Weblogic's implementationof the RMI specification uses a
proprietary wire-protocol known as T3. javasoft's reference
implementation of RMI uses a proprietary protocol callrd
JRMP. weblogic developed T3 because they needed a
scalable,efficient protocol for building enterprise-class
destributed object systems with java.

T3 provides a framework for WebLogic Server messages that 
support for enhancements. These enhancements include 
abbreviations and features, such as object replacement, 
that work in the context of WebLogic Server clusters and 
HTTP and other product tunneling. T3 predates Java Object 
Serialization and RMI, while closely tracking and 
leveraging these specifications. T3 is a superset of Java 
Object. Serialization or RMI; anything you can do in Java 
Object Serialization and RMI can be done over T3. T3 is 
mandated between WebLogic Servers and between programmatic 
clients and a WebLogic Server cluster. HTTP and IIOP are 
optional protocols that can be used to communicate between 
other processes and WebLogic Server. It depends on what you 
want to do. For example, when you want to communicate 
between a browser and WebLogic Server-use HTTP, or an ORB 
and WebLogic Server-IIOP.