Quiz1 Review

Quiz1 Review - Key Elements of a Protocol Syntax Data...

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Key Elements of a Protocol Syntax Data formats Signal levels Semantics Control information Error handling Timing Speed matching Sequencing
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Protocol Architectures and Networks
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Addressing Requirements Two levels of addressing required Each computer needs unique network address Each application on a (multi-tasking) computer needs a unique address within the computer The service access point or SAP The port on TCP/IP stacks
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Protocol Data Units (PDU) At each layer, protocols are used to communicate Control information is added to user data at each layer Transport layer may fragment user data Each fragment has a transport header added Destination SAP Sequence number Error detection code
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Protocol Data Units
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Operation of a Protocol Architecture
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Standardized Protocol Architectures Required for devices to communicate Vendors have more marketable products Customers can insist on standards based equipment Two standards: OSI Reference model Never lived up to early promises TCP/IP protocol suite Most widely used Also: IBM Systems Network Architecture
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Characteristics Direct or indirect Monolithic or structured Symmetric or asymmetric Standard or non-standard
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Direct or Indirect Direct Systems share a point to point link or Systems share a multi-point link Data can pass without intervening active agent Indirect Switched networks or Internetworks or internets Data transfer depend on other entities
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Functions Encapsulation Segmentation and reassembly Connection control Ordered delivery Flow control Error control Addressing Multiplexing Transmission services
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Encapsulation Addition of control information to data Address information Error-detecting code Protocol control
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Segmentation (Fragmentation) Data blocks are of bounded size Application layer messages may be large Network packets may be smaller Splitting larger blocks into smaller ones is segmentation (or fragmentation in TCP/IP) ATM blocks (cells) are 53 octets long Ethernet blocks (frames) are up to 1526 octets long Checkpoints and restart/recovery
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Why Fragment? Advantages More efficient error control More equitable access to network facilities Shorter delays Smaller buffers needed Disadvantages Overheads Increased interrupts at receiver More processing time
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Flow Control Done by receiving entity Limit amount or rate of data Stop and wait Credit systems Sliding window Needed at application as well as network layers
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Guard against loss or damage Error detection Sender inserts error detecting bits Receiver checks these bits If OK, acknowledge If error, discard packet Retransmission If no acknowledge in given time, re-transmit Performed at various levels
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This note was uploaded on 02/10/2012 for the course CSC 411 taught by Professor Simmons during the Spring '08 term at S. Alabama.

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Quiz1 Review - Key Elements of a Protocol Syntax Data...

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