Hi,
Local interfaces are used to reduce the network turnaround time.Consider your scenario where a client interacts with a remote client.
Suppose that the remote client is a session bean which needs to interact with multiple enterprise beans in a single method invocation.
In absence of local interfaces, the communication between the session bean and the other beans would be through remote interfaces.This would increase the response time even in cases where the beans are colocated.
To avoid this local interfaces have been introduced in
EJB 2.0.
Previous to this server providers would make there own optimazations, so that colocated beans would interact locally.In order to standardize this access local interfaces were introduced
Hope this answers your query
Regards,
Paresh Vernekar