Algorithm

  When a system/node connects to the ring, it listens for a while. 

  If it hears nothing, a single 3-byte token is generated.
    One node is set up to guard against multiple tokens.
    * It most likely generates the initial token.

  While nodes are linked into token ring,
    The "empty" token is passed from node to node around the ring.

    If a node wants to transmit 
      It converts token to data or command frame consisting of :

        Starting delimiter - unique bit pattern to id start of token.

        Access control - priority field, flags empty or filled token, other.
          Bits 0-2 - priority, 3 - Token type, 4 - monitor, 5-7 - reserved.

        Frame control - type of frame (data or control) and control info.
          0-1 - type of info (control or data)
          2-7 - if control, control code.          

        DA - Destination Address (Media access control, MAC - hardware address)
        SA - Source Address. (SA and DA are 6 bytes)
        * If you are communicating with a system outside the local network
           then the IP number of the destination is carried in the data 
           portion of the frame.

        Data frame up to 4500 bytes of data.

        Frame Check Sequence - CRC error check. 

        Ending delimiter - End of main frame. Complement to Starting delimiter.

        FS - frame control. Sender sets bit, when appropriate receiver sees 
          packet, it clears bit and packet continues back around to sender.

      Once sender sees the frame has returned, 
        it "removes" the data thus re-creating the default "empty" token 
        or it sends the next frame of data. 

        The token/frame must return to the original sender before being 
        available for the next packet in current node's communication session 
        or to be handed to the next station desiring to transmit.
        
        Generally, a node will desire to send several packets that make up 
          a 'session'. 
   
      Optional 
        Other stations may request next access to token. 
        And stations can be assigned priority.

        For example : the administrator may want to grant a server node a longer
          token access time or higher priority.

  Abort Frame - special purpose frame generated by sender to abort session.