try Flashcards
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data
messages to be shared between sender and receiver
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what does protocols establish ?
Protocols establish accurate and appropriate meaning to the messages that are understood by both senders and receivers
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is the physical connection dependent of the physical connection ?
▪ Physical connection that is independent of the messaging ▪ message sharing “connection” between applications at the sender and the receiver ▪ physical connection with signaling that represents the messages being transported
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examples of the Physical connection
▪ Examples ▪ POTS - plain old telephone service ▪ Web servers and Web browsers
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HTTP Request and Response
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Model of a Communication Channel
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what are the limitations of communication tool
▪ Limitation as a communication tool is the varying message length ▪ Long messages could tie up a communication channel indefinitely creating problems for other messages that share that channel
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what are the packets ?
* A group of related packets make up a single message ▪ Consist of data encapsulated by the packet header which contains information about the packet
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what are the packets used ?
▪ Used to solve problems of channel availability and maximum utilization ▪ Equivalent to an envelope that contains pages of data
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what is the packet Header named ?
▪ Also known as the preamble
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what does the packet header contain?
▪ Contains * Description of the packet * Destination address of receiver * Source address of sender * Information about the data being sent
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Advantages of Packets?
- ▪ Simplifies operations and increases communications efficiency 2. ▪ Reasonable unit for routing of data 3. ▪ Alternative to dedicating a channel for the entire length of the message 4. ▪ Packets from several sources can share a single channel 5. ▪ Each sender/receiver pair appears to have a channel to itself 6. ▪ Receiving computer can process an entire block of data instead of a character or byte at a time 7. ▪ Simplifies synchronization of the sending and receiving systems by providing clear start and stop point
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what is the communication channel ?
▪ The path for the message between two communicating nodes ▪ May include intermediate nodes that forward packets to the next node ▪ Interfaces at each end of the connection may be differen
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what is ▪ Links?
▪ A segment of a communication channel
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what is the bandwidth ?
▪ Bit rate of overall channel
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what is ▪ Medium parts ?
▪ Guided – communications limited to a specific path ▪ Unguided – communications not limited to a specific path
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A Multi-Link Channel
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/image7sz7qx-14A5C9702F52BAAF49D.png
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what are the ▪ Data transmission directionality?
▪ Simplex – messages are carried only in one direction ▪ Half-duplex – messages are carried in both directions but only one direction at a time ▪ Full duplex – messages are simultaneously carried in both directions
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what are the numbers of connections ?
▪ Number of connections ▪ Point-to-point ▪ Multipoint
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types of signaling ?
▪ Digital vs. Analog
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what are End node interfaces types ?
▪ Wired or wireless Ethernet ▪ Bluetooth, WiMax, DSL or cable link, modem, etc.
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what are the types of Packet Routing ?
- Circuit switching 2. Virtual circuit 3. Packet switching (datagram switching )
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what are the circuit switching ?
▪ Circuit switching ▪ Dedicated channel between source and destination for duration of connection
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what are the ▪ Virtual circuit
Virtual circuit ▪ A channel path that is used to send packets between two end nodes ▪ Intermediate nodes may be shared with other channel paths
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what are the packet switching ?
▪ Packet switching (datagram switching) ▪ Each packet is routed from node to node independently based on various criteria
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End-to-end channel with many possible paths through intermediate nodes diagram
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_183-14A5C9FE5A17ACA9A06.png
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Virtual Circuits in a Network diagram
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_184-14A5CA0907B479F38C0.png
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Connecting End Points through Links and Networks diagram
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_185-14A5CA10D68611A3141.png
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what are routers ?
▪ Specialized devices used to interconnect network and pass packets from one network to another
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what ARE the operations
When packet arrives at input port Processor decides where packet is to be directed A switch is set to direct the packet to the correct output port
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what are getaways and what do they do ?
▪ Same as routers but connect dissimilar networks together ▪ Convert packet headers for the dissimilar network
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what are the Communication Models
▪ TCP/IP ▪ OSI
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what are the network addressing
▪ Network Topology
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what are the types of networks ?
- Local Area Networks 2. Backbone Networks 3. Metropolitan Area Networks 4. Wide Area Networks 5. Internet Backbones and the Internet 6. Piconets
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how is the communication model is implemented ?
▪ Implemented as a hierarchical protocol stack ▪ Each layer of the stack at the sender node contributes information that is used by the corresponding peer layer at the receiver node
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why different protocols for ?
Different protocols for the different aspects of communication
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17 advantages of Separating tasks and including well defined interfaces between the tasks?
* Adds flexibility * Simplifies design of protocols * Permits modification or substitution of protocols without affecting unrelated tasks * Permits a system to select only the protocols needed for a particular application
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18 TCP/IP?
Transmission Control Protocol/Internet Protocol
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what does the TCP and IP encapasses ?
The TCP/IP protocol suite encompasses an integrated suite of numerous protocols that work together and guide all aspects of communication.
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Operation of TCP/IP Model daigram
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Application Layer (Layer 5) what does do ?
▪ Layer where message is created ▪ Includes any application that provides software that can communicate with the network layer
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from what sockets are Originated ?
Originated with BSD UNIX
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what does sockets provide ?
* Provide the interface between the application layer and transport layer * Used by applications to i nitiate connections and to send messages through the network * A means for adding new protocols and keeping the network facilities current in their offerings
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example for sockets ?
Example: SCSI over IP
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what does transport layer does ?
▪ Provides services that support reliable end-to-end communications ▪ Generates the final address of the destination ▪ Responsible for all end-to-end communication facilities ▪ Packetization of the message, breaking up of the message into packets of reasonable size takes place at this level
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where does the Packetization of the message, breaking up of the message into packets of reasonable size takes place?
Transport Layer (Layer 4)
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where does the Generates the final address of the destination?
Transport Layer (Layer 4
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▪ Three different protocols of the Transport Layer (Layer 4)?
▪ TCP ▪ UDP ▪ SCTP
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advantages of the TCP? (Transmission Control Protocol)
▪ Reliable delivery service ▪ Sending and receiving TCP each create a socket ▪ Control packets are used to create a full duplex connection between the sockets ▪ A single TCP service can create multiple connections that operate simultaneously by creating additional sockets as needed ▪ Routing is the responsibility of the network layer (layer 3
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talk about the ▪ UDP (User Datagram Protocol)?
▪ Unreliable, connectionless service ▪ No acknowledgment of receipt by receiving node ▪ Example: streaming video
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example of the UDP ?
▪ Example: streaming video
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what is the SCTP ?
Similar to TCP but with improved fault tolerance and ability to transport multiple messages through the same connection
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what is the Logical Connection View of TCP daigram ?
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what is the Network layer called ?
▪ The TCP/IP network layer is also called the internetworking layer or the IP layer
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what is the responsible for the network layer ?
Responsible for the addressing and routing of packets to their proper and final destination
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traits of the network layers ?
▪ Unreliable, connectionless, packet switching service * Does not guarantee delivery nor check for errors
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what are routers and getaways refereed to ?
Routers and gateways are sometimes referred to as level 3 switches to indicate the level at which routing takes place
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what does the network layer do during Communications within a local network?
* No routing is required because nodes are directly addressable ▪ Physical addresses for corresponding IP addresses are looked up in a table ▪ IP appends a header with the physical address and passes the datagram to the data link layer (layer 2)
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what does the network layer do Communications sent outside of the local network?
▪ At each intermediate node, the network layer removes the current node address and determines the next node address ▪ The new address is added to the packet and passed to the data link layer (layer 2)
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what does the Data Link Layer (Layer 2) do ?
▪ Responsible for the reliable transmission and delivery of packets between two adjacent nodes
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what are packets called in the data link layer ?
n Packets at this layer are called frames
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What are the 2 sub layers of the Data link layer?
- software Logical Link Control (LLC) - establish control of logical links btwn local devices on network 2. hardware Media Access Control (MAC) - device use to control access to network medium
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traits of the Software logical link control sublayer?
* Error correction, flow control, retransmission, packet reconstruction and IP datagram/frame conversions * Numbers frames and reorders received frames to recreate the original message * Rarely used
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what are the traits of the Hardware medium-access control sublayer?
* Defines procedures for access the channel and detecting errors * Responsible for services such as data encoding, collision handling, synchronization, and multiplexing
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what takes place at the physical layer ?
Layer at which communication actually takes place consisting of a bare stream of bits
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where is the physical layer implemented ?
▪ Primarily implemented in hardware by a network interface controller (NIC)
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in the physical layer what does the Physical access protocol includes?
▪ Definition of the medium ▪ Signaling method, signal parameters, carrier frequencies, lengths of pulses, synchronization and timing issues ▪ Method used to physically connect the computer to the medium
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Passing a Message Through an Intermediate Node diagram ?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/image1n3irx-14A5C86D25F4E8764EC.png
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OSI Model what does it stand for ?
Open Systems Interconnection Reference Model was created by the International Standards Organization (ISO)
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is it important the OSI model ?
▪ Although a conceptually important model, OSI is not widely accepted or used for actual communication
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how many layers the OSI consists of ?
▪ Contains seven layers instead of five ▪ The application layer in the TCP/IP model is essentially represented by three layers in the OSI model ▪ Application layer ▪ Presentation layer ▪ Session layer
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Comparison of OSI and TCP/IP diagram ?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/image5xcbrx-14A5C8971A233C5B7A8.png
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what is OSI Presentation Layer Different protocols for the different aspects of communication
▪ Responsible for presenting data at the destination with the same meaning and appearance as it would have at the source ▪ Provides common data conversions and transformations that allow systems with different standards to communicate
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what does OSI Presentation Layer include ?
Includes services such as data compression and restoration, encryption and decryption, data reformatting, ASCII-Unicode conversion, etc.
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what does the OSI session layer establishes ?
▪ Establishes a dialogue between two cooperating applications or processes at the ends of the communication link
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what is OSI Session Layer ▪ Responsible for?
▪ Establishing the session between the applications ▪ Controlling the dialogue ▪ Terminating the session
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examples of the OSI session layer are ?
Examples ▪ Remote login ▪ Print spooling to remote printer
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TCP/IP Addressing (1) what type of addresses used ?
▪ User friendly addresses ▪ URL – www.youtube.com ▪ Email – somebody@yahoo.com ▪ Printer name on the network
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what is the domain name ?
▪ Standard global domain name system provides global scope for user friendly addresses ▪ Hierarchical system for name creation and registration ▪ Tools for locating and identifying specific names
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traits of port addresses TCP/IP addressing ?
▪ Port Addresses (port numbers) ▪ Transport layer uses to identify the application that is to receive the message
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what is the length of the port addressed ?
▪ 16 bits in length
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example of the length of the port addresses ?
Example: port 80 is commonly used for Web services ▪ First 1024 numbers are called well-known ports because they are standard addresses specified for most common applications
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what is the defined port numbers are also available to ??
applications
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example of the ▪ Port Addresses (port numbers)
▪ For example, the following Web service uses the user- defined port of 8080 http://www.somewhere.org:8080/hiddenServer/index.html
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daigram of the Well-Known Port Addresses
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TCP/IP Addressing (3)▪ IP addresses ▪ IP addresses traits of IPv4 ?
* 32-bit addresses arranged as 4 octets, delimited by dots * Each octet is written as a decimal number between 0 and 255 * Example: 208.80.152.2 (Wikipedia’s IP address)
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traits of IPv6
* Intended to eventually supplant IPv4 to provide additional IP addresses * 128-bit addresses arranged as 8 groups of four-digit hexadecimal * numbers separated by colons * Leading zeros and zero values in one or more consecutive groups may * be eliminated * Example: 6E:2A20::35C:66C0:0:5500 is the same as * 006E:2A20:0000:0000:035C:66C0:0000:550
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TCP/IP Addressing (4) what is ▪ Domain name translation
▪ Translate a user friendly address into an IP address and port address for the transport layer ▪ Utilizes a global domain name directory servic
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what does ▪ Address resolution protocol (network layer) do ?
▪ Translates IP addresses into physical addresses
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what is ▪ MAC (medium-access control) address
▪ Most common type of physical address ▪ Every manufactured device that may connect to a network anywhere in the world is supplied with a permanent, unique MAC address ▪ Format consists of 48 bits arranged as 6 two-digit hexadecimal numbers separated by colons ▪ Example: 00:C0:9F:6C:F9:D0
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diagram of the Different Addresses Used in a Network
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imagev46erx-14A5CB78A12613DFA9F.png
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what is Network Topology
Fundamental layout of a network
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what does Network Topology describe ?
▪ Describes the path or paths between any two points in the network ▪ Affects availability, speed and traffic congestion of the networ
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types of Network Topology?
▪ Logical topology – operational relationship between the various network components ▪ Physical topology – actual layout of the network wiring
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Automobile Traffic Scenarios
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Four Network Topologies
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what is Mesh Topology
Multiple paths between end nodes
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what are the limitations of the mesh topology ?
▪ Failure of an individual intermediate node will slow but not stop the network as long as an alternative path is available
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▪ Large networks that use switches and routers are typically
partial mesh networks
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Full mesh network
- Direct point-to-point channel connecting every pair of nodes 2. Impractical due to the large number of connections needed 3. Number of connections = nodes x (nodes – 1) / 2 4. 500 computer nodes would require 125,000 interconnecting cables
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Five-Node Full Mesh Network diagram ?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imageaw4hrx-14A5CBE06FF76B1A028.png
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how is the lay of the bus topology ?
▪ To communicate, each node “broadcasts” a message that travels along the bus ▪ Every node on the bus receives the message but it is ignored by all nodes except the one whose node matches the delivery address in the message
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what does the transmission of the bus Topology ?
▪ Transmission from any stations travels entire medium (both directions) ▪ Termination required at ends of bus to prevent the signal from echoing
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can Branches be added to a bus?
Branches can be added to a bus, expanding it into a tree but messages are still broadcast throughout the entire tree
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how to implement bus network?
▪ Only requires a single pair of wires from one end of the network space to the other
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advantage of the bus network ?
▪ Easiest to wire of the network topologies ▪ Low cost
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issues of the bus network?
▪ Traffic congestion is a major issue
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why bus network Rarely used in designs of new networks except for wireless networks?
▪ Because of the unguided nature of radio waves, wireless networks require some form of bus topology
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when does the star network used?
▪ Primarily used for local area networks and sometimes used to connect satellite offices to a central office
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how is the nodes connected in the star topology?
▪ All nodes are connected point-to-point to a central device ▪ Nodes communicate through the central device ▪ Switching in the central device connects pairs of nodes together to allow them to communicate directly
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what does the Central device of the star topology?
Central device can steer data from one node to another as required
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is it possible to switch multiple pairs
▪ Most modern switches allow multiple pairs to communicate simultaneously
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limitations of the star topology ?
▪ Failure of central device causes entire network to go down
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how Ring Topology works
▪ Point-to-point connection from each node to the next ▪ Last node is connected back to the first to form a closed ring ▪ Each node retransmits the signal that it receives from the previous node in the ring ▪ Packets are placed on the loop at a node, and travel from node to node until the desired node is reached
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Although the ring is inherently unidirectional, it is possible to build a
bidirectional ring network
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is it popular in the past Ring topology?
▪ Popular in the past because they provided a controlled way in which to guarantee network performance ▪ Legacy token-ring local area networks ▪ Used in some FDDI fiber optic backbone and metropolitan area networks
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what is Local Area Networks (LAN)?
▪ A network that connections computers and other supporting devices over a relatively small localized area
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what is the size of Local Area Networks (LAN)?
▪ Typically ranging in size from a single room to multiple buildings in close range of each other ▪ Most of the computers are personal computers or workstations
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is Routers and perhaps gateways are used to connect the LAN
▪ Routers and perhaps gateways are used to connect the LAN to other networks
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how to minimize extraneous traffic on the network?
Creating separate LANs for different departments or for different business functions is done to minimize extraneous traffic on the network
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what protocol LAN is base on?
Most modern LANs are based on one of the Ethernet protocol standards
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Common Ethernet Standards diagram
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imageoylhrx-14A5D0DDE8D65A8F480.png
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what is the Ethernet Hubs based on ?
Based on bus topology
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how to to simplify wiring and maintenance in Ethernet Hubs?
▪ A passive central connection device used to simplify wiring and maintenance
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what does the physical layer does in the Ethernet Hubs ?
▪ Physical layer device where all of the connections are tied together inside the hub
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how the signaling of the Ethernet Hubs ?
▪ Signals are broadcast to every device connected to the hub
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what are MACP in the Ethernet Hubs ?
Uses the CSMA/CD medium access control protocol
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why is the hubs in the Ethernet is declining
Use of hubs is declining because switches often provide better performance
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Ethernet Switches what topology it uses ?
Logically a star topology, not a bus topology
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the ability of the Ethernet switches ?
▪ Able to set up a direction connection between any two nodes ▪ Multiple pairs of nodes can communicate at the full bandwidth
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what method is Ethernet Switches ?
Prevalent method for wired local area networks
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Hub vs. Switch Based Ethernet
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Wireless Ethernet (WiFi) how
* Radio-based compatible extension to the Ethernet standard ▪ Central access point is similar to a hub but is an active node ▪ Central access point transmits and receives radio waves to communicate with the nodes
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Radio space requirement ?
▪ Radio space must be shared between the nodes
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why is the Wireless Ethernet (WiFi) Does not use the CSMA-CD protocol?
Does not use the CSMA-CD protocol because it is possible for units to be far away that although they can communicate with the access point, they cannot detect one another
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Wireless Ethernet Characteristics
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imagew7ebrx-14A5D1D7EFD0AF1736A.png
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Wireless Mesh Network
Mesh points operate at the medium-access control layer and do not require wiring
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what is Backbone Networks also called ?
Also called tiered Ethernet
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what does the backbone networks do ?
▪ Ties together LANs and provides access to external networks like the Internet
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what is the Chief motivation of Backbone Networks ?
Chief motivation is to improve overall performance of a larger network by creating separate networks for groups of users who primarily communicate with one another
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when in the backbone networks Communicate between the LANs is enabled?
Communicate between the LANs is enabled only when necessary
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did you know that
in Backbone Networks Overall range of the network can be extended beyond the limits of a single LAN Can be viewed as a large LAN where each node is itself a LAN
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example of the backbone networks ?
Intranets – an organizational network where user interfaces and applications are primarily based on Web services
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Backbone Network
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imageeekerx-14A5D2543935633B090.png
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what is the Metropolitan Area Networks?
A network larger in geographical scope than a LAN but within a range of less than 30 miles or 50 km
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did you know that there is Often there is a desire to create network links to link locations
that would require running wires through someone else’s property.
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how does MAN works
▪ Requires services from a service provider or public carrier ▪ Begins to resemble a WAN ▪ Edge connection – a connection at an access point on the customer’s premises that connects to a provider
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what is Campus area network (CAN) ?
▪ Network type between a LAN and a MAN ▪ Number of interconnected buildings clustered together
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Metropolitan Area Network
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imageju36qx-14A5D28CBCB4208E85A.png
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what is Wide Area Networks (WAN) ?
▪ Facilitate communications between users and applications over large geographical distances ▪ Distinguishing feature is the extensive reliance on service providers to provide the required connectivity between nodes
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how is the carrier network represented by in WAN?
The carrier network is sometimes represented as a collection of private virtual networks
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Primary reasons for WANs
▪ Organization requires data communication links between widely spread facilities and between an organization and its external contacts ▪ Organization requires fast access to the Internet, either as a consumer or as a provider of Internet services, or both
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what is an example in WAN?
Extranet ▪ A connection between a business and its business partners that usually uses the Internet as a medium for its activities
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Two Real-World WANs
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Wide Area Network Carrier Options
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/image38aerx-14A5D2D8B8D48804881.png
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what does (ISPs) do ?
Internet Service Providers
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traits of the Internet backbone?
▪ High speed fiber optic networks that carry traffic between major cities throughout the world ▪ Speed ranges from 45 to 625 Gbps with faster backbones in the future ▪ Created to speed network traffic that would otherwise require many slow hops to the final destination ▪ No official central backbone and no official guidance for its development
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what does the Network access points do in the backbone ?
Interchanges between the backbones
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DID you know
▪ Local ISPs receive their service from regional ISPs who, in turn, receive their service from national ISPs Most regional ISPs also interconnect among themselves
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Comparison of Internet and Highway Architecture
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imagep16frx-14A5D312EAE3EA6EDA5.png
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what is Piconets also known as >?
Also known as personal area networks (PAN) Created for the personal use of an individual
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what is the pictonets range of?
▪ Generally have ranges of 30 feet or less which is sufficient to permit an individual to interconnect personal computing devices ▪ Connections between different cooperating users are possible but rare
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what is the primary medium for PANs?
Bluetooth
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example of the PANS ?
▪ Example: interconnection between a cell phone, hands-free speaker and car radio
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ISO
(International Standards Organization) ▪ > 17,000 standards including the OSI Reference model
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IEEE
* (Institute for Electrical and Electronics Engineers ▪ Ethernet standards – Ethernet (802.3), Wi-Fi (802.11), Bluetooth (802.15) and WiMax (802.16)
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what does ▪ IETF stands for ?
IETF (Internet Engineering Task Force) ▪ Internet standards based on RFCs (request for comments)
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what does ICANN stand for ?
ICANN ▪ Internet Corporation for Assigned Names and Numbers ▪ IP address allocation, domain name registration, protocol parameter assignment ▪ Management of domain name and root server systems
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what does IANA stands for ?
(Internet Assigned Numbers Authority ▪ Registers application layer port numbers and specific parameter values used in Internet protocol headers
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Numbers can be represented as a combination of
▪ Value or magnitude ▪ Sign (plus or minus) ▪ Decimal (if necessary)
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Value Range: Binary vs. BCD
▪ BCD range of values < conventional binary representation
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Value Range: Binary vs. BCD how ?
▪ Binary: 4 bits can hold 16 different values (0 to 15) ▪ BCD: 4 bits can hold only 10 different values (0 to 9)
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Conventional Binary why prefered ?
▪ Binary representation generally preferred ▪ Greater range of value for given number of bits ▪ Calculations easier
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where BCD is used ?
BCD often used in business applications to maintain decimal rounding and decimal precision
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Simple BCD Multiplication
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/imageh9m7qx-14A62F9928F3EC59B43.png
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how is packed decimal format ?
▪ Real numbers representing dollars and cents ▪ Support by business-oriented languages like COBOL ▪ IBM System 370/390 and Compaq Alpha
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Signed-Integer Representation how ?
▪ No obvious direct way to represent the sign in binary notation
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what options are Signed-Integer Representation ?
Options: ▪ Sign-and-magnitude representation ▪ 1’s complement ▪ 2’s complement (most common)
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Sign-and-Magnitude how ?
▪ Use left-most bit for sign ▪ 0 = plus; 1 = minus ▪ Total range of integers the same ▪ Half of integers positive; half negative ▪ Magnitude of largest integer half as large
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example of the sign and magnitude
▪ Example using 8 bits: ▪ Unsigned: 1111 1111 = +255 ▪ Signed: 0111 1111 = +127 1111 1111 = -127 Note: 2 values for 0: +0 (0000 0000) and -0 (1000 0000)
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Difficult Calculation Algorithms
▪ Sign-and-magnitude algorithms complex and difficult to implement in hardware ▪ Must test for 2 values of 0 ▪ Useful with BCD ▪ Order of signed number and carry/borrow makes a difference ▪ Example: Decimal addition algorithm
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Instruction Set Architectures, what do it do?
ISA ISA determines instruction formats
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– The LMC is a
one-address architecture (an accumulator-based machine).– e.g., the instruction ADD X
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other instructions set and why
There are other instruction set architectures, all based on the number of explicit operands . 0-address (stack) 1-address (accumulator) 2-address 3-addres
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0-Address Machines
– All operands for binary operations are implicit on the stack. Only push/pop reference memory. – e.g., calculating a = a * b + c – d * e
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1-Address Machines
Accumulator is a source and destination. Second source is explicit.
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1-Address Machines
10 memory references, not including instruction fetch
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2-Address Machines
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2-Address Machines
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_246-14A61F45B74229CEDAE.png
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2-Address Machines with registers ?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_247-14A61F50C171EEB8E26.png
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3-Address Machines
– One destination operand, two source operands, all explicit
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3-Address Machines eg without registers ?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_248-14A61F622D5078C6512.png
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3-Address Machines without registers?
https://s3.amazonaws.com/classconnection/655/flashcards/7082655/png/selection_249-14A61F7191F1FB1AE34.png
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6 memory accesses; general purpose registers make a substantial difference.
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Comparison – Assume 8 registers (3 bits), * 32 op-codes (5 bits), 15-bit addresses, * 16-bit integers. – Which ISA accesses memory the least?
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0-address
(stack)
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1-address
(accumulator)
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2-address
(register variant is 11⁄2-address)
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3-address
(with register variant
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The instruction set architecture determines
the format of instructions (and therefore the assembly language).
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Four basic types with variations:?
- 0-address (stack) 2. 1-address (accumulator) 3. 2-address (register variant is 11⁄2-address) 4. 3-address (with register variant
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ISA dramatically affects what ?
the number of times memory is accessed.
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CISC
Complex Instruction Set Computers
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RISC
Reduced Instruction Set Computers
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Motivation for CISC
Early computers had very little and very slow memory. Thus, the fewer instructions fetched, the faster the computer could be.
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General characteristics: CISC
High number of operations (300+) Compilers have less work to do to translate HLL into machine code. Large number of instruction formats Multi-clock cycle instructions Fewer registers; more memory access Large number of transistors, CPU complexity, therefore higher CPU prices
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Motivation for RISC
As memory capacities grew, there was less need for high code density. Also, pushing clock rates higher on CISC hardware was difficult. A simpler processor could be clocked faster
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– General characteristics of RISC
- Lower number of operations (150+) 2. Compilers have more work to do. 3. Small number of instruction formats 4. All instructions take one cycle. 5. Load/store architecture 6. Smaller number of transistors, lower CPU complexity, therefore lower CPU prices
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RISC vs. CISC
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did you know about transistor
– CISC processors require more CPU transistors in an effort to maximize code density in memory
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did you know about the Risc processor
RISC processors use a simpler design in an effort to reduce the number of cycles per instruction
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The only major CISC architecture today is
the Intel x86 and x64. Nearly all else is RISC.
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CPU: Major Components
▪ ALU CU
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ALU
arithmetic logic unit) ▪ Performs calculations and comparisons
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CU
(control unit) ▪ Performs fetch/execute cycle Accesses program instructions and issues commands to the ALU Moves data to and from CPU registers and other hardware components
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Subcomponents: of the CPU
Memory management unit: supervises fetching instructions and data from memory I/O Interface: sometimes combined with memory management unit as Bus Interface Unit
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System Block Diagram
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Concept of Registers
▪ Small, permanent storage locations within the CPU used for a particular purpose ▪ Manipulated directly by the Control Unit ▪ Wired for specific function ▪ Size in bits or bytes (not in MB like memory ▪ Can hold data, an address or an instruction
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▪ How many registers does the LMC have? ▪ What are the registers in the LMC?
two the baskets
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Use of Registers
▪ Scratchpad for currently executing program • Holds data needed quickly or frequently ▪ Stores information about status of CPU and currently executing program * Address of next program instruction * Signals from external devices
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what about General Purpose Registers
User-visible registers Hold intermediate results or data values, e.g., loop counters Equivalent to LMC’s calculator Typically several dozen in current CPUs
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Special-Purpose Registers (PC )
Program Count Register (PC) ▪ Also called instruction pointer
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Special-Purpose Registers (IR)
Instruction Register (IR) ▪ Stores instruction fetched from memory
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Special-Purpose Registers
▪ Memory Address Register (MAR) ▪ Memory Data Register (MDR)
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Status Registers
▪ Status of CPU and currently executing program
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▪ Flags
(one bit Boolean variable) to track condition like arithmetic carry and overflow, power failure, internal computer error
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Register Operations
Stores values from other locations (registers and memory) ▪ Addition and subtraction ▪ Shift or rotate data ▪ Test contents for conditions such as zero or positive
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Operation of Memory
▪ Each memory location has a unique address ▪ Address from an instruction is copied to the MAR which finds the location in memory ▪ CPU determines if it is a store or retrieval ▪ Transfer takes place between the MDR and memory ▪ MDR is a two way register
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Relationship between MAR, MDR and Memory
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MAR-MDR Example
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Visual Analogy of Memory
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Individual Memory Cell
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memory capacity determined by two factors ?
- Number of bits in the MAR LMC = 100 (00 to 99) 2 K where K = width of the register in bits 2. Size of the address portion of the instruction 4 bits allows 16 locations 8 bits allows 256 locations 32 bits allows 4,294,967,296 or 4 GB
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RAM:
Random Access Memory
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what is RAM (Dynamic RAM)?
▪ Most common, cheap, less electrical power, less heat, smaller space ▪ Volatile: must be refreshed (recharged with power) * 1000’s of times each second
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SRAM (static RAM)
▪ Faster and more expensive than DRAM ▪ Volatile ▪ Small amounts are often used in cache memory for high-speed memory access
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Nonvolatile Memory?1
ROM ▪ Read-only Memory ▪ Holds software that is not expected to change over the life of the system