中枢神经系统结构设计,骨干.ppt

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1、Structured Backbone Design of CNs,Habib Youssef,Ph.DDepartment of Computer Engineering King Fahd University of Petroleum&MineralsDhahran,Saudi Arabia,Computer Networks,Outline,1.Enterprise Backbone Basics2.Structured Cabling3.Types of Backbones4.Backbone Examples 5.The Network Development Life Cycle

2、(NDLC),Enterprise Backbone Basics,Modern organizations haveLarge networksComplex communication requirementsAccess to mainframe dataInternetworking of several LANsConnectivity to a WAN(the Internet)Transmission of data and non-data,Backbone Basics(Cont.),Complex requirements mandated the structuring

3、of enterprise-wide information distribution.Such structuring is effectively achieved through a system called Backbone.Structured wiring combined with Backbone solution provide a powerful and efficient networking solution to company-wide communication needs.,Backbone Basics(Cont.),Key Factors in asse

4、ssing network topologies:PerformanceHighest network availability.Lowest latency.Most appropriate connectivity for users.ScalabilityAbility to expand the network in terms of end-points and aggregate bandwidth without affecting existing users.,Backbone Basics(Cont.),Cost of administration:The inherent

5、 ease of moves,adds,and changes,plus the capability to efficiently diagnose,remedy,or prevent network outages.Structured Backbone solutions offerFlexibilityScalabilityTroubleshooting&ManageabilityPerformance,Structured Cabling,Cabling plan should be easy to:implement,andaccommodates future growth.Tw

6、o standards have been issued that specify cabling types and layout for structured commercial buildings wiring.A network should follow a cabling plan:Selection of cable typesCable layout topology,Structured Cabling Standards,EIA/TIA-568:Issued jointly by the Electronic Industries Association and the

7、Telecommunications Industry Assoc.ISO 11801:Issued by the International Organization for Standardization.Both Standards are similar.,Structured Cabling(Cont.),It is a generic wiring scheme with the following characteristics:Wiring within a commercial building.Cabling to support all forms of informat

8、ion transfer.Cable selection and layout is independent of vendor and end-user equipment.Cable layout designed to encompass distribution to all work areas within the building(relocation wouldnt need rewiring).,Structured Cabling(Cont.),Based on the use of a hierarchical star-wired cable layout.Extern

9、al cables terminate at Equipment Room(ER).Patch panel and cross-connect hardware connect ER to Internal Distribution Cable.Typically,first level of distribution consists of Backbone cables.Backbone cable(s)run from ER to Telecom Closets(Wiring Closets)on each floor.,Structured Cabling(Cont.),Wiring

10、Closet contains cross-connect equipment for interconnecting cable on a single floor to the Backbone.Cable distributed on a single floor is called Horizontal Cabling,and connects the Backbone to Wall Outlets that service individual telephone and data equipment.,Structured Cabling(Cont.),Based on the

11、use of a hierarchical star-wired cable layout.,ExternalCable,Telecom.Closet,EquipmentRoom,Backbone,Horizontal,Cable,WorkArea,Structured Cabling Terminology,BackboneA facility between telecommunications closets or floor distribution terminals,the entrance facilities,and the equipment rooms within or

12、between buildingsHorizontal CablingThe wiring/cabling between the telecomoutlet and the horizontal cross-connect,Terminology(Cont.),Cross-ConnectA facility enabling the termination of cable elements&their interconnection,and/or cross-connection,primarily by means of a patch cord or jumperEquipment R

13、oomA centralized space for telecom equipt that serves the occupants of the building(Bldg/Campus distributor in ISO 11801),Terminology(Cont.),Telecommunications Closet:An enclosed space for housing telecom eqpt,cable terminations,and cross-connect cabling;the location for cross-connection between the

14、 backbone and horizontal facilitiesWork AreaA building space where the occupants interact with the telecom terminal eqpt,Terminology(Cont.),Main Cross-ConnectA cross-connect between 1st and 2nd level backbone cables,entrance cables,and equipment cables(no ISO name)Intermediate Cross-ConnectA cross-c

15、onnect between 1st and 2nd level backbone cabling(no ISO name),Terminology(Cont.),Horizontal Cross-Connect:A cross-connect of horizontal cabling to other cabling,e.g.horizontal,backbone,or equipment(no ISO name)Telecommunications OutletA connecting device in the work area on which horizontal cable t

16、erminates,Media Recommended,Telecomm.Outlet,HorizontalCross-connect,MainCrossconnect,IntermediateCross-connect,Telecomm.Outlet,HorizontalCross-connect,A,C,B,D,D,Cable Distances,UTP(Voice Transmission)MC-HC HC-ICMC-ICTO-HCA BC D 800m500m 300m90mCat 3 or 5 UTP(up-to 16 or 100 MHz),and STP(up-to 300 MH

17、z)A BC D 90m90m 90m90m,Cable Distances(Cont.),62.5 microns FiberMC-HC HC-ICMC-ICTO-HCA BC D 2000m500m 1500m90mSingle-Mode FiberA BC D3000m500m 2500m90m,Unstructured Backbone-Mainframe,Terminals,Mainframe,.,.,.,Cluttered and noisycable risers,.,.,.,Unstructured Backbone-LAN,Each station must be physi

18、cally connected by a thick coax tapped to the LAN coax,running by all stations.,Structured Backbone,By using a MUX or similar device,a backbone can be structured.A single fiber pair replaces mounds of coax cable,andfloor-to-floor traffic is systematically organized.With Structure comes enhancednetwo

19、rk controlreliability,andefficiency.,Structured Backbone(Cont.),Structured backbone=structured,hierarchical physical star wiring scheme.,Mainframe,MUX,MUX,MUX,Structured Backbone(Cont.),The first information backbone emerged in the mid 1980s.An enterprise backbone is an aggregate data path(a central

20、 communication highway)for the transport of all signals to/from users distributed throughout the enterprise.Early backbones were mainly muxes.,Structured Backbone(Cont.),The enterprise network is usually comprised of three main parts:The horizontal access portion:Connecting individual workstations t

21、o wiringclosets and most often accomplished via anintelligent cabling Hub.The Backbone portion:Facilitating floor-to-floor or building-to-buildingconnectivity.,Structured Backbone(Cont.),The Wide Area Network link,Horizontalaccess,Backbone,WANInterface,When are Backbones needed?,Companies utilizing

22、Backbone techno-logy have typically one or more of the following communication needs:Multiple data protocols and signals.Heavy network traffic to be supported simultaneously.Multiple workgroups,networks,and facilities that need to be internetworked.Mission critical applications where high reliabilit

23、y and security are mandatory.,When are Backbones needed?(Cont.),Need to support varying media and device types.A high degree of upgradeability,so that existing equipment can be preserved and higher performance hardware and software solutions can be implemented seamlessly.A high degree of network mov

24、es,adds,and changes,requiring that the enterprise network be highly manageable.,Types of(private)Backbones,Three broad categories:(1)Multiplexers-based.(2)LAN Backbones.FDDI,Ethernet,Token Ring,etc(3)Collapsed Backbones.High-speed Router,ATM.,Public Backbones,Public telephone/data network,Backbone T

25、opologies,StarCollapsed BackbonePBX systemSwitch-based networks,Backbone Topologies(Cont.),Ring.Ex:FDDI.,Backbone Topologies(Cont.),Hierarchical/Inverse Tree.Higher power at higher levels.,Backbone Topologies(Cont.),Mesh.Multiple data paths between peer stations.Topology relies on the use of Routers

26、.,Backbone Benefits,+Makes complex distributed computing environment easier to manage.+Allows Organizations to easily upgrade the system.+Creates an integrated communication path capable of accommodating the enterprises data transfer requirements safely and cost effectively.,Fiber Optics,Many of the

27、 Backbone advantages are enabled by the implementation of fiber.Advantages of fiber:+Ability to combine data,voice&video signals over a single fiber pair.+Very large bandwidth:(allows large number of users,is cost effective and space-conservative).+Increased data security&reliability.,Application/Ba

28、ndwidth,High capacity Backbone is a must to support increasing need for bandwidth.ApplicationBandwidth Digital audio1.4 Mbps Compressed video(JPEG)2-10 Mbps Document Reprographics20-100 Mbps Compressed broadcast-quality TV20-100 Mbps High-definition full motion video1-2 Gbps Chest X-Ray4-40 Mbps Rem

29、ote query burst1 Mbps,Multiplexer-Based Backbones,The first Backbones were Mux-based.Designed for and continued to be used predominantly in the mainframe environment.Suitable for situations when a mixture of LAN and host-to-terminal traffic needs to be supported via a common Backbone.A Mux is a devi

30、ce that simultaneously transmits several messages or signals across a single channel or data path.,Multiplexer-Based Backbones,Two primary types of Backbone Muxes in use today:Time Division Mux(TDM).Statistical or Stat Mux.,Time Division Muxes,A TDM combines signals onto a high speed link,and then s

31、ends those signals sequentially at fixed time intervals.Each user interface is allocated a time slot within which its data is transmitted.Data is usually sent one char at a timeCombined signal rates 100 Mbps.,Time Division Muxes,Ethernet,Token Ring,Mainframe,Ethernet,Token Ring,Mainframe,MTEMTE,MTEM

32、TE,.,.,.,Aggregate pathway,Muxing,De-Muxing,TDM Strengths,+Dedicated bandwidth partitions=Guaranteed throughput&no loss.+Versatile&scaleable.+Low cost compared to Stat.TDM.+Proven Reliable data transport.,TDM Weaknesses,-Bandwidth of idle sources is lost.-Minimal internetworking capability.,Statisti

33、cal TDM,Based on the premise that stations rarely need to transmit data constantly at full available speed.Attempts to move as much data as possible across the common channel.Combined bandwidth of all sources exceeds the available bandwidth.Allocates time slots on-demand,constantly evaluating traffi

34、c needing to be sent(based on priority).,Stat-Mux(Cont.),In case demand exceeds capacity,lower-priority traffic is off-loaded into a buffer and delayed for retransmission during a non-peak period=More complex front-end management.Greater degree of intelligence.Greater computer power.,Stat-Mux Streng

35、ths,+Supports more data than available bandwidth=better bandwidth utilization.+Critical data can be given higher priority.,Stat-Mux Weaknesses,-Requires more management and more expensive to operate.-Low priority data can suffer excessive delays.-Data may get lost.(No guaranteed bandwidth),Emerging

36、Backbone Technologies,Three of the most promising Backbone technologies are:Asynchronous Transfer Mode(ATM).Synchronous Optical Network(SONET).Fibre Channel.,ATM,Todays collapsed Backbones are based on Router technology.Tomorrows collapsed Backbones will be based on switching technology.ATM is predi

37、cted to be at the core of the switching technology.ATM is hailed as the first solution that will erase the barriers between LANs and WANs.,ATM(Cont.),ATM,ATM,Server,WANInterface,Router,Backbone,ATM Benefits,+Combines best features of Muxes and LAN Backbones.+ATM rides on top of a highly scaleable ph

38、ysical layer protocol such as Fiber channel and SONET.+Short&fixed-length cells=Relatively low cost hardware implementation.+Can accommodate both real-time and non-real-time data.,ATM Benefits(Cont.),+Provides high throughput.+ATM is not protocol-dependent.Any packet format can be mapped into ATM ce

39、lls and transported.=It is an ideal data transfer system for changing LAN environments.,How ATM Works?,Data Units:Fixed-length cells of size 53 bytes each(5 Header+48 payload).Operates at the equivalent of MAC sublayer.Operates above physical layer which could be SONET,Fibre channel,.Connection-orie

40、nted.Universal transfer mode for all B-ISDN services.Layered architecture.,ATM Layered Architecture,Higher Layers,User Services&applications,ATM Adaptation Layer,ATM Layer,Physical MediumDependent Layer,Fragmentation andde-fragmentation of frames,Cell header insertion/removalCell relaying&multiplexi

41、ngConnection establishment,Transmission&receipt of bitsSynchronization,How ATM Works?,Data packet,AAL,ATM,Physical Layer,How ATM Works(Cont.)?,Physical Layer,ATM,Entire process is reversed,Overhead,Envelope,Cell,Examples of ATM Switches,FORE SystemsASX-200BX(2.5 Gbps backplane)ASX-1000(10 Gbps backp

42、lane)CISCO SystemsNWAYS 8260(5 Gbps backplane)Bay NetworksCentillian-100:campus ATM switch(3.2 Gbps backplane),Examples of ATM Switches(Cont.),IBM NWAYS 8260(5 Gbps backplane)MADGE NetworksCollage 740:Campus ATM switch(5 Gbps backplane)ALCATEL1100 LSS Series 550A,Synchronous Optical Network,SONET is

43、 ANSI&ITU Standard.First standard optical interface.Used in the public network and is being adopted as a private Backbone solution.American SONET Standard:Rates start at OC-1:51.84 MbpsScaling up to OC-48:2.48 Gbps,SONET(Cont.),European SDH:Initial Rate:SDH-1=OC-3:155.52 MbpsSONET provides a transpo

44、rt payload envelope and framing format.Any type of data is transparently transmitted with low delays.SONET is currently defined for use with single mode fiber.,Fibre Channel,ANSI X3T9.3 Standard.Developed as high speed interface for linking mainframes and their peripherals.Better suited as a private

45、 Backbone becauseless overheadlowest implementationmulti-mode fiber,Fibre Channel(Cont.),Is also highly expandableInitial Rate:100 MbpsScales up to:1.6 GbpsHas a transport payload envelope,LAN Backbones,Unlike Muxes which are capable of transmitting an array of data,host-to-host,voice and video sign

46、als,LAN Backbones are dedicated exclusively for LAN communication.Actually,any legacy LAN such as Ethernet or Token Ring can be called a backboneLANs constitute the primary datapaths.,LAN Backbones(Cont.),In the broader context of Backbones,the key LAN standard that has far-reaching Backbone-based a

47、pplications is the Fiber Distributed Data Interface(FDDI).FDDI is(still?)the dominant LAN Backbone in use.It provides standards-based connectivity for legacy LANs(Ethernet&Token Ring).,LAN Backbones(Cont.),Token Ring,Ethernet,Token Ring,Ethernet,Ethernet,Token Ring,All of the protocols areconverted

48、to the FDDI transport protocol,Data is Bridged/Routed from the high-speed Backbone to destination LAN,LAN Backbones(Cont.),FDDI complements existing LANs by providing a high-speed path upon which all LAN protocols can be transported.Typical FDDI applications:Backbone connectivity between LANs in a b

49、uilding or campus.LAN for high-end graphics&CAD/CAM workstationsConnection device for host-to-host or Backbone-to-Backbone applications.,FDDI Strengths,+FDDI is tailor-made and very effective as a high-speed LAN for workstation traffic and as a Backbone for LANs.+Provides a framework for inter-netwo

50、rking between various LAN protocols.,FDDI Strengths(Cont.),+Compared to legacy LANs,FDDI provides greater data capacity and performance,transmitting at 100 Mbps.+Can accommodate large networks of up to 500 Backbone nodes.,FDDI Strengths(Cont.),+Because of its dual-ring architecture,FDDI offers a hig