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CCNA 1 v3.0 Module 11 TCP/IP Transport and

Application Layers

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Objectives

• TCP/IP Transport Layer

• TCP/IP Application Layer

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TCP/IP Transport Layer

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Introduction to Transport Layer

• Five basic services:

Segmenting upper-layer application data

Establishing end-to-end operations

Transporting segments from one end host to another end host

Ensuring data reliability

Providing flow control

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Reliability

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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

• One function of the transport layer is to establish a connection-oriented session between similar devices at the application layer.

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Session Maintenance and Termination

• Congestion can occur during data transfer

• To terminate, the sending host sends a signal that indicates the end of the transmission, which is acknowledged by the receiver.

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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

• TCP window sizes are variable during the lifetime of a connection.

• 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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TCP Sequence and Acknowledgment

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Transmission Control Protocol (TCP)

• The protocols that use TCP include:

FTP (File Transfer Protocol)

HTTP (Hypertext Transfer Protocol)

SMTP (Simple Mail Transfer Protocol)

Telnet

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TCP Segment Format

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UDP

• The protocols that use UDP include:

TFTP (Trivial File Transfer Protocol)

SNMP (Simple Network Management Protocol)

DHCP (Dynamic Host Control Protocol)

DNS (Domain Name System)

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UDP Segment Format

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TCP and UDP Port Numbers

• Both TCP and UDP use port (socket) numbers to pass information to the upper layers.

Numbers below 1024 are considered well-known ports numbers.

Numbers above 1024 are dynamically assigned ports numbers.

Registered port numbers are those registered for vendor-specific applications. Most of these are above 1024.

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TCP and UDP Port Numbers

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TCP/IP Application Layer

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Introduction to Application Layer

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Responsibilities of Application Layer

• 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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DNS

• The Domain Name System (DNS) is a system used for translating names of domains into IP addresses.

• There are more than 200 top-level domains on the Internet, examples of which include the following:

.us – United States

.uk – United Kingdom

.edu – educational sites

.com – commercial sites

.gov – government sites

.org – non-profit sites

.net – network service

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FTP and TFTP

• FTP is a reliable, connection-oriented service that uses TCP to transfer files between systems that support FTP.

• TFTP is a connectionless service that uses User Datagram Protocol (UDP).

TFTP is used on routers to transfer configuration files and Cisco IOS images.

TFTP is designed to be small and easy to implement.

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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.

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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.