Protection techniques against overload in corporate networks

Abstract

Self-similar (fractal) bursty traffic is specific for corporate networks that often causes an overload of buffer devices. Therefore, packet delay variation can exceed admissible values and low priority packets are lost. All this leads to queues and reducing QoS as the lost packets are transferred repeatedly for the purpose to ensure required reliability. Control mechanisms of packet processing queues do not fully ensure overload reduction effect. That is why networks operate in the underloaded mode and that it is not cost-efficient economically. However, there are usually alternate paths to the network destinations in the telecommunication packet switched network. Therefore, when the router is overloaded then the traffic partly can be redirected via the redundant paths where the network elements are underloaded for the time being. Thus, the load reallocation (balancing) has to be performed in real time. Hardware and software system was designed for   research of overloads in networks. This system includes the equipment of Technologies of Package Switching laboratory (6 switches, 6 Cisco routers), and also the personal computer with five network interface cards that enabled to simulate a router. The new method was suggested which implies the redirection of the queued packets into redundant paths. The mathematical model of this method was developed. The method provides two ways of the traffic redirection. The first way consists in equitable distribution, i.e. equally along all existing paths. The second way implies the load distribution to threshold value of the next redundant router, i.e. the main path is loaded to the maximum, and the remaining traffic is reallocated along the redundant paths. When carrying out research the traffic was formed to make the router’s overload and partly the traffic was transferred into the redundant path and thus to prevent packets discard. To implement this method the router with the open initial will be used. The suggested methods of protection against overloads will enable to prevent packet discards as well as to use effectively network transmission capacity.