Skip to content
Skip to main content

About this free course

Download this course

Share this free course

Discovering computer networks: hands on in the Open Networking Lab
Discovering computer networks: hands on in the Open Networking Lab

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

11.1 Data transmission

Modern communication systems are the result of a gradual evolution from earlier systems, each bringing its own legacy of diverse technologies and infrastructure that need to be integrated for effective transition. An important task is to ensure that the content of messages is not compromised during the process, and this has led to the development of protocols whose role is to ensure that the message can be conveyed by various networking technologies in a way that is independent of message content. This has led to the development of protocols that work for almost any of the standard data transmission media and almost any kind of content, whether text, audio, video or whatever.

In this section you will revisit some of the concepts of data transmission introduced earlier in this course, keeping an eye on the historical journey that brings us to where we are.

Watch the video below (which is about 5 minutes long). This video considers the influence of the historical development of data transmission on the technologies used today.

Box _unit7.1.1 Data transmission

Download this video clip.Video player: 63_data_transmission.mp4
Copy this transcript to the clipboard
Print this transcript
Show transcript|Hide transcript
Interactive feature not available in single page view (see it in standard view).

Activity _unit7.1.1 Activity 1 Think about

5 minutes

Write two or three sentences to briefly explain the process of encapsulation of data units and why it is needed.


Here’s one possible answer.

During transmission, a message is likely to be carried over a variety of communication networks using different methods and processes. Encapsulation of data units is the process of successively adding delivery information relevant to the protocol being used at a particular point in the journey.

Activity _unit7.1.2 Activity 2 Test yourself

5 minutes


Using the following two lists, match each numbered item with the correct letter.

  1. Network Access

  2. Data Link

  3. Internet

  4. Network

  • a.Which layer of the TCP/IP protocol suite do switches operate at?

  • b.Which layer of the TCP/IP protocol suite do routers operate at?

  • c.Which layer of the OSI model do routers operate at?

  • d.Which layer of the OSI model do switches operate at?

The correct answers are:
  • 1 = a
  • 2 = d
  • 3 = b
  • 4 = c


Without a router in a local network, it is not possible for two network devices to ping each other.


OSI stands for Organised System Information.


Encapsulation is the process of adding protocol information to a data unit.


Both the OSI model and the TCP/IP protocol suite have a layer called ‘Application’.

The correct answers are c and d.