designated as decoders 0, 1, 2 and 3 and corresponding to ports 0, 1, 2 and 3, respectively.
  • the decoders decode the data packet transmitted by the corresponding nodes via the corresponding ports into a receive data signal, a receive clock signal, and a receive carrier signal. These signals are then provided to a selector 30 that selects the signals to be processed, i.e., selects which node will be granted access to the network 10, based on a control signal received from the microprocessor 14. The selected receive data, receive clock, and carrier signals are then provided by the selector 30 to the state machine 16.
  • the hub 20 also includes a demultiplexer 24 and a plurality of encoders 26, designated as encoders 0, 1, 2 or 3, corresponding to ports 0, 1, 2 or 3 and thus, nodes 0, 1, 2 or 3, respectively.
  • the state machine 16 Upon receipt of a transmit control signal from the microprocessor 14, the state machine 16 sends the demultiplexer a transmit enable signal and the encoders a transmit data signal and a transmit clock signal.
  • the demultiplexer 24 supplies the transmit enable signal to the encoders that are to encode the transmit data signal using the transmit clock signal.
  • the hub transmits received data to all of the nodes except the one sending the data to the hub.
  • all of the encoders, except for one are enabled by the transmit enable signal.
  • the demultiplexer 24 in essence decides which encoder is not to be enabled based on the nature of the port select signal and the transmit enable signal. The encoders then encode the data signal and send the encoded data signal to the corresponding nodes via the corresponding ports.
  • the flow of data through the Ethernet network 10 via the hub 20 is controlled in accordance with the logic illustrated in FIGURES 3A and 3B.
  • the hub 20 grants each node access to the network 10 in a round-robin fashion, i.e., the hub 20 only allows one node to transmit a data packet via the network at a time. Consequently, no node becomes favored and the "capture effect" is eliminated. Further, because only one node is allowed to transmit data at a time, packet collision is avoided and the distribution of backlogged packets is evenly spread out over the network. The overall result is predictable packet latencies over the network.
  • a current node variable used to identify the node being granted access by the hub is initialized to zero at a block 102 of FIGURE 2A.
  • a number of ports counter that is used to keep track of the number of ports 18 in the hub 20 is initialized.
  • the number of ports counter is set equal to 4 because there are four ports 0, 1, 2 and 3, one for each node 0, 1, 2 and 3. As will be described more fully below, the number of ports counter is used to determine the next node that will be granted access to the network 10.
  • the hub 20 waits for a predetermined spacing interval, for example, 4.5 microseconds (identified as interval "B" in FIGURES 4A and 4B) to expire. Then in a block 108, a timer is set to zero and started. As the timer runs, the logic proceeds to a decision block 110 where a test is made to determine if the hub 20 is receiving a data packet from the current node via the current port. If the result of decision block 110 is negative, the logic proceeds to a block 116 where the hub 20 begins transmitting a traffic signal 32 to all of the nodes connected to the hub, except the current node.
  • a predetermined spacing interval for example, 4.5 microseconds (identified as interval "B" in FIGURES 4A and 4B)
  • the traffic signal is preferably comprised of alternating Is and 0s and created by changing the state of a bit between zero and one each time a pass is made through block 116.
  • a traffic signal 32 prevents the other nodes from transmitting a data packet to the hub.
  • the lack of a traffic signal being sent to the current node creates a gap (identified as interval "A" in FIGURE 4A) during which the current node can transmit a data packet to the hub.
  • a decision block 118 the logic determines if a 9.6 microsecond transmission interval has passed. This is determined by testing the timer (started in block 108) to determine if the timer value is greater than or equal to 9.6 microseconds. If the a transmission interval has not passed, the logic returns to decision block 110. If the result of decision block 110 is positive, meaning that the hub 20 is receiving a data packet from the current node, the logic proceeds to block 112. At block 112 the hub 20 transmits the received data packet to all of the nodes except the current node. Next, at a decision block 114, the logic determines if the hub has finished receiving the data packet from the current node via the current port. If the result is negative, the logic returns to block 112.
  • Blocks 112 and 114 are repeated until the hub has finished receiving the data packet from the current node. Then the logic proceeds to decision block 118 where it determines if the 9.6 microsecond transmission interval has passed. It will be appreciated that the transmission interval may have long been exceeded depending on the size of the data - -
  • each data packet contains a preamble of at least fifty-six bits of alternating Is and 0s. Since there is no maximum specification for the length of the preamble under the Ethernet standard, the extra alternating bits spliced onto the transmitted data packet are merely treated by the Ethernet network 10 as part of the preamble.
  • the present invention seamlessly interfaces with the Ethernet network, and there is no need to modify or change the existing Ethernet network adapters, network cards or driver software in any of the connected nodes.
  • Blocks 110-118 are repeated until the 9.6 microsecond transmission interval has expired, or longer if the retransmission of data received from the current node exceeds the transmission interval.
  • the logic proceeds to a decision block 120 where a test is made to determine if the hub 20 had received a data packet from the current node via the current port during the period of time the logic was cycling through blocks 106-118. If the result is negative, it will be appreciated that a traffic signal was transmitted to all of the remaining nodes, except for the current node for exactly 9.6 microseconds. Further, no data was received by the hub from the current node for a total of 14.1 microseconds (4.5 microseconds plus 9.6 microseconds).
  • the hub Before the hub grants access to another node and repeats the process described above beginning with the initiation of the 4.5 microsecond spacing interval, the hub must synchronize all of the nodes. This is done to ensure that all of the nodes begin the 4.5 microsecond spacing interval at the same point in time.
  • the logic proceeds to a block 122 where the timer is reset to 0.
  • the hub begins transmitting a synchronization signal 34 to all of the nodes, including the current node.
  • the synchronization signal is preferably created by changing the state of a bit between zero and one each time a pass is made through this part of the logic. With respect to the current node, this first bit marks the end of the 9.6 microsecond interval during which the hub 20 gave the current node the opportunity to transmit a data packet.
  • a decision block 126 the logic determines if the hub 20 is now receiving a data packet from the current node via the current port. If the result is positive, the logic proceeds to block 128 where the alternate bit is sent to all nodes, e.g., if the bit sent at block 124 was a one, the bit sent at black 128 is a zero and vice versa. Blocks 126 and 128 are repeated as long as the hub continues to receive a data packet from the current node. Hence, rather than recognizing and retransmitting the received data packet to all the other nodes, the hub ignores the received data packet and continues sending the synchronization signal 34 comprising alternating Is and 0s to all of the nodes, including the current node.
  • the logic determines if a predetermined (preferably 3.2 microsecond) synchronization interval has passed, i.e., the timer is tested to determine if its value is greater than or equal to 3.2 microseconds. If the result is negative, the logic returns to block 124 where the hub 20 sends the opposite (alternate) bit to all of the ports. Blocks 124-130 are repeated until the 3.2 microsecond synchronization interval has expired. As shown in FIGURES 4A and 4B, sending a synchronization signal 34 to each of the ports at the end of the transmission interval results in all of the nodes being synchronized before the initiation of the next 4.5 microsecond spacing interval.
  • the traffic signal essentially is extended another 3.2 microseconds to end at the same time as the 3.2 microsecond synchronization signal 34 transmitted to the current node.
  • the hub receives a data packet from the current node during the 3.2 microsecond interval, the hub ignores the incoming data and continues to send the synchronization signal 34 (comprised of alternating bits) to all of the nodes, including the current node until the entire data packet has been received by the hub. Necessarily, the synchronization signal transmitted to all of the nodes will end at the same time, even though the 3.2 microsecond synchronization signal may have since been exceeded.
  • the logic " ⁇ "then returns to block 106 where the hub waits for a 4.5 microsecond spacing interval to expire. Blocks 106-132 are continuously repeated as the hub grants network access to each node, one node at a time.
  • FIGURE 4B is an exemplary diagram that first depicts the traffic and data signals received and transmitted by the hub 20 when node 2 is granted access to the network 10 and transmits a data packet 38 to the hub via input port 2 following the expiration of the 4.5 microsecond spacing interval.
  • the data packet 38 is repeated to the remaining nodes 0, 1, and 3 via ports 0, 1, and 3, respectively, spliced to the portion 36 of the traffic signals that occurred prior to when the hub first received the data packet from node 2.
  • the hub grants access to the network 10 to node 3 connected to the hub via port 3.
  • the hub then waits for another 4.5 microsecond spacing interval to expire and sends a traffic signal 32 comprising alternating Is and 0s to each of the other nodes, namely, nodes 0, 1, and 2 via their corresponding ports.
  • node 3 Since node 3 does not transmit a data packet during the next 9.6 microsecond transmission interval, the transmission of signals to each of the nodes is resynchronized by transmitting a synchronization signal 34 comprised of alternating Is and 0s that is sent to all of the nodes by the hub for the next 3.2 microseconds. Once synchronized, the hub grants access to a new node, another 4.5 microsecond spacing interval begins, and so on.
  • a timing scheme could be implemented that would assign a timer to each node of the hub.
  • the hub would grant access in round-robin fashion to all of the nodes whose timers have timed out. If no node timed out, the hub would grant access to each node in turn.
  • the timers could also be adapted such that if the nodes sent data on every grant the time out would decrease.
  • the hub could also be configured so as to provided guaranteed bandwidth to each node.
  • 9.6 microsecond transmission interval, 3.2 microsecond synchronization interval and the 4.5 microsecond spacing interval have been calibrated to provide a smooth interface with the Ethernet standard, those of ordinary skill in the art will recognize that under some circumstances it may be desirable to vary or modify the length of these time intervals. Accordingly, it is not intended that the scope of the invention be limited by the disclosure of the actual embodiment described above. Instead the invention should be determined entirely by reference to the claims that follow.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)

Abstract

Procédé permettant de réguler le flux de données dans un réseau Ethernet (10) doté d'une pluralité de noeuds (12) connectés à un pivot (20) qui accorde l'accès à un noeud à la fois et attend pendant un intervalle de transmission de 9,9 microsecondes pour que le noeud (12) transmette un paquet de données au pivot (20). Lors de l'attente, le pivot (20) envoie des signaux de trafic à chacun des autres noeuds (12) afin de les empêcher de transmettre un paquet de données au pivot (20) pendant l'intervalle de transmission de 9,6 microsecondes. Si le pivot (20) reçoit un paquet de données du noeud (12) à qui l'accès a été accordé pendant l'intervalle de transmission de 9,6 microsecondes, il (20) cesse d'émettre des signaux de trafic (32) et retransmet immédiatement le paquet de données aux noeuds restants. Le paquet est rattaché à la fin (36) du signal de trafic qui a été envoyé aux autres noeuds lorsque le paquet de données a démarré. Le pivot (20) accorde ensuite l'accès à un nouveau noeud (12) et attend que s'écoule un intervalle d'espacement de 4,5 microsecondes avant de transmettre des signaux de trafic aux noeuds restants. Si le pivot (20) ne reçoit pas de paquet de données du noeud pendant l'intervalle de 9,6 microsecondes, il (20) émet un signal de synchronisation (34) à chaque noeud avant d'accorder l'accès à un nouveau noeud (12) et de répéter le processus une fois écoulé l'intervalle d'espacement de 4,5 microsecondes.
PCT/US1997/008111 1996-05-15 1997-05-14 Procede et appareil permettant de reguler le flux de donnees dans un reseau ethernet WO1997043843A1 (fr)

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US64855796A 1996-05-15 1996-05-15
US08/648,557 1996-05-15

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19835376A1 (de) * 1998-08-05 2000-02-10 Abb Research Ltd Verfahren zum Betrieb mehrerer Geräte an einem CSMA-Netzwerk
WO2002054680A1 (fr) * 2000-12-28 2002-07-11 Lanxpress Plc Dispositif de commande pour un reseau de communication
WO2003077479A1 (fr) * 2002-03-14 2003-09-18 Wolfram Kress Procede d'echange mutidirectionnel d'ensembles de donnees
CN114244773A (zh) * 2020-09-09 2022-03-25 英业达科技有限公司 封包处理系统及其封包处理方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0123507A1 (fr) * 1983-04-21 1984-10-31 International Computers Limited Système et appareil de communication de données
US5355375A (en) * 1993-03-18 1994-10-11 Network Systems Corporation Hub controller for providing deterministic access to CSMA local area network
US5469439A (en) * 1994-05-04 1995-11-21 Hewlett Packard Company Two priority fair distributed round robin protocol for a network having cascaded hubs

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0123507A1 (fr) * 1983-04-21 1984-10-31 International Computers Limited Système et appareil de communication de données
US5355375A (en) * 1993-03-18 1994-10-11 Network Systems Corporation Hub controller for providing deterministic access to CSMA local area network
US5469439A (en) * 1994-05-04 1995-11-21 Hewlett Packard Company Two priority fair distributed round robin protocol for a network having cascaded hubs

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19835376A1 (de) * 1998-08-05 2000-02-10 Abb Research Ltd Verfahren zum Betrieb mehrerer Geräte an einem CSMA-Netzwerk
WO2002054680A1 (fr) * 2000-12-28 2002-07-11 Lanxpress Plc Dispositif de commande pour un reseau de communication
WO2003077479A1 (fr) * 2002-03-14 2003-09-18 Wolfram Kress Procede d'echange mutidirectionnel d'ensembles de donnees
CN114244773A (zh) * 2020-09-09 2022-03-25 英业达科技有限公司 封包处理系统及其封包处理方法

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