Internet Engineering Task Force Ken Carlberg
INTERNET DRAFT G11
May 14, 2004 Charlie Perkins
Nokia
Requirements for MIPv4 Mobility Agents
Support of Emergency Telecommunication Service
<draft-carlberg-ets-MIP-00.txt>
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Abstract
This document presents a list of requirements for the IPv4 Mobile IP
(MIP) protocol to support Emergency Telecommunications Service (ETS).
1. Introduction
Effective telecommunications capabilities can be imperative to
facilitate immediate recovery operations for serious disaster events,
such as, hurricanes, floods, earthquakes, and attacks by hostile
individuals. Disasters can happen any time, any place, unexpectedly.
Quick response for recovery operations requires immediate access to
any public telecommunications capabilities at hand. These
capabilities include: conventional telephone, cellular phones, and
Internet access (possibly at 802.11 hotspots) via online terminals,
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IP telephones, and wireless PDAs. The commercial telecommunications
infrastructure is rapidly evolving to Internet-based technology.
Therefore, the Internet community should accept the responsibility to
consider how it can best support emergency management and recovery
operations.
Emergency Telecommunications Service (ETS) involves authorized access
and use of services (i.e., resources) set aside for users involved in
disaster response or recovery. The manner in which these resources
are identified and allocated for ETS users is outside the scope of
this document.
A general set of requirements for ETS has been defined in [2], and is
meant to act as a baseline for future and more specific requirements.
The requirements presented in section 3 below represent an extension
to [2] and are aimed at the mobility agents specified in the Mobile
IP (MIP) protocol [3].
Note, all references to MIP in this document refer to the IPv4
version of the protocol. However, similar considerations can be
expected to be applied for IPv6 MIP whenever the appropriate access
control points are able to be identified. For IPv4, it is easy to
specify the foreign agent as the requisite control point.
2. Mobile IP
MIP is used to support a mobile host that operates in either its home
or in foreign networks. These networks have mobility agents,
designated as either foreign agents or home agents, that forward
traffic between the mobile device and correspondent hosts. Agent
Discovery involves an exchange of messages (Agent Advertisements)
that allow the mobile host to determine whether it is connected
within its home domain or in a foreign network. This discovery
process also indicates if the host has moved to a different IP
network.
Beyond the discovery of other MIP nodes and movement, Agent
Advertisements are used by mobility agents to advertise services on a
link. These messages are sent as an extension of the ICMP Router
Advertisement. The Mobility Agent Advertisement Extension message is
an example of the extentions defined in MIP and is used to convey one
of several services that are offered by the node -- such as "this
node is a Home Agent and/or Foreign Agent". Of particular importance
to this document is that this extension may indicate that the Foreign
Agent is BUSY and will not accept registrations from additional
mobile nodes.
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The existance of a busy condition implies that a threshold exists
that prevents any additional registrations to be accepted by that
mobility agent. During times of disasters, a need may arise to allow
mobile users involved in disaster recovery or response to bypass this
"busy" condition. This function, and the requirements of how it is
accomplished, is the concern of this document. The precise manner in
which this bypass is accomplished with respect to conveying existing
and requested service is outside the scope of this document.
However, contraints and references to previous related RFCs with
respect to security are listed.
3. Requirements
We divide the set of requirements into two subgroups. The first
involves the list of requirements concerning the advertisement of ETS
support and the request/registration of that service. The second set
of requirements pertain to security and the authorization &
authentication features needed by the system to ensure that the
correct set of users are enabled to obtain their desired service.
3.1 Conveying ETS Information
The requirements below pertain to those entities that choose to
support ETS type users. For those that choose not to provide this
support users, either because of legacy implementations of [3] or
because of lack of configuration, the following do not apply.
3.1.1 Mobility Agent Indicates ETS Support
In order for mobile hosts to determine if ETS type users are
supported, mobility agents are required to be able to advertise this
service and therefore distinguish themselves from other mobility
agents.
3.1.2 Form of ETS Advertisement by Mobility Agent
The advertisement of ETS support by mobility agents can either be a
binary indicator, or a more descriptive format that identifies the
sets of ETS users supported by that agent. Tradeoffs regarding
scarcity of unreserved fields in existing MIP messages versus
significant changes to MIP deserve close consideration.
3.1.3 Role of Mobility Agents
Mobility Agents may support non-ETS users at the same time as
providing support for ETS users.
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3.1.4 Mobile Host Requesting ETS Support
If a mobile host needs to use an ETS capable mobility agent, the
means by which a mobile host obtains that service has to be specified
-- this is particularly important when mobile agents support for ETS
and non-ETS users. This is likely to involve defining a new message
format that explicitly signals the requested service, but it may also
involve others means of identification.
3.1.5 Preemption
Mobility agents that provide ETS support may preempt (or even
terminate) existing registrations of non-ETS users in favor of ETS
users. This action is subject to local policies of that agent.
Refer to [2] for additional insight in the role of policies with
respect to ETS.
3.2 Security Requirements
The operation of ETS is expected to introduce certain security
requirements, which are mentioned in this section.
3.2.1 MIP AAA compatibility
Solutions are expected to remain compatible with the MIP AAA
requirements document of RFC 2977[4].
3.2.2 Foreign agent operation
Foreign agents are required to be able to check that a mobile device
is authorized to use ETS. Otherwise, arbitrary mobile devices could
routinely obtain services for applications that have no requirement
for emergency services.
4. Security Considerations
If a foreign agent does not protect against unauthorized invocation
of ETS features, the danger exists that the additional resources
required would be unavailable in the case of real need. Moreover, a
malicious node would typically target ETS to disable the delivery of
needed support in conflict situations. Vulnerability to such attacks
should be minimized.
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5. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 Carlberg, K., Atkinson, R., "General Requirements for Emergency
Telecommunication Service (ETS)", RFC 3689, February 2004
3 Perkins, C., ed., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
4 Glass, S., et. al, "Mobile IP Authentication, Authorization,
and Accounting Requirements", RFC 2977, October 2000
6. Author's Addresses
Ken Carlberg Charlie Perkins
G11 Communications Systems Laboratory
123a Versailles Circle Nokia Research Center
Baltimore, MD 313 Fairchild Drive
USA Mountain View, CA 94303
USA
carlberg@g11.org.uk Charles.Perkins@nokia.com
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