Even if the DSB already extends the Petals ESB, you can use it and extend it to add some specific features. Extending means that you may want to add some custom core services to the Service Bus. For example, add a transport layer, use your own registry implementation, expose a service as Web service, invoke operations on DSB lifecycle... The goal of this part is to show that extending the DSB is (quite) easy. In fact it should be easier to extend the DSB than the Petals ESB.