This paper mainly studies the composition and significance of SDN network and SDN controller, and illustrates the advantages of SDN network with the case of IP network traffic optimization.Comparing with traditional network and SDN network, the structure of SDN network, new protocols and their functions are expounded.The advantages and problems of SDN network are analyzed emphatically.Taking the backbone network of IP network as an example, this paper expounds the significance of SDN network to the whole network re-architecture.In the era of increasingly complex mobile networks and accelerating mobile technology updates, the rise of Internet companies has posed unprecedented challenges to operators, prompting operators to put forward a series of demands for their own networks to adapt to social development.In order to solve the problems of slow network innovation, lagging management, huge equipment and slow technological development, starting from network reconstruction, using the new thinking mode of SDN network, using the principle of separation of control plane and forwarding plane of traditional network, adopting SDN network architecture to transform equipment, thus speeding up technological innovation and business deployment, Create an open, intelligent and efficient mobile network.Mobile network plays a more and more important role in modern society, among which IP network is the most widely used. At the beginning of the birth of IP protocol, IP protocol only serves the Internet.With the development of IP technology, it is gradually used to carry voice, Vpn and other services.With the diversification of bearer services, the scale of services is gradually evolving towards ubiquitous and ultra-wideband.The traditional IP network will transit to the next generation IP network (NGI).At the same time, the business operation mode of IP business will also change.This has led to many problems faced by mobile network operators, such as: complex management, operation and maintenance; network innovation difficulties; increasingly overstaffed equipment, etc., at this time NFV/SDN technology came into being.Network Function Virtvalization (NFV) uses virtualization technology to decouple software and hardware of traditional telecommunication equipment. It realizes telecommunication network functions based on general computing, storage and network equipment, improves management and maintenance efficiency, and enhances system flexibility.SDN (Software Definef Network) is a software defined network.In 2000, a new network innovation architecture was proposed by clean slate research group of Stanford University.Following four principles: control and forwarding separation principle; centralized control principle; network business programmable; open interface.The essence of SDN is network software, which improves network programmability. SDN is a reconstruction of network architecture, not a new feature and function.
SDN will be better, faster and simpler than the original network architecture to implement various functional features.Nowadays, IP network management is complex and has many command lines. The real pain point is the slow deployment of services, the centralized control of the network, and the centralized control of the control surface to a software (SDN controller), so many things are solved.As shown in Figure 1.With the promotion of ONF (Open Network Foundation), NFV industry alliance and the active input of operators, network service providers and equipment manufacturers, the SDN model has gradually reached a consensus.As shown in Figure 2.Collaborative Application Layer: Software applications that communicate with the controller.Extension for network services.A variety of upper-level applications that accomplish user intentions are called collaborative applications. Typical collaborative applications include OSS, openstack and so on.OSS is responsible for the business collaboration of the whole network, while Openstack is responsible for the collaboration of network, computing and storage in the data center.OpenStack is currently the most active open source cloud computing management platform, providing the network as a service function.The collaborative application layer and the control layer are defined as the northbound interface (NBI, Northbound Intterface).Network Configuration Protocol (Netconf) is a North-South application protocol.The northbound interface is located between the control layer and the application layer, which abstracts the network capability and information provided by the controller and opens it to the application layer.It determines the direction and value of SDN development and is of great significance.The northbound interface mainly includes several interfaces: REST and RESTful services.REST (Representational State Transfer) is a WWW based on software architecture style. REST-based services become RESTful services.Restful interface for network management, port management, business management.NetConf and RESTful are also East-West agreements.Openstack Plug-In interface is used for network management, firewall management and router management.NetConf interface: used to manage SNC. routers and switch devices; XML-based network configuration and management protocol.NetStream is also a northbound interface. It is a statistical technology based on classified statistics of network traffic and resource usage.Mainly used in time or traffic based billing and reconciliation, network planning and analysis, network monitoring, application monitoring and analysis, user monitoring and analysis.Control Layer: Control Layer is the control center of the system, responsible for the generation of intra-network switching paths and boundary service routes, and responsible for handling network state change events.Its implementation entity is the SDN controller, which is also the core component of the SDN network architecture.There are also other collaboration layer applications such as secure APP, network business APP client, etc.Its core function is to realize the calculation of intra-network switching path and boundary service routing.It includes a logically centralized SDN controller, which can accomplish network resource scheduling and control well.The interface between the collaborative application layer and the forwarding layer is defined as the south bound interface.Southward network control technology needs to manage and schedule the device layer in the whole network, including link discovery topology management strategy formulation.It is also necessary to implement integrated management and network equipment monitoring through clearly defined application layer interface requirements and standard protocols.The south-facing interface mainly includes several CLI interfaces: for managing firewalls; MROSI interface: for docking with U2000; SNMP interface: for managing router devices; SFTP interface: for obtaining performance data from U2000.As shown in Figure 3.
Infrastructure layer or forwarding layer: including physical network devices, Ethernet switches and routers.Provides programmable, high-speed hardware and software.In the software definition network, the control plane and the forwarding plane are separated. The forwarding layer is mainly composed of the forwarder and the line connecting the forwarder. This layer is responsible for the transmission of user data. In the forwarding process, the forwarding table entries are generated by the control layer, not the forwarder.Forwarding table entries can be two-tier forwarding table entries or three-tier forwarding table entries.The forwarding layer reports network resource information and status on one hand, and receives forwarding information from the control layer on the other.Location in SDN is defined as OpenFlow protocol between infrastructure layer and control layer, which is the basic element of building SDN network.It is a very famous south-facing interface protocol.It is used as a communication protocol between OpenFlow controller and transponder.OpenFlow is a flat interface or standard-based protocol.Define platforms and data plane devices between controller communication controllers, such as physical and virtual switches and routers.Including OpenFlow PCEP SNMP OVSDB and other protocols.Network Configuration Protocol (NETCONF) is defined as a network configuration and management protocol based on Extensible Markup Language (XML).NETCONF provides a mechanism for removing and operating network devices; a network management protocol for remote management and monitoring of network devices.A set of standard operations and RPC calls are provided to manage network devices.Use SSH transport protocol.Simple Network Management Protocol (SNMP) with Southward Interface is a standard protocol for network management widely used in TCP/IP networks. It is used to collect, manage and modify equipment information.As part of the TCP/IP protocol family, SNMP messages are encapsulated as UDP messages and transmitted over the Internet.The functions are network management station (NMS), agent and managed equipment.East-West interface includes Restful interface and SFTP interface: NetMatrix provides network resource interface, through which uTraffic obtains network resource data from NetMatrix.UTraffic provides a real-time traffic interface, through which NetMatrix obtains real-time traffic information from uTraffic to display real-time traffic situation and traffic trends.Under SDN network architecture, since the whole network belongs to SDN controller, the reliability of SDN controller is particularly important.A comparison of the reliability of traditional networks and SDN networks is shown in Figure 4.The reliability of SDN controller mainly involves four aspects as shown in Fig. 5.SDN Controller Architecture Performance Requirements.Performance analysis of the first time index and convergence time of the network: It is required that the convergence time of the network is equal to that of the traditional network when the controller is deployed.The second space index: and the implementation technology DC requires support of more than one million OVS (OpenvSwitch) capabilities; DCI/METEO/CORE, each controller controls 2000 devices; IPRAN access scenario, each controller controls 20,000 devices.SDN Network Value.First, the programmability and openness of SDN make it possible for us to rapidly develop new network services and accelerate business innovation.The second SDN network architecture simplifies the network and eliminates many IETF protocols.The removal of agreement means the decrease of learning cost, operation and maintenance cost and the increase of deployment speed.The third is the generalization of network equipment.Fourth Business Automation: Self-deployment of network services to provide network automation capabilities.Fifth, network path optimization and traffic optimization: When SDN network architecture is adopted, SDN controller can adjust network path intelligently according to network traffic status to achieve the purpose of improving network throughput.The sixth SDN is a reconfiguration of telecommunication network.
In the SDN era, most of the network business needs can be adjusted as quickly as IT applications, and new services can be deployed quickly.There are mainly applications of data center (DC) network based on SDN/NFV.With the gradual cloud of enterprise business, resource centralized management, thermostatic element flexible network adjustment, high-speed, low-latency dedicated bearer network for data center interconnection is also a problem to be solved. SDN enables DCI (data center two-tier interconnection) to meet this demand.With the rapid growth of Internet traffic, the telecom industry has been exploring ways to reduce the cost of backbone networks.Taking SDN as an example, this paper illustrates how SDN optimizes the backbone network of MPLS.The networking architecture is shown in Figure 6.Includes WAN (IP CORE) solutions, DCI solutions, Cloud VPN solutions PCE traffic tuning solutions.Among them, Agile Controller-WAN is the core component, mainly for WAN (IP CORE) scenarios DCI scenarios and Cloud Vpn scenarios, to achieve rapid distribution in the WAN field, optimize intra-domain traffic, simplify modern networks, and reduce the operating costs of existing networks.
Agile Controller-WAN solves the problems of slow business deployment, low network utilization and complex maintenance of operators by providing on-demand services, network tuning, telecommunication-level reliability, visualization and open innovation.PCE traffic tuning PCE (Path Computation Element) is a centralized computing mode based on MPLS TE, which solves the limitation of independent computing of traditional MPLS TE.PCC (Path Compution Client) requests path calculation from the Ingress node of the tunnel to PCE Server. After PCE Server returns the result of path calculation, PCC triggers RSVP-TE protocol to establish LSP.It mainly includes: PCC (transponder) is responsible for TE tunnel creation, bandwidth label resource reservation, and is the owner and manager of TE tunnel.PCE Server (Controller) is the computing center. It collects TEDB-Traffic Engineering Database information through IGP-TE and is responsible for centralized computing.PCE is based on the evolution of PCE technology, and the main difference between PCE and PCE is: PCE (also known as Passive Stateless PCE): the transponder reports LSP information but does not delegation, that is, the controller will not actively send information to the transponder.At the same time, the controller can only receive TEDB information, and can not receive LSP-DB-Label Switched Path Database. It has no right to actively optimize the paths of different PCCs with the goal of global optimization.PCE (also known as Active Stateful PCE): The transponder authorization controller manages the managed LSP, while the controller collects LSP-DB information based on PCEP protocol, and calculates network optimization based on LSP-DB, so as to actively tune for global optimization.PCEP (Path Computation Element Communication Protocol) protocol is a communication protocol between PCC and PCE Server.
It collects RSVP-TE LSP information of the whole network and provides centralized computing services based on it.PECP only provides the standard definition of PCE south-facing interface, but does not include PCE computing method. PCE has its own centralized network optimization algorithm, which supports path calculation based on COST, bandwidth, delay and other SLAs.PCE for SR-TE: In addition to RSVP-TE, PCEP also supports collecting SR-TE LSP information and tuning SR-TE LSP.Including northward protocol RESTCONF, Syslog client, AAA, SFTP, client, SNMP agent.SNMP client NETCONF, SFTP Server, Trap Server, PCEP, BGP, BGP-LS/GP.At present, the most developed protocols are Openflow and Openstack, and the technologies are in the stage of gradual improvement.From the application of Agile Controller-WAN software based on SDN network, this paper illustrates that it speeds up the business deployment of operators, reduces the workload, and does not need the cooperation of multi-departments and manufacturers.In order to improve network efficiency, rapid response should be made to adjust network traffic globally, and the results of the optimization can be perceived in time.The network maintenance operation is simple, and the location time is short, and the network reconfiguration is realized.From explaining the composition of SDN network architecture to the application of SDN in IP network, this paper elaborates the great significance of SDN network to the re-architecture of existing network.This review solves the problem of mobile network adapting to the development of the times, carries out a series of reforms to the network, and adopts the latest new protocols and standards in the field of communication.Thus gradually improve the transformation of the existing network.Create a brand new mobile network to meet the requirements of the times.