Study On Overload Control Mechanisms In NGN Service Architecture

It is the root cause for network overload that the network resources cannot meet the user demand.Many factors will cause a network to be overloaded,such as the unpredictable behaviours from end users,the cost limitation on the network construction,the non-economy of network over-configuration,and the increasing demands,and so on.The objective existence of these factors makes the network overload control as an issue that must be solved in the various networks.Furthermore, the following factors in next generation network(NGN) make the overload control more difficult than in traditional network,which makes it as a hot research focus. Firstly,the next generation network is a distributed system.The IP multimedia system (IMS) is the core network in NGN to provide the multimedia services,and it is comprised of multiple components with differenet functionalities.These components cooperate with each other to serve end users,and this cooperation increases more interactions between them and dependence on each other.Secondly,the singalling control is separated from the bearer control in NGN,which needs a new effective mechanism to implement the overload control between the components in these two layers.Thirdly,multiple protocols co-exist in the NGN.These protocols interact with each other to provide end-to-end services,but they have different capabilites on the overload control.Fourthly,the NGN enables the network and/or service capabilites to be open to the 3^rd party via the APIs,which allows the 3^rd party to develop the telecommunication services,and make it possible for 3^rd party to run the telecommunication services,and make it true for different 3^rd parties to run their servies on the same service execution environment.This can help to accelerate the service development.But the openness requires the network operators and the service providers to establish the service level agreement(SLA) to protect the interests of both sides.These SLAs should be enforced in the network in a real-time way.Fifthly, the NGN provide the converged multimedia services,which consist of voice,data, video and other media.The traffic types' increasing and the best-effort and connectless transporting make the burst and unpredictability of the traffic higher than before.Sixthly,user demands for new services varies daily,and the individuality will be one important characteristic in the NGN services,which needs services to be developed and deployed in a rapid,convenient and economic way.The separation of non-functional service features such as overload control from the service feature is one efficient way to implement it.And the individuality is not only characterized that different subscribers have different demands on the service features,but also pay more attention to the users' experience.Based on the distributed,modularized, multiple-protocols,convergent and open network architecture,the multiple traffic types,personalized service demands in NGN,this paper mainly focuses on the topics on the network overload control archicture,overload control component distribution, the customers' perception,and efficient resource usage in open environment,and proposes the network overload control architecture and mechanisms that satisfy the demands for the NGN overload requirements.The detail can be outlined as follows:1.Based on the distribution,modularization,multiple-protocol and openness in NGN,a policy-based overload control architecture is proposed.This architecture is composed of 6 types of components,which is located in the different IMS components.It employs the general overload control application protocol (GOCAP).And the policy control gives full consideration of the business demand between the network operators and the service providers in NGN.2.Built on the NGN service architecture and the above overload control architecture, the concept "adjacent-resource" is proposed.A search algorithm is presented to locate the adjacent resources according to the component dependence formed by their process sequence to perform the user service,thus the control point can be located at the neareast to the user and throttles the request at the logical adjacent resources.The algorithm can efficiently solve the overload issues the SIP fork function and load balance bring about,reject a request as soon as possible,which helps to reduce the traffic in the network and overloaded resource and improve the efficiency of the network capacity and the resource,and satisfies the overoad requirements that ETSI TISPAN proposes for the NGN.3.Users' experience will be the important factor that will have a signifant impact on a user's decision to choose a service.Besides the service features,the QoS attribute is paid more and more attention to.Based on the psychophysical laws and user's patience characteristic,the paper proposes a dynamically priority queueing system,which employs a greedy admission control algorithm to schedule the services.The analysis and simulation shows that the scheduling policy has more advantages on the system throughput,the wait time and the degree of a user's satisfaction over other three methods under a heavy load in the multi-service environment.This scheduling policy can meet a multi-service overload control requirements in NGN.The introduction of users' patience to the network control is a meaning trial to satisfy the demand for the customer-centred NGN.This also embodies that the NGN is a service-driven network.4.The open NGN service architecture enables the network capabilities open to the 3^rd party via APIs,such as the Parlay/OSA API,which helps to prompt the service demelopment.The services from different service providers may coexist on the same service platform Thus a SLA contract must be established and maintained between the service platform providers(network operators) and the service providers to protect the interests of both sides.So the service platform must control the service requests according the SLA contract in a real-time way.Based on the broad overload control connotation,against the contradiction between the resource efficiency and the SLA constraints,the paper employs the Nash Equilibrium theories,proposes two SLA-constraied overload algorithms to solve the "resource-surplus" and "resource-shortage" concurrent existence,which help to make full use of the resources of the service platform and the network.Herein, the overload is extended from over the network capability to over the SLA business contract.