Video presentation: "Transport layer: Multiplexing and demultiplexing." What are multiplexing and demultiplexing? How is it done? How does it work in TCP and UDP?

Computer networks class.
Jim Kurose
Textbook reading: Section 3.2, Computer Networking: a TopDown Approach (8th edition), J.F. Kurose, K.W. Ross, Pearson, 2020.
See http://gaia.cs.umass.edu/kurose_ross for more open student resources.