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> Zone
> Zones restrict the behavior of routes, so you can configure complex routing paths. Zones affect topic messages, but not queue messages.
> Basic Operation
> A zone is a named set of routes. Every route belongs to a zone. A zone affects the forwarding behavior of its routes:

> • | In a multi-hop (mhop) zone, topic messages travel along all applicable routes to all servers connected by routes within the zone.

> • | In a one-hop (1hop) zone, topic messages travel only one hop (from the first server).

> • | Queue messages travel only one hop, even within multi-hop zones.

> For example, Figure 34 depicts a set of servers connected by routes within a multi-hop zone, Z1. If a client sends a message to a global topic on server B, the servers forward the message to A, C, D and E (assuming there are subscribers at each of those servers). In contrast, if Z1 were a one-hop zone, B would forward the message to A, C and D—but D would not forward it E.
> Figure 34 Zones: multi-hop
> Eliminating Redundant Paths with a One-Hop Zone
> Figure 35 illustrates an enterprise with four servers:

> • | B1 and B2 serve producers at branch offices of an enterprise.

> • | M serves consumers at the main office, which process the messages from the branches.

> • | R serves consumers that record messages for archiving, auditing, and backup.

> The goal is to forward messages from B1 and B2 to both M and R. The routing graph seems to contain a cycle—the path from B1 to M to B2 to R duplicates the route from B1 to R. However, since these routes belong to the one-hop zone Z2, it is impossible for messages to travel the longer path. Instead, this limitation results in the desired result—forwarding from B1 to M and R, and from B2 to M and R.
> Figure 35 Zones: one-hop
> 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.
> Figure 36 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.
> Figure 36 Zones: overlap

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