Internet DRAFT - draft-thubert-v6ops-yada-yatt
draft-thubert-v6ops-yada-yatt
v6ops P. Thubert, Ed.
Internet-Draft Cisco Systems
Updates: 1122, 4291 (if approved) 11 April 2022
Intended status: Informational
Expires: 13 October 2022
Yet Another Double Address and Translation Technique
draft-thubert-v6ops-yada-yatt-04
Abstract
This document provides a stepwise migration between IPv4 and IPv6
with baby steps from an IPv4-only stack/gateway/ISP to an IPv6-only
version, that allows portions of the nodes and of the networks to
remain IPv4, and reduces the need for dual stack and CG NATs between
participating nodes. A first mechanism named YADA to augment the
capacity of the current IPv4 Internet by interconnecting IPv4 realms
via a common footprint called the shaft. YADA extends RFC 1122 with
the support of an IP-in-IP format used to forward the packet between
parallel IPv4 realms. This document also provides a stateless
address and IP header translation between YADA and IPv6 called YATT
and extends RFC 4291 for the YATT format. The YADA and YATT formats
are interchangeable, and the stateless translation can take place as
a bump in the stack at either end, or within the network at any
router. This enables an IPv6-only stack to dialog with an IPv4-only
stack across a network that can be IPv6, IPv4, or mixed. YATT
requires that the IPv6 stack owns a prefix that derives from a YADA
address and that the IPv4 stack in a different realm is capable of
YADA, so it does not replace a generic 4 to 6 translation mechanism
for any v6 to any v4.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 13 October 2022.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Extending RFC 1122 . . . . . . . . . . . . . . . . . . . . . 7
5. Extending RFC 2131 . . . . . . . . . . . . . . . . . . . . . 8
6. Extending RFC 4291 . . . . . . . . . . . . . . . . . . . . . 8
7. Extending RFC 8415 . . . . . . . . . . . . . . . . . . . . . 8
8. YADA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9. YADA Stateful NAT . . . . . . . . . . . . . . . . . . . . . . 12
10. YATT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11. YATT Stateful PAT . . . . . . . . . . . . . . . . . . . . . . 16
12. The structure of the shaft . . . . . . . . . . . . . . . . . 17
13. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 18
14. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 19
15. Security Considerations . . . . . . . . . . . . . . . . . . . 19
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
18.1. Normative References . . . . . . . . . . . . . . . . . . 20
18.2. Informative References . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction and Motivation
At the time of this writing, the transition to IPv6 started 20 years
ago and large amounts of networks, hosts, and programs, are still
IPv4-only. The IPv4 and IPv6 camps are quite entrenched, and there's
no indication that things will change any time soon.
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During that endless transition, stacks must implement both protocols
(aka dual stack) and a mechanism to use either based on the
responsiveness (Happy Eyeballs). Service Providers must implement
heavy weaponry called Carrier-Grade Network Address Translators (CG-
NATs) to translate between protocols between legacy IPv4-only and
IPv6-only stacks, and tunneling techniques such as DS-Lite [RFC7333]
and 464XLAT [RFC6877] to traverse portions of the network that
support only one of the IP versions. This means both CAPEX to
install dual stack infrastructures and NAT devices and OPEX to
maintain them. The current situation is often qualified as the worst
of both worlds and any indications is that it's here to stay, till
each side suffered enough and is ready for a compromise.
This document prepares for that time where the players will
effectively be ready for a compromise. An acceptable compromise must
provide both sides with way to remain as long as desired, while
eliminating the need for dual stack and CG-NATs between participating
nodes. Certainly, an effort must be asked on each side to reduce the
chasm, and that effort must come with enough benefits to effectively
encourage a majority of interested parties to make the step.
Yet Another Double Address (YADA) refers to effort that is asked from
the IPv4 side to support a new IP-in-IP model. YADA extends
[INT-ARCHI] with the support of an IP-in-IP format used to forward
the packet between parallel IPv4 realms. The proposed benefit is a
thousandfold increase of the IPv4-addressable domain by building
parallel realms each potentially the size of the current Internet.
Only the stacks that need to talk to a parallel realm need to evolve.
Routing and forwarding can remain IPv4-only with the same operations
as today, though new routers with YADA capabilities must be deployed
to route between realms.
Yet Another Translation Technique (YATT) refers to an effort to be
made by the IPv6 side to support a new IPv6 Prefix with special
properties, which impacts in particular source address selection
(SAS). YATT extends [IPv6-ADDRESSING] for the YATT format. The
proposed benefit is a prefix (say /32) per realm and a prefix (say
/64) per host in the realm. This address space may for instance
become handy for load balancing between physical servers / VMs / pods
that operate a service associated with the virtual server that owns
the host prefix.
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The YADA and YATT formats are interchangeable, which means that the
translation is stateless and can take place as a bump-in-the-stack at
either end or can be operated at line rate anywhere in the network by
an upgraded hardware. The routers that connect the shaft also
perform a stateless operation that can be achieved at line rate by
upgraded hardware. This is how the chasm between IPv4 and IPv6 can
be reduced, removing the need to deploy dual stack and CG-NATs
between participating nodes.
This document provides a stepwise migration between IPv4 and IPv6
with baby steps from an IPv4-only stack/gateway/ISP to YADA to YATT
to an IPv6-only version. The migration strategy allows portions of
the nodes and of the networks to remain IPv4.
YATT requires that the IPv6 stack owns a prefix that derives from a
YADA address associated to a realm, even if there's absolutely no
IPv4 operation taking place in that realm. The resulting
connectivity without dual stack and CG-NAT is as follows:
* A legacy IPv4-only node can only talk within its realm. It can
talk to an IPv4 legacy node, a YADA IPv4-only node, and even a
YATT IPv6-only node, e.g., leveraging a bump-in-the-stack in the
YATT node if the access network is IPv4-only.
* In addition, a YADA IPv4-only node can talk across realms to a
YADA IPv4-only node and to any YATT IPv6-only node, e.g.,
leveraging a bump-in-the-stack in the YADA node if the network is
IPv6-only.
* In addition, a YATT IPv6-only node can talk to any other IPv6-only
node.
Connectivity between an IPv4-only node and an IPv6-only node, or
between an IPv4-only node and a YADA node in different realm, still
requires a CG-NATs as of today, e.g., using the YATT format for the
IPv6 side in an unmodified CG-NAT.
2. Terminology
2.1. Glossary
This document often uses the following acronyms:
YADA: Yet Another Double Address
YATT: Yet Another Translation Technique
NAT: Network address Translation
IID: Interface ID
CG-NAT: Carrier Grade NAT
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2.2. New Terms
This document often uses the following new terms:
IPv4 realm: A full IPv4 network like the current Internet. YADA
does not affect the traditional IPv4 operations within a realm.
The shaft: The shaft refers to a collection of IPv4 unicast and
multicast prefixes that are assigned to Inter-realm communications
and cannot be assigned to hosts or multicast groups within a
realm.
Realm address: An IPv4 address that derives from a shaft prefix.
Uni-realm address: A realm address that is unicast or anycast. A
realm may have more than one Uni-realm add ress.
Multi-realm address: A realm address that is multicast and denotes a
collection of realms.
YADA realm prefix: A prefix assigned to the shaft and from which
realm addresses can be derived.
YADA NAT prefix: A prefix assigned to the YADA bump-in-the-stack NAT
operation.
Double-A or YADA address: A YADA address is a tuple (realm address,
IPv4 address) where the IPv4 address is only significant within
the realm denoted by the realm address.
YATT Space: An IPv6 range that is assigned for YATT operation.
YATT prefix: An IPv6 prefix that is derived from a YADA address by
appending the YATT space prefix, the (truncated) realm address and
the IPv4 address.
YATT-IID: A 64-bit assigned constant that is used in YATT to
statelessly form an IPv6 address from a YATT prefix.
Multinternet: A collection of IPv4 realms interconnected using a
common shaft.
3. Overview
This document provides a stepwise migration between IPv4 and IPv6
with baby steps from an IPv4-only stack/gateway/ISP to an IPv6-only
version. The baby steps reduce the gap between the only versions and
the associated need for dual stack and CG-NATs.
This first mechanism called YADA allows to grow the Internet beyond
the current IPv4 [IPv4] realm that limits its capacity to form public
addresses. Depending on the assignments to be made, the model allows
to reuse all IP addresses and all Autonomous System Number (ASN)
currently available in the internet hundreds to millions of times.
This is achieved by interconnecting IPv4 realms via a common
footprint called the shaft.
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In the analogy of a building, the ground floor would be the Internet,
and each additional floor would be another IPv4 realm. The same
surface of floor is available in each level, analog to the full IPv4
addressing that is available in each realm. The same footprint is
dedicated across the building levels for the elevator shaft. The
elevator shaft enables a third dimension that spans across the levels
and allows to traverse from any level to any other level. The
elevator shaft cannot be used for living or office space.
/------------------------------------------------------
/ /
/ |------------| realm 1 /
/ /. /. /
/ / . shaft / . (current IPv4 Internet) /
/ |------------| . /
/ . . . . /
------------------------------------------------------/
| . | |
/-----|------------|--|--------------------------------
/ | . | | /
/ | |---------|--| realm 2 /
/ | /. | /. /
/ |/ . shaft |/ . /
/ |------------| . /
/ . . . . /
------------------------------------------------------/
| . | |
| . | |
| | .
| | .
. . |
. . |
| . | |
/-----|------------|--|--------------------------------
/ | . | | /
/ | |---------|--| realm N /
/ | / | / /
/ |/ shaft |/ /
/ |------------| /
/ /
------------------------------------------------------/
Figure 1: The shaft
By analogy, YADA assigns IPv4 prefixes to a multinternet shaft; those
prefixes are common across the realms that are interconnected by the
shaft. A single /24 IPv4 prefix assigned allows for > 250 times the
capacity of the Internet as we know it at the time of this writing.
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Multiple prefixes can be assigned to the shaft for unicast and
multicast communications, and each realm needs at least one unicast
address in the shaft called its realm address. A YADA address is
formed by the tuple (realm address, IPv4 address) and is advertised
in DNS as a new double-A record.
YADA leverages IP-in-IP encapsulation to tunnel packets across the
shaft while normal IPv4 operations happen within a realm. YADA
requires a change in the stack in the YADA endpoints that communicate
with other realms to support the IP-in-IP YADA encapsulation. YADA
also provides a bump in the stack method for legacy applications.
More in Section 9.
A second mechanism called YATT translates the YADA format into flat
IPv6 [IPv6]. While a YADA address pair can be seen as some foot
print in one level, the YATT prefix encompasses that same foot print
plus all the air above it. For unicast addresses, YATT forms an IPv6
prefix by collating an well-known assigned short prefix, the realm
address (in the shaft), and the host IPv4 address (locally
significant within the realm). The resulting IPv6 prefix is
automatically owned by the host that owns the IPv4 address in the
realm. YATT then forms an IPv6 address for that host by collating a
well-known Interface ID, so there's a one-to-one relationship between
the YADA and the IPv6 address derived from it. More in Section 10.
A key concept for this specification is that YADA (the IPv4
formulation) and YATT (the IPv6 formulation) are alternative
representations of the same abstract object (a double address), which
can serve as an intermediate step across the IPv4-IPv6 chasm. The
IPv4 formulation (YADA) is a plain IP-in-IP with no new extension.
The IPv6 formulation (YATT) uses a standard IPv6 header with a
special encoding of the addresses. The formulations are
interchangeable; if a link supports both IP versions then the next
hop is valid for both formulations, whichever of the 2 Address
Families (AFs) was used to learn it; else any node can convert one
formulation to the other to accomodate the IP version that is
available on the next hop link.
4. Extending RFC 1122
YADA extends [INT-ARCHI] to add the capability for an IPv4 host to
recognize an special IP-in-IP format as an inter-realm IPv4 packet
and process it accordingly. It also adds a new DNS double-A record
format that denotes a YADA address.
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5. Extending RFC 2131
The Dynamic Host Configuration Protocol [RFC2131] (DHCP) is extended
to pass information to the host about its current realm. When this
information is present, the host is free to use YADA using that
realms as source realm.
If a host obtains a public address from DHCP, and for the duration of
the lease, the host automatically owns the YATT prefix associated to
a owned YADA address. In this manner, DHCPv4 becomes an alternate
method for delegating an IPv6 prefix from which the host may
provision an IPv6 stack.
6. Extending RFC 4291
YATT extends the IPv6 Addressing Architecture [IPv6-ADDRESSING] to
add the capability for a host to recognize an special IPv6 format as
an YATT address embedding a YADA address and process it accordingly.
This is achieved in particular by the allocation of a YATT space that
is a short prefix for all YATT prefixes, and a YATT-IID.
7. Extending RFC 8415
The DHCPv6 prefix delegation mechanism in Dynamic Host Configuration
Protocol for IPv6 [RFC8415] is extended to delegate YATT prefixes to
the hosts by enforcing that a delegated YATT prefix is provided in
the form defined by Section 6.
8. YADA
YADA assigns IPv4 prefixes to a multinternet shaft; those prefixes
must be the same across all the realms that are interconnected by the
shaft. Multiple prefixes can be assigned to the shaft for unicast
and multicast communications, and each realm needs at least one
unicast address in the shaft called its realm address. A YADA
address is formed by the tuple (realm address, IPv4 address) and is
advertised in DNS as a new double-A record. Because the YADA
prefixes are assigned for YADA, a packet that has either source or
destination IPV4 address derived from a shaft prefix is a YADA
packet.
YADA leverages IP-in-IP encapsulation to tunnel packets across the
shaft for inter-realm communications, while the IPv4 operations
within a realm are unaffected. The YADA address is found by using
both inner and outer header and combining that information. The pair
of IP headers is seen by a YADA stack as a single larger header
though a non-YADA forwarder only needs the outer header and plain
IPv4 operations on the outer IPv4 header to forward.
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YADA requires a change in the stack in the YADA endpoints that
communicate with other realms to support the YADA encapsulation. A
stack that resolve a DNS name with a double-A record indicating a
different realm generates an IP-in-IP packet to signal both the
source and destination realms and the source and destination IPv4
addresses within the respective realms.
Inside the source realm, the outer IPv4 header indicates the node's
IPv4 address as source, to remain topologically correct, and the
local realm address as source in the inner header, as shown in
Figure 2
<----------------------------- 20 bytes ---------------------------->
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source node | destination realm |
| (outer) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source realm | destination node |
| (inner) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
. Options .
+------------ ... --------------------------------------------------+
| |
. Data .
| |
+-------------------------------------------------------------------+
Figure 2: YADA format in the source realm
YADA also requires a change for the routers that serve the shaft.
Those routers play a special role for packets that are delivered from
the shaft to the destination realm, and for ICMP errors across
realms. All other IPv4 nodes in the realm continue to operate
routing and forwarding as before.
Routers serving the shaft advertise the shaft prefix(es) in their
respective realms, and their realm addresses within the shaft, as
host routes for unicast and anycast addresses.
Inside the source realm, the IPv4 destination in the outer header is
an address is the shaft and it is attracted by a router that serves
the shaft in the source realm. The packet source in the outer header
is the address of the source node in the local realm, so the packet
does not defeat BCP 38 rules in the ISP network, as shown in
Figure 3.
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| |
/------|------------|---------------------------------
/ | | /
/ | | | | /
/ | |--------|---| Source Node /
/ | / | / /
/ | /. <--|---- outer(src=src-addr /
/ |/ . |/ . dst=dst-realm) /
/ |------------| . inner(src=src-realm /
/ . . . . dst=dst-addr) /
/ . . . . /
/ . . . . /
-----------------------------------------------------/
| | |
| |
| |
Figure 3: Packets Entering the shaft
When the packet reaches the shaft, the router that serves the shaft
in this realm checks that packet source in the inner header is an
address of this realm, and if so, it swaps the inner and outer source
IPv4 address, and forwards the packet down the shaft. this way, the
the packet remains topologically correct inside the shaft, as shown
in Figure 4.
<----------------------------- 20 bytes ---------------------------->
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source realm | destination realm |
| (outer) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source node | destination node |
| (inner) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
. Options .
+------------ ... --------------------------------------------------+
| |
. Data .
| |
+-------------------------------------------------------------------+
Figure 4: YADA format inside the shaft
Based on longest match, the router forwards the packet inside the
shaft following the host route to a router that serves the
destination realm, as shown in Figure 5.
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| |
/------|------------|---------------------------------
/ | | /
/ | | | | /
/ | |--------|---| Source Node /
/ | / | /. /
/ | /. +- | / . outer(src=src-realm /
/ |/ . | |/ . dst=dst-realm) /
/ |------------| . inner(src=src-addr /
/ . . | . . dst=dst-addr) /
/ . . | . . /
/ . . | . . /
-----------------------------------------------------/
| | | |
| | |
| | | Sources swapped at shaft ingress
v
Figure 5: Packets Entering the shaft
That router swaps the destination address in the inner and outer
headers and forwards within its realm to the final destination, as
shown in Figure 6.
<----------------------------- 20 bytes ---------------------------->
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source realm | destination node |
| (outer) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
| IPv4 header fields | Source node | destination realm |
| (inner) | IPv4 Address | IPv4 Address |
+------------ ... ------------+-----------------+-------------------+
. Options .
+------------ ... --------------------------------------------------+
| |
. Data .
| |
+-------------------------------------------------------------------+
Figure 6: YADA format in the destination realm
In normal conditions, the stack of the destination node recognizes
the YADA format and replies accordingly.
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| |
| |
/------|------------|---------------------------------
/ | | | | /
/ | | | | | /
/ | |----|---|---| Destination Node /
/ | / | | /. /
/ | /. +---|----> outer(src=src-realm /
/ |/ . |/ . dst=dst-addr) /
/ |------------| . inner(src=src-addr /
/ . . . . dst=realm-addr) /
/ . . . . /
/ . . . . /
-----------------------------------------------------/
destinations swapped at shaft egress
Figure 7: Packets Outgoing the shaft
In case of an error down the shaft or in the destination realm, if an
ICMP message is generated by a node that is not YADA-aware, the
message reaches the router that serves the shaft in the source realm.
If the inner header is present in the ICMP payload, then the Router
extracts it and forwards to the packet source. If the destination
stack does not support YADA and decapsulates, the message reaches the
router that serves the destination realm which logs and drops. based
on the log, the node may be updated, or the DNS records may be fixed
to avoid pointing on a node that does not support YADA.
YADA was initially published as USPTO 7,356,031, filed in February
2002.
9. YADA Stateful NAT
Inside a realm, a YADA stack falls back to classical IPv4 operations
and will natively connects to any legacy IPv4 peers. To reach YADA
nodes in alternate realms, YADA also provides a stateful NAT
operation that performs an IPv4-to-YADA translation below the legacy
stack. The translation reuses some prefix space allocated for either
[RFC1918] or [RFC6598] for a local NAT pool that is used to present a
single address to the legacy stack.
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The YADA formulation couples a realm address with a public IPv4
address. A host that owns a public address may perform the YADA
stateful NAT operation as a bump-in-the-stack below the legacy stack.
In a private network, the operation is preferably done in the private
gateway, outside the existing private-public NAT so it operates on
the resulting public address, to keep the classical NAT operation as
is.
+-------------+
| |
| | +-------------+
+-------------+ | address |
| IPv4 | | pool |
| stack | +-------------+
+-------------+ +------------------------+
| | | bump in stack stateful |
| | | IPv4 -> YADA NAT |
+-----+-------+ +--------------------+---+
| ^ |
v | v
+---------------+------+--------+ +-------------------------------+
| src=this_node | dst=from_pool | | src=this_node | dst=dst-realm |
+---------------+---------------+ +---------------+---------------+
| | |src=this_realm |dst=destination|
| | +---------------+---------------+
| | | |
| IP PAYLOAD | | |
| | | |
| | | IP PAYLOAD |
| | | |
+-------------------------------+ | |
| |
+----------------+--------------+
|
V
Figure 8: YADA Stateful NAT
The stateful NAT intercepts the DNS lookups. If the response
contains an A record, then the address is reachable in the local
realm and the NAT ignores that destination, letting the legacy
operations take place transparently.
When the response yields a double-A record with a foreign realm, the
stateful NAT allocates an IPv4 address from the local NAT pool and
adds it in an A record to the DNS response. A local NAT state is
built, indexed by the double-A outside and the allocated single-A
inside.
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When the legacy stack pushes a packet to that particular address, the
stateful NAT translates to the YADA format, using the information in
the double-A record for the destination, and the local realm as
source realm.
The other way around, if a packet arrives in the YADA formulation
from a different realm, the stateful NAT allocates an address from
the pool, and NATs to classical IPv4 using that address as source.
As an optimization, a NAT in a private gateway may learn which nodes
inside support YADA and bypass the YADA stateful NAT operation
completely for those nodes.
As long at the bump-in-the-stack (or the gateway) generates YADA
packets, the packets can be translated statelessly to YATT as a last
bump-in-the-stack operation before transmission to be pushed on an
IPv6-only link.
The YATT and YADA formulations refer to the same object. A node that
is configured with a YATT address is de facto owner of the embedded
IPv4 address within the embedded IPv4 realm, and that address can be
used to install a legacy IPv4 stack even if the attachement link is
pure IPv6. As long at the stack generates YADA packets, the packets
can be translated statelessly to YATT as a next bump-in-the-stack
operation before transmission and placed on the IPv6-only network.
10. YATT
A second mechanism called YATT translates the YADA format into flat
IPv6.
+-----+---------------+--------------+-----------------------------+
|YATT | Realm | IPv4 | Well-Known |
|Space| Address | Address | IID |
+-----+- -------------+--------------+-----------------------------+
<- YADA
prefix ->
<-------- YATT prefix ---------->
Figure 9: YATT format
For unicast addresses, YATT forms an IPv6 prefix by collating an
well-known assigned short prefix called the YATT space, the realm
address, and the host IPv4 address (locally significant within the
realm). The resulting IPv6 prefix is automatically owned by the host
that owns the IPv4 address in the realm.
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Depending on assignment, the leftmost piece realm prefix may be
truncated if it is well-known, to allow the YATT space and the realm
address to fit in a 32-bit DWORD. This way, the YATT prefix can be a
full /64 prefix that is entirely owned by the host that owns the
associated YADA address.
YATT then forms an IPv6 address for that host by collating a well-
known Interface ID, so there's a one-to-one relationship.
The formats can not be strictly provided till the YATT space and YADA
prefix are assigned. But say that the YATT Space is F000::/6 and the
YADA prefix is 240.0.0.0/6. In that case the values perfectly
overlap and the YATT format becomes as follows:
+-----+----------+----------------+---------------------------------+
| Realm Address | IPv4 Host | Well-Known |
| in 240.0.0.0/6 | Public Address | IID |
+-----+- --------+----+-----------+---------------------------------+
<--- 32 bits ---><--- 32 bits ---><------------ 64 bits ------------>
<------ YATT IPv6 prefix ------->
Figure 10: YATT format using 240.0.0.0/6
In that case, the NAT operation is a plain insertion. Depending on
the assignment, it might be that the Realm address must be placed in
full after YATT space. In that case, the length of the YATT prefix
will be more than 64 bits.
Also, since 240.0.0.0/6 is currently unassigned, using it for the
shaft would allow literally to reuse every ASN and every IPv4 address
currently available in the Internet in each and every other realm and
reallocate them in any fashion desirable in that realm.
If the network supports IPv6 to the shaft, it makes sense for the
YADA host or the bump-in-the-stack to generate the packets in the
YATT form natively. The shaft router must then attract the shaft
YADA realm prefix in both IPv4 and YATT forms.
If the network is IPv4 only, the packets are still generated using
IP-in-IP, and the YATT NAT operation may happen at the router that
delivers the packet in the destination realm, if it is v6-only, or in
the destination host, if its stack is v6-only.
YATT was initially published as USPTO 7,764,686, filed in December
2002.
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11. YATT Stateful PAT
The YATT and YADA formulations refer to the same object. A node that
is the owner of a public address in a realm is de facto owner of the
matching YATT prefix, and is de facto assigned the IPv6 address
derived with the YATT-IID. The other way around, a node that is
delegated a YATT prefix is de facto owner of the embedded IPv4
address within the embedded IPv4 realm.
In an IPv4-only environment, a YATT stack may obtain a YADA address
pair from DHCPv4 (see Section 5), derive a YATT prefix, and use it to
configure the local IPv6 stack. As long at the stack generates YATT
packets, the packets can be translated statelessly to YADA as a last
bump-in-the-stack operation before transmission. In that model,
lower-layer protocols such as ARP and DHCP must be supported, but the
IP stack can be IPv6-only.
In that case, the node shows as a YADA node, and may talk to a legacy
IPv4 stack in a remote realm if the legacy that supports the YADA
stateful translation. This combination of stateful PAT after the
IPv6 stack and stateful NAT after the IPv4 stack allow the 2 stacks
to communicate in the YADA/YATT formulations, and traverse IPv4-only
and IPv6-only links using the appropriate formulation.
The YATT node may use the YATT prefix to autoconfigure addresses, or
it may offer it on an IPv6 stub (tethered) network for address
autoconfiguration by attached nodes, protecting the addresses that it
keeps for itself using in the DAD procedure. Addresses that are not
derived from the YATT-IID will be reachable from IPv6 nodes over an
IPv6 network, but not from YADA node, and not over IPv4-only links.
To reach YADA nodes and traverse IPv4, the YATT node may leverage a
stateful Port Address Translation (PAT) to transform the original IID
in the YATT-IID outside. The stateful PAT operation can happen as a
bump-in-the-stack before the YATT-to-YADA stateless translation.
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+-------------+
| |
| | +----------+
+-------------+ | port |
| IPv6 | | pool |
| stack | +----------+
+-------------+ +------------------------+
| | | bump in stack stateful |
| | | IPv6 -> YATT PAT |
+-----+-------+ +--------------------+---+
| ^ |
v | v
+----------------------+--------+ +-------------------------------+
| src_prefix (YATT) ; IID = any | | src_prefix ; IID = YATT-IID |
+-------------------------------+ +-------------------------------+
| dst (other YATT address) | | dst |
+-------------------------------+ +-------------------------------+
+-------------------------------+ +-------------------------------+
| srcport = Selected ; dport | | srcport = Translated ; dport |
+-------------------------------+ +-------------------------------+
| | | |
| | | |
| | | |
| IP PAYLOAD | | IP PAYLOAD |
| | | |
| | | |
| | | |
+-------------------------------+ +---------------+---------------+
|
V
Figure 11: YATT Stateful PAT
12. The structure of the shaft
A 10 miles view of the shaft could be as follows: it is implemented
in one IXP, spans all realms, and each realm has one address in the
shaft, with one router serving that realm. The address of the realm
is encoded in a loopback in the router, and advertised through an IGP
inside the shaft, while BGP is used inside the realms but not inside
the shaft. The shaft has a single large prefix that is advertised in
each realm by the router that serves the shaft, and that is
disaggregated into host routes inside the shaft.
None of the above is expected to remain true for long. As YADA and
YATT get deployed, the shaft will be implemented in different sites
over the world. A realm may be multihomed to be reached from a
different physical instance of the shaft, meaning that the shaft is
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composed of either more prefixes or the shaft prefix is
disaggregated. Multiple routers will serve the same realm with high
availability and load balancing taking place inside the shaft to
maintain connectivity. A private shaft may be deployed to
interconnect a subset of the realms, in which case the shaft would
use a specific prefix that would not be advertised outside the
concerned realms.
13. Applicability
YADA And YATT enable communication between YADA-enabled IPv4 nodes
across realms, and with IPv6 nodes that own a YADA address from which
a YATT address can be derived. Communication from a legacy IPv4
application/stack that is not YADA-enabled, or to an IPv6 address
that is not a YATT address, is not provided.
Since the YATT translation is stateless, the header translation can
happen anywhere in the network, e.g., as a bump in the stack at
either end, or within the network, e.g., at the routers that serve
the realms on the shaft. The shaft itself is expected to be dual
stack to forward packets in their native form, either v4 or v6.
For a legacy IPv4 node to communicate with YADA-enabled IPv4 node in
another realm, a NAT operation similar to NAT46 [NAT-DEPLOY], but
between IPv4 and YADA addresses, is required. The same would be
required to allow an IPv4-only YADA node to communicate with an IPv6
node a non-YATT address.
In summary:
* this specification does not allow any IPv4 legacy node to talk to
any pure IPv6 node, and recognizes that this Graal may actually be
a non-goal.
* With YADA the current IPv4 Internet operations within a realm are
not mostly unaffected, though additional provisionning is needed
for routing and security purposes
* YADA extends the IPv4-reachable world by creating (millions of)
parallel realms
* The stack on IPv4 hosts that require inter-realm communication
must be upgraded at least with a bump, though the function may be
deported to the private gateway
* A new functionality is needed in specific routers at the ingress
of the realms and at the border to a single-version domain for NAT
operation
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* A YADA node can talk (using IPv4) to a YATT node (using IPv6) with
a stateless translation. The translation can happen anywhere in
the network or in the stack.
14. Backwards Compatibility
YADA operation does not affect the intra-realm communication. The
only affected stacks are the endpoints that communicate between
realms leveraging YADA.
15. Security Considerations
YADA introduces an IP-in-IP format that might be used to obfuscate an
IP address impersonation performed in the inner header. A proper
implemetation of BCP 38 should thus include the capability to
recognize a YADA format and allow the source IP address in the inner
header to be set to the local realm.
Before the router that serves the realm swaps the source address to
place a YADA packet in the shaft, it MUST ensure that the realm
address in the inner header matches this realm. Otherwise it MUST
drop the packet and MAY generate and ICMP Error message back to the
source, indicating the offset of the source IP address of the inner
header.
16. IANA Considerations
This document requires the creation of a registry for IPv4 YADA realm
prefixes, and the assignment of at least one YADA realm prefix.
This document requires the creation of a registry for IPv4 YADA NAT
prefixes, and the assignment of at least one YADA NAT prefix.
This document requires the creation of a new record in the Resource
Record (RR) TYPEs subregistry of the Domain Name System (DNS)
Parameters. The new record would be of type AA meaning a YADA
address.
17. Acknowledgments
The author wishes to recognize the pioneer work done by Brian
carpenter in the space of IPv4 augmentation with
[I-D.carpenter-aeiou]
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The author wishes to thank Greg Skinner as the first reviewer/
contributor to this work. Also Dave Bell, to remind that even if
routing is not touched much inside an IPv4 realm vs. the current art,
there might still be work for the ISP, e.g., update the BCP 38 rules
in the BNGs.
18. References
18.1. Normative References
[IPv4] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[INT-ARCHI]
Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
[IPv6-ADDRESSING]
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[IPv6] 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>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
18.2. Informative References
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC 1918, DOI 10.17487/RFC1918,
February 1996, <https://www.rfc-editor.org/info/rfc1918>.
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[RFC6598] Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address
Space", BCP 153, RFC 6598, DOI 10.17487/RFC6598, April
2012, <https://www.rfc-editor.org/info/rfc6598>.
[RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation",
RFC 6877, DOI 10.17487/RFC6877, April 2013,
<https://www.rfc-editor.org/info/rfc6877>.
[RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
Korhonen, "Requirements for Distributed Mobility
Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,
<https://www.rfc-editor.org/info/rfc7333>.
[NAT-DEPLOY]
Palet Martinez, J., "Additional Deployment Guidelines for
NAT64/464XLAT in Operator and Enterprise Networks",
RFC 8683, DOI 10.17487/RFC8683, November 2019,
<https://www.rfc-editor.org/info/rfc8683>.
[I-D.carpenter-aeiou]
Carpenter, B. E., "Address Extension by IP Option Usage
(AEIOU)", Work in Progress, Internet-Draft, draft-
carpenter-aeiou-00, 21 March 1994,
<https://datatracker.ietf.org/doc/html/draft-carpenter-
aeiou-00>.
Author's Address
Pascal Thubert (editor)
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
06254 Mougins - Sophia Antipolis
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Thubert Expires 13 October 2022 [Page 21]
