overlay networks

An Ethernet Virtual Private Network (EVPN) provides a unified control plane that solves the issues of Network Virtualization Edge (NVE) auto-discovery, tenant Media Access Control (MAC) / IP dissemination, and advanced features in a scablable way as required by Network Virtualization over Layer 3 (NVO3) networks. EVPN is a scalable solution for NVO3 networks and keeps the independence of the underlay IP Fabric, i.e., there is no need to enable Protocol Independent Multicast (PIM) in the underlay network and maintain multicast states for tenant Broadcast Domains. This document describes the use of EVPN for NVO3 networks and discusses its applicability to basic Layer 2 and Layer 3 connectivity requirements and to advanced features such as MAC Mobility, MAC Protection and Loop Protection, multihoming, Data Center Interconnect (DCI), and much more. No new EVPN procedures are introduced.

In the Split Network Virtualization Edge (Split-NVE) architecture, the functions of the NVE are split across a server and a piece of external network equipment that is called an "External NVE". The server-resident control-plane functionality resides in control software, which may be part of hypervisor or container-management software; for simplicity, this document refers to the hypervisor as the "location" of this software.

One or more control-plane protocols between a hypervisor and its associated External NVE(s) are used by the hypervisor to distribute its virtual-machine networking state to the External NVE(s) for further handling. This document illustrates the functionality required by this type of control-plane signaling protocol and outlines the high-level requirements. Virtual-machine states as well as state transitioning are summarized to help clarify the protocol requirements.

This document describes Network Virtualization over Layer 3 (NVO3) use cases that can be deployed in various data centers and serve different data-center applications.

This document presents a high-level overview architecture for building data-center Network Virtualization over Layer 3 (NVO3) networks. The architecture is given at a high level, showing the major components of an overall system. An important goal is to divide the space into individual smaller components that can be implemented independently with clear inter-component interfaces and interactions. It should be possible to build and implement individual components in isolation and have them interoperate with other independently implemented components. That way, implementers have flexibility in implementing individual components and can optimize and innovate within their respective components without requiring changes to other components.

This document describes issues associated with providing multi-tenancy in large data center networks and how these issues may be addressed using an overlay-based network virtualization approach. A key multi-tenancy requirement is traffic isolation so that one tenant's traffic is not visible to any other tenant. Another requirement is address space isolation so that different tenants can use the same address space within different virtual networks. Traffic and address space isolation is achieved by assigning one or more virtual networks to each tenant, where traffic within a virtual network can only cross into another virtual network in a controlled fashion (e.g., via a configured router and/or a security gateway). Additional functionality is required to provision virtual networks, associating a virtual machine's network interface(s) with the appropriate virtual network and maintaining that association as the virtual machine is activated, migrated, and/or deactivated. Use of an overlay-based approach enables scalable deployment on large network infrastructures.

This document provides a framework for Data Center (DC) Network Virtualization over Layer 3 (NVO3) and defines a reference model along with logical components required to design a solution.