INTERNET-DRAFT Tom Herbert
Intended Status: Standard Quantonium
Expires: September 5, 2018 Petr Lapukhov
Facebook
March 5, 2018
Identifier-locator addressing for IPv6
draft-herbert-intarea-ila-01
Abstract
This specification describes identifier-locator addressing (ILA) for
IPv6. 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 as well as solutions for use cases in
mobility.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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Copyright and License Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Use cases . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Architecture overview . . . . . . . . . . . . . . . . . . . . . 7
2.1 Addressing . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Network topology . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Transformations and mappings . . . . . . . . . . . . . . . . 8
2.4 ILA routing . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 ILA domains . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6 ILA control plane . . . . . . . . . . . . . . . . . . . . . 10
3 Address formats . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 ILA address format . . . . . . . . . . . . . . . . . . . . . 10
3.2 Locators . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . 11
3.4 Standard identifier representation addresses . . . . . . . . 12
4 Optional identifier formats . . . . . . . . . . . . . . . . . . 13
4.1 Checksum neutral mapping . . . . . . . . . . . . . . . . . . 13
4.2 Identifier types . . . . . . . . . . . . . . . . . . . . . 13
4.2.1 Interface identifiers . . . . . . . . . . . . . . . . . 15
4.2.2 Locally unique identifiers . . . . . . . . . . . . . . . 15
4.2.3 Virtual networking identifiers for IPv4 . . . . . . . . 15
4.2.4 Virtual networking identifiers for IPv6 unicast . . . . 16
4.2.5 Virtual networking identifiers for IPv6 multicast . . . 17
4.2.6 Non-local address identifiers . . . . . . . . . . . . . 18
4.3 SIR addresses with formatted identifiers . . . . . . . . . . 19
4.3.1 SIR for locally unique identifiers . . . . . . . . . . . 20
4.3.2 SIR for virtual addresses . . . . . . . . . . . . . . . 20
4.3.2 SIR for non-local address identifiers . . . . . . . . . 20
5 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.1 Identifier to locator mapping . . . . . . . . . . . . . . . 20
5.2 Address transformations . . . . . . . . . . . . . . . . . . 21
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5.2.1 SIR to ILA address transformation . . . . . . . . . . . 21
5.2.2 ILA to SIR address transformation . . . . . . . . . . . 21
5.3 Virtual networking operation . . . . . . . . . . . . . . . . 22
5.3.1 Crossing virtual networks . . . . . . . . . . . . . . . 22
5.3.2 IPv4/IPv6 protocol translation . . . . . . . . . . . . . 22
5.4 Transport layer checksums . . . . . . . . . . . . . . . . . 23
5.4.1 Checksum-neutral mapping . . . . . . . . . . . . . . . . 23
5.4.2 Sending an unmodified checksum . . . . . . . . . . . . . 25
5.5 Non-local address mapping . . . . . . . . . . . . . . . . . 25
5.6 Address assignment . . . . . . . . . . . . . . . . . . . . . 26
5.6.1 Singleton address assignment . . . . . . . . . . . . . . 26
5.6.2 Network prefix assignment . . . . . . . . . . . . . . . 26
5.6.3 Strong privacy addresses . . . . . . . . . . . . . . . . 27
5.7 Address selection . . . . . . . . . . . . . . . . . . . . . 27
5.8 Duplicate identifier detection . . . . . . . . . . . . . . . 27
5.9 ICMP error handling . . . . . . . . . . . . . . . . . . . . 28
5.9.1 Handling ICMP errors by ILA capable hosts . . . . . . . 28
5.9.2 Handling ICMP errors by non-ILA capable hosts . . . . . 28
5.10 Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 29
6 Motivation for ILA . . . . . . . . . . . . . . . . . . . . . . 29
6.1 Use cases . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.1 Multi-tenant virtualization . . . . . . . . . . . . . . 29
6.1.2 Datacenter virtualization . . . . . . . . . . . . . . . 30
6.1.3 Mobile networks . . . . . . . . . . . . . . . . . . . . 30
6.2 Alternative methods . . . . . . . . . . . . . . . . . . . . 31
6.2.1 ILNP . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.2.2 Flow label as virtual network identifier . . . . . . . . 31
6.2.3 Extension headers . . . . . . . . . . . . . . . . . . . 32
6.2.4 Encapsulation techniques . . . . . . . . . . . . . . . . 32
7 Security Considerations . . . . . . . . . . . . . . . . . . . . 32
8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 33
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.1 Normative References . . . . . . . . . . . . . . . . . . . 34
9.2 Informative References . . . . . . . . . . . . . . . . . . 34
10 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix A: Communication scenarios . . . . . . . . . . . . . . . 36
A.1 Terminology for scenario descriptions . . . . . . . . . . . 36
A.2 Identifier objects . . . . . . . . . . . . . . . . . . . . . 37
A.3 Reference network for scenarios . . . . . . . . . . . . . . 37
A.4 Scenario 1: Object to task . . . . . . . . . . . . . . . . . 38
A.5 Scenario 2: Object to Internet . . . . . . . . . . . . . . . 38
A.6 Scenario 3: Internet to object . . . . . . . . . . . . . . . 38
A.7 Scenario 4: Tenant system to service . . . . . . . . . . . . 39
A.8 Scenario 5: Object to tenant system . . . . . . . . . . . . 39
A.9 Scenario 6: Tenant system to Internet . . . . . . . . . . . 40
A.10 Scenario 7: Internet to tenant system . . . . . . . . . . . 40
A.11 Scenario 8: IPv4 tenant system to object . . . . . . . . . 40
A.12 Tenant to tenant system in the same virtual network . . . . 41
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A.12.1 Scenario 9: TS to TS in the same VN using IPV6 . . . . 41
A.12.2 Scenario 10: TS to TS in same VN using IPv4 . . . . . . 41
A.13 Tenant system to tenant system in different virtual
networks . . . . . . . . . . . . . . . . . . . . . . . . . 41
A.13.1 Scenario 11: TS to TS in different VNs using IPV6 . . . 41
A.13.2 Scenario 12: TS to TS in different VNs using IPv4 . . . 42
A.13.3 Scenario 13: IPv4 TS to IPv6 TS in different VNs . . . 42
A.14 Scenario 14: Non-local address to tenant system . . . . . . 42
Appendix B: unique identifier generation . . . . . . . . . . . . . 43
B.1 Globally unique identifiers method . . . . . . . . . . . . . 43
B.2 Universally Unique Identifiers method . . . . . . . . . . . 44
Appendix C: Datacenter task virtualization . . . . . . . . . . . . 44
C.1 Address per task . . . . . . . . . . . . . . . . . . . . . . 44
C.2 Job scheduling . . . . . . . . . . . . . . . . . . . . . . . 45
C.3 Task migration . . . . . . . . . . . . . . . . . . . . . . . 45
C.3.1 Address migration . . . . . . . . . . . . . . . . . . . 46
C.3.2 Connection migration . . . . . . . . . . . . . . . . . . 46
Appendix D: Mobility in wireless networks . . . . . . . . . . . . 47
1 Introduction
This specification describes the address formats, protocol operation,
and communication scenarios of identifier-locator addressing (ILA).
In identifier-locator addressing, an IPv6 address is split into a
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 peer
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 translate and forward the packet to the application.
Some of the concepts for ILA are adapted from Identifier-Locator
Network Protocol (ILNP) ([RFC6740], [RFC6741]) which defines a
protocol and operations model for identifier-locator addressing in
IPv6.
Section 6 provides a motivation for ILA and comparison of ILA with
alternative methods that achieve similar functionality.
1.1 Terminology
ILA Identifier-locator addressing.
ILA host An end host that is capable of performing ILA
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translations on transmit or receive.
ILA router A network node that performs ILA translation and
forwarding of translated packets.
ILA node A network node capable of performing ILA translations.
This can be an ILA router or ILA host.
Locator A network prefix that routes to a physical host.
Locators provide the topological location of an
addressed node. ILA locators are typically sixty-four
bit prefixes, however other prefix sizes can be used.
Locator address
An IPv6 address than contains a locator.
Identifier A number that identifies an addressable node in the
network independent of its location. ILA identifiers
are typically sixty-four bit values, however other
sized values may be used.
Identifier address
An IPv6 address that contains an identifier but not a
locator. Identifier addresses are visible to
applications and provide a means to address nodes
independent of their location.
ILA address
An IPv6 address composed of a locator and an
identifier. In the canonical format the locator
occupies the upper sixty-four bits of an address and
the identifier is in the lower sixty-four bits.
ILA domain A unique identifier namespace. This may be indicated by
a SIR prefix where each SIR prefix maps to an ILA
domain.
ILA transformation
The process of transforming an identifier address to a
locator address or vice versa.
SIR Standard identifier representation.
SIR prefix A network prefix used to identify a SIR address. In the
canonical format SIR prefixes are sixty-four bits.
SIR address
An identifier address composed of a SIR prefix
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(typically upper sixty-four bits) and an identifier
(typically lower sixty-four bits).
Virtual address
An IPv6 or IPv4 address that resides in the address
space of a virtual network. Such addresses may be
translated to identifier addresses as an external
representation of the address outside of the virtual
network, or they may be translated to locator addresses
for transit over an underlay network.
Topological address
An address that refers to a non-virtual node in a
network topology. These address physical hosts in a
network.
Checksum-neutral mapping
A method to preserve a correct transport layer checksum
when performing ILA transformation. When the upper bits
of an address are overwritten in an ILA transformation,
a modification can be made to the low order bits of the
identifier to offset the checksum difference.
1.2 Use cases
ILA use cases include datacenter virtualization, network
virtualization, and mobility in cellular and other mobile networks.
Section 6 provides details on these use cases. ILA operates at the
network layer so it works with any transport layer protocol and can
be used at intermediate devices or end nodes. An ILA implementation
may include optimizations depending on where in the network it runs.
1.3 Scope
Architecturally, ILA is a protocol to implement transparent network
overlays without encapsulation. It is also an identifier/locator
split protocol where location of a node is decoupled from its
identity. ILA works by transforming addresses between identifier and
locator addresses. ILA does address "transformation" as opposed to
"translation" since address modifications are always undone before
delivery to a destination node.
With identifier-locator addressing, network virtualization and
addressing for mobility 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 method is transparent to the network, so protocol
specific mechanisms in network hardware work seamlessly. These
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mechanisms include hash calculation for ECMP, NIC large segment
offload, checksum offload, etc.
ILA includes both a data plane and control plane. The data plane
defines the address structure and mechanisms for transforming
application visible identifier addresses to locator addresses. The
control plane's primary focus is a mapping system that includes a
database of identifier to locator mappings. This mapping database
drives ILA transformations. Control plane protocols disseminate
identifier to locator mappings amongst ILA nodes.
This specification is mostly concerned with the data plane for ILA.
The control plane is specified elsewhere.
2 Architecture overview
This section describes the architectural aspects of ILA.
2.1 Addressing
ILA performs transformations on IPv6 addresses. There are two types
of addresses introduced for ILA: locator addresses and identifier
addresses.
Locator addresses are IPv6 addresses that are composed of a locator
(typically upper sixty-four bits) and an identifier (typically low
order sixty-four bits). The identifier serves as the logical address
of a node, and the locator indicates the location of a node on the
network.
Identifier addresses are IPv6 addresses that contain an identifier
but not a locator. Identifier addresses are visible to applications
and provide a means to address nodes independent of their location.
A SIR address (Standard Identifier Representation) is an identifier
address that contains an identifier and an application visible SIR
prefix. SIR addresses are visible to the application and can be used
as connection endpoints. When a packet is sent to a SIR address, an
ILA router or host overwrites the SIR prefix with a locator
corresponding to the identifier. When a peer receives the packet, the
locator is overwritten with the original SIR prefix before delivery
to the application. In this manner applications only see SIR
addresses, they do not have visibility into ILA addresses.
ILA transformations can transform addresses from one type to another.
In network virtualization, virtual addresses can be transformed into
locator or identifier addresses, and conversely locator and
identifier addresses can be translated to virtual addresses.
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2.2 Network topology
ILA nodes are nodes in the network that perform ILA transformations.
An ILA router is a node that performs ILA address transformation and
packet forwarding to implement overlay network functionality. ILA
routers perform transformations on packets sent by end nodes for
transport across an underlay network. Packets received by ILA routers
on the underlay network have their addresses reversed transformed for
reception at an end node. An ILA host is an end node that implements
ILA functionality for transmitting or receiving packets.
ILA nodes are responsible for transit of packets over an underlay
network. On ingress, an ILA node (host or router) will transform the
virtual or identifier address of a destination to a locator address.
At a peer ILA node, the reverse transformation is performed before
handing packets to an application.
The figure below provides an example topology using ILA with SIR
addresses. ILA transformations performed in one direction between
Host A and Host B are denoted. Host A sends a packet with a
destination SIR address (step (1)). An ILA router in the path
transforms the SIR address to an ILA address with a locator. The
locator is set to a value that will route packets to a peer ILA node
that Host B is downstream of. The packet is forwarded over the
network and delivered to the peer ILA node (step 2). The peer ILA
node, in this case another ILA router, transforms the destination
address back to a SIR address and forwards to the final destination
(step 3).
+--------+ +--------+
| Host A +-+ +--->| Host B |
| | | (2) ILA (') | |
+--------+ | ...addressed.... ( ) +--------+
V +---+--+ . packet . +---+--+ (_)
(1) SIR | | ILA |----->-------->---->| ILA | | (3) SIR
addressed +->|router| . . |router|->-+ addressed
packet +---+--+ . IPv6 . +---+--+ packet
/ . Network .
/ . . +--+-++--------+
+--------+ / . . |ILA || Host |
| Host +--+ . .- -|host|| |
| | . . +--+-++--------+
+--------+ ................
2.3 Transformations and mappings
Address transformation is the mechanism employed by ILA. Logical or
virtual addresses are transformed to topological IPv6 addresses for
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transport to the proper destination. In the canonical ILA addressing
format, transformation occurs in the upper sixty-four bits of an
address, the low order sixty-four bits contains an identifier that is
immutable and is not used to route a packet. The identifier/locator
split in addresses may have alternate arrangements for different use
cases. For instance, transformations on non-local identifier address
(Section 4.2.6) are performed across the full 128 bit address.
Each ILA node maintains a mapping table. This table maps identifiers
to locators. The mappings are dynamic as nodes with identifiers can
be created, destroyed, or move in the network. Mappings are
propagated amongst ILA routers or hosts in a network using mapping
propagation protocols (mapping propagation protocols will be
described in other specifications).
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 device mobility. 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 location, its identifier to locator mapping is updated.
2.4 ILA routing
ILA is intended to be sufficiently lightweight so that all the hosts
in a network 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
routing topology is illustrated below.
+---------+--+
(1) Default SIR route |ILA router | (2) Transformed dest.
+->->->->->->->->->| |->->->->->+
| +------------+ |
| V
+--------++-----+ +-----++--------+
| || | | || |
| Host || ILA | | ILA || Host |
| ||host |->->->->->->->->->->->->->->| host|| |
+--------++-----+ (5) Direct route +-----++--------+
. .
. . (3) Resolve
(4) Resolve . . Request +--------------+
Reply . ..................>| |
. | ILA resolver |
........................| |
+--------------+
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An ILA router can be addressed by an "anycast" SIR prefix so that it
receives packets sent on the network with SIR addresses. When an ILA
router receives a SIR addressed packet (step (1) in the diagram) it
will perform the ILA transformation and send the ILA addressed packet
to the destination ILA node (step (2)).
If a sending host is ILA capable the triangular routing can be
eliminated by performing an ILA resolution protocol. This entails a
host sending an ILA resolve request that specifies the SIR address to
resolve (step (3) in the figure). An ILA resolver can respond to a
resolve request with the identifier to locator mapping (step (4)).
Subsequently, the ILA host can perform ILA transformation and send
directly to the destination specified in the locator (step (5) in the
figure). The ILA resolution protocol will be specified in a companion
document.
In this model an ILA host maintains a cache of identifier mappings
for identifiers that it is currently communicating with. ILA routers
are expected to maintain a complete list of identifier to locator
mappings within the ILA domains that they service.
2.5 ILA domains
An ILA domain defines a namespace for identifiers. Identifiers must
be unique within an ILA domain. Each SIR prefix maps to one ILA
domain so that the combination of a SIR prefix and an identifier (a
SIR address) uniquely identifies a node. More than one SIR prefix may
be associated a domain where each SIR prefix combined with the same
identifier refers to the same node.
Locators MUST map to only one ILA domain in order to ensure that
transformation from a locator to SIR prefix is unambiguous.
2.6 ILA control plane
ILA routers and ILA hosts require a control plane that propagates the
tables that map identifier addresses to locator address (or just
identifier to locator mappings). There are several possible methods
for control planes that have been proposed including synchronized
configuration, BGP, DNS, and NoSQL databases. Defining a specific
control plane for ILA is out of scope of this document.
3 Address formats
3.1 ILA address format
In the canonical format, an ILA address is composed of a locator and
an identifier where each occupies sixty-four bits (similar to the
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encoding in ILNP [RFC6741]).
| 64 bits | 64 bits |
+--------------------------------+-------------------------------+
| Locator | Identifier |
+----------------------------------------------------------------+
Note that there is no technical reason why identifiers and locators
must be sixty-four bits. Different sizes could be used. The split is
somewhat arbitrary, however it does simplify the description and
implementation. For instance, sixty-four bits is the size of a "long
long" native data type in several computer architectures. It is
conceivable that a different arrangement could be used for some ILA
domain. However, for the purposes of this document we assume that the
64/64 split is the canonical format.
3.2 Locators
Locators are routable network address prefixes that create
topological addresses for physical hosts within the network. They
SHOULD be assigned from a global address block [RFC3587].
The format of an ILA address with a global unicast locator is:
|<---------- Locator ----------->|
|3 bits| N bits | M bits | 64 bits |
+------+-------------+---------+---------------------------------+
| 001 | Global prefix | Subnet | Identifier |
+------+---------------+---------+-------------------------------+
3.3 Identifiers
Identifiers uniquely identify logical nodes in an ILA domain. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Identifiers are specified to be sixty-four bit values that are
unstructured. A structure and format for identifiers MAY be defined
for a domain; for instance the operator of an ILA domain may define
the use of prefixes for its identifiers in order to facilitate
hierarchies of its identifiers. Section 4 defines optional ILA
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formats that an ILA domain might impose locally that allow different
types of identifiers as well as an indication of checksum neutral
mapping.
3.4 Standard identifier representation addresses
An identifier identifies objects or nodes in a network. 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 an identifier address to indicate the peer endpoint of the
communication. The endpoints of an established connection context are
also referenced by identifiers (encoded in identifier addresses). 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.
The format of a SIR address is:
| 64 bits | 64 bits |
+--------------------------------+-------------------------------+
| SIR prefix | Identifier |
+----------------------------------------------------------------+
A SIR prefix SHOULD be a globally routable prefix per [RFC3587]. A
globally routable SIR prefix facilitates connectivity between hosts
on the Internet and ILA nodes. An ILA router 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 transformation from a SIR address to an ILA address is
performed when sending a packet, the reverse transformation at the
receiver yields the same SIR address that was seen at the
transmitter. This also ensures that a reverse checksum-neutral
mapping can be performed at a receiver to restore the addresses that
were included in a pseudo header for setting a transport checksum.
An identifier 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 identifier address without knowledge that it encodes an
identifier.
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4 Optional identifier formats
This section describes optional identifier formats that allow for
different types of identifiers, groups of identifiers, and checksum
neutral mapping being applied. Note that identifiers are defined as
unstructured fields, there is no required structure imposed on them.
An administrator MAY impose an identifier format within an ILA
domain. Any imposed structure is local only to the domain and all ILA
nodes within the domain must agree on the format. A format might
include optional elements as described below, or may include other
elements customized for a domain.
4.1 Checksum neutral mapping
Checksum neutral mapping is an optional mechanism that may be applied
to an ILA address (see section 5.4.1 for description of checksum-
neutral mapping). When employed the checksum neutral mapping occupies
the low order sixteen bits of the identifier in a locator address.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum-neutral adjustment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The presence of the checksum-neutral adjustment field must be
unambiguous. An optional C-bit flag could be used in the identifier
to indicate the checksum-neutral field is valid. The use of the C-bit
is demonstrated below. Alternatively, within an ILA domain an
operator could require it to be assumed that all ILA addresses have
the checksum-neutral field set so that an explicit flag is not
needed. Note that checksum-neutral adjustment is not used with
identifier addresses.
4.2 Identifier types
This section describes an optional identifier format that allows for
different types of identifiers and an indication of checksum neutral
mapping being applied.
Note that the identifier type format is optional. If this is not used
within an ILA domain then all ILA nodes assume that all identifiers
are of the same type (locally unique identifier for instance).
The optional type format of an ILA identifier with the checksum
adjust flag 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|C| Identifier |
+-+-+-+-+ |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields are:
o Type: Type of the identifier (see below).
o C: The C-bit. This indicates that checksum-neutral mapping
applied (see below). Presence of this field is optional.
o Identifier: Identifier value.
Identifier types allow standard encodings for common uses of
identifiers. 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: non-local address identfier
6-7: Reserved
If the C-bit is set then the low order sixteen bits of an identifier
contain the adjustment for checksum-neutral mapping (see section
4.4.1 for description of checksum-neutral mapping). The format of an
identifier with checksum neutral mapping 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|1| Identifier |
+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Checksum-neutral adjustment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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4.2.1 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 purpose of this
type is to allow normal IPv6 addresses to be defined within the same
networking prefix as ILA addresses. Type bits and C-bit MUST be zero.
The format of an ILA interface identifier address is:
| 64 bits |3 bits|1| 60 bits |
+----------------------------+------+---------------------------+
| Prefix | 0x0 |0| IID |
+---------------------------------------------------------------+
4.2.2 Locally unique identifiers
Locally unique identifiers (LUI) can be created for various
addressable objects within a network. These identifiers are in a flat
space and must be unique within a SIR domain (unique within a site
for instance). To simplify administration, hierarchical allocation of
locally unique identifiers may be performed. The format of an ILA
address with locally unique identifiers is:
| 64 bits |3 bits|1| 60 bits |
+----------------------------+------+---------------------------+
| Locator | 0x1 |C| Locally unique ident. |
+---------------------------------------------------------------+
The figure below illustrates the transformation from SIR address to
an ILA address as would be performed when a node sends to a SIR
address. Note the low order 16 bits of the identifier may be modified
as the checksum-neutral adjustment. The reverse transformation of ILA
address to SIR address is symmetric.
+----------------------------+------+---------------------------+
| SIR prefix | 0x1 |0| Identifier |
+---------------------------------------------------------------+
| | |
SIR prefix to locator C-bit if needed |
V V V
+----------------------------+------+---------------------------+
| Locator | 0x1 |C| Identifier |
+---------------------------------------------------------------+
4.2.3 Virtual networking identifiers for IPv4
This type defines a format for encoding an IPv4 virtual address and
virtual network identifier within an identifier. The format of an ILA
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address for IPv4 virtual networking is:
| 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.
Translating a virtual IPv4 address into an ILA or SIR address and the
reverse transformation are straight forward. Note that the low order
16 bits of the IPv6 address may be modified as the checksum-neutral
adjustment and that this transformation implies protocol translation
between IPv4 and IPv6.
+----------------+
| IPv4 address |
+----------------+
^
|
V
+----------------------------+------+-----------+----------------+
| Locator or SIR prefix | 0x2 |C| VNID | IPv4 address |
+----------------------------------------------------------------+
4.2.4 Virtual networking identifiers for IPv6 unicast
In this format, a 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. The format an IPv6
unicast encoding with VNID in an ILA address is:
| 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. Note that for ILA transformations the low order
sixteen of the VADDR6L may be modified for checksum-neutral
adjustment.
The figure below illustrates encoding a tenant IPv6 virtual unicast
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address into a ILA or SIR address.
+----------------------------------------------+-----------------+
| Tenant prefix | VADDR6L |
+-----------------------+-------------------------------+--------+
| |
+-prefix to VNID-+ |
| |
v v
+---------------------------+------+-----------+-----------------+
| Locator or SIR prefix | 0x3 |C| VNID | VADDR6L |
+----------------------------------------------------------------+
This encoding is reversible, given an ILA address, the virtual
address visible to the tenant can be deduced:
+---------------------------+------+-----------+-----------------+
| Locator or SIR prefix | 0x3 |C| VNID | VADDR6L |
+----------------------------------------+-----------------------+
| |
+-VNID to prefix-+ |
| |
v v
+----------------------------------------------+-----------------+
| Tenant prefix | VADDR6L |
+----------------------------------------------------------------+
4.2.5 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 an ILA address */
| 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>::<MADDRL6 high 12 bits>:<MADDRL6 low 16 bits>
And so can encode multicast addresses of the form:
ff0X::0 to ff0X::0fff:ffff
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The figure below illustrates encoding a tenant IPv6 virtual multicast
address in an ILA or SIR address. Note that low order sixteen bits
of MADDR6L may be modified to be the checksum-neutral adjustment.
| 12 bits | 4 bits| 84 bits | 28 bits |
+---------+-------+-----------------------------------+----------+
| 0xfff | Scope | 0's | MADDR6L |
+-------------+---------------------------------------------+----+
| |
+------------------------------------+ |
| |
v v
+--------------------------+------+------------------------------+
| Locator or SIR prefix | 0x4 |C| VNID |Scope | MADDR6L |
+----------------------------------------------------------------+
This transformation is reversible:
+--------------------------+------+------------------------------+
| Locator or SIR prefix | 0x4 |C| VNID |Scope | MADDR6L |
+----------------------------------------------------------------+
| |
+------------------------------------+ |
| |
V V
+---------+-------+-----------------------------------+----------+
| 0xfff | Scope | 0's | MADDR6L |
+-------------+---------------------------------------------+----+
4.2.6 Non-local address identifiers
Non-local address identifiers allow mapping an arbitrary address to
an ILA address. The mapping system contains an entry that associates
an IPv6 address with an identifier. The associated IP address does
not need to be a SIR address or even in the same routing domain.
The format of a locator address for a non-local address identifier
is:
/* Non local identifier address mapping */
| 64 bits |3 bits|1| 44 bits | 16 bits |
+--------------------------+------+------------------------------+
| Locator | 0x5 |C| Identifier | csum adj |
+----------------------------------------------------------------+
If the checksum adjust field is present it is not part of the
identifier that is used in the mapping lookup. The high order bits of
the address were originally not a SIR prefix, so it cannot be assumed
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the checksum adjustment is based on a SIR prefix. The identifier is
taken to be the forty-four bits that precede the checksum adjustment
field. When creating the ILA address, the checksum adjustment field
is initialized to zero and then set based on checksum difference
between the original non-local address and the ILA address.
The figure below illustrates encoding an address into a locator
address.
/* Non local address identifier */
+----------------------------------------------------------------+
| Address |
+----------------------------------------------------------------+
|
+--------------+
|
V
+-------------------------------+--------------------------------+
| Locator | 0x5 |C| Identifier | Csum-adj |
+-------------------------------+--------------------------------+
A reverse transformation is performed based on a lookup in the
mapping table on the identifier (44 bits as shown above). The result
of the lookup provides the original address.
+-------------------------------+--------------------------------+
| Locator | 0x5 |C| Identifier | Csum-adj |
+-------------------------------+--------------------------------+
|
+-------------+
|
V
+----------------------------------------------------------------+
| Address |
+----------------------------------------------------------------+
4.3 SIR addresses with formatted identifiers
The format of a SIR address with a formatted identifier is:
| 64 bits |3 bits|1| 60 bits |
+--------------------------------+-------------------------------+
| SIR prefix | Type |0| Identifier |
+----------------------------------------------------------------+
The C-bit (checksum-neutral mapping) MUST be zero for a SIR address.
Type may be any identifier type except zero (interface identifiers)
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4.3.1 SIR for locally unique identifiers
The SIR address for a locally unique identifier has format:
| 64 bits |3 bits|1| 60 bits |
+--------------------------------+-------------------------------+
| SIR prefix | 0x1 |0|Locally unique ident. |
+----------------------------------------------------------------+
4.3.2 SIR for virtual addresses
A virtual address can be encoded using the standard identifier
representation. For example, the SIR address for an IPv6 virtual
address may be:
| 64 bits |3 bits|1| 28 bits | 32 bits |
+--------------------------------+------+------------+-----------+
| SIR prefix | 0x3 |0| VNID | VADDRL6 |
+----------------------------------------------------------------+
Note that this allows three representations of the same address in he
network: as a virtual address, a SIR address, and an ILA address.
4.3.2 SIR for non-local address identifiers
A non-local address identifier can be encoded using the standard
identifier representation. For example, an encoding may be:
| 64 bits |3 bits|1| 44 bits | 16 bits |
+--------------------------------+------+--------------+---------+
| SIR prefix | 0x5 |0| Identifier | 0 |
+----------------------------------------------------------------+
Note that lower order sixteen bits are set to zero since that would
be the checksum adjustment value bits if transformed to an ILA
address.
5 Operation
This section describes operation methods for using identifier-locator
addressing.
5.1 Identifier to locator mapping
An application initiates a communication or flow using an identifier
address or virtual address for a destination. In order to send a
packet on the network, the destination address is transformed by an
ILA node in the path. An ILA node maintains a list of mappings from
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identifier to locator to perform this transformation.
The mechanisms of propagating and maintaining identifier to locator
mappings are outside the scope of this document.
5.2 Address transformations
With ILA, address transformation is performed to convert identifier
addresses to locator addresses, and locator addresses to identifier
addresses. Transformation is usually done on a destination address as
a form of source routing, however transformation on source virtual
addresses to identifier addresses can also be done to support some
network virtualization scenarios (see section Appendix A for
examples).
5.2.1 SIR to ILA address transformation
When translating a SIR address to an ILA address, the SIR prefix in
the address is overridden with a locator, and checksum neutral
mapping may be performed. Since this operation is potentially done
for every packet the process should be very efficient (particularly
the lookup and checksum processing operations).
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 or virtual
address for the peer. The peer address may have been discovered
through DNS or other means.
2) An ILA node translates the packet to use the locator. If the
original destination address is a SIR address then the SIR
prefix is overwritten with the locator. If the original packet
is a virtually addressed tenant packet then the virtual address
is transformed per section 4.2. The locator is discovered by a
lookup in the locator to identifier mappings.
3) The ILA node performs checksum-neutral mapping if configured
for that (section 5.4).
4) Packet is forwarded on the wire. The network routes the packet
to the node indicated by the locator.
5.2.2 ILA to SIR address transformation
When a destination node (ILA router or end host) receives an ILA
addressed packet, the ILA address MUST be transformed back to a SIR
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address (or virtual address) before upper layer processing.
The steps of receive processing are:
1) Packet is received. The destination locator is verified to
match a locator assigned to the node.
2) A lookup is performed on the destination identifier to find if
it addresses a local identifier. If match is found, either the
locator is overwritten with SIR prefix (for locally unique
identifier type) or the address is transformed back to a tenant
virtual address.
3) Perform reverse checksum-neutral mapping if C-bit is set
(section 5.4).
4) Perform any optional policy checks; for instance that the
source may send a packet to the destination address, that
packet is not illegitimately crossing virtual networks, etc.
5) Forward packet to the application.
5.3 Virtual networking operation
When using ILA with virtual networking identifiers, address
transformation 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. Transformation may
occur on either source address, destination address, or both (see
scenarios for virtual networking in Appendix A). Address
transformation is performed similar to the SIR transformation cases
described above.
5.3.1 Crossing virtual networks
With explicit configuration, virtual network hosts may communicate
directly with virtual hosts in another virtual network by using
identifier 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). See appendix A.13 for example of ILA addressing for
such a scenario.
5.3.2 IPv4/IPv6 protocol translation
An IPv4 tenant may send a packet that is converted to an IPv6 packet
with ILA addresses. Similarly, an IPv6 packet with ILA addresses may
be converted to an IPv4 packet to be received by an IPv4-only tenant.
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These are IPv4/IPv6 stateless protocol translations as described in
[RFC6144] and [RFC6145]. See appendix A.12 for a description of these
scenarios.
5.4 Transport layer checksums
Packets undergoing ILA transformation may encapsulate transport layer
checksums (e.g. TCP or UDP) that include a pseudo header that is
affected by the transformation.
ILA provides two alternatives do deal with this:
o Perform a checksum-neutral mapping to ensure that an
encapsulated transport layer checksum is kept correct on the
wire.
o Send the checksum as-is, that is send the checksum value based
on the pseudo header before transformation.
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, using checksum-
neutral mapping is recommended. 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.
5.4.1 Checksum-neutral mapping
When a change is made to one of the IP header fields in the IPv6
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 can perform a checksum-neutral mapping when a SIR prefix or
virtual address is transformed to a locator in an IPv6 address, and
performs the reverse mapping when translating a locator back to a SIR
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prefix or virtual address. The low order sixteen bits of the
identifier contain the checksum adjustment value for ILA.
On transmission, the transformation 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) If the C-bit is to be used then 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 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 if it is to be present.
Note that the "adjustment" (the 16-bit value set in the identifier)
is fixed for a given SIR to locator mapping, so the adjustment value
can be saved in an associated data structure for a mapping to avoid
computing it for each transformation.
On reception of an ILA addressed packet, if checksum-neutral mapping
is applied to the packet (either the C-bit is set or its used is
assumed for the ILA domain):
1) Compute the one's complement difference between the locator in
the address and the SIR prefix that the locator is being
transformed to. Fold this value to 16 bits (add-with-carry four
16-bit words of the difference).
2) If the C-bit is used then add-with-carry 0x1000 to the value
from #1. This compensates the checksum for clearing the C-bit.
3) Add-with-carry 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 clear the C-bit if its present. This
restores the original identifier sent in the packet.
Note that receive checksum-neutral mapping process requires that the
original upper sixty four bits in the address can be deduced. The
method for this is different based on identifier type:
o interface identifier: checksum-neutral mapping is not used.
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o locally unique identifier: the SIR prefix is inferred from the
one to one mapping with a locator.
o virtual network identifier for IPv4: the original upper sixty-
four bits are assumed to be zero.
o virtual network identifier for IPv6 unicast: the VNID in the
identifier is mapped to a tenant prefix that includes the
original upper sixty-four bits.
o virtual network identifier for IPv6 multicast: the original
upper sixty-four bits can be deduced by from the scope field in
the identifier and fixed field of the multicast address.
o non-local address identifier: the identifier, not including the
low order sixteen bits of the address, is used to lookup the
original address. Since the full address is provided by the
lookup, the process to undo a checksum-neutral mapping can be
obviated in this case
5.4.2 Sending an unmodified checksum
When sending an unmodified checksum, the checksum is incorrect as
viewed in the packet on the wire. At the receiver, ILA transformation
of the destination ILA address back to the SIR address occurs before
transport layer processing. This ensures that the checksum can be
verified when processing the transport layer header containing the
checksum. Intermediate devices are not expected to drop packets due
to a bad transport layer checksum.
5.5 Non-local address mapping
Non-local addresses may be mapped into ILA addresses using non-local
address identifiers. This allows transit of such addresses across the
underlay of an ILA domain. This would be useful for handling
addresses in a network that originate from an external source. An
example of this would be roaming in cellular network so that a device
can continue using addresses that are part of its home network.
A packet may be forwarded to an ILA router that has a non-local
destination address which is not a identifier address for the domain.
An ILA router can perform a lookup on the full address in an
alternate mapping table. If there is a match, an identifier is
returned that reverses maps to the address. This identifier is in the
ILA domain space and identifies the node with the non-local address.
A normal mapping table lookup can then be done to get the locator for
the node in the ILA domain.
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At a peer ILA router, a lookup is performed on the destination
identifier in a table that maps the non-local address identifier to
the original non-local address. If an entry is found, the address is
set in the destination address and the packet is forward to the
destination.
Note that the non-local address to identifier mapping and its reverse
mapping must be set in the table before hand.
5.6 Address assignment
ILA supports single address assignments as well as prefix
assignments. ILA will also support strong privacy in addressing
[ADDRPRIV].
5.6.1 Singleton address assignment
Singleton addresses can use a canonical 64/64 locator/identifier
split. Singleton addresses can be assigned by DHCPv6.
5.6.2 Network prefix assignment
Prefix assignment can be done via SLAAC or DHCPv6-PD.
To support /64 prefix assignment with ILA, the ILA identifier can be
encoded in the upper sixty-four bits of an address. A level of
indirection is used so that ILA transforms the upper sixty four bits
to contain both a locator and an index into a locator (ILA node)
specific table. The entry in the table provides the original sixty-
four bit prefix so that locator to identifier address transformation
can be done. As an example of this scheme, suppose network has a /24
prefix. The identifier address format for /64 assignment might be:
| 24 bits | 40 bits | 64 bits |
+-------------+---------------------+------------------------------+
| Network | Identifier | IID |
+-------------+---------------------+------------------------------+
The IID part is arbitrarily assigned by the device, so that is
ignored by ILA. All routing, lookups, and transformations (excepting
checksum neutral mapping) are based on the upper sixty-four bits. For
identifier to locator address transformation, a lookup is done on the
upper sixty-four bits. That returns a value that contains a locator
and a locator table index. The resulting packet format may be
something like:
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| 24 bits | 20 bits | 20 bits | 64 bits |
+-------------+---------+-----------+------------------------------+
| Network | Locator | Loc index | IID |
+-------------+---------+-----------+------------------------------+
The packet is forwarded and routed as addressed by locator (/44 route
in this case). At the ILA forwarding node, the locator index is used
as a key to an ILA node specific table that returns a 40 bit
Identifier. This value is then written in the packet do ILA to
identifier address transformation thereby restoring the original
destination address. The locator index is not globally unique, it is
specific to each ILA node. When an end node attaches to an ILA node,
an index is chosen so that the table is populated at the ILA node and
the ILA mapping includes the locator and index. When a node detaches
from on ILA, it's entry in the table is removed and the index can be
reused after a hold-down period to allow stale mappings to be purged.
5.6.3 Strong privacy addresses
Note that when a /64 is assigned to end hosts (such as UEs in a
mobile network), the assigned prefix may become a persistent
identifier for a device. This is a potential privacy issue. [ADDPRIV]
describes this problem and suggests some solutions that may be used
with ILA.
5.7 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 choice of locator or identifier is implementation or
configuration specific. The selection of an identifier occurs at flow
creation and must be invariant for the duration of the flow. Locator
selection must be done at least once per flow, and the locator
associated with the destination of a flow may change during the
lifetime of the flow (for instance in the case of a migrating
connection it will change). ILA address selection should follow
specifications in Default Address Selection for Internet Protocol
Version 6 (IPv6) [RFC6724].
5.8 Duplicate identifier detection
As part of implementing the locator to identifier mapping, duplicate
identifier detection should be implemented in a centralized control
plane. A registry of identifiers could be maintained (possibly in
association with 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 the identifier is unregistered. The
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control plane should able to detect a registration attempt for an
existing identifier and deny the request.
5.9 ICMP error handling
A packet that contains an ILA address may cause ICMP errors within
the network. In this case the ICMP data contains an IP header with an
ILA address. ICMP messages are sent back to the source address in the
packet. Upon receiving an ICMP error the host will process it
differently depending on whether it is ILA capable.
5.9.1 Handling ICMP errors by ILA capable hosts
If a host is ILA capable it can attempt to reverse translate the ILA
address in the destination of a header in the ICMP data back to a SIR
address that was originally used to transmit the packet. The steps
are:
1) Assume that the upper sixty-four bits of the destination
address in the ICMP data is a locator. Match these bits to a
SIR address. If the host is only in one SIR domain, then the
mapping to SIR address is implicit. If the host is in multiple
domains then a locator to SIR addresses table can be maintained
for this lookup.
2) If the identifier includes checksum-neutral mapping, undo the
checksum-neutral mapping using the SIR address found in #1 and
the process in section 5.4.1. The resulting identifier address
is potentially the original address used to send the packet.
3) Lookup the identifier in the identifier to locator mapping
table. If an entry is found compare the locator in the entry to
the locator (upper sixty-four bits) of the destination address
in the IP header of the ICMP data. If these match then proceed
to next step.
4) Overwrite the upper sixty-four bits of the destination address
in the ICMP data with the found SIR prefix and overwrite the
low order sixty-four bits with the found identifier (the result
of undoing checksum-neutral mapping). The resulting address
should be the original SIR address used in sending. The ICMP
error packet can then be received by the stack for further
processing.
5.9.2 Handling ICMP errors by non-ILA capable hosts
A non-ILA capable host may receive an ICMP error generated by the
network that contains an ILA address in IP header contained in the
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ICMP data. This would happen in the case that an ILA router performed
transformation on a packet the host sent and that packet subsequently
generated an ICMP error. In this case the host receiving the error
message will attempt to find the connection state corresponding to
the packet header in the ICMP data. Since the host is unaware of ILA
the lookup for connection state should fail. Because the host cannot
recover the original addresses it used to send the packet, it won't
be able any to derive any useful information about the original
destination of the packet that it sent.
If packets for a flow are always routed through an ILA router in both
directions, for example ILA routers are coincident with edge routers
in a network, then ICMP errors could be intercepted by an
intermediate node which could translate the destination addresses in
ICMP data back to the original SIR addresses. A receiving host would
then see the destination address in the packet of the ICMP data to be
that it used to transmit the original packet.
5.10 Multicast
ILA is generally not intended for use with multicast. In the case of
multicast, routing of packets is based on the source address. Neither
the SIR address nor an ILA address is suitable for use as a source
address in a multicast packet. A SIR address is unroutable and hence
would make a multicast packet unroutable if used as a source address.
Using an ILA address as the source address makes the multicast packet
routable, but this exposes ILA address to applications which is
especially problematic on a multicast receiver that doesn't support
ILA.
If all multicast receivers are known to support ILA, a local locator
address may be used in the source address of the multicast packet. In
this case, each receiver will translate the source address from an
ILA address to a SIR address before delivering packets to an
application.
6 Motivation for ILA
6.1 Use cases
6.1.1 Multi-tenant virtualization
In multi-tenant virtualization overlay networks are established for
tenants to provide virtual networks. Each tenant may have one or more
virtual networks and a tenant's nodes are assigned virtual addresses
within virtual networks. Identifier-locator addressing may be used as
an alternative to traditional network virtualization encapsulation
protocols used to create overlay networks (e.g. VXLAN [RFC7348]).
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Tenant systems (e.g. VMs) run on physical hosts and may migrate to
different hosts. A tenant system is identified by a virtual address
and virtual networking identifier of a corresponding virtual network.
ILA can encode the virtual address and a virtual networking
identifier in an ILA identifier. Each identifier is mapped to a
locator that indicates the current host where the tenant system
resides. Nodes that send to the tenant system set the locator per the
mapping. When a tenant system migrates, its identifier to locator
mapping is updated and communicating nodes will use the new mapping.
6.1.2 Datacenter virtualization
Datacenter virtualization virtualizes networking resources. Various
objects within a datacenter can be assigned addresses and serve as
logical endpoints of communication. A large address space, for
example that of IPv6, allows addressing to be used beyond the
traditional concepts of host based addressing. Addressed objects can
include tasks, virtual IP addresses (VIPs), pieces of content, disk
blocks, etc. Each object has a location which is given by the host on
which an object resides. Some objects may be migratable between hosts
such that their location changes over time.
Objects are identified by a unique identifier within a namespace for
the datacenter (appendix B discusses methods to create unique
identifiers for ILA). Each identifier is mapped to a locator that
indicates the current host where the object resides. Nodes that send
to an object set the locator per the mapping. When an object migrates
its identifier to locator mapping is updated and communicating nodes
will use the new mapping.
A datacenter object of particular interest is tasks, units of
execution for for applications. The goal of virtualzing tasks is to
maximize resource efficiency and job scheduling. Tasks share many
properties of tenant systems, however they are finer grained objects,
may have a shorter lifetimes, and are likely created in greater
numbers. Appendix C provides more detail and motivation for
virtualizing tasks using ILA.
6.1.3 Mobile networks
ILA may be applied as a solution for mobility in mobile networks
(such as cellular networks). In mobile networks, devices such as
smart phones move physically within the network. When a device moves
it changes its point of attachment in the network. The goal of
mobility is to provide a seamless transition when a device moves from
one attachment point to another. Appendix D provides more detail and
motivation for ILA in wireless networks.
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Each mobile device in a network may be assigned one or more
identifiers to use in communications. The ILA mapping table has an
entry for each identifier that maps to a locator indicating the
current network point of attachment for the device. Nodes that send
to the device set the locator per the mapping. When a mobile device
moves to a new attachment point, then mapping table entries all of
its associated identifiers are updated with a new locator.
6.2 Alternative methods
This section discusses the merits of alternative solution that have
been proposed to provide network virtualization or mobility in IPv6.
6.2.1 ILNP
ILNP splits an address into a locator and identifier in the same
manner as ILA. ILNP has characteristics, not present in ILA, that
prevent it from being a practical solution:
o ILNP requires that transport layer protocol implementations must
be modified to work over ILNP.
o ILNP can only be implemented in end hosts, not within the
network. This essentially requires that all end hosts need to be
modified to participate in mobility.
6.2.2 Flow label as virtual network identifier
The IPv6 flow label could conceptually be used as a 20-bit virtual
network identifier in order to indicate a packet is sent on an
overlay network. In this model the addresses may be virtual addresses
within the specified virtual network. Presumably, the tuple of flow-
label and addresses could be used by switches to forward virtually
addressed packets.
This approach 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.
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o The flow label is not part of the pseudo header for transport
checksum calculation, so it is not covered by any transport (or
other) checksums.
6.2.3 Extension headers
To accomplish network virtualization an extension header, such as a
destination or routing option, could be used that contains the
virtual destination address of a packet. The destination address in
the IPv6 header would be the topological address for the location of
the virtual node. Conceivably, segment routing could be used to
implement network virtualization in this manner.
This technique has some issues:
o Intermediate devices must not insert extension headers
[RFC8200].
o Extension headers introduce additional packet overhead which may
impact performance.
o Extension headers are not covered by transport checksums (as the
addresses 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.
6.2.4 Encapsulation techniques
Various encapsulation techniques have been proposed for implementing
network virtualization and mobility. LISP is an example of an
encapsulation that is based on locator identifier separation similar
to ILA. The primary drawback of encapsulation is complexity and per
packet overhead. For instance, when LISP is used with IPv6 the
encapsulation overhead is fifty-six bytes and two IP headers are
present in every packet. This adds considerable processing costs,
requires considerations to handle path MTU correctly, and certain
network accelerations may be lost.
7 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.
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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
addressing should be used with stronger security and isolation
mechanisms such as IPsec or GUESEC.
8 IANA Considerations
There are no IANA considerations in this specification.
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9 References
9.1 Normative References
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, DOI
10.17487/RFC8200, July 2017, <https://www.rfc-
editor.org/info/rfc8200>.
[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.
9.2 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.
[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.
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[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[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>.
[GUE] Herbert, T., and Yong, L., "Generic UDP Encapsulation",
draft-ietf-intarea-gue-04, work in progress.
[GUESEC] Yong, L., and Herbert, T. "Generic UDP Encapsulation (GUE)
for Secure Transport", draft-hy-gue-4-secure-transport-
03, work in progress
[ADDRPRIV] Herbert, T., "Privacy in IPv6 Network Prefix Assignment",
draft-herbert-ipv6-prefix-address-privacy-00
10 Acknowledgments
The authors would like to thank Mark Smith, Lucy Yong, Erik Kline,
Saleem Bhatti, Blake Matheny, Doug Porter, Pierre Pfister, Fred
Baker, 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; Kalyani Bogineni, Niranjan
Avula, Behcet Sarikaya, Dirk von-Hugo, and Ratul Guha for insights
regarding the mobility use case.
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Appendix A: Communication scenarios
This section describes the use of identifier-locator addressing in
several scenarios.
A.1 Terminology for scenario descriptions
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
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 SIR address with a locally unique identifier and 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 SIR addresses to ILA addresses
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for transmission on the network and back to SIR addresses at a
receiver has notation:
A,A -> L:I,A -> A,A
A.2 Identifier objects
Identifier-locator addressing is broad enough in scope to address
many different types of networking entities. For the purposes of this
section we classify these as "objects" and "tenant systems".
Objects encompass uses where nodes are address by local unique
identifiers (LUI). In the scenarios below objects are denoted by OBJ.
Tenant systems are those associated with network virtualization that
have virtual addresses (that is they are addressed by VNI:VA). In the
scenarios below tenant systems are denoted by TS.
A.3 Reference network for scenarios
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 objects with
identifiers O1, O2, and O3, as well as a common networking service
with identifier S1. 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 | | | +-------------+ |
| | OBJ O1 | | | +-----+-----+ | | | TS VNI2:VA3 | |
| +-------------+ | | | | | +-------------+ |
+-----------------+ | ............. | +-----------------+
+-----. .-----+
+-----------------+ . Underlay . +-----------------+
| Host L3 | +-----. Network .---+ | Host L4 |
| +-------------+ | | ............. | | +-------------+ |
| | OBJ O2 | | | | | | VM VNI2:VA4 | |
| +-------------+ +---+ +-----| +-------------+ |
| +-------------+ | | +-------------+ |
| | OBJ O3 | | | | Serv. S1 | |
| +-------------+ | | +-------------+ |
+-----------------+ +-----------------+
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Several communication scenarios can be considered:
1) Object to object
2) Object to Internet
3) Internet to object
4) Tenant system to local service
5) Object to tenant system
6) Tenant system to Internet
7) Internet to tenant system
8) IPv4 tenant system to service
9) Tenant system to tenant system same virtual network using IPv6
10) Tenant system to tenant system in same virtual network using
IPv4
11) Tenant system to tenant system in different virtual network
using IPv6
12) Tenant system to tenant system in different virtual network
using IPv4
13) IPv4 tenant system to IPv6 tenant system in different virtual
networks
14) Non-local address to tenant system
A.4 Scenario 1: Object to task
The transport endpoints for object to object communication are the
SIR addresses for the objects. 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:O1,SIR:O2 -> // Transport endpoints on O1
SIR:O1,L3:O2 -> // ILA used on the wire
SIR:O1,SIR:O2 // Received at O2
A.5 Scenario 2: Object to Internet
Communication from an object 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 object O1 is sending to an address Iaddr on the Internet, the
packet addresses would be:
SIR:O1,Iaddr
A.6 Scenario 3: Internet to object
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An Internet host transmits a packet to a task using an externally
routable SIR address. The SIR prefix routes the packet to a gateway
for the datacenter. The gateway translates the destination to an ILA
address.
If a host on the Internet with address Iaddr sends a packet to object
O3, the ILA translation sequence would be:
Iaddr,SIR:O3 -> // Transport endpoint at Iaddr
Iaddr,L1:O3 -> // On the wire in datacenter
Iaddr,SIR:O3 // Received at O3
A.7 Scenario 4: Tenant system to service
A tenant can communicate with a datacenter service using the SIR
address of the service.
If TS VA1 is communicating with service S1, the ILA translation
sequence would be:
VNET:VA1,Saddr-> // Transport endpoints in TS
SIR:(VNET:VA1):Saddr-> // On the wire
SIR:(VNET:VA1):Saddr // Received at S1
Where VNET is the address prefix for the tenant and Saddr is the IPv6
address of the service.
The ILA translation sequence in the reverse path, service to tenant
system, would be:
Saddr,SIR:(VNET:VA1) // Transport endpoints in S1
Saddr,L1:(VNET:VA1) // On the wire
Saddr,VNET:VA1 // Received at the TS
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.
A.8 Scenario 5: Object to tenant system
An object can communicate with a tenant system through it's
externally visible address.
If object O2 is communicating with TS VA4, the ILA translation
sequence would be:
SIR:O2,VNET:VA4 -> // Transport endpoints at T2
SIR:O2,L4:(VNI2:VAX4) -> // On the wire
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SIR:O2,VNET:VA4 // Received at TS
A.9 Scenario 6: Tenant system 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
A.10 Scenario 7: Internet to tenant system
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 datacenter. 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:
Iaddr,VNET:VA4 -> // Endpoint at Iaddr
Iaddr,L4:(VNI2:VAX4) -> // On the wire in datacenter
Iaddr,VNET:VA4 // Received at TS
A.11 Scenario 8: IPv4 tenant system to object
A TS that is IPv4-only may communicate with an object using protocol
translation. The object 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 object O3, the ILA translation sequence
would be:
VA2,ADDR3 -> // IPv4 endpoints at TS
SIR:(VNI1:VA2),L3:O3 -> // On the wire in datacenter
SIR:(VNI1:VA2),SIR:O3 // 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 object O3 communicate with TS VA2, the ILA translation sequence
would be:
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SIR:O3,SIR:(VNI1:VA2) -> // Endpoints at T4
SIR:O3,L2:(VNI1:VA2) -> // On the wire in datacenter
ADDR4,VA2 // IPv4 endpoint at TS
A.12 Tenant to tenant system 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.
A.12.1 Scenario 9: TS to TS in the 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
A.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
Note that the SIR is chosen by an ILA node as an appropriate SIR
prefix in the underlay network. Tenant systems do not use SIR address
for this communication, they only use virtual addresses.
A.13 Tenant system to tenant system in 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.
A.13.1 Scenario 11: TS to TS in 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
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Note that this assumes that VNET1 and VNET2 are globally routable
between the two virtual networks.
A.13.2 Scenario 12: TS to TS in different VNs using IPv4
To allow IPv4 tenant systems in different virtual networks to
communicate with each other, an address representing the peer would
be mapped into each 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.
A.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 TS VA4 using IPv4 to communicate with TS 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.
In the reverse direction, TS VA1 using IPv6 would communicate with TS
VA4 with the translation sequence:
VNET1:VA1,SIR:(VNI2:VA4) // Endpoint at VA1
VNET1:VA1,L4:(VNI2:VA4) // On the wire
SADDR1,VA4 // Received at VA4
A.14 Scenario 14: Non-local address to tenant system
A tenant system may have a global address that is non-local to the
network. A host on the Internet or a tenant system may send packet to
this address. The packet is forwarded by some means to a gateway or
other ILA node (tunneling could be used to accomplish this). An ILA
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node can crate a an ILA address for this using a non-local address
identifier.
For a node sending to a non-local address that is an address of task
T2, the ILA translation sequence would be:
SADDR,A // Endpoint at a host
SADDR,L3:X // On the wire
SADDR,A // Received by TS 2
Note that A is the non-local address, and X is is an identifier that
maps to the non-local address.
Appendix B: unique identifier generation
The unique identifier type of ILA identifiers can address 2**60
objects (assuming the typed identifier format is used as described in
section 4). This appendix describes some method to perform allocation
of identifiers for objects to avoid duplicated identifiers being
allocated.
B.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.
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.
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
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determining the probability of identifier collision.
B.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 object 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 unique
identifiers for objects could be created autonomously by the host.
The identifier might be composed of a twenty-four bit host identifier
followed by a thirty-six bit timestamp. Assuming that a host can
allocate up to 100 identifiers per second, this allows about 21.8
years before wrap around.
/* LUI identifier with host registrar and timestamp */
|3 bits|1| 24 bits | 36 bits |
+------+-------------------+-------------------------------------+
| 0x1 |C| Host identifier | Timestamp Identifier |
+----------------------------------------------------------------+
Appendix C: Datacenter task virtualization
This section describes some details to apply ILA to virtualizing
tasks in a datacenter.
C.1 Address per task
Managing the port number space for services within a datacenter 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.
With ILA, each service task can be assigned its own IPv6 address and
therefore will logically be assigned the full port space for that
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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.
C.2 Job scheduling
In the usual datacenter 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 datacenter in terms utilization, cost, latency, etc. Datacenter
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.
C.3 Task migration
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.
This model similar to virtual machine (VM) migration except that the
runtime state is typically much less data-- just task state as
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opposed to a full OS image. Task state may be compressed to reduce
latency in migration.
C.3.1 Address migration
ILA facilitates address (specifically identifier address) 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 ICMP destination
unreachable when packets to the migrated address are received.
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 resolution protocol.
C.3.2 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.
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Appendix D: Mobility in wireless networks
ILA can be used in public wireless networks to provide a solution for
mobility.
Devices in a carrier network are referred to as User Equipment (UE)
and can include smart phones, automobiles, and other IoT devices. UEs
attach to provider network at base stations (eNodeB in carrier
terminology). As the device moves, it may change it's point of
attachment to a geographically close base station. A cellular network
is composed of cells each of which has an eNodeB.
A node may change cells several times over a time period. In order to
provide seamless communications it is desirable that the existing
connections of the device are preserved. ILA provides for this by
assigning SIR addresses to UEs and deploying ILA routers in the
network infrastructure.
In a canonical architecture each base station (eNodeB) would have an
ILA router, and there would be a number of ILA routers that serve as
gateways between a provider's network and the Internet. When a host
on the Internet sends to a UE's SIR address, a gateway ILA router
will translate the address. The locator addresses the base station
that is the current point of attachment. At the base station ILA
router, the destination is transformed back to a SIR address and
delivered to a UE. A similar process can happen when two UEs in the
network communicate.
The wireless network use case is conceptually similar to network
virtualization. In both scenarios, nodes have a point of attachment
and can move to other points of attachment. The difference is that in
network virtualization it is virtual machines that are mobile, in
wireless networks it is real devices.
The wireless use case has some unique properties:
o These are often public networks so that privacy is a
consideration. It is likely that devices may have many addresses
assigned to promote privacy. Strong privacy addresses may be
needed [ADDRPRIV].
o A single device might have many identifiers assigned to it. When
a device moves, all of the identifiers must change to map to the
same locator.
o Devices move on their own accord so that mobility is
unpredictable.
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o There are mostly real humans using devices so that human
identity and exposing geo location are concerns.
Author's Address
Tom Herbert
Quantonium
4701 Patrick Henry Dr.
Santa Clara, CA
EMail: tom@herbertland.com
Petr Lapukhov
1 Hacker Way
Menlo Parck, CA
EMail: petr@fb.com
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