Internet Engineering Task Force (IETF) G. Lencse
Request for Comments: 9313 BUTE
Category: Informational J. Palet Martinez
ISSN: 2070-1721 The IPv6 Company
L. Howard
Retevia
R. Patterson
Sky UK
I. Farrer
Deutsche Telekom AG
October 2022
Pros and Cons of IPv6 Transition Technologies for IPv4-as-a-Service
(IPv4aaS)
Abstract
Several IPv6 transition technologies have been developed to provide
customers with IPv4-as-a-Service (IPv4aaS) for ISPs with an IPv6-only
access and/or core network. These technologies have their advantages
and disadvantages. Depending on existing topology, skills, strategy,
and other preferences, one of these technologies may be the most
appropriate solution for a network operator.
This document examines the five most prominent IPv4aaS technologies
and considers a number of different aspects to provide network
operators with an easy-to-use reference to assist in selecting the
technology that best suits their needs.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9313.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction
2. Overview of the Technologies
2.1. 464XLAT
2.2. Dual-Stack Lite
2.3. Lightweight 4over6
2.4. MAP-E
2.5. MAP-T
3. High-Level Architectures and Their Consequences
3.1. Service Provider Network Traversal
3.2. Network Address Translation among the Different IPv4aaS
Technologies
3.3. IPv4 Address Sharing
3.4. IPv4 Pool Size Considerations
3.5. CE Provisioning Considerations
3.6. Support for Multicast
4. Detailed Analysis
4.1. Architectural Differences
4.1.1. Basic Comparison
4.2. Trade-Off between Port Number Efficiency and Stateless
Operation
4.3. Support for Public Server Operation
4.4. Support and Implementations
4.4.1. Vendor Support
4.4.2. Support in Cellular and Broadband Networks
4.4.3. Implementation Code Sizes
4.5. Typical Deployment and Traffic Volume Considerations
4.5.1. Deployment Possibilities
4.5.2. Cellular Networks with 464XLAT
4.5.3. Wireline Networks with 464XLAT
4.6. Load Sharing
4.7. Logging
4.8. Optimization for IPv4-Only Devices and Applications
5. Performance Comparison
6. IANA Considerations
7. Security Considerations
8. References
8.1. Normative References
8.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
As the deployment of IPv6 continues to be prevalent, it becomes
clearer that network operators will move to building single-stack
IPv6 core and access networks to simplify network planning and
operations. However, providing customers with IPv4 services
continues to be a requirement for the foreseeable future. To meet
this need, the IETF has standardized a number of different IPv4aaS
technologies for this (see [LEN2019]) based on differing requirements
and deployment scenarios.
The number of technologies that have been developed makes it time-
consuming for a network operator to identify the most appropriate
mechanism for their specific deployment. This document provides a
comparative analysis of the most commonly used mechanisms to assist
operators with this problem.
Five different IPv4aaS solutions are considered:
1. 464XLAT [RFC6877]
2. Dual-Stack Lite [RFC6333]
3. Lightweight 4over6 (lw4o6) [RFC7596]
4. Mapping of Address and Port with Encapsulation (MAP-E) [RFC7597]
5. Mapping of Address and Port using Translation (MAP-T) [RFC7599]
We note that [RFC6180] gives guidelines for using IPv6 transition
mechanisms during IPv6 deployment; that document addresses a much
broader topic, whereas this document focuses on a small part of it.
2. Overview of the Technologies
The following sections introduce the different technologies analyzed
in this document and describe some of their most important
characteristics.
2.1. 464XLAT
464XLAT may use double translation (stateless NAT46 + stateful NAT64)
or single translation (stateful NAT64) depending on different
factors, such as the use of DNS by the applications and the
availability of a DNS64 function (in the host or service provider
network).
The customer-side translator (CLAT) is located in the customer's
device, and it performs stateless NAT46 translation [RFC7915] (more
precisely, a stateless IP/ICMP translation from IPv4 to IPv6).
IPv4-embedded IPv6 addresses [RFC6052] are used for both source and
destination addresses. Commonly, a /96 prefix (either the
64:ff9b::/96 Well-Known Prefix (WKP) or a Network-Specific Prefix) is
used as the IPv6 destination for the IPv4-embedded client traffic.
In deployments where NAT64 load balancing (see Section 4.2 of
[RFC7269]) is enabled, multiple WKPs [RFC8215] may be used.
In the operator's network, the provider-side translator (PLAT)
performs stateful NAT64 [RFC6146] to translate the traffic. The
destination IPv4 address is extracted from the IPv4-embedded IPv6
packet destination address, and the source address is from a pool of
public IPv4 addresses.
Alternatively, when a dedicated /64 is not available for translation,
the CLAT device uses a stateful NAT44 translation before the
stateless NAT46 translation.
In general, keeping state in devices close to the end-user network
(i.e., at the CE (Customer Edge) router) is not perceived to be as
problematic as keeping state in the operator's network.
In typical deployments, 464XLAT is used together with DNS64
[RFC6147]; see Section 3.1.2 of [RFC8683]. When an IPv6-only client
or application communicates with an IPv4-only server, the DNS64
server returns the IPv4-embedded IPv6 address of the IPv4-only
server. In this case, the IPv6-only client sends out IPv6 packets,
the CLAT functions as an IPv6 router, and the PLAT performs a
stateful NAT64 for these packets. There is a single translation.
Similarly, when an IPv4-only client or application communicates with
an IPv4-only server, the CLAT will statelessly translate to IPv6 so
it can traverse the ISP network up to the PLAT (NAT64), which in turn
will translate to IPv4.
Alternatively, one can say that DNS64 + stateful NAT64 is used to
carry the traffic of the IPv6-only client and the IPv4-only server,
and the CLAT is used only for the IPv4 traffic from applications or
devices that use literal IPv4 addresses or non-IPv6-compliant APIs.
Private +----------+ Translated +----------+ _______
+------+ IPv4 | CLAT | 4-6-4 | PLAT | ( IPv4 )
| IPv4 |------->| Stateless|------------>| Stateful +--( Internet )
|Device|<-------| NAT46 |<------------| NAT64 | (________)
+------+ +----------+ ^ +----------+
|
Operator IPv6
Network
Figure 1: Overview of the 464XLAT Architecture
Note: In mobile networks, the CLAT is commonly implemented in the
user equipment (UE) or smartphone; please refer to Figure 2 in
[RFC6877].
Some NAT64 vendors support direct communication (that is, without
translation) between two CLATs by means of hairpinning through the
NAT64.
2.2. Dual-Stack Lite
Dual-Stack Lite (DS-Lite) [RFC6333] was the first of the considered
transition mechanisms to be developed. DS-Lite uses a Basic Bridging
BroadBand (B4) function in the customer's CE router that encapsulates
IPv4 in IPv6 traffic and sends it over the IPv6 native service
provider network to an Address Family Transition Router (AFTR). The
AFTR performs encapsulation/decapsulation of the 4in6 [RFC2473]
traffic and translates the IPv4 source address in the inner IPv4
packet to a public IPv4 source address using a stateful NAPT44
[RFC2663] function.
+-------------+
Private +----------+ IPv4-in-IPv6|Stateful AFTR|
+------+ IPv4 | B4 | Tunnel |------+------+ _______
| IPv4 |------->| Encap./ |------------>|Encap.| | ( IPv4 )
|Device|<-------| Decap. |<------------| / | NAPT +--( Internet )
+------+ +----------+ ^ |Decap.| 44 | (________)
| +------+------+
Operator IPv6
Network
Figure 2: Overview of the DS-Lite Architecture
Some AFTR vendors support direct communication between two B4s by
means of hairpinning through the AFTR.
2.3. Lightweight 4over6
Lightweight 4over6 (lw4o6) is a variant of DS-Lite. The main
difference is that the stateful NAPT44 function is relocated from the
centralized AFTR to the customer's B4 element (called an "lwB4").
The AFTR (called an "lwAFTR") function therefore only performs A+P
(Address plus Port) routing [RFC6346] and 4in6 encapsulation/
decapsulation.
Routing to the correct client and IPv4 address sharing are achieved
using the A+P model [RFC6346] of provisioning each lwB4 with a unique
tuple of IPv4 address and a unique range of transport-layer ports.
The client uses these for NAPT44.
The lwAFTR implements a binding table, which has a per-client entry
linking the customer's source IPv4 address and an allocated range of
transport-layer ports to their IPv6 tunnel endpoint address. The
binding table allows egress traffic from customers to be validated
(to prevent spoofing) and ingress traffic to be correctly
encapsulated and forwarded. As there needs to be a per-client entry,
an lwAFTR implementation needs to be optimized for performing a per-
packet lookup on the binding table.
Direct communication (that is, without translation) between two lwB4s
is performed by hairpinning traffic through the lwAFTR.
+-------------+ +----------+
Private | lwB4 | IPv4-in-IPv6| Stateless|
+------+ IPv4 |------+------| Tunnel | lwAFTR | _______
| IPv4 |------->| |Encap.|------------>|(encap/A+P| ( IPv4 )
|Device|<-------| NAPT | / |<------------|bind. tab +--( Internet )
+------+ | 44 |Decap.| ^ | routing) | (________)
+------+------+ | +----------+
Operator IPv6
Network
Figure 3: Overview of the lw4o6 Architecture
2.4. MAP-E
Like 464XLAT (Section 2.1), MAP-E and MAP-T use IPv4-embedded IPv6
addresses [RFC6052] to represent IPv4 hosts outside the MAP domain.
MAP-E and MAP-T use a stateless algorithm to embed portions of the
customer's allocated IPv4 address (or part of an address with A+P
routing) into the IPv6 prefix delegated to the client. This allows
for large numbers of clients to be provisioned using a single MAP
rule (called a "MAP domain"). The algorithm also allows direct IPv4
peer-to-peer communication between hosts provisioned with common MAP
rules.
The CE router typically performs stateful NAPT44 [RFC2663] to
translate the private IPv4 source addresses and source ports into an
address and port range defined by applying the MAP rule to the
delegated IPv6 prefix. The client address/port allocation size is a
configuration parameter. The CE router then encapsulates the IPv4
packet in an IPv6 packet [RFC2473] and sends it directly to another
host in the MAP domain (for peer-to-peer) or to a Border Router (BR)
if the IPv4 destination is not covered in one of the CE's MAP rules.
The MAP BR is provisioned with the set of MAP rules for the MAP
domains it serves. These rules determine how the MAP BR is to
decapsulate traffic that it receives from the client, validate the
source IPv4 address and transport-layer ports assigned, and calculate
the destination IPv6 address for ingress IPv4 traffic.
+-------------+ +----------+
Private | MAP CE | IPv4-in-IPv6| Stateless|
+------+ IPv4 |------+------| tunnel | MAP BR | _______
| IPv4 |------->| |Encap.|------------>|(encap/A+P| ( IPv4 )
|Device|<-------| NAPT | / |<------------|algorithm +--( Internet )
+------+ | 44 |Decap.| ^ | routing) | (________)
+------+------+ | +----------+
Operator IPv6
Network
Figure 4: Overview of the MAP-E Architecture
Some BR vendors support direct communication between two MAP CEs by
means of hairpinning through the BR.
2.5. MAP-T
MAP-T uses the same mapping algorithm as MAP-E. The major difference
is that double stateless translation (NAT46 in the CE and NAT64 in
the BR) is used to traverse the ISP's IPv6 single-stack network.
MAP-T can also be compared to 464XLAT when there is a double
translation.
A MAP CE router typically performs stateful NAPT44 to translate
traffic to a public IPv4 address and port range calculated by
applying the provisioned Basic MAP Rule (BMR), which is a set of
inputs to the algorithm, to the delegated IPv6 prefix. The CE then
performs stateless translation from IPv4 to IPv6 [RFC7915]. The MAP
BR is provisioned with the same BMR as the client, enabling the
received IPv6 traffic to be translated (using stateless NAT64) back
to the public IPv4 source address used by the client.
Using translation instead of encapsulation also allows IPv4-only
nodes to correspond directly with IPv6 nodes in the MAP-T domain that
have IPv4-embedded IPv6 addresses.
+-------------+ +----------+
Private | MAP CE | Translated | Stateless|
+------+ IPv4 |------+------| 4-6-4 | MAP BR | _______
| IPv4 |------->| |State-|------------>|(NAT64/A+P| ( IPv4 )
|Device|<-------| NAPT | less |<------------|algorithm +--( Internet )
+------+ | 44 |NAT46 | ^ | routing) | (________)
+------+------+ | +----------+
Operator IPv6
Network
Figure 5: Overview of the MAP-T Architecture
Some BR vendors support direct communication between two MAP CEs by
means of hairpinning through the BR.
3. High-Level Architectures and Their Consequences
3.1. Service Provider Network Traversal
For the data plane, there are two approaches for traversing the IPv6
provider network:
* 4-6-4 translation
* 4in6 encapsulation
+====================+=========+=========+=======+=======+=======+
| | 464XLAT | DS-Lite | lw4o6 | MAP-E | MAP-T |
+====================+=========+=========+=======+=======+=======+
| 4-6-4 translation | X | | | | X |
+--------------------+---------+---------+-------+-------+-------+
| 4in6 encapsulation | | X | X | X | |
+--------------------+---------+---------+-------+-------+-------+
Table 1: Available Traversal Mechanisms
In the scope of this document, all of the encapsulation-based
mechanisms use IP-in-IP tunneling [RFC2473]. This is a stateless
tunneling mechanism that does not require any additional overhead.
It should be noted that both of these approaches result in an
increase in the size of the packet that needs to be transported
across the operator's network when compared to native IPv4. 4-6-4
translation adds a 20-byte overhead (the 20-byte IPv4 header is
replaced with a 40-byte IPv6 header). Encapsulation has a 40-byte
overhead (an IPv6 header is prepended to the IPv4 header).
The increase in packet size can become a significant problem if there
is a link with a smaller MTU in the traffic path. This may result in
the need for traffic to be fragmented at the ingress point to the
IPv6 only domain (i.e., the NAT46 or 4in6 encapsulation endpoint).
It may also result in the need to implement buffering and fragment
reassembly in the PLAT/AFTR/lwAFTR/BR node.
The advice given in Section 8.3.1 of [RFC7597] is applicable to all
of these mechanisms: It is strongly recommended that the MTU in the
IPv6-only domain be well managed (it should have sufficiently large
MTU to support tunneling and/or translation) and that the IPv6 MTU on
the CE WAN-side interface be set so that no fragmentation occurs
within the boundary of the IPv6-only domain.
3.2. Network Address Translation among the Different IPv4aaS
Technologies
For the high-level solution of IPv6 service provider network
traversal, MAP-T uses double stateless translation. The first
translation is from IPv4 to IPv6 (NAT46) at the CE, and the second
translation is from IPv6 to IPv4 (NAT64) at the service provider
network.
464XLAT may use double translation (stateless NAT46 + stateful NAT64)
or single translation (stateful NAT64) depending on different
factors, such as the use of DNS by the applications and the
availability of a DNS64 function (in the host or in the service
provider network). For deployment guidelines, please refer to
[RFC8683].
The first step for the double translation mechanisms is a stateless
NAT from IPv4 to IPv6 implemented as SIIT (Stateless IP/ICMP
Translation Algorithm) [RFC7915], which does not translate IPv4
header options and/or multicast IP/ICMP packets. With encapsulation-
based technologies, the header is transported intact, and multicast
can also be carried.
Single and double translation results in native IPv6 traffic with a
transport-layer next header. The fields in these headers can be used
for functions such as hashing across equal-cost multipaths or Access
Control List (ACL) filtering. Encapsulation technologies, in
contrast, may hinder hashing algorithms or other functions relying on
header inspection.
Solutions using double translation can only carry port-aware IP
protocols (e.g., TCP and UDP) and ICMP when they are used with IPv4
address sharing (please refer to Section 4.3 for more details).
Encapsulation-based solutions can also carry any other protocols over
IP.
An in-depth analysis of stateful NAT64 can be found in [RFC6889].
As stateful NAT interferes with the port numbers, [NAT-SUPP] explains
how NATs can handle SCTP (Stream Control Transmission Protocol).
3.3. IPv4 Address Sharing
As public IPv4 address exhaustion is a common motivation for
deploying IPv6, transition technologies need to provide a solution
that allows public IPv4 address sharing.
In order to fulfill this requirement, a stateful NAPT function is a
necessary function in all of the mechanisms. The major
differentiator is where in the architecture this function is located.
The solutions compared by this document fall into two categories:
* Approaches based on Carrier-Grade NAT (CGN) (DS-Lite, 464XLAT)
* Approaches based on A+P (lw4o6, MAP-E, MAP-T)
In the CGN-based model, a device such as a CGN/AFTR or NAT64 performs
the NAPT44 function and maintains per-session state for all of the
active client's traffic. The customer's device does not require per-
session state for NAPT.
In the A+P-based model, a device (usually a CE) performs stateful
NAPT44 and maintains per-session state only for co-located devices,
e.g., in the customer's home network. Here, the centralized network
function (lwAFTR or BR) only needs to perform stateless
encapsulation/decapsulation or NAT64.
Issues related to IPv4 address-sharing mechanisms are described in
[RFC6269] and should also be considered.
The address-sharing efficiency of the five technologies is
significantly different and is discussed in Section 4.2.
Lw4o6, MAP-E, and MAP-T can also be configured without IPv4 address
sharing; see the details in Section 4.3. However, in that case,
there is no advantage in terms of public IPv4 address saving. In the
case of 464XLAT, one-to-one mapping can also be achieved through EAMT
(Explicit Address Mapping Table) [RFC7757].
Conversely, both MAP-E and MAP-T may be configured to provide more
than one public IPv4 address (i.e., an address with an IPv4 prefix
shorter than a /32) to customers.
Dynamic DNS issues in address-sharing contexts and their possible
solutions using PCP (Port Control Protocol) are discussed in detail
in [RFC7393].
3.4. IPv4 Pool Size Considerations
In this section, we do some simple calculations regarding port
numbers. However, technical limitations are not the only point to
consider for port sharing; there are also local regulations and best
current practices.
Note: By "port numbers", we mean TCP/UDP port numbers or ICMP
identifiers.
In most networks, it is possible to use existing data about flows to
Content Delivery Networks (CDNs), caches, or other well-known
IPv6-enabled destinations to calculate the percentage of traffic that
would turn into IPv6 if IPv6 is enabled on that network or on part of
it.
Knowing that, it is possible to calculate the IPv4 pool size required
for a given number of subscribers, depending on the IPv4aaS
technology being used.
According to [MIY2010], each user device (computer, tablet,
smartphone) behind a NAT could simultaneously use up to 300 ports.
(Table 1 of [MIY2010] lists the port number usage of various
applications. According to [REP2014], the downloading of some web
pages may consume up to 200 port numbers.) If the extended NAPT
algorithm is used, which includes the full 5-tuple into the
connection tracking table, then the port numbers are reused when the
destinations are different. Therefore, we need to consider the
number of "port-hungry" applications that are accessing the same
destination simultaneously. We estimate that in the case of a
residential subscriber, there will be typically no more than four
port-hungry applications communicating with the same destination
simultaneously, which is a total of 1,200 ports.
For example, if 80% of the traffic is expected towards IPv6
destinations, only 20% will actually be using IPv4 ports. Thus, in
our example, 240 ports are required for each subscriber.
From the 65,535 ports available per IPv4 address, we could even
consider reserving 1,024 ports for customers that need EAMT entries
for incoming connections to System ports (0-1023, also called "well-
known ports") [RFC7605]. This means that 64,511 ports are actually
available for each IPv4 address.
According to this, a /22 (1.024 public IPv4 addresses) will be
sufficient for over 275,000 subscribers
(1,024x64,511/240=275,246.93).
Similarly, a /18 (16,384 public IPv4 addresses) will be sufficient
for over 4,403,940 subscribers, and so on.
This is a conservative approach, which is valid in the case of
464XLAT because ports are assigned dynamically by the NAT64.
Therefore, it is not necessary to consider if one user is actually
using more or fewer ports; average values work well.
As the deployment of IPv6 progresses, the use of NAT64, and therefore
of public IPv4 addresses, decreases (more IPv6 ports, fewer IPv4
ports). Thus, either more subscribers can be accommodated with the
same number of IPv4 addresses or some of those addressed can be
retired from the NAT64.
For comparison, if dual-stack is being used, any given number of
users will require the same number of public IPv4 addresses. For
instance, a /14 will provide 262,144 IPv4 public addresses for
262,144 subscribers, versus 275,000 subscribers being served with
only a /22.
In the other IPv4aaS technologies, this calculation will only match
if the assignment of ports per subscriber can be done dynamically,
which is not always the case (depending on the vendor
implementation).
When dynamic assignment of addresses is not possible, an alternative
approximation for the other IPv4aaS technologies must ensure a
sufficient number of ports per subscriber. That means 1,200 ports,
and typically, it comes to 2,000 ports in many deployments. In that
case, assuming 80% is IPv6 traffic (as above), only 30 subscribers
will be allowed per each IPv4 address; thus, the closer approximation
to 275,000 subscribers per our example with 464XLAT (with a /22) will
be using a /19, which serves 245,760 subscribers (a /19 has 8,192
addresses and 30 subscribers with 2,000 ports each per address).
If the CGN (in case of DS-Lite) or the CE (in case of lw4o6, MAP-E,
and MAP-T) make use of a 5-tuple for tracking the NAT connections,
the number of ports required per subscriber can be limited as low as
four ports per subscriber. However, the practical limit depends on
the desired limit for parallel connections that any single host
behind the NAT can have to the same address and port in Internet.
Note that it is becoming more common that applications use AJAX
(Asynchronous JavaScript and XML) and similar mechanisms, so taking
that extreme limit is probably not a safe choice.
This feature of extremely reduced number of ports could also be used
in case the CLAT-enabled CE with 464XLAT makes use of tracking the
5-tuple NAT connections and could also be further extended if the
NAT64 also uses the 5-tuple.
Please also refer to [RFC6888] for in-depth information about the
requirements for sizing CGN gateways.
3.5. CE Provisioning Considerations
All of the technologies require some provisioning of customer
devices. The table below shows which methods currently have
extensions for provisioning the different mechanisms.
+==============+=========+=========+=========+==========+===========+
|Provisioning | 464XLAT | DS-Lite | lw4o6 | MAP-E | MAP-T |
|Method | | | | | |
+==============+=========+=========+=========+==========+===========+
|DHCPv6 | | X | X | X | X |
|[RFC8415] | | | | | |
+--------------+---------+---------+---------+----------+-----------+
|RADIUS | |[RFC6519]| X | X | X |
|[RFC8658] | | | | | |
+--------------+---------+---------+---------+----------+-----------+
|TR-069 | * | X | * | X | X |
|[TR-069] | | | | | |
+--------------+---------+---------+---------+----------+-----------+
|DNS64 | X | | | | |
|[RFC7050] | | | | | |
+--------------+---------+---------+---------+----------+-----------+
|YANG [RFC7950]|[RFC8512]|[RFC8513]|[RFC8676]|[RFC8676] | [RFC8676] |
+--------------+---------+---------+---------+----------+-----------+
|DHCP 4o6 | | | X | X | |
|[RFC7341] | | | | | |
+--------------+---------+---------+---------+----------+-----------+
Table 2: Available Provisioning Mechanisms
*: Work started at Broadband Forum (2021)
X: Supported by the provisioning method
3.6. Support for Multicast
The solutions covered in this document are all intended for unicast
traffic. [RFC8114] describes a method for carrying encapsulated IPv4
multicast traffic over an IPv6 multicast network. This could be
deployed in parallel to any of the operator's chosen IPv4aaS
mechanism.
4. Detailed Analysis
4.1. Architectural Differences
4.1.1. Basic Comparison
The five IPv4aaS technologies can be classified based on two aspects:
* Technology used for service provider network traversal. It can be
single/double translation or encapsulation.
* Presence or absence of per-flow state in the operator network.
+====================+=========+=========+=======+=======+=======+
| | 464XLAT | DS-Lite | lw4o6 | MAP-E | MAP-T |
+====================+=========+=========+=======+=======+=======+
| Translation (T) or | T | E | E | E | T |
| Encapsulation (E) | | | | | |
+--------------------+---------+---------+-------+-------+-------+
| Presence (+) of | + | + | | | |
| Per-Flow State in | | | | | |
| Operator Network | | | | | |
+--------------------+---------+---------+-------+-------+-------+
Table 3: Basic Comparison among the Analyzed Technologies
4.2. Trade-Off between Port Number Efficiency and Stateless Operation
464XLAT and DS-Lite use stateful NAPT at the PLAT and AFTR devices,
respectively. This may cause scalability issues for the number of
clients or volume of traffic, but it does not impose a limitation on
the number of ports per user, as they can be allocated dynamically
on-demand and the allocation policy can be centrally managed and
adjusted.
A+P-based mechanisms (lw4o6, MAP-E, and MAP-T) avoid using NAPT in
the service provider network. However, this means that the number of
ports provided to each user (and hence the effective IPv4 address-
sharing ratio) must be pre-provisioned to the client.
Changing the allocated port ranges with A+P-based technologies
requires more planning and is likely to involve reprovisioning both
hosts and operator-side equipment. It should be noted that due to
the per-customer binding table entry used by lw4o6, a single customer
can be reprovisioned (e.g., if they request a full IPv4 address)
without needing to change parameters for a number of customers as in
a MAP domain.
It is also worth noting that there is a direct relationship between
the efficiency of public port allocations for customers and the
corresponding logging overhead that may be necessary to meet data-
retention requirements. This is considered in Section 4.7.
Determining the optimal number of ports for a fixed port set is not
an easy task and may also be impacted by local regulatory law (and in
the Belgian case, it is not a law but more a memorandum of
understanding or best current practice), which may define a maximum
number of users per IP address and consequently a minimum number of
ports per user.
On the one hand, the "lack of ports" situation may cause serious
problems in the operation of certain applications. For example,
Miyakawa has demonstrated the consequences of the session number
limitation due to port number shortage in the example of Google Maps
[MIY2010]. When the limit was 15, several blocks of the map were
missing, and the map was unusable. This study also provided several
examples for the session numbers of different applications (the
highest one was Apple's iTunes at 230-270 ports).
The port number consumption of different applications is highly
varying. In the case of web browsing, it depends on several factors,
including the choice of the web page, the web browser, and sometimes
the operating system [REP2014]. For example, under certain
conditions, 120-160 ports were used (URL: sohu.com, browser: Firefox
under Ubuntu Linux), and in some other cases, only 3-12 ports were
used (URL: twitter.com, browser: Iceweasel under Debian Linux).
There may be several users behind a CE router, especially in the
broadband case (e.g., Internet is used by different members of a
family simultaneously), so sufficient ports must be allocated to
avoid impacting user experience.
In general, assigning too few source port numbers to an end user may
result in unexpected and hard-to-debug consequences; therefore, if
the number of ports per end user is fixed, then we recommend
assigning a conservatively large number of ports. For example, the
developers of Jool used 2048 ports per user in their example for
MAP-T [JOOL-MAPT].
However, assigning too many ports per CE router will result in waste
of public IPv4 addresses, which are scarce and expensive resources.
Clearly, this is a big advantage in the case of 464XLAT where they
are dynamically managed so that the number of IPv4 addresses for the
sharing pool is smaller while the availability of ports per user
doesn't need to be pre-defined and is not a limitation.
There is a direct trade-off between the optimization of client port
allocations and the associated logging overhead. Section 4.7
discusses this in more depth.
We note that common NAT44 implementations utilizing Netfilter at the
CE router multiplex active sessions using a 3-tuple (source address,
destination address, and destination port). This means that external
source ports can be reused for unique internal source and destination
addresses and port sessions. It is also noted that Netfilter cannot
currently make use of multiple source port ranges (i.e., several
blocks of ports distributed across the total port space as is common
in MAP deployments). This may influence the design when using
stateless technologies.
Stateful technologies, 464XLAT, DS-Lite, and NAT444 can therefore be
much more efficient in terms of port allocation and thus public IP
address saving. The price is the stateful operation in the service
provider network, which allegedly does not scale up well. It should
be noted that, in many cases, all those factors may depend on how it
is actually implemented.
Measurements have been started to examine the scalability of a few
stateful solutions in two areas:
* How their performance scales up with the number of CPU cores
* To what extent their performance degrades with the number of
concurrent connections
The details of the measurements and their results are available from
[IPv4aaS-SCALE-TECH].
We note that some CGN-type solutions can allocate ports dynamically
"on the fly". Depending on configuration, this can result in the
same customer being allocated ports from different source addresses.
This can cause operational issues for protocols and applications that
expect multiple flows to be sourced from the same address (e.g., ECMP
hashing, STUN, gaming, and content delivery networks). However, it
should be noted that this is the same problem when a network has a
NAT44 with multiple public IPv4 addresses, or even when applications
in a dual-stack case, behave wrongly if Happy Eyeballs is flapping
the flow address between IPv4 and IPv6.
The consequences of IPv4 address sharing [RFC6269] may impact all
five technologies. However, when ports are allocated statically,
more customers may get ports from the same public IPv4 address, which
may result in negative consequences with higher probability. For
example, many applications and service providers (Sony PlayStation
Network, OpenDNS, etc.) can permanently block IPv4 ranges if they
detect that they are used for address sharing.
Both cases are, again, implementation-dependent.
We note that although it is not of typical use, one can do
deterministic, stateful NAT and reserve a fixed set of ports for each
customer as well.
4.3. Support for Public Server Operation
Mechanisms that rely on operator-side per-flow state do not, by
themselves, offer a way for customers to present services on publicly
accessible transport-layer ports.
The Port Control Protocol (PCP) [RFC6887] provides a mechanism for a
client to request an external public port from a CGN device. For
server operation, it is required with 464XLAT/NAT64, and it is
supported in some DS-Lite AFTR implementations.
A+P-based mechanisms distribute a public IPv4 address and restricted
range of transport-layer ports to the client. In this case, it is
possible for the user to configure their device to offer a publicly
accessible server on one of their allocated ports. It should be
noted that operators commonly do not assign the well-known ports to
users (unless they are allocating a full IPv4 address), so the user
will need to run the service on an allocated port or configure port
translation.
Lw4o6, MAP-E, and MAP-T may be configured to allocated clients with a
full IPv4 address, allowing exclusive use of all ports and non-port-
based transport-layer protocols. Thus, they may also be used to
support server/services operation on their default ports. However,
when public IPv4 addresses are assigned to the CE router without
address sharing, there is obviously no advantage in terms of IPv4
public addresses saving.
It is also possible to configure specific ports mapping in 464XLAT/
NAT64 using EAMT [RFC7757], which means that only those ports are
"lost" from the pool of addresses, so there is a higher maximization
of the total usage of IPv4 port resources.
4.4. Support and Implementations
4.4.1. Vendor Support
In general, router vendors support AFTR, MAP-E BR, MAP-T BR, and
NAT64. Vendors of load balancers and firewalls usually support NAT64
as well while not all of them have support for the other protocols.
A 464XLAT client (CLAT) is implemented in Windows 10, Linux
(including Android), Windows Mobile, Chrome OS, and iOS, but it is
not available in macOS 12.3.1.
The remaining four solutions are commonly deployed as functions in
the CE device only; however, the vendors' support is poor in general
(except for DS-Lite).
OpenWRT is a Linux-based open-source OS designed for CE devices. It
offers a number of different 'opkg' packages as part of the
distribution:
* '464xlat' enables support for 464XLAT CLAT functionality.
* 'ds-lite' enables support for DSLite B4 functionality.
* 'map' enables support for MAP-E and lw4o6 CE functionality.
* 'map-t' enables support for MAP-T CE functionality.
At the time of publication, some free open-source implementations
exist for the operator-side functionality:
* Jool [JOOL] (CLAT, NAT64, EAMT, MAP-T CE, MAP-T BR)
* VPP/fd.io [VPP] (MAP-BR, lwAFTR, CGN, CLAT, NAT64)
* Snabb [SNABB] (lwAFTR)
* AFTR [AFTR] (DSLite AFTR)
4.4.2. Support in Cellular and Broadband Networks
Several cellular networks use 464XLAT, whereas there are no
deployments of the four other technologies in cellular networks, as
they are neither standardized nor implemented in UE devices.
In broadband networks, there are some deployments of 464XLAT, MAP-E,
and MAP-T. Lw4o6 and DS-Lite have more deployments, with DS-Lite
being the most common, but deployments of lw4o6 have been rapidly
increasing in the last few years.
Please refer to Tables 2 and 3 of [LEN2019] for a limited set of
deployment information.
4.4.3. Implementation Code Sizes
As a hint to the relative complexity of the mechanisms, the code
sizes reported from the OpenWRT implementations of each technology
are 17 kB, 35 kB, 15 kB, 35 kB, and 48 kB for 464XLAT, lw4o6, DS-
Lite, MAP-E, and MAP-T, respectively (see
<https://openwrt.org/packages/start>).
We note that the support for all five technologies requires a much
smaller code size than the total sum of the above quantities, because
they contain a lot of common functions (e.g., data plane is shared
among several of them).
4.5. Typical Deployment and Traffic Volume Considerations
4.5.1. Deployment Possibilities
Theoretically, all five IPv4aaS technologies could be used together
with DNS64 + stateful NAT64, as is done in 464XLAT. In this case,
the CE router would treat the traffic between an IPv6-only client and
IPv4-only server as normal IPv6 traffic, and the stateful NAT64
gateway would do a single translation, thus offloading this kind of
traffic from the IPv4aaS technology. The cost of this solution would
be the need to also deploy DNS64 + stateful NAT64.
However, this has not been implemented in clients or actual
deployments, so only 464XLAT always uses this optimization, and the
other four solutions do not use it at all.
4.5.2. Cellular Networks with 464XLAT
Figures from existing deployments (through the end of 2018) show the
typical traffic volumes in an IPv6-only cellular network when 464XLAT
technology is used together with DNS64:
* 75% of traffic is IPv6 end-to-end (no translation).
* 24% of traffic uses DNS64 + NAT64 (one translation).
* Less than 1% of traffic uses the CLAT in addition to NAT64 (two
translations), due to an IPv4 socket and/or IPv4 literal.
Without using DNS64, 25% of the traffic would undergo double
translation.
4.5.3. Wireline Networks with 464XLAT
Figures from several existing deployments (through the end of 2020),
mainly with residential customers, show the ranges of typical traffic
volumes in an IPv6-only network, when 464XLAT is used with DNS64:
* 65%-85% of traffic is IPv6 end-to-end (no translation).
* 14%-34% of traffic uses DNS64 + NAT64 (one translation).
* Less than 1-2% of traffic uses the CLAT in addition to NAT64 (two
translations), due to an IPv4 socket and/or IPv4 literal.
Without using DNS64, 16%-35% of the traffic would undergo double
translation.
This data is consistent with non-public information of actual
deployments, which can be easily explained. When a wireline ISP has
mainly residential customers, content providers and CDNs that are
already IPv6 enabled (Google/YouTube, Netflix, Facebook, Akamai,
etc.) typically account for 65-85% of the traffic in the network.
Thus, when the subscribers are IPv6 enabled, about the same
percentage of traffic will become IPv6.
4.6. Load Sharing
If multiple network-side devices are needed as PLAT/AFTR/BR for
capacity, then there is a need for a load-sharing mechanism. ECMP
(Equal-Cost Multipath) load sharing can be used for all technologies;
however, stateful technologies will be impacted by changes in network
topology or device failure.
Technologies utilizing DNS64 can also distribute load across PLAT/
AFTR devices, evenly or unevenly, by using different prefixes.
Different network-specific prefixes can be distributed for
subscribers in appropriately sized segments (like split-horizon DNS,
also called "DNS views").
Stateless technologies, due to the lack of per-flow state, can make
use of anycast routing for load sharing and resiliency across network
devices, both ingress and egress; flows can take asymmetric paths
through the network, i.e., in through one lwAFTR/BR and out via
another.
Mechanisms with centralized NAPT44 state have a number of challenges
specifically related to scaling and resilience. As the total amount
of client traffic exceeds the capacity of a single CGN instance,
additional nodes are required to handle the load. Each CGN maintains
a stateful table of active client sessions, and this table may need
to be synchronized between CGN instances. This is necessary for two
reasons:
* To prevent all active customer sessions from being dropped in the
event of a CGN node failure.
* To ensure a matching state table entry for an active session in
the event of asymmetric routing through different egress and
ingress CGN nodes.
4.7. Logging
In the case of 464XLAT and DS-Lite, the user of any given public IPv4
address and port combination will vary over time; therefore, logging
is necessary to meet data-retention laws. Each entry in the PLAT/
AFTR generates a logging entry. As discussed in Section 4.2, a
client may open hundreds of sessions during common tasks such as web
browsing, each of which needs to be logged so the overall logging
burden on the network operator is significant. In some countries,
this level of logging is required to comply with data-retention
legislation.
One common optimization available to reduce the logging overhead is
the allocation of a block of ports to a client for the duration of
their session. This means that a logging entry only needs to be made
when the client's port block is released, which dramatically reduces
the logging overhead. This comes as the cost of less efficient
public address sharing as clients need to be allocated a port block
of a fixed size regardless of the actual number of ports that they
are using.
Stateless technologies that pre-allocate the IPv4 addresses and ports
only require that copies of the active MAP rules (for MAP-E and MAP-
T) or binding table (for lw4o6) are retained along with timestamp
information of when they have been active. Support tools (e.g.,
those used to serve data-retention requests) may need to be updated
to be aware of the mechanism in use (e.g., implementing the MAP
algorithm so that IPv4 information can be linked to the IPv6 prefix
delegated to a client). Stateless technologies do not have a
centralized stateful element that customer traffic needs to pass
through, so if data-retention laws mandate per-session logging, there
is no simple way of meeting this requirement with a stateless
technology alone. Thus, a centralized NAPT44 model may be the only
way to meet this requirement.
Deterministic CGN [RFC7422] was proposed as a solution to reduce the
resource consumption of logging.
Please also refer to Section 4 of [RFC6888] for more information
about requirements for logging CGN gateways.
4.8. Optimization for IPv4-Only Devices and Applications
When IPv4-only devices or applications are behind a CE connected with
IPv6-only and IPv4aaS, the IPv4-only traffic flows will necessarily
be encapsulated/decapsulated (in the case of DS-Lite, lw4o6, and MAP-
E) and will reach the IPv4 address of the destination, even if that
service supports dual-stack. This means that the traffic flow will
cross through the AFTR, lwAFTR, or BR, depending on the specific
transition mechanism being used.
Even if those services are directly connected to the operator network
(e.g., CDNs and caches) or located internally (such as VoIP, etc.),
it is not possible to avoid that overhead.
However, in the case of those mechanisms that use a NAT46 function,
in the CE (464XLAT and MAP-T), it is possible to take advantage of
optimization functionalities, such as the ones described in
[OP-464XLAT/MAP-T].
Because the NAT46 has already translated the IPv4-only flow to IPv6
and the services are dual-stack, using these optimizations allows the
services to be reached without the need to translate the flow back to
IPv4.
5. Performance Comparison
We plan to compare the performances of the most prominent free
software implementations of the five IPv6 transition technologies
using the methodology described in "Benchmarking Methodology for IPv6
Transition Technologies" [RFC8219].
The dual Device Under Test (DUT) setup of [RFC8219] makes it possible
to use the existing measurement devices compliant with "Benchmarking
Methodology for Network Interconnect Devices" [RFC2544]; however,
this solution has two kinds of limitations:
* Dual DUT setup has the drawback that the performances of the CE
and the ISP-side device (e.g., the CLAT and PLAT of 464XLAT) are
measured together. In order to measure the performance of only
one of them, we need to ensure that the desired one is the
bottleneck.
* Measurement procedures for Packet Delay Variation (PDV) and Inter-
Packet Delay Variation (IPDV) measurements are missing from the
legacy devices, and the old measurement procedure for latency has
been redefined in [RFC8219].
The single DUT setup of [RFC8219] makes it possible to benchmark the
selected device separately, but either special Tester is required or
some trick is needed if we want to use legacy Testers. An example
for the latter is our stateless NAT64 measurements testing Throughput
and Frame Loss Rate using a legacy commercial Tester [LEN2020a] that
is compliant with [RFC5180].
Siitperf, a DPDK-based software Tester that is compliant with
[RFC8219] and used for benchmarking stateless NAT64 gateways, has
been developed recently. Siitperf is available from GitHub
[SIITPERF] as free software and is documented in [LEN2021].
Originally, it literally followed the test frame format of [RFC2544],
including "hard-wired" source and destination port numbers, and then
it was complemented with the pseudorandom port feature required by
[RFC4814]. The new version is documented in [LEN2020b].
Further DPDK-based software Testers that are compliant with [RFC8219]
are being developed at the Budapest University of Technology and
Economics as student projects. They are planned to be released as
free software, too.
Information about the benchmarking tools, measurements, and results
will be made available in [IPv4aaS-BENCHMARK-TECH].
6. IANA Considerations
This document has no IANA actions.
7. Security Considerations
As discussed in Section 4.7, the different technologies have varying
logging capabilities and limitations. Care should be taken when
storing, transmitting, and providing access to log entries that may
be considered personally identifiable information. However, it
should be noted that those issues are not specific to the IPv4aaS
IPv6 transition technologies but apply to logging functionalities in
general.
For all five technologies, the CE device typically contains a DNS
proxy. However, the user may change DNS settings. If this happens
and lw4o6, MAP-E, and MAP-T are used with a significantly restricted
port set (which is required for efficient public IPv4 address
sharing), the entropy of the source ports is significantly lowered
(e.g., from 16 bits to 10 bits when 1024 port numbers are assigned to
each subscriber), and these technologies are thus theoretically less
resilient against cache poisoning (see [RFC5452]). However, an
efficient cache poisoning attack requires that the subscriber
operates its own caching DNS server and the attack is performed in
the service provider network. Thus, we consider the chance of the
successful exploitation of this vulnerability to be low.
IPv4aaS technologies based on encapsulation have no DNSSEC
implications. However, those based on translation may have
implications as discussed in Section 4.1 of [RFC8683].
An in-depth security analysis of all five IPv6 transition
technologies and their most prominent free software implementations
according to the methodology defined in [LEN2018] is planned.
As the first step, an initial security analysis of 464XLAT was done
in [AZZ2021].
The implementers of any of the five IPv4aaS solutions should consult
the Security Considerations of the respective RFCs documenting them.
8. References
8.1. Normative References
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544,
DOI 10.17487/RFC2544, March 1999,
<https://www.rfc-editor.org/info/rfc2544>.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, DOI 10.17487/RFC2663, August 1999,
<https://www.rfc-editor.org/info/rfc2663>.
[RFC4814] Newman, D. and T. Player, "Hash and Stuffing: Overlooked
Factors in Network Device Benchmarking", RFC 4814,
DOI 10.17487/RFC4814, March 2007,
<https://www.rfc-editor.org/info/rfc4814>.
[RFC5180] Popoviciu, C., Hamza, A., Van de Velde, G., and D.
Dugatkin, "IPv6 Benchmarking Methodology for Network
Interconnect Devices", RFC 5180, DOI 10.17487/RFC5180, May
2008, <https://www.rfc-editor.org/info/rfc5180>.
[RFC5452] Hubert, A. and R. van Mook, "Measures for Making DNS More
Resilient against Forged Answers", RFC 5452,
DOI 10.17487/RFC5452, January 2009,
<https://www.rfc-editor.org/info/rfc5452>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
DOI 10.17487/RFC6147, April 2011,
<https://www.rfc-editor.org/info/rfc6147>.
[RFC6180] Arkko, J. and F. Baker, "Guidelines for Using IPv6
Transition Mechanisms during IPv6 Deployment", RFC 6180,
DOI 10.17487/RFC6180, May 2011,
<https://www.rfc-editor.org/info/rfc6180>.
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
P. Roberts, "Issues with IP Address Sharing", RFC 6269,
DOI 10.17487/RFC6269, June 2011,
<https://www.rfc-editor.org/info/rfc6269>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<https://www.rfc-editor.org/info/rfc6333>.
[RFC6346] Bush, R., Ed., "The Address plus Port (A+P) Approach to
the IPv4 Address Shortage", RFC 6346,
DOI 10.17487/RFC6346, August 2011,
<https://www.rfc-editor.org/info/rfc6346>.
[RFC6519] Maglione, R. and A. Durand, "RADIUS Extensions for Dual-
Stack Lite", RFC 6519, DOI 10.17487/RFC6519, February
2012, <https://www.rfc-editor.org/info/rfc6519>.
[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>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <https://www.rfc-editor.org/info/rfc6888>.
[RFC6889] Penno, R., Saxena, T., Boucadair, M., and S. Sivakumar,
"Analysis of Stateful 64 Translation", RFC 6889,
DOI 10.17487/RFC6889, April 2013,
<https://www.rfc-editor.org/info/rfc6889>.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis",
RFC 7050, DOI 10.17487/RFC7050, November 2013,
<https://www.rfc-editor.org/info/rfc7050>.
[RFC7269] Chen, G., Cao, Z., Xie, C., and D. Binet, "NAT64
Deployment Options and Experience", RFC 7269,
DOI 10.17487/RFC7269, June 2014,
<https://www.rfc-editor.org/info/rfc7269>.
[RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport",
RFC 7341, DOI 10.17487/RFC7341, August 2014,
<https://www.rfc-editor.org/info/rfc7341>.
[RFC7393] Deng, X., Boucadair, M., Zhao, Q., Huang, J., and C. Zhou,
"Using the Port Control Protocol (PCP) to Update Dynamic
DNS", RFC 7393, DOI 10.17487/RFC7393, November 2014,
<https://www.rfc-editor.org/info/rfc7393>.
[RFC7422] Donley, C., Grundemann, C., Sarawat, V., Sundaresan, K.,
and O. Vautrin, "Deterministic Address Mapping to Reduce
Logging in Carrier-Grade NAT Deployments", RFC 7422,
DOI 10.17487/RFC7422, December 2014,
<https://www.rfc-editor.org/info/rfc7422>.
[RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the Dual-
Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
July 2015, <https://www.rfc-editor.org/info/rfc7596>.
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015,
<https://www.rfc-editor.org/info/rfc7597>.
[RFC7599] Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
and T. Murakami, "Mapping of Address and Port using
Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July
2015, <https://www.rfc-editor.org/info/rfc7599>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/info/rfc7605>.
[RFC7757] Anderson, T. and A. Leiva Popper, "Explicit Address
Mappings for Stateless IP/ICMP Translation", RFC 7757,
DOI 10.17487/RFC7757, February 2016,
<https://www.rfc-editor.org/info/rfc7757>.
[RFC7915] Bao, C., Li, X., Baker, F., Anderson, T., and F. Gont,
"IP/ICMP Translation Algorithm", RFC 7915,
DOI 10.17487/RFC7915, June 2016,
<https://www.rfc-editor.org/info/rfc7915>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>.
[RFC8215] Anderson, T., "Local-Use IPv4/IPv6 Translation Prefix",
RFC 8215, DOI 10.17487/RFC8215, August 2017,
<https://www.rfc-editor.org/info/rfc8215>.
[RFC8219] Georgescu, M., Pislaru, L., and G. Lencse, "Benchmarking
Methodology for IPv6 Transition Technologies", RFC 8219,
DOI 10.17487/RFC8219, August 2017,
<https://www.rfc-editor.org/info/rfc8219>.
[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>.
[RFC8512] Boucadair, M., Ed., Sivakumar, S., Jacquenet, C.,
Vinapamula, S., and Q. Wu, "A YANG Module for Network
Address Translation (NAT) and Network Prefix Translation
(NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019,
<https://www.rfc-editor.org/info/rfc8512>.
[RFC8513] Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG
Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513,
DOI 10.17487/RFC8513, January 2019,
<https://www.rfc-editor.org/info/rfc8513>.
[RFC8658] Jiang, S., Ed., Fu, Y., Ed., Xie, C., Li, T., and M.
Boucadair, Ed., "RADIUS Attributes for Softwire Mechanisms
Based on Address plus Port (A+P)", RFC 8658,
DOI 10.17487/RFC8658, November 2019,
<https://www.rfc-editor.org/info/rfc8658>.
[RFC8676] Farrer, I., Ed. and M. Boucadair, Ed., "YANG Modules for
IPv4-in-IPv6 Address plus Port (A+P) Softwires", RFC 8676,
DOI 10.17487/RFC8676, November 2019,
<https://www.rfc-editor.org/info/rfc8676>.
[RFC8683] 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>.
8.2. Informative References
[AFTR] ISC, "ISC Implementation of AFTR",
<https://downloads.isc.org/isc/aftr/>.
[AZZ2021] Al-Azzawi, A. and G. Lencse, "Identification of the
Possible Security Issues of the 464XLAT IPv6 Transition
Technology", Infocommunications Journal, Vol. 13, No. 4,
pp. 10-18, DOI 10.36244/ICJ.2021.4.2, December 2021,
<https://www.infocommunications.hu/2021_4_2>.
[IPv4aaS-BENCHMARK-TECH]
Lencse, G., "Performance Analysis of IPv6 Transition
Technologies for IPv4aaS", Work in Progress, Internet-
Draft, draft-lencse-v6ops-transition-benchmarking-01, 2
May 2022, <https://datatracker.ietf.org/doc/html/draft-
lencse-v6ops-transition-benchmarking-01>.
[IPv4aaS-SCALE-TECH]
Lencse, G., "Scalability of IPv6 Transition Technologies
for IPv4aaS", Work in Progress, Internet-Draft, draft-
lencse-v6ops-transition-scalability-03, 30 June 2022,
<https://datatracker.ietf.org/doc/html/draft-lencse-v6ops-
transition-scalability-03>.
[JOOL] "Jool: SIIT & NAT64", <http://www.jool.mx>.
[JOOL-MAPT]
"MAP-T Run", <https://www.jool.mx/en/run-mapt.html>.
[LEN2018] Lencse, G. and Y. Kadobayashi, "Methodology for the
identification of potential security issues of different
IPv6 transition technologies: Threat analysis of DNS64 and
stateful NAT64", Computers & Security, Vol. 77, No. 1, pp.
397-411, DOI 10.1016/j.cose.2018.04.012, August 2018,
<http://www.hit.bme.hu/~lencse/publications/ECS-2018-
Methodology-revised.pdf>.
[LEN2019] Lencse, G. and Y. Kadobayashi, "Comprehensive Survey of
IPv6 Transition Technologies: A Subjective Classification
for Security Analysis", IEICE Transactions on
Communications, Vol. E102-B, No. 10, pp. 2021-2035,
DOI 10.1587/transcom.2018EBR0002, October 2019,
<http://www.hit.bme.hu/~lencse/publications/
e102-b_10_2021.pdf>.
[LEN2020a] Lencse, G., "Benchmarking stateless NAT64 implementations
with a standard tester", Telecommunication Systems, Vol.
75, pp. 245-257, DOI 10.1007/s11235-020-00681-x, June
2020, <https://link.springer.com/article/10.1007/
s11235-020-00681-x>.
[LEN2020b] Lencse, G., "Adding RFC 4814 Random Port Feature to
Siitperf: Design, Implementation and Performance
Estimation", International Journal of Advances in
Telecommunications, Electrotechnics, Signals and Systems,
Vol. 9, No. 3, pp. 18-26, DOI 10.11601/ijates.v9i3.291,
2020,
<https://ijates.org/index.php/ijates/article/view/291>.
[LEN2021] Lencse, G., "Design and Implementation of a Software
Tester for Benchmarking Stateless NAT64 Gateways", IEICE
Transactions on Communications, Vol. E104.B, Issue 2, pp.
128-140, DOI 10.1587/transcom.2019EBN0010, 2021,
<https://doi.org/10.1587/transcom.2019EBN0010>.
[MIY2010] Miyakawa, S., "IPv4 to IPv6 Transformation Schemes", IEICE
Transactions on Communications, Vol. E93-B, Issue 5, pp.
1078-1084, DOI 10.1587/transcom.E93.B.1078, 2010,
<https://www.jstage.jst.go.jp/article/transcom/E93.B/5/
E93.B_5_1078/_article>.
[NAT-SUPP] Stewart, R. R., Tüxen, M., and I. Ruengeler, "Stream
Control Transmission Protocol (SCTP) Network Address
Translation Support", Work in Progress, Internet-Draft,
draft-ietf-tsvwg-natsupp-23, 25 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-
natsupp-23>.
[OP-464XLAT/MAP-T]
Palet Martinez, J. and A. D'Egidio, "464XLAT/MAT-T
Optimization", Work in Progress, Internet-Draft, draft-
ietf-v6ops-464xlat-optimization-03, 28 July 2020,
<https://datatracker.ietf.org/doc/html/draft-ietf-v6ops-
464xlat-optimization-03>.
[REP2014] Répás, S., Hajas, T., and G. Lencse, "Port Number
Consumption of the NAT64 IPv6 Transition Technology", 37th
International Conference on Telecommunications and Signal
Processing, DOI 10.1109/TSP.2015.7296411, 2014,
<http://www.hit.bme.hu/~lencse/publications/TSP-
2014-PC.pdf>.
[SIITPERF] "Siitperf: an RFC 8219 compliant SIIT (stateless NAT64)
tester", commit bdce0f, February 2021,
<https://github.com/lencsegabor/siitperf>.
[SNABB] "Snabb implementation of lwAFTR", commit 1ef72ce, January
2022, <https://github.com/Igalia/snabb>.
[TR-069] Broadband Forum, "CPE WAN Management Protocol", Technical
Report TR-069, June 2020, <https://www.broadband-
forum.org/technical/download/TR-069.pdf>.
[VPP] "VPP", July 2022,
<https://wiki.fd.io/index.php?title=VPP&oldid=11809>.
Acknowledgements
The authors would like to thank Ole Troan, Warren Kumari, Dan
Romascanu, Brian Trammell, Joseph Salowey, Roman Danyliw, Erik Kline,
Lars Eggert, Zaheduzzaman Sarker, Robert Wilton, Éric Vyncke and
Martin Duke for their review of this document and acknowledge the
inputs of Mark Andrews, Edwin Cordeiro, Fred Baker, Alexandre
Petrescu, Cameron Byrne, Tore Anderson, Mikael Abrahamsson, Gert
Doering, Satoru Matsushima, Yutianpeng (Tim), Mohamed Boucadair, Nick
Hilliard, Joel Jaeggli, Kristian McColm, Tom Petch, Yannis
Nikolopoulos, Havard Eidnes, Yann-Ju Chu, Barbara Stark, Vasilenko
Eduard, Chongfeng Xie, Henri Alves de Godoy, Magnus Westerlund,
Michael Tüxen, Philipp S. Tiesel, Brian E. Carpenter, and Joe Touch.
Authors' Addresses
Gábor Lencse
Budapest University of Technology and Economics
Budapest
Magyar tudósok körútja 2
H-1117
Hungary
Email: lencse@hit.bme.hu
URI: http://www.hit.bme.hu/~lencse/index_en.htm
Jordi Palet Martinez
The IPv6 Company
Molino de la Navata, 75
28420 La Navata - Galapagar Madrid
Spain
Email: jordi.palet@theipv6company.com
URI: http://www.theipv6company.com/
Lee Howard
Retevia
9940 Main St., Suite 200
Fairfax, Virginia 22031
United States of America
Email: lee@asgard.org
Richard Patterson
Sky UK
1 Brick Lane
London
EQ 6PU
United Kingdom
Email: richard.patterson@sky.uk
Ian Farrer
Deutsche Telekom AG
Landgrabenweg 151
53227 Bonn
Germany
Email: ian.farrer@telekom.de
