Study of applications and testing scenarios of Citrix SD-WAN solution

Traditional networks are no more suitable for the increasing traffic demand of the recent years. Indeed, they were based on coupling the data and the control plane in each device of the network. This approach is old and poorly flexible because it is strictly related to hardware vendors and is too much pricey nowadays. For satisfying the high bandwidth request and the switchover to cloud-based applications, the traditional approach would imply purchasing a lot of new devices, that is costly and energy-consuming. Thus, a transition towards the Software Defined Networking (SDN) is occurring. SDN is a new network paradigm that reverses the previous approach by decoupling the data and the control plane, implementing the first into the dummy switches of the network, and the second into a specialized hardware usually known as SDN controller or orchestrator. This new layout turns out to be more flexible, cost-effective and dynamic and makes the network control plane directly programmable. The current work investigates the application of SDN to wide area networks (SD-WAN), where wide area networks are massive networks whose function is to connect users at the branch or campus to applications hosted on servers in the data center. Actually, the point of interest of the thesis relies on understanding what has brought enterprises to develop this new solution. In the past, wide area networks were mainly implemented through dedicated MPLS circuits, which are expensive and require long lead times for the deployment. Typically, dedicated MPLS circuits were used to help ensure security and reliable connectivity. Nowadays, the majority of applications is developed by means of Software-as-a-service platforms on the cloud, and the old MPLS is no longer up to the job. The thesis has been realized in partnership with the Citrix vendor, with the aim to test its peculiar SD-WAN solution, its capabilities and the innovations it brings. For this purpose, many simulation scenarios have been deployed by creating a virtual network infrastructure on the Vmware EsXi platform. The simulated network involves a branch office and a head quarter, both connected to two instances of a Citrix SD-WAN appliance and communicating between them thanks to an emulator of wide area networks that mimics an MPLS circuit and an ADSL link. The tests are based on exchanges of data among the two sites while monitoring continuously the network statistics through the graphical interface of the Citrix product. The results of the experiments have highlighted which are the benefits of the new technology, starting from the application routed traffic dynamism, to the improved operational expenditures, to the simplified and programmable management and to end up in the enhanced WAN performances. To wrap up, the Citrix SD-WAN solution offers a competitive environment for the transition from traditional networks to a cloud-centric world. However, there are still some open issues to address: mobile users are completely transparent to SD-WAN devices, no true end to end quality of service is guaranteed, there is no on-site security functionality and there is still the need for qualified IT staff to deploy and maintain this technical solution.