Making Things Talk

82 MAKING THINGS TALK

Network Maps and Addresses

In the last chapter, it was easy to keep track of where messages went, because there

were only two points in the network you built: the sender and the receiver. In any

network with more than two objects, from three to three billion, you need a map

to keep track of which objects are connected to which, and an addressing scheme

to know how a message gets to its destination.

Network Maps: How

Things Are Connected

The arrangement of physical connections on a network

depends on how you want to route the messages on that

network. The simplest way is to make a physical connec-

tion from each object in the network to every other object.

That way, messages can get sent directly from one point

to another. The problem with this approach, as you can

see from the directly connected network in Figure 3-1, is

that the number of connections gets large very fast, and

the connections get tangled. A simpler alternative to this

is to put a central controller in the middle, and pass all

messages through this hub, as seen in the star network.

This way works great as long as the hub continues to

function, but the more objects you add, the faster the hub

has to be to process all the messages. A third alternative is

to daisy-chain the objects, connecting them together in a

ring. This design makes for a small number of connections,

and it means that any mes