# GANA-VDC: Application-Aware with Bandwidth Guarantee in Cloud Datacenters
## 1 Introduction
Apparently, the virtual network possesses enough space to map a lifting algorithm. Tenants desire an efficient allocation procedure. Hence, how to design a VDC allocation algorithm improving allocation efficiency poses another challenge to overcome. This paper presents GANA-VDC, a network virtualization framework supporting bandwidth allocation in cloud data centers. In this work, we observe primarily the network remains physically interconnected as a fat-tree to a second layer scalable and fault-tolerant routing and forwarding protocol, for cloud data center using commodity switches [16]. However, the commodity switches closure restricts internal information access and control, prohibiting application-aware networking. By deliberately replacing commodity switches with OpenFlow-based switches [17], we offer a flexible physical network infrastructure. Flowtable capacity typifies a limited resource, as flowtable capacity remains scarce. Given the cloud datacenter magnitude, the flowtable cannot practically accommodate the flow entry volume. OpenFlow permits scalable flow entries with the switches; thus, source routing was chosen as the preferred method. With source routing, even though one benefits from the switches' statelessness completely unaware of VDC and bandwidth reservation, one cannot avoid the challenge related to the inability of a tenant to enable properly fine-grained traffic on specified and concrete service type. As OpenFlow v1.3 protocol [18] offers a table of entries defining the flow meters to implement complex QoS frameworks, e.g., DiffServ [19; 20], the redundant flowtable-space is amortized on demand with pay-as-you-go pricing. Combining source routing with flowtable can be adapted to the diverse SLA requirements, and thus, two principal mechanisms in VMSG perform routing and forwarding: Firstly, one provides the fundamental bandwidth guarantee using source routing, the other targets fine-grained QoS relying on flowtable division. Datacenters tenants should be able to select their Self-Defined Network (SDN) controllers, e.g., OpenDaylight [21], NOX [22], and Floodlight [23]. The underlying physical network remains transparent to the network VDC controllers. To achieve this, we use switch-level virtualization, such as FlowVisor [10], in which several isolated networks with potentially differing forwarding and addressing tenants mechanisms are built on the same hardware forwarding plane. However, the challenge arises to support many tenants each characterizing a different topology and alternative application controller. The link service is the underlying network service the SDN controller eventually provides. It starts with learning physical links initially created between switches in the control domain utilizing instructing switches to send Link-Local Discovery Protocol messages (LLDP) out of all ports connected once the service is initiated. Once the number of tenant controllers expands to a particular scale, FlowVisor fails to sustain the overhead. In this work, we propose the design of hierarchical state maintenance and query algorithm for relieving the burden of FlowVisor. The state of high layer tenant link service can be constructed from the intermediate one conserved by low tenant link service, reducing the overall request number tenant link services send to each physical network switch. Efficient virtual network mapping to the physical network crucially gives good user experience, especially when the scale of VDC to-be-allocated proves enormous. As mentioned above, mapping VN to PN is an NP-hard problem. Therefore, we propose a heuristic switch-centered based VN to PN mapping approach to solve the VDC allocation issue in polynomial time. Converse to VM centered approaches, this method is parallel and more efficient. Our work includes the following contributions:  
* Designing a network virtualization framework for enabling application-aware networking with bandwidth VDC guarantees. * Maintaining VN mapping topology on PN, proposing the GANA model, a switch centered based VN to PN mapping scheme.