Network Working Group J. Kempf
Request for Comments: 3154 C. Castelluccia
Category: Informational P. Mutaf
N. Nakajima
Y. Ohba
R. Ramjee
Y. Saifullah
B. Sarikaya
X. Xu
August 2001
Requirements and Functional Architecture for
an IP Host Alerting Protocol
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.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document develops an architecture and a set of requirements
needed to support alerting of hosts that are in dormant mode. The
architecture and requirements are designed to guide development of an
IP protocol for alerting dormant IP mobile hosts, commonly called
paging.
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Table of Contents
1. Introduction ...................................................3
2. Terminology ....................................................3
3. Security Considerations ........................................3
3.1. DoS Amplification .........................................3
3.2. Queue Overflow ............................................4
3.3. Selective DoS against Hosts ...............................4
4. Requirements ...................................................5
4.1. Impact on Power Consumption ...............................5
4.2. Scalability ...............................................5
4.3. Control of Broadcast/Multicast/Anycast ....................5
4.4. Efficient Signaling for Inactive Mode .....................6
4.5. No Routers ................................................6
4.6. Multiple Dormant Modes ....................................6
4.7. Independence of Mobility Protocol .........................6
4.8. Support for Existing Mobility Protocols ...................6
4.9. Dormant Mode Termination ..................................6
4.10. Network Updates ...........................................6
4.11. Efficient Utilization of L2 ...............................7
4.12. Orthogonality of Paging Area and Subnets ..................7
4.13. Future L3 Paging Support ..................................7
4.14. Robustness Against Failure of Network Elements ............7
4.15. Reliability of Packet Delivery ............................7
4.16. Robustness Against Message Loss ...........................7
4.17. Flexibility of Administration .............................7
4.18. Flexibility of Paging Area Design .........................8
4.19. Availability of Security Support ..........................8
4.20. Authentication of Paging Location Registration ............8
4.21. Authentication of Paging Area Information .................8
4.22. Authentication of Paging Messages .........................8
4.23. Paging Volume .............................................8
4.24. Parsimonious Security Messaging ...........................8
4.25. Noninterference with Host's Security Policy ...............8
4.26. Noninterference with End-to-end Security ..................9
4.27. Detection of Bogus Correspondent Nodes ....................9
5. Functional Architecture ........................................9
5.1. Functional Entities .......................................9
5.2. Interfaces ...............................................10
5.3. Functional Architecture Diagram ..........................12
6. Acknowledgements ..............................................12
7. References ....................................................13
8. Authors' Addresses ............................................13
9. Full Copyright Statement ......................................16
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1. Introduction
In [1], a problem statement was developed to explain why an IP
protocol was desirable for alerting hosts in dormant mode, commonly
called paging. In this document, a set of requirements is developed
for guiding the development of an IP paging protocol. Based on the
requirements, an architecture is developed to represent the
functional relationships between logical functional entities
involved.
2. Terminology
Please see [1] for definition of terms used in describing paging. In
addition, this document defines the following terms:
Wide Casting - Either broadcasting or multicasting.
Inactive Mode - The host is no longer listening for any
packets, not even periodically, and not sending packets. The
host may be in a powered off state, it may have shut down all
interfaces to drastically conserve power, or it may be out of
range of a radio access point.
3. Security Considerations
An IP paging protocol introduces new security issues. In this
section, security issues with relevance to formulating requirements
for an IP paging protocol are discussed.
3.1. DoS Amplification
A DoS (Denial-of-Service) or DDoS (Distributed DoS) attack generally
consists of flooding a target network with bogus IP packets in order
to cause degraded network performance at victim nodes and/or routers.
Performance can be degraded to the point that the network cannot be
used. Currently, there is no preventive solution against these
attacks, and the impacts can be very important.
In general a DoS attacker profits from a so-called "amplifier" in
order to increase the damage caused by his attack. Paging can serve
for an attacker as a DoS amplifier.
An attacker (a malicious correspondent node) can send large numbers
of packets pretending to be sent from different (bogus) correspondent
nodes and destined for large numbers of hosts in inactive and dormant
modes. This attack, in turn, will be amplified by the paging agent
which wide casts paging messages over a paging area, resulting in
more than one networks being flooded. Clearly, the damage can be
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more important in wireless networks that already suffer from scarce
radio bandwidth.
Alternatively, an attacker can sort out a host which:
1. sends periodic messages declaring that it is in dormant mode,
2. never replies to paging requests.
Such a node may be the attacker's node itself, or a second node
participating in the attack.
That node is never in inactive mode because of behavior 1 above. In
this case, the attacker can send large numbers of packets destined
for that host which periodically declares that it is in dormant mode
but never replies to paging messages. The impact will be the same as
above however in this case the attack will be amplified indefinitely.
3.2. Queue Overflow
For reliability reasons, the paging protocol may need to make
provisions for a paging queue where a paging request is buffered
until the requested host replies by sending a location registration
message.
An attacker can exploit that by sending large numbers of packets
having different (bogus) correspondent node addresses and destined
for one or more inactive hosts. These packets will be buffered in
the paging queue. However, since the hosts are inactive, the paging
queue may quickly overflow, blocking the incoming traffic from
legitimate correspondent nodes. As a result, all registered dormant
hosts may be inaccessible for a while. The attacker can re-launch
the attack in a continuous fashion.
An attacker together with a bogus host that fails to respond to pages
can overflow the buffering provided to hold packets for dormant mode
hosts. If the attacker keeps sending packets while the dormant mode
host fails to reply, the buffer can overflow.
3.3. Selective DoS against Hosts
The following vulnerabilities already exist in the absence of IP
paging. However, they are included here since they can affect the
correct operation of the IP paging protocol.
These vulnerabilities can be exploited by an attacker in order to
eliminate a particular host. This, in turn, can be used by an
attacker as a stepping stone to launch other attacks.
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Forced Battery Consumption
An attacker can frequently send packets to a host in order to prevent
that host from switching to dormant mode. As a result the host may
quickly run out of battery.
Bogus Paging Areas
An attacker can periodically emit malicious packets in order to
confuse one or more hosts about their actual locations. Currently,
there is no efficient way to authenticate such packets.
In the case of IP paging, these packets may also contain bogus paging
area information. Upon receipt of such a packet, a host may move and
send a location registration message pointing to a non-existing or
wrong paging area. The functional entities of the IP paging protocol
may loose contact with the host.
More importantly, this attack can serve for sorting out a host which
shows the behaviors 1 and 2 described in Section 3.1.
Bogus Paging Agents
An attacker can wide cast fake paging messages pretending to be sent
by a paging agent. The impacts will be similar to the ones described
in Sections 4.1 and 4.3.1. However, depending on how the IP paging
protocol is designed, additional harm may be caused.
4. Requirements
The following requirements are identified for the IP paging protocol.
4.1. Impact on Power Consumption
The IP paging protocol MUST minimize impact on the Host's dormant
mode operation, in order to minimize excessive power drain.
4.2. Scalability
The IP paging protocol MUST be scalable to millions of Hosts.
4.3. Control of Broadcast/Multicast/Anycast
The protocol SHOULD provide a filter mechanism to allow a Host prior
to entering dormant mode to filter which broadcast/multicast/anycast
packets active a page. This prevents the Host from awakening out of
dormant mode for all broadcast/multicast/anycast traffic.
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4.4. Efficient Signaling for Inactive Mode
The IP paging protocol SHOULD provide a mechanism for the Tracking
Agent to determine whether the Host is in inactive mode, to avoid
paging when a host is completely unreachable.
4.5. No Routers
Since the basic issues involved in handling mobile routers are not
well understood and since mobile routers have not exhibited a
requirement for paging, the IP paging protocol MAY NOT support
routers. However, the IP paging protocol MAY support a router acting
as a Host.
4.6. Multiple Dormant Modes
Recognizing that there are multiple possible dormant modes on the
Host, the IP paging protocol MUST work with different implementations
of dormant mode on the Host.
4.7. Independence of Mobility Protocol
Recognizing that IETF may support multiple mobility protocols in the
future and that paging may be of value to hosts that do not support a
mobility protocol, the IP paging protocol MUST be designed so there
is no dependence on the underlying mobility protocol or on any
mobility protocol at all. The protocol SHOULD specify and provide
support for a mobility protocol, if the Host supports one.
4.8. Support for Existing Mobility Protocols
The IP paging protocol MUST specify the binding to the existing IP
mobility protocols, namely mobile IPv4 [2] and mobile IPv6 [3]. The
IP paging protocol SHOULD make use of existing registration support.
4.9. Dormant Mode Termination
Upon receipt of a page (either with or without an accompanying L3
packet), the Host MUST execute the steps in its mobility protocol to
re-establish a routable L3 link with the Internet.
4.10. Network Updates
Recognizing that locating a dormant mode mobile requires the network
to have a rough idea of where the Host is located, the IP paging
protocol SHOULD provide the network a way for the Paging Agent to
inform a dormant mode Host what paging area it is in and the IP
paging protocol SHOULD provide a means whereby the Host can inform
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the Target Agent when it changes paging area. The IP paging protocol
MAY additionally provide a way for the Host to inform the Tracking
Agent what paging area it is in at some indeterminate point prior to
entering dormant mode.
4.11. Efficient Utilization of L2
Recognizing that many existing wireless link protocols support paging
at L2 and that these protocols are often intimately tied into the
Host's dormant mode support, the IP paging protocol SHOULD provide
support to efficiently utilize an L2 paging protocol if available.
4.12. Orthogonality of Paging Area and Subnets
The IP paging protocol MUST allow an arbitrary mapping between
subnets and paging areas.
4.13. Future L3 Paging Support
Recognizing that future dormant mode and wireless link protocols may
be designed that more efficiently utilize IP, the IP paging protocol
SHOULD NOT require L2 support for paging.
4.14. Robustness Against Failure of Network Elements
The IP paging protocol MUST be designed to be robust with respect to
failure of network elements involved in the protocol. The self-
healing characteristics SHOULD NOT be any worse than existing routing
protocols.
4.15. Reliability of Packet Delivery
The IP paging protocol MUST be designed so that packet delivery is
reliable to a high degree of probability. This does not necessarily
mean that a reliable transport protocol is required.
4.16. Robustness Against Message Loss
The IP paging protocol MUST be designed to be robust with respect to
loss of messages.
4.17. Flexibility of Administration
The IP paging protocol SHOULD provide a way to flexibly auto-
configure Paging Agents to reduce the amount of administration
necessary in maintaining a wireless network with paging.
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4.18. Flexibility of Paging Area Design
The IP paging protocol MUST be flexible in the support of different
types of paging areas. Examples are fixed paging areas, where a
fixed set of bases stations belong to the paging area for all Hosts,
and customized paging areas, where the set of base stations is
customized for each Host.
4.19. Availability of Security Support
The IP paging protocol MUST have available authentication and
encryption functionality at least equivalent to that provided by
IPSEC [5].
4.20. Authentication of Paging Location Registration
The IP paging protocol MUST provide mutually authenticated paging
location registration to insulate against replay attacks and to avoid
the danger of malicious nodes registering for paging.
4.21. Authentication of Paging Area Information
The IP paging protocol MUST provide a mechanism for authenticating
paging area information distributed by the Paging Agent.
4.22. Authentication of Paging Messages
The IP paging protocol MUST provide a mechanism for authenticating L3
paging messages sent by the Paging Agent to dormant mode Hosts. The
protocol MUST support the use of L2 security mechanisms so
implementations that take advantage of L2 paging can also be secured.
4.23. Paging Volume
The IP paging protocol SHOULD be able to handle large numbers of
paging requests without denying access to any legitimate Host nor
degrading its performance.
4.24. Parsimonious Security Messaging
The security of the IP paging protocol SHOULD NOT call for additional
power consumption while the Host is in dormant mode, nor require
excessive message exchanges.
4.25. Noninterference with Host's Security Policy
The IP paging protocol MUST NOT impose any limitations on a Host's
security policies.
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4.26. Noninterference with End-to-end Security
The IP paging protocol MUST NOT impose any limitations on a Host's
ability to conduct end-to-end security.
4.27. Detection of Bogus Correspondent Nodes
The IP paging protocol SHOULD make provisions for detecting and
ignoring bogus correspondent nodes prior to paging messages being
wide cast on behalf of the correspondent node.
5. Functional Architecture
In this section, a functional architecture is developed that
describes the logical functional entities involved in IP paging and
the interfaces between them. Please note that the logical
architecture makes absolutely no commitment to any physical
implementation of these functional entities whatsoever. A physical
implementation may merge particular functional entities. For
example, the Paging Agent, Tracking Agent, and Dormant Monitoring
Agent may all be merged into one in a particular physical
implementation. The purpose of the functional architecture is to
identify the relevant system interfaces upon which protocol
development may be required, but not to mandate that protocol
development will be required on all.
5.1. Functional Entities
The functional architecture contains the following elements:
Host - The Host (H) is a standard IP host in the sense of [4]. The
Host may be connected to a wired IP backbone through a wireless
link over which IP datagrams are exchanged (mobile usage pattern),
or it may be connected directly to a wired IP network, either
intermittently (nomadic usage pattern) or constantly (wired usage
pattern). The Host may support some type of IP mobility protocol
(for example, mobile IP [2] [3]). The Host is capable of entering
dormant mode in order to save power (see [1] for a detailed
discussion of dormant mode). The Host also supports a protocol
allowing the network to awaken it from dormant mode if a packet
arrives. This protocol may be a specialized L2 paging channel or
it may be a time-slotted dormant mode in which the Host
periodically wakes up and listens to L2 for IP traffic, the
details of the L2 implementation are not important. A dormant
Host is also responsible for determining when its paging area has
changed and for responding to changes in paging area by directly
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or indirectly informing the Tracking Agent about its location.
Since routers are presumed not to require dormant mode support, a
Host is never a router.
Paging Agent - The Paging Agent is responsible for alerting the
Host when a packet arrives and the Host is in dormant mode.
Alerting of the Host proceeds through a protocol that is peculiar
to the L2 link and to the Host's dormant mode implementation,
though it may involve IP if supported by the L2. Additionally,
the Paging Agent maintains paging areas by periodically wide
casting information over the Host's link to identify the paging
area. The paging area information may be wide cast at L2 or it
may also involve IP. Each paging area is served by a unique
Paging Agent.
Tracking Agent - The Tracking Agent is responsible for tracking a
Host's location while it is in dormant mode or active mode, and
for determining when Host enters inactive mode. It receives
updates from a dormant Host when the Host changes paging area.
When a packet arrives for the Host at the Dormant Monitoring
Agent, the Tracking Agent is responsible for notifying the Dormant
Monitoring Agent, upon request, what Paging Agent is in the Host's
last reported paging area. There is a one to one mapping between
a Host and a Tracking Agent.
Dormant Monitoring Agent - The Dormant Monitoring Agent detects
the delivery of packets to a Host that is in Dormant Mode (and
thus does not have an active L2 connection to the Internet). It
is the responsibility of the Dormant Monitoring Agent to query the
Tracking Agent for the last known Paging Agent for the Host, and
inform the Paging Agent to page the Host. Once the Paging Agent
has reported that a routable connection to the Internet exists to
the Host, the Dormant Monitoring Agent arranges for delivery of
the packet to the Host. In addition, the Host or its Tracking
Agent may select a Dormant Monitoring Agent for a Host when the
Host enters dormant mode, and periodically as the Host changes
paging area.
5.2. Interfaces
The functional architecture generates the following list of
interfaces. Note that the interfaces between functional entities
that are combined into a single network element will require no
protocol development.
Host - Paging Agent (H-PA) - The H-PA interface supports the
following types of traffic:
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- Wide casting of paging area information from the Paging
Agent.
- The Paging Agent alerting the Host when informed by the
Dormant Monitoring Agent that a packet has arrived.
Host - Tracking Agent (H-TA) - The H-TA interface supports the
following types of traffic:
- The Host informing the Tracking Agent when it has changed
paging area, and, optionally, prior to entering dormant
mode, in what paging area it is located.
- Optionally, the Host informs the Tracking Agent at a planned
transition to inactive mode.
Dormant Monitoring Agent - Tracking Agent (DMA-TA) - The DMA-TA
interface supports the following types of traffic:
- A report from the Dormant Monitoring Agent to the Tracking
Agent that a packet has arrived for a dormant Host for which
no route is available.
- A report from the Tracking Agent to the Dormant Monitoring
Agent giving the Paging Agent to contact in order to page
the Host.
- A report from the Tracking Agent to the Dormant Monitoring
Agent that a Host has entered inactive mode, if not provided
directly by the Host
- A report from the Tracking Agent to the Dormant Monitoring
Agent that a Host has entered dormant mode, if not provided
directly by the Host.
Dormant Monitoring Agent - Paging Agent (DMA-PA) - The DMA-PA
interface supports the following types of traffic:
- A request from the Dormant Monitoring Agent to the Paging
Agent to page a particular Host in dormant mode because a
packet has arrived for the Host.
- Negative response indication from the Paging Agent if the
Host does not respond to a page.
- Positive response from the Paging Agent indication if the
Host does respond to a page.
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- Delivery of the packet to the Host.
Host - Dormant Monitoring Agent (H-DMA) - The H-DMA interface
supports the following types of traffic:
- The Host registers to the Dormant Monitoring Agent prior to
entering dormant mode, (if needed) with filtering
information on which broadcast/multicast/anycast packets
trigger a page.
- The Host informs the Dormant Monitoring Agent, when it
directly deregisters from the Dormant Monitoring Agent due
to a change from dormant mode to active or inactive mode.
5.3. Functional Architecture Diagram
The functional architecture and interfaces lead to the following
diagram.
+------+ H-TA +----------+
| Host | <----------------------> | Tracking |
+------+ | Agent |
^ ^ +----------+
| | H-DMA ^
| +------------------------------+ |
| | | DMA-TA
| | |
| H-PA | |
v v v
+--------+ DMA-PA +------------+
| Paging | <--------------------> | Dormant |
| Agent | | Monitoring |
+--------+ | Agent |
+------------+
Figure 1 - Paging Functional Architecture
6. Acknowledgements
The authors would like to thank Arthur Ross for helpful comments on
this memo.
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7. References
[1] Kempf, J., "Dormant Mode Host Alerting ("IP Paging") Problem
Statement", RFC 3132, June 2001.
[2] Perkins, C., ed., "IP Mobility Support", RFC 2002, October,
1996.
[3] Johnson, D., and Perkins, C., "Mobility Support in Ipv6", Work
in Progress.
[4] Braden, R., "Requirements for Internet Hosts - Communication
Layers", STD 3, RFC 1122, October 1989.
[5] Kent, S., and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
8. Authors' Addresses
James Kempf
Sun Microsystems Laboratories
901 San Antonio Rd.
UMTV29-235
Palo Alto, CA
95303-4900
USA
Phone: +1 650 336 1684
Fax: +1 650 691 0893
EMail: James.Kempf@Sun.COM
Pars Mutaf
INRIA Rhone-Alpes
655 avenue de l'Europe
38330 Montbonnot Saint-Martin
FRANCE
Phone:
Fax: +33 4 76 61 52 52
EMail: pars.mutaf@inria.fr
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Claude Castelluccia
INRIA Rhone-Alpes
655 avenue de l'Europe
38330 Montbonnot Saint-Martin
FRANCE
Phone: +33 4 76 61 52 15
Fax: +33 4 76 61 52 52
EMail: claude.castelluccia@inria.fr
Nobuyasu Nakajima
Toshiba America Research, Inc.
P.O. Box 136
Convent Station, NJ
07961-0136
USA
Phone: +1 973 829 4752
EMail: nnakajima@tari.toshiba.com
Yoshihiro Ohba
Toshiba America Research, Inc.
P.O. Box 136
Convent Station, NJ
07961-0136
USA
Phone: +1 973 829 5174
Fax: +1 973 829 5601
EMail: yohba@tari.toshiba.com
Ramachandran Ramjee
Bell Labs, Lucent Technologies
Room 4g-526
101 Crawfords Corner Road
Holmdel, NJ
07733
USA
Phone: +1 732 949 3306
Fax: +1 732 949 4513
EMail: ramjee@bell-labs.com
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Yousuf Saifullah
Nokia Research Center
6000 Connection Dr.
Irving, TX
75039
USA
Phone: +1 972 894 6966
Fax: +1 972 894 4589
EMail: Yousuf.Saifullah@nokia.com
Behcet Sarikaya
Alcatel USA, M/S CT02
1201 Campbell Rd.
Richardson, TX
75081-1936
USA
Phone: +1 972 996 5075
Fax: +1 972 996 5174
EMail: Behcet.Sarikaya@usa.alcatel.com
Xiaofeng Xu
Alcatel USA, M/S CT02
1201 Campbell Rd.
Richardson, TX
75081-1936
USA
Phone: +1 972 996 2047
Fax: +1 972 996 5174
Email: xiaofeng.xu@usa.alcatel.com
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9. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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