Networking of multi-domain unified communications systems: Structure design and performance evaluation

UC (Unified Communications) can integrate different terminals and media and has played an important role in some enterprises. However, for large UC system with multiple domains, there still exist unsolved issues such as large call delay, overlay management overhead, and bandwidth costliness. In this paper, the hierarchal structure, call routing, and bandwidth usage of the multi-domain UC system are studied. After describing the architecture of the multi-domain UC system, a no-worse-than-two-hop query algorithm based on P2P is proposed for inter domain call, and it is showed that 80% users can finish call query in one hop based on the derived performance formulas. Then, the typical transmission networking structure is designed with an overlay between provincial domains, and the bandwidth requirements of signaling and media traffics are estimated. By comparing the performances of overlays with mesh, star, and hybrid topologies, the hybrid overlay topology is showed to be the best choice in terms of cost and manageability for the typical traffic distribution. In the overlay with hybrid topology, the media traffic routes can be controlled dynamically with SDN (Software Defined Network), and the overlay bandwidth reserved can be used efficiently with utilization up to 84%, thus demonstrating the technical and economic feasibilities of the proposed transmission overlay.