Imported debug from /usr/lib/site-python/debug.pyc draft-herbert-nvo3-ila-02 - Identifier-locator addressing for IPv6
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INTERNET-DRAFT                                               Tom Herbert
Intended Status: Informational                                  Facebook
Expires: September 15, 2016                               March 14, 2016


        Identifier-locator addressing for network virtualization
                       draft-herbert-nvo3-ila-02


Abstract

   This specification describes identifier-locator addressing (ILA) in
   IPv6 for network virtualization. Identifier-locator addressing
   differentiates between location and identity of a network node. Part
   of an address expresses the immutable identity of the node, and
   another part indicates the location of the node which can be dynamic.
   Identifier-locator addressing can be used to efficiently implement
   overlay networks for network virtualization

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

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

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
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Copyright and License Notice

   Copyright (c) 2016 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



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
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   described in the Simplified BSD License.



Table of Contents

   1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1 Network virtualization . . . . . . . . . . . . . . . . . . .  5
       2.1.1 Architecture . . . . . . . . . . . . . . . . . . . . . .  5
       2.1.2 Multi-tenant virtualization  . . . . . . . . . . . . . .  6
     2.2 Data center virtualization . . . . . . . . . . . . . . . . .  6
       2.2.1 Address per task . . . . . . . . . . . . . . . . . . . .  6
       2.2.2 Job scheduling . . . . . . . . . . . . . . . . . . . . .  7
     2.3 Alternative solutions in IPv6  . . . . . . . . . . . . . . .  8
       2.3.1 Use flow label for VNID  . . . . . . . . . . . . . . . .  8
       2.3.2 Using an extension header  . . . . . . . . . . . . . . .  8
   3 Address formats  . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.1 ILA format . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2 Identifier format  . . . . . . . . . . . . . . . . . . . . . 10
     3.3 Identifier types . . . . . . . . . . . . . . . . . . . . . . 11
     3.4 Interface identifiers  . . . . . . . . . . . . . . . . . . . 11
     3.5 Locally unique identifiers . . . . . . . . . . . . . . . . . 11
     3.6 Virtual networking identifiers for IPv4  . . . . . . . . . . 12
     3.7 Virtual networking identifiers for IPv6  . . . . . . . . . . 12
       3.7.1 Virtual networking identifiers for IPv6 unicast  . . . . 12
       3.7.2 Virtual networking identifiers for IPv6 multicast  . . . 13
     3.8 Standard identifier representation addresses . . . . . . . . 14
       3.8.1 SIR for locally unique identifiers . . . . . . . . . . . 15
       3.8.2 SIR for virtual addresses  . . . . . . . . . . . . . . . 15
     3.9 Locators . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   4 Operation  . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     4.1 Identifier to locator mapping  . . . . . . . . . . . . . . . 17
     4.2 Address translations . . . . . . . . . . . . . . . . . . . . 17
       4.2.1 SIR to ILA address translation . . . . . . . . . . . . . 17
       4.2.2 ILA to SIR address translation . . . . . . . . . . . . . 18
     4.3 Virtual networking operation . . . . . . . . . . . . . . . . 18
       4.3.1 Crossing virtual networks  . . . . . . . . . . . . . . . 18
       4.3.2 IPv4/IPv6 protocol translation . . . . . . . . . . . . . 19
     4.4 Transport layer checksums  . . . . . . . . . . . . . . . . . 19
       4.4.1 Checksum-neutral mapping . . . . . . . . . . . . . . . . 19
       4.4.2 Sending an unmodified checksum . . . . . . . . . . . . . 21



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     4.5 Address selection  . . . . . . . . . . . . . . . . . . . . . 21
     4.6 SIR address routing  . . . . . . . . . . . . . . . . . . . . 21
     4.7 Duplicate identifier detection . . . . . . . . . . . . . . . 22
   5. Communication scenarios . . . . . . . . . . . . . . . . . . . . 22
     5.1 Terminology  . . . . . . . . . . . . . . . . . . . . . . . . 22
     5.2 Identifier objects . . . . . . . . . . . . . . . . . . . . . 23
     5.3 Reference network for scenarios  . . . . . . . . . . . . . . 24
     5.4 Scenario 1: Task to task . . . . . . . . . . . . . . . . . . 25
     5.5 Scenario 2: Task to Internet . . . . . . . . . . . . . . . . 25
     5.6 Scenario 3: Internet to task . . . . . . . . . . . . . . . . 25
     5.7 Scenario 4: TS to service task . . . . . . . . . . . . . . . 26
     5.8 Scenario 5: Task to TS . . . . . . . . . . . . . . . . . . . 26
     5.9 Scenario 6: TS to Internet . . . . . . . . . . . . . . . . . 26
     5.10 Scenario 7: Internet to TS  . . . . . . . . . . . . . . . . 26
     5.11 Scenario 8: IPv4 TS to service  . . . . . . . . . . . . . . 27
     5.12 TS to TS in the same virtual network  . . . . . . . . . . . 28
       5.12.1 Scenario 9: TS to TS in same VN using IPV6  . . . . . . 28
       5.12.2 Scenario 10: TS to TS in same VN using IPv4 . . . . . . 28
     5.13 TS to TS in a different virtual networks  . . . . . . . . . 28
       5.13.1 Scenario 11: TS to TS in a different VNs using IPV6 . . 28
       5.13.2 Scenario 12: TS to TS in a different VNs using IPv4 . . 28
       5.13.3 Scenario 13: IPv4 TS to IPv6 TS in different VNs  . . . 29
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 29
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 30
   8  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     8.1  Normative References  . . . . . . . . . . . . . . . . . . . 30
     8.2  Informative References  . . . . . . . . . . . . . . . . . . 30
   9 Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . 31
   Appendix A: Task identifier generation . . . . . . . . . . . . . . 31
     A.1 Globally unique identifiers method . . . . . . . . . . . . . 31
     A.2 Universally Unique Identifiers method  . . . . . . . . . . . 33
   Appendix B: Task migration considerations  . . . . . . . . . . . . 33
     B.1 Address migration  . . . . . . . . . . . . . . . . . . . . . 33
     B.2 Connection migration . . . . . . . . . . . . . . . . . . . . 34

1 Introduction

   This specification describes the data path, address formats, and
   expected use cases of identifier-locator addressing in IPv6
   ([RFC2460]). The Identifier-Locator Network Protocol (ILNP)
   ([RFC6740], [RFC6741]) defines a protocol and operations model for
   identifier-locator addressing in IPv6. Many concepts here are taken
   from ILNP, however there are some differences in the context of
   network virtualization-- for instance in ILA a method to encode a
   virtual network identifier and virtual address within an identifier
   is defined.

   In identifier-locator addressing, an IPv6 address is split into a



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   locator and an identifier component. The locator indicates the
   topological location in the network for a node, and the identifier
   indicates the node's identity which refers to the logical or virtual
   node in communications. Locators are routable within a network, but
   identifiers typically are not. An application addresses a destination
   by identifier. Identifiers are mapped to locators for transit in the
   network. The on-the-wire address is composed of a locator and an
   identifier: the locator is sufficient to route the packet to a
   physical host, and the identifier allows the receiving host to
   forward the packet to the addressed application.

   Identifiers are not statically bound to a host on the network, and in
   fact their binding (or location) may change. This is the basis for
   network virtualization and address migration. An identifier is mapped
   to a locator at any given time, and a set of identifier to locator
   mappings is propagated throughout a network to allow communications.
   The mappings are kept synchronized so that if an identifier migrates
   to a new physical host, its identifier to locator mapping is updated.

   In network virtualization, an identifier may further be split into a
   virtual network identifier and virtual host address. With identifier-
   locator addressing network virtualization can be implemented in an
   IPv6 network without any additional encapsulation headers. Packets
   sent with identifier-locator addresses look like plain unencapsulated
   packets (e.g. TCP/IP packets). This "encapsulation" is transparent to
   the network, so protocol specific mechanisms in network hardware work
   seamlessly. These mechanisms include hash calculation for ECMP, NIC
   large segment offload, checksum offload, etc.

   ILA exhibits properties of different networking techniques:

      o Network Address Translation

      o Source routing

      o Encapsulation















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2 Motivation

   This section highlights the motivation for identifier-locator
   addressing.

2.1 Network virtualization

   Identifier-locator addressing allows a data plane method to implement
   network virtualization without encapsulation and its related
   overheads. The service ILA provides is explicitly layer 3 over layer
   3 network virtualization (IPv4 or IPv6 over IPv6).

2.1.1 Architecture

   The architecture for Network Virtualization over Layer 3 ([NVO3ARCH])
   can be applied to network virtualization with ILA.

    +--------+                                             +--------+
    | Tenant +--+                                     +----| Tenant |
    | System |  |                                    (')   | System |
    +--------+  |          ................         (   )  +--------+
                |  +-+--+  .              .  +--+-+  (_)
                |  | NVE|--.              .--| NVE|   |
                +--|    |  .              .  |    |---+
                   +-+--+  .              .  +--+-+
                   /       .              .
                  /        . Ipv6 Overlay .   +--+-++--------+
    +--------+   /         .    Network   .   | NVE|| Tenant |
    | Tenant +--+          .              .- -|    || System |
    | System |             .              .   +--+-++--------+
    +--------+             ................

   A Network Virtualization Edge (NVE) [RFC7365] is the entity that
   implements the overlay functionality using ILA.  An NVE resides at
   the boundary between a Tenant System and the IPV6 overlay network as
   shown above. An NVE creates and maintains local state about each
   Virtual Network for which it is providing service on behalf of a
   Tenant System.

   As in traditional network virtualization, NVEs are responsible for
   transit of tenant's packets through the overlay network. With ILA,
   the NVEs perform address translation on packets as opposed to
   encapsulation. The ingress NVE will translate the virtual address of
   a destination to an ILA address. At the egress NVE, the reverse
   translation is performed.






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2.1.2 Multi-tenant virtualization

   Identifier-locator addressing may be used as an alternative to nvo3
   encapsulation protocols (such as GUE [GUE]). In multi-tenant
   virtualization, overlay networks are established for various tenants
   to create virtual networks and a tenant's nodes are assigned virtual
   addresses. Virtual networking identifiers are used to encode a
   virtual network identifier and a virtual address in an ILA address.

   An advantage of identifier-locator addressing is that the overhead of
   encapsulation is reduced and use of virtualization can be transparent
   to the underlying network. A downside is that some features that use
   additional data in an encapsulation aren't available (security option
   in GUE for instance [GUESEC]).

   Identifier-locator addressing may be appropriate in network
   virtualization where the users are trusted, for instance if virtual
   networks were assigned to different departments within an enterprise.
   Network virtualization in this context provides a means of isolation
   of traffic belonging to different departments of a single tenant. In
   this scenario, if the isolation breaks and packets unintentionally
   crosses between virtual networks, it would not be considered a
   security risk.

2.2 Data center virtualization

   A primary motivation for identifier-locator addressing is data center
   virtualization. Virtualization within a data center permits
   malleability and flexibility in using data center resources. In
   particular, identifier-locator addressing virtualizes networking to
   allow flexible job scheduling and possibility of live task migration.

2.2.1 Address per task

   Managing the port number space for services within a data center is a
   nontrivial problem. When a service task is created, it may run on
   arbitrary hosts. The typical scenario is that the task will be
   started on some machine and will be assigned a port number for its
   service. The port number must be chosen dynamically to not conflict
   with any other port numbers already assigned to tasks on the same
   machine (possibly even other instances of the same service). A
   canonical name for the service is entered into a database with the
   host address and assigned port. When a client wishes to connect to
   the service, it queries the database with the service name to get
   both the address of an instance as well as its port number. Note that
   DNS is not adequate for the service lookup since it does not provide
   port numbers.




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   With ILA, each service task can be assigned its own IPv6 address and
   therefore will logically be assigned the full port space for that
   address. This a dramatic simplification since each service can now
   use a publicly known port number that does not need to unique between
   services or instances. A client can perform a lookup on the service
   name to get an IP address of an instance and then connect to that
   address using a well known port number. In this case, DNS is
   sufficient for directing clients to instances of a service.

   Algorithms for the creation of unique address per task are described
   in Appendix A.

2.2.2 Job scheduling

   In the usual data center model, jobs are scheduled to run as tasks on
   some number of machines. A distributed job scheduler provides the
   scheduling which may entail considerable complexity since jobs will
   often have a variety of resource constraints. The scheduler takes
   these constraints into account while trying to maximize utility of
   the data center in terms utilization, cost, latency, etc. Data center
   jobs do not typically run in virtual machines (VMs), but may run
   within containers. Containers are mechanisms that provide resource
   isolation between tasks running on the same host OS. These resources
   can include CPU, disk, memory, and networking.

   A fundamental problem arises in that once a task for a job is
   scheduled on a machine, it often needs to run to completion. If the
   scheduler needs to schedule a higher priority job or change resource
   allocations, there may be little recourse but to kill tasks and
   restart them on a different machine. In killing a task, progress is
   lost which results in increased latency and wasted CPU cycles. Some
   tasks may checkpoint progress to minimize the amount of progress
   lost, but this is not a very transparent or general solution.

   An alternative approach is to allow transparent job migration. The
   scheduler may migrate running jobs from one machine to another.

   Under the orchestration of the job scheduler, the steps to migrate a
   job may be:

      1) Stop running tasks for the job.
      2) Package the runtime state of the job. The runtime state is
         derived from the containers for the jobs.
      3) Send the runtime state of the job to the new machine where the
         job is to run.
      4) Instantiate the job's state on the new machine.
      5) Start the tasks for the job continuing from the point at which
         it was stopped.



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   This model similar to virtual machine (VM) migration except that the
   runtime state is typically much less data-- just task state as
   opposed to a full OS image. Task state may be compressed to reduce
   latency in migration.

   The networking state of interest to migrate are the addresses used by
   the task and open transport connections. The handling of these at
   task migration is discussed in Appendix B.

2.3 Alternative solutions in IPv6

   A few alternative solutions have been proposed to provide network
   virtualization without encapsulation in IPv6.

2.3.1 Use flow label for VNID

   The IPv6 flow label could be used as a 20-bit Virtual Network
   Identifier. In this model the addresses may be virtual address within
   the specified virtual network. Presumably, the flow-label/addresses
   could be used by switches to forward virtually addressed packets.
   This has some issues:

      o Forwarding virtual packets to their physical location would
        require specialized switch support.

      o The flow label is only twenty bits, this is too small to be a
        discriminator in forwarding a virtual packet to a specific
        destination. Conceptually, the flow label might be used in a
        type of label switching to solve that.

      o The flow label is not considered immutable in transit,
        intermediate devices may change it.

      o The flow label is not part of the pseudo header for transport
        checksum calculation, so it is not be covered by any transport
        (or other) checksums.

2.3.2 Using an extension header

   To accomplish network virtualization an extension header, probably as
   a destination option, could be used that contains the virtual
   (destination) address of a packet. The destination address in the
   IPv6 header would be the physical address for the location of the
   virtual node.

   This technique also has some issues:

      o Intermediate devices must not insert extension headers



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        [RFC2460bis]. This would preclude using extension headers in an
        NVE that is not co-located with a source host.

      o Extension headers introduce additional packet overhead which may
        impact performance.

      o Extension headers are not covered by transport checksums (as the
        address would be) nor any other checksum.

      o Extension headers are not widely supported in network hardware
        or devices. For instance, several NIC offloads don't work in the
        presence of extension headers

3 Address formats

   This section describes the address formats associated with
   identifier-locator addressing in network virtualization.

3.1 ILA format

   As described in ILNP ([RFC6741]) an IPv6 address may be encoded to
   hold a locator and identifier where each occupies sixty-four bits. In
   ILA, the upper three bits of the identifier indicate an identifier
   type. The fourth upper bit of the identifier, the C bit, is used to
   indicate that checksum-neutral mapping has been done (see section
   4.4).

   The IPv6 canonical address format is:

     |            64 bits             |             64 bits           |
     +--------------------------------+-------------------------------+
     |   IPv6 Unicast Routing Prefix  |      Interface Identifier     |
     +--------------------------------+-------------------------------+

   The address format using ILA is:

     |            64 bits             |3 bits|1|     60 bits          |
     +--------------------------------+-------------------------------+
     |             Locator            | Type |C|    Identifier        |
     +----------------------------------------------------------------+











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   An IPv6 header with an ILA address would then have the format:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Version| Traffic Class |           Flow Label                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Payload Length       |   Next Header |  Hop Limit    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Source Address                         |
     +                                                               +
     |                                                               |
     +                                                               +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Destination Locator                       |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Type |C|               Destination Identifier                  |
     +-+-+-+-+                                                       +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.2 Identifier format

   The format of an ILA identifier is:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type|C|                    Identifier                         |
     +-+-+-+-+                                                       |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      o Type: Type of the identifier (see section 3.3).

      o C: Checksum-neutral mapping applied

      o Identifier: Identifier value.

   If the C-bit is set the low order 16-bits of an identifier contain
   the adjustment for checksum-neutral mapping. The format of an
   identifier with checksum neutral mapping is:




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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type|1|                    Identifier                         |
     +-+-+-+-+                       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |  Checksum-neutral adjustment  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.3 Identifier types

   Defined identifier types are:

      0: interface identifier

      1: locally unique identifier

      2: virtual networking identifier for IPv4 address

      3: virtual networking identifier for IPv6 unicast address

      4: virtual networking identifier for IPv6 multicast address

      5-7: Reserved

3.4 Interface identifiers

   The interface identifier type indicates a plain local scope interface
   identifier. When this type is used the address is a normal IPv6
   address without identifier-locator semantics. The pupose of this type
   is to allow normal IPv6 addresses to be defined within the same
   networking prefix as ILA addresses. The type bits and C-bit must be
   zero, and the format of the other bits (subnetting) would be site-
   defined. For example, the format of an interface identifier might be:

      /* Local scope interface identifier */
      |         64 bits            |3 bits|1|       60 bits           |
      +----------------------------+------+---------------------------+
      |          Prefix            |  0x0 |0|         IID             |
      +---------------------------------------------------------------+

3.5 Locally unique identifiers

   Locally unique identifiers (LUI) can be created for various
   addressable nodes within a network. These identifiers are in a flat
   sixty bit space and must be unique within a domain (unique within a
   site for instance). To simplify administration, hierarchical
   allocation of locally unique identifiers may be performed.




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      /* ILA with locally unique identifiers */
      |         64  bits           |3 bits|1|        60 bits          |
      +----------------------------+------+---------------------------+
      |          Locator           |  0x1 |C| Locally unique ident.   |
      +---------------------------------------------------------------+

3.6 Virtual networking identifiers for IPv4

   This type defines a format for encoding an IPv4 virtual address and
   virtual network identifier within an identifier.

      /* ILA for IPv4 virtual networking */
      |         64 bits            |3 bits|1| 28 bits     |   32 bits |
      +----------------------------+------+---------------+-----------+
      |          Locator           |  0x2 |C|  VNID       |   VADDR   |
      +---------------------------------------------------------------+

   VNID is a virtual network identifier and VADDR is a virtual address
   within the virtual network indicated by the VNID. The VADDR can be an
   IPv4 unicast or multicast address, and may often be in a private
   address space (i.e. [RFC1918]) used in the virtual network.

3.7 Virtual networking identifiers for IPv6

   A virtual network identifier and an IPv6 virtual host address (tenant
   visible address) can be encoded within an identifier. Encoding the
   virtual host address involves mapping the 128 bit address into a
   sixty bit identifier. Different encodings are used for unicast and
   multicast addresses.

3.7.1 Virtual networking identifiers for IPv6 unicast

   In this format, the virtual network identifier and virtual IPv6
   unicast address are encoded within an identifier. To facilitate
   encoding of virtual addresses, there is a unique mapping between a
   VNID and a ninety-six bit prefix of the virtual address.

      /* IPv6 unicast encoding with VNID in ILA */
      |           64 bits            |3 bits|1| 28 bits    |  32 bits  |
      +------------------------------+------+--------------+-----------+
      |            Locator           |  0x3 |C|  VNID      |  VADDR6L  |
      +----------------------------------------------------------------+

   VADDR6L contains the low order 32 bits of the IPv6 virtual address.
   The upper 96 bits of the virtual address inferred from the VNID to
   prefix mapping.

   The figure below illustrates encoding a tenant IPv6 virtual unicast



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   address into a ILA address.

      /* IPv6 virtual address seen by tenant */
      +----------------------------------------------+-----------------+
      |            Tenant prefix                     |  VADDR6L        |
      +-----------------------+-------------------------------+--------+
                              |                               |
                              +-prefix to VNID-+              |
                                               |              |
                                               v              v
      +---------------------------+------+-----------+-----------------+
      |            Locator        |  0x3 |C| VNID    |  VADDR6L        |
      +----------------------------------------------------------------+
      /* Encoded IPv6 virtual address with VNID in ILA */

   This encoding is reversible, given an ILA address, the virtual
   address visible to the tenant can be deduced:

      /* ILA encoded virtual networking address */
      +---------------------------+------+-----------+-----------------+
      |            Locator        |  0x3 |C| VNID    |  VADDR6L        |
      +----------------------------------------+-----------------------+
                                               |              |
                              +-VNID to prefix-+              |
                              |                               |
                              v                               v
      +----------------------------------------------+-----------------+
      |            Tenant prefix                     |  VADDR6L        |
      +----------------------------------------------------------------+
      /* IPv6 virtual address seen by tenant */

3.7.2 Virtual networking identifiers for IPv6 multicast

   In this format, a virtual network identifier and virtual IPv6
   multicast address are encoded within an identifier.

      /* IPv6 multicast address with VNID encoding in ILA */
      |         64 bits          |3 bits|1|28 bits   |4 bits| 28 bits  |
      +--------------------------+------+------------------------------+
      |          Locator         |  0x4 |C|  VNID    |Scope |  MADDR6L |
      +----------------------------------------------------------------+

   This format encodes an IPv6 multicast address in an identifier. The
   scope indicates multicast address scope as defined in [RFC7346].
   MADDR6L is the low order 28 bits of the multicast address. The full
   multicast address is thus:

     ff0<Scope>::0<MADDRL6 high 12 bits>:<MADDRL6 low 16 bits>



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   And so can encode multicast addresses of the form:

     ff0X::0 to ff0X::0fff:ffff

   The figure below illustrates encoding a tenant IPv6 virtual multicast
   address into an ILA address.

      /* IPv6 multicast address */
      | 12 bits | 4 bits|        84 bits                    | 28 bits  |
      +---------+-------+-----------------------------------+----------+
      |  0xfff  | Scope |           0's                     |  MADDR6L |
      +-------------+---------------------------------------------+----+
                    |                                             |
                    +------------------------------------+        |
                                                         |        |
                                                         v        v
      +--------------------------+------+------------------------------+
      |          Locator         |  0x4 |C|  VNID    |Scope |  MADDR6L |
      +----------------------------------------------------------------+
      /* IPv6 multicast address with VNID encoding in ILA */

3.8 Standard identifier representation addresses

   An identifier serves as the external representation of a network
   node. For instance, an identifier may refer to a specific host,
   virtual machine, or tenant system. When a host initiates a connection
   or sends a packet, it uses the identifier to indicate the peer
   endpoint of the communication. The endpoints of an established
   connection context also referenced by identifiers. It is only when
   the packet is actually being sent over a network that the locator for
   the identifier needs to be resolved.

   In order to maintain compatibility with existing networking stacks
   and applications, identifiers are encoded in IPv6 addresses using a
   standard identifier representation (SIR) address. A SIR address is a
   combination of a prefix which occupies what would be the locator
   portion of an ILA address, and the identifier in its usual location.

      /* SIR address in IPv6 */
      |            64 bits             |3 bits|1|       60 bits        |
      +--------------------------------+-------------------------------+
      |           SIR prefix           | Type |0|      Identifier      |
      +----------------------------------------------------------------+

   Note that the C-bit (checksum-neutral translation) is always 0 for a
   SIR address.

   A SIR prefix may be site-local, or globally routable. A globally



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   routable SIR prefix facilitates connectivity between hosts on the
   Internet and ILA endpoints. A gateway between a site's network and
   the Internet can translate between SIR prefix and locator for an
   identifier. A network may have multiple SIR prefixes where each
   prefix defines a unique identifier space.

   Locators must only be associated with one SIR prefix. This ensures
   that if a translation from a SIR address to an ILA address is
   performed when sending a packet, the reverse translation at the
   receiver yields the same SIR address that was seen at the
   transmitter. This also ensures that a reverse checksum-neutral
   translation can be performed at a receiver to restore the addresses
   that were included in a pseudo header for setting a transport
   checksum.

   The standard identifier representation address can be used as the
   externally visible address for a node. This can used throughout the
   network, returned in DNS AAAA records ([RFC3363]), used in logging,
   etc. An application can use a SIR address without knowledge that it
   encodes an identifier.

3.8.1 SIR for locally unique identifiers

   The SIR address for a locally unique identifier has format:

      /* SIR address with locally unique identifiers */
      |            64  bits            |3 bits|1|       60 bits        |
      +--------------------------------+-------------------------------+
      |           SIR prefix           |  0x1 |0|Locally unique ident. |
      +----------------------------------------------------------------+

   When using ILA with locally unique identifiers a flow tuple logically
   has the form:

     (source address, source port,
      destination identifier, destination port)

   Using standard identifier representation the flow is then represented
   with IPv6 addresses:

      (source address, source port,
       destination SIR address, destination port)

3.8.2 SIR for virtual addresses

   An ILA virtual address may be encoded using the standard identifier
   representation. For example, the SIR address for an IPv6 virtual
   address may be:



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      /* SIR with IPv6 virtual network encoding */
      |           64 bits            |3 bits|1| 28 bits   |  32 bits   |
      +------------------------------+------+-------------+------------+
      |          SIR prefix          |  0x3 |0|   VNID    |  VADDRL6   |
      +----------------------------------------------------------------+

   In a tenant system, a flow tuple would have the form:

     (local VADDR, local port, remote VADDR, remote port)

   After translating packets for the flow into ILA, the flow would be
   identified on-the-wire as:

     ((local VNID, local VADDR), local port,
      (remote VNID, remote VADDR), remote port

   A tenant may communicate with a peer in the network which is not in
   its virtual network, for instance to reach a network service (see
   section 5). In this case the flow tuple at the peer may be:

     (local address, local port,
      remote SIR address, remote port)

   In this example, the remote SIR address is a SIR address for a
   virtual networking identifier, however from peer's connectivity
   perspective this is not distinguishable from a SIR address with a
   locally unique identifier or even a non-ILA address.

3.9 Locators

   Locators are routable network address prefixes that address physical
   hosts within the network. They may be assigned from a global address
   block [RFC3587], or be based on unique local IPv6 unicast addresses
   as described in [RFC4193].

      /* ILA with a global unicast locator */
      |<--------------- Locator --------------->|
      |3 bits| N bits        | M bits  | 61-N-M | 64 bits              |
      +------+-------------+---------+---------------------------------+
      | 001  | Global prefix | Subnet  | Host   |      Identifier      |
      +------+---------------+---------+--------+----------------------+

      /* ILA with a unique local IPv6 unicast locator */
      |<--------------- Locator --------->|
      | 7 bits |1|  40 bits   |  16 bits  |          64 bits           |
      +--------+-+------------+-----------+----------------------------+
      | FC00   |L| Global ID  | Host      |        Identifier          |
      +--------+-+------------+-----------+----------------------------+



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4 Operation

   This section describes operation methods for using identifier-locator
   addressing with network virtualization.

4.1 Identifier to locator mapping

   An application initiates a communication or flow using a SIR address
   or virtual address for a destination. In order to send a packet on
   the network, the destination identifier is mapped to a locator. The
   mappings are not expected to change frequently, so it is likely that
   locator mappings can be cached in the flow contexts.

   Identifier to locator mapping is nearly identical to the mechanism
   needed in virtual networking to map a virtual network and virtual
   host address to a physical host. These mechanisms should leverage a
   common solution.

   The mechanisms of propagating and maintaining identifier to locator
   mappings are outside the scope of this document.

4.2 Address translations

   With ILA, address translation is performed to convert SIR addresses
   to ILA addresses, and ILA addresses to SIR addresses. Translation is
   done on a destination address as a form of source routing.

4.2.1 SIR to ILA address translation

   When transmitting a packet, the locator for the destination ILA
   address might need to be set before the packet is sent on the wire.
   In the case that packet was created using a standard identifier
   representation, the SIR prefix is overridden with a locator. Since
   this operation is potentially done for every packet the process
   should be very efficient. Presumably, a host will maintain a cache of
   identifier locator mappings with a fast lookup function. If there is
   a connection state associated with the communication, the locator
   information may be cached with the connection state to obviate the
   need to perform a lookup per packet.

   The typical steps to transmit a packet using ILA are:

      1) Host stack creates a packet with source address set to a local
         address (possibly a SIR address) for the local identity, and
         the destination address is set to the SIR address for the peer.
         The peer SIR address may have been discovered through DNS or
         other means.




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      2) An NVE overwrites the SIR prefix in the destination address
         with a locator for the peer. This locator is discovered by a
         lookup in the locator to identifier mappings.

      3) The NVE peforms checksum-neutral mapping if configured for that
         (section 4.4).

      4) Packet is forwarded on the wire. The network routes the packet
         to the host indicated by the locator.

4.2.2 ILA to SIR address translation

   Upon reception, an ILA address must be translated back to a SIR
   address before upper layer processing.

   Receive processing may be:

      1) Packet is received, the destination locator matches an
         interface address prefix on the host.

      2) A lookup is performed on the destination identifier to find if
         it addresses a local identifier. If match is found, a SIR
         address can be created for the destination (overwrite locator
         with a SIR prefix).

      3) Perform reverse checksum-neutral mapping if C-bit is set
         (section 4.4).

      4) Perform any checks as necessary. Validate locators,
         identifiers, and check that packet is not illegitimately
         crossing virtual networks (see below).

      5) Forward packet to application processing. If necessary, the
         addresses in the packet can be converted to SIR addresses in
         place.

4.3 Virtual networking operation

   When using ILA with virtual networking identifiers, address
   translation is performed to convert tenant virtual network and
   virtual addresses to ILA addresses, and ILA addresses back to a
   virtual network and tenant's virtual addresses. Translation may occur
   on either source address, destination address, or both (see scenarios
   for virtual networking in section 5). Address translation is
   performed similar to the SIR translation cases described above.

4.3.1 Crossing virtual networks




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   With explicit configuration, virtual network hosts may communicate
   directly with virtual hosts in another virtual network by using ILA
   addresses for virtualization in both the source and destination
   addresses. This might be done to allow services in one virtual
   network to be accessed from another (by prior agreement between
   tenants).

4.3.2 IPv4/IPv6 protocol translation

   An IPv4 tenant may send a packet that is converted to an IPv6 packet
   with ILA addresses having IPv4 virtual networking identifiers.
   Similarly, an IPv6 packet with ILA addresses may be converted to an
   IPv4 packet to be received by an IPv4-only tenant. These are
   IPv4/IPv6 stateless protocol translations as described in [RFC6144]
   and [RFC6145].

4.4 Transport layer checksums

   Packets undergoing ILA translation may include transport layer
   checksums (e.g. TCP or UDP) that include a pseudo header that is
   affected by the translation.

   ILA provides two alternatives do deal with this:

      o Perform a checksum-neutral mapping by performing a complementary
        change modification to a different 16-bit field covered by the
        checksum (as described in [RFC6296]).

      o Send the checksum as-is, that is send the checksum value based
        on the pseudo header before translation.

   Some intermediate devices that are not the actual end point of a
   transport protocol may attempt to validate transport layer checksums.
   In particular, many Network Interface Cards (NICs) have offload
   capabilities to validate transport layer checksums (including any
   pseudo header) and return a result of validation to the host.
   Typically, these devices will not drop packets with bad checksums,
   they just pass a result to the host. Checksum offload is a
   performance benefit, so if packets have incorrect checksums on the
   wire this benefit is lost. With this incentive, applying a checksum-
   neutral translation is the recommended alternative. If it is known
   that the addresses of a packet are not included in a transport
   checksum, for instance a GRE packet is being encapsulated, then a
   source may choose not to perform checksum-neutral mapping.

4.4.1 Checksum-neutral mapping

   When a change is made to one of the IP header fields in the IPv6



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   pseudo-header checksum (such as one of the IP addresses), the
   checksum field in the transport layer header may become invalid.
   Fortunately, an incremental change in the area covered by the
   Internet standard checksum [RFC1071] will result in a well-defined
   change to the checksum value [RFC1624].  So, a checksum change caused
   by modifying part of the area covered by the checksum can be
   corrected by making a complementary change to a different 16-bit
   field covered by the same checksum.

   ILA performs a checksum-neutral mapping when a SIR prefix is
   translated to a locator in an IPv6 address, and performs the reverse
   mapping when translating a locator back to a SIR prefix. The low
   order sixteens bits of the identifier contain the offset to produce a
   checksum-neutral translation in ILA.

   On transmission, the translation process is:

      1) Compute the one's complement difference between the SIR prefix
         and the locator. Fold this value to 16 bits (add-with-carry
         four 16-bit words of the difference).

      2) Add-with-carry the bit-wise not of the 0x1000 (i.e. 0xefff) to
         the value from #1. This compensates the checksum for setting
         the C-bit.

      3) Add-with-carry the bit-wise not of the value from #2 to the low
         order sixteen bits of the identifier.

      4) Set the resultant value from #3 in the low order sixteen bits
         of the identifier and set the C-bit.

   Note that the "adjustment" (the 16-bit value set in the identifier in
   set #3) is fixed for a given SIR to locator mapping, so the
   adjustment value can be saved in an associated data structure for a
   mapping and does not need to be computed for each translation.

   On reception, if the C-bit is set in an ILA address:

      1) Compute the one's complement difference between the locator in
         the address and the SIR prefix that the locator is being
         translated to. Fold this value to 16 bits (add-with-carry four
         16-bit words of the difference).

      2) Add-with-carry 0x1000 to the value from #1. This compensates
         the checksum for clearing the C-bit.

      3) Add-with-carry the bit-wise not of the value from #2 to the low
         order sixteen bits of the identifier.



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      4) Set the resultant value from #3 in the low order sixteen bits
         of the identifier and clear the C-bit. This restores the
         original identifier sent in the packet.

4.4.2 Sending an unmodified checksum

   When sending an unmodified checksum, the checksum is technically
   incorrect as viewed in the packet on the wire. At the receiver, ILA
   translation of the destination ILA address back to the SIR address
   occurs before transport layer processing. In this way when the
   transport layer validates the checksum the pseudo header is based on
   that of the orignal used to set the checksum. As mentioned above,
   intermediate devices are not expected to drop packets due to a bad
   transport layer checksum.

4.5 Address selection

   There may be multiple possibilities for creating either a source or
   destination address. A node may be associated with more than one
   identifier, and there may be multiple locators for a particular
   identifier. The selection of an identifier occurs at flow creation
   and must be invariant for the duration of the flow. Locator selection
   should be done once per flow, however may change (in the case of a
   migrating connection it will change). ILA address selection should
   follow guidelines in Default Address Selection for Internet Protocol
   Version 6 (IPv6) ([RFC6724]).

4.6 SIR address routing

   ILA is intended to be sufficiently lightweight so that all the hosts
   in a data center could potentially send and receive ILA addressed
   packets. In order to scale this model and allow for hosts that do not
   participate in ILA, a routing topology may be applied. A simple
   topology is illustrated below.

                               +---+-+---+-+
      (1) Default SIR route    |ILA router |
            +->->->->->->->->->|           |->->->->-+
            |                  +---+-+---+-+         |
            ^                      . (2) ILA         V
            |                      .   redirect      |
       +--------++--+--+           .              +--+--++--------+
       |        ||     |<...........              |     ||        |
       |   Host || NVE |                          | NVE || Host   |
       |        ||     |->->->->->->->->->->->->->|     ||        |
       +--------++--+--+     (3) Direct route     +--+--++--------+

   An ILA router is a node that implements both NVE and NVA (Network



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   Virtualization Authority). Packets sent with a destination SIR
   address are routed to an ILA router (the SIR prefixes may "anycast"
   address prefixes to facilitate this routing). When an ILA router
   receives a SIR addressed packet it will perform the ILA translation
   and send the ILA addressed packet to the destination NVE.

   Host NVEs might not be initialized with ILA identifier to locator
   mappings. When a host sends a SIR addressed packet, the packet is
   routed to an ILA router based on the SIR prefix. The ILA router
   provides ILA translation for the SIR prefix (this is shown in (1)
   above). In addition to forwarding the ILA packet, the ILA router may
   send an "ILA redirect" back to the source (at (2) above). The
   redirect indicates the locator to use for the associated identifier.
   Subsequently, the NVE at the source host can perform ILA translation
   to send directly to the destination NVE thus eliminating triangular
   routing (as shown in (3)). The specification of the ILA redirect
   message is outside the scope of this document.

4.7 Duplicate identifier detection

   As part of implementing the locator to identifier mapping, duplicate
   identifier detection may be implemented in a centralized control
   plane. A registry of identifiers could be maintained (possibly in
   association the identifier to locator mapping database). When a node
   creates an identifier it registers the identifier, and when the
   identifier is no longer in use (e.g. task completes) the identifier
   is unregistered. The control plane should able to detect a
   registration attempt for an existing identifier and deny the request.

5. Communication scenarios

   This section describes the use of identifier-locator addressing in
   several scenarios.

5.1 Terminology

   A formal notation for identifier-locator addressing with ILNP is
   described in [RFC6740]. We extend this to include for network
   virtualization cases.

   Basic terms are:

      A = IP Address
      I = Identifier
      L = Locator
      LUI = Locally unique identifier
      VNI = Virtual network identifier
      VA  = An IPv4 or IPv6 virtual address



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      VAX = An IPv6 networking identifier (IPv6 VA mapped to VAX)
      SIR = Prefix for standard identifier representation
      VNET = IPv6 prefix for a tenant (assumed to be globally routable)
      Iaddr = IPv6 address of an Internet host

   An ILA IPv6 address is denoted by

     L:I

   A transport endpoint IPv6 address with a locally unique identifier
   with SIR prefix is denoted by

     SIR:LUI

   A virtual identifier with a virtual network identifier and a virtual
   IPv4 address is denoted by

     VNI:VA

   An ILA IPv6 address with a virtual networking identifier for IPv4
   would then be denoted

     L:(VNI:VA)

   The local and remote address pair in a packet or endpoint is denoted

     A,A

   An address translation sequence from transport visible addresses to
   ILA addresses for transmission on the network and back to transport
   endpoint addresses at the receiver has notation:

     A,A -> L:I,A -> A,A

5.2 Identifier objects

   Identifier-locator addressing is broad enough in scope to address
   many different types of networking objects within a data center. For
   descriptive purposes we classify these objects as tasks or tenant
   systems.

   A task is a unit of execution that runs in the data center networks.
   These do not run in a virtual machine, but typically run in the
   native host context perhaps within containers. Tasks are the
   execution mechanism for native jobs in the data center.

   A network service is a task that provides some network wide service
   such as DNS, remote storage, remote logging, etc. A network service



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   may be accessed by tenant systems as well as other tasks.

   A tenant system, or TS, is a unit of execution which runs on behalf
   of a tenant in network virtualization. A TS may be implemented as a
   virtual machine or possibly using containers mechanisms. In either
   case, a virtual overlay network is implemented on behalf of a tenant,
   and isolation between tenants' virtual networks is paramount.

5.3 Reference network for scenarios

   Several communication scenarios can be considered:

      1) Task to task (service)
      2) Task to Internet
      3) Internet to task
      4) TS to service
      5) Task to TS
      6) TS to Internet
      7) Internet to TS
      8) IPv4 TS to service
      9) TS to TS in same virtual network using IPv6
      10) TS to TS in same virtual network using IPv4
      11) TS to TS in different virtual network using IPv6
      12) TS to TS in different virtual network using IPv4
      13) IPv4 TS to IPv6 TS in different virtual networks

   The figure below provides an example network topology with ILA
   addressing in use. In this example, there are four hosts in the
   network with locators L1, L2, L3, and L4. There three tasks with
   identifiers T1, T2, and T3, as well as a networking service task with
   identifier T4. The identifiers for these tasks may be locally unique
   identifiers. There are two virtual networks VNI1 and VNI2, and four
   tenant systems addressed as: VA1 and VA2 in VNI1, VA3 and VA4 in
   VNI2. The network is connected to the Internet via a gateway.

         `                     .............
                               .           .
   +-----------------+         . Internet  .         +-----------------+
   |    Host L1      |         .           .         |    Host L2      |
   | +-------------+ |         .............         | +-------------+ |
   | | TS VNI1:VA1 | |               |               | | TS VNI1:VA2 | |
   | +-------------+ +---+     +-----+-----+     +---+ +-------------+ |
   | +-------------+ |   |     | Gateway   |     |   | +-------------+ |
   | | Task T1     | |   |     +-----+-----+     |   | | TS VNI2:VA3 | |
   | +-------------+ |   |           |           |   | +-------------+ |
   +-----------------+   |     .............     |   +-----------------+
                         +-----.   Data    .-----+
   +-----------------+         .  Center   .         +-----------------+



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   |   Host L3       |   +-----.  Network  .---+     |    Host L4      |
   | +-------------+ |   |     .............   |     | +-------------+ |
   | |  Task T2    | |   |                     |     | | VM VNI2:VA4 | |
   | +-------------+ +---+                     +-----| +-------------+ |
   | +-------------+ |                               | +-------------+ |
   | |  Task T3    | |                               | | Serv. T4    | |
   | +-------------+ |                               | +-------------+ |
   +-----------------+                               +-----------------+

5.4 Scenario 1: Task to task

   The transport endpoints for task to task communication are the SIR
   addresses for the tasks. When a packet is sent on the wire, the
   locator is set in the destination address of the packet. On reception
   the destination addresses is converted back to SIR representation for
   processing at the transport layer.

   If task T1 is communicating with task T2, the ILA translation
   sequence would be:

     SIR:T1,SIR:T2 ->                     // Transport endpoints on T1
     SIR:T1,L3:T2 ->                      // ILA used on the wire
     SIR:T1,SIR:T2                        // Received at T2

5.5 Scenario 2: Task to Internet

   Communication from a task to the Internet is accomplished through use
   of a SIR address (globally routable) in the source address of
   packets. No ILA translation is needed in this path.

   If task T1 is sending to an address Iaddr on the Internet, the packet
   addresses would be:

     SIR:T1,Iaddr

5.6 Scenario 3: Internet to task

   An Internet host transmits packet to a task using an externally
   routable SIR address. The SIR prefix routes the packet to a gateway
   for the data center. The gateway translates the destination to an ILA
   address.

   If a host on the Internet with address Iaddr sends a packet to task
   T3, the ILA translation sequence would be:

     Iaddr,SIR:T3 ->                      // Transport endpoint at Iaddr
     Iaddr,L1:T3 ->                       // On the wire in data center
     Iaddr,SIR:T3                         // Received at T3



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5.7 Scenario 4: TS to service task

   A tenant can communicate with a data center service using the SIR
   address of the service.

   If TS VA1 is communicating with service task T4, the ILA translation
   sequence would be:

     VNET:VA1,SIR:T4->                    // Transport endpoints in TS
     VNET:VA1,L3:T4->                     // On the wire
     VNET:VA1,SIR:T4                      // Received at T4

   Where VNET is the address prefix for the tenant.

   Note that from the point of view of the service task there is no
   material difference between a peer that is a tenant system versus one
   which is another task.

5.8 Scenario 5: Task to TS

   A task can communicate with a TS through it's externally visible
   address.

   If task T2 is communicating with TS VA4, the ILA translation sequence
   would be:

     SIR:T2,VNET:VA4 ->                // Transport endpoints at T2
     SIR:T2,L4:(VNI2:VAX4) ->          // On the wire
     SIR:T2,VNET:VA4                   // Received at TS

5.9 Scenario 6: TS to Internet

   Communication from a TS to the Internet assumes that the VNET for the
   TS is globally routable, hence no ILA translation would be needed.

   If TS VA4 sends a packet to the Internet, the addresses would be:

     VNET:VA4,Iaddr

5.10 Scenario 7: Internet to TS

   An Internet host transmits a packet to a tenant system using an
   externally routable tenant prefix and address. The prefix routes the
   packet to a gateway for the data center. The gateway translates the
   destination to an ILA address.

   If a host on the Internet with address Iaddr is sending to TS VA4,
   the ILA translation sequence would be:



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     Iaddr,VNET:VA4 ->                   // Endpoint at Iaddr
     Iaddr,L4:(VNI2:VAX4) ->             // On the wire in data center
     Iaddr,VNET:VA4                      // Received at TS

5.11 Scenario 8: IPv4 TS to service

   A TS that is IPv4-only may communicate with a data center network
   service using protocol translation. The network service would be
   represented as an IPv4 address in the tenant's address space, and
   stateless NAT64 should be usable as described in [RFC6145].

   If TS VA2 communicates with service task T4, the ILA translation
   sequence would be:

     VA2,ADDR4 ->                        // IPv4 endpoints at TS
     SIR:(VNI1:VA2),L4:T4 ->             // On the wire in data center
     SIR:(VNI1:VA2),SIR:T4               // Received at task

   VA2 is the IPv4 address in the tenant's virtual network, ADDR4 is an
   address in the tenant's address space that maps to the network
   service.

   The reverse path, task sending to a TS with an IPv4 address, requires
   a similar protocol translation.

   For service task T4 to communicate with TS VA2, the ILA translation
   sequence would be:

     SIR:T4,SIR:(VNI1:VA2) ->           // Endpoints at T4
     SIR:T4,L2:(VNI1:VA2)   ->          // On the wire in data center
     ADDR4,VA2                          // IPv4 endpoint at TS




















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5.12 TS to TS in the same virtual network

   ILA may be used to allow tenants within a virtual network to
   communicate without the need for explicit encapsulation headers.

5.12.1 Scenario 9: TS to TS in same VN using IPV6

   If TS VA1 sends a packet to TS VA2, the ILA translation sequence
   would be:

     VNET:VA1,VNET:VA2 ->                // Endpoints at VA1
     VNET:VA1,L2:(VNI1,VAX2) ->          // On the wire
     VNET:VA1,VNET:VA2 ->                // Received at VA2

5.12.2 Scenario 10: TS to TS in same VN using IPv4

   For two tenant systems to communicate using IPv4 and ILA, IPv4/IPv6
   protocol translation is done both on the transmit and receive.

   If TS VA1 sends an IPv4 packet to TS VA2, the ILA translation
   sequence would be:

     VA1,VA2 ->                          // Endpoints at VA1
     SIR:(VNI1:VA1),L2:(VNI1,VA2) ->     // On the wire
     VA1,VA2                             // Received at VA2

5.13 TS to TS in a different virtual networks

   A tenant system may be allowed to communicate with another tenant
   system in a different virtual network. This should only be allowed
   with explicit policy configuration.

5.13.1 Scenario 11: TS to TS in a different VNs using IPV6

   For TS VA4 to communicate with TS VA1 using IPv6 the translation
   sequence would be:

     VNET2:VA4,VNET1:VA1->                // Endpoint at VA4
     VNET2:VA4,L1:(VNI1,VAX1)->           // On the wire
     VNET2:VA4,VNET1:VA1                  // Received at VA1

   Note that this assumes that VNET1 and VNET2 are globally routable
   between the two virtual networks.

5.13.2 Scenario 12: TS to TS in a different VNs using IPv4

   To allow IPv4 tenant systems in different virtual networks to
   communicate with each other, an address representing the peer would



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   be mapped into the tenant's address space. IPv4/IPv6 protocol
   translation is done on transmit and receive.

   For TS VA4 to communicate with TS VA1 using IPv4 the translation
   sequence may be:

     VA4,SADDR1 ->                        // IPv4 endpoint at VA4
     SIR:(VNI2:VA4),L1:(VNI1,VA1)->       // On the wire
     SADDR4,VA1                           // Received at VA1

      SADDR1 is the mapped address for VA1 in VA4's address space, and
      SADDR4 is the mapped address for VA4 in VA1's address space.

5.13.3 Scenario 13: IPv4 TS to IPv6 TS in different VNs

   Communication may also be mixed so that an IPv4 tenant system can
   communicate with an IPv6 tenant system in another virtual network.
   IPv4/IPv6 protocol translation is done on transmit.

   For VM VA4 using IPv4 to communicate with VM VA1 using IPv6 the
   translation sequence may be:

     VA4,SADDR1 ->                        // IPv4 endpoint at VA4
     SIR:(VNI2:VA4),L1:(VNI1,VAX1)->      // On the wire
     SIR:(VNI2:VA4),VNET1:VA1             // Received at VA1

   SADDR1 is the mapped IPv4 address for VA1 in VA4's address space.

6  Security Considerations

   Security must be considered when using identifier-locator addressing.
   In particular, the risk of address spoofing or address corruption
   must be addressed. To classify this risk the set possible
   destinations for a packet are classified as trusted or untrusted. The
   set of possible destinations includes those that a packet may
   inadvertently be sent due to address or header corruption.

   If the set of possible destinations are trusted then packet
   misdelivery is considered relatively innocuous. This might be the
   case in a data center if all nodes were tightly controlled under
   single management. Identifier-locator addressing can be used in this
   case without further additional security.

   If the set of possible destinations contains untrusted hosts, then
   packet misdelivery could be a risk. This may be the case that virtual
   machines with untrusted third party applications or OSes are running
   in the network. A malicious user may be snooping for misdelivered
   packets, or may attempt to spoof addresses. Identifier-locator



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   addressing should be used with stronger security and isolation
   mechanisms such as IPsec or GUESEC.

7  IANA Considerations

   There are no IANA considerations in this specification.

8  References

8.1  Normative References

   [RFC2460]   Deering, S. and R. Hinden, "Internet Protocol, Version 6
               (IPv6) Specification", RFC 2460, December 1998.

   [RFC2460bis] Deering, S. and R. Hinden, "Internet Protocol, Version 6
               (IPv6) Specification", draft-ietf-6man-rfc2460bis-03,
               January 2016.

   [RFC4291]   Hinden, R. and S. Deering, "IP Version 6 Addressing
               Architecture", RFC 4291, February 2006.

   [RFC6296]   Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
               Translation", RFC 6296, June 2011.

   [RFC1071]   Braden, R., Borman, D., Partridge, C., and W. Plummer,
               "Computing the Internet checksum", RFC 1071, September
               1988.

   [RFC1624]   Rijsinghani, A., "Computation of the Internet Checksum
               via Incremental Update", RFC 1624, May 1994.

   [RFC6724]   Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
               "Default Address Selection for Internet Protocol Version
               6 (IPv6)", RFC 6724, September 2012.

8.2  Informative References

   [RFC6740]   RJ Atkinson and SN Bhatti, "Identifier-Locator Network
               Protocol (ILNP) Architectural Description", RFC 6740,
               November 2012.

   [RFC6741]   RJ Atkinson and SN Bhatti, "Identifier-Locator Network
               Protocol (ILNP) Engineering Considerations", RFC 6741,
               November 2012.

   [RFC1918]   Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
               and E. Lear, "Address Allocation for Private Internets",
               BCP 5, RFC 1918, February 1996.



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   [RFC3363]   Bush, R., Durand, A., Fink, B., Gudmundsson, O., and T.
               Hain, "Representing Internet Protocol version 6 (IPv6)
               Addresses in the Domain Name System (DNS)", RFC 3363,
               August 2002.

   [RFC3587]   Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
               Unicast Address Format", RFC 3587, August 2003.

   [RFC4193]   Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
               Addresses", RFC 4193, October 2005.

   [RFC6144]   Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
               IPv4/IPv6 Translation", RFC 6144, April 2011.

   [NVO3ARCH]  Black, D., Hudson, J., Kreeger, L., Lasserre, M., and
               Narten, T., "An Architecture for Overlay Networks
               (NVO3)", draft-ietf-nvo3-arch-03

   [GUE]       Herbert, T., and Yong, L., "Generic UDP Encapsulation",
               draft-herbert-gue-02, work in progress.

   [GUESEC]   Yong, L., and Herbert, T. "Generic UDP Encapsulation (GUE)
               for Secure Transport", draft-hy-gue-4-secure-transport-
               00, work in progress

9 Acknowledgments

   The author would like to thank Mark Smith, Lucy Yong, Erik Kline,
   Saleem Bhatti, Petr Lapukhov, Blake Matheny,Doug Porter, and Fred
   Baker for their insightful comments for this draft; Roy Bryant,
   Lorenzo Colitti, Mahesh Bandewar, and Erik Kline for their work on
   defining and applying ILA.

Appendix A: Task identifier generation

   Potentially every task in a data center could be migratable as long
   as each task is assigned a unique identifier. Since an ILA identifier
   is sixty bits it is conceivable that identifiers could be allocated
   using a shared counter or based on a timestamp.

A.1 Globally unique identifiers method

   For small to moderate sized deployments the technique for creating
   locally assigned global identifiers described in [RFC4193] could be
   used. In this technique a SHA-1 digest of the time of day in NTP
   format and an EUI-64 identifier of the local host is performed. N
   bits of the result are used as the globally unique identifier.




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   The probability that two or more of these IDs will collide can be
   approximated using the formula:

       P = 1 - exp(-N**2 / 2**(L+1))

   where P is the probability of collision, N is the number of
   identifiers, and L is the length of an identifier.

   The following table shows the probability of a collision for a range
   of identifiers using a 60-bit length.









































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         Identifiers      Probability of Collision
                1000      4.3368*10^-13
               10000      4.3368*10^-11
              100000      4.3368*10^-09
             1000000      4.3368*10^-07

   Note that locally unique identifiers may be ephemeral, for instance a
   task may only exist for a few seconds. This should be considered when
   determining the probability of identifier collision.

A.2 Universally Unique Identifiers method

   For larger deployments, hierarchical allocation may be desired. The
   techniques in Universally Unique Identifier (UUID) URN ([RFC4122])
   can be adapted for allocating unique task identifiers in sixty bits.
   An identifier is split into two components: a registrar prefix and
   sub-identifier. The registrar prefix defines an identifier block
   which is managed by an agent, the sub-identifier is a unique value
   within the registrar block.

   For instance, each host in a network could be an agent so that a task
   identifier could be created on the host that initially runs a task.
   The identifier might be composed of a twenty-four bit host identifier
   followed by a thirty-six bit timestamp. Assuming that a host can
   start up to 100 tasks per second, this allows about 21.8 years before
   wrap around.

      /* Task identifier with host registrar and timestamp  */
      |3 bits|1|    24 bits      |               36  bits              |
      +------+-------------------+-------------------------------------+
      | 0x1  |C| Host identifier |        Timestamp Identifier         |
      +----------------------------------------------------------------+

Appendix B: Task migration considerations

B.1 Address migration

   ILA facilitates address (specifically identifier) migration between
   hosts as part of task migration or for other purposes. The steps in
   migrating an address might be:

      1) Configure address on the target host.

      2) Suspend use of the address on the old host. This includes
         handling established connections (see next section). A state
         may be established to drop packets or send an ILA redirect when
         packets to the migrated address are received.




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      3) Update the identifier to locator mapping database. Depending on
         the control plane implementation this may include pushing the
         new mapping to hosts.

      4) Communicating hosts will learn of the new mapping via a control
         plane either by participation in a protocol for mapping
         propagation or by the ILA redirect mechanism.

B.2 Connection migration

   When a task and its addresses are migrated between machines, the
   disposition of existing TCP connections needs to be considered.

   The simplest course of action is to drop TCP connections across a
   migration. Since migrations should be relatively rare events, it is
   conceivable that TCP connections could be automatically closed in the
   network stack during a migration event. If the applications running
   are known to handle this gracefully (i.e. reopen dropped connections)
   then this may be viable.

   For seamless migration, open connections may be migrated between
   hosts. Migration of these entails pausing the connection, packaging
   connection state and sending to target, instantiating connection
   state in the peer stack, and restarting the connection. From the time
   the connection is paused to the time it is running again in the new
   stack, packets received for the connection should be silently
   dropped. For some period of time, the old stack will need to keep a
   record of the migrated connection. If it receives a packet, it should
   either silently drop the packet or forward it to the new location.

   Author's Address

      Tom Herbert
      Facebook
      1 Hacker Way
      Menlo Park, CA
      EMail: tom@herbertland.com














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