5221
INFORMATIONAL
Requirements for Address Selection Mechanisms
Authors: A. Matsumoto, T. Fujisaki, R. Hiromi, K. Kanayama
Date: July 2008
Area: ops
Working Group: v6ops
Stream: IETF
Abstract
There are some problematic cases when using the default address selection mechanism that RFC 3484 defines. This document describes additional requirements that operate with RFC 3484 to solve the problems. This memo provides information for the Internet community.
RFC 5221
INFORMATIONAL
Network Working Group A. Matsumoto
Request for Comments: 5221 T. Fujisaki
Category: Informational NTT
R. Hiromi
Intec NetCore
K. Kanayama
INTEC Systems
July 2008
<span class="h1">Requirements for Address Selection Mechanisms</span>
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Abstract
There are some problematic cases when using the default address
selection mechanism that <a href="./rfc3484">RFC 3484</a> defines. This document describes
additional requirements that operate with <a href="./rfc3484">RFC 3484</a> to solve the
problems.
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-2">2</a>. Requirements of Address Selection ...............................<a href="#page-2">2</a>
<a href="#section-2.1">2.1</a>. Effectiveness ..............................................<a href="#page-2">2</a>
<a href="#section-2.2">2.2</a>. Timing .....................................................<a href="#page-2">2</a>
<a href="#section-2.3">2.3</a>. Dynamic Behavior Update ....................................<a href="#page-3">3</a>
<a href="#section-2.4">2.4</a>. Node-Specific Behavior .....................................<a href="#page-3">3</a>
<a href="#section-2.5">2.5</a>. Application-Specific Behavior ..............................<a href="#page-3">3</a>
<a href="#section-2.6">2.6</a>. Multiple Interface .........................................<a href="#page-3">3</a>
<a href="#section-2.7">2.7</a>. Central Control ............................................<a href="#page-3">3</a>
<a href="#section-2.8">2.8</a>. Next-Hop Selection .........................................<a href="#page-3">3</a>
<a href="#section-2.9">2.9</a>. Compatibility with <a href="./rfc3493">RFC 3493</a> ................................<a href="#page-4">4</a>
<a href="#section-2.10">2.10</a>. Compatibility and Interoperability with <a href="./rfc3484">RFC 3484</a> ..........<a href="#page-4">4</a>
<a href="#section-2.11">2.11</a>. Security ..................................................<a href="#page-4">4</a>
<a href="#section-3">3</a>. Security Considerations .........................................<a href="#page-4">4</a>
3.1. List of Threats Introduced by New Address-Selection
Mechanism ..................................................<a href="#page-4">4</a>
3.2. List of Recommendations in Which Security Mechanism
Should Be Applied ..........................................<a href="#page-5">5</a>
<a href="#section-4">4</a>. Normative References ............................................<a href="#page-5">5</a>
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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
Today, the <a href="./rfc3484">RFC 3484</a> [<a href="./rfc3484" title=""Default Address Selection for Internet Protocol version 6 (IPv6)"">RFC3484</a>] mechanism is widely implemented in
major OSs. However, in many sites, the default address-selection
rules are not appropriate, and cause a communication failure. The
problem statement (PS) document [<a href="./rfc5220" title=""Problem Statement for Default Address Selection in Multi-Prefix Environments: Operational Issues of RFC 3484 Default Rules"">RFC5220</a>] lists problematic cases
that resulted from incorrect address selection.
Though <a href="./rfc3484">RFC 3484</a> made the address-selection behavior of a host
configurable, typical users cannot make use of that because of the
complexity of the mechanism and lack of knowledge about their network
topologies. Therefore, an address-selection autoconfiguration
mechanism is necessary, especially for unmanaged hosts of typical
users.
This document contains requirements for address-selection mechanisms
that enable hosts to perform appropriate address selection
automatically.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Requirements of Address Selection</span>
Address-selection mechanisms have to fulfill the following eleven
requirements.
<span class="h3"><a class="selflink" id="section-2.1" href="#section-2.1">2.1</a>. Effectiveness</span>
The mechanism can modify <a href="./rfc3484">RFC 3484</a> default address-selection behavior
at nodes. As documented in the PS [<a href="./rfc5220" title=""Problem Statement for Default Address Selection in Multi-Prefix Environments: Operational Issues of RFC 3484 Default Rules"">RFC5220</a>], the default rules
defined in <a href="./rfc3484">RFC 3484</a> do not work properly in some environments.
Therefore, the mechanism has to be able to modify the address-
selection behavior of a host and to solve the problematic cases
described in the PS document.
<span class="h3"><a class="selflink" id="section-2.2" href="#section-2.2">2.2</a>. Timing</span>
Nodes can perform appropriate address selection when they select
addresses.
If nodes need to have address-selection information to perform
appropriate address selection, then the mechanism has to provide a
function for nodes to obtain the necessary information beforehand.
The mechanism should not degrade usability. The mechanism should not
enforce long address-selection processing time upon users.
Therefore, forcing every consumer user to manipulate the address-
selection policy table is usually not an acceptable solution. So, in
this case, some kind of autoconfiguration mechanism is desirable.
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<span class="h3"><a class="selflink" id="section-2.3" href="#section-2.3">2.3</a>. Dynamic Behavior Update</span>
The address-selection behavior of nodes can be dynamically updated.
When the network structure changes and the address-selection behavior
has to be changed accordingly, a network administrator can modify the
address-selection behavior of nodes.
<span class="h3"><a class="selflink" id="section-2.4" href="#section-2.4">2.4</a>. Node-Specific Behavior</span>
The mechanism can support node-specific address-selection behavior.
Even when multiple nodes are on the same subnet, the mechanism should
be able to provide a method for the network administrator to make
nodes behave differently. For example, each node may have a
different set of assigned prefixes. In such a case, the appropriate
address-selection behavior may be different.
<span class="h3"><a class="selflink" id="section-2.5" href="#section-2.5">2.5</a>. Application-Specific Behavior</span>
The mechanism can support application-specific address-selection
behavior or combined use with an application-specific address-
selection mechanism such as address-selection APIs.
<span class="h3"><a class="selflink" id="section-2.6" href="#section-2.6">2.6</a>. Multiple Interface</span>
The mechanism can support those nodes equipped with multiple
interfaces. The mechanism has to assume that nodes have multiple
interfaces and makes address selection of those nodes work
appropriately.
<span class="h3"><a class="selflink" id="section-2.7" href="#section-2.7">2.7</a>. Central Control</span>
The address-selection behavior of nodes can be centrally controlled.
A site administrator or a service provider could determine or could
have an effect on the address-selection behavior at their users'
hosts.
<span class="h3"><a class="selflink" id="section-2.8" href="#section-2.8">2.8</a>. Next-Hop Selection</span>
The mechanism can control next-hop-selection behavior at hosts or
cooperate with other routing mechanisms, such as routing protocols
and <a href="./rfc4191">RFC 4191</a> [<a href="./rfc4191" title=""Default Router Preferences and More-Specific Routes"">RFC4191</a>]. If the address-selection mechanism is used
with a routing mechanism, the two mechanisms have to be able to work
synchronously.
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<span class="h3"><a class="selflink" id="section-2.9" href="#section-2.9">2.9</a>. Compatibility with <a href="./rfc3493">RFC 3493</a></span>
The mechanism can allow an application that uses the basic socket
interface defined in <a href="./rfc3493">RFC 3493</a> [<a href="./rfc3493" title=""Basic Socket Interface Extensions for IPv6"">RFC3493</a>] to work correctly. That is,
with the basic socket interface the application can select
appropriate source and destination addresses and can communicate with
the destination host. This requirement does not necessarily mean
that OS protocol stack and socket libraries should not be changed.
<span class="h3"><a class="selflink" id="section-2.10" href="#section-2.10">2.10</a>. Compatibility and Interoperability with <a href="./rfc3484">RFC 3484</a></span>
The mechanism is compatible with <a href="./rfc3484">RFC 3484</a>. Now that <a href="./rfc3484">RFC 3484</a> is
widely implemented, it is preferable that a new address selection
mechanism does not conflict with the address selection mechanisms
defined in <a href="./rfc3484">RFC 3484</a>.
If the solution mechanism changes or replaces the address-selection
mechanism defined in <a href="./rfc3484">RFC 3484</a>, interoperability has to be retained.
That is, a host with the new solution mechanism and a host with the
mechanism of <a href="./rfc3484">RFC 3484</a> have to be interoperable.
<span class="h3"><a class="selflink" id="section-2.11" href="#section-2.11">2.11</a>. Security</span>
The mechanism works without any security problems. Possible security
threats are described in the Security Considerations section of this
document.
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Security Considerations</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. List of Threats Introduced by New Address-Selection Mechanism</span>
There will be some security incidents when combining the requirements
described in <a href="#section-2">Section 2</a> into a protocol. In particular, there are 3
types of threats: leakage, hijacking, and denial of service.
1. Leakage: Malicious nodes may tap to collect the network policy
information and leak it to unauthorized parties.
2. Hijacking: Nodes may be hijacked by malicious injection of
illegitimate policy information. <a href="./rfc3484">RFC 3484</a> defines both a source
and destination selection algorithm. An attacker able to inject
malicious policy information could redirect packets sent by a
victim node to an intentionally chosen server that would scan the
victim node activities to find vulnerable code. Once vulnerable
code is found, the attacker can take control of the victim node.
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3. Denial of Service: This is an attack on the ability of nodes to
communicate in the absence of the address-selection policy. An
attacker could launch a flooding attack on the controller to
prevent it from delivering the address selection policy
information to nodes, thus preventing those nodes from
appropriately communicating.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. List of Recommendations in Which Security Mechanism Should Be</span>
<span class="h3"> Applied</span>
The address selection mechanism should be afforded security services
listed below. It is preferable that these security services are
afforded via use of existing protocols (e.g., IPsec).
1. Integrity of the network policy information itself and the
messages exchanged in the protocol. This is a countermeasure
against leakage, hijacking, and denial of service.
2. Authentication and authorization of parties involved in the
protocol. This is a countermeasure against Leakage and
Hijacking.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Normative References</span>
[<a id="ref-RFC3484">RFC3484</a>] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", <a href="./rfc3484">RFC 3484</a>, February 2003.
[<a id="ref-RFC3493">RFC3493</a>] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6", <a href="./rfc3493">RFC</a>
<a href="./rfc3493">3493</a>, February 2003.
[<a id="ref-RFC4191">RFC4191</a>] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", <a href="./rfc4191">RFC 4191</a>, November 2005.
[<a id="ref-RFC5220">RFC5220</a>] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,
"Problem Statement for Default Address Selection in
Multi-Prefix Environments: Operational Issues of <a href="./rfc3484">RFC 3484</a>
Default Rules", <a href="./rfc5220">RFC 5220</a>, July 2008.
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Authors' Addresses
Arifumi Matsumoto
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 3334
EMail: [email protected]
Tomohiro Fujisaki
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 7351
EMail: [email protected]
Ruri Hiromi
Intec Netcore, Inc.
Shinsuna 1-3-3
Koto-ku, Tokyo 136-0075
Japan
Phone: +81 3 5665 5069
EMail: [email protected]
Ken-ichi Kanayama
INTEC Systems Institute, Inc.
Shimoshin-machi 5-33
Toyama-shi, Toyama 930-0804
Japan
Phone: +81 76 444 8088
EMail: [email protected]
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