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

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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 ControlAvoids the problem of a host at one side of the connection overflowing the buffers in the host at the other sideEnsures the integrity of the data

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Session EstablishmentOne 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 TerminationCongestion can occur during data transfer

1- A high speed computer might generate traffic faster than a network can transfer

2- If many computers simultaneously send datagrams to single destination, that destination can experience congestion, although no single source caused a problemTo 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 endInformation 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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UDPThe 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 TCP/IP Application Layer

Identifying and establishing the availability of intended communication partners Synchronizing cooperating applications Establishing agreement on procedures for error recovery Controlling data integrityPresentation, encoding and dialog control

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Application Layer Examples

Domain Name SystemFile Transfer Protocol Hypertext Transfer Protocol Simple Mail Transport ProtocolSimple Network Management ProtocolTelnet

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DNSThe 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 TFTPFTP 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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SMTPE-mail servers communicate with each other using the Simple Mail Transport Protocol (SMTP) to send and receive mail.

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TelnetTelnet 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.

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Telnet uses TCP thence is connection

oriented.