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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.