Consolidation Problems and Solutions for ABR Multicasting Service in ATM Networks

The key issue at a branch-point switch for multicasting (point-to-multipoint) available bit rate (ABR) flow control is how to consolidate backward resource management (BRM) cells returning from each branch to avoid feedback implosion. However, consolidating BRM cells at a branch point can cause undesirable effects such as consolidation noise, consolidation delay, and consolidation loss. This paper first investigates the consolidation problems and proposes their solutions. Furthermore, this paper introduces various implementation alternatives for the proposed solutions. A combination of the proposed solutions, in which each branch point stores feedback information on a per-branch basis for each multicast virtual connection and only passes BRM cells returning from the farthest destination, provides a good fairness, a higher efficiency, and an excellent scalability. In addition, if a fast overload indication is additionally employed, the feedback delay can be significantly reduced in an overload situation. Key-Words: Consolidation, Multicasting (or Point to Multipoint), Available Bit Rate, ATM