NVGRE: Network Virtualization Using Generic Routing Encapsulation
RFC 7637

Document Type RFC - Informational (September 2015; No errata)
Last updated 2015-10-14
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Independent Submission                                      P. Garg, Ed.
Request for Comments: 7637                                  Y. Wang, Ed.
Category: Informational                                        Microsoft
ISSN: 2070-1721                                           September 2015

   NVGRE: Network Virtualization Using Generic Routing Encapsulation

Abstract

   This document describes the usage of the Generic Routing
   Encapsulation (GRE) header for Network Virtualization (NVGRE) in
   multi-tenant data centers.  Network Virtualization decouples virtual
   networks and addresses from physical network infrastructure,
   providing isolation and concurrency between multiple virtual networks
   on the same physical network infrastructure.  This document also
   introduces a Network Virtualization framework to illustrate the use
   cases, but the focus is on specifying the data-plane aspect of NVGRE.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7637.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Garg & Wang                   Informational                     [Page 1]
RFC 7637                          NVGRE                   September 2015

Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology ................................................4
   2. Conventions Used in This Document ...............................4
   3. Network Virtualization Using GRE (NVGRE) ........................4
      3.1. NVGRE Endpoint .............................................5
      3.2. NVGRE Frame Format .........................................5
      3.3. Inner Tag as Defined by IEEE 802.1Q ........................8
      3.4. Reserved VSID ..............................................8
   4. NVGRE Deployment Considerations .................................9
      4.1. ECMP Support ...............................................9
      4.2. Broadcast and Multicast Traffic ............................9
      4.3. Unicast Traffic ............................................9
      4.4. IP Fragmentation ..........................................10
      4.5. Address/Policy Management and Routing .....................10
      4.6. Cross-Subnet, Cross-Premise Communication .................10
      4.7. Internet Connectivity .....................................12
      4.8. Management and Control Planes .............................12
      4.9. NVGRE-Aware Devices .......................................12
      4.10. Network Scalability with NVGRE ...........................13
   5. Security Considerations ........................................14
   6. Normative References ...........................................14
   Contributors ......................................................16
   Authors' Addresses ................................................17

1.  Introduction

   Conventional data center network designs cater to largely static
   workloads and cause fragmentation of network and server capacity [6]
   [7].  There are several issues that limit dynamic allocation and
   consolidation of capacity.  Layer 2 networks use the Rapid Spanning
   Tree Protocol (RSTP), which is designed to eliminate loops by
   blocking redundant paths.  These eliminated paths translate to wasted
   capacity and a highly oversubscribed network.  There are alternative
   approaches such as the Transparent Interconnection of Lots of Links
   (TRILL) that address this problem [13].

   The network utilization inefficiencies are exacerbated by network
   fragmentation due to the use of VLANs for broadcast isolation.  VLANs
   are used for traffic management and also as the mechanism for
   providing security and performance isolation among services belonging
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