The protocol defined in this Recommendation is called the Service Specific Connection Oriented Protocol in a Multilink and Connectionless Environment (SSCOPMCE) and provides assured data delivery between AAL connection endpoints. SSCOPMCE is a peer-to-peer protocol which provides the following functions: transfer of user data with sequence integrity, error correction by selective retransmission, flow control, connection control, error reporting to layer management, connection maintenance in the prolonged absence of data transfer, local data retrieval by the user, error detection of protocol control information, status reporting, and out-of-sequence delivery. This Recommendation enhances the specification in ITU-T Q.2110 to allow the SSCOPMCE mechanism to be deployed not only on a single ATM connection but also: on multiple ATM connections between the same endpoints, or on a connectionless network. When deployed on a single ATM connection, the protocol defined in this Recommendation is interoperable with the protocol specified in ITU-T Recommendation Q.2110. This Recommendation describes the necessary elements for layer to layer communication, the elements for peer-to-peer communication, a detailed protocol specification, and examples of assured data operation.