





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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