CIM 2465 TCP/IP Transport and Application Layers1 TCP/IP Transport and Application (Topic 6)...

CIM 2465 TCP/IP Transport and Application Layers 1

TCP/IP Transport and Application(Topic 6)

Textbook:

Networking Basics, CCNA 1 Companion Guide, Cisco Press

Cisco Networking Academy Program, CCNA 1 and 2, Companion Guide, Cisco Press, Latest Edition


TCP/IP Transport Layer (1)

• Main goal of the Transport Layer– To provide the service of taking data from one application

process on one computer and delivering that data to the correct application process on another computer

– Compare with the Internet layer, it delivers data packets from one computer to another, but it does not think about which application sent the data or which application on the receiving computer needs the data

• Key protocols– Transmission Control Protocol (TCP)– User Datagram Protocol (UDP)

• TCP provides several more functions, but more overhead


TCP Vs UDP


Flow Control

• When a host sends data using TCP, the receiving host can control how fast each TCP sender sends the data over time. This process is called flow control.

• Why needed?– Receiver needs time to process the received data– Receiver might have a finite amount of memory for

processing of data

• TCP has flow-control mechanism


Connection-Oriented Vs Conncetionless

• Connectionless– The sender and receiver do not pre-arrange for

communication to occur

• Connection-oriented– The sender and receiver must pre-arrange for

communication to occur (use messages, events, or other prearranged settings)

• TCP is a connection-oriented protocol, uses a process called a three-way handshake


Three-Way TCP Connection


Error Recovery (Reliability)

• Reliable protocols perform error recovery, which means that they ensure that all the data eventually gets to the receiver– No data loss– No data duplicated– Data received in correct sequence (in order

delivery)

• TCP is a reliable protocol, through the use of Acknowledgements


TCP Acknowledgements


Segmentation, Reassembly, and In-Order Delivery

• TCP segmentation refers to the process of TCP accepting a large chunk of data from application protocol and breaking it into pieces that are small enough to be appropriate for transmission

• TCP on the receiving end reassembles the data into its original form, and guarantees that the data will be in order

• Through the use of a Sequence Number


Port Numbers

• One function performed by both UDP and TCP is providing a means to identify the specific application processes that send and receive data

• Through the use of Port Numbers– < 1024, reserved, Well-Known ports– 1024 - 65535, dynamic port numbers


• An IP packet with TCP segment arrives at Keith’s Computer

• TCP examines the destination port number• Based on the port number, the TCP software gives the

data to Browser2


Well-Know Ports (1)


Well-Know Ports (2)


TCP Header Fields

• Key Fields– Source Port– Destination Port– Sequence Number– Acknowledgement Number– Checksum


TCP Header Fields


UDP Header Fields

• Key Fields– Source Port– Destination Port– Length– Checksum


TCP/IP Application Layer

• TCP/IP application layer performs the same functions as defined in the top three layers of the OSI reference model

• TCP/IP application protocols define the format of the data being transferred (binary or ASCII), required encryption, protocol rules for transferring data, combinations of messages (dialogues or sessions)

• Application software (e.g. browsers) typically implements application layer protocols


Application Protocol Examples (1)

• Domain Name System (DNS)– Resolves names into IP addresses– UDP

• Hypertext Transfer Protocol (HTTP)– Transfers files from web servers to web browsers– TCP

• Simple Mail Transfer Protocol (SMTP) and Post Office Protocol version 3 (POP3)– Send and receive e-mail, respectively– TCP

• File Transfer Protocol (FTP)– Stores and retrieves files– TCP


Application Protocol Examples (2)

• Trivial File Transfer Protocol (TFTP)– Works similarly to FTP, but with some benefits when used on

networking devices– UDP

• Simple Network Management Protocol (SNMP)– Allows management software (the client) to query networking

devices (the servers) to manage and control the networking devices

– UDP• Telnet

– Allows a client to emulate a terminal. It allows a user to sit at one computer (Telnet client) and use a remote computer (Telnet server) through a text-based interface

– TCP


DNS


HTTP


SMTP and POP3


FTP

CIM 2465 TCP/IP Transport and Application Layers1 TCP/IP Transport and Application (Topic 6)...

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