Study On Key Technologies Of Broadband Access Network For Efficient Application Carrying

In recent years, with the emerge and development of the high speed and strict quality requirement services, such as IPTV, HDTV, Online Games and P2P applications, the requirement for bandwidth grows rapidly. The operators become to focus on broadband access network building. The P2P traffic increases fast and it has used half and more network bandwidth. The coexistence of P2P services and C/S services becomes an important feature of the access network. More and more, some new type multicast such as ALM(application layer multicast), overlay multicast and so on take the place of traditional IP multicast which is not suitable to deploy on a large scale and become the research hot point. It seems to become the main trend in the future. So, how to support these kinds of new type application is an urgent and hard problem in access network domain.As one of the most important broadband access networks, the traditional EPON does not support the direct communication between ONUs. When EPON carries P2P applications, network throughput will decrease rapidly and the switch burden in OLT is heavy. When EPON carries tradition IP multicast and ALM, it doesn't make use of physical layer multicast character, so there is some problem such as bandwidth wasting, topology mismatch. Furthermore, the rapid transformation and naissance of new type application bring forward the "flexibility" demand to the network equipments, especially the alteration and upgrade of P2P and ALM.Aiming at the continuous naissance of the new type applications and the coexistence of P2P services and C/S services, this paper research on the overall frame, multi-application carrying strategy and reorganizable flexibility based on a novel EPON network architecture which is both master-slave and reciprocate. Besides, the paper designs the proto system software, do experiments to validate the feasibility of mentioned above. The main contributions of this thesis are as follows.1) A novel EPON architecture and a novel medium access control protocol which can realize direct packets transmission between ONUs are participating proposed. A circle PON ODN structure based on splitter combination, physical layer transmission and Medium Access Control mechanism is mainly worked over.2) Aiming at P2P application characteristics and low carrying efficiency by network, especially the mismatch problem between P2P overlay layer and actual network layer topology and swallowing a large number of bandwidth of core network, the paper brings forward a P2P redirect mechanism based on a wire-speed DPI method. The mechanism alleviates the bandwidth wasting problem to some extent. Its feasibility and effectiveness is validated by Markov chain theory-based analysis and simulation based on NS2 tools.3) Against the low efficient problem of multicast such as topology mismatch and extraordinary protocol demand to net devices, a IP multicast carrying strategy base on snooping and a ALM carrying strategy base on "Redirect & Flow Copy" is put forward. Further more, a overlay multicast structure based on access network devices is put forward too. In the structure, setting up a minimum cost multicast tree is solving by a heuristic algorithm (based on genetic algorithm). All of above, the objective is to alleviate core network traffic burden, reduce redundantly data forwarding, water down the demand of whole routers and so on. The simulation results show effectiveness.4) The paper research the reorganizable software architecture, brings forward a application-oriented reorganizable software architecture. On the architecture, the network device software can be reorganized dynamically like "hot plug". Second, a quantitative analyzed method based on Petri net theory for the software reliability on reorganizable platform is put forward. The reorganizable platform makes great sense to the "feasibility" of the service transformation along the demand changing. It can be evaluated easily by Petri Net or Markov chain theory tools.5) The paper participates in designing a master-slave and reciprocity EPON experimental system and conducting experimental research. The feasibility of reorganizable software architecture, the effectiveness of P2P redirection mechanism has been verified. The experiment results show that the prototype system, with P2P redirection mechanisms can save the traffic of core network for more than 30%, download speed increase more than 20%. The advantages on reducing traffic burden and enhance user experience are obvious.