TCP/UDP vs Circut/Packet Switching confusion

Question

My silly brain is unable to understand the difference between OSI's Transport Layer TCP/UDP and the Circuit/Packet Switching.

Firstly, I am failing to understand which layer should Circuit/Packet Switching be referring to? As it concerns the way the data is being sent (i.e.the "broken down" pieces of information via either different/same routes and orders to destination), isn't it also the Transport Layer?

Also, as TCP/UDP are equally relating to the way data is being sent, I do not know what exactly am I referring to when I'm talking about circuit/packet switching or TCP/UDP anymore. How do these differ? Can anyone try to explain to me the basic difference?

I'm very sorry for my silly brain.

Answer 1

TCP and UDP are in Layer 4 of the OSI Model. This layer is the application interface to networking. TCP and UDP package the data which an application sends, and unpackages the data which an application receives. The application data are encapsulated in TCP segments or UDP datagrams, or any other layer-4 protocol the application uses.

Packet switching is in Layer 3 of the OSI Model. This is the layer where routing happens. The layer-4 segments are encapsulated in IP packets.

Frame switching is in Layer 2 of the OSI Model. This is the layer used by switches and bridges. The layer-3 packets are encapsulated in layer-2 (e.g. ethernet) frames.