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Building a Simple Network

Understanding theHost-to-HostCommunications Model

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Understanding Host-to-HostCommunications

Older model

o Proprietary

o Application and combinations software controlled by one

vendor Standards-based model

o Multivendor software

o Layered approach

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Why a Layered Network Model?

Reduces complexity Standardizes interfaces Facilitates modular engineering Ensures interoperable

technology Accelerates evolution Simplifies teaching and learning

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The Seven Layers of the OSI Model

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The Seven Layers of the OSI Model (Cont.)

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The Seven Layers of the OSI Model (Cont.)

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The Seven Layers of the OSI Model (Cont.)

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The Seven Layers of the OSI Model (Cont.)

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The Seven Layers of the OSI Model (Cont.)

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The Seven Layers of the OSI Model (Cont.)

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Data Encapsulation

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Data De-Encapsulation

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Peer-to-Peer Communication

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Defines four layers

Uses different names for Layers 1through 3

Combines Layers 5 through 7 intosingle application layer

TCP/IP Stack

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Transport Layer

Session multiplexing Segmentation Flow control (when required) Connection-oriented

(when required)

Reliability (when required)

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Reliable vs. Best-Effort Comparison

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UDP Characteristics

Operates at transport layer of OSI and TCP/IP models Provides applications with access to the network layer without the

overhead of reliability mechanisms

Is a connectionless protocol Provides limited error checking Provides best-effort delivery Has no data-recovery features

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UDP Header

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TCP Characteristics

Transport layer of the TCP/IP stack Access to the network layer for applications Connection-oriented protocol

Full-duplex mode operation Error checking Sequencing of data packets Acknowledgement of receipt Data-recovery features

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TCP Header

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TCP/IP Application Layer Overview File transfer

o FTPo TFTPo Network File

System E-mail

o Simple MailTransfer Protocol

Remote logino Telneto rlogin

Network managemento Simple Network

ManagementProtocol

Name management

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Mapping Layer 3 to Layer 4

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Mapping Layer 4 to Applications

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Establishing a Connection

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Three-Way Handshake

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Flow Control

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TCP Acknowledgment

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Fixed Windowing

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TCP Sliding Windowing

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TCP Sequence and Acknowledgment Numbers