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www.ciscopress.comCopyright 2003
CCNA 1 Chapter 9
TCP/IP Transport and Application Layers
By
Your Name
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Objectives
• TCP/IP transport layer
• TCP/IP application layer
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Routed Protocols Versus Routing Protocols
Routing protocols determine the path that routed protocols follow to their destinations.
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The Transport Layer Functions
Five basic services:• Segmenting upper-layer application data• Establishing end-to-end operations• Sending segments from one end host to another
end host• Ensuring data reliability• Providing flow control
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Flow Control
• Avoids the problem of a host at one side of the connection overflowing the buffers in the host at the other side
• Ensures the integrity of the data
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Session Establishment
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Three-Way Handshake
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Windowing
• A method of controlling the amount of information transferred end to end
• Information can be measured in terms of the number of packets or the number of bytes
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Window Size
Larger window sizes increase communication efficiency.
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Acknowledgment
• Positive acknowledgment requires a recipient to communicate with the source, sending back an acknowledgment message when it receives data.
• Sender keeps a record of each data packet that it sends and expects an acknowledgment.
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Layer 4 Protocols
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TCP
• Connection oriented • Reliable • Divides outgoing messages into segments • Reassembles messages at the destination
station • Resends anything not received • Reassembles messages from incoming
segments
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UDP
• Connectionless • Unreliable • Transmits messages (called user datagrams) • Provides no software checking for message
delivery (unreliable) • Does not reassemble incoming messages • Uses no acknowledgments • Provides no flow control
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TCP/IP Protocol Graph
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TCP Segment Format
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UDP Segment Format
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Port Numbers
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Application Layer
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TCP/IP Application Layer
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Responsibilities
• Identifying and establishing the availability of intended communication partners
• Synchronizing cooperating applications • Establishing agreement on procedures for error
recovery • Controlling data integrity
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Application Layer Examples
• Domain Name System• File Transfer Protocol • Hypertext Transfer Protocol • Simple Mail Transport Protocol• Simple Network Management Protocol• Telnet
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Domain Name System
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FTP
• FTP is a reliable, connection-oriented service that uses TCP to transfer files between systems that support FTP.
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HTTP
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SMTP
• E-mail servers communicate with each other using the Simple Mail Transport Protocol (SMTP) to send and receive mail.
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SNMP
• The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices.
• An SNMP managed network consists of the following: – Network management
system (NMS) – Managed device– Agents
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Telnet
• Telnet client software provides the ability to log in to a remote Internet host that is running a Telnet server application and then to execute commands from the command line.