SOA Model 1 and 2

Although some EAI architects may take umbrage to this computing analogy, but the difference between an SOA with and without an ESB is analogous to the difference between a hub-and-spoke architecture, often referred to as a message broker, and point-to-point application integration. Basically, Figure 2 depicts a more simplistic point-to-point SOA, while Figure 1 includes an SOA with an ESB.