1. Framing mechanism. Recall that "frame" is the terminology used to describe a Protocol Data Unit (PDU) at the Data-Link layer.
   1. [5 marks] What framing technique does HDLC use? (please see the MAC sublayer lecture materials)
   2. [5 marks] Create a simple diagram of the structure of a frame for HDLC that includes the name, size, and position of all fields.
   3. [5 marks] Provide a description of the purpose of each field in the frame.