An SDN Framework with Software-Defined Pricing (SDP)

Software-Defined Networks(SDN) is in the research process. With the idea of SDN, networking resources like switches, routers and types of Network Elements (NEs)are managed as kinds of virtual resources, forming virtual networks so as to provide rather flexible services to network users. In this research process, we noticed that how to price the services and the use of virtual network resources in an SDN is as critical as how the SDN is defined. We consider that it seems a precious idea to treat a service pricing mechanism as part of the SDN framework and to manage it in a software-defined way. Network service prices are traditionally determined by service providers in a rather rigid way, which lacks of flexibility and sometimes even fairness to resources users. By means of the idea of SDP, it is able to treat service pricing as a part of SDN, forming a service pricing model flexible to time, traffic and other network factors and status. In this way, it is expected to promote the efficiency of SDN resources usage and ease the management for service providers.

Software-Defined Pricing (SDP) is an idea specific to network management, whose core is that the service prices of network resources are determined by means of software-defined algorithms and/or mechanisms, which figure the prices according to various factors and status of the network resources. In contrast to SDP, service prices may be pre-determined rigidly by service providers. An SDP Protocol is an instance of SDP implementation shown in a way of protocol, which specifically defines algorithms and/or mechanisms to price specific services and use of network resources. An SDP protocol may be a private protocol if it is defined by a service provider personally, or a public protocol if defined publicly by standardization organizations. By use of the software-defined mechanism, SDP essentially supports automatic negotiations of prices in a pricing process. Automatic resource and price negotiation features a Guaranteed Service (GS). As a result, SDN with SDP essentially supports GS services. Network users must accept and abide by the network SDP protocol when they use the network resources and the services. An SDP protocol usually includes trading partners, trading content, obligations and other transaction costs. Service providers can make provisions for users in terms of workload and resource use. As an example, we present a typical process for an SDP protocol. When users expect to use resources from a virtual network by a service provider, users first query prices of various resources and services by means of the SDP protocol. The service provider returns the resource prices to users. Then, users will start up a price negotiation process with the service provider by use of the SDP protocol. Both the user and the service provider will proceed the price negotiation process based on their specific price negotiation algorithms. The negotiation process will be ended only from the user with the SDP protocol. It will end with an agreement is either met or not. The SDP protocol process is shown in . Usually, in a negotiation algorithm, the user or the service provider are able to take into consideration of current network status and other network factors, which make the price negotiation process much more efficient and flexible than traditional pricing methods.

| -----------------+ | | | | | | search price | | | | | | <-------SDP protocol--------|<-----------------+ | | | | | --------SDP protocol------->|------------------+ | service | | user | | | price negotiation| | sprovider | | | | <-------SDP protocol--------|<-----------------+ | | | | | --------SDP protocol------->|------------------+ | | | | | | negotiation ends | | | | | | <-------SDP protocol--------|<-----------------+ | | +------+ + + +-----------+ ]]> To fulfill above process, an SDP protocol header may usually include fields like shown in , where: ID: the unique identifier of the protocol header. Level: service priorities identified. Expression: including one or more ITP(ID-Type-Properties) formats, where ID is the unique identifier of a resource, Type is the type of resource, Properties is the attributes of the resource. TimeSpec: a structure of service time, mainly refers to the selection of the service period. Price: the price of the transaction. ContractTime: trading hours. State: trading status with success or failure.

(TBD)

SDP can be applied to SDN architecture well because of its natural software-defined feature. In SDN architecture, control plane and data plane are separated to achieve the segregation of the control and forwarding. A typical SDN architecture usually includes: application layer, control layer, and infrastructure (forwarding) layer. To adopt SDP in SDN, an SDP module is applied. An SDP module implements the SDP protocol and corresponding negotiation algorithms/mechanisms. An SDP module can be applied to any layer in the SDN, where resources need to be priced. In this way, theoretically, all kinds of network resources and services can be programmed in terms of use prices as well as resources functions. This makes SDN more complete regarding its software-defining characters. In SDN application market, resource providers and resource consumers actually hardly know each other fully for the value of resources and services. Hence, the trade between them is an information asymmetry game. To take this into consideration, an SDP module with its protocol and associated negotiation mechanisms applied to an SDN system is usually of the following features: 1) An SDP module can be distributed across parts of SDN system, to get the optimal level of service quality under budget constraints of service consumers. As a result, the SDP module usually further contains a pricing module and a trading module, used for pricing and trading of resources respectively. With an SDP module, users can submit their requirements according to their budgets at the SDN application layer to SDN control layer. Then, the SDN control layer can get results of optimal resource services based on user's budget. 2) An SDP module usually includes an auto-negotiation mechanism. During the trading process, resource providers first get the price based on the price algorithm and/or mechanism, and present them to resources consumers. If consumers are not satisfied with the prices, process of negotiation with auto-negotiation algorithm or mechanism will be triggered. 3) With SDP, use of resources and their prices are not unique anymore. Different resources providers may provide different prices even for the same resources. SDP module may query different resources providers for optimal prices. This process usually takes place at the SDP protocol stage of searching prices. 4) In an SDP transaction, an SDN application usually act as a resource provider to end users. Whereas, at the same time, it can also act as resource consumers to SDN control plane as well as SDN forwarding plane. It sells resources to end users. At the same time, it may buy or hire resources from SDN core systems. All these can be done by use of SDP module. 5) With a time attribute, SDP can respectively support SDN applications well for temporary term users or long term users regarding optimal use prices.

As mentioned, a typical SDN framework usually includes Application Layer, Control Layer, and Infrastructure (forwarding) Layer. In SDN Application Layer, things like virtual servers and other SDN personalized services will be presented as individual SDN Applications. Based on the idea above on adopting SDP to SDN, a typical framework of an SDN system which adopts SDP module is as shown in .In this framework, the SDP-App includes an SDP module inside and makes the module support software-defined pricing function. SDP-App may exist in each layer of the SDN framework. Note that, SDN Application communicates with SDN controllers via the AD-SAL and Service Interface.Either should require that the AD-SAL and Service Interface must support SDP protocol to support the SDN with SDP. Also note that, SDN Control Layer includes the network service, SDP-App, and control abstraction Layer(CAL), it is defined to communicate with SDN forwarding layer by means of the resource abstraction layer(RAL) and the uniformly defined SDN southern interface protocols like ForCES ,OpenFlow, etc. To support SDN with SDP, SDP protocol must be designed supportable by these protocols for messaging purpose. This may become a key question for the design of an SDP protocol. The SDN Forwarding Layer includes the network element, and SDP-App. It is exposed via the Resource Abstraction Layer (RAL), which may be expressed by one or more abstraction models. (TBD)

As another example, we try to present an SDN application which uses SDP to access network resources so as to get optimal resources use price. We call the SDN application a 'Chat' App, which is to construct a social App platform to connect, communicate and share among people and things by means of Guaranteed-Service (GS) rather than Best-Efforts (BE) services to users. Hence, the App needs to hire network resources from cloud network service providers to provide virtual server and Guaranteed Service (GS) resources. Fig 4 shown the process for 'Chat' to access the GS Resources by use of SDP. 'Chat' client and 'Chat' Server makes service agreement via SDP module. 'Chat' server may be implemented as a virtual server, whose pricing is also implemented by SDP module. Further more, resources to support the virtual server and the 'chat' message forwarding are used based on SDP negotiations. As shown in , in this case, SDN controller inside the virtual server of 'chat' may send requests to multiple cloud platforms by SDP module(such as Sina cloud, Baidu cloud and Ali cloud in the figure). All the cloud service providers return with resource prices, and SDN controller inside the 'chat' server select or negotiate with the cloud service providers. SDN controller finally may select or get a successful or failed negotiation results and returns to the 'chat' client via SDP protocols. As a result, a transaction for a GS service pricing ends.

A Meta-Model is a model architecture in which each defined layer will supply services and functions that built in a meta-model, to be exactly, APP-likely way. Then all of APPs could be refactoried and combined to satisfied sorts of diversified needs from users in upper layer. To be more precisely to defined the meta-model, the following elements will be invoked: Meta-APP:the minimum logical elements in application layer that be used to combine and register applications with more complexity. Meta-APPs includes all of function feature and needs of application, and they could abstract the fundamental functions of network service needed by business according to feature and requirements of application. Con-App:Business Abstraction Layer:It is a mechanism that be used to map the meta-app to the corresponding meta-service in the application layer. Business Abstraction Layer will recognize and adapte all of meta-service supplied by controller, and then select suitable meta-service to service a meta-app bases on the requirement of relevant business. SDP-App:The modules which could support software-defined pricing function in the aspects of resource and service from each layer. Meta-Ability: The fine-grained elements of switch function in switch layer, which is the atomic elements in divide assignment. It is the fundamental host components. All of the meta-ability can supply diversified host ability for meta-service within the scope of world-wide network. Resource Abstraction layer: Mapping the physical resources to virtual resource. Resource Abstraction Layer uses virtualization technology to abstract physical resources at the bottom in order to shidding the difference between facilities. In addition, Resource Abstraction Layer can schedule resources to achieve its reasonable alloction, which can avoid the quality reduction of upper layer application due to the resource shortcut and waste in result of its long-term idleness, raising the resource untilization ratio. Based on the idea above on Meta-Model to SDN, a typical framework of an SDN with SDP bases on Meta-Model system is as shown in .In this framework, the application layer includes a meta-app part inside and makes the module support dividing and refactoring the meta-service . (TBD)

As the mentioned definiton of SDN framework with SDP bases on Meta-Model above, the minimum units of application are meta-app, which of control layer are meta-service, and the minimum units in forwarding layer are meta-ability. Meanwhile, Refering to the idea of reconfigurable network architecture, The features of business and the load capacity of network could be abstract as a chained model like "Application -> Meta-App -> Meta-Service -> Meta-Ability" which be showed in . A complicated network application can be divided to amounts of meta-app abstractly, and each meta-app contains features and functions of network applications. In this case, The meta-app is also combined by a series of fine-grained meta-service sets that called network fundamental function components. In addition, A set of meta-abilities can combine a series of fundamental load components of network, which can associate meta-service. (TBD)

---------->-| Meta-service |->-+------->-| Meta-App |->----+ | +--------------+ | +-------->-+--------------+ | | | +----------+ | | | | | | | | | | | | +--------------+ | | | +--------------+ | +------->-+----------+ | | | | Meta-ability |->-+-------->-| Meta-service |->---+----->-| Meta-App |->-+ | | +--------------+ | | +------>-+--------------+ | | +->-+----------+ | | | | | | | | | | | | | | +------>o-------------o | +--------------+ | | | | +--------------+ | +---|->-+----------+ | +--------->| Application | | | Meta-ability |->-|-+------>-| Meta-service |->-+-----|->-| Meta-App | | +---->o-------------o | +--------------+ | | +----->-+--------------+ | | | | +----------+ | | | . | | | | . | | +---+ | | | | . | | | | . | | | | | | | . | | | | . | | | | | | | . | | | | . | | | | | | | +--------------+ | +--|----->-+--------------+ | +-|----->-+----------+ | | | | Meta-ability |->----+ | | Meta-service |->---+----->-| Meta-App |->------+ | +--------------+ | | +--------------+ | | +----------+ | | | | | | | o------------------o o------------------o o--------------o ]]>

As shown in A complete SDN environment is made up of application layer, control layer, data forwarding plane, if regard SDN environment as an economy market ,Then corresponding to the three layers structure of SDN environment, the economy market can be divided into: user layer, trading platform and provider layer. But each layer is embedded with the pricing model and consumption pattern which is apply to this layer , the communication between each other is accomplished by special protocol, each of them is independent but closely linked.In application layer, there are many users, the users were independent of each other, and they belonged to different platforms.In control layer there are multiple platforms, on the two ends of platform respectively connected to different users and providers, the existence of multiple platforms can solve the monopoly of a single platform and the problem that users and providers'choice unicity.In fowarding layer,there are many providers, they can offer different types of resources for each platform.

We summarize the differences of three kinds of trading pattern and the position of SDN architecture which applied them , as shown in :

The commodities mode, trading market and other factors of planned trading decides it apply to the entire SDN market; the commodities mode of spot trading determines which is suitable for small number of resources trading, and it has some risks, therefore it works in the application layer of SDN architecture; the commodities mode of futures trading trade in a kind of resource as a unit, and the risk is small, possess the futures market, so it works in data forwarding layer of SDN architecture.

TBD

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