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<front>
  <title abbrev="NVO3 Encapsulation Considerations">Network
  Virtualization Overlays over Layer 3 (NVO3) Encapsulation Considerations</title>
   <!--  The abbreviated title is required if the full title is
        longer than 39 characters -->
   <seriesInfo name="Internet-Draft"
               value="&filename;"/> name="RFC" value="9638"/>
   <author initials="S." surname="Boutros" fullname="Sami Boutros" role="editor">
     <organization>Ciena Corporation</organization>
     <address>
       <postal>
         <country>USA</country>
         <country>United States of America</country>
       </postal>
       <email>sboutros@ciena.com</email>
     </address>
   </author>
   <author fullname="Donald E. Eastlake 3rd" initials="D."
           surname="Eastlake" surname="Eastlake 3rd" role="editor">
     <organization>Futurewei Technologies</organization>
     <organization>Independent</organization>
     <address>
       <postal>
         <street>2386 Panoramic Circle</street>
         <city>Apopka</city>
         <region>Florida</region>
         <region>FL</region>
         <code>32703</code>
         <country>USA</country>
         <country>United States of America</country>
       </postal>
       <phone>+1-508-333-2270</phone>
       <email>d3e3e3@gmail.com</email>
     </address>
   </author>

   <date year="2024" month="2" day="19"/>

   <area>Routing</area>
   <workgroup>NVO3 Working Group</workgroup>
   <!-- "Internet Engineering Task Force" is fine for individual
        submissions.  If this element is not present, the default is
        "Network Working Group", which is used by the RFC Editor as a
        nod to the history of the RFC Series. -->

   <keyword></keyword>
   <!-- Multiple keywords are allowed.  Keywords are incorporated
        into HTML output files for use by search engines. --> month="September"/>

   <area>RTG</area>
   <workgroup>nvo3</workgroup>

<abstract>
  <t>The IETF Network Virtualization Overlays (NVO3) Working Group
  developed considerations for a common encapsulation that addresses
  various network virtualization overlay technical concerns.
  This document provides a record, for the benefit of the IETF community,
  of the considerations arrived at by the NVO3 Working Group starting from
  the output of an the NVO3 encapsulation design team. Design Team. These considerations
  may be helpful with future deliberations by working groups over the choice of
  encapsulation formats.</t>

  <t>There are implications of having different encapsulations in real
  environments consisting of both software and hardware
  implementations and within and spanning multiple data centers.  For
  example, OAM Operations, Administration, and Maintenance (OAM) functions such as path MTU discovery become challenging
  with multiple encapsulations along the data path.</t>

  <t>Based on these considerations, the NVO3 Working Group determined that
  Geneve
  Generic Network Virtualization Encapsulation (Geneve) with a few modifications as is the common encapsulation. This document provides more details, particularly in Section 7.</t> <xref target="Recommendations"/>.</t>
</abstract>
</front>

<!-- ____________________MIDDLE_MATTER____________________ -->

<middle>
<section>  <!-- 1. -->
  <name>Introduction</name>

<t>The NVO3 Working Group is chartered to gather requirements and
develop solutions for network virtualization data planes based on
encapsulation of virtual network traffic over an IP-based underlay
data plane.  Requirements include due consideration for OAM and
security.  Based on these requirements requirements, the WG was to select, extend,
and/or develop one or more data plane encapsulation format(s).</t> formats.</t>

<t>This led to WG drafts Internet-Drafts and an RFC describing three encapsulations as
follows:</t>

<ul>
  <li><xref target="RFC8926"/> Geneve:
  <li>"Geneve: Generic Network Virtualization
Encapsulation</li>

<li><xref target="ietf_intarea_gue"/> Generic Encapsulation" <xref target="RFC8926"/></li>
  <li>"Generic UDP Encapsulation</li>

<li><xref target="nvo3_vxlan_gpe"/> Generic Encapsulation" <xref target="I-D.ietf-intarea-gue"/></li>
  <li>"Generic Protocol Extension for VXLAN (VXLAN-GPE)</li> (VXLAN-GPE)" <xref target="I-D.ietf-nvo3-vxlan-gpe"/></li>
</ul>

<t>Discussion on the list and in face-to-face meetings identified a
number of technical problems with each of these encapsulations.
Furthermore, there was a clear consensus at the 96th IETF meeting in
Berlin that, to maximize interoperability, that the working group should progress only one data plane encapsulation. encapsulation, to maximize interoperability. In order to overcome a
deadlock on the encapsulation decision, the WG consensus was to form a
Design Team <xref target="RFC2418"/> to resolve this issue and provide
initial considerations.</t>

</section>
<section>  <!-- 2. -->
  <name>Design Team and Working Group Process</name>

<t>The Design Team was to select one of the proposed encapsulations and
enhance it to address the technical concerns.  The goals were simple evolution of
deployed networks as well as applicability to all locations in the NVO3 architecture were goals.
architecture. The Design Team was to specifically avoid selecting select a design that allows for future extensibility but is not burdensome on hardware implementations but should allow future extensibility. implementations. The selected design also needed to operate well with ICMP the Internet Control Message Protocol (ICMP) and
in Equal
  Cost Multi-Path Equal-Cost Multipath (ECMP) environments.  If further extensibility is
required, then it should be done in such a manner that it does not require the
consent of an entity outside of the IETF.</t>

  <t>The output of the Design Team was then prcoessed processed through the
  working group group, resulting in a working group consensus for this
  document.</t>

</section>
<section>  <!-- 3. -->
  <name>Terminology</name>

 <t>The
          <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
 NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
 "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>",
    "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are to be
    interpreted as described in BCP 14 BCP&nbsp;14 <xref target="RFC2119"/> <xref
    target="RFC8174"/> when, and only when, they appear in all capitals, as
    shown here.</t> here.
        </t>
</section>
<section>  <!-- 4. -->
  <name>Abbreviations
  <name>Abbreviations, Acronyms, and Acronyms</name> Definitions</name>
 <t>The following abbreviations and acronyms are used in this
 document:</t>
 <dl>
<dt>ACL </dt><dd>- Access
   <dt>ACL:</dt><dd>Access Control List</dd>

<dt>DT</dt><dd>- NVO3 encapsulation Design Team</dd>

<dt>ECMP</dt><dd>- Equal Cost Multi-Path</dd>

<dt>EVPN</dt><dd>- Ethernet
   <dt>ECMP:</dt><dd>Equal-Cost Multipath</dd>
   <dt>EVPN:</dt><dd>Ethernet VPN <xref target="RFC8365"/></dd>

<dt>Geneve</dt><dd>- Generic
   <dt>Geneve:</dt><dd>Generic Network Virtualization Encapsulation <xref target="RFC8926"/></dd>

<dt>GPE </dt><dd>- Generic
   <dt>GPE:</dt><dd>Generic Protocol Extension</dd>

<dt>GUE </dt><dd>- Generic
   <dt>GUE:</dt><dd>Generic UDP Encapsulation <xref
target="ietf_intarea_gue"/></dd>

<dt>HMAC</dt><dd>- Hash based keyed target="I-D.ietf-intarea-gue"/></dd>
   <dt>HMAC:</dt><dd>Hash-Based Message Authentication Code <xref target="RFC2104"/></dd>

<dt>IEEE</dt><dd>- Institute
   <dt>IEEE:</dt><dd>Institute for Electrical and Electronic Engineers
(www.ieee.org)</dd>

<dt>NIC</dt><dd>- Network (<eref
   brackets="angle" target="https://www.ieee.org/"/>)</dd>
   <dt>NIC:</dt><dd>Network Interface Card (refers to network interface
   hardware which that is not necessarily a discrete "card")</dd>

<dt>NSH </dt><dd>- Network
   <dt>NSH:</dt><dd>Network Service Header <xref target="RFC8300"/></dd>

<dt>NVA </dt><dd>- Network
   <dt>NVA:</dt><dd>Network Virtualization Authority</dd>

<dt>NVE </dt><dd>- Network
   <dt>NVE:</dt><dd>Network Virtual Edge (device)</dd>

<dt>NVO3</dt><dd>- Network (refers to an NVE device)</dd>
   <dt>NVO3:</dt><dd>Network Virtualization Overlays over Layer 3</dd>

<dt>OAM </dt><dd>- Operations,
   <dt>OAM:</dt><dd>Operations, Administration, and Maintenance <xref target="RFC6291"/></dd>

<dt>PWE3</dt><dd>- Pseudowire
   <dt>PWE3:</dt><dd>Pseudowire Emulation Edge to Edge</dd>

<dt>TCAM</dt><dd>- Ternary Edge-to-Edge</dd>
   <dt>TCAM:</dt><dd>Ternary Content-Addressable Memory</dd>

<dt>TLV </dt><dd>- Type, Length, and Value</dd>
   <dt>TLV:</dt><dd>Type-Length-Value</dd>
   <dt>Transit device</dt><dd>- Underlay device:</dt><dd>Refers to underlay network devices between NVE(s).</dd>

<dt>UUID</dt><dd>- Universally NVEs.</dd>
   <dt>UUID:</dt><dd>Universally Unique Identifier</dd>

<dt>VNI </dt><dd>- Virtual
   <dt>VNI:</dt><dd>Virtual Network Identifier</dd>

<dt>VXLAN</dt><dd>- Virtual
   <dt>VXLAN:</dt><dd>Virtual eXtensible LAN Local Area Network <xref target="RFC7348"/></dd>
 </dl>
</section>

<section>  <!-- 5. -->
  <name>Encapsulation Issues and Background</name>

  <t>The following subsections describe issues with current
  encapsulations as discussed by the NVO3 WG. Numerous extensions and
  options have been designed for GUE and Geneve which that may help resolve
  some of these issues issues, but these have not yet been validated by the WG.</t>

  <t>Also included are diagrams and information on the candidate
  encapsulations. These are mostly copied from other documents. Since
  each protocol is assumed to be sent over UDP, an initial UDP Header header
  is shown which that would be preceded by an IPv4 or IPv6 Header.</t> header.</t>
<section>  <!-- 5.1 -->
  <name>Geneve</name>

  <t>The Geneve packet format, taken from <xref target="RFC8926"/>, is shown in
  <xref target="GeneveHeader"/> below.</t>

<figure anchor="GeneveHeader">
  <name>Geneve Header</name>
    <artwork type="ascii-art" align="center">
      <![CDATA[ align="center"><![CDATA[
    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 UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Source Port          |    Dest Port = 6081 Geneve    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          UDP Length           |        UDP Checksum           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Geneve Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ver|  Opt Len  |O|C|    Rsvd.  |          Protocol Type        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Virtual Network Identifier (VNI)       |    Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                    Variable-Length Options                    ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ]]>
    </artwork>
]]></artwork>
</figure>

  <t>The type of payload being carried is indicated by an Ethertype
  <xref target="RFC7042"/> target="RFC9542"/> in the Protocol Type field in the Geneve
  Header;
  header; Ethernet itself is represented by Ethertype 0x6558. See
  <xref target="RFC8926"/> for details concerning UDP header
  fields. The O bit indicates an OAM packet. The Geneve C bit is the
  "Critical" bit bit, which means that the options must be processed or the
  packet discarded.</t>

  <t>Issues with Geneve <xref target="RFC8926"/> are as follows:</t>

  <ul>
    <li>Can't
    <li>Geneve can't be implemented cost-effectively in all use cases because
    variable length
    the variable-length header and order of the TLVs makes make it costly (in
    terms of number of gates) to implement in hardware.</li>

    <li>Header

    <li>The header doesn't fit into the largest commonly available parse
    buffer (256 bytes in a NIC).  Cannot justify Thus, doubling the buffer size can't be
    justified unless it is mandatory for hardware to process additional option
    fields.</li>
  </ul>

  <t>Selection

  <t>The selection of Geneve despite these issues may be the result of the
  Geneve design effort effort, assuming that the Geneve header would typically
  be delivered to a server and parsed in software.</t>

</section>
<section>  <!-- 5.2 -->
  <name>Generic UDP Encapsulation (GUE)</name>
<figure anchor="GUEHeader">
  <name>GUE Header</name>
    <artwork type="ascii-art" align="center">
      <![CDATA[ align="center"><![CDATA[
    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

UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Source port Port            |     Dest port Port = 6080 GUE      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        UDP Length             |          UDP Checksum         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

GUE Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 0 |C|   Hlen  |  Proto/ctype  |             Flags             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                  Extensions Fields (optional)                 ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ]]>
    </artwork>
]]></artwork>
</figure>

<t>The type of payload being carried is indicated by an IANA Internet protocol number in the Proto/ctype field. The GUE C bit (Control bit) indicates a
Control
control packet.</t>

<t>Issues with GUE <xref target="ietf_intarea_gue"/> target="I-D.ietf-intarea-gue"/> are as
follows:</t>

<ul>
  <li>There were a significant number of objections to GUE related to
  the complexity of its implementation in hardware, similar to those noted
  for Geneve above, such as the variable length and
  possible high maximum length of the header.</li>
</ul>

</section>
<section>  <!-- 5.3 -->
  <name>Generic Protocol Extension (GPE) for VXLAN</name>
<figure anchor="GPEHeader">
  <name>GPE Header</name>
    <artwork type="ascii-art" align="center">
      <![CDATA[ align="center"><![CDATA[
    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 UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Source Port         |     Dest Port = 4790 GPE      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           UDP Length          |           UDP Checksum        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

VXLAN-GPE Header
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|R|Ver|I|P|B|O|       Reserved                | Next Protocol |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                VXLAN              Virtual Network Identifier (VNI) |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ]]>
    </artwork>
]]></artwork>
</figure>

<t>The type of payload being carried is indicated by the Next Protocol
field using a VXLAN-GPE-specific registry. registry specific to VXLAN-GPE. The I bit indicates that
the VNI is valid. The P bit indicates that the Next Protocol field is
valid. The B bit indicates that the packet is an ingress replicated
Broadcast, Unknown Unicast, or Multicast packet. The O bit indicates
an OAM packet.</t>

<t>Issues with VXLAN-GPE <xref target="nvo3_vxlan_gpe"/> target="I-D.ietf-nvo3-vxlan-gpe"/> are as
follows:</t>

<ul>
  <li>GPE is not day-1 day one backwards compatible with VXLAN <xref
  target="RFC7348"/>.  Although the frame format is similar, it uses a
  different UDP port, so it would require changes to existing
  implementations even if the rest of the GPE frame were the
  same.</li>

  <li>GPE is insufficiently extensible. It adds a Next Protocol field
  and some flag bits to the VXLAN header but is not otherwise
  extensible.</li>

  <li>Security, e.g., of the VNI, as

  <li>As discussed in <xref target="SecExt"/>, security (e.g., of the VNI) has
  not been addressed by GPE.  Although a shim header could be added for
  security and to support other extensions, this has not been defined
  yet. More study would be needed to understand the implication of such a shim
  on offloading in NICs.</li>
</ul>

</section>
</section>

<section>  <!-- 6. -->

<section anchor="CommonEncapsulationConsiderations">
  <name>Common Encapsulation Considerations</name>

  <section>  <!-- 6.1 -->
    <name>Current Encapsulations</name>

<t>Appendix A

<t><xref target="EncapsulationComparison"/> includes a detailed comparison between the three
proposed encapsulations.  The comparison indicates several common
properties but also three major differences among the
encapsulations:</t>

<ul>
  <li>Extensibility: Geneve and GUE were defined with built-in
  extensibility, while VXLAN-GPE is not inherently extensible.  Note
  that any of the three encapsulations can be extended using the
  Network Service Header (NSH (NSH) <xref target="RFC8300"/>).</li> target="RFC8300"/>.</li>

  <li>Extension method: Geneve is extensible using Type/Length/Value Type-Length-Value
  (TLV) fields, while GUE uses a small set of possible extensions, extensions and
  a set of flags that indicate which extensions are present.</li>

  <li>Length field: Geneve and GUE include a Length field, indicating
  the length of the encapsulation header, while VXLAN-GPE does not
  include such a field. Thus Thus, it may be harder to skip the encapsulation
  header with VXLAN-GPE</li>
</ul>

  </section>
  <section>  <!-- 6.2 -->
  <section anchor="ExtensionsUseCases">
    <name>Useful Extensions Use Cases</name>

<t>Non-vendor specific extensions,

<t>Extensions that are not vendor-specific, such as TLVs, MUST <bcp14>MUST</bcp14> follow the
standardization process.  The following use cases for extensions show
that there is a strong requirement to support variable length variable-length
extensions with possible different subtypes.</t>

    <section>  <!--6.2.1 -->
      <name>Telemetry Extensions</name>

<t>In several scenarios scenarios, it is beneficial to make information available to the
operator about the path a packet took through the network or through a network
device as well as associated telemetry information available to the
operator.</t> about associated telemetry.</t>

<t>This includes not only tasks like debugging, troubleshooting, and
network planning and optimization but also policy or service level
agreement compliance checks.</t>

<t>Packet scheduling algorithms, especially for balancing traffic
across equal cost equal-cost paths or links, often leverage information contained
within the packet, such as protocol number, IP address, or MAC Message
Authentication Code (MAC) address.  Probe  Thus, probe packets would thus either need to be either sent between the
exact same endpoints with the exact same parameters, parameters or probe packets
would need to be artificially constructed as "fake" packets and
inserted along the path.  Both approaches are often not feasible from
an operational perspective because access to the end-system end system is not
feasible or the diversity of parameters and associated probe packets
to be created is simply too large.  An extension providing an in-band
telemetry mechanism <xref target="RFC9197"/> is an alternative in
those cases.</t>

    </section>
    <section anchor="SecExt"> <!-- 6.2.2 -->
      <name>Security/Integrity Extensions</name>

<t>Since the currently proposed NVO3 encapsulations do not protect
their headers, a single bit corruption in the VNI field could deliver
a packet to the wrong tenant.  Extension headers are needed to use any
sophisticated security.</t>

<t>The possibility of VNI spoofing with an NVO3 protocol is
exacerbated by using UDP.  Systems typically have no restrictions on
applications being able to send to any UDP port port, so an unprivileged
application can trivially spoof VXLAN <xref target="RFC7348"/> packets
for instance, including packets,
using arbitrary VNIs.</t> VNIs, for instance.</t>

<t>One can envision support of an HMAC-like Message Authentication
Code (MAC) <xref target="RFC2104"/> in an NVO3 extension to
authenticate the header and the outer IP addresses, thereby preventing
attackers from injecting packets with spoofed VNIs.</t>

<t>Another aspect of security is payload security.  Essentially  Essentially, this
makes packets that look like the following:</t>

<sourcecode>

<artwork><![CDATA[
  IP|UDP|NVO3 Encap|DTLS/IPsec-ESP Extension|payload.
</sourcecode>
]]></artwork>

<t>This is desirable since we because:</t>
<ul>
<li>we still have the UDP header for ECMP, the ECMP,</li>
<li>the NVO3 header is in plain text so it can be read by network elements,
and different and</li>
<li>different security or other payload transforms can be supported on
a single UDP port (we don't need a separate UDP port for DTLS/IPsec DTLS/IPsec; see <xref target="RFC9147"/> and <xref target="RFC9147"/>/<xref target="RFC6071"/>).</t> target="RFC6071"/>, respectively).</li>
</ul>

    </section>
    <section>  <!-- 6.2.3 -->
      <name>Group Based
      <name>Group-Based Policy</name>

<t>Another use case would be to carry the Group Based Group-Based Policy (GBP)
source group information within a NVO3 header extension in a similar
manner as has been implemented for VXLAN <xref target="VXLANgroup"/>. target="I-D.smith-vxlan-group-policy"/>.
This allows various forms of policy such as access control and QoS to
be applied between abstract groups rather than coupled to specific
endpoint addresses.</t>
    </section>
  </section>
  <section>  <!-- 6.3 -->

  <section anchor="HardwareConsiderations">
    <name>Hardware Considerations</name>
<t>Hardware restrictions should be taken into consideration along with
future hardware enhancements that may provide more flexible metadata (MD)
processing.  However, the set of options that need to and will be
implemented in hardware will be a subset of what is implemented in
software, since
software. This is because software NVEs are likely to grow features, and hence
option support, at a more rapid rate.</t>

<t>It is hard to predict which options will be implemented in which
piece of hardware and when.  That depends on whether the hardware will
be in the form of</t> of:</t>

<ul>
  <li>a NIC providing increasing offload capabilities to software
  NVEs,</li>

  <li>or a
  NVEs, or</li>

  <li>a switch chip being used as an NVE gateway towards
  non-NVO3 parts of the network,</li>

  <li>or even a network, or even</li>

  <li>a transit device that participates in the NVO3
  dataplane,
  data plane, e.g., for OAM purposes.</li>
</ul>

<t>A result of this is that it doesn't look useful to prescribe some
order of to the options so that the ones that are likely to be implemented
in hardware come first; we first. We can't decide such an order when we define
the options, however options; however, a control plane can enforce such an order for
some hardware implementation.</t> implementations.</t>

<t>We do know that hardware initially needs to initially be able to efficiently
skip over the NVO3 header to find the inner payload.  That is needed
both for NICs implementing various TCP offload mechanisms and for
transit devices and NVEs applying policy or ACLs to the inner
payload.</t>

  </section>
  <section>  <!-- 6.4 -->
    <name>Extension Size</name>

<t>Extension header length has a significant impact on hardware and
software implementations.  A maximum total header length that is too
small will unnecessarily constrain software flexibility.  A maximum
total header length that is too large will place a nontrivial cost on
hardware implementations.  Thus, the DT recommends that there be a
minimum and maximum total available extension header length specified.
The maximum total header length is determined by the size of the bit
field allocated for the total extension header length field.  The risk
with this approach is that it may be difficult to extend the total
header size in the future.  The minimum total header length is
determined by a requirement in the specifications that all
implementations must meet.  The risk with this approach is that all
implementations will only implement support for the minimum total
header length length, which would then become the de facto maximum total
header length.</t>

<t>The recommended minimum total available header length is 64
bytes.</t>

<t>The size of an extension header should always be 4 byte 4-byte
aligned.</t>

<t>The maximum length of a single option should be large enough to
meet the different extension use case requirements, e.g., for in-band
telemetry and future use.</t>

  </section>

  <section>  <!-- 6.5 -->
    <name>Ordering of Extension Headers</name>
<t>To support hardware nodes at the target NVE or at a transit device
that can process one or a few extension headers in TCAM, a control
plane in such a deployment can could signal a capability to ensure that a
specific extension header will always appear in a specific order, for
example the
example, that such a specific extension header appear first one in the packet.</t>

<t>The order of the extension headers should be hardware friendly for
both the sender and the receiver and possibly some transit devices
also.
as well. This may requre require that the extension headers and their order be
dynamically
determined dynamically based on the hardware of those devices.</t>

<t>Transit devices don't participate in control plane communication
between the end points endpoints and are not required to process the extension
headers; however, if they do, they may need to process only a small
subset of the extension headers that will be consumed by target
NVEs.</t>
  </section>

  <section>  <!-- 6.6 -->
    <name>TLV versus Bit Fields</name>

<t>If there is a well-known initial set of options that are is likely to
be implemented in software and in hardware, it can be efficient to use
the bit fields approach to indicate the presence of extensions as in
GUE.  However, as described in section 6.3, <xref target="HardwareConsiderations"/>, if options are added over
time and different subsets of options are likely to be implemented in
different pieces of hardware, then it would be hard for the IETF to
specify which options should get the early bit fields.  TLVs are a lot
more flexible, which avoids the need to determine the relative
importance of different options.  However, general TLVs of arbitrary
order, size, and repetition are difficult to implement in hardware.  A
middle ground is to use TLVs with restrictions on their size and
alignment, observing that individual TLVs can have a fixed length, and
to support via the control plane a method such that an NVE will only
receive options that it needs and implements.  The control plane
approach can potentially be used to control the order of the TLVs sent
to a particular NVE.  Note that transit devices are not likely to
participate in the control plane; hence, to the extent that they need
to participate in option processing, some other method must be
used. Transit devices would have issues with future GUE bit fields
being defined for future options as well.</t>

<t>A benefit of TLVs from a hardware perspective is that they are self describing,
i.e., all the information is in the TLV.  In a bit field
approach, the hardware needs to look up the bit to determine the
length of the data associated with the bit through some separate
table, which would add hardware complexity.</t>

<t>There are use cases where multiple modules of software are running
on an NVE.  These can be modules such as a diagnostic module by one
vendor that does packet sampling and another module from a different
vendor that implements a firewall.  Using a TLV format, it is easier
to have different software modules process different TLVs, which could
be standard extensions or vendor specific extensions defined by the
different vendors, TLVs without conflicting with each other. Such TLVs could be standard extensions or vendor-specific extensions.  This can help
with hardware modularity as well. There are some implementations with
options that allows allow different software modules, like MAC learning and
security, to process different options.</t>
  </section>

  <section>  <!-- 6.7 -->
    <name>Control Plane Considerations</name>

<t>Given that we want to allow considerable flexibility and
extensibility, e.g.,
extensibility (e.g., for software NVEs, NVEs), yet want to be able to support
important extensions in less flexible contexts such as hardware NVEs,
it is useful to consider the control plane.  By control plane in this
section we mean both protocols, such as EVPN <xref target="RFC8365"/>
and others, and deployment specific configuration.</t> deployment-specific configurations.</t>

<t>If each NVE can express in the control plane that it only supports
certain extensions (which could be a single extension, or a few), and
the source NVEs only include supported extensions in the NVO3 packets,
then the target NVE can both use a simpler parser (e.g., a TCAM might
be usable to look for a single NVO3 extension) and the depth of the
inner payload in the NVO3 packet will be minimized.  Furthermore, if
the target NVE cares about a few extensions and can express in the
control plane the desired order of those extensions in the NVO3
packets, then the deployment can provide useful functionality with
simplified hardware requirements for the target NVE.</t>

<t>Transit devices that are not aware of the NVO3 extensions somewhat
benefit from such an approach, since the inner payload is less deep in
the packet if no extraneous extension headers are included in the
packet.  In general, a transit device is not likely to participate in
the NVO3 control plane.  However, configuration mechanisms can take
into account limitations of the transit devices used in particular
deployments.</t>

<t>Note that with this approach approach, different NVEs could desire different
extensions or sets of extensions, which means that the source NVE
needs to be able to place different sets of extensions in different
NVO3 packets, and perhaps in a different order.  It also assumes that
underlay multicast or replication servers are not used together with
NVO3 extension headers.</t>

<t>There is a need to consider mandatory extensions versus optional
extensions.  Mandatory extensions require the receiver to drop the
packet if the extension is unknown.  A control plane mechanism can
prevent the need for dropping unknown extensions, since they would not
be included to target NVEs that do not support them.</t>

<t>The control planes defined today need to add the ability to
describe the different encapsulations.  Thus, perhaps EVPN <xref
target="RFC8365"/> and any other control plane protocol that the IETF
defines should have a way to indicate the supported NVO3 extensions
and their order, order for each of the encapsulations supported.</t>

<t>Developing a separate draft document on guidance for option processing and
control plane participation should be considered.  This should provide
examples/guidance
examples and guidance on the range of usage models and deployments deployment scenarios
for specific options and options. It should also provide examples of option ordering that are relevant for that specific
deployment.  This includes end points endpoints and middle boxes middleboxes that are using the
options.  Having the control plane negotiate the constraints is the
most appropriate and flexible way to address these requirements.</t>
  </section>

  <section>  <!-- 6.8 -->
    <name>Split NVE</name>
<t>If there is a need for hosts to send and receive options in a split
NVE case <xref target="RFC8394"/>, this is possible using any of the
existing extensible encapsulations (Geneve, (GPE with NSH, GUE, GPE+NSH) or Geneve) by defining
a way to carry those over other transports. An NSH can already be used
over different transports.</t>

<t>If this is needed with other encapsulations encapsulations, it can be done by
defining an Ethertype so that it can be carried over Ethernet and
IEEE Std 802.1Q <xref target="IEEE802.1Q"/>.</t>

<t>If there is a need to carry other encapsulations over MPLS, it
would require an EVPN control plane to signal that other encapsulation
header +
headers and options will be present in front of the L2 Layer 2 (L2) packet.  The VNI
can be ignored in the header, and the MPLS label will be the one used
to identify the EVPN L2 instance.</t>
  </section>

  <section anchor="LargerVNI"> <!-- 6.9 -->
    <name>Larger VNI Considerations</name>

<t>Whether we should make the VNI 32-bits 32 bits or larger was one of the
topics considered.  The benefit of a 24-bit VNI would be to avoid
unnecessary changes with existing proposals and implementations that
are almost all, if not all, using a 24-bit VNI.  If we need a larger
VNI, perhaps for a telemetry case, an extension can be used to support
that. </t>
  </section>
</section>
<section>  <!-- 7. -->

<section anchor="Recommendations">
  <name>Recommendations</name>

<t>The Design Team (DT) reported that Geneve was most suitable as a
starting point for a proposed standard for network virtualization, for
the following reasons given below. This conclusion was supported by
the NVO3 Working Group.</t>

<ol>
  <li>On whether the VNI should be in the base header or in an extension
  header and whether it should be a 24-bit or 32-bit field (see <xref
  target="LargerVNI"/>), it was agreed that the VNI is critical
  information for network virtualization and MUST <bcp14>MUST</bcp14> be present in all
  packets.  It was also agreed that a 24-bit VNI, which is supported
  by Geneve, matches the existing widely used encapsulation formats,
  i.e., VXLAN <xref target="RFC7348"/> and NVGRE Network Virtualization Using Generic Routing Encapsulation (NVGRE) <xref
  target="RFC7637"/>, and hence is more suitable to use going
  forward.</li>

  <li>The Geneve header has the total options length length, which allows
  skipping over the options for NIC offload operations and will allow
  transit devices to view flow information in the inner payload.</li>

  <li>The option of using an NSH <xref target="RFC8300"/> with VXLAN-GPE
  was considered considered, but given that an NSH is targeted at service chaining
  and contains service chaining information, it is less suitable for
  the network virtualization use case.  The other downside for of
  VXLAN-GPE was the lack of a header length in VXLAN-GPE, which makes
  skipping over the headers to process inner payload payloads more difficult. A
  Total Option Length
  total options length is present in Geneve.  It is not possible to
  skip any options in the middle with VXLAN-GPE.  In principle principle, a split
  between a base header and a header with options is interesting
  (whether that options header is an NSH or some new header without ties
  to a service path).  Whether it would make sense to either use an NSH
  for this, this or define a new NVO3 options header was explored.
  However, this makes it slightly harder to find the inner payload
  since the length Length field is not in the NVO3 header itself.  Thus, one
  more field would have to be extracted to compute the start of the
  inner payload.  Also, if the experience with IPv6 extension headers
  is a guide, there would be a risk that key pieces of hardware might
  not implement the options header, resulting in future calls to
  deprecate its use.  Making the options part of the base NVO3 header
  has less of those issues.  Even though the implementation of any
  particular option can not can't be predicted ahead of time, the option
  mechanism and ability to skip the options is likely to be broadly
  implemented.</li>

  <li>The TLV style and bit field style of extension mechanisms were compared. It
  was deemed that parsing either TLVs or bit fields is expensive and, expensive, and
  while bit fields may be simpler to parse, it is they are also more
  restrictive and requires require guessing which extensions will be widely
  implemented so they can in order to get early bit assignments. Given that half
  the bits are already assigned in GUE, a widely deployed extension
  may appear in a flag extension, and this will require extra
  processing,
  processing to dig the flag from the flag extension and then look
  for the extension itself.  Also  Also, bit fields are not flexible enough
  to address the requirements from OAM, Telemetry, telemetry, and security
  extensions,
  extensions for variable length option variable-length options and different subtypes of the
  same option.  While TLVs are more flexible, a control plane can
  restrict the number of option TLVs as well as the order and size of
  the TLVs to limit this flexibility and make the TLVs simpler for a
  dataplane
  data plane implementation to handle.</li>

  <li>The multi-vendor NVE case was briefly discussed, as was the need
  to allow vendors to put their own extensions in the NVE header.
  This is possible with TLVs.</li>

<li>It was agreed that the C (Critical) bit (Critical bit) in Geneve is
  helpful. This bit indicates that the header includes options which that
  must be parsed parsed, or else the packet must be discarded. It The bit allows a receiver NVE to
  easily decide whether or not to process options or not, for example (such as a UUID
  based UUID-based packet trace, trace) and decide how an optional extension such as that can be ignored by ignored. Thus, a receiver NVE and thus make Critical bit makes it easy for the NVE to skip over the options. options not marked with such a bit.  Thus, the C bit should remain as defined in
  Geneve.</li>

  <li>There are already some extensions of varying sizes that are being discussed  (see
  section 6.2) of varying sizes.
  <xref target="ExtensionsUseCases"/>). By using Geneve options options, it is
  possible to get in-band parameters like switch id, ingress port,
  egress port, internal delay, and queue size using TLV extensions for
  telemetry purpose purposes from switches. It is also possible to add
  security extension TLVs like HMAC <xref target="RFC2104"/> and
  DTLS/IPsec (see <xref target="RFC9147"/> and <xref target="RFC9147"/>/<xref target="RFC6071"/> target="RFC6071"/>, respectively) to
  authenticate the Geneve packet header and secure the Geneve packet
  payload by software or hardware tunnel endpoints.  A Group Based Group-Based
  Policy extension TLV can be carried as well.</li>

  <li>There are already implementations of Geneve options deployed in
  production networks.  There is as well new hardware supporting
  Geneve TLV parsing. parsing as well.  In addition, an In-band Telemetry (INT) specification <xref
  target="INT"/> specification is being developed by P4.org that
  illustrates the option of INT meta data metadata carried over Geneve.
  OVN/OVS Open Virtual Network (OVN) and Open vSwitch (OVS) <xref target="OVN"/> have also defined some one or more option TLV(s) TLVs
  for Geneve.</li>

<li>Usage requirements (see Section 6) <xref
target="CommonEncapsulationConsiderations"/>) have been addressed while also
considering the requirements and implementations in general
  including (including those for
software and hardware.</li> hardware).</li>
</ol>

<t>There seems to be interest in standardizing some well-known secure
option TLVs to secure the header and payload to guarantee
encapsulation header integrity and tenant data privacy.  The working
group should consider standardizing such option(s).</t>

<t>The following enhancements to Geneve are recommended to make it
more suitable to hardware and yet provide flexibility for
software:</t>

<ul>
  <li>The following sort of text is recommended: recommended in Geneve documents: while TLVs are more
  flexible, a control plane can restrict the number of option TLVs as
  well as the order and size of the TLVs to make it simpler for a data
  plane implementation in software or hardware to handle.  For
  example, there may be some critical information such as a secure
  hash that must be processed in a certain order at lowest
  latency.</li>

  <li>A control plane can negotiate a subset of option TLVs and
  certain TLV ordering, as well as limiting the total number of option
  TLVs present in the packet, for example, to allow for hardware
  capable of processing fewer options.  Hence, the control plane needs
  to have the ability to describe the supported TLVs subset and their
  order.</li>

  <li>The Geneve documents should specify that the subset and order of
  option TLVs SHOULD <bcp14>SHOULD</bcp14> be configurable for each remote NVE in the
  absence of a protocol control plane.</li>

<li>Geneve should follow fragmentation recommendations in overlay services
  like PWE3 and the L2/L3 VPN recommendations to guarantee larger MTU MTUs for the
  tunnel overhead (<xref target="RFC3985"/> Section
  5.3).</li>

  <li>Geneve target="RFC3985" sectionFormat="comma"
  section="5.3"/>).</li>

  <li>The Geneve documents should provide a recommendation for critical C bit
  processing - (Critical bit)
  processing. This text could specify how critical bits can be used with
  control plane specifying planes and specify the critical options.</li>

  <li>Given that there is a telemetry option use case for a length of
  256 bytes, it is recommended that Geneve increase the Single single TLV
  option length to 256.</li>

  <li>Geneve address requirements for OAM considerations for alternate
  marking and for performance measurements that need a 2 bit 2-bit field in
  the header should be considered and the need for the current OAM bit
  in the Geneve Header header should be clarified.</li>

  <li>The WG should work on security options for Geneve.</li>
</ul>
</section>
<section anchor="Acknowledgements">  <!-- 8. -->
  <name>Acknowledgements</name>

<t>The authors would like to thank Tom Herbert for providing the
motivation for the Security/Integrity extension, and for his valuable
comments, T. Sridhar for his valuable comments and feedback, Anoop
Ghanwani for his extensive comments, and Ignas Bagdonas.</t>

</section>

<section>  <!-- 9. -->
  <name>Security Considerations</name>

<t>This document does not introduce any additional security constraints;
however, <xref target="SecExt"/> discusess discusses security/integrity extensions and
this document suggests, in Section
7, <xref target="Recommendations"/>, that the the nvo3 NVO3 WG
work on security options for Geneve.</t>

</section> <!-- end Security Considerations -->
<section anchor="IANA">
  <name>IANA Considerations</name>

<t>This document requires has no IANA actions.</t>

</section>

</middle>

<!-- ____________________BACK_MATTER____________________ -->

<back>

<displayreference target="I-D.ietf-intarea-gue-extensions" to="GUE-EXTENSIONS"/>
<displayreference target="I-D.ietf-intarea-gue" to="GUE"/>
<displayreference target="I-D.ietf-nvo3-vxlan-gpe" to="VXLAN-GPE"/>
<displayreference target="I-D.smith-vxlan-group-policy" to="VXLAN-GROUP"/>
<displayreference target="I-D.hy-nvo3-gue-4-nvo" to="GUE-ENCAPSULATION"/>

<references>
  <name>References</name>
  <references>
    <name>Normative References</name>

  <xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.2119.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
  <xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.8174.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>

  </references>
  <references>
  <name>Informative References</name>

<reference anchor="ietf_gue_extensions"
	   target="https://datatracker.ietf.org/doc/draft-ietf-intarea-gue-extensions/">
  <front>
    <title>Extensions for Generic UDP Encapsulation</title>
    <author initials="T." surname="Herbert"/>
    <author initials="L." surname="Yong"/>
    <author initials="F." surname="Templin"/>
    <date year="2019" month="March" day="8"/>
  </front>
  <seriesInfo name="work in" value="progress"/>
</reference>

<reference anchor="ietf_intarea_gue"
	   target="">
  <front>
    <title>Generic UDP Encapsulation</title>
    <author initials="T." surname="Herbert"/>
    <author initials="L." surname="Yong"/>
    <author initials="O." surname="Zia"/>
    <date year="2019" month="October" day="26"/>
  </front>
  <seriesInfo name="work in" value="progress"/>
</reference>

<!-- [I-D.ietf-intarea-gue-extensions] IESG state: Expired as of 09/16/24 -->
  <xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-intarea-gue-extensions.xml"/>

<!-- [I-D.ietf-intarea-gue] IESG state: Expired as of 09/16/24 -->
  <xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-intarea-gue.xml"/>

<reference anchor="IEEE802.1Q">
  <front>
  <title>Bridges
  <title>IEEE Standard for Local and Metropolitan Area Networks--Bridges and Bridged Networks</title>
  <author initials="IEEE" surname="802.1 WG"
          fullname="IEEE 802.1 Working Group">
      <organization>Institute for Electrical and Electronic
      Engineers</organization>
  <author>
    <organization>IEEE</organization>
  </author>
  <date year="2014" month="November" day="3"/> year="2022" month="December"/>
  </front>
  <seriesInfo name="IEEE Std" value="802.1Q-2014"/> value="802.1Q-2022"/>
  <seriesInfo name="DOI" value="10.1109/IEEESTD.2022.10004498"/>
</reference>

<reference anchor="INT"	target="https://p4.org/p4-spec/docs/INT_v2_1.pdf">
  <front>
    <title>In-band Network Telemetry (INT) Dataplane Specification</title>
    <author fullname="P4.org"/>
    <author>
      <organization>P4.org Applications Working Group</organization>
    </author>
    <date year="2020" month="November"/>
  </front>
</reference>

<!-- [nvo3_vxlan_gpe] [I-D.ietf-nvo3-vxlan-gpe] IESG state: Expired as of 09/16/24. Entered the long way to display editor roles-->
<reference anchor="nvo3_vxlan_gpe"
	   target="https://datatracker.ietf.org/doc/draft-ietf-nvo3-vxlan-gpe/"> anchor="I-D.ietf-nvo3-vxlan-gpe" target="https://datatracker.ietf.org/doc/html/draft-ietf-nvo3-vxlan-gpe-13">
  <front>
    <title>Generic Protocol Extension for VXLAN (VXLAN-GPE)</title>
    <author fullname="Fabio Maino" initials="F." surname="Maino"/> surname="Maino" role="editor">
      <organization>Cisco Systems</organization>
    </author>
    <author fullname="Larry Kreeger" initials="L." surname="Kreeger"/> surname="Kreeger" role="editor">
      <organization>Arrcus</organization>
    </author>
    <author fullname="Uri Elzur" initials="U." surname="Elzur"/> surname="Elzur" role="editor">
      <organization>Intel</organization>
    </author>
    <date year="2023" day="4" month="November" day="04"/> year="2023"/>
  </front>
  <seriesInfo name="work in" value="progress"/> name="Internet-Draft" value="draft-ietf-nvo3-vxlan-gpe-13"/>
</reference>

<reference anchor="OVN" target="https://www.openvswitch.org/">
  <front>
    <title></title>
    <author fullname="Open Virtual Network"/>
    <title>Open vSwitch</title>
    <author>
      <organization>Linux Foundation</organization>
    </author>
  </front>
</reference>

<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.2104.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2104.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.2418.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2418.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.3985.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3985.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.6071.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6071.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.6291.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6291.xml"/>

<!--Note: RFC 7042 was obsoleted by RFC 9542-->
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.7042.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9542.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.7348.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7348.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.7637.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7637.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.8300.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8300.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.8365.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8365.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.8394.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8394.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.8926.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8926.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.9147.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9147.xml"/>
<xi:include
    href="https://www.rfc-editor.org/refs/bibxml/reference.RFC.9197.xml"/>

<reference anchor="VXLANgroup"
	   target="https://datatracker.ietf.org/doc/html/draft-smith-vxlan-group-policy-05">
  <front>
    <title>VXLAN Group Policy Option</title>
    <author initials="M." surname="Smith"/>
    <author initials="L." surname="Kreeger"/>
    <date year="2018" month="October" day="22"/>
  </front>
  <seriesInfo name="work in" value="progress"/>
</reference>

</references>

<section> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9197.xml"/>

<!-- Appendix A --> [I-D.smith-vxlan-group-policy] IESG state: Expired as of 09/16/24-->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.smith-vxlan-group-policy.xml"/>

<!--[draft-hy-nvo3-gue-4-nvo-04] Added during AUTH48. IESG state: Expired as of 09/16/24-->
<xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.hy-nvo3-gue-4-nvo.xml"/>
</references>
</references>

<section anchor="EncapsulationComparison">
  <name>Encapsulation Comparison</name>

   <section> <!-- A.1 -->
    <name>Overview</name>

    <t>This section presents a comparison of the three NVO3
    encapsulation proposals, proposals: Geneve <xref target="RFC8926"/>, GUE
    <xref target="ietf_intarea_gue"/>, target="I-D.ietf-intarea-gue"/>, and VXLAN-GPE <xref
    target="nvo3_vxlan_gpe"/>.
    target="I-D.ietf-nvo3-vxlan-gpe"/>.  The three encapsulations use an outer
    UDP/IP transport.  Geneve and VXLAN-GPE use an 8-octet header,
    while GUE uses a 4-octet header.  In addition to the base header,
    optional extensions may be included in the encapsulation, as
    discussed in Section A.2 <xref target="Extensibility"/> below.</t>
  </section>
  <section>  <!-- A.2 -->
  <section anchor="Extensibility">
    <name>Extensibility</name>

    <section>  <!-- A.2.1 -->
      <name>Native
      <name>Innate Extensibility Support</name>

<t>The Geneve and GUE encapsulations both enable optional headers to
be incorporated at the end of the base encapsulation header.</t>

<t>VXLAN-GPE does not provide native innate support for header extensions.
However, as discussed in <xref target="nvo3_vxlan_gpe"/>, target="I-D.ietf-nvo3-vxlan-gpe"/>,
extensibility can be attained to some extent if the Network Service
Header (NSH) <xref target="RFC8300"/> is used immediately following
the VXLAN-GPE header.  The NSH supports either a fixed-size extension (MD
Type 1), 1) or a variable-size TLV-based extension (MD Type 2).  Note
that NSH-over-VXLAN-GPE implies an additional overhead of the 8-octets
NSH header, 8-octet
NSH, in addition to the VXLAN-GPE header.</t>

    </section>
    <section>  <!-- A.2.2 -->
      <name>Extension Parsing</name>

<t>The Geneve Variable Length Options variable-length options are defined as Type/Length/Value Type-Length-Value
(TLV) extensions.  Similarly, VXLAN-GPE, when using an NSH, can include
NSH TLV-based extensions.  In contrast, GUE defines a small set of
possible extension fields (proposed in <xref
target="ietf_gue_extensions"/>),
target="I-D.ietf-intarea-gue-extensions"/> and <xref
target="I-D.hy-nvo3-gue-4-nvo"/>), and a set of flags in the GUE header
that indicate for each extension type whether it is present or
not.</t>

<t>TLV-based extensions, as defined in Geneve, provide the flexibility
for a large number of possible extension types.  Similar behavior can
be supported in NSH-over-VXLAN-GPE when using MD Type 2.  The
flag-based approach taken in GUE strives to simplify implementations
by defining a small number of possible extensions used in a fixed
order.</t>

<t>The Geneve and GUE headers both include a length field, defining Length field that defines
the total length of the encapsulation, including the optional
extensions.  This length Length field simplifies the parsing by transit
devices that skip the encapsulation header without parsing its
extensions.</t>

    </section>
    <section>  <!-- A.2.3 -->
      <name>Critical Extensions</name>

<t>The Geneve encapsulation header includes the 'C' C field, which
indicates whether the current Geneve header includes critical options,
that is to say, options which must be parsed by the target NVE.  If
the endpoint is not able to process a critical option, the packet is
discarded.</t>

    </section>
    <section>  <!-- A.2.4 -->
      <name>Maximal Header Length</name>

<t>The maximal header length in Geneve, including options, is 260
octets.  GUE defines the maximal header to be 128 octets.  VXLAN-GPE
uses a fixed-length header of 8 octets, unless NSH-over-VXLAN-GPE is
used, yielding an encapsulation header of up to 264 octets.</t>

    </section>
  </section>
  <section>  <!-- A.3 -->
    <name>Encapsulation Header</name>

    <section>  <!-- A.3.1 -->
      <name>Virtual Network Identifier (VNI)</name>

<t>The Geneve and VXLAN-GPE headers both include a 24-bit VNI field.
GUE, on the other hand, enables the use of a 32-bit field called VNID;
this field is not included in the GUE header, header but was defined as an
optional extension in <xref target="ietf_gue_extensions"/>.</t> target="I-D.hy-nvo3-gue-4-nvo"/>.</t>

<t>The VXLAN-GPE header includes the 'I' I bit, indicating that the VNI
field is valid in the current header.  A similar indicator is defined
as a flag in the GUE header <xref target="ietf_gue_extensions"/>.</t> target="I-D.ietf-intarea-gue-extensions"/>.</t>

    </section>
    <section> <!-- A.3.2 -->
      <name>Next Protocol</name>

<t>All three encapsulation headers include a field that specifies the
type of the next protocol header, which resides after the NVO3
encapsulation header.  The Geneve header includes a 16-bit field that
uses the IEEE Ethertype convention.  GUE uses an 8-bit field, which
uses the IANA Internet protocol numbering.  The VXLAN-GPE header
incorporates an 8-bit Next Protocol field, using a VXLAN-GPE-specific
registry, registry specific to VXLAN-GPE, defined in <xref target="nvo3_vxlan_gpe"/>.</t> target="I-D.ietf-nvo3-vxlan-gpe"/>.</t>

<t>The VXLAN-GPE header also includes the 'P' P bit, which explicitly
indicates whether the Next Protocol field is present in the current
header.</t>

    </section>
    <section>  <!-- A.3.3 -->
      <name>Other Header Fields</name>

<t>The OAM bit, which is defined in Geneve and in VXLAN-GPE, indicates
whether the current packet is an OAM packet.  The GUE header includes
a similar field, field but uses different terminology; the GUE 'C-bit' C bit (Control bit)
specifies whether the current packet is a control packet.  Note that
the GUE control C bit can potentially be used in a large set of
protocols that are not OAM protocols.  However, the control packet
examples discussed in <xref target="ietf_intarea_gue"/> target="I-D.ietf-intarea-gue"/> are
OAM-related.</t>
related to OAM.</t>

<t>Each of the three NVO3 encapsulation headers includes a 2-bit
Version field, which is currently defined to be zero.</t>

<t>The Geneve and VXLAN-GPE headers include reserved fields; 14 bits
in the Geneve header, header and 27 bits in the VXLAN-GPE header are
reserved.</t>

    </section>
  </section>
  <section>  <!-- A.4 -->
    <name>Comparison Summary</name>

<t>The following table summarizes the comparison between the three
NVO3 encapsulations. In some cases cases, a plus sign ("+") or minus sign
("-") is used to indicate that the header is stronger or weaker in an
area
area, respectively.</t>

<figure anchor="ComparisonChart">
  <name>NVO3 Encapsulations Comparison</name>
    <artwork type="ascii-art"

<table anchor="EncapsulationsComparisonTable" align="center">
      <![CDATA[
+----------------+----------------+----------------+----------------+
|                |     Geneve     |      GUE       |   VXLAN-GPE    |
+----------------+----------------+----------------+----------------+
| Outer transport|     UDP/IP     |     UDP/IP     |     UDP/IP     |
|
  <name>Encapsulations Comparison</name>
  <thead>
    <tr>
      <th></th>
      <th>Geneve</th>
      <th>GUE</th>
      <th>VXLAN-GPE</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Outer transport UDP Port Number|     6081       |     6080       |     4790       |
+----------------+----------------+----------------+----------------+
| Base header    |    8 octets    |    4 octets    |    8 Number</td>
      <td>UDP/IP 6081</td>
      <td>UDP/IP 6080</td>
      <td>UDP/IP 4790</td>
    </tr>
    <tr>
      <td>Base header length</td>
      <td>8 octets</td>
      <td>4 octets</td>
      <td>8 octets    |
| length         |                |                | (16 octets    |
|                |                |                | using NSH)   |
+----------------+----------------+----------------+----------------+
| Extensibility  |Variable length |Extension fields| No native ext- |
|                |    options     |                | ensibility.    |
|                |                |                | an NSH)</td>
    </tr>
    <tr>
      <td>Extensibility</td>
      <td>Variable-length options</td>
      <td>Extension fields</td>
      <td>No innate extensibility. Might use NSH. |
+----------------+----------------+----------------+----------------+
| Extension      |   TLV-based    |   Flag-based   |   TLV-based    |
| an NSH.</td>
    </tr>
    <tr>
      <td>Extension parsing method |                |                |(using method</td>
      <td>TLV-based</td>
      <td>Flag-based</td>
      <td>TLV-based (using an NSH with |
|                |                |                | MD Type 2)   |
+----------------+----------------+----------------+----------------+
| Extension      |    Variable    |     Fixed      |    Variable    |
| order          |                |                | 2)</td>
    </tr>
    <tr>
      <td>Extension order</td>
      <td>Variable</td>
      <td>Fixed</td>
      <td>Variable (using NSH)   |
+----------------+----------------+----------------+----------------+
| Length field   |       +        |       +        |       -        |
+----------------+----------------+----------------+----------------+
| Max Header     |   260 octets   |   128 octets   |    8 an NSH)</td>
    </tr>
    <tr>
      <td>Length field</td>
      <td>+</td>
      <td>+</td>
      <td>-</td>
   </tr>
   <tr>
     <td>Max header length</td>
     <td>260 octets</td>
     <td>128 octets</td>
     <td>8 octets    |
| Length         |                |                |(264 (264 using NSH) |
+----------------+----------------+----------------+----------------+
| Critical exte- |       +        |       -        |       -        |
| nsion bit      |                |                |                |
+----------------+----------------+----------------+----------------+
| VNI an NSH)</td>
  </tr>
  <tr>
    <td>Critical extension bit</td>
    <td>+</td>
    <td>-</td>
    <td>-</td>
  </tr>
  <tr>
    <td>VNI field size |    24 size</td>
    <td>24 bits</td>
    <td>32 bits     |    32 (extension)</td>
    <td>24 bits</td>
  </tr>
  <tr>
   <td>Next Protocol field</td>
   <td>16 bits     |    24 Ethertype registry</td>
   <td>8 bits     |
|                |                |  (extension)   |                |
+----------------+----------------+----------------+----------------+
| Next Internet protocol  |    16 registry</td>
   <td>8 bits     |     8 bits     |     8 bits     |
| field          |   Ethertype    | Internet prot- | New registry  |
|                |   registry     | ocol registry  |                |
+----------------+----------------+----------------+----------------+
| Next registry</td>
  </tr>
  <tr>
    <td>Next protocol  |       -        |       -        |       +        |
| indicator      |                |                |                |
+----------------+----------------+----------------+----------------+
| OAM indicator</td>
    <td>-</td>
    <td>-</td>
    <td>+</td>
  </tr>
  <tr>
    <td>OAM / control  |    OAM bit     | Control bit   |    OAM bit     |
| field          |                |                |                |
+----------------+----------------+----------------+----------------+
| Version field  |    2 bits      |    2 bits      |    2 bits      |
+----------------+----------------+----------------+----------------+
| Reserved bits  |   14 bits      |     none       |   27 bits      |
+----------------+----------------+----------------+----------------+
      ]]>
    </artwork>
</figure> field</td>
    <td>OAM bit</td>
    <td>Control bit</td>
    <td>OAM bit</td>
  </tr>
  <tr>
    <td>Version field</td>
    <td>2 bits</td>
    <td>2 bits</td>
    <td>2 bits</td>
  </tr>
  <tr>
    <td>Reserved bits</td>
    <td>14 bits</td>
    <td>none</td>
    <td>27 bits</td>
  </tr>
  </tbody>
</table>
  </section>
</section>

<section anchor="Acknowledgements" numbered="false">
  <name>Acknowledgements</name>

<t>The authors would like to thank <contact fullname="Tom Herbert"/> for
providing the motivation for the security/integrity extension and for his
valuable comments; <contact fullname="T. Sridhar"/> for his valuable comments
and feedback; <contact fullname="Anoop Ghanwani"/> for his extensive comments;
and <contact fullname="Ignas Bagdonas"/>.</t>

</section>

<section anchor="Contributors" numbered="false">
  <name>Contributors</name>

  <t>The following co-authors coauthors have contributed to this document:.</t> document:</t>

  <contact fullname="Ilango Ganga">
    <organization>Intel</organization>
    <address>
      <email>ilango.s.ganga@intel.com</email>
    </address>
  </contact>

  <contact fullname="Pankaj Garg">
    <organization>Microsoft</organization>
    <address>
      <email> pankajg@microsoft.com</email>
    </address>
  </contact>

  <contact fullname="Rajeev Manur">
    <organization>Broadcom</organization>
    <address>
      <email>rajeev.manur@broadcom.com</email>
    </address>
  </contact>

  <contact fullname="Tal Mizrahi">
    <organization>Huawei</organization>
    <address>
      <email>tal.mizrahi.phd@gmail.com</email>
    </address>
  </contact>

  <contact fullname="David Mozes">
    <address>
      <email>mosesster@gmail.com</email>
    </address>
  </contact>

  <contact fullname="Erik Nordmark">
    <organization>ZEDEDA</organization>
    <address>
      <email>nordmark@sonic.net</email>
    </address>
  </contact>

  <contact fullname="Michael Smith">
    <organization>Cisco</organization>
    <address>
      <email>michsmit@cisco.com</email>
    </address>
  </contact>

  <contact fullname="Sam Aldrin">
    <organization>Google</organization>
    <address>
      <email>aldrin.ietf@gmail.com</email>
    </address>
  </contact>

</section>
</back>
</rfc>