What is a frame?

Hello mates,
A frame is a n-bit structure having data in it along with the control and management information. The term 'frame' is used in SDH, SONET and PDH. In simple terms, a frame is a data unit.

Why frame?
For transmission of data, we need some control information of how data is organised and how management is done. Depending on the capability of the device, the amount of data which can be transferred varies. Like, PDH frames have lesser data rate and it carries lesser data in comparison with SDH.

This is what the frame is and why it id needed.

I am happy to listen to the suggestions, doubts and ideas.