draft-ietf-tsvwg-behave-requirements-update-04.txt   draft-ietf-tsvwg-behave-requirements-update-05.txt 
TSVWG R. Penno TSVWG R. Penno
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Best Current Practice S. Perreault Updates: 4787, 5382, 5508 (if approved) S. Perreault
Expires: February 15, 2016 Jive Communications Intended status: Best Current Practice Jive Communications
M. Boucadair Expires: May 7, 2016 M. Boucadair
France Telecom France Telecom
S. Sivakumar S. Sivakumar
Cisco Cisco
K. Naito K. Naito
NTT NTT
August 14, 2015 November 4, 2015
Network Address Translation (NAT) Behavioral Requirements Updates Network Address Translation (NAT) Behavioral Requirements Updates
draft-ietf-tsvwg-behave-requirements-update-04 draft-ietf-tsvwg-behave-requirements-update-05
Abstract Abstract
This document clarifies and updates several requirements of RFC4787, This document clarifies and updates several requirements of RFC4787,
RFC5382 and RFC5508 based on operational and development experience. RFC5382 and RFC5508 based on operational and development experience.
The focus of this document is NAT44. The focus of this document is NAT44.
This document updates RFC4787, RFC5382 and RFC5508.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 15, 2016. This Internet-Draft will expire on May 7, 2016.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. TCP Session Tracking . . . . . . . . . . . . . . . . . . . . 3 2. TCP Session Tracking . . . . . . . . . . . . . . . . . . . . 3
2.1. TCP Transitory Connection Idle-Timeout . . . . . . . . . 4 2.1. TCP Transitory Connection Idle-Timeout . . . . . . . . . 5
2.2. TCP RST . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. TCP RST . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Port Overlapping Behavior . . . . . . . . . . . . . . . . . . 5 3. Port Overlapping Behavior . . . . . . . . . . . . . . . . . . 5
4. Address Pooling Paired (APP) . . . . . . . . . . . . . . . . 6 4. Address Pooling Paired (APP) . . . . . . . . . . . . . . . . 6
5. EIF Protocol Independence . . . . . . . . . . . . . . . . . . 6 5. EIM Protocol Independence . . . . . . . . . . . . . . . . . . 6
6. EIF Mapping Refresh . . . . . . . . . . . . . . . . . . . . . 7 6. EIF Protocol Independence . . . . . . . . . . . . . . . . . . 7
6.1. Outbound Mapping Refresh and Error Packets . . . . . . . 7 7. EIF Mapping Refresh . . . . . . . . . . . . . . . . . . . . . 7
7. EIM Protocol Independence . . . . . . . . . . . . . . . . . . 7 7.1. Outbound Mapping Refresh and Error Packets . . . . . . . 8
8. Port Parity . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Port Parity . . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Port Randomization . . . . . . . . . . . . . . . . . . . . . 8 9. Port Randomization . . . . . . . . . . . . . . . . . . . . . 8
10. IP Identification (IP ID) . . . . . . . . . . . . . . . . . . 8 10. IP Identification (IP ID) . . . . . . . . . . . . . . . . . . 9
11. ICMP Query Mappings Timeout . . . . . . . . . . . . . . . . . 8 11. ICMP Query Mappings Timeout . . . . . . . . . . . . . . . . . 9
12. Hairpinning Support for ICMP Packets . . . . . . . . . . . . 9 12. Hairpinning Support for ICMP Packets . . . . . . . . . . . . 9
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
14. Security Considerations . . . . . . . . . . . . . . . . . . . 9 14. Security Considerations . . . . . . . . . . . . . . . . . . . 9
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
15.1. Normative References . . . . . . . . . . . . . . . . . . 10 15.1. Normative References . . . . . . . . . . . . . . . . . . 10
15.2. Informative References . . . . . . . . . . . . . . . . . 11 15.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
[RFC4787], [RFC5382] and [RFC5508] greatly advanced NAT [RFC4787], [RFC5382] and [RFC5508] greatly advanced Network Address
interoperability and conformance. But with widespread deployment and Translation (NAT) interoperability and conformance. Operational
evolution of Network Address Translation (NAT) more development and experience gained through widespread deployment and evolution of NAT
operational experience was acquired some areas of the original indicates that some areas of the original documents need further
documents need further clarification or updates. This document clarification or updates. This document provides such clarifications
provides such clarifications and updates. and updates.
1.1. Scope 1.1. Scope
The goal of this document is to clarify and update the set of The goal of this document is to clarify and update the set of
requirements listed in [RFC4787], [RFC5382] and [RFC5508]. The requirements listed in [RFC4787], [RFC5382] and [RFC5508]. The
document focuses exclusively on NAT44. document focuses exclusively on NAT44.
The scope of this document has been set so that it does not create The scope of this document has been set so that it does not create
new requirements beyond those specified in the documents cited above. new requirements beyond those specified in the documents cited above.
Carrier-Grade NAT (CGN) related requirements are defined in Carrier-Grade NAT (CGN) related requirements are defined in
[RFC6888]. [RFC6888].
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The reader is assumed to be familiar withe terminology defined in: The reader is assumed to be familiar withe terminology defined in:
skipping to change at page 4, line 23 skipping to change at page 4, line 40
| C FIN | | S FIN | | | C FIN | | S FIN | |
| RCV | | RCV | | | RCV | | RCV | |
+---------+ +----------+ | +---------+ +----------+ |
| | | | | |
Server FIN Client FIN TCP_TRANS Server FIN Client FIN TCP_TRANS
| | T.O. | | T.O.
V V | V V |
+----------------------+ | +----------------------+ |
| C FIN + S FIN RCV |-----------------+ | C FIN + S FIN RCV |-----------------+
+----------------------+ +----------------------+
Legend: Legend:
* Messages sent to (resp. received from) the server * Messages sent or received from the server are
are prefixed with "Server". prefixed with "Server".
* Messages sent to (resp. received from) the client * Messages sent or received from the client are
are prefixed with "Client". prefixed with "Client".
* "C" means "Client-side" * "C" means "Client-side"
* "S" means "Server-side". * "S" means "Server-side".
* TCP_EST T.O: refers to the established connection * TCP_EST T.O: refers to the established connection
idle timeout as defined in [RFC5382]. idle timeout as defined in [RFC5382].
* TCP_TRANS T.O: refers to the transitory connection * TCP_TRANS T.O: refers to the transitory connection
idle timeout as defined in [RFC5382]. idle timeout as defined in [RFC5382].
Figure 1: State Machine Figure 1: Simplified version of the TCP State Machine
2.1. TCP Transitory Connection Idle-Timeout 2.1. TCP Transitory Connection Idle-Timeout
The transitory connection idle-timeout is defined as the minimum time The transitory connection idle-timeout is defined as the minimum time
a TCP connection in the partially open or closing phases must remain a TCP connection in the partially open or closing phases must remain
idle before the NAT considers the associated session a candidate for idle before the NAT considers the associated session a candidate for
removal (REQ-5 of [RFC5382]). But [RFC5382] does not clearly state removal (REQ-5 of [RFC5382]). But [RFC5382] does not clearly state
whether these can be configured separately. whether these can be configured separately.
Clarification: This document clarifies that a NAT SHOULD provide Clarification: This document clarifies that a NAT SHOULD provide
different configurable parameters for configuring the open and different configurable parameters for configuring the open and
closing idle timeouts. closing idle timeouts.
To accommodate deployments that consider a partially open timeout To accommodate deployments that consider a partially open timeout
of 4 minutes as being excessive from a security standpoint, a NAT of 4 minutes as being excessive from a security standpoint, a NAT
MAY allow to configure the timeout to be less than 4 minutes. MAY allow the configured timeout to be less than 4 minutes.
Still, this specification recommends the default "transitory However, a minimum default transitory connection idle-timeout of 4
connection idle-timeout" minimum value to be set to 4 minutes. minutes is RECOMMENDED.
2.2. TCP RST 2.2. TCP RST
[RFC5382] leaves the handling of TCP RST packets unspecified. [RFC5382] leaves the handling of TCP RST packets unspecified.
Update: This document adopts a similar default behavior as in Update: This document adopts a similar default behavior as in
[RFC6146]. Concretely, when the NAT receives a TCP RST matching [RFC6146]. Concretely, when the NAT receives a TCP RST matching
an existing mapping, it MUST translate the packet according the an existing mapping, it MUST translate the packet according the
NAT mapping entry. Moreover, the NAT SHOULD wait for 4 minutes NAT mapping entry. Moreover, the NAT SHOULD wait for 4 minutes
before deleting the session and removing any state associate with before deleting the session and removing any state associated with
it if no packets are received during that 4 minutes timeout. it if no packets are received during that 4 minutes timeout.
Admittedly, the NAT has to verify whether received TCP RST packets Admittedly, the NAT has to verify whether received TCP RST packets
belong to a connection. These verification checks are required to belong to a connection. This verification check is required to
avoid off-path attacks. avoid off-path attacks.
If the NAT removes immediately the NAT mapping upon receipt of a If the NAT removes immediately the NAT mapping upon receipt of a
TCP RST message, stale connections may be maintained by endpoints TCP RST message, stale connections may be maintained by endpoints
if the first RST message is lost between the NAT and the if the first RST message is lost between the NAT and the
recipient. recipient.
3. Port Overlapping Behavior 3. Port Overlapping Behavior
REQ-1 from [RFC4787] and REQ-1 from [RFC5382] specify a specific port REQ-1 from [RFC4787] and REQ-1 from [RFC5382] specify a specific port
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This enables concurrent use of a single NAT external port for This enables concurrent use of a single NAT external port for
multiple transport sessions, which allows a NAT to successfully multiple transport sessions, which allows a NAT to successfully
process packets in an IP address resource limited network (e.g., process packets in an IP address resource limited network (e.g.,
deployment with high address space multiplicative factor (refer to deployment with high address space multiplicative factor (refer to
Appendix B. of [RFC6269])). Appendix B. of [RFC6269])).
4. Address Pooling Paired (APP) 4. Address Pooling Paired (APP)
The Address Pooling Paired (APP) behavior for a NAT was recommended The Address Pooling Paired (APP) behavior for a NAT was recommended
in REQ-2 from [RFC4787], but the behavior when a public IPv4 runs out in REQ-2 from [RFC4787], but the behavior when an external IPv4 runs
of ports was left undefined. out of ports was left undefined.
Clarification: This document clarifies that if APP is enabled, new Clarification: This document clarifies that if APP is enabled, new
sessions from a host that already has a mapping associated with an sessions from a host that already has a mapping associated with an
external IP that ran out of ports SHOULD be dropped. external IP that ran out of ports SHOULD be dropped. A
configuration parameter MAY be provided to allow a NAT to starting
using ports from another external IP address when the one that
anchored the APP mapping ran out of ports. Tweaking this
configuration parameter is a trade-off between service continuity
and APP strict enforcement. Note, this behavior is sometimes
referred as 'soft-APP'.
The administrator MAY provide a configurable parameter that allows As a reminder, the recommendation for the particular case of a CGN
a NAT to starting using ports from another external IP address is that an implementation must use the same external IP address
when the one that anchored the APP mapping ran out of ports. This mapping for all sessions associated with the same internal IP
is a trade-off between service continuity and APP strict address, be they TCP, UDP, ICMP, something else, or a mix of
enforcement. (Note, this behavior is sometimes referred as 'soft- different protocols [RFC6888].
APP'.)
Update: This behavior SHOULD apply also for TCP. Update: This behavior SHOULD apply also for TCP.
5. EIF Protocol Independence 5. EIM Protocol Independence
REQ-1 from [RFC4787] and REQ-1 from [RFC5382] do not specify whether
EIM are protocol-dependent or protocol-independent. For example, if
an outbound TCP SYN creates a mapping, it is left undefined whether
outbound UDP packets can reuse such mapping.
Update: EIM mappings SHOULD be protocol-dependent. A configuration
parameter MAY be provided to allow protocols that multiplex TCP
and UDP over the same source IP address and port number to use a
single mapping. The default value of this configuration parameter
MUST be protocol-dependent EIM.
This update is compliant with the stateful NAT64 [RFC6146] that
clearly specifies three binding information bases (TCP, UDP,
ICMP).
6. EIF Protocol Independence
REQ-8 from [RFC4787] and REQ-3 from [RFC5382] do not specify whether REQ-8 from [RFC4787] and REQ-3 from [RFC5382] do not specify whether
EIF mappings are protocol-independent. In other words, if an EIF mappings are protocol-independent or protocol-dependent . For
outbound TCP SYN creates a mapping, it is left undefined whether example, if an outbound TCP SYN creates a mapping, it is left
inbound UDP packets destined to that mapping should be forwarded. undefined whether inbound UDP packets matching that mapping should be
accepted or rejected.
Update: This document specifies that EIF mappings SHOULD be Update: EIF filtering SHOULD be protocol-dependent. A configuration
protocol-independent in order allow inbound packets for protocols parameter MAY be provided to make it protocol-independent. The
that multiplex TCP and UDP over the same IP address and port default value of this configuration parameter MUST be protocol-
through the NAT and also maintain compatibility with stateful dependent EIF.
NAT64 . The administrator MAY provide a configuration parameter to
make it protocol-dependent. The default value of this This behavior is aligned with the update in Section 5.
configuration parameter is to allow for protocol-independent EIF.
Applications that can be transported over a variety of transport Applications that can be transported over a variety of transport
protocols and/or support transport fall back schemes won't protocols and/or support transport fall back schemes won't
experience connectivity failures as a function of the underlying experience connectivity failures if the NAT is configured with
transport protocol or the filtering mode enabled at the NAT. protocol-independent EIM and protocol-independent EIF.
6. EIF Mapping Refresh 7. EIF Mapping Refresh
The NAT mapping Refresh direction may have a "NAT Inbound refresh The NAT mapping Refresh direction may have a "NAT Inbound refresh
behavior" of "True" according to REQ-6 from [RFC4787], but [RFC4787] behavior" of "True" according to REQ-6 from [RFC4787], but [RFC4787]
does not clarify how this behavior applies to EIF mappings. The does not clarify how this behavior applies to EIF mappings. The
issue in question is whether inbound packets that match an EIF issue in question is whether inbound packets that match an EIF
mapping but do not create a new session due to a security policy mapping but do not create a new session due to a security policy
should refresh the mapping timer. should refresh the mapping timer.
Clarification: This document clarifies that even when a NAT has an Clarification: This document clarifies that even when a NAT has an
inbound refresh behavior set to 'TRUE', such packets SHOULD NOT inbound refresh behavior set to 'TRUE', such packets SHOULD NOT
refresh the mapping. Otherwise a simple attack of a packet every refresh the mapping. Otherwise a simple attack of a packet every
2 minutes can keep the mapping indefinitely. 2 minutes can keep the mapping indefinitely.
Update: This behavior SHOULD apply also for TCP. Update: This behavior SHOULD apply also for TCP.
6.1. Outbound Mapping Refresh and Error Packets 7.1. Outbound Mapping Refresh and Error Packets
Update: In the case of NAT outbound refresh behavior there are Update: In the case of NAT outbound refresh behavior there are
certain types of packets that should not refresh the mapping even certain types of packets that should not refresh the mapping even
if their direction is outbound. For example, if the mapping is if their direction is outbound. For example, if the mapping is
kept alive by ICMP Errors or TCP RST outbound packets sent as kept alive by ICMP Errors or TCP RST outbound packets sent as
response to inbound packets, these SHOULD NOT refresh the mapping. response to inbound packets, these SHOULD NOT refresh the mapping.
7. EIM Protocol Independence
REQ-1 from [RFC4787] and REQ-1 from [RFC5382] do not specify whether
EIM are protocol-independent. In other words, if a outbound TCP SYN
creates a mapping it is left undefined whether outbound UDP can reuse
such mapping and create session. On the other hand, stateful NAT64
[RFC6146] clearly specifies three binding information bases (TCP,
UDP, ICMP).
Update: EIM mappings SHOULD be protocol-dependent. A configuration
parameter MAY be provided in order allow protocols that multiplex
TCP and UDP over the same source IP address and port number to use
a single mapping.
8. Port Parity 8. Port Parity
Update: A NAT MAY disable port parity preservation for all dynamic Update: A NAT MAY disable port parity preservation for all dynamic
mappings. Nevertheless, A NAT SHOULD support means to explicitly mappings. Nevertheless, A NAT SHOULD support means to explicitly
request to preserve port parity (e.g., [I-D.ietf-pcp-port-set]). request to preserve port parity (e.g., [I-D.ietf-pcp-port-set]).
Note: According to [RFC6887], dynamic mappings are said to be Note: According to [RFC6887], dynamic mappings are said to be
dynamic in the sense that they are created on demand, either dynamic in the sense that they are created on demand, either
implicitly or explicitly: implicitly or explicitly:
1. Implicit dynamic mappings refer to mappings that are created 1. Implicit dynamic mappings refer to mappings that are created
as a side effect of traffic such as an outgoing TCP SYN or as a side effect of traffic such as an outgoing TCP SYN or
outgoing UDP packet. Implicit dynamic mappings usually have a outgoing UDP packet. Implicit dynamic mappings usually have a
finite lifetime, though this lifetime is generally not known finite lifetime, though this lifetime is generally not known
to the client using them. to the client using them.
2. Explicit dynamic mappings refer to mappings that are created 2. Explicit dynamic mappings refer to mappings that are created
as a result, for example, of explicit PCP MAP and PEER as a result, for example, of explicit Port Control Protocol
requests. Explicit dynamic mappings have a finite lifetime, (PCP) MAP and PEER requests. Explicit dynamic mappings have a
and this lifetime is communicated to the client. finite lifetime, and this lifetime is communicated to the
client.
9. Port Randomization 9. Port Randomization
Update: A NAT SHOULD follow the recommendations specified in Update: A NAT SHOULD follow the recommendations specified in
Section 4 of [RFC6056], especially: Section 4 of [RFC6056], especially:
"A NAPT that does not implement port preservation [RFC4787] "A NAPT that does not implement port preservation [RFC4787]
[RFC5382] SHOULD obfuscate selection of the ephemeral port of a [RFC5382] SHOULD obfuscate selection of the ephemeral port of a
packet when it is changed during translation of that packet. A packet when it is changed during translation of that packet. A
NAPT that does implement port preservation SHOULD obfuscate the NAPT that does implement port preservation SHOULD obfuscate the
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port number to 0 or 1 according to whether even or odd parity port number to 0 or 1 according to whether even or odd parity
is desired)." is desired)."
10. IP Identification (IP ID) 10. IP Identification (IP ID)
Update: A NAT SHOULD handle the Identification field of translated Update: A NAT SHOULD handle the Identification field of translated
IPv4 packets as specified in Section 5.3.1 of [RFC6864]. IPv4 packets as specified in Section 5.3.1 of [RFC6864].
11. ICMP Query Mappings Timeout 11. ICMP Query Mappings Timeout
Section 3.1 of [RFC5508] precises that ICMP Query Mappings are to be Section 3.1 of [RFC5508] specifies that ICMP Query Mappings are to be
maintained by a NAT. However, the specification doesn't discuss maintained by a NAT. However, the specification doesn't discuss
Query Mapping timeout values. Section 3.2 of [RFC5508] only Query Mapping timeout values. Section 3.2 of [RFC5508] only
discusses ICMP Query Session Timeouts. discusses ICMP Query Session Timeouts.
Update: ICMP Query Mappings MAY be deleted once the last the session Update: ICMP Query Mappings MAY be deleted once the last session
using the mapping is deleted. using the mapping is deleted.
12. Hairpinning Support for ICMP Packets 12. Hairpinning Support for ICMP Packets
REQ-7 from [RFC5508] specifies that a NAT enforcing 'Basic NAT' must REQ-7 from [RFC5508] specifies that a NAT enforcing 'Basic NAT' must
support traversal of hairpinned ICMP Query sessions. support traversal of hairpinned ICMP Query sessions.
Clarification: This implicitly means that address mappings from Clarification: This implicitly means that address mappings from
external address to internal address (similar to Endpoint external address to internal address (similar to Endpoint
Independent Filters) must be maintained to allow inbound ICMP Independent Filters) must be maintained to allow inbound ICMP
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Because some of the clarifications and updates (e.g., Section 2) are Because some of the clarifications and updates (e.g., Section 2) are
inspired from NAT64, the security considerations discussed in inspired from NAT64, the security considerations discussed in
Section 5 of [RFC6146] apply also for this specification. Section 5 of [RFC6146] apply also for this specification.
The update in Section 3 allows for an optimized NAT resource usage. The update in Section 3 allows for an optimized NAT resource usage.
In order to avoid service disruption, the NAT MUST invoke this In order to avoid service disruption, the NAT MUST invoke this
functionality only if packets are to be sen to distinct destination functionality only if packets are to be sen to distinct destination
addresses. addresses.
Some of the updates (e.g., Section 6, Section 9, and Section 11) Some of the updates (e.g., Section 7, Section 9, and Section 11)
allow for an increased security compared to [RFC4787], [RFC5382], and allow for an increased security compared to [RFC4787], [RFC5382], and
[RFC5508]. Particularly: [RFC5508]. Particularly:
o The updates in Section 6 and Section 11 prevent an illegitimate o The updates in Section 7 and Section 11 prevent an illegitimate
node to maintain mappings activated in the NAT while these node to maintain mappings activated in the NAT while these
mappings should be cleared. mappings should be cleared.
o Port randomization (Section 9) complicates tracking hosts located o Port randomization (Section 9) complicates tracking hosts located
behind a NAT. behind a NAT.
Section 4 and Section 12 propose updates that increase the Section 4 and Section 12 propose updates that increase the
serviceability of a host located behind a NAT. These updates do not serviceability of a host located behind a NAT. These updates do not
introduce any additional security concerns to [RFC4787], [RFC5382], introduce any additional security concerns to [RFC4787], [RFC5382],
and [RFC5508]. and [RFC5508].
The updates in Section 5 and Section 7 allow for a better NAT The updates in Section 5 and Section 6 allow for a better NAT
transparency from an application standpoint. Hosts which require a transparency from an application standpoint. Hosts which require a
restricted filtering behavior should enable security-dedicated restricted filtering behavior should enable security-dedicated
features (e.g., ACL) either locally or by soliciting a dedicated features (e.g., access control list (ACL)) either locally or by
security device (e.g., firewall). soliciting a dedicated security device (e.g., firewall).
The update in Section 8 induces security concerns that are specific The update in Section 8 induces security concerns that are specific
to the protocol used to interact with the NAT. For example, if PCP to the protocol used to interact with the NAT. For example, if PCP
is used to explicitly request parity preservation for a given is used to explicitly request parity preservation for a given
mapping, the security considerations discussed in [RFC6887] should be mapping, the security considerations discussed in [RFC6887] should be
taken into account. taken into account.
The update in Section 10 may have undesired effects on the The update in Section 10 may have undesired effects on the
performance of the NAT in environments in which fragmentation is performance of the NAT in environments in which fragmentation is
massively experienced. Such issue may be used as an attack vector massively experienced. Such issue may be used as an attack vector
skipping to change at page 11, line 19 skipping to change at page 11, line 34
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6 NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <http://www.rfc-editor.org/info/rfc6146>. April 2011, <http://www.rfc-editor.org/info/rfc6146>.
[RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field", [RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field",
RFC 6864, DOI 10.17487/RFC6864, February 2013, RFC 6864, DOI 10.17487/RFC6864, February 2013,
<http://www.rfc-editor.org/info/rfc6864>. <http://www.rfc-editor.org/info/rfc6864>.
[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, <http://www.rfc-editor.org/info/rfc6888>.
15.2. Informative References 15.2. Informative References
[I-D.ietf-pcp-port-set] [I-D.ietf-pcp-port-set]
Qiong, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, Qiong, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou,
T., and S. Perreault, "Port Control Protocol (PCP) T., and S. Perreault, "Port Control Protocol (PCP)
Extension for Port Set Allocation", draft-ietf-pcp-port- Extension for Port Set Allocation", draft-ietf-pcp-port-
set-09 (work in progress), May 2015. set-13 (work in progress), October 2015.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations", Translator (NAT) Terminology and Considerations",
RFC 2663, DOI 10.17487/RFC2663, August 1999, RFC 2663, DOI 10.17487/RFC2663, August 1999,
<http://www.rfc-editor.org/info/rfc2663>. <http://www.rfc-editor.org/info/rfc2663>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001, DOI 10.17487/RFC3022, January 2001,
<http://www.rfc-editor.org/info/rfc3022>. <http://www.rfc-editor.org/info/rfc3022>.
skipping to change at page 12, line 5 skipping to change at page 12, line 15
[RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and [RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
P. Roberts, "Issues with IP Address Sharing", RFC 6269, P. Roberts, "Issues with IP Address Sharing", RFC 6269,
DOI 10.17487/RFC6269, June 2011, DOI 10.17487/RFC6269, June 2011,
<http://www.rfc-editor.org/info/rfc6269>. <http://www.rfc-editor.org/info/rfc6269>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and [RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013, DOI 10.17487/RFC6887, April 2013,
<http://www.rfc-editor.org/info/rfc6887>. <http://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, <http://www.rfc-editor.org/info/rfc6888>.
Acknowledgements Acknowledgements
Thanks to Dan Wing, Suresh Kumar, Mayuresh Bakshi, Rajesh Mohan, Lars Thanks to Dan Wing, Suresh Kumar, Mayuresh Bakshi, Rajesh Mohan, Lars
Eggert, and Gorry Fairhurst for their review and discussion. Eggert, Gorry Fairhurst, and Brandon Williams for their review and
discussion.
Contributors Contributors
The following individual contributed text to the document: The following individual contributed text to the document:
Sarat Kamiset, Insieme Networks, United States Sarat Kamiset, Insieme Networks, United States
Authors' Addresses Authors' Addresses
Reinaldo Penno Reinaldo Penno
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