1 © 2003, Cisco Systems, Inc. All rights reserved. CCNA 1 v3.0 Module 11 TCP/IP Transport and Application Layers

222 © 2003, Cisco Systems, Inc. All rights reserved. Objectives TCP/IP Transport Layer TCP/IP Application Layer

3 © 2003, Cisco Systems, Inc. All rights reserved. TCP/IP Transport Layer

444 © 2003, Cisco Systems, Inc. All rights reserved. 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

555 © 2003, Cisco Systems, Inc. All rights reserved. Reliability

666 © 2003, Cisco Systems, Inc. All rights reserved. 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

777 © 2003, Cisco Systems, Inc. All rights reserved. Session Establishment One function of the transport layer is to establish a connection- oriented session between similar devices at the application layer.

888 © 2003, Cisco Systems, Inc. All rights reserved. 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.

999 © 2003, Cisco Systems, Inc. All rights reserved. Three-Way Handshake

10 © 2003, Cisco Systems, Inc. All rights reserved. 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

11 © 2003, Cisco Systems, Inc. All rights reserved. Window Size TCP window sizes are variable during the lifetime of a connection. Larger window sizes increase communication efficiency.

12 © 2003, Cisco Systems, Inc. All rights reserved. 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.

13 © 2003, Cisco Systems, Inc. All rights reserved. TCP Sequence and Acknowledgment

14 © 2003, Cisco Systems, Inc. All rights reserved. Transmission Control Protocol (TCP) The protocols that use TCP include: FTP (File Transfer Protocol) HTTP (Hypertext Transfer Protocol) SMTP (Simple Mail Transfer Protocol) Telnet

15 © 2003, Cisco Systems, Inc. All rights reserved. TCP Segment Format

16 © 2003, Cisco Systems, Inc. All rights reserved. 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)

17 © 2003, Cisco Systems, Inc. All rights reserved. UDP Segment Format

18 © 2003, Cisco Systems, Inc. All rights reserved. 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.

19 © 2003, Cisco Systems, Inc. All rights reserved. TCP and UDP Port Numbers

20 © 2003, Cisco Systems, Inc. All rights reserved. TCP/IP Application Layer

21 © 2003, Cisco Systems, Inc. All rights reserved. Introduction to Application Layer

22 © 2003, Cisco Systems, Inc. All rights reserved. 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

23 © 2003, Cisco Systems, Inc. All rights reserved. Application Layer Examples Domain Name System File Transfer Protocol Hypertext Transfer Protocol Simple Mail Transport Protocol Simple Network Management Protocol Telnet

24 © 2003, Cisco Systems, Inc. All rights reserved. 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

25 © 2003, Cisco Systems, Inc. All rights reserved. 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.

26 © 2003, Cisco Systems, Inc. All rights reserved. HTTP

27 © 2003, Cisco Systems, Inc. All rights reserved. SMTP servers communicate with each other using the Simple Mail Transport Protocol (SMTP) to send and receive mail.

28 © 2003, Cisco Systems, Inc. All rights reserved. SNMP The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices.

29 © 2003, Cisco Systems, Inc. All rights reserved. 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.