In this paper,a network-level abstraction called phi -channel that supports the requirements of real-time applications is proposed. A phi -channel represents a simplex, end-to-end communication channel between a source and a destination. The channel is characterized by a set of specific performance parameters associated with its traffic, namely packet maximum end-to-end delay and the maximum number of packets that can be sent over that delay. The primary attribute supported by the phi -channel is on-time reliability. The basic scheme used to verify the feasibility of accepting a phi -channel, and the run-time support to guarantee its performance are described. The results of a simulation experiment implementing the basic functionalities of the proposed scheme are presented.