Engineers working on Project X form a cluster, those working on Project Y form a cluster, and those working on Project Z form a cluster. Everyone knows everyone else within the local cluster, and yet only a few individuals have boundary spanning ties to other clusters. Strong, frequent, ties are usually found within clusters, while weaker, less frequent ties are found between clusters. Clusters of concentrated connections appear throughout an organization and throughout industries.
Some clusters have many ties to many others, while other clusters have only a few ties.
Poor connections between clusters result in very long path lengths throughout the greater network. In such a network it is easy to access those in your cluster but not those in other clusters. This often results in distant clusters not having access to information and knowledge that is available in the organization. Often the knowledge you need is in clusters other than your own. Networks have a horizon beyond which it is difficult to see what is happening.