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

CCNA 1 v3.0 Module 11 TCP/IP Transport and Application Layers. Objectives. TCP/IP Transport Layer TCP/IP Application Layer. TCP/IP Transport Layer. Introduction to Transport Layer. Five basic services : Segmenting upper-layer application data Establishing end-to-end operations

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

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

  2. Objectives • TCP/IP Transport Layer • TCP/IP Application Layer

  3. TCP/IP Transport Layer

  4. 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

  5. Reliability • Reliable transport can accomplish the following: • Ensure the segments delivered will be acknowledged to the sender • Provide for retransmission of any segments that are not acknowledged • Put segments back into their correct sequence at the destination • Provide congestion avoidance and control

  6. 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

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

  8. 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.

  9. Three-Way Handshake

  10. Windowing • The number of data packets the sender is allowed to have outstanding without having received an acknowledgment is known as the window size, or window. • 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. Synchronisation • Hosts use segments called SYNs for synchronisation. SYNs carry a control bit also called SYN and the Initial Sequence Number (ISN) • The synchronization requires each side to send its own ISN and to receive a confirmation of exchange in an acknowledgment (ACK) from the other side. • Each side must also receive the ISN from the other side and send a confirming ACK.

  12. The sequence is as follows: • A→B SYN—(A) initial sequence number is X, ACK number is 0, SYN bit is set, but ACK bit is not set. • B→A ACK—(A) sequence number is X + 1, (B) initial sequence number is Y, and SYN and ACK bit are set. • A→B ACK—(B) sequence number is Y + 1, (A) sequence number is X + 1, the ACK bit is set, but the SYN bit is not set.

  13. Window Size • TCP window sizes are variable during the lifetime of a connection. • Larger window sizes increase communication efficiency.

  14. 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.

  15. TCP Sequence and Acknowledgment

  16. Transmission Control Protocol (TCP) • The protocols that use TCP include: • FTP (File Transfer Protocol) • HTTP (Hypertext Transfer Protocol) • SMTP (Simple Mail Transfer Protocol) • Telnet

  17. TCP Segment Format

  18. The following are the definitions of the fields in the TCP segment: • Source port – Number of the calling port • Destination port – Number of the called port • Sequence number – Number used to ensure correct sequencing of the arriving data • Acknowledgment number – Next expected TCP octet • HLEN – Number of 32-bit words in the header • Reserved – Set to zero

  19. fields in the TCP segment (cont) • Code bits – Control functions, such as setup and termination of a session • Window – Number of octets that the sender is willing to accept • Checksum – Calculated checksum of the header and data fields • Urgent pointer – Indicates the end of the urgent data • Option – One option currently defined, maximum TCP segment size • Data – Upper-layer protocol data

  20. 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)

  21. UDP Segment Format

  22. The following are the definitions of the fields in the UDP segment: • Source port – Number of the calling port • Destination port – Number of the called port • Length – Number of bytes including header and data • Checksum – Calculated checksum of the header and data fields • Data – Upper-layer protocol data

  23. 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.

  24. TCP and UDP Port Numbers

  25. Port Numbers

  26. TCP/IP Application Layer

  27. Introduction to Application Layer

  28. 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

  29. Application Layer Examples • Domain Name System • File Transfer Protocol • Hypertext Transfer Protocol • Simple Mail Transport Protocol • Simple Network Management Protocol • Telnet

  30. 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

  31. 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.

  32. HTTP

  33. SMTP • E-mail servers communicate with each other using the Simple Mail Transport Protocol (SMTP) to send and receive mail.

  34. SNMP • The Simple Network Management Protocol (SNMP)is an application layer protocol that facilitates the exchange of management information between network devices.

  35. Telnet • Telnet client software provides the ability to login to a remote Internet host that is running a Telnet server application and then to execute commands from the command line.

  36. Summary • The functions of the TCP/IP transport layer • Flow control • The processes of establishing a connection between peer systems • Windowing • Acknowledgment • Transport layer protocols • TCP and UDP header formats • TCP and UDP port numbers • The processes and protocols at the TCP/IP application layer • Domain Name Services • File Transfer Protocols • Simple Mail Transfer Protocol • Simple Network Management Protocol • Telnet

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