





Internet Engineering Task Force (IETF)                             Y. Li
Request for Comments: 8394                               D. Eastlake 3rd
Category: Informational                              Huawei Technologies
ISSN: 2070-1721                                               L. Kreeger
                                                            Arrcus, Inc.
                                                               T. Narten
                                                                     IBM
                                                                D. Black
                                                                Dell EMC
                                                                May 2018


Split Network Virtualization Edge (Split-NVE) Control-Plane Requirements

Abstract

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

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

Status of This Memo

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

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8394.



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Copyright Notice

   Copyright (c) 2018 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
      1.1. Terminology ................................................4
      1.2. Target Scenarios ...........................................6
   2. VM Lifecycle ....................................................7
      2.1. VM Creation Event ..........................................8
      2.2. VM Live Migration Event ....................................8
      2.3. VM Termination Event .......................................9
      2.4. VM Pause, Suspension, and Resumption Events ...............10
   3. Hypervisor-to-NVE Control-Plane Protocol Functionality .........10
      3.1. VN_Connect and VN_Disconnect ..............................10
      3.2. TSI Associate and Activate ................................12
      3.3. TSI De-Associate and Deactivate ...........................15
   4. Hypervisor-to-NVE Control-Plane Protocol Requirements ..........16
   5. VDP Applicability and Enhancement Needs ........................17
   6. Security Considerations ........................................19
   7. IANA Considerations ............................................20
   8. References .....................................................21
      8.1. Normative References ......................................21
      8.2. Informative References ....................................22
   Appendix A. VDP Illustrations (per IEEE 802.1Q) (for Information
               Only) .................................................23
   Acknowledgements ..................................................25
   Authors' Addresses ................................................26











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1.  Introduction

   In the Split Network Virtualization Edge (Split-NVE) architecture
   shown in Figure 1, the functionality of the NVE is split across an
   end device supporting virtualization and an external network device
   that is called an "External NVE".  The portion of the NVE
   functionality located on the end device is called the "tNVE"
   (terminal-side NVE), and the portion located on the External NVE is
   called the "nNVE" (network-side NVE) in this document.  Overlay
   encapsulation/decapsulation functions are normally offloaded to the
   nNVE on the External NVE.

                       +------------ Split-NVE ---------+
                       |                                |
                       |                                |
     +-----------------|-----+                          |
     | +---------------|----+|                          |
     | | +--+         \|/   ||                          |
     | | |V |TSI  +-------+ ||                   +------|-------------+
     | | |M |-----+       | ||                   |     \|/            |
     | | +--+     |       | ||                   |+--------+          |
     | | +--+     | tNVE  | ||-------------------||        |          |
     | | |V |TSI  |       | ||                   || nNVE   |          |
     | | |M |-----|       | ||                   ||        |          |
     | | +--+     +-------+ ||                   |+--------+          |
     | |                    ||                   +--------------------+
     | +-----Hypervisor-----+|
     +-----------------------+
            End Device                               External NVE

                       Figure 1: Split-NVE Structure

   The tNVE is normally implemented as a part of a hypervisor or
   container and/or a virtual switch in a virtualized end device.  This
   document uses the term "hypervisor" throughout when describing the
   Split-NVE scenario where part of the NVE functionality is offloaded
   to a separate device from the "hypervisor" that contains a VM
   (Virtual Machine) connected to a VN (Virtual Network).  In this
   context, the term "hypervisor" is meant to cover any device type
   where part of the NVE functionality is offloaded in this fashion,
   e.g., a Network Service Appliance or Linux Container.

   The Network Virtualization over Layer 3 (NVO3) problem statement
   [RFC7364] discusses the need for a control-plane protocol (or
   protocols) to populate each NVE with the state needed to perform the
   required functions.  In one scenario, an NVE provides overlay
   encapsulation/decapsulation packet-forwarding services to Tenant
   Systems that are co-resident within the NVE on the same end device



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   (e.g., when the NVE is embedded within a hypervisor or a Network
   Service Appliance).  In such cases, there is no need for a
   standardized protocol between the hypervisor and the NVE, as the
   interaction is implemented via software on a single device.  However,
   in the Split-NVE architecture scenarios shown in Figures 2 through 4
   (see Section 1.2), one or more control-plane protocols between a
   hypervisor and its associated External NVE(s) are required for the
   hypervisor to distribute the VM's networking states to the NVE(s) for
   further handling.  The protocol is an NVE-internal protocol and runs
   between tNVE and nNVE logical entities.  This protocol is mentioned
   in the "third work area" text in Section 4.5 of the NVO3 problem
   statement [RFC7364].

   VM states and state transitioning are summarized in this document,
   showing events where the NVE needs to take specific actions.  Such
   events might correspond to actions that the control-plane signaling
   protocol or protocols need to take between the tNVE and the nNVE in
   the Split-NVE scenario.  The high-level requirements to be fulfilled
   are listed in Section 4.

   To describe the requirements, this document uses VMs as an example of
   Tenant Systems, even though a VM is just one type of Tenant System
   that may connect to a VN.  For example, a service instance within a
   Network Service Appliance is another type of Tenant System, as are
   systems running on OS-level virtualization technologies like
   containers.  The fact that VMs have lifecycles (e.g., can be created
   and destroyed, can be moved, and can be started or stopped) results
   in a general set of protocol requirements, most of which are
   applicable to other forms of Tenant Systems, although not all of the
   requirements are applicable to all forms of Tenant Systems.

   Section 2 describes VM states and state transitioning in the VM's
   lifecycle.  Section 3 introduces hypervisor-to-NVE control-plane
   protocol functionality derived from VM operations and network events.
   Section 4 outlines the requirements of the control-plane protocol to
   achieve the required functionality.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.







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   This document uses the same terminology as the terminology found in
   [RFC7365].  This section defines additional terminology used by this
   document.

   Split-NVE:  A type of NVE (Network Virtualization Edge) where the
      functionalities are split across an end device supporting
      virtualization and an external network device.

   tNVE:  Terminal-side NVE.  The portion of Split-NVE functionalities
      located on the end device supporting virtualization.  The tNVE
      interacts with a Tenant System through an internal interface in
      the end device.

   nNVE:  Network-side NVE.  The portion of Split-NVE functionalities
      located on the network device that is directly or indirectly
      connected to the end device that contains the corresponding tNVE.
      The nNVE normally performs encapsulation to and decapsulation from
      the overlay network.

   External NVE:  The physical network device that contains the nNVE.

   Hypervisor:  The logical collection of software, firmware, and/or
      hardware that allows the creation and running of server or service
      appliance virtualization.  The tNVE is located under a hypervisor.
      The term "hypervisor" is loosely used in this document to refer to
      the end device supporting the virtualization.  For simplicity, we
      also use the term "hypervisor" to represent both the hypervisor
      and the container.

   Container:  Please see "Hypervisor:" above.

   VN Profile:  Metadata that is associated with a VN and applied to any
      attachment point to the VN (i.e., VAP (Virtual Access Point)
      properties that are applied to all VAPs associated with a given VN
      and used by an NVE when ingressing/egressing packets to/from a
      specific VN).  Metadata could include such information as Access
      Control Lists (ACLs) and QoS settings.  The VN Profile contains
      parameters that apply to the VN as a whole.  Control protocols
      between the NVE and the NVA (Network Virtualization Authority)
      could use the VN ID or VN Name to obtain the VN Profile.

   VSI:  Virtual Station Interface.  See [IEEE802.1Q].

   VDP:  VSI Discovery and Configuration Protocol.  See [IEEE802.1Q].







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1.2.  Target Scenarios

   In the Split-NVE architecture, an External NVE can provide offloading
   of the encapsulation/decapsulation functions and network policy
   enforcement as well as offloading of overhead from the VN overlay
   protocol.  This offloading may improve performance and/or save
   resources in the end device (e.g., hypervisor) using the
   External NVE.

   Figures 2 through 4 give example scenarios for the Split-NVE
   architecture.

              Hypervisor             Access Switch
         +------------------+       +-----+-------+
         | +--+   +-------+ |       |     |       |
         | |VM|---|       | | VLAN  |     |       |
         | +--+   | tNVE  |---------+ nNVE|       +--- Underlying
         | +--+   |       | | Trunk |     |       |    Network
         | |VM|---|       | |       |     |       |
         | +--+   +-------+ |       |     |       |
         +------------------+       +-----+-------+

                 Figure 2: Hypervisor with an External NVE


             Hypervisor       L2 Switch
         +---------------+     +-----+     +----+---+
         | +--+   +----+ |     |     |     |    |   |
         | |VM|---|    | |VLAN |     |VLAN |    |   |
         | +--+   |tNVE|-------+     +-----+nNVE|   +--- Underlying
         | +--+   |    | |Trunk|     |Trunk|    |   |    Network
         | |VM|---|    | |     |     |     |    |   |
         | +--+   +----+ |     |     |     |    |   |
         +---------------+     +-----+     +----+---+

                 Figure 3: Hypervisor with an External NVE
                Connected through an Ethernet Access Switch














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        Network Service Appliance          Access Switch
     +-----------------------------+      +-----+-------+
     | +---------------+    | \    |      |     |       |
     | |Network Service|----|  \   |      |     |       |
     | |Instance       |    |   \  | VLAN |     |       |
     | +---------------+    |tNVE| |------+nNVE |       +--- Underlying
     | +---------------+    |    | | Trunk|     |       |    Network
     | |Network Service|----|   /  |      |     |       |
     | |Instance       |    |  /   |      |     |       |
     | +---------------+    | /    |      |     |       |
     +-----------------------------+      +-----+-------+

     Figure 4: Physical Network Service Appliance with an External NVE

   Tenant Systems connect to External NVEs via a Tenant System Interface
   (TSI).  The TSI logically connects to the External NVE via a VAP
   [RFC8014].  The External NVE may provide Layer 2 or Layer 3
   forwarding.  In the Split-NVE architecture, the External NVE may be
   able to reach multiple Media Access Control (MAC) addresses and IP
   addresses via a TSI.  An IP address can be in either IPv4 or IPv6
   format.  For example, Tenant Systems that are providing network
   services (such as a transparent firewall, load balancer, or VPN
   gateway) are likely to have a complex address hierarchy.  This
   implies that if a given TSI de-associates from one VN, all the MAC
   and/or IP addresses are also de-associated.  There is no need to
   signal the deletion of every MAC or IP address when the TSI is
   brought down or deleted.  In the majority of cases, a VM will be
   acting as a simple host that will have a single TSI as well as a
   single MAC and IP address visible to the External NVE.

   Figures 2 through 4 show the use of VLANs to separate traffic for
   multiple VNs between the tNVE and the nNVE; VLANs are not strictly
   necessary if only one VN is involved, but multiple VNs are expected
   in most cases.  Hence, this document assumes the presence of VLANs.

2.  VM Lifecycle

   Figure 2 of [RFC7666] shows the states and transitions of a VM.  Some
   of the VM states are of interest to the External NVE.  This section
   illustrates the relevant phases and events in the VM lifecycle.  Note
   that the following subsections do not give exhaustive descriptions of
   VM lifecycle states.  Rather, they are intended as illustrative
   examples that are relevant to the Split-NVE architecture and not as
   prescriptive text; the goal is to capture sufficient detail to set a
   context for the signaling-protocol functionality and requirements
   described in the following sections.





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2.1.  VM Creation Event

   The VM creation event causes the VM state to transition from the
   "preparing" state to the "shutdown" state and then to the "running"
   state [RFC7666].  The end device allocates and initializes local
   virtual resources like storage in the VM's preparing state.  In the
   shutdown state, the VM has everything ready, except that CPU
   execution is not scheduled by the hypervisor and the VM's memory is
   not resident in the hypervisor.  The transition from the shutdown
   state to the running state normally requires human action or a
   system-triggered event.  The running state indicates that the VM is
   in the normal execution state.  As part of transitioning the VM to
   the running state, the hypervisor must also provision network
   connectivity for the VM's TSI(s) so that Ethernet frames can be sent
   and received correctly.  Initially, when in the running state, no
   ongoing migration, suspension, or shutdown is in process.

   In the VM creation phase, the VM's TSI has to be associated with the
   External NVE.  "Association" here indicates that the hypervisor and
   the External NVE have signaled each other and reached some form of
   agreement.  Relevant networking parameters or information have been
   provisioned properly.  The External NVE should be informed of the
   VM's TSI MAC address and/or IP address.  In addition to external
   network connectivity, the hypervisor may provide local network
   connectivity between the VM's TSI and TSIs for other VMs that are
   co-resident on the same hypervisor.  When the intra- or
   inter-hypervisor connectivity is extended to the External NVE, a
   locally significant tag, e.g., VLAN ID, should be used between the
   hypervisor and the External NVE to differentiate each VN's traffic.
   Both the hypervisor and External NVE sides must agree on that tag
   value for traffic identification, isolation, and forwarding.

   The External NVE may need to do some preparation before it signals
   successful association with the TSI.  Such preparation may include
   locally saving the states and binding information of the TSI and its
   VN or communicating with the NVA for network provisioning.

   A TSI association should be performed before the VM enters the
   running state, preferably in the shutdown state.  If the association
   with an External NVE fails, the VM should not go into the running
   state.

2.2.  VM Live Migration Event

   Live migration is sometimes referred to as "hot" migration in that,
   from an external viewpoint, the VM appears to continue to run while
   being migrated to another server (e.g., TCP connections generally
   survive this class of migration).  In contrast, "cold" migration



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   consists of shutting down VM execution on one server and restarting
   it on another.  For simplicity, the following abstract summary of
   live migration assumes shared storage, so that the VM's storage is
   accessible to the source and destination servers.  Assume that the VM
   "live migrates" from hypervisor 1 to hypervisor 2.  Such a migration
   event involves state transitions on both source hypervisor 1 and
   destination hypervisor 2.  The VM state on source hypervisor 1
   transitions from the running state to the "migrating" state and then
   to the shutdown state [RFC7666].  The VM state on destination
   hypervisor 2 transitions from the shutdown state to the migrating
   state and then to the running state.

   The External NVE connected to destination hypervisor 2 has to
   associate the migrating VM's TSI with itself (i.e., the External NVE)
   by discovering the TSI's MAC and/or IP addresses, discovering its VN,
   discovering its locally significant VLAN ID (if any), and
   provisioning other network-related parameters of the TSI.  The
   External NVE may be informed about the VM's peer VMs, storage
   devices, and other network appliances with which the VM needs to
   communicate or is communicating.  The migrated VM on destination
   hypervisor 2 should not go to the running state until all the network
   provisioning and binding have been done.

   The VM state on both the source hypervisor and the destination
   hypervisor will be the migrating state during the transfer of VM
   execution.  The migrating VM should not be in the running state at
   the same time on the source hypervisor and destination hypervisor
   during migration.  The VM on the source hypervisor does not
   transition to the shutdown state until the VM successfully enters the
   running state on the destination hypervisor.  It is possible that the
   VM on the source hypervisor stays in the migrating state for a while
   after the VM on the destination hypervisor enters the running state.

2.3.  VM Termination Event

   A VM termination event is also referred to as "powering off" a VM.  A
   VM termination event leads to the VM's transition to the shutdown
   state.  Per [RFC7666], there are two possible causes of VM
   termination:

   1.  A running VM has undergone a normal "power-off".

   2.  The VM has been migrated to another hypervisor, and the VM image
       on the source hypervisor has to stop executing and be shut down.







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   In VM termination, the External NVE connecting to that VM needs to
   deprovision the VM, i.e., delete the network parameters associated
   with that VM.  In other words, the External NVE has to de-associate
   the VM's TSI.

2.4.  VM Pause, Suspension, and Resumption Events

   A VM pause event leads to the VM transitioning from the running state
   to the "paused" state.  The paused state indicates that the VM is
   resident in memory but that CPU execution is not scheduled by the
   hypervisor [RFC7666].  The VM can be easily reactivated from the
   paused state to the running state.

   A VM suspension event leads to the VM transitioning from the running
   state to the "suspended" state.  A VM resumption event leads to the
   VM transitioning from the suspended state to the running state.  In
   the suspended state, the memory and CPU execution state of the VM are
   saved to persistent storage.  During this state, CPU execution for
   the VM is not scheduled by the hypervisor [RFC7666].

   In the Split-NVE architecture, the External NVE should not
   de-associate the paused or suspended VM, as the VM can return to the
   running state at any time.

3.  Hypervisor-to-NVE Control-Plane Protocol Functionality

   The following subsections show illustrative examples of the state
   transitions of an External NVE that are relevant to hypervisor-to-NVE
   signaling-protocol functionality.  Note: This is not prescriptive
   text for the full state machine.

3.1.  VN_Connect and VN_Disconnect

   In the Split-NVE scenario, a protocol is needed between the end
   device (e.g., hypervisor) and the External NVE it is using, in order
   to make the External NVE aware of the changing VN membership
   requirements of the Tenant Systems within the end device.

   A key driver for using a protocol rather than using static
   configuration of the External NVE is that the VN connectivity
   requirements can change frequently as VMs are brought up, moved, and
   brought down on various hypervisors throughout the data center or
   external cloud.

   Figure 5 shows the state transition for a VAP on the External NVE.
   An NVE that supports the hypervisor-to-NVE control-plane protocol
   should support one instance of the state machine for each active VN.
   The state transition on the External NVE is normally triggered by



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   events and behaviors on the hypervisor-facing side.  Some of the
   interleaved interactions between the NVE and the NVA will be
   illustrated to better explain the whole procedure, while other
   interactions will not be shown.

   +----------------+   Receive VN_Connect;     +----------------------+
   |VN_Disconnected |   return Local_Tag value  |VN_Connected          |
   +----------------+   for VN if successful;   +----------------------+
   |VN_ID;          |-------------------------->|VN_ID;                |
   |VN_State=       |                           |VN_State=VN_Connected;|
   |VN_Disconnected;|                           |Num_TSI_Associated;   |
   |                |<--Receive VN_Disconnect---|Local_Tag;            |
   +----------------+                           |VN_Context;           |
                                                +----------------------+

           Figure 5: State Transition Example of a VAP Instance
                            on an External NVE

   The External NVE must be notified when an end device requires a
   connection to a particular VN and when it no longer requires a
   connection.  Connection cleanup for the failed devices should be
   employed.  Note that this topic is out of scope for the protocol
   specified in this document.

   In addition, the External NVE should provide a local tag value for
   each connected VN to the end device to use for exchanging packets
   between the end device and the External NVE (e.g., a locally
   significant tag value per [IEEE802.1Q]).  How "local" the
   significance is depends on whether

   1.  the hypervisor has a direct physical connection to the
       External NVE (in which case the significance is local to the
       physical link) or

   2.  there is an Ethernet switch (e.g., a blade switch) connecting the
       hypervisor to the NVE (in which case the significance is local to
       the intervening switch and all the links connected to it).

   These VLAN tags are used to differentiate between different VNs as
   packets cross the shared-access network to the External NVE.  When
   the External NVE receives packets, it uses the VLAN tag to identify
   their VN coming from a given TSI, strips the tag, adds the
   appropriate overlay encapsulation for that VN, and sends it towards
   the corresponding remote NVE across the underlying IP network.

   The Identification of the VN in this protocol could be through either
   a VN Name or a VN ID.  A globally unique VN Name facilitates
   portability of a tenant's virtual data center.  Once an External NVE



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   receives a VN_Connect message, the NVE needs a way to get a
   VN_Context allocated (or to receive the already-allocated VN_Context)
   for a given VN Name or VN ID (as well as any other information needed
   to transmit encapsulated packets).  How this is done is the subject
   of the NVE-to-NVA protocol; see the "first two areas of work" text in
   Section 4.5 of [RFC7364].  The External NVE needs to synchronize the
   mapping information of the local tag and VN Name or VN ID with
   the NVA.

   The VN_Connect message can be explicit or implicit.  "Explicit" means
   that the hypervisor sends a request message explicitly for the
   connection to a VN.  "Implicit" means that the External NVE receives
   other messages, e.g., the very first TSI Associate message (see the
   next subsection) for a given VN, that implicitly indicate its
   interest in connecting to a VN.

   A VN_Disconnect message indicates that the NVE can release all the
   resources for that disconnected VN and transition to the
   VN_Disconnected state.  The local tag assigned for that VN can
   possibly be reclaimed for use by another VN.

3.2.  TSI Associate and Activate

   Typically, a TSI is assigned a single MAC address, and all frames
   transmitted and received on that TSI use that single MAC address.  As
   mentioned earlier, it is also possible for a Tenant System to
   exchange frames using multiple MAC addresses or packets with multiple
   IP addresses.

   Particularly in the case of a Tenant System that is forwarding frames
   or packets from other Tenant Systems, the External NVE will need to
   communicate the mapping between the NVE's IP address on the
   underlying network and ALL the addresses the Tenant System is
   forwarding on behalf of the corresponding VN to the NVA.

   The NVE has two ways it can discover the tenant addresses for which
   frames are to be forwarded to a given end device (and ultimately to
   the Tenant System within that end device).

   1.  It can glean the addresses by inspecting the source addresses in
       packets it receives from the end device.

   2.  The hypervisor can explicitly signal the address associations of
       a TSI to the External NVE.  An address association includes all
       the MAC and/or IP addresses possibly used as source addresses in
       a packet sent from the hypervisor to the External NVE.  The
       External NVE may further use this information to filter the
       future traffic from the hypervisor.



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   To use the second approach above, the control-plane protocol running
   between the hypervisor and the NVE must support end devices
   communicating new tenant-address associations for a given TSI within
   a given VN.

   Figure 6 shows an example of a state transition for a TSI connecting
   to a VAP on the External NVE.  An NVE that supports the hypervisor-
   to-NVE control-plane protocol may support one instance of the state
   machine for each TSI connecting to a given VN.

                De-Associate   +--------+     De-Associate
              +--------------->|  Init  |<--------------------+
              |                +--------+                     |
              |                |        |                     |
              |                |        |                     |
              |                +--------+                     |
              |                  |    |                       |
              |       Associate  |    |  Activate             |
              |      +-----------+    +-----------+           |
              |      |                            |           |
              |      |                            |           |
              |     \|/                          \|/          |
      +--------------------+                  +---------------------+
      |     Associated     |                  |       Activated     |
      +--------------------+                  +---------------------+
      |TSI_ID;             |                  |TSI_ID;              |
      |Port;               |-----Activate---->|Port;                |
      |VN_ID;              |                  |VN_ID;               |
      |State=Associated;   |                  |State=Activated;     |-+
    +-|Num_Of_Addr;        |<---Deactivate ---|Num_Of_Addr;         | |
    | |List_Of_Addr;       |                  |List_Of_Addr;        | |
    | +--------------------+                  +---------------------+ |
    |                    /|\                     /|\                  |
    |                     |                       |                   |
    +---------------------+                       +-------------------+
     add/remove/updt addr;                        add/remove/updt addr;
     or update port;                              or update port;

           Figure 6: State Transition Example of a TSI Instance
                            on an External NVE

   The Associated state of a TSI instance on an External NVE indicates
   that all the addresses for that TSI have already associated with the
   VAP of the External NVE on a given port, e.g., on port p for a given
   VN, but no real traffic to and from the TSI is expected and allowed
   to pass through.  An NVE has reserved all the necessary resources for
   that TSI.  An External NVE may report the mappings of its underlay IP
   address and the associated TSI addresses to the NVA, and relevant



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   network nodes may save such information to their mapping tables but
   not their forwarding tables.  An NVE may create ACLs or filter rules
   based on the associated TSI addresses on that attached port p but not
   enable them yet.  The local tag for the VN corresponding to the TSI
   instance should be provisioned on port p to receive packets.

   The VM migration event (discussed in Section 2) may cause the
   hypervisor to send an Associate message to the NVE connected to the
   destination hypervisor of the migration.  A VM creation event may
   also trigger the same scenario.

   The Activated state of a TSI instance on an External NVE indicates
   that all the addresses for that TSI are functioning correctly on a
   given port, e.g., port p, and traffic can be received from and sent
   to that TSI via the NVE.  The mappings of the NVE's underlay IP
   address and the associated TSI addresses should be added to the
   forwarding table rather than the mapping table on relevant network
   nodes.  ACLs or filter rules based on the associated TSI addresses on
   the attached port p on the NVE are enabled.  The local tag for the VN
   corresponding to the TSI instance must be provisioned on port p to
   receive packets.

   The Activate message makes the state transition from Init or
   Associated to Activated.  VM creation, VM migration, and VM
   resumption events (discussed in Section 2) may trigger sending the
   Activate message from the hypervisor to the External NVE.

   TSI information may get updated in either the Associated state or the
   Activated state.  The following are considered updates to the TSI
   information: add or remove the associated addresses, update the
   current associated addresses (for example, update the IP address for
   a given MAC address), and update the NVE port information based on
   where the NVE receives messages.  Such updates do not change the
   state of the TSI.  When any address associated with a given TSI
   changes, the NVE should inform the NVA to update the mapping
   information for the NVE's underlying address and the associated TSI
   addresses.  The NVE should also change its local ACLs or filter
   settings accordingly for the relevant addresses.  Port information
   updates will cause the provisioning of the local tag for the VN
   corresponding to the TSI instance on the new port and removal from
   the old port.










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3.3.  TSI De-Associate and Deactivate

   De-Associate and Deactivate behaviors are conceptually the reverse of
   Associate and Activate.

   From the Activated state to the Associated state, the External NVE
   needs to make sure the resources are still reserved but the addresses
   associated with the TSI are not functioning.  No traffic to or from
   the TSI is expected or allowed to pass through.  For example, the NVE
   needs to tell the NVA to remove the relevant information regarding
   address mapping from the forwarding and routing tables.  ACLs and
   filter rules regarding the relevant addresses should be disabled.

   From the Associated or Activated state to the Init state, the NVE
   releases all the resources relevant to TSI instances.  The NVE should
   also inform the NVA to remove the relevant entries from the mapping
   table.  ACLs or filter rules regarding the relevant addresses should
   be removed.  Local tag provisioning on the connecting port on the NVE
   should be cleared.

   A VM suspension event (discussed in Section 2) may cause the relevant
   TSI instance(s) on the NVE to transition from the Activated state to
   the Associated state.

   A VM pause event normally does not affect the state of the relevant
   TSI instance(s) on the NVE, as the VM is expected to run again soon.

   A VM shutdown event will normally cause the relevant TSI instance(s)
   on the NVE to transition to the Init state from the Activated state.
   All resources should be released.

   A VM migration will cause the TSI instance on the source NVE to leave
   the Activated state.  When a VM migrates to another hypervisor
   connecting to the same NVE, i.e., the source and destination NVE are
   the same, the NVE should use the TSI_ID and the incoming port to
   differentiate two TSI instances.

   Although the triggering messages for the state transition shown in
   Figure 6 do not indicate the difference between a VM
   creation/shutdown event and a VM migration arrival/departure event,
   the External NVE can make optimizations if it is given such
   information.  For example, if the NVE knows that the incoming
   Activate message is caused by migration rather than VM creation, some
   mechanisms may be employed or triggered to make sure the dynamic
   configurations or provisionings on the destination NVE are the same
   as those on the source NVE for the migrated VM.  For example, an IGMP
   query [RFC2236] can be triggered by the destination External NVE to
   the migrated VM so that the VM is forced to send an IGMP report to



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   the multicast router.  The multicast router can then correctly route
   the multicast traffic to the new External NVE for those multicast
   groups the VM joined before the migration.

4.  Hypervisor-to-NVE Control-Plane Protocol Requirements

   Req-1:   The protocol MUST support a bridged network connecting end
            devices to the External NVE.

   Req-2:   The protocol MUST support multiple end devices sharing the
            same External NVE via the same physical port across a
            bridged network.

   Req-3:   The protocol MAY support an end device using multiple
            External NVEs simultaneously, but only one External NVE for
            each VN (active-standby External NVE case for a VN).

   Req-4:   The protocol MAY support an end device using multiple
            External NVEs simultaneously for the same VN (active-active
            External NVE case for a VN).

   Req-5:   The protocol MUST allow the end device to initiate a request
            to its associated External NVE to be connected/disconnected
            to a given VN.

   Req-6:   The protocol MUST allow an External NVE initiating a request
            to its connected end devices to be disconnected from a
            given VN.

   Req-7:   When a Tenant System attaches to a VN, the protocol MUST
            allow for an end device and its External NVE to negotiate
            one or more locally significant tags for carrying traffic
            associated with a specific VN (e.g., tags per [IEEE802.1Q]).

   Req-8:   The protocol MUST allow an end device initiating a request
            to associate/de-associate and/or activate/deactivate some or
            all addresses of a TSI instance to a VN on an NVE port.

   Req-9:   The protocol MUST allow the External NVE initiating a
            request to de-associate and/or deactivate some or all
            addresses of a TSI instance to a VN on an NVE port.

   Req-10:  The protocol MUST allow an end device initiating a request
            to add, remove, or update address(es) associated with a TSI
            instance on the External NVE.  Addresses can be expressed in
            different formats -- for example, MAC, IP, or IP-MAC pair.





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   Req-11:  The protocol MUST allow the External NVE and the connected
            end device to authenticate each other.

   Req-12:  The protocol MUST be able to run over Layer 2 links between
            the end device and its External NVE.

   Req-13:  The protocol SHOULD support an end device that indicates
            that an Associate or Activate request from the end device is
            the result of a VM hot migration event.

5.  VDP Applicability and Enhancement Needs

   The Virtual Station Interface (VSI) Discovery and Configuration
   Protocol (VDP) [IEEE802.1Q] can be the control-plane protocol running
   between the hypervisor and the External NVE.  Appendix A provides
   informative VDP illustrations for the reader.

   VDP facilitates the automatic discovery and configuration of Edge
   Virtual Bridging (EVB) stations and EVB bridges.  An EVB station is
   normally an end station running multiple VMs.  In this document, it
   is considered conceptually equivalent to a hypervisor.  An EVB bridge
   is conceptually equivalent to the External NVE.

   VDP is able to pre-associate/associate/de-associate a VSI on an EVB
   station with a port on the EVB bridge.  In the context of this
   document, a VSI is conceptually approximate to a virtual port by
   which a VM connects to the hypervisor.  The EVB station and the EVB
   bridge can reach agreement on VLAN ID(s) assigned to a VSI via a VDP
   message exchange.  Other configuration parameters can be exchanged
   via VDP as well.  VDP is carried over the Edge Control Protocol (ECP)
   [IEEE802.1Q], which provides reliable transportation over a Layer 2
   network.



















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   VDP needs some extensions to fulfill the requirements listed in
   Section 4 of this document.  Table 1 shows the needed extensions
   and/or clarifications in the NVO3 context.

   +------+-----------+-----------------------------------------------+
   | Req  | Supported |                    Remarks                    |
   |      | by VDP?   |                                               |
   +------+-----------+-----------------------------------------------+
   | Req-1|           |                                               |
   +------+           |Needs extension.  Must be able to send to a    |
   | Req-2|           |specific unicast MAC, and should be able to    |
   +------+ Partially |send to a non-reserved well-known multicast    |
   | Req-3|           |address other than the nearest customer bridge |
   +------+           |address.                                       |
   | Req-4|           |                                               |
   +------+-----------+-----------------------------------------------+
   | Req-5| Yes       |The VN is indicated by GroupID.                |
   +------+-----------+-----------------------------------------------+
   | Req-6| Yes       |The bridge sends a De-Associate.               |
   +------+-----------+------------------------+----------------------+
   |      |           |VID==NULL in the request.  The bridge returns  |
   |      |           |the assigned VLAN ID (VID) value in the        |
   | Req-7| Yes       |response.  GroupID, which is optionally present|
   |      |           |in the request, is equivalent to the VN ID in  |
   |      |           |the context of NVO3.  Multiple VLANs per group |
   |      |           |are allowed.                                   |
   +------+-----------+------------------------+----------------------+
   |      |           |     Requirements       |    VDP Equivalent    |
   |      |           +------------------------+----------------------+
   | Req-8| Partially | Associate/De-Associate |Pre-Assoc/De-Associate|
   |      |           | Activate/Deactivate    |Associate/De-Associate|
   |      |           +------------------------+----------------------|
   |      |           |Needs extension to allow Associate->Pre-Assoc. |
   +------+-----------+------------------------+----------------------+
   | Req-9| Yes       |The VDP bridge initiates a De-Associate.       |
   +------+-----------+-----------------------------------------------+
   |Req-10| Partially |Needs extension for an IPv4/IPv6 address.      |
   |      |           |Add a new "filter information format" type.    |
   +------+-----------+-----------------------------------------------+
   |      |           |An out-of-band mechanism is preferred, e.g.,   |
   |      |           |MACsec or 802.1X.  Implicit authentication     |
   |Req-11| No        |based on control of physical connectivity      |
   |      |           |exists in VDP when the External NVE connects to|
   |      |           |the end device directly and is reachable with  |
   |      |           |the nearest customer bridge address.           |
   +------+-----------+-----------------------------------------------+
   |Req-12| Yes       |VDP naturally runs on the Layer 2 protocol.    |




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   +------+-----------+-----------------------------------------------+
   |      |           |A migration event may cause the M-bit to be set|
   |      |           |to 1 in the VDP request to the migration       |
   |      |           |destination hypervisor and the S-bit to be set |
   |      |           |to 1 in the VDP request to the migration source|
   |      |           |hypervisor.  However, a setting of M-bit = 0 or|
   |Req-13| Partially |S-bit = 0 can indicate that no information is  |
   |      |           |available regarding migration or that the      |
   |      |           |events in question are not caused by migration.|
   |      |           |To fully meet the requirement, this ambiguity  |
   |      |           |would need to be fixed so that migration or no |
   |      |           |migration could be safely inferred from the    |
   |      |           |M-bit or S-bit settings.                       |
   +------+-----------+-----------------------------------------------+

    Table 1: Comparison of Split-NVE Requirements and VDP Capabilities

   By simply adding the ability to carry Layer 3 addresses as per
   Req-10, VDP can provide most of the hypervisor-to-NVE control-plane
   functionality required.

6.  Security Considerations

   External NVEs must ensure that only properly authorized Tenant
   Systems are allowed to join and become a part of any particular VN.
   In some cases, the tNVE may want to connect to the nNVE for
   provisioning purposes.  This may require that the tNVE authenticate
   the nNVE in addition to the nNVE authenticating the tNVE.  If a
   secure channel is required between the tNVE and the nNVE to carry the
   encrypted Split-NVE control-plane protocol, then existing mechanisms
   such as MACsec [IEEE802.1AE] can be used.  In some deployments,
   authentication may be implicit, based on control of physical
   connectivity, e.g., if the nNVE is located in the bridge that is
   directly connected to the server that contains the tNVE.  The use of
   the "nearest customer bridge address" in VDP [IEEE802.1Q] is an
   example of where this sort of implicit authentication is possible,
   although explicit authentication also applies in that case.

   As the control-plane protocol results in configuration changes for
   both the tNVE and the nNVE, tNVE and nNVE implementations should log
   all state changes, including those described in Section 3.
   Implementations should also log significant protocol events, such as
   the establishment or loss of control-plane protocol connectivity
   between the tNVE and the nNVE, as well as authentication results.







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   In addition, External NVEs will need appropriate mechanisms to ensure
   that any hypervisor wishing to use the services of an NVE is properly
   authorized to do so.  One design point is whether the hypervisor
   should

   1.  supply the External NVE with necessary information (e.g., VM
       addresses, VN information, or other parameters) that the
       External NVE uses directly or

   2.  only supply a VN ID and an identifier for the associated VM
       (e.g., its MAC address), with the External NVE using that
       information to obtain the information needed to validate the
       hypervisor-provided parameters or obtain related parameters in a
       secure manner.

   The former approach can be used in a trusted environment so that the
   External NVE can directly use all the information retrieved from the
   hypervisor for local configuration.  It relieves the External NVE
   side of effort related to information retrieval and/or validation.
   The latter approach gives more reliable information, as the
   External NVE needs to retrieve it from a management-system database.
   In particular, some network-related parameters, such as VLAN IDs, can
   be passed back to the hypervisor to be used as a form of provisioning
   that is more authoritative.  However, in certain cases it is
   difficult or inefficient for an External NVE to be granted rights to
   access or query information on those management systems.  The
   External NVE then has to obtain the information from the hypervisor.

7.  IANA Considerations

   This document has no IANA actions.




















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8.  References

8.1.  Normative References

   [IEEE802.1Q]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Bridges and Bridged Networks", IEEE Standard
              802.1Q-2014, DOI 10.1109/IEEESTD.2014.6991462.

   [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>.

   [RFC7365]  Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
              Rekhter, "Framework for Data Center (DC) Network
              Virtualization", RFC 7365, DOI 10.17487/RFC7365,
              October 2014, <https://www.rfc-editor.org/info/rfc7365>.

   [RFC7666]  Asai, H., MacFaden, M., Schoenwaelder, J., Shima, K., and
              T. Tsou, "Management Information Base for Virtual Machines
              Controlled by a Hypervisor", RFC 7666,
              DOI 10.17487/RFC7666, October 2015,
              <https://www.rfc-editor.org/info/rfc7666>.

   [RFC8014]  Black, D., Hudson, J., Kreeger, L., Lasserre, M., and T.
              Narten, "An Architecture for Data-Center Network
              Virtualization over Layer 3 (NVO3)", RFC 8014,
              DOI 10.17487/RFC8014, December 2016,
              <https://www.rfc-editor.org/info/rfc8014>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in
              RFC 2119 Key Words", BCP 14, RFC 8174,
              DOI 10.17487/RFC8174, May 2017,
              <https://www.rfc-editor.org/info/rfc8174>.
















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8.2.  Informative References

   [IEEE802.1AE]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks: Media Access Control (MAC) Security",
              IEEE Standard 802.1AE-2006,
              DOI 10.1109/IEEESTD.2006.245590.

   [NVO3-HYPERVISOR-NVE-CP]
              Kreeger, L., Narten, T., and D. Black, "Network
              Virtualization Hypervisor-to-NVE Overlay Control Protocol
              Requirements", Work in Progress, draft-kreeger-nvo3-
              hypervisor-nve-cp-01, February 2013.

   [NVO3-TES-NVE]
              Yingjie, G. and L. Yizhou, "The mechanism and signalling
              between TES and NVE", Work in Progress, draft-gu-nvo3-tes-
              nve-mechanism-01, October 2012.

   [NVO3-VM-NVE]
              Kompella, K., Rekhter, Y., Morin, T., and D. Black,
              "Signaling Virtual Machine Activity to the Network
              Virtualization Edge", Work in Progress, draft-kompella-
              nvo3-server2nve-02, April 2013.

   [RFC2236]  Fenner, W., "Internet Group Management Protocol,
              Version 2", RFC 2236, DOI 10.17487/RFC2236, November 1997,
              <https://www.rfc-editor.org/info/rfc2236>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <https://www.rfc-editor.org/info/rfc4122>.

   [RFC7364]  Narten, T., Ed., Gray, E., Ed., Black, D., Fang, L.,
              Kreeger, L., and M. Napierala, "Problem Statement:
              Overlays for Network Virtualization", RFC 7364,
              DOI 10.17487/RFC7364, October 2014,
              <https://www.rfc-editor.org/info/rfc7364>.












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Appendix A.  VDP Illustrations (per IEEE 802.1Q) (for Information Only)

   VDP (the VSI Discovery and Discovery and Configuration Protocol; see
   Clause 41 of [IEEE802.1Q]) can be considered as a controlling
   protocol running between the hypervisor and the external bridge.  The
   VDP association TLV structure is formatted as shown in Figure 7.

   +--------+--------+------+-----+--------+------+------+------+------+
   |TLV Type|TLV Info|Status|VSI  |VSI Type|VSI ID|VSI ID|Filter|Filter|
   |        |String  |      |Type |Version |Format|      |Info  |Info  |
   |        |Length  |      |ID   |        |      |      |Format|      |
   +--------+--------+------+-----+--------+------+------+------+------+
   |                 |      |<--VSI Type and instance--->|<--Filter--->|
   |                 |      |<-------------VSI attributes------------->|
   |<--TLV header--->|<-----------TLV information string ------------->|

                       Figure 7: VDP Association TLV

   There are basically four TLV types.

   1.  Pre-Associate: The Pre-Associate is used to Pre-Associate a VSI
       instance with a bridge port.  The bridge validates the request
       and returns a failure status in the case of errors.  A successful
       Pre-Associate does not imply that the indicated VSI Type or
       provisioning will be applied to any traffic flowing through the
       VSI.  By allowing the bridge to obtain the VSI Type prior to an
       association, the Pre-Associate enables faster response to an
       Associate.

   2.  Pre-Associate with Resource Reservation: The Pre-Associate with
       Resource Reservation involves the same steps as those for the
       Pre-Associate, but on success it also reserves resources in the
       bridge to prepare for a subsequent Associate request.

   3.  Associate: The Associate request creates and activates an
       association between a VSI instance and a bridge port.  A bridge
       allocates any required bridge resources for the referenced VSI.
       The bridge activates the configuration for the VSI Type ID.  This
       association is then applied to the traffic flow to/from the VSI
       instance.

   4.  De-Associate: The De-Associate is used to remove an association
       between a VSI instance and a bridge port.  Pre-associated and
       associated VSIs can be de-associated.  The De-Associate releases
       any resources that were reserved as a result of prior Associate
       or Pre-Associate operations for that VSI instance.





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   The De-Associate can be initiated by either side, and the other types
   can only be initiated by the server side.

   Some important flag values in the VDP Status field are as follows:

   1.  M-bit (Bit 5): M-bit = 1: indicates that the user of the VSI
       (e.g., the VM) is migrating.  M-bit = 0: no indication of whether
       the VSI user is migrating.  The M-bit is used as an indicator
       relative to the VSI to which the user is migrating.

   2.  S-bit (Bit 6): S-bit = 1: indicates that the VSI user (e.g., the
       VM) is suspended.  S-bit = 0: no indication of whether the VSI
       user is suspended.  A keep-alive Associate request with S-bit = 1
       can be sent when the VSI user is suspended.  The S-bit is used as
       an indicator relative to the VSI from which the user is
       migrating.

   The filter information format currently defines four types.
   Information for each of these types is shown in detail in Figures 8
   through 11.  "PCP" stands for Priority Code Point [IEEE802.1Q].  The
   PCP value, if specified, is used by the EVB station as the default
   PCP value associated with the VSI and VID.  The filter information
   contains a PCP Significant (PS) bit associated with each PCP field,
   indicating whether the PCP field carries a PCP value (binary 1) or
   does not carry a PCP value (binary 0).

                 +----------+-------+--------+--0------+
                 | # of     | PS    | PCP    | VID     |
                 |entries   |(1 bit)|(3 bits)|(12 bits)|
                 |(2 octets)|       |        |         |
                 +----------+-------+--------+---------+
                            |<---Repeated per entry--->|

                  Figure 8: VID Filter Information Format


          +----------+--------------+-------+--------+---------+
          | # of     |  MAC address | PS    | PCP    | VID     |
          |entries   |  (6 octets)  |(1 bit)|(3 bits)|(12 bits)|
          |(2 octets)|              |       |        |         |
          +----------+--------------+-------+--------+---------+
                     |<----------Repeated per entry----------->|

                Figure 9: MAC/VID Filter Information Format







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         +----------+--------------+-------+--------+---------+
         | # of     |  GroupID     | PS    | PCP    | VID     |
         |entries   |  (4 octets)  |(1 bit)|(3 bits)|(12 bits)|
         |(2 octets)|              |       |        |         |
         +----------+--------------+-------+--------+---------+
                    |<----------Repeated per entry----------->|

             Figure 10: GroupID/VID Filter Information Format


     +----------+----------+-------------+-------+--------+---------+
     | # of     | GroupID  | MAC address | PS    | PCP    | VID     |
     |entries   |(4 octets)| (6 octets)  |(1 bit)|(3 bits)|(12 bits)|
     |(2 octets)|          |             |       |        |         |
     +----------+----------+-------------+-------+--------+---------+
                |<---------------Repeated per entry---------------->|

           Figure 11: GroupID/MAC/VID Filter Information Format

   The null VID can be used in the VDP Request sent from the station to
   the external bridge.  The null VID indicates that the set of VID
   values associated with the VSI is expected to be supplied by the
   bridge.  The set of VID values is returned to the station via the VDP
   Response.  The returned VID values can be locally significant values.
   When GroupID is used, it is equivalent to the VN ID in NVO3.  GroupID
   will be provided by the station to the bridge.  The bridge maps
   GroupID to a locally significant VLAN ID.

   The VSI ID in the VDP association TLV that identifies a VM can be in
   one of the following formats: IPv4 address, IPv6 address, MAC
   address, Universally Unique Identifier (UUID) [RFC4122], or locally
   defined.

Acknowledgements

   This document was initiated based on the merger of the following
   documents: [NVO3-HYPERVISOR-NVE-CP], [NVO3-TES-NVE], and
   [NVO3-VM-NVE].  Thanks to all the coauthors and contributing members
   of those documents.

   The authors would like to specially thank Lucy Yong and Jon Hudson
   for their generous help in improving this document.









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Authors' Addresses

   Yizhou Li
   Huawei Technologies
   101 Software Avenue
   Nanjing  210012
   China

   Phone: +86-25-56625409
   Email: liyizhou@huawei.com


   Donald Eastlake 3rd
   Huawei R&D USA
   155 Beaver Street
   Milford, MA  01757
   United States of America

   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com


   Lawrence Kreeger
   Arrcus, Inc.

   Email: lkreeger@gmail.com


   Thomas Narten
   IBM

   Email: narten@us.ibm.com


   David Black
   Dell EMC
   176 South Street
   Hopkinton, MA  01748
   United States of America

   Email: david.black@dell.com










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