Figure 1 is an animation used to demonstrate the rules used in communication.  The figure shows an envelope that has a recipient address and a return address on it.  These represent the location address of the recipient and the location address of the sender of the message.  The letter inside represents the message being sent.   The greeting such as “Dear” on the message aligns with the start of message indicator.  The name following Dear such as “Jane” represents the identity of the recipient.  The contents of the letter represent the encapsulated data and the signing of the letter is the source identifier.  The stamp represents transmitting the message. Figure 2 shows the format and contents of a frame.  This encapsulation has the frame addressing on one end and the frame indicator on the other end with the message in between.