With DECnet Phase V, DEC nodes become equal participants in OSI networks. DECnet Phase V also supports much larger networks than previous DECnet phases. DECnet Phase V's network layer is equivalent to CLNS, which is described in Cisco's OSI Routing Protocol Brief. The difference between them is that while both end nodes and routing nodes can send and receive network information, only routing nodes can provide routing services for other DECnet nodes. Instead, DECnet locates hosts using area and node address pairs.
Areas can span many routers, and a single cable can support many areas.
Figure 2 shows a sample DECnet network with several addressable entities. A Level 1 router communicates with end nodes and with other Level 1 routers in a particular area. Level 2 routers communicate with Level 1 routers in the same area and with Level 2 routers in different areas. Together, Level 1 and Level 2 routers form a hierarchical routing scheme. This relationship is illustrated in Figure 3.