This paper presents our experience in implementing OMG Unreliable Multicast Inter-ORB Protocol specifications into an ORB. An integration model is proposed to allow the coexistence of two different protocol stacks (IIOP/TCP/IP and MIOP/UDP/IP multicast) making possible a large spectrum of middleware support for distributed objects communication. That integration model is discussed in this paper, giving evidence of the compatibility of our approach with the CORBA specifications. In order to evaluate that integration, different tests were made considering interoperability, performance and scalability aspects.