Network Working Group G. Van de Velde
Internet-Draft T. Hain
Expires: July 28, 2005 R. Droms
Cisco Systems
B. Carpenter
IBM Corporation
E. Klein
TTI Telecom
January 24, 2005
IPv6 Network Architecture Protection
<draft-vandevelde-v6ops-nap-01.txt>
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
Although there are many perceived benefits to Network Address
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Translation (NAT), its primary benefit of "amplifying" available
address space is not needed in IPv6. In addition to NAT's many
serious disadvantages, there is a perception that other benefits
exist, such as a variety of management and security attributes that
could be useful for an Internet Protocol site. IPv6 does not support
NAT by design and this document shows how Network Architecture
Protection (NAP) using IPv6 can provide the same or more benefits
without the need for NAT.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Perceived benefits of NAT and its impact on IPv4 . . . . . . 6
2.1 Simple gateway between Internet and internal network . . . 6
2.2 Simple security due to stateful filter implementation . . 6
2.3 User/Application tracking . . . . . . . . . . . . . . . . 7
2.4 Privacy and topology hiding . . . . . . . . . . . . . . . 7
2.5 Independent control of addressing in a private network . . 8
2.6 Global address pool conservation . . . . . . . . . . . . . 8
2.7 Multihoming and renumbering with NAT . . . . . . . . . . . 9
3. Description of the IPv6 tools . . . . . . . . . . . . . . . 9
3.1 Privacy addresses (RFC 3041) . . . . . . . . . . . . . . . 9
3.2 Unique Local Addresses . . . . . . . . . . . . . . . . . . 10
3.3 DHCPv6 prefix delegation . . . . . . . . . . . . . . . . . 11
3.4 Untraceable IPv6 addresses . . . . . . . . . . . . . . . . 11
4. Using IPv6 technology to provide the market perceived
benefits of NAT . . . . . . . . . . . . . . . . . . . . . . 12
4.1 Simple gateway between Internet and internal network . . . 12
4.2 IPv6 and Simple security . . . . . . . . . . . . . . . . . 12
4.3 User/Application tracking . . . . . . . . . . . . . . . . 14
4.4 Privacy and topology hiding using IPv6 . . . . . . . . . . 14
4.5 Independent control of addressing in a private network . . 15
4.6 Global address pool conservation . . . . . . . . . . . . . 15
4.7 Multihoming and renumbering . . . . . . . . . . . . . . . 16
5. Case Studies . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1 Medium/large private networks . . . . . . . . . . . . . . 17
5.2 Small private networks . . . . . . . . . . . . . . . . . . 18
5.3 Single user connection . . . . . . . . . . . . . . . . . . 20
5.4 ISP/Carrier customer networks . . . . . . . . . . . . . . 20
6. IPv6 gap analysis . . . . . . . . . . . . . . . . . . . . . 21
6.1 Completion of work on ULAs . . . . . . . . . . . . . . . . 21
6.2 Subnet topology masking . . . . . . . . . . . . . . . . . 22
6.3 Minimal traceability of privacy addresses . . . . . . . . 22
6.4 Renumbering procedure . . . . . . . . . . . . . . . . . . 22
6.5 Site multihoming . . . . . . . . . . . . . . . . . . . . . 22
6.6 Untraceable addresses . . . . . . . . . . . . . . . . . . 22
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . 23
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9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 23
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1 Normative References . . . . . . . . . . . . . . . . . . 24
11.2 Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 25
A. Additional benefits due to Native IPv6 and universal
unique addressing . . . . . . . . . . . . . . . . . . . . . 26
A.1 Universal any-to-any connectivity . . . . . . . . . . . . 26
A.2 Auto-configuration . . . . . . . . . . . . . . . . . . . . 27
A.3 Native Multicast services . . . . . . . . . . . . . . . . 27
A.4 Increased security protection . . . . . . . . . . . . . . 28
A.5 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 28
A.6 Merging networks . . . . . . . . . . . . . . . . . . . . . 29
A.7 Community of interest . . . . . . . . . . . . . . . . . . 29
B. Revision history . . . . . . . . . . . . . . . . . . . . . . 29
B.1 Changes from *-nap-00 to *-nap-01 . . . . . . . . . . . . 29
Intellectual Property and Copyright Statements . . . . . . . 30
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1. Introduction
Although there are many perceived benefits to Network Address
Translation (NAT), its primary benefit of "amplifying" available
address space is not needed in IPv6. The serious disadvantages of
ambiguous "private" address space and of Network Address Translation
(NAT) [2][6] have been well documented [5][7]. However, given its
wide market acceptance NAT undoubtedly has some perceived benefits.
Indeed, in an Internet model based on universal any-to-any
connectivity, product marketing departments have driven a perception
that some connectivity and security concerns can only be solved by
using a NAT device or by using logically separated LAN address
spaces. This document describes the market-perceived reasons to
utilize a NAT device in an IPv4 environment and shows how these needs
can be met and even exceeded with IPv6. The use of the facilities
from IPv6 described in this document avoids the negative impacts of
translation and may be described as Network Architecture Protection
(NAP).
As far as security and privacy is concerned, this document considers
how to mitigate a number of threats. Some are obviously external,
such as having a hacker trying to penetrate your network, or having a
worm infected machine outside your network trying to attack it. Some
are local such as a disgruntled employee disrupting business
operations, or the unintentional negligence of a user downloading
some malware which then proceeds to attack any device on the LAN.
Some may be embedded such as having some firmware in a domestic
appliance "call home" to its manufacturer without the user's consent.
This document describes several techniques that may be combined on an
IPv6 site to protect the integrity of its network architecture.
These techniques, known collectively as NAP, retain the concept of a
well defined boundary between "inside" and "outside" the private
network, and allow firewalling, topology hiding, and privacy and will
achieve these goals without address translation.
IPv6 Network Architecture Protection can be summarized in the
following table. It presents the marketed functions of NAT with a
cross-reference of how those are delivered in both the IPv4 and IPv6
environments.
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Function IPv4 IPv6
+------------------+-----------------------+-----------------------+
| Simple Gateway | DHCP - single | DHCP-PD - arbitrary |
| as default router| address upstream | length customer |
| and address pool | DHCP - limited | prefix upstream |
| manager | number of individual | SLAAC via RA |
| | devices downstream | downstream |
| | see section 2.1 | see section 4.1 |
+------------------|-----------------------|-----------------------+
| Simple Security | Filtering side | Explicit Context |
| | effect due to lack | Based Access Control |
| | of translation state | (Reflexive ACL) |
| | see section 2.2 | see section 4.2 |
+------------------|-----------------------|-----------------------+
| Local usage | NAT state table | Address uniqueness |
| tracking | | |
| | see section 2.3 | see section 4.3 |
+------------------|-----------------------|-----------------------+
| End system | NAT transforms | Temporary use |
| privacy | device ID bits in | privacy addresses |
| | the address | |
| | see section 2.4 | see section 4.4 |
+------------------|-----------------------|-----------------------+
| Topology hiding | NAT transforms | Untraceable addresses|
| | subnet bits in the | using IGP host routes|
| | address | /or MIPv6 tunnels for|
| | | stationary systems |
| | see section 2.4 | see section 4.4 |
+------------------|-----------------------|-----------------------+
| Addressing | RFC 1918 | RFC 3177 & ULA |
| Autonomy | | |
| | see section 2.5 | see section 4.5 |
+------------------|-----------------------|-----------------------+
| Global Address | RFC 1918 | 340,282,366,920,938, |
| Pool | | 463,463,374,607,431, |
| Conservation | | 768,211,456 |
| | | (3.4*10^38) addresses|
| | see section 2.6 | see section 4.6 |
+------------------|-----------------------|-----------------------+
| Renumbering and | Address translation | Preferred lifetime |
| Multi-homing | at border | per prefix & Multiple|
| | | addresses per |
| | | interface |
| | see section 2.7 | see section 4.7 |
+------------------+-----------------------+-----------------------+
This document first identifies the perceived benefits of NAT in more
detail, and then shows how IPv6 NAP can provide each of them. It
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concludes with a IPv6 NAP case study and a gap analysis of work that
remains to be done for a complete NAP solution.
2. Perceived benefits of NAT and its impact on IPv4
This section provides visibility into the generally perceived
benefits of the use of IPv4 NAT. The goal of this description is not
to analyze these benefits or discuss the accuracy of the perception
(detailed discussions in [5]) , but to describe the deployment
requirements and set a context for the later descriptions of the IPv6
approaches for dealing with those requirements.
2.1 Simple gateway between Internet and internal network
A NAT device can connect a private network with any kind of address
(ambiguous [RFC 1918] or global registered address) towards the
Internet. The address space of the private network can be built from
globally unique addresses, from ambiguous address space or from both
simultaneously. Without specific configuration from public to
private, the NAT device enables access between the client side of an
application in the private network with the server side in the public
Internet.
Wide-scale deployments have shown that using NAT to attach a private
IPv4 network to the Internet is simple and practical for the
non-technical end user. Frequently a simple user interface is
sufficient for configuring both device and application access rights.
Additionally, thanks to successful marketing campaigns it is
perceived by end users that their equipment is protected from the bad
elements and attackers on the public IPv4 Internet.
2.2 Simple security due to stateful filter implementation
It is frequently believed that a NAT device puts in an extra barrier
to keep the private network protected from evil outside influences
due to the session-oriented character of NAT technology. Since a NAT
typically keeps state only for individual sessions, attackers, worms,
etc. cannot exploit this state to attack a host in general and on
any port. This benefit may be partially real; however, experienced
hackers are well aware of NAT devices and are very familiar with
private address space, and have devised methods of attack (such as
trojan horses) that readily penetrate NAT boundaries. The secure
feeling is in vain.
Address translation does not provide security in itself; for example,
consider a configuration with static NAT translation and all inbound
ports translating to a single machine. In such a scenario the
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security risk for that machine is identical to the case with no NAT
device in the communication path. As result there is no specific
security value in the address translation function. The perceived
security comes from the lack of pre-established or permanent mapping
state. Dynamically establishing state in response to internal
requests reduces the threat of unexpected external connections to
internal devices.
In some cases, NAT operators (including domestic users) may be
obliged to configure quite complex port mapping rules to allow
external access to local applications such as a multi-player game or
web servers. In this case the NAT actually adds management
complexity compared to a simple router. In situations where 2 or
more devices need to host the same application this complexity shifts
from difficult to impossible.
2.3 User/Application tracking
Although NATs create temporary state for active sessions, in general
they provide limited capabilities for the administrator of the NAT to
gather information about who in the private network is requesting
access to which Internet location. This could in theory be done by
logging the network address translation details of the private and
the public addresses of the NAT devices state database.
The checking of this database is not always a simple task, especially
if Port Address Translation is used. It also has an unstated
assumption that the administrative instance has a mapping between an
IPv4-address and a network element or user at all times, or the
administrator has a time-correlated list of the address/port
mappings.
2.4 Privacy and topology hiding
The ability of NAT to provide internet access by the use of a single
(or few) global IPv4 routable addresses to a large community of users
offers a simple mechanism to hide the internal topology of a network.
In this scenario the large community will be reflected in the
internet by a single (or few) IPv4 address(es).
The use of NAT then results in a user behind a NAT gateway actually
appearing on the Internet as a user inside the NAT box itself; i.e.,
the IPv4 address that appears on the Internet is only sufficient to
identify the NAT. When concealed behind a NAT it is impossible to
tell from the outside which member of a family, which customer of an
Internet cafe, or which employee of a company generated or received a
particular packet. Thus, although NATs do nothing to provide
application level privacy, they do prevent the external tracking and
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profiling of individual host computers by means of their IP
addresses. At the same time a NAT creates a smaller pool of
addresses for a much more focused point of attack.
There is a similarity with privacy based on application level
proxies. When using an application level gateway for browsing the
web for example, the 'privacy' of a web user can be provided by
masking the true identity of the original web user towards the
outside world (although the details of what is - or is not - logged
at the NAT/proxy will be different).
Some enterprises prefer to hide as much as possible of their internal
network topology from outsiders. Mostly this is achieved by blocking
"traceroute" etc., but NAT of course entirely hides the internal
subnet topology, which some network managers believe is a useful
precaution to mitigate scanning attacks. Scanning for IPv6 can be
much harder in comparison with IPv4 as described in [18]
Once a list of available devices and IP addresses has been mapped, a
port-scan on these IP addresses can be performed. Scanning works by
tracking which ports do not receive unreachable errors from either
the firewall or host. With the list of open ports an attacker can
optimize the time needed for a successful attack by correlating it
with known vulnerabilities to reduce the number of attempts. For
example, FTP usually runs on port 21, and HTTP usually runs on port
80. These open ports could be used for initiating attacks on an end
system.
2.5 Independent control of addressing in a private network
Many private IPv4 networks take benefit from using the address space
defined in RFC 1918 to enlarge the available addressing space for
their private network, and at the same time reduce their need for
globally routable addresses. This type of local control of address
resources allows a clean and hierarchical addressing structure in the
network.
Another benefit is due to the usage of independent addresses on
majority of the network infrastructure there is an increased ability
to change provider with less operational difficulties.
2.6 Global address pool conservation
Due to the ongoing depletion of the IPv4 address range, the remaining
pool of unallocated IPv4 addresses is below 30%. While mathematical
models based on historical IPv4 prefix consumption periodically
attempt to predict the future exhaustion date of the IPv4 address
pool, a direct result of this continuous resource consumption is that
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the administrative overhead for acquiring globally unique IPv4
addresses will continue increasing in direct response to tightening
allocation policies. In response to the increasing administrative
overhead many Internet Service Providers (ISPs) have already resorted
to the ambiguous addresses defined in RFC 1918 behind a NAT for the
various services they provide as well as connections for their end
customers. In turn this has restricted the number of and types of
applications that can be deployed by these ISPs and their customers.
Forced into this limiting situation such customers can rightly claim
that despite the optimistic predictions of mathematical models the
global pool of IPv4 addresses is effectively already exhausted.
2.7 Multihoming and renumbering with NAT
The elements of multihoming and renumbering are quite different.
However, multihoming is often a transitional state for renumbering,
and NAT interacts with both in the same way.
For enterprise networks, it is highly desirable to be connected to
more than one Internet Service Provider (ISP) and to be able to
change ISPs at will. This means that a site must be able to operate
under more than one CIDR prefix [1] and/or readily change its CIDR
prefix. Unfortunately, IPv4 was not designed to facilitate either of
these maneuvers. However, if a site is connected to its ISPs via NAT
boxes, only those boxes need to deal with multihoming and renumbering
issues.
Similarly, if two enterprise IPv4 networks need to be merged, it may
well be that installing a NAT box between them will avoid the need to
renumber one or both. For any enterprise, this can be a short term
financial saving, and allow more time to renumber the network
components. The longterm solution is a single network without usage
of NAT to avoid the ongoing operational complexity of overlapping
addresses.
This solution may be sufficient for some networks; however when the
merging networks were already using address translation it will
create huge problems due to admistrative difficulties of the merged
address space.
3. Description of the IPv6 tools
This section describes several features that can be used to provide
the protection features associated with IPv4 NAT.
3.1 Privacy addresses (RFC 3041)
There are situations where it is desirable to prevent device
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profiling, such as by contacted web sites, so IPv6 privacy addresses
were defined to provide that capability. IPv6 addresses consist of a
routing prefix subnet-id part (SID) and an interface identifier part
(IID). For interfaces that contain embedded IEEE Link Identifiers
the interface identifier is typically derived from it, though this
practice facilitates tracking and profiling of a device as it moves
around the Internet. RFC 3041 describes an extension to IPv6
stateless address autoconfiguration for interfaces [8]. Use of the
privacy address extension causes nodes to generate global-scope
addresses from interface identifiers that change over time, even in
cases where the interface contains an embedded IEEE link identifier.
Changing the interface identifier (thus the global-scope addresses
generated from it) over time makes it more difficult for
eavesdroppers and other information collectors to identify when
addresses used in different transactions actually correspond to the
same node. A relatively short valid lifetime for the privacy address
also has the side effect of reducing the attack profile of a device,
as it is not directly attackable once it stops answering at the
temporary use address.
While the primary implementation and source of randomized RFC 3041
addresses is expected to be from end systems running stateless
autoconfiguration, there is nothing that prevents a DHCP server from
running the RFC 3041 algorithm for any new IEEE identifier it hears,
then remembering that for future queries. This would allow using
them in DNS for registered services since the assumption of a server
based deployment would be a persistent value that minimizes DNS
churn. A DHCP based deployment would also allow for local policy to
periodically change the entire collection of end device addresses
while maintaining some degree of central knowledge and control over
which addresses should be in use at any point in time.
Randomizing the IID, as defined in RFC 3041, only precludes tracking
of the lower 64 bits of the IPv6 address. Masking of the subnet ID
will require additional approaches as discussed below in 3.4.
Additional considerations are discussed in [17]. Providing privacy
for a subnet ID will require different technology.
3.2 Unique Local Addresses
Local network and application services stability during periods of
intermittent connectivity between one or more providers requires
address management autonomy. Such autonomy in a single routing
prefix environment would lead to massive expansion of the global
routing tables, so IPv6 provides for simultaneous use of multiple
prefixes. The Unique Local Address prefix (ULA) [16] has been set
aside for use in local communications. The ULA address prefix for
any network is routable over a locally defined collection of routers.
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These prefixes are NOT to be routed on the public global Internet as
that would have a serious negative impact on global routing.
ULAs have the following characteristics:
o Globally unique prefix
* Allows networks to be combined or privately interconnected
without creating any address conflicts or requiring renumbering
of interfaces using these prefixes
* If accidentally leaked outside of a network via routing or DNS,
there is no conflict with any other addresses
o ISP independent and can be used for communications inside of a
network without having any permanent or intermittent Internet
connectivity
o Well known prefix to allow for easy filtering at network
boundaries
o In practice, applications may treat these addresses like global
scoped addresses
3.3 DHCPv6 prefix delegation
The Prefix Delegation (DHCP-PD) options [11] provide a mechanism for
automated delegation of IPv6 prefixes using the Dynamic Host
Configuration Protocol (DHCP) [10]. This mechanism (DHCP-PD) is
intended for delegating a long-lived prefix from a delegating router
to a requesting router, across an administrative boundary, where the
delegating router does not require knowledge about the topology of
the links in the network to which the prefixes will be assigned.
3.4 Untraceable IPv6 addresses
These should be globally routable IPv6 addresses which can be
randomly and independently assigned to IPv6 devices.
The random assignment has as purpose to confuse the outside world on
the structure of the local network. However for the local network
there is a correlation between the location of the device and the
untraceable IPv6 address. This correlation could be done by
generating IPv6 host route entries or by utilizing an aggregation
device like a Mobile IPv6 Home Gateway.
The main goal of untraceable IPv6 addresses is to create an
apparently unpredictable network infrastructure as seen from external
networks to protect the local infrastructure from malicious outside
influences or from mapping any correlation between the network
activities of multiple devices from external networks. When using
untraceable IPv6 addresses, it could be that two apparently
sequential addresses are reachable on very different parts of the
local network instead of belonging to the same subnet next to each
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other.
4. Using IPv6 technology to provide the market perceived benefits of
NAT
The facilities in IPv6 can be used to provide the protection
perceived to be associated with IPv4 NAT. This section gives some
examples of how IPv6 can be used securely.
4.1 Simple gateway between Internet and internal network
As a simple gateway, the device has the role of managing both packet
Routing and local address management. A basic IPv6 router could have
a default configuration to advertize inside the site a locally
generated random ULA prefix, independently from the state of any
external connectivity. This would allow local nodes to communicate
amongst themselves prior to establishing a global connection. If the
network happened to concatenate with another local network, this is
highly unlikely to result in address collisions. With external
connectivity the simple gateway could also use DHCP-PD to acquire a
routing prefix from the service provider for use when connecting to
the global Internet. End node connections involving other nodes on
the global Internet will always use the global IPv6 addresses [9]
derived from this prefix delegation. In the very simple case there
is no explicit routing protocol and a single default route is used
out to the global Internet. A slightly more complex case might
involve local routing protocols, but with the entire local network
sharing a common global prefix there would still not be a need for an
external routing protocol as a default route would continue to be
consistent with the connectivity.
4.2 IPv6 and Simple security
The vulnerability of an IPv6 host is similar as for an IPv4 host
directly connected towards the Internet, and firewall and IDS systems
are recommended. However, with IPv6, the following protections are
available without the use of NAT:
1. Short lifetimes on privacy extension suffixes reduce the attack
profile since the node will not respond to the address once the
address is no longer valid.
2. IPsec is a mandatory service for IPv6 implementations. IPsec
functions to prevent session hijacking, prevent content
tampering, and optionally masks the packet contents. While IPsec
might be available in IPv4 implementations, deployment in NAT
environments either breaks the protocol or requires complex
helper services with limited functionality or efficiency.
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3. The size of the typical subnet ::/64 will make a network ping
sweep and resulting port-scan virtually impossible due to the
amount of possible combinations available. This goes from the
assumption that the attacker has no access to a local connection.
If an attacker has local access then he could use ND [4] and
ping6 to ff02::1 to detect local neighbors. (Of course, a
locally connected attacker has many scanning options with IPv4 as
well.) It is recommended for site administrators to take [18]
into consideration to achieve the expected goal.
IPv4 NAT was not developed as a security mechanism. Despite
marketing messages to the contrary it is not a security mechanism,
and hence it will pose some security holes while many people assume
their network is secure due to the usage of NAT. This is directly
the opposite of what IPv6 security best-practices are trying to
achieve.
An example of a potential set of firewall rules could be:
Source_A: IPv6 Home broadband user
located on the internal network
Destination_B: IPv6 HTTP server
located on the external network
On the edge broadband router a security rule could be:
Internal network -> external network:
Actions:
Allow all traffic
Create reflective session state (true) for the session
External network -> internal network
Actions:
If the session had reflective 'true'-state,
then allow the inbound traffic
If the session had reflective 'false' state,
then drop the traffic
This simple rule would create similar protection and security holes
the typical IPv4 NAT device will offer and may for example be enabled
by default on all broadband edge-routers,with that difference that
the security caveats will be documented, and may hence be removed
with the next revision of the rule. The goal is that at every
iteration, the IPv6 internet will become more secure for the
oblivious users.
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Assuming the network administrator is aware of [18] the increased
size of the IPv6 address will make topology probing much harder, and
almost impossible for IPv6 devices. What one does when topology
probing is to get an idea of the available hosts inside an
enterprise. This mostly starts with a ping-sweep. This is an
automated procedure of sending Internet Control Message Protocol
(ICMP) echo requests (also known as PINGs) to a range of IP addresses
and recording replies. This can enable an attacker to map the
network. Since the IPv6 subnets are 64 bits worth of address space,
this means that an attacker has to send out a simply unrealistic
number of pings to map the network, and virus/worm propagation will
be thwarted in the process. At full rate 40Gbps (400 times the
typical 100Mbps LAN, and 13,000 times the typical DSL/Cable access
link) it takes over 5000 years to scan a single 64 bit space.
4.3 User/Application tracking
IPv6 enables the collection of information about data flows. Due to
the fact that all addresses used for Internet and intra-/inter- site
communication are unique, it is possible for an enterprise or ISP to
get very detailed information on any communication exchange between
two or more devices. This enhances the capability of data-flow
tracking for security audits compared with IPv4 NAT, because in IPv6
a flow between a sender and receiver will always be uniquely
identified due to the unique IPv6 source and destination addresses.
4.4 Privacy and topology hiding using IPv6
Partial host privacy is achieved in IPv6 using pseudo-random privacy
addresses (RFC 3041) which are generated as required, so that a
session can use an address that is valid only for a limited time.
Exactly like IPv4 NAT, this only allows such a session to be traced
back to the subnet that originates it, but not immediately to the
actual host.
If a network manager wishes to conceal the internal IPv6 topology,
and the majority of its host computer addresses, a good option will
be to run all internal traffic using ULA since such packets can by
definition never exit the site. For hosts that do in fact need to
generate external traffic, by using multiple IPv6 addresses (ULAs and
one or more global addresses), it will be possible to hide and mask
some or all of the internal network. As discussed above, there are
multiple parts to the IPv6 address, and different techniques to
manage privacy for each.
When a network manager also wishes to conceal the internal IPv6
topology, by using explicit host routes it is possible to locate
nodes on one segment while they appear externally to be on another.
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An alternative method to hide the internal topology would be to use
Mobile IPv6 internally without route optimization where the public
facing addresses are consolidated on an edge Home Agent (HA), then
use MIPv6 in bidirectional tunnel mode between the HA and topology
masked node using the ULA as a COA This truly masks the internal
topology as all nodes with global access appear to share a common
subnet. There is no reason that rack mounted devices shouldn't be
considered mobile nodes to mask the internal topology. It looks
equivalent to running a VPN to a central server, however it does not
involve any encryption or significant overhead.
4.5 Independent control of addressing in a private network
IPv6 provides for autonomy in local use addresses through ULAs. At
the same time IPv6 simplifies simultaneous use of multiple addresses
per interface so that a NAT is not required (or even defined) between
the ULA and the public Internet. Nodes that need access to the
public Internet may have a ULA for local use, and will have a global
use address because the global use IPv6 address space is not a scarce
resource like the global use IPv4 space. While global IPv6
allocation policy is managed through the Regional Internet
Registries, it is expected that they will continue with derivatives
of RFC 3177 for the foreseeable future.
When using IPv6, the need to ask for more address space will become
far less likely due to the increased size of the subnets. These
subnets typically allow 2^64 hosts per subnet and an enterprise will
typically receive a /48 which allows segmentation into at least 2^16
different subnets.
The ongoing subnet size maintenance may become simpler when IPv6
technology is utilised. If IPv4 address space is optimised one has
periodically to look into the number of hosts on a segment and the
subnet size allocated to the segment; an enterprise today may have a
mix of /28 - /23 size subnets for example, and may shrink/grow these
as their network user base/etc changes. In v6, it's all /64.
4.6 Global address pool conservation
IPv6 provides sufficient space to completely avoid the need for
overlapping address space,
340,282,366,920,938,463,463,374,607,431,768,211,456 (3.4*10^38) total
possible addresses. As previously discussed, the serious
disadvantages of ambiguous address space have been well documented,
and with sufficient space there is no need to continue the
increasingly aggressive conservation practices that are necessary
with IPv4. While IPv6 allocation policies and ISP business practice
will continue to evolve, the recommendations in RFC 3177 are based on
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the technical potential of the vast IPv6 address space. That
document demonstrates that there is no resource limitation which will
lead to the IPv4 practice of ambiguous space behind a NAT. As an
example of the direct contrast, many expansion oriented IPv6
deployment scenarios result in multiple IPv6 addresses per device, as
opposed to the IPv4 constricting scenarios of multiple devices
sharing a scarce global address.
4.7 Multihoming and renumbering
Multihoming and renumbering remain technically challenging with IPv6
(see the Gap Analysis below). However, IPv6 was designed to allow
sites and hosts to run with several simultaneous CIDR-like prefixes
and thus with several simultaneous ISPs. An address selection
mechanism [12] is specified so that hosts will behave consistently
when several addresses are simultaneously valid. The fundamental
difficulty that IPv4 has in this regard therefore does not apply to
IPv6. IPv6 sites can and do run today with multiple ISPs active, and
the processes for adding and removing active prefixes at a site have
been documented [15] and [19].
The IPv6 address space allocated by the ISP will be dependent upon
the connecting Service provider. This may result in a renumbering
effort if the network changes from Service Provider. When changing
ISPs or ISPs readjusting their addressing pool, DHCP-PD [13] can be
used as the zero-touch external mechanism for prefix change in
conjunction with a ULA prefix for internal connection stability.
With appropriate management of the lifetime values and overlap of the
external prefixes, a smooth make-before-break transition is possible
as existing communications will continue on the old prefix as long as
it remains valid, while any new communications will use the new
prefix.
5. Case Studies
It is possible to divide the type of networks in different
categories. This can be done on various criteria. The criteria used
within this document are based on the number of components or
connections. For each of these category of networks we can use IPv6
Network Architecture Protection to achieve a secure and flexible
infrastructure, which provides an enhanced network functionality in
comparison with the usage of address translation.
o Medium/large private networks (typically >10 connections)
o Small private networks (typically 1 to 10 connections)
o Single user connection (typically 1 connection)
o ISP/Carrier customer networks
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5.1 Medium/large private networks
Under this category fall the majority of private enterprise networks.
Many of these networks have one or more exit points to the Internet.
Though these organizations have sufficient resources to acquire
addressing independence there are several reasons why they might
choose to use NAT in such a network. For the ISP there is no need to
import the IPv4 address range from the remote end-customer, which
facilitates IPv4 address summarization. The customer can use a
larger IPv4 address range (probably with less-administrative
overhead) by the use of RFC 1918 and NAT. The customer also reduces
the overhead in changing to a new ISP, because the addresses assigned
to devices behind the NAT do not need to be changed when the customer
is assigned a different address by a new ISP. By using address
translation one avoids the need for network renumbering. Finally,
the customer can provide privacy about its hosts and the topology of
its internal network if the internal addresses are mapped through
NAT.
It is expected that there will be enough IPv6 addresses available for
all networks and appliances for the foreseeable future. The basic
IPv6 address-range an ISP allocates for a private network is large
enough (currently /48) for most of the medium and large enterprises,
while for the very large private enterprise networks address-ranges
can be concatenated. A single /48 alloaction provides an enterprise
network with 65536 different /64 prefixes.
The summarization benefit for the ISP is happening based on the IPv6
allocation rules. This means that the ISP will provide the
enterprise with an IPv6 address-range (typically a one or multiple
range(s) of '/48') from its RIR assigned IPv6 address-space. The
goal of this allocation mechanism is to decrease the total amount of
entries in the internet routing table.
To mask the identity of a user on a network of this type, the usage
of IPv6 privacy extensions may be advised. This technique is useful
when an external element wants to track and collect all information
sent and received by a certain host with known IPv6 address. Privacy
extensions add a random factor to the host part of an IPv6 address
and will make it very hard for an external element to keep
correlating the IPv6 address to a host on the inside network. The
usage of IPv6 privacy extensions does not mask the internal network
structure of an enterprise network.
If there is need to mask the internal structure towards the external
IPv6 internet, then some form of 'Untraceable' addresses may be used.
These addresses will be derived from a local pool, and may be
assigned to those hosts for which topology masking is required or
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which want to reach the IPv6 Internet or other external networks.
The technology to assign these addresses to the hosts could be based
on DHCPv6. To complement the 'Untraceable' addresses it is needed to
have at least awareness of the IPv6 address location when routing an
IPv6 packet through the internal network. This could be achieved by
'route-injection' in the network infrastructure. This
route-injection could be done based on /128 host-routes to each
device that wants to connect to the Internet using an untraceable
address. This will provide the most dynamic masking, but will have a
scalability limitation, as an IGP is typically not designed to carry
many thousands of IPv6 prefixes. A large enterprise may have
thousands of hosts willing to connect to the Internet. Less flexible
masking could be to have time-based IPv6 prefixes per link or subnet.
This may reduce the amount of route entries in the IGP by a
significant factor, but has as trade-off that masking is time and
subnet based.
The dynamic allocation of 'Untraceable' addresses can also limit the
IPv6 access between local and external hosts to those local hosts
being authorized for this capability. Dynamically allocated
'Untraceable' addresses may also facilitate and simplify the
connectivity to the outside networks during renumbering, because the
existing IPv6 central address pool could be swapped for the newly
allocated IPv6 address pool.
The use of permanent ULA addresses on a site provides the benefit
that even if an enterprise would change its ISP, the renumbering is
only affecting those devices that have a wish to connect beyond the
site. Internal servers and services would not change their allocated
IPv6 ULA address, and the service would remain available even during
global address renumbering.
5.2 Small private networks
Also known as SOHO (Small Office/Home Office) networks, this
category describes those networks which have few routers in the
topology, and usually have a single network egress point. Typically
these networks are connected via either a dial-up connection or
broadband access; don't have dedicated Network Operation Center
(NOC); and through economic pressure are typically forced today to
use NAT. In most cases the received global IPv4 prefix is not fixed
over time and is too long to provide every node in the private
network with a unique globally usable address. Fixing either of
those issues typically adds an administrative overhead for address
management to the user. This category may even be limited to
receiving ambiguous IPv4 addresses from the service provider based on
RFC 1918. An ISP will typically pass along the higher administration
cost attached to larger address blocks, or IPv4 prefixes that are
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static over time, due to the larger public address pool each of those
requires.
As a direct response to explicit charges per public address most of
this category has deployed NAPT (port demultiplexing NAT) to minimize
the number of addresses in use. Unfortunately this also limits the
Internet capability of the equipment to being mainly a receiver of
Internet data (client), and makes it quite hard for the equipment to
become a world wide Internet server (i.e. HTTP, FTP, etc.) due to
the stateful operation of the NAT equipment. Even when there is
sufficient technical knowledge to manage the NAT to enable a server,
only one server of any given protocol type is possible per address,
and then only when the address from the ISP is public.
When deploying IPv6 NAP in this environment, there are two approaches
possible with respect to IPv6 addressing.
o DHCPv6 Prefix-Delegation
o ISP provides a static IPv6 address-range
For the DHCPv6-PD solution, a dynamic address allocation approach
is chosen. By means of the enhanced DHCPv6 protocol it is possible
to have the ISP push down an IPv6 prefix range automatically towards
the small private network and populate all interfaces in that small
private network dynamically. This reduces the burden for
administrative overhead because everything happens automatically.
For the static configuration the mechanisms used could be the
same as for the medium/large enterprises. Typically the need for
masking the topology will not be of high priority for these users,
and the usage of IPv6 privacy extensions could be sufficient.
For both alternatives the ISP has the unrestricted capability for
summarization of its RIR allocated IPv6 prefix, while the small
private network administrator has all flexibility in using the
received IPv6 prefix to its advantage because it will be of
sufficient size to allow all the local nodes to have a public address
and full range of ports available whenever necessary.
While a full prefix is expected to be the primary deployment model
there may be cases where the ISP provides a single IPv6 address for
use on a single piece of equipment (PC, PDA, etc.). This is expected
to be rare though, because in the IPv6 world the assumption is that
there is an unrestricted availability of a large amount of globally
routable and unique address space. If scarcity was the motivation
with IPv4 to provide RFC 1918 addresses, in this environment the ISP
will not be motivated to allocate private addresses towards the
single user connection because there are enough global addresses
available at essentially the same cost. Also if the single device
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wants to mask its identity to the called party or its attack profile
over a short time window it will need to enable IPv6 privacy
extensions, which in turn leads to the need for a minimum allocation
of a /64 prefix rather than a single address.
5.3 Single user connection
This group identifies the users which are connected via a single IPv4
address and use a single piece of equipment (PC, PDA, etc.). This
user may get an ambiguous IPv4 address (frequently imposed by the
ISP) from the service provider which is based on RFC 1918. If
ambiguous addressing is utilized, the service provider will execute
NAT on the allocated IPv4 address for global Internet connectivity.
This also limits the internet capability of the equipment to being
mainly a receiver of Internet data, and makes it quite hard for the
equipment to become a world wide internet server (i.e. HTTP, FTP,
etc.) due to the stateful operation of the NAT equipment.
When using IPv6 NAP, this group will identify the users which are
connected via a single IPv6 address and use a single piece of
equipment (PC, PDA, etc.).
In IPv6 world the assumption is that there is unrestricted
availability of a large amount of globally routable and unique IPv6
addresses. The ISP will not be motivated to allocate private
addresses towards the single user connection because he has enough
global addresses available, if scarcity was the motivation with IPv4
to provide RFC 1918 addresses. If the single user wants to mask his
identity, he may choose to enable IPv6 privacy extensions.
5.4 ISP/Carrier customer networks
This group refers to the actual service providers that are providing
the IPv4 access and transport services. They tend to have three
separate IPv4 domains that they support:
o For the first they fall into the Medium/large private networks
category (above) for their own internal networks, LANs etc.
o The second is the Operations network which addresses their
backbone and access switches, and other hardware, this is separate
for both engineering reasons as well as simplicity in managing the
security of the backbone.
o The third is the IP addresses (single or blocks) that they assign
to customers. These can be registered addresses (usually given to
category a and b and sometimes c) or can be from a pool of RFC
1918 addresses used with NAT for single user connections.
Therefore they can actually have two different NAT domains that
are not connected (internal LAN and single user customers).
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When IPv6 NAP is utilized in these three domains then for the first
category it will be possible to use the same solutions as described
in chapter 5.1. The second domain of the ISP/carrier is the
Operations network. This environment tends to be a closed
environment, and consequently intra- communication can be done based
on ULA addresses. This would give a stable configuration with
respect to a local IPv6 address plan. Using these local scope
addresses would also prevent from being accessed from the external
network. The third is the IPv6 addresses that ISP/carrier network
assign to customers. These will typically be assigned with prefix
lengths terminating on nibble boundaries to be consistent with the
DNS PTR records. As scarcity of IPv6 addresses is not a concern, it
will be possible for the ISP to provide global routable IPv6 prefixes
without a requirement for address translation. An ISP may for
commercial reasons still decide to restrict the capabilities of the
end users by other means like traffic and/or route filtering etc.
If the carrier network is a mobile provider, then IPv6 is encouraged
in comparison with the combination of IPv4+NAT for 3GPP attached
devices. When looking in chapter 2.3 of RFC3314 'Recommendations for
IPv6 in 3GPP Standards September 2002' [9] it is found that the IPv6
WG recommends that one or more /64 prefixes should be assigned to
each primary PDP context. This will allow sufficient address space
for a 3GPP-attached node to allocate privacy addresses and/or route
to a multi-link subnet, and will discourage the use of NAT within
3GPP-attached devices.
6. IPv6 gap analysis
Like IPv4 and any major standards effort, IPv6 standardization
work continues as deployments are ongoing. This section discusses
several topics for which additional standardization, or documentation
of best practice, is required to fully realize the benefits of NAP.
None of these items are show-stoppers for immediate usage of NAP in
roles where there are no current gaps.
6.1 Completion of work on ULAs
As noted above, a new form of Unique Local IPv6 Unicast Addresses
(ULAs) is being standardized by the IETF. Experience to date has
shown that most network managers want to gain some operational
familiarity with IPv6 in their local environment before exposing
their network to the live global Internet. Since these addresses
allow autonomy for local deployment of IPv6 in private networks, this
work should be completed as soon as possible. In addition to
autonomy the routing limitation of ULA addresses protects nodes that
are only for local use from global exposure.
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6.2 Subnet topology masking
There really is no functional gap here as a centrally assigned
pool of addresses in combination with host routes in the IGP is an
effective way to mask topology. If necessary a best practice
document could be developed describing the interaction between DHCP
and various IGPs which would in effect define Untraceable Addresses.
As an alternative some work in Mobile IP to define a policy
message where a mobile node would learn from the home agent that it
should not even try to inform its correspondent about route
optimization (and thereby expose its real location) would allow a
border home agent using internal tunneling to the logically mobile
node (potentially rack mounted) to completely mask all internal
topology while avoiding the strain from a large number of host routes
in the IGP. This work should be pursued in the IETF.
6.3 Minimal traceability of privacy addresses
Privacy addresses (RFC 3041) may certainly be used to limit the
traceability of external traffic flows back to specific hosts, but
lacking a topology masking component above they would still reveal
the subnet address bits. For complete privacy a best practice
document describing the combination of privacy addresses with
topology masking is required. This work remains to be done, and
should be pursued by the IETF.
6.4 Renumbering procedure
Documentation of site renumbering procedures [15] should be
completed. It should also be noticed that ULAs will help here too,
since a change of ISP prefix will only affect hosts that need an
externally routeable address as well as a ULA.
6.5 Site multihoming
This complex problem has never been well solved for IPv4, which is
exactly why NAT has been used as a partial solution. For IPv6, after
several years' work, the relevant IETF WG is finally converging on an
architectural approach intended to reconcile enterprise and ISP
perspectives. Again, ULAs will help since they will provide stable
addressing for internal communications that are not affected by
multihoming.
6.6 Untraceable addresses
The details of the untraceable addresses, along with any associated
mechanisms such as route injection, must be worked out and specified.
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7. IANA Considerations
This document requests no action by IANA
8. Security Considerations
While issues which are potentially security related are discussed
throughout the document, the approaches herein do not introduce any
new security concerns. Product marketing departments have widely
sold IPv4 NAT as a security tool, though the misleading nature of
those claims has been previously documented in RFC 2663 [3] and RFC
2993 [5].
This document defines IPv6 approaches which collectively achieve
the goals of the network manager without the negative impact on
applications or security that are inherent in a NAT approach. To the
degree that these techniques improve a network manager's ability to
explicitly know about or control access, and thereby manage the
overall attack exposure of local resources, they act to improve local
network security. In particular the explicit nature of a content
aware firewall in NAP will be a vast security improvement over the
NAT artifact where lack of translation state has been widely sold as
a form of protection.
9. Conclusion
This document has described a number of techniques that may be
combined on an IPv6 site to protect the integrity of its network
architecture. These techniques, known collectively as Network
Architecture Protection, retain the concept of a well defined
boundary between "inside" and "outside" the private network, and
allow firewalling, topology hiding, and privacy. However, because
they preserve address transparency where it is needed, they achieve
these goals without the disadvantage of address translation. Thus,
Network Architecture Protection in IPv6 can provide the benefits of
IPv4 Network Address Translation without the corresponding
disadvantages.
The document has also identified a few ongoing IETF work items that
are needed to realize 100% of the benefits of NAP.
10. Acknowledgements
Christian Huitema has contributed during the initial round table to
discuss the scope and goal of the document, while the European Union
IST 6NET project acted as a catalyst for the work documented in this
draft. Editorial comments and contributions have been received from:
Fred Templin, Chao Luo, Pekka Savola, Tim Chown, Jeroen Massar,
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Salman Asadullah, Patrick Grossetete and other members of the v6ops
WG.
11. References
11.1 Normative References
11.2 Informative References
[1] Fuller, V., Li, T., Yu, J. and K. Varadhan, "Classless
Inter-Domain Routing (CIDR): an Address Assignment and
Aggregation Strategy", RFC 1519, September 1993.
[2] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and E.
Lear, "Address Allocation for Private Internets", BCP 5,
RFC 1918, February 1996.
[3] Srisuresh, P. and M. Holdrege, "IP Network Address Translator
(NAT) Terminology and Considerations", RFC 2663, August 1999.
[4] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[5] Hain, T., "Architectural Implications of NAT", RFC 2993,
November 2000.
[6] Srisuresh, P. and K. Egevang, "Traditional IP Network Address
Translator (Traditional NAT)", RFC 3022, January 2001.
[7] Holdrege, M. and P. Srisuresh, "Protocol Complications with the
IP Network Address Translator", RFC 3027, January 2001.
[8] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[9] Wasserman, M., "Recommendations for IPv6 in Third Generation
Partnership Project (3GPP) Standards", RFC 3314, September
2002.
[10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[11] Bush, R., Durand, A., Fink, B., Gudmundsson, O. and T. Hain,
"Representing Internet Protocol version 6 (IPv6) Addresses in
the Domain Name System (DNS)", RFC 3363, August 2002.
[12] Draves, R., "Default Address Selection for Internet Protocol
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version 6 (IPv6)", RFC 3484, February 2003.
[13] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
Configuration Protocol (DHCP) version 6", RFC 3633, December
2003.
[14] Savola, P. and B. Haberman, "Embedding the Rendezvous Point
(RP) Address in an IPv6 Multicast Address", RFC 3956, November
2004.
[15] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering
an IPv6 Network without a Flag Day",
Internet-Draft draft-ietf-v6ops-renumbering-procedure-03,
November 2004.
[16] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses",
Internet-Draft draft-ietf-ipv6-unique-local-addr-08, November
2004.
[17] Dupont, F. and P. Savola, "RFC 3041 Considered Harmful
(draft-dupont-ipv6- rfc3041harmful-05.txt)", June 2004.
[18] Chown, T., "IPv6 Implications for TCP/UDP Port Scanning
(chown-v6ops- port-scanning-implications-01.txt)", July 2004.
[19] Chown, T., Tompson, M. and A. Ford, "Things to think about when
Renumbering an IPv6 network
(draft-chown-v6ops-renumber-thinkabout-00)", October 2004.
Authors' Addresses
Gunter Van de Velde
Cisco Systems
De Kleetlaan 6a
Diegem 1831
Belgium
Phone: +32 2704 5473
Email: gunter@cisco.com
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Tony Hain
Cisco Systems
500 108th Ave. NE
Bellevue, Wa.
USA
Email: alh-ietf@tndh.net
Ralph Droms
Cisco Systems
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: rdroms@cisco.com
Brian Carpenter
IBM Corporation
Sauemerstrasse 4
Rueschlikon, 8803
Switzerland
Email: brc@zurich.ibm.com
Eric Klein
TTI Telecom
Petach Tikvah,
Israel
Phone: +972 3 926-9130
Email: erick@tti-telecom.com
Appendix A. Additional benefits due to Native IPv6 and universal unique
addressing
The users of native IPv6 technology and global unique IPv6 addresses
have the potential to make use of the enhanced IPv6 capabilities, in
addition to the benefits offered by the IPv4 technology.
A.1 Universal any-to-any connectivity
One of the original design points of the Internet was any-to-any
connectivity. The dramatic growth of Internet connected systems
coupled with the limited address space of the IPv4 protocol spawned
address conservation techniques. NAT was introduced as a tool to
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reduce demand on the limited IPv4 address pool, but the side effect
of the NAT technology was to remove the any-to-any connectivity
capability. By removing the need for address conservation (and
therefore NAT), IPv6 returns the any-to-any connectivity model and
removes the limitations on application developers. With the freedom
to innovate unconstrained by NAT traversal efforts, developers will
be able to focus on new advanced network services (i.e. peer-to-peer
applications, IPv6 embedded IPsec communication between two
communicating devices, instant messaging, Internet telephony, etc..)
rather than focusing on discovering and traversing the increasingly
complex NAT environment.
It will also allow application and service developers to rethink the
security model involved with any-to-any connectivity, as the current
edge firewall solution in IPv4 may not be sufficient for Any-to-any
service models.
A.2 Auto-configuration
IPv6 offers a scalable approach to minimizing human interaction and
device configuration. Whereas IPv4 implementations require touching
each end system to indicate the use of DHCP vs. a static address and
management of a server with the pool size large enough for the
potential number of connected devices, IPv6 uses an indication from
the router to instruct the end systems to use DHCP or the stateless
auto configuration approach supporting a virtually limitless number
of devices on the subnet. This minimizes the number of systems that
require human interaction as well as improves consistency between all
the systems on a subnet. In the case that there is no router to
provide this indication, an address for use on the local link only
will be derived from the interface media layer address.
A.3 Native Multicast services
Multicast services in IPv4 were severely restricted by the limited
address space available to use for group assignments and an implicit
locally defined range for group membership. IPv6 multicast corrects
this situation by embedding explicit scope indications as well as
expanding to 4 billion groups per scope. In the source specific
multicast case, this is further expanded to 4 billion groups per
scope per subnet by embedding the 64 bits of subnet identifier into
the multicast address.
IPv6 allows also for innovative usage of the IPv6 address length, and
makes it possible to embed the multicast 'Rendez-Vous Point' (or RP)
[14] directly in the IPv6 multicast address when using ASM multicast.
this is not possible with limited size of the IPv4 address. This
approach also simplifies the multicast model considerably, making it
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easier to understand and deploy.
A.4 Increased security protection
The security protection offered by native IPv6 technology is more
advanced than IPv4 technology. There are various transport
mechanisms enhanced to allow a network to operate more securely with
less performance impact:
o IPv6 has the IPsec technology directly embedded into the IPv6
protocol. This allows for simpler peer-to-peer encryption and
authentication, once a simple key/trust management model is
developed, while the usage of some other less secure mechanisms is
avoided (i.e. md5 password hash for neighbor authentication).
o On a local network, any user will have more security awareness.
This awareness will motivate the usage of simple firewall
applications/devices to be inserted on the border between the
external network and the local (or home network) as there is no
Address Translater and hance no false safety perception.
o All flows on the Internet will be better traceable due to a unique
and globally routable source and destination IPv6 address. This
may facilitate an easier methodology for back-tracing DoS attacks
and avoid illegal access to network resources by simpler traffic
filtering.
o The usage of private address-space in IPv6 is now provided by
Unique Local Addresses, which will avoid conflict situations when
merging networks and securing the internal communication on a
local network infrastructure due to simpler traffic filtering
policy.
o The technology to enable source-routing on a network
infrastructure has been enhanced to allow this feature to
function, without impacting the processing power of intermediate
network devices. The only devices impacted with the
source-routing will be the source and destination node and the
intermediate source-routed nodes. This impact behavior is
different if IPv4 is used, because then all intermediate devices
would have had to look into the source-route header.
A.5 Mobility
Anytime, anywhere, universal access requires MIPv6 services in
support of mobile nodes. While a Home Agent is required for initial
connection establishment in either protocol version, IPv6 mobile
nodes are able to optimize the path between them using the MIPv6
option header while IPv4 mobile nodes are required to triangle route
all packets. In general terms this will minimize the network
resources used and maximize the quality of the communication.
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A.6 Merging networks
When two IPv4 networks want to merge it is not guaranteed that both
networks would be using different address-ranges on some parts of the
network infrastructure due to the legitimate usage of RFC 1918
private addressing. This potential overlap in address space may
complicate a merge of two and more networks dramatically due to the
additional IPv4 renumbering effort. i.e. when the first network has
a service running (NTP, DNS, DHCP, HTTP, etc..) which need to be
accessed by the 2nd merging network. Similar address conflicts can
happen when two network devices from these merging networks want to
communicate.
With the usage of IPv6 the addressing overlap will not exist because
of the existence of the Unique Local Address usage for private and
local addressing.
A.7 Community of interest
Although some Internet-enabled devices will function as fully-fledged
Internet hosts, it is believed that many will be operated in a highly
restricted manner functioning largely or entirely within a Community
of Interest. By Community of Interest we mean a collection of hosts
that are logically part of a group reflecting their ownership or
function. Typically, members of a Community of Interest need to
communicate within the community but should not be generally
accessible on the Internet. They want the benefits of the
connectivity provided by the Internet, but do not want to be exposed
to the rest of the world. This functionality will be available
through the usage of NAP and native IPv6 dataflows, without any
stateful device in the middle. It will also allow to build virtual
organization networks on the fly, which is very difficult to do in
IPv4+NAT scenarios.
Appendix B. Revision history
B.1 Changes from *-nap-00 to *-nap-01
o Document introduction has been revised and overview table added
o Comments and suggestions from nap-00 draft have been included.
o Initial section of -00 draft 2.6 and 4.6 have been aggregated into
a new æcase studyÆ section 5.
o The list of additional IPv6 benefits has been been placed into
appendix.
o new security considerations section added.
o GAP analysis revised.
o Section 2.6 and 4.6 have been included.
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