WO2007096852A1 - Reseau de communication optique - Google Patents

Reseau de communication optique Download PDF

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Publication number
WO2007096852A1
WO2007096852A1 PCT/IE2007/000024 IE2007000024W WO2007096852A1 WO 2007096852 A1 WO2007096852 A1 WO 2007096852A1 IE 2007000024 W IE2007000024 W IE 2007000024W WO 2007096852 A1 WO2007096852 A1 WO 2007096852A1
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WO
WIPO (PCT)
Prior art keywords
network
wavelength
optical
node
packet
Prior art date
Application number
PCT/IE2007/000024
Other languages
English (en)
Inventor
David Cotter
Original Assignee
University College Cork - National University Of Ireland, Cork
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 University College Cork - National University Of Ireland, Cork filed Critical University College Cork - National University Of Ireland, Cork
Publication of WO2007096852A1 publication Critical patent/WO2007096852A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0016—Construction using wavelength multiplexing or demultiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0024—Construction using space switching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0007—Construction
    • H04Q2011/0033—Construction using time division switching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0037—Operation
    • H04Q2011/0039—Electrical control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H04Q2011/0052—Interconnection of switches
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0064—Arbitration, scheduling or medium access control aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0073—Provisions for forwarding or routing, e.g. lookup tables
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/009—Topology aspects

Definitions

  • Each of the torus nodes contains a 2x2 cross-bar space switch, as shown in Fig. 2.
  • Fig. 2a When the switch is in the cross state (Fig. 2a), the row input is connected to the row output and the column input is connected to the column output; whereas when the switch is in the bar state (Fig. 2b), the row input is connected to the column output and the column input is connected to the row output.
  • Fig. 2b When the switch is in the bar state (Fig. 2b), the row input is connected to the column output and the column input is connected to the row output.
  • the switches throughout the network operate in synchronism with a global clock. According to this global clock, time is divided into a continuous sequence of fixed, equal-length time slots.
  • the source could transmit the packet on the column output in a time slot labelled 1, in which case the clockwork routing is as follows: node (2, 0) in time slot 1; node (1, 0) in time slot 2; node (0, 0) in time slot 3; node (3, 0) in time slot 0 (at which point the packet is diverted automatically to the row); node (3, 3) in time slot 1; and finally the destination node (3, 2) in time slot 2. Notice, in this case the alternative routing is longer than the first.
  • the packet destination address is compared with the address of the current node; if there is an address match, the destination has been reached and the packet will be removed from the network, whereas if the addresses do not match the packet will be allowed to continue uninterrupted. Notice that at each node, this simple address match is the only information processing needed to ensure the packet arrives correctly at its destination. All the routing selection is performed at the source, by the initial choice of outward link and time slot.
  • an optical interconnection network having a plurality of network nodes interconnected by optical links:
  • network nodes each comprise means for receiving a global clock and for switching repeatedly with a fixed periodicity their routing states according to the global clock;
  • each network node comprises means for selecting a time slot, a wavelength, and an initial optical link for transmitting a packet in dependence upon the desired path for the packet through the network, and for outputting the packet in the selected time slot, wavelength and link.
  • the transmission wavelength generator comprises: an interface to receive data in electrical form; an interface to the optical node processor; and a switch to transfer the data signal to one of a plurality of lasers each emitting at a different wavelength.
  • each laser is an integrated laser modulator semiconductor laser.
  • the means for selecting a wavelength for a packet includes means for switching a laser between a plurality of emission wavelengths.
  • the invention provides a supercomputer comprising a plurality of computing processors and any interconnect network as defined above.
  • each network node comprises a plurality of channel nodes for each network link, and each processor is connected to a channel node.
  • each processor is connected to a buffer of a channel node.
  • Fig. 1 is a diagram showing a 4 x 4 "clockwork" type network of the prior art discussed in the INTRODUCTION above and also applying to the invention at this level;
  • Fig. 2 is a diagram of a 2x2 crossbar switch for a node of the network of Fig. 1, showing the cross (a) and bar (b) states, discussed in the INTRODUCTION above and also applying to the invention at this level;
  • Fig. 7 shows a configuration of opto-electronic components to implement an optical wavelength converter of the switch of Fig. 5.
  • Fig. 8 is a block diagram showing the functional components of a wavelength or "optical" channel node of the network node of Fig. 4;
  • Fig. 9 shows a configuration of optical and opto-electronic components to implement a transmission wavelength selector of the channel node of Fig. 8;
  • Figs. 10 and 11 show alternative implementations of the transmission wavelength selector.
  • An optical communication network uses packet routing to transmit data in the optical domain according to the "clockwork" arrangement, without contention at nodes.
  • the network is as represented in Fig. 1 at a high level, the invention lying in the manner of implementing the network or "torus" nodes.
  • Each network node acts at any one time as a sender node and/or a transit node and/or a receiver node.
  • Each network node contains several optical channel nodes.
  • Each channel node can host a number (maybe several tens or even hundreds) of processors.
  • the total number of processors (number of processors hosted in each channel node x number of channel nodes in a torus node x number of torus nodes in the network) together constitute a supercomputer.
  • the size of the network can be kept small, with n being only of the order of 8 for example while providing a much higher network capacity. This is achieved because each node selects not only a time slot and outgoing link (row or column), but also a wavelength for transmission of each packet.
  • the network is of particular benefit as a supercomputer architecture that consists of large numbers of interconnected individual processors. This allows supercomputers to be scaled to substantially greater computing power than has been achieved to date.
  • the scaling limitation of the prior clockwork architecture is that increasing the size of the torus increases the number of hops between any pair of nodes or processors, thus reducing the available interconnection bandwidth per processor.
  • the invention overcomes this scaling limitation.
  • m the number of distinct wavelengths used on the row or column directions
  • the number of channel nodes in each torus node is 2x32 (for the example configuration of Fig.
  • the contention-resolution unit 71 detects the occurrence of contending requests, and returns control signals to the optical channel nodes indicating grants or denials of permission to use particular time slots and wavelengths.
  • the 2x2 cross-bar switch 75 for a network node is in one embodiment implemented using a passive optical routing device in combination with optical wavelength converters.
  • the architecture is shown in Fig. 5, in which a passive routing device 41 of a node directs an optical signal with wavelength ⁇ i received from input a or b to output c, and directs an optical signal with different wavelength X 1 ' received from input at a or b to output d.
  • Items 42 and 43 are optical wavelength converters which can be switched on or off by control signals at inputs 44 and 45. hi the cross state (Fig.
  • FIG. 7 shows an example of an OEO converter 42.
  • An optical receiver 61 converts an optical signal input on an optical waveguide 66 with wavelength ⁇ p to an electrical data signal.
  • a laser 62 is of a type whose output wavelength can be switched between two values, Xp and X ⁇ ', according to the value of a control signal at a control input 64.
  • the output from the laser is modulated by a modulator 63, which is driven by the electrical data signal obtained from the receiver 61.
  • the node (2,0) selects the row output and time slot 2.
  • the packet is held in an electronic buffer before conversion to an optical signal and transmission into the optical network, and the route selection can be performed in software using a look-up table.
  • the information about incoming packets and outstanding requests to transmit is conveyed from the control unit 83 to the contention-resolution unit 71, which subsequently relays control messages back to the control unit 83.
  • the control unit 83 On the basis of the information and control messages received, the control unit 83 generates control signals 800, 803, 805, 64 and 65.
  • the function of serial the delay unit 84 is to provide a fixed predetermined time delay sufficient to allow the control processing and signalling to be completed, before transferring the electrical data signal to the switch 85. hi accordance with control signal 800, the switch 85 will divert the electrical data signal to either the input buffer 86 or optical modulator 65.
  • the electrical data signal will be diverted to the input buffer 86 in the case that the destination address of the incoming packet is within the optical channel node 80, otherwise the electrical data signal will be diverted to the optical modulator 65 for immediate onward transmission in the network.
  • the input buffer 86 transfers an incoming packet via output 87 to its required destination.
  • Packets to be inserted onto the network are received from processors in the channel node via 801 and are held in output buffer 802.
  • data packets will be transferred at appropriate times to transmission wavelength generator unit 804.
  • the transmission wavelength generator unit 804 emits optical data packets at one of a plurality of wavelengths ⁇ i, ⁇ 2 , ..., ⁇ m , ⁇ ⁇ , ⁇ 2 ', ..., ⁇ m '.
  • the outputs from wavelength selector unit 804 and modulator 63 are combined at optical coupler 806 and pass to optical output 807.
  • Control signal 805 tells the transmission wavelength generator unit 804 which output wavelength is required. This control signal is derived from the routing table.
  • the wavelength selected for the required route is q.
  • the control circuitry is not shown explicitly in Fig. 8.
  • a dedicated control processor chip runs the software needed to hold the routing table and make the appropriate route selection depending on the destination address of a packet. An output from that route selection process is therefore the control signal 805 instructing the transmission wavelength generator unit 804 to select wavelength q.
  • Fig. 8 only one output buffer 802 is shown, it may be advantageous to have a plurality of such buffers which queue outgoing packets according to their priority class or other attributes.
  • Fig. 8 only one output buffer 802 is shown, it may be advantageous to have a plurality of such buffers which queue outgoing packets according to their priority class or other attributes.
  • a packet when a packet is inserted onto the network by an optical channel node, its path through the network from the source to the ultimate destination is entirely determined at the source node by selecting a time slot and wavelength for the packet.
  • This together with the global synchronised switching with a fixed periodicity by the transit nodes passed by the packet on its route from source to destination, ensures delivery to the destination.
  • the transit nodes are not involved in path selection.
  • the only processing required at a transit or destination optical channel node is to determine whether the destination address of the incoming packet matches an address in the node; if there is a match then the destination is reached, otherwise the packet is transmitted onwards.
  • the network could be a torus in which adjacent rows and columns do not alternate in direction.
  • Fig. 1 and the description given above suggests that the links between adjacent nodes are unidirectional, the invention is not limited to that case.
  • the network may be advantageous for the network to contain bi-directional links, in which case each torus node contains two 2x2 crossbar switches and an increased number of wavelength channel nodes each of which takes as its input one wavelength channel on one of the four links entering the torus node (those four links being two opposing row links and two opposing column links).
  • This conf ⁇ guration with bi-directional links is of greater complexity and requires approximately twice as many components; however the advantages include double the communications bandwidth and reduced average shortest path between any pair of torus nodes thus reducing the average communications latency.
  • clockwork routing of data packets in a network has known benefits, including avoidance of the need for a central network controller, thus reducing latency, whilst also eliminating the need for contention resolution at transit network nodes, thus reducing latency, equipment complexity and cost.
  • clockwork routing until now has been the limited bandwidth available and the limited ability to scale the network to large size.
  • clockwork routing can be used to provide an interconnection network for the processors in high-end computing, capable of scaling to sizes substantially greater than the world's largest supercomputers today. This can be illustrated by the following example:
  • guard band 1 ns
  • processors that are hosted by a channel node may be interconnected by a dedicated local interconnection such as a high speed parallel bus. This may be connected to the buffer 802 for the channel node 73 a.
  • a processor wishes to transmit a packet to a processor hosted on a different channel node, it sends the packet to the output buffer 802 where it awaits transmission onwards into the optical interconnection network using the clockwork routing described above, hi this way all of the processors are interconnected together to form a single supercomputer.
  • the invention retains the important advantages of clockwork routing including reduced latency and complexity as compared to the prior art, whilst now allowing a higher degree of bandwidth scaling (or equivalently, whilst allowing the network to interconnect a much greater number of devices).

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Optical Communication System (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

La présente invention concerne un réseau d'interconnexion optique ayant une pluralité de nœuds de réseau (70) interconnectés par des liaisons optiques (76-79). Les nœuds de réseau (70) reçoivent chacun une horloge globale et ils commutent de façon répétée avec une périodicité fixe leurs états de routage en fonction de l'horloge globale. Chaque nœud de réseau (70) sélectionne un intervalle de temps, une longueur d'onde et une liaison optique initiale pour transmettre un paquet en fonction du chemin désiré pour le paquet à travers le réseau et sort le paquet dans l'intervalle de temps, la longueur d'onde et la liaison sélectionnés. La topologie du réseau est un tore du type des rues de Manhattan. Chaque nœud de réseau (70) comprend une pluralité de nœuds de canal (73 a) pour chaque liaison, un démultiplexeur de division de longueur d'onde (72a), un combineur (74a) et un commutateur spatial optique (75). Le commutateur spatial optique (75) a une configuration 2x2. Le commutateur spatial optique (75) a un convertisseur de longueur d'onde (42) par liaison alimentant un dispositif de routage de longueur d'onde passif (41).
PCT/IE2007/000024 2006-02-21 2007-02-21 Reseau de communication optique WO2007096852A1 (fr)

Applications Claiming Priority (2)

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IE20060125 2006-02-21
IE2006/0125 2006-02-21

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2665212A1 (fr) * 2012-05-16 2013-11-20 Alcatel Lucent Système de transmission de données optiques
CN103490820A (zh) * 2013-09-13 2014-01-01 中国人民解放军国防科学技术大学 面向无缓存光互连网络的网络互连装置
CN108696329A (zh) * 2018-08-27 2018-10-23 电子科技大学 基于二维Torus架构的大规模光网络拓扑设计方法

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US6714552B1 (en) * 1996-08-28 2004-03-30 British Telecommunications Public Limited Company Communications network

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US6714552B1 (en) * 1996-08-28 2004-03-30 British Telecommunications Public Limited Company Communications network

Non-Patent Citations (1)

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Title
CHEVALIER F ET AL: "A NEW PACKET ROUTING STATEGY FOR ULTRA-FAST PHOTONIC NETWORKS", IEEE GLOBECOM 1998. GLOBECOM '98. THE BRIDGE TO GLOBAL INTEGRATION. SYDNEY, NOV. 8 - 12, 1998, IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, NEW YORK, NY : IEEE, US, vol. VOL. 4, 8 November 1998 (1998-11-08), pages 2321 - 2326, XP000894452, ISBN: 0-7803-4985-7 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2665212A1 (fr) * 2012-05-16 2013-11-20 Alcatel Lucent Système de transmission de données optiques
KR20150004378A (ko) * 2012-05-16 2015-01-12 알까뗄 루슨트 광학 데이터 송신 시스템
CN104285395A (zh) * 2012-05-16 2015-01-14 阿尔卡特朗讯 光学数据传输系统
KR101657956B1 (ko) * 2012-05-16 2016-09-20 알까뗄 루슨트 광학 데이터 송신 시스템
US9509408B2 (en) 2012-05-16 2016-11-29 Alcatel Lucent Optical data transmission system
CN103490820A (zh) * 2013-09-13 2014-01-01 中国人民解放军国防科学技术大学 面向无缓存光互连网络的网络互连装置
CN108696329A (zh) * 2018-08-27 2018-10-23 电子科技大学 基于二维Torus架构的大规模光网络拓扑设计方法

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