Overlapping Zones
A server can have routes that belong to several zones. When zones overlap at a server, the routing behavior within each zone does not limit routing in other zones. That is, when a forwarded message reaches a server with routes in several zones, the message crosses zone boundaries, and its hop count is reset to zero.
The following image illustrates an enterprise with one-hop zones connecting all the servers in each of several cities in a fully-connected graph. Zone TK connects all the servers in Tokyo; zone NY connects all the servers in New York; zone PA connects all the servers in Paris. In addition, the multi-hop zone WO connects one server in each city.
When a client of server TK3 produces a message, it travels one hop to each of the other Tokyo servers. When the message reaches TK1, it crosses into zone WO. TK1 forwards the message to NY1, which in turn forwards it to PA1. When the message reaches NY1, it crosses into zone NY (with hop count reset to zero); NY1 forwards it one hop to each of the other New York servers. Similarly, when the message reaches PA1, it crosses into zone PA (with hop count reset to zero); PA1 forwards it one hop to each of the other Paris servers.
