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.
Activity 1 Think about
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 2 Test yourself
Using the following two lists, match each numbered item with the correct letter.
a.Which layer of the OSI model do routers operate at?
b.Which layer of the OSI model do switches operate at?
c.Which layer of the TCP/IP protocol suite do routers operate at?
d.Which layer of the TCP/IP protocol suite do switches operate at?
- 1 = d
- 2 = b
- 3 = c
- 4 = a
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.