Generic Protocol Extension for VXLAN
draft-ietf-nvo3-vxlan-gpe-09

Document Type Active Internet-Draft (nvo3 WG)
Last updated 2019-12-05
Replaces draft-quinn-vxlan-gpe
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Network Working Group                                      F. Maino, Ed.
Internet-Draft                                             Cisco Systems
Intended status: Informational                           L. Kreeger, Ed.
Expires: June 7, 2020                                             Arrcus
                                                           U. Elzur, Ed.
                                                                   Intel
                                                        December 5, 2019

                  Generic Protocol Extension for VXLAN
                      draft-ietf-nvo3-vxlan-gpe-09

Abstract

   This draft describes extending Virtual eXtensible Local Area Network
   (VXLAN), via changes to the VXLAN header, with four new capabilities:
   support for multi-protocol encapsulation, support for operations,
   administration and maintenance (OAM) signaling, support for ingress-
   replicated BUM Traffic (i.e.  Broadcast, Unknown unicast, or
   Multicast), and explicit versioning.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 7, 2020.

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Copyright Notice

   Copyright (c) 2019 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
   (https://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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  VXLAN Without Protocol Extension  . . . . . . . . . . . . . .   3
   3.  Generic Protocol Extension for VXLAN (VXLAN GPE)  . . . . . .   4
     3.1.  VXLAN GPE Header  . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Multi Protocol Support  . . . . . . . . . . . . . . . . .   5
     3.3.  Replicated BUM Traffic  . . . . . . . . . . . . . . . . .   7
     3.4.  OAM Support . . . . . . . . . . . . . . . . . . . . . . .   7
     3.5.  Version Bits  . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Outer Encapsulations  . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Inner VLAN Tag Handling . . . . . . . . . . . . . . . . .  11
     4.2.  Fragmentation Considerations  . . . . . . . . . . . . . .  11
   5.  Implementation and Deployment Considerations  . . . . . . . .  12
     5.1.  Applicability Statement . . . . . . . . . . . . . . . . .  12
     5.2.  Congestion Control Functionality  . . . . . . . . . . . .  12
     5.3.  UDP Checksum  . . . . . . . . . . . . . . . . . . . . . .  13
       5.3.1.  UDP Zero Checksum Handling with IPv6  . . . . . . . .  13
   6.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .  15
     6.1.  VXLAN VTEP to VXLAN GPE VTEP  . . . . . . . . . . . . . .  15
     6.2.  VXLAN GPE VTEP to VXLAN VTEP  . . . . . . . . . . . . . .  15
     6.3.  VXLAN GPE UDP Ports . . . . . . . . . . . . . . . . . . .  15
     6.4.  VXLAN GPE and Encapsulated IP Header Fields . . . . . . .  15
   7.  VXLAN GPE Examples  . . . . . . . . . . . . . . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     11.1.  UDP Port . . . . . . . . . . . . . . . . . . . . . . . .  19
     11.2.  VXLAN GPE Next Protocol  . . . . . . . . . . . . . . . .  19
     11.3.  VXLAN GPE Flag and Reserved Bits . . . . . . . . . . . .  19
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  20

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     12.2.  Informative References . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Virtual eXtensible Local Area Network VXLAN [RFC7348] defines an
   encapsulation format that encapsulates Ethernet frames in an outer
   UDP/IP transport.  As data centers evolve, the need to carry other
   protocols encapsulated in an IP packet is required, as well as the
   need to provide increased visibility and diagnostic capabilities
   within the overlay.  The VXLAN header does not specify the protocol
   being encapsulated and therefore is currently limited to
   encapsulating only Ethernet frame payload, nor does it provide the
   ability to define OAM protocols.  In addition, [RFC6335] requires
   that new transports not use transport layer port numbers to identify
   tunnel payload, rather it encourages encapsulations to use their own
   identifiers for this purpose.  VXLAN GPE is intended to extend the
   existing VXLAN protocol to provide protocol typing, OAM, and
   versioning capabilities.

   The Version and OAM bits are introduced in Section 3, and the choice
   of location for these fields is driven by minimizing the impact on
   existing deployed hardware.

   In order to facilitate deployments of VXLAN GPE with hardware
   currently deployed to support VXLAN, changes from legacy VXLAN have
   been kept to a minimum.  Section 6 provides a detailed discussion
   about how VXLAN GPE addresses the requirement for backward
   compatibility with VXLAN.

   The capabilities of the VXLAN-GPE protocol can be extended by
   defining next protocol "shim" headers that are used to implement new
   data plane functions.  For example, Group-Based Policy (GBP) or In-
   situ Operations, Administration, and Maintenance (IOAM) metadata
   functionalities can be added as specified in
   [I-D.lemon-vxlan-lisp-gpe-gbp] and
   [I-D.brockners-ippm-ioam-vxlan-gpe].

2.  VXLAN Without Protocol Extension

   VXLAN provides a method of creating multi-tenant overlay networks by
   encapsulating packets in IP/UDP along with a header containing a
   network identifier which is used to isolate tenant traffic in each
   overlay network from each other.  This allows the overlay networks to
   run over an existing IP network.

   Through this encapsulation, VXLAN creates stateless tunnels between
   VXLAN Tunnel End Points (VTEPs) which are responsible for adding/

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   removing the IP/UDP/VXLAN headers and providing tenant traffic
   isolation based on the VXLAN Network Identifier (VNI).  Tenant
   systems are unaware that their networking service is being provided
   by an overlay.

   When encapsulating packets, a VTEP must know the IP address of the
   proper remote VTEP at the far end of the tunnel that can deliver the
   inner packet to the Tenant System corresponding to the inner
   destination address.  The control plane used to distribute inner to
   outer mappings is out of the scope of this document.

   The VXLAN Network Identifier (VNI) provides scoping for the addresses
   in the header of the encapsulated PDU.  If the encapsulated packet is
   an Ethernet frame, this means the Ethernet MAC addresses are only
   unique within a given VNI and may overlap with MAC addresses within a
   different VNI.  If the encapsulated packet is an IP packet, this
   means the IP addresses are only unique within that VNI.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|R|R|I|R|R|R|            Reserved                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 1: VXLAN Header

3.  Generic Protocol Extension for VXLAN (VXLAN GPE)

3.1.  VXLAN GPE Header

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|Ver|I|P|B|O|       Reserved                |Next Protocol  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 2: VXLAN GPE Header

   Flags (8 bits):  The first 8 bits of the header are the flag field.
      The bits designated "R" above are reserved flags.  These MUST be
      set to zero on transmission and ignored on receipt.

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   Version (Ver):  Indicates VXLAN GPE protocol version.  The initial
      version is 0.  If a receiver does not support the version
      indicated it MUST drop the packet.

   Instance Bit (I bit):  The I bit MUST be set to indicate a valid VNI.

   Next Protocol Bit (P bit):  The P bit is set to indicate that the
      Next Protocol field is present.

   BUM Traffic Bit (B bit):  The B bit is set to indicate that this is
      ingress-replicated BUM Traffic (ie, Broadcast, Unknown unicast, or
      Multicast).

   OAM Flag Bit (O bit):  The O bit is set to indicate that the packet
      is an OAM packet.

   Next Protocol:  This 8 bit field indicates the protocol header
      immediately following the VXLAN GPE header.

   VNI:  This 24 bit field identifies the VXLAN overlay network the
      inner packet belongs to.  Inner packets belonging to different
      VNIs cannot communicate with each other (unless explicitly allowed
      by policy).

   Reserved:  Reserved fields MUST be set to zero on transmission and
      ignored on receipt.

3.2.  Multi Protocol Support

   This draft defines the following two changes to the VXLAN header in
   order to support multi-protocol encapsulation:

   P Bit:  Flag bit 5 is defined as the Next Protocol bit.  The P bit
      MUST be set to 1 to indicate the presence of the 8 bit next
      protocol field.

      When UDP dest port=4790, P = 0 the "Next Protocol" field must be
      set to zero and the payload MUST be ETHERNET(L2) as defined by
      [RFC7348].

      Flag bit 5 was chosen as the P bit because this flag bit is
      currently reserved in VXLAN.

   Next Protocol Field:  The lower 8 bits of the first word are used to
      carry a next protocol.  This next protocol field contains the
      protocol of the encapsulated payload packet.  A new protocol
      registry will be requested from IANA, see section 10.2.

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      This draft defines the following Next Protocol values:

      0x01 :  IPv4

      0x02 :  IPv6

      0x03 :  Ethernet

      0x04 :  Network Service Header [RFC8300]

      0x05 to 0x7F:  Unassigned.

      0x80 to 0xFF:  Unassigned (shim headers).

   Next protocol values from Ox80 to 0xFF are assigned to protocols
   encoded as generic "shim" headers.  All shim protocols MUST use the
   header structure in Figure 3, which includes a Type, a Lenght, and a
   Next Protocol field.  When a shim header is used with other protocols
   identified by next protocol values from 0x0 to 0x7F, the shim header
   MUST come before the further protocol, and the next header of the
   shim will indicate which protocol follows the shim header.

   Shim headers can be used to incrementally deploy new GPE features
   without updating the implementation of each transit node between two
   tunnel endpoints, and without punting the packet with shim headers of
   unknown type to the 'slow' path.  Transit nodes that are not aware of
   a given shim header type MUST ignore that shim header and proceed to
   parse the next protocol.

   VTEP implementations can keep the processing of known shim headers in
   the 'fast' path (typically an ASIC), while punting the processing of
   the remaining new GPE features to the 'slow' path.

   Shim protocols MUST have the first 32 bits defined as:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |   Reserved    | Next Protocol |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                    Protocol Specific Fields                   ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 3: Shim Header

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   Where:

   Type:  This field MAY be used to identify different messages of this
      protocol.

   Length:  The length, in in 4-octet units, of this protocol message
      not including the first 4 octects.

   Reserved:  The use of this field is reserved to the protocol defined
      in this message.

   Next Protocol Field:  This next protocol field contains the protocol
      of the encapsulated payload.  The protocol registry will be
      requested from IANA as per section 10.2.

3.3.  Replicated BUM Traffic

   Flag bit 6 is defined as the B bit.  When the B bit is set to 1, the
   packet is marked as an an ingress-replicated BUM Traffic (i.e.
   Broadcast, Unknown unicast, or Multicast) to help egress VTEP to
   differentiate between known and unknown unicast.  The details of
   using the B bit are out of scope for this document, but please see
   [RFC8365] for an example in the EVPN context.  As with the P-bit, bit
   6 is currently a reserved flag in VXLAN.

3.4.  OAM Support

   Flag bit 7 is defined as the O bit.  When the O bit is set to 1, the
   packet is an OAM packet and OAM processing MUST occur.  Other header
   fields including Next Protocol MUST adhere to the definitions in
   Section 3.  The OAM protocol details are out of scope for this
   document.  As with the P-bit, bit 7 is currently a reserved flag in
   VXLAN.

3.5.  Version Bits

   VXLAN GPE bits 2 and 3 are defined as version bits.  These bits are
   reserved in VXLAN.  The version field is used to ensure backward
   compatibility going forward with future VXLAN GPE updates.

   The initial version for VXLAN GPE is 0.

4.  Outer Encapsulations

   In addition to the VXLAN GPE header, the packet is further
   encapsulated in UDP and IP.  Data centers based on Ethernet, will
   then send this IP packet over Ethernet.

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   Outer UDP Header:

   Destination UDP Port: IANA has assigned the value 4790 for the VXLAN
   GPE UDP port.  This well-known destination port is used when sending
   VXLAN GPE encapsulated packets.

   Source UDP Port: The source UDP port is used as entropy for devices
   forwarding encapsulated packets across the underlay (ECMP for IP
   routers, or load splitting for link aggregation by bridges).  Tenant
   traffic flows should all use the same source UDP port to lower the
   chances of packet reordering by the underlay for a given flow.  It is
   recommended for VTEPs to generate this port number using a hash of
   the inner packet headers.  Implementations MAY use the entire 16 bit
   source UDP port for entropy.

   UDP Checksum: see Section 5.3 for considerations related to UDP
   Checksum processing.

   Outer IP Header:

   This is the header used by the underlay network to deliver packets
   between VTEPs.  The destination IP address can be a unicast or a
   multicast IP address.  The source IP address must be the source VTEP
   IP address which can be used to return tenant packets to the tenant
   system source address within the inner packet header.

   When the outer IP header is IPv4, VTEPs MUST set the DF bit.

   Outer Ethernet Header:

   Most data centers networks are built on Ethernet.  Assuming the outer
   IP packet is being sent across Ethernet, there will be an Ethernet
   header used to deliver the IP packet to the next hop, which could be
   the destination VTEP or be a router used to forward the IP packet
   towards the destination VTEP.  If VLANs are in use within the data
   center, then this Ethernet header would also contain a VLAN tag.

   The following figures show the entire stack of protocol headers that
   would be seen on an Ethernet link carrying encapsulated packets from
   a VTEP across the underlay network for both IPv4 and IPv6 based
   underlay networks.

    0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

   Outer Ethernet Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Outer Destination MAC Address                     |

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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Outer Destination MAC Address | Outer Source MAC Address      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Outer Source MAC Address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Opt Ethertype = C-Tag 802.1Q  |     Outer VLAN Tag            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Ethertype = 0x0800            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Outer IPv4 Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version|  IHL  |Type of Service|          Total Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Identification        |Flags|      Fragment Offset    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Time to Live |Protocl=17(UDP)|   Header Checksum             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Outer Source IPv4 Address               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Outer Destination IPv4 Address              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Outer UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Source Port         |       Dest Port = 4790        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           UDP Length          |        UDP Checksum           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   VXLAN GPE Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|Ver|I|P|R|O|       Reserved                |Next Protocol  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Payload:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Depends on VXLAN GPE Next Protocol field above.          |
   |    Note that if the payload is Ethernet, then the original    |
   |    Ethernet Frame's FCS is not included.                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Frame Check Sequence:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   New FCS (Frame Check Sequence) for Outer Ethernet Frame     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 4: Outer Headers for VXLAN GPE over IPv4

    0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

   Outer Ethernet Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Outer Destination MAC Address                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Outer Destination MAC Address | Outer Source MAC Address      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Outer Source MAC Address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Opt Ethertype = C-Tag 802.1Q  |     Outer VLAN Tag            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Ethertype = 0x86DD            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Outer IPv6 Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Traffic Class |           Flow Label                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        | NxtHdr=17(UDP)|   Hop Limit   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                     Outer Source IPv6 Address                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                  Outer Destination IPv6 Address               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Outer UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   |           Source Port         |       Dest Port = 4790        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           UDP Length          |        UDP Checksum           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   VXLAN GPE Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|Ver|I|P|R|O|       Reserved                |Next Protocol  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Payload:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Depends on VXLAN GPE Next Protocol field above.          |
   |    Note that if the payload is Ethernet, then the original    |
   |    Ethernet Frame's FCS is not included.                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Frame Check Sequence:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   New FCS (Frame Check Sequence) for Outer Ethernet Frame     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5: Outer Headers for VXLAN GPE over IPv6

4.1.  Inner VLAN Tag Handling

   If the inner packet (as indicated by the VXLAN GPE Next Protocol
   field) is an Ethernet frame, it is recommended that it does not
   contain a VLAN tag.  In the most common scenarios, the tenant VLAN
   tag is translated into a VXLAN Network Identifier.  In these
   scenarios, VTEPs should never send an inner Ethernet frame with a
   VLAN tag, and a VTEP performing decapsulation should discard any
   inner frames received with a VLAN tag.  However, if the VTEPs are
   specifically configured to support it for a specific VXLAN Network
   Identifier, a VTEP may support transparent transport of the inner
   VLAN tag between all tenant systems on that VNI.  The VTEP never
   looks at the value of the inner VLAN tag, but simply passes it across
   the underlay.

4.2.  Fragmentation Considerations

   VTEPs MUST never fragment an encapsulated VXLAN GPE packet, and when
   the outer IP header is IPv4, VTEPs MUST set the DF bit in the outer
   IPv4 header.  It is recommended that the underlay network be
   configured to carry an MTU at least large enough to accommodate the
   added encapsulation headers.  It is recommended that VTEPs perform

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   Path MTU discovery [RFC1191] [RFC1981] to determine if the underlay
   network can carry the encapsulated payload packet.

5.  Implementation and Deployment Considerations

5.1.  Applicability Statement

   VXLAN-GPE conforms, as an UDP-based encapsulation protocol, to the
   UDP usage guidelines as specified in [RFC8085].  The applicability of
   these guidelines are dependent on the underlay IP network and the
   nature of the encapsulated payload.

   [RFC8085] outlines two applicability scenarios for UDP applications,
   1) general Internet and 2) controlled environment.  The controlled
   environment means a single administrative domain or adjacent set of
   cooperating domains.  A network in a controlled environment can be
   managed to operate under certain conditions whereas in general
   Internet this cannot be done.  Hence requirements for a tunnel
   protocol operating under a controlled environment can be less
   restrictive than the requirements of general internet.

   VXLAN-GPE is intended to be deployed in a data center network
   environment operated by a single operator or adjacent set of
   cooperating network operators that fits with the definition of
   controlled environments in [RFC8085].

   For the purpose of this document, a traffic-managed controlled
   environment (TMCE), outlined in [RFC8086], is defined as an IP
   network that is traffic-engineered and/or otherwise managed (e.g.,
   via use of traffic rate limiters) to avoid congestion.  Significant
   portions of text in this Section are based on [RFC8086].

   It is the responsibility of the network operators to ensure that the
   guidelines/requirements in this section are followed as applicable to
   their VXLAN-GPE deployments

5.2.  Congestion Control Functionality

   VXLAN-GPE does not natively provide congestion control functionality
   and relies on the payload protocol traffic for congestion control.
   As such VXLAN-GPE MUST be used with congestion controlled traffic or
   within a network that is traffic managed to avoid congestion (TMCE).
   An operator of a traffic managed network (TMCE) may avoid congestion
   by careful provisioning of their networks, rate-limiting of user data
   traffic and traffic engineering according to path capacity.

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5.3.  UDP Checksum

   In order to provide integrity of VXLAN-GPE headers and payload, for
   example to avoid mis-delivery of payload to different tenant systems
   in case of data corruption, outer UDP checksum SHOULD be used with
   VXLAN-GPE when transported over IPv4.  The UDP checksum provides a
   statistical guarantee that a payload was not corrupted in transit.
   These integrity checks are not strong from a coding or cryptographic
   perspective and are not designed to detect physical-layer errors or
   malicious modification of the datagram (see Section 3.4 of
   [RFC8085]).  In deployments where such a risk exists, an operator
   SHOULD use additional data integrity mechanisms such as offered by
   IPSec.

   An operator MAY choose to disable UDP checksum and use zero checksum
   if VXLAN-GPE packet integrity is provided by other data integrity
   mechanisms such as IPsec or additional checksums or if one of the
   conditions in Section 5.3.1 a, b, c are met.

   By default, UDP checksum MUST be used when VXLAN-GPE is transported
   over IPv6.  A tunnel endpoint MAY be configured for use with zero UDP
   checksum if additional requirements in Section 5.3.1 are met.

5.3.1.  UDP Zero Checksum Handling with IPv6

   When VXLAN-GPE is used over IPv6, UDP checksum is used to protect
   IPv6 headers, UDP headers and VXLAN-GPE headers and payload from
   potential data corruption.  As such by default VXLAN-GPE MUST use UDP
   checksum when transported over IPv6.  An operator MAY choose to
   configure to operate with zero UDP checksum if operating in a traffic
   managed controlled environment as stated in Section 5.1 if one of the
   following conditions are met:

   a.  It is known that the packet corruption is exceptionally unlikely
       (perhaps based on knowledge of equipment types in their underlay
       network) and the operator is willing to take a risk of undetected
       packet corruption

   b.  It is judged through observational measurements (perhaps through
       historic or current traffic flows that use non zero checksum)
       that the level of packet corruption is tolerably low and where
       the operator is willing to take the risk of undetected corruption

   c.  VXLAN-GPE payload is carrying applications that are tolerant of
       misdelivered or corrupted packets (perhaps through higher layer
       checksum validation and/or reliability through retransmission)

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   In addition VXLAN-GPE tunnel implementations using Zero UDP checksum
   MUST meet the following requirements:

   1.  Use of UDP checksum over IPv6 MUST be the default configuration
       for all VXLAN-GPE tunnels

   2.  If VXLAN-GPE is used with zero UDP checksum over IPv6 then such
       VTEP implementation MUST meet all the requirements specified in
       section 4 of [RFC6936] and requirements 1 as specified in section
       5 of [RFC6936]

   3.  The VTEP that decapsulates the packet SHOULD check the source and
       destination IPv6 addresses are valid for the VXLAN-GPE tunnel
       that is configured to receive Zero UDP checksum and discard other
       packets for which such check fails

   4.  The VTEP that encapsulates the packet MAY use different IPv6
       source addresses for each VXLAN-GPE tunnel that uses Zero UDP
       checksum mode in order to strengthen the decapsulator's check of
       the IPv6 source address (i.e the same IPv6 source address is not
       to be used with more than one IPv6 destination address,
       irrespective of whether that destination address is a unicast or
       multicast address).  When this is not possible, it is RECOMMENDED
       to use each source address for as few VXLAN-GPE tunnels that use
       zero UDP checksum as is feasible

   5.  Measures SHOULD be taken to prevent VXLAN-GPE traffic over IPv6
       with zero UDP checksum from escaping into the general Internet.
       Examples of such measures include employing packet filters at the
       gateways or edge of a VXLAN-GPE network, and/or keeping logical
       or physical separation of VXLAN network from networks carrying
       General Internet

   The above requirements do not change either the requirements
   specified in [RFC2460] as modified by [RFC6935] or the requirements
   specified in [RFC6936].

   The requirement to check the source IPv6 address in addition to the
   destination IPv6 address, plus the recommendation against reuse of
   source IPv6 addresses among VXLAN-GPE tunnels collectively provide
   some mitigation for the absence of UDP checksum coverage of the IPv6
   header.  A traffic-managed controlled environment that satisfies at
   least one of three conditions listed at the beginning of this section
   provides additional assurance.

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6.  Backward Compatibility

6.1.  VXLAN VTEP to VXLAN GPE VTEP

   A VXLAN VTEP conforms to VXLAN frame format and uses UDP destination
   port 4789 when sending traffic to VXLAN GPE VTEP.  As per VXLAN,
   reserved bits 5 and 7, VXLAN GPE P and O-bits respectively must be
   set to zero.  The remaining reserved bits must be zero, including the
   VXLAN GPE version field, bits 2 and 3.  The encapsulated payload MUST
   be Ethernet.

6.2.  VXLAN GPE VTEP to VXLAN VTEP

   A VXLAN GPE VTEP MUST NOT encapsulate non-Ethernet frames to a VXLAN
   VTEP.  When encapsulating Ethernet frames to a VXLAN VTEP, the VXLAN
   GPE VTEP MUST conform to VXLAN frame format and hence will set the P
   bit to 0, the Next Protocol to 0 and use UDP destination port 4789.
   A VXLAN GPE VTEP MUST also set O = 0 and Ver = 0 when encapsulating
   Ethernet frames to VXLAN VTEP.  The receiving VXLAN VTEP will treat
   this packet as a VXLAN packet.

   A method for determining the capabilities of a VXLAN VTEP (GPE or
   non-GPE) is out of the scope of this draft.

6.3.  VXLAN GPE UDP Ports

   VXLAN GPE uses a IANA assigned UDP destination port, 4790, when
   sending traffic to VXLAN GPE VTEPs.

6.4.  VXLAN GPE and Encapsulated IP Header Fields

   When encapsulating IP (including over Ethernet) packets [RFC2983]
   provides guidance for mapping DSCP between inner and outer IP
   headers.  The Pipe model typically fits better Network
   virtualization.  The DSCP value on the tunnel header is set based on
   a policy (which may be a fixed value, one based on the inner traffic
   class, or some other mechanism for grouping traffic).  Some aspects
   of the Uniform model (which treats the inner and outer DSCP value as
   a single field by copying on ingress and egress) may also apply, such
   as the ability to remark the inner header on tunnel egress based on
   transit marking.  However, the Uniform model is not conceptually
   consistent with network virtualization, which seeks to provide strong
   isolation between encapsulated traffic and the physical network.

   [RFC6040] describes the mechanism for exposing ECN capabilities on IP
   tunnels and propagating congestion markers to the inner packets.
   This behavior MUST be followed for IP packets encapsulated in VXLAN-
   GPE.

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   Though Uniform or Pipe models could be used for TTL (or Hop Limit in
   case of IPv6) handling when tunneling IP packets, Pipe model is more
   aligned with network virtualization.  [RFC2003] provides guidance on
   handling TTL between inner IP header and outer IP tunnels; this model
   is more aligned with the Pipe model and is recommended for use with
   VXLAN-GPE for network virtualization applications.

7.  VXLAN GPE Examples

   This section provides three examples of protocols encapsulated using
   the Generic Protocol Extension for VXLAN described in this document.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|0|0|I|1|R|0|       Reserved                |    NP = IPv4  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Original IPv4 Packet                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 6: IPv4 and VXLAN GPE

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|0|0|I|1|R|0|       Reserved                |  NP = IPv6    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Original IPv6 Packet                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 7: IPv6 and VXLAN GPE

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|0|0|I|1|R|0|       Reserved                |NP = Ethernet  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Original Ethernet Frame                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 8: Ethernet and VXLAN GPE

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8.  Security Considerations

   VXLAN-GPE encapsulation does not affect security for the payload
   protocol.  The security considerations for VXLAN applies to VXLAN-
   GPE, see [RFC7348].

   When crossing an untrusted link, such as the public Internet, IPsec
   [RFC4301] may be used to provide authentication and/or encryption of
   the IP packets formed as part of VXLAN-GPE encapsulation.

   Operators have to make an assessment based on their network
   environment and determine the risks that are applicable to their
   specific environment and use appropriate mitigation approaches as
   applicable.

9.  Contributors

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   Paul Quinn
   Cisco Systems
   paulq@cisco.com

   Rajeev Manur
   Broadcom
   rmanur@broadcom.com

   Michael Smith
   Cisco Systems
   michsmit@cisco.com

   Darrel Lewis
   Cisco Systems
   darlewis@cisco.com

   Puneet Agarwal
   Innovium, Inc
   puneet@acm.org

   Lucy Yong
   Huawei USA
   lucy.yong@huawei.com

   Xiaohu Xu
   Huawei Technologies
   xuxiaohu@huawei.com

   Pankaj Garg
   Microsoft
   pankajg@microsoft.com

   David Melman
   Marvell
   davidme@marvell.com

   Jennifer Lemon
   Broadcom Limited
   jennifer.lemon@broadcom.com

10.  Acknowledgments

   A special thank you goes to Dino Farinacci for his guidance and
   detailed review.

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11.  IANA Considerations

11.1.  UDP Port

   UDP 4790 port has been assigned by IANA for VXLAN GPE.

11.2.  VXLAN GPE Next Protocol

   IANA is requested to set up a registry of "Next Protocol".  These are
   8-bit values.  Next Protocol values in the table below are defined in
   this draft.  New values are assigned via Standards Action [RFC5226].

       +---------------+---------------------------+---------------+
       | Next Protocol | Description               | Reference     |
       +---------------+---------------------------+---------------+
       | 0x0           | Reserved                  | This Document |
       | 0x1           | IPv4                      | This Document |
       | 0x2           | IPv6                      | This Document |
       | 0x3           | Ethernet                  | This Document |
       | 0x4           | NSH                       | This Document |
       | 0x05..0x7F    | Unassigned                |               |
       | 0x80..0xFF    | Unassigned (shim headers) |               |
       +---------------+---------------------------+---------------+

11.3.  VXLAN GPE Flag and Reserved Bits

   There are ten flag bits at the beginning of the VXLAN GPE header,
   followed by 16 reserved bits and an 8-bit reserved field at the end
   of the header.  New bits are assigned via Standards Action [RFC5226].

      Bits 0-1 - Reserve6

      Bits 2-3 - Version

      Bit 4 - Instance ID (I bit)

      Bit 5 - Next Protocol (P bit)

      Bit 6 - Reserved

      Bit 7 - OAM (O bit)

      Bit 8-23 - Reserved

      Bits 24-31 in the 2nd Word -- Reserved

   Reserved bits/fields MUST be set to 0 by the sender and ignored by
   the receiver.

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12.  References

12.1.  Normative References

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,
              <https://www.rfc-editor.org/info/rfc1191>.

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
              1996, <https://www.rfc-editor.org/info/rfc1981>.

   [RFC2003]  Perkins, C., "IP Encapsulation within IP", RFC 2003,
              DOI 10.17487/RFC2003, October 1996,
              <https://www.rfc-editor.org/info/rfc2003>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <https://www.rfc-editor.org/info/rfc2460>.

   [RFC2983]  Black, D., "Differentiated Services and Tunnels",
              RFC 2983, DOI 10.17487/RFC2983, October 2000,
              <https://www.rfc-editor.org/info/rfc2983>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC6040]  Briscoe, B., "Tunnelling of Explicit Congestion
              Notification", RFC 6040, DOI 10.17487/RFC6040, November
              2010, <https://www.rfc-editor.org/info/rfc6040>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

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   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935,
              DOI 10.17487/RFC6935, April 2013,
              <https://www.rfc-editor.org/info/rfc6935>.

   [RFC6936]  Fairhurst, G. and M. Westerlund, "Applicability Statement
              for the Use of IPv6 UDP Datagrams with Zero Checksums",
              RFC 6936, DOI 10.17487/RFC6936, April 2013,
              <https://www.rfc-editor.org/info/rfc6936>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/info/rfc7348>.

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <https://www.rfc-editor.org/info/rfc8085>.

   [RFC8086]  Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
              in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
              March 2017, <https://www.rfc-editor.org/info/rfc8086>.

   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,
              <https://www.rfc-editor.org/info/rfc8300>.

   [RFC8365]  Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
              Uttaro, J., and W. Henderickx, "A Network Virtualization
              Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
              DOI 10.17487/RFC8365, March 2018,
              <https://www.rfc-editor.org/info/rfc8365>.

12.2.  Informative References

   [I-D.brockners-ippm-ioam-vxlan-gpe]
              Brockners, F., Bhandari, S., Govindan, V., Pignataro, C.,
              Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Kfir, A.,
              Gafni, B., Lapukhov, P., and M. Spiegel, "VXLAN-GPE
              Encapsulation for In-situ OAM Data", draft-brockners-ippm-
              ioam-vxlan-gpe-03 (work in progress), November 2019.

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   [I-D.lemon-vxlan-lisp-gpe-gbp]
              Lemon, J., Maino, F., Smith, M., and A. Isaac, "Group
              Policy Encoding with VXLAN-GPE and LISP-GPE", draft-lemon-
              vxlan-lisp-gpe-gbp-02 (work in progress), April 2019.

Authors' Addresses

   Fabio Maino (Editor)
   Cisco Systems

   Email: fmaino@cisco.com

   Larry Kreeger (editor)
   Arrcus

   Email: lkreeger@gmail.com

   Uri Elzur (editor)
   Intel

   Email: uri.elzur@intel.com

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