This document discusses different types of communication networks. It describes internal communication that occurs within an organization between roles like teachers and students. External communication links an organization to outside entities, like communication between heads of two organizations. Vertical communication flows up and down an organizational hierarchy, including downward communication from managers to subordinates and upward communication from subordinates to managers. Diagonal communication moves across levels in a mixture of vertical and horizontal directions. Horizontal communication occurs between individuals of equal rank laterally across departments.