# GANA-VDC: Application-Aware with Bandwidth Guarantee in Cloud Datacenters
## 2 Related work  
Researchers in cloud datacenters have concentrated on providing a sophisticated solution for supporting VN performance separation in the cloud data center. Presenting diverse bandwidth allocation VN models, such as traffic matrix [13]; engendering a fixed bandwidth, e.g., the hose model with invariable bandwidth [14] or where the bandwidth varies with time [24] or a TAG model based on a communication structure between applications [19]. Choosing from this variety, researchers design their proper version of VN to PN mapping algorithms. However, the above works only emphasize practical VN models conveying the communication relationship among VMs and VN to PN mapping efficiency, and none of these proposals intend to provide fine-grained QoS for VDC. Currently, despite self-defining network topology, VDC tenants cannot self-define control networks logic. We summarize the requirements to consider in such a scenario in the cloud data center. **Virtualization:** According to [PERSON] et al., a virtualized data center is a data center where some or all of the hardware is virtualized [25]. This is achieved by simply ensuring the different components are isolated and independent virtual instance [25]. This process faces a unique problem known as VNE. Virtual Network Embedding (VNE) is a common challenge faced by different researchers. [PERSON] et al. 's proposal is one of the viable solutions to this process. They highlighted the importance of self-configuration and organization of the network [26]. According to the authors, good service is computed based on either QoS, economic profit or survivability over energy-efficiency to the security of the network. The most palatable procedure, in this case, is to ensure virtual resources are allocated to physical infrastructure in the most optimal method [26]. These resources are allocated to nodes as well as links (Virtual Node Mapping (VNoM) and Virtual Link Mapping (VLiM)). To further simplify the challenge, the authors suggested that all VNE approaches should be categorized as \"static or dynamic\", \"centralized or distributed\" and \"concise or redundant\". **Optimization:** Optimization is therefore key in the virtualization process. The authors detailed this in their editorial into different steps. By considering small instances of the challenge, the authors discussed exact solution, heuristics-based solution and metaheuristic solution. Besides this, embedding metrics must be considered, including quality of services metrics, cost-related metrics and resilience metrics [26]. Quality of service is related to this topic where different metrics define the proposition. QoS is derived from the following entities, which are used to discuss a network: path length, stress level, utilization, throughput, delay and jitter [26]. **IP Addressing:** Preferably, a multi-tenant network allows a tenant to design the VN abstraction where the tenant acts as the sole occupant of the physical network (PN). This signifies second layer (L2) and third layer (L3) addresses must remain tenant definable. For address isolation, every VDC may create multiple subnets, where each has a personal IP address that can interfere with other VDC addresses. VM communications remain within the same VDC managed by a distinguished controller. By default, for the sake of network security, different VDCs do not allow their VMs to communicate. In such a framework, the proper way to communicate will then be achieved through L3 gateways. Likewise, VM communication in VDCs with private networks or computers on the Internet also go through those gateways. The authors of [27] presented an approach for encapsulating second layer L2 packets to send them over a scalable L2 fabric combining both the L2 and L3 layers through encapsulation simultaneously benefitting from using both characteristics. Such encapsulation provides full address space virtualization. **Self-defining Topology:** Tenants should be able to build network topologies that can deploy necessary VDC applications.