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1. Introduction

1. Introduction​

This document specifies how Ethernet VPN (EVPN) [RFC7432] can be used as a Network Virtualization Overlay (NVO) solution and explores the various tunnel encapsulation options over IP and their impact on the EVPN control plane and procedures. In particular, the following encapsulation options are analyzed: Virtual Extensible LAN (VXLAN) [RFC7348], Network Virtualization using Generic Routing Encapsulation (NVGRE) [RFC7637], and MPLS over Generic Routing Encapsulation (GRE) [RFC4023]. This specification is also applicable to Generic Network Virtualization Encapsulation (GENEVE) [GENEVE]; however, some incremental work is required, which will be covered in a separate document [EVPN-GENEVE]. This document also specifies new multihoming procedures for split-horizon filtering and mass withdrawal. It also specifies EVPN route constructions for VXLAN/NVGRE encapsulations and Autonomous System Border Router (ASBR) procedures for multihoming of Network Virtualization Edge (NVE) devices.

In the context of this document, an NVO is a solution to address the requirements of a multi-tenant data center, especially one with virtualized hosts, e.g., Virtual Machines (VMs) or virtual workloads. The key requirements of such a solution, as described in [RFC7364], are the following:

  • Isolation of network traffic per tenant

  • Support for a large number of tenants (tens or hundreds of thousands)

  • Extension of Layer 2 (L2) connectivity among different VMs belonging to a given tenant segment (subnet) across different Points of Delivery (PoDs) within a data center or between different data centers

  • Allowing a given VM to move between different physical points of attachment within a given L2 segment

The underlay network for NVO solutions is assumed to provide IP connectivity between NVO endpoints.

This document describes how EVPN can be used as an NVO solution and explores applicability of EVPN functions and procedures. In particular, it describes the various tunnel encapsulation options for EVPN over IP and their impact on the EVPN control plane as well as procedures for two main scenarios:

(a) single-homing NVEs - when an NVE resides in the hypervisor, and

(b) multihoming NVEs - when an NVE resides in a Top-of-Rack (ToR) device.

The possible encapsulation options for EVPN overlays that are analyzed in this document are:

  • VXLAN and NVGRE

  • MPLS over GRE

Before getting into the description of the different encapsulation options for EVPN over IP, it is important to highlight the EVPN solution's main features, how those features are currently supported, and any impact that the encapsulation has on those features.

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