Page 126 - Handout Computer Network.

CHAPTER 6

TRANSPORT AND APPLICATION LAYERS PROTOCOLS

6.1 TCP/IP Transport and Application Layer

The transport layer uses the services provided by the network layer, such as best-path
selection and logical addressing, to provide end-to-end communication between source and
destination. This chapter describes how the transport layer regulates the flow of information
from source to destination reliably and accurately.

The primary characteristics of the transport layer are discussed, including the following:

• The transport layer data stream is a logical connection between the endpoints of
a network.

• End-to-end control and reliability are provided by sliding windows, sequencing
numbers, and acknowledgments.

• Layer 4 protocols TCP and UDP use port numbers to keep track of different
conversations that cross the network at the same time, and to pass information
to the upper layers.
The primary characteristics of the TCP/IP application layer include the following:

• End-user applications reside at this layer.

• Commonly used applications include NFS, DNS, ARP, rlogin, talk, FTP, NTP, and
traceroute.

https://www.youtube.com/watch?v=bQ6woul_JrQ

6.2 Understanding the TCP/IP Transport Layer

The phrase “quality of service” often is used to describe the purpose of Layer 4, the
transport layer. UDP, which is covered later, also operates at Layer 4 and provides
connectionless transport services.

146