The cool thing about OpenStack is – its tight integration with SDN solutions like OpenDaylight to keep apart network traffic, on-demand scaling and enabling centralized control on geographically distributed data centers. In this article, we will talk about a proposed SDN based architecture in which how OpenStack and OpenDaylight can be used to automate the deployment of VPN instances (Ethernet VPN in this case), centrally manage them along with regular updates network policies and enhancement in terms of scalability and response time on VPNs.
Problem with Interconnection of data centers with L2VPN
Virtual Private Network is generally used for geographically distributed data center interconnection. There were a lot of generations of VPN technologies that were introduced to address the connectivity needs between different sites. Layer -2 VPN (L2VPN) is the one that is widely used by organizations due to its flexibility and transparency. Virtual Private Lan Service (VPLS) service is used by L2VPN to connect different data centers. The main advantage of VPLS is that it can extend the VLAN to data centers. But VPLS has its own barriers in terms of redundancy, scalability, flexibility, and limited forwarding policies. However, Internet Service Providers (ISPs) use Multiprotocol Label Switching (MPLS) for data center interconnection because of its flexibility and ease in deployment. That triggers the necessity to have VPN technology designed for MPLS. This is where Ethernet VPN (EVPN) comes in, that address concerns and challenges associated with using VPN with MPLS. EVPN simple enables an L2 VPN connection over MPLS.
The core problem with EVPN was with manual configuration and management of EPVN instances which can cause huge time consumption, error-prone configuration and high OPEX.
An SDN Based Solution
To address the problem, SDN based architecture was proposed by researchers and engineers from Karlstd University and Ericsson. It utilized OpenDaylight SDN controller and OpenStack for automated remote deployment and automation of EVPN related tasks.
The offered solution in this paper mainly reduces two existing limitations. One is flexible network management automation and other is control plane complexity of MPLS based VPN and provision of flexibility for adding new network changes.
Before we dive into the architecture, let’s talk about how EVPN is a key technology for this solution to run EVPN dynamically on MPLS. EVPN uses MP-BGP in its control plane as a signaling method to broadcast addresses that removes the need of traditional flood-and-learn in the data plane. In EVPN, the control and data plane are abstracted and separated. That allows MPLS and Provider Edge Backbone Bridge to be used together with the EVPN control plane.
The above architecture depicts the model-driven network management and automation of EVPN instances. In this model a YANG data modeling language is used to define services and configurations, represent state data and process notifications. A configuration data defined in YANG file transmitted to network devices. NETCONF protocol is used to for transmission of configuration along with installation, deletion, and manipulation of configuration of network devices. Transmitted messages are encoded in XML file. NETCONF admin help data to pass through, validate the configuration and after successful execution admin commit changes to network devices. SDN controller leverages the NETCONF for automating the configuration of EVIs on provider edge routers.
Let’s understand the role of key components in the architecture
OpenStack: It is used as a central cloud platform to orchestrate the management of EVPNs using SDN controller. OpenStack Neutron project API is used to communicate with ODL SDN controller to manage EVPN instances attached in network.
OpenDaylight SDN Controller: It is the core element of this architecture which extends the Multiprotocol Border Gatway Protocol (MP-BGP) inside OpenDaylight controller with MP-BGP control plane (EVPN instances on the provider edge/data center) and the VPNService inside the OpenDaylight controller that automates EVPN configuration using YANG and NETCONF. This bypasses the slow and error-prone tasks of manual EVPN configuration.
Open vSwtich (OVS): This switch sits inside OpenStack compute nodes. It is used to isolate the traffic among different VMs and connects them to the physical network.
Provider Edge (PE) routers: The PE acts as a middleware for the data centers and supports EVPN and MP-BGP extensions as well as NETCONF and YANG.
Above architecture solution is evaluated. You can refer to the paper for test results here.
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