The Design And Implementation Of Forwarding And Control Separation System Based On PPPoE

In the era of "Internet plus",the changing needs of network services have been continuously updated,and the flow of IP-centric in ISP(Internet Service Provider)network has grown exponentially which exposes some of its shortcomings when dealing with large-scale network traffic.PPPoE is a very mature protocol that is widely used for broadband access at BRAS(Broadband Remote Access Server)equipment in ISP network.The BRAS device is a large-scale network equipment which is tightly coupled with the forwarding and controlling functions.It is responsible for the users' PPPoE connections and aggregates traffic,and cooperates with the AAA server to implement authentication,authorization and accounting management for clients.The user control and data forwarding are both processed by the BRAS device with the result that the processing load of CPU of it would be severely consumed and the hardware forwarding capability is not utilized effectively.In addition,its computing and forwarding capabilities are set to a fixed value at the factory.If the band is needed to increase,only the latest device can be purchased so that the cost of updating the hardware equipment is too great.In view of the drawbacks of the current implementation scheme for PPPoE used by ISP in the BRAS device,this thesis proposes a new access scheme to achieve the separation of PPPoE forwarding and control functions,using the design concept of SDN,which uses two new devices(CP and DP)to carry the forwarding and control functions in PPPoE module to decouple the forwarding and control planes.CP is a control plane device as a virtual BRAS using virtualization technology.While DP is a forwading plane device to implement distributed data forwarding.On the one hand,CP could achieve centralized control and flexible expansion so that it is flexible to expand its hardware resources.On the other hand,as the control function is weaked in DP,it is making gradually DP to evolve towards general forwarding equipment.In this thesis,once a request packet of PPPoE is received from the client,DP forwards the packet to CP through the VXLAN tunnel,and CP gives a response.Only protocol packets of PPPoE are transparently transmitted in VXLAN tunnel.After client going online,CP deliveries the PPPoE protocol data to DP through Openflow messages.The client's traffic packets are forwarded only through the routing table generated by DP forwarding module.Finally,according to a test suite,the basic separation function related to PPPoE packets of control and forwarding planes are tested by building a test environment at a company.What's more,the dialing function and the speed limitation of packets are also tested.The test results show that the implement of this thesis could meet the project requirements.