Overview

Introduction

The Understand Network Communications and Protocols module provides you with the instruction and computer hardware to develop your hands on skills in the defined topics. This module includes the following exercises:

  • Verifying Port 80 for HTTP
  • Verifying Port 443 for HTTPS
  • Verify Port 139 for NetBIOS
  • Understanding TCP and UDP

Exercise 1 - Verifying Port 80 for HTTP

Hypertext Transfer Protocol (HTTP) is application level protocol in TCP/IP that enables users of the World Wide Web to exchange data. HTTP supports a wide variety of data formats - from text to voice to all way through to multi-media. HTTP servers typically listen on TCP port 80 for any session requests from HTTP clients.

Exercise 2 - Verifying Port 443 for HTTPS

Hypertext Transfer Protocol Secure (HTTPS) is HTTP with Secure Sockets Layer/Transport Layer Security (SSL/TLS) added for security. Web pages with SSL enabled use a computer certificate issued by a Certification Authority. The security feature encrypts communication between the devices and prevent unauthorized access of information available on a public network like the Internet. HTTPS reserves port #443 to receive incoming connections from clients.

Exercise 3 - Verifying Port 139 for NetBIOS

NetBIOS, short for Network Basic Input/Output System, is a communication protocol that supports communication among computers connected on LAN. NetBIOS does not support communication on WANs. Therefore, NetBIOS normally rides on TCP/IP when implemented on applications/computers connected to a WAN. Port #139 is reserved for NetBIOS protocol.

Exercise 4 - Contrast TCP and UDP Protocols

Both TCP (transmission control protocol) and UDP (user datagram protocol) are transport layer protocols responsible for establishing a connection between a client and a server. TCP is a connection-oriented protocol where data is transmitted in large chunks and guarantees their delivery with the use of checksums. While UDP is a connection-less oriented protocol where data is sent in smaller chunks and does not guarantee their delivery to destination node. Both these protocols convert data into packets to enable exchange across networked computers. However, the two are very dissimilar in their details of operation; and hence have very different application.

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