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• Bootstraps OVS and "br-int" interface in a compute node to be controlled by ONOS and CORD-VTN properly
• Provides a basic connectivity among all VMs in the same service(i.e. same Neutron network).
• Provides an external connectivity to a VM with public type of service 's network.
• Provides a local management connectivity, which is a limited connection between a VM and compute node where the VM is running.
• Provides a service dependency between two services. It guarantees forwarding all traffics from 'service A', which is tenant service, is forwarded to one of the VM of 'service B', which is provider service. The selection of one VM in the provider service is based on simple hash, and it provides a simple load balancing. 
• Provides WAN and LAN connectivities for vSG.

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Here's a brief explanation of how CORD-VTN works to provision for provisioning a virtual network in a data plane.

• nova-compute agent in a compute node creates a VM upon request, and also creates and attaches “tap” interface connected to the VM’s vNIC to “br-int” bridge. It’s all done by nova-compute agent and Hypervisor for example KVM.
• ONOS and CORD-VTN application detects a new port on "br-int".
• CORD-VTN asks about the new port with port name(it contains port UUID) to Neutron. The information from Neutron includes IP and MAC address of the VM associated to the port.
• CORD-VTN injects a new host to ONOS with the information and then populates some flows rules into the “br-int” for ARP and DHCP proxy as well as the basic tenant network connectivity. And also registers static DHCP lease for the IP and MAC pair to ONOS DHCP application which plays a role as a DHCP server.
• The VM must have an interface with the MAC address that Neutron assigns, and it's all OpenStack's responsibility. If the VM sends a DHCP request, the request would be forwarded to ONOS by the rule installed in "br-int", and then the DHCP application gets the request and looks up its static lease table and replies with the correct IP address.
• When the VM sends a packet to the other VMs in the same network, it is forwarded to the right compute node and port by the flow rules. If the destination VM is in a different compute node with the source, the packet would be encapsulated with VXLAN.

[TODO: adds pipeline diagram]

OpenStack Settings

You can find various setups and ways to build OpenStack from the Internet. Note that instructions described here include important configurations only to use CORD VTN service. All the other settings are completely up to your environment.

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