1 Making Networks Work ITEC 370 George Vaughan Franklin University.
1 Lecture 11: Computer Systems and Networks ITEC 1000 “Introduction to Information Technology”
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Transcript of 1 Lecture 11: Computer Systems and Networks ITEC 1000 “Introduction to Information Technology”
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Lecture 11:Lecture 11:Computer Systems and NetworksComputer Systems and Networks
ITEC 1000 “Introduction to Information Technology”
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Lecture Template:Lecture Template:
System Performance ImprovementSystem Performance Improvement MultiprocessingMultiprocessing Computer InterconnectionComputer Interconnection OSI model and TCP/IPOSI model and TCP/IP Network TopologiesNetwork Topologies Protocols Protocols Wide Area NetworkWide Area Network High Performance ComputingHigh Performance Computing
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System Performance System Performance ImprovementsImprovements
Multiple CPUsSharing memory and I/O facilitiesConflict among the CPUs for shared resources
Faster clock speed, buses and circuitsImproving technology to design faster CPU circuits and buses
Wider instruction and data pathsWider interface between the CPU and memory allows to fetch more data in a single operation
Faster disk accessSmaller discs, more density packed, increased storageRAID: data on different discs, multiple access simultaneously
More and faster memoryReduces the time to access instructions and data
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MultiprocessingMultiprocessing
ReasonsIncrease the processing power of a systemParallel processing
Types of multiprocessor systemsTightly coupled systemsLoosely coupled systems
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Tightly Coupled SystemsTightly Coupled Systems
Also called multiprocessor systems Identical access to programs, data,
shared memory, I/O, etc. Easily extends multi-tasking, and
redundant program execution Two ways to configure
Master-slave multiprocessingSymmetrical multiprocessing (SMP)
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Master-Slave MultiprocessingMaster-Slave Multiprocessing
Master CPUManages the systemControls all resources and schedulingAssigns tasks to slave CPUs
AdvantagesSimplicityProtection of system and data
DisadvantagesMaster CPU becomes a bottleneckReliability issues – if master CPU fails entire system fails
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Symmetrical MultiprocessingSymmetrical Multiprocessing
Each CPU has equal access to resources Each CPU determines what to run using a
standard algorithm Disadvantages
Resource conflicts – memory, i/o, etc.Complex implementation
AdvantagesHigh reliabilityFault tolerant support is straightforwardBalanced workload
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Loosely Coupled SystemsLoosely Coupled Systems
Clusters or multi-computer systems Each system has its own CPU, memory, and
I/O facilities Each system is known as a node of the
cluster Advantages
Fault-tolerant, scalable, well balanced, distance is not an issue
Two ways to configureShared-nothing modelShared-disk model
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Shared-Nothing ModelShared-Nothing Model
High speed link between nodes No sharing of resources Partitioning of work through division
of data Advantage
Reduced communication between nodes Disadvantage
Can result in inefficient division of work
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Shared-Disk ModelShared-Disk Model
High speed link between nodes Disk drives are shared between nodes Advantage
Better load balancing Disadvantage
Complex software required for transactional processing (lock, commit phases)
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Computer InterconnectionComputer Interconnection
Communication channel – pathway for data movement between computers
Point-to-Point connectivityCommunication channel that passes data directly between two computersSerial connectionTelephone modemTerminal controller – handles multiple point-to-point connections for a host computer
Multipoint connectivityMultidrop channel or shared communication channel
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DefinitionsDefinitions
Topology: the way in which loosely coupled computers are interconnected
Synonym: configuration
Protocol: a set of rules and standards for communications between computers
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Client-Server ArchitectureClient-Server Architecture
Computer server provides servicesFile storage, databases, printing services, login services, web services
Client computersExecute programs in its own memoryAccess files either locally or can request files from a server
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Beowulf ClustersBeowulf Clusters
Simple and highly configurable Low cost Networked
Computers connected to one another by a private Ethernet networkConnection to an external network is through a single gateway computer
ConfigurationCOTS – Commodity-off-the-shelf components such as inexpensive computersBlade components – computers mounted on a motherboard that are plugged into connectors on a rackEither shared-disk or shared-nothing model
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LAN TopologyLAN Topology
Arrangement of workstations in a shared medium environment
Logical arrangement (data flow) Physical arrangement (cabling
scheme)
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Network TopologiesNetwork Topologies
Bus: Nodes are connected to a common bus with a terminator on each end.
Ring: Similar to bus, but bus is closed - no ends.Star: A central node does most of the processing. Remote
nodes are connected point-to-point with it.Loop: Similar to ring but nodes are directly in
communication path.Hierarchical: A tree-like structure emanating from a central or
root node.Web: Everything connected to everything else.
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LAN Topologies: RingLAN Topologies: Ring
Repeaters are joined by unidirectional point-to-point links in a ring
As data circulates past a receiver, the receiver checks its address, and copies those intended for it into a local buffer
Data circulates until it returns to source, which removes it from network
Better performance at high levels of usage
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LAN Topologies: Bus
Multipoint medium Stations attach to linear medium (bus)
using tap Transmission from any stations
travels entire medium (both directions)
Termination required at ends of bus to prevent the signal from bouncing
Break in cable brings down entire bus
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LAN Topologies: TreeLAN Topologies: Tree
Generalization of bus topology Branching cable with no closed loops Cable(s) begin at headend, travel to
branches which may have branches of their own
Each transmission propagates through network, can be received by any station
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LAN Topologies: StarLAN Topologies: Star
Each station connected point-to-point to a central station, usually with two unidirectional links
Switching in the central station connects pairs of nodes together
Central node can broadcast info, or can switch frames among stations
Failure of central station causes entire network to go down
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Topology Selection: FactorsTopology Selection: Factors
Distances between stations Layout of the room/building Overall size of the network Distance between the most remote
nodes Speed requirements Network traffic Total number of stations
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Medium Access Control (MAC) Medium Access Control (MAC) ProtocolsProtocols
Characteristics of the channels, data rate, voltage levels, etc.
Node access to the channel (medium access control protocol)
Steer data to its destinationDetect errorsPrevent multiple nodes from accessing the network simultaneously (collision)Ethernet and token ringImplemented in hardware
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Ethernet MAC ProtocolEthernet MAC Protocol
MAC – Medium Access Control Ethernet and CSMA/CD
Carrier sense multiple access with collision detection
Four step procedureIf medium is idle, transmitIf medium is busy, listen until idle and then transmitIf collision is detected, cease transmittingAfter a collision, wait a random amount of time before retransmitting
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Token Ring MAC ProtocolToken Ring MAC Protocol
Token “seized” by changing a bit on the circulating frame to indicate start of frame rather than token
Default configuration requires sender to complete transmission and begin receiving transmitted frame before releasing the token
“Early token release” allows release of token after transmission but before receipt of frame
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HubsHubs
The active central element of the star layout
When a single station transmits, the hub repeats the signal on the outgoing line to each station
Hubs can be cascaded in a hierarchical configuration
Ethernet hubs are physically a star but logically a bus
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BridgesBridges
Allow connections between LANs and to WANs
Used between similar networks Read all frames from each networkAccept frames from sender on one network that are addressed to a receiver on the other networkRetransmit frames from sender using MAC protocol for receiver
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GatewaysGateways
Similar to bridges but connect dissimilar networks
Convert format of the message to correspond to the protocol of the other network
Network traffic is specifically addressed to the router
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Wide Area NetworkWide Area Network
Circuit switchingDedicated channel between source and destination for duration of connection
Message switchingDedicated channel for an entire message
Packet switchingAn independent path is created for each datagram
Virtual circuit switchingA route is created from source to destination before transmission begins and all datagrams are sent using the same route
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Networks vs. ClustersNetworks vs. Clusters
Externally, clusters appear as a single computing unit
Network nodes are individually identifiable
Workload on a cluster is determined by cluster administration and load-balancing software
Network workload cannot be controlled using the above method
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High Performance ComputingHigh Performance Computing
Massively parallel processor architectures (MPP)
Clusters of power machines or larger Beowulf blade clusters
Well suited for problems that can be broken into subtasks
Grid computingSupercomputer performance through distributing CPU processing to the spare CPU cycles of personal computers connected to a network