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rfc:rfc3583

Network Working Group H. Chaskar, Ed. Request for Comments: 3583 Nokia Research Center Category: Informational September 2003

 Requirements of a Quality of Service (QoS) Solution for Mobile IP

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 (2003).  All Rights Reserved.

Abstract

 Mobile IP ensures correct routing of packets to a mobile node as the
 mobile node changes its point of attachment to the Internet.
 However, it is also required to provide proper Quality of Service
 (QoS) forwarding treatment to the mobile node's packet stream at the
 intermediate nodes in the network, so that QoS-sensitive IP services
 can be supported over Mobile IP.  This document describes
 requirements for an IP QoS mechanism for its satisfactory operation
 with Mobile IP.

Chaskar Informational [Page 1] RFC 3583 Mobile IP QoS Requirements September 2003

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Problem Statement. . . . . . . . . . . . . . . . . . . .  2
     1.2.  An approach for solving QoS problem in Mobile IP . . . .  3
 2.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  3
 3.  Requirements of a QoS solution for Mobile IP . . . . . . . . .  3
     3.1.  Performance requirements . . . . . . . . . . . . . . . .  4
     3.2.  Interoperability requirements. . . . . . . . . . . . . .  5
     3.3.  Miscellaneous requirements . . . . . . . . . . . . . . .  6
     3.4.  Standard requirements. . . . . . . . . . . . . . . . . .  7
 4.  Security Considerations. . . . . . . . . . . . . . . . . . . .  7
 5.  Recommendation . . . . . . . . . . . . . . . . . . . . . . . .  8
 6.  Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . .  8
 7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     7.1.  Normative References . . . . . . . . . . . . . . . . . .  8
     7.2.  Informative References . . . . . . . . . . . . . . . . .  8
 8.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  9
 9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 10

1. Introduction

 Mobile IP is a technology that allows a "mobile node" (MN) to change
 its point of attachment to the Internet while communicating with the
 "correspondent node" (CN) using IP.  The formal description of Mobile
 IP can be found in [1, 6].  Mobile IP primarily addresses the correct
 routing of packets to MN's current point of attachment with the
 Internet.
 It is also essential to provide proper Quality of Service (QoS)
 forwarding treatment to the packets sent by or destined to MN as they
 propagate along different routes in the network due to node mobility.
 This document will identify the requirements that Mobile IP places on
 an IP QoS mechanism.

1.1. Problem Statement

 When an MN using Mobile IP undergoes handover from one access router
 to another, the path traversed by MN's packet stream in the network
 may change.  Such a change may be limited to a small segment of the
 end-to-end path near the extremity, or it could also have an end-to-
 end impact.  Further, the packets belonging to MN's ongoing session
 may start using a new care-of address after handover.  Hence, they
 may not be recognized by some forwarding functions in the nodes even
 along that segment of the end-to-end path that remains unaltered
 after handover.  Finally, handover may occur between the subnets that
 are under different administrative control.

Chaskar Informational [Page 2] RFC 3583 Mobile IP QoS Requirements September 2003

 In the light of this scenario, it is essential to establish proper
 QoS support for the MN's packet stream along the new packet path.

1.2. An approach for solving the QoS problem in Mobile IP

 There are four important steps involved in solving the QoS problem
 for Mobile IP.  They are as follows: (1) List the requirements that
 Mobile IP places on the QoS mechanism, (2) Evaluate current IP QoS
 solutions against these requirements, (3) Decide if current solutions
 need to be extended, or if new ones need to be defined, and (4)
 Depending on the result of step 3, define new solutions or fix the
 old ones.
 Of these, the first step, i.e., the requirements step, is addressed
 in this document.  The last three steps are not dealt with here in
 detail.  However, so as to create useful insight into the Mobile IP
 QoS problem, at times this document highlights the shortcomings of
 some well known current proposals for establishing QoS support for
 the packet stream in the network, when directly used with Mobile IP.

2. Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in BCP 14, RFC 2119 [2].

3. Requirements of a QoS solution for Mobile IP

 This section describes the requirements for a QoS solution for its
 satisfactory operation with Mobile IP.  Conversely, note that only
 Mobile IP-specific requirements are described here.  We do not assume
 any particular version (4 or 6) of IP while describing the
 requirements.  Solutions can be designed for IPv4 and IPv6
 independently, or a single solution can be designed to work with both
 versions.
 In this document, we assume that the target access router for MN's
 handover is already pinned down by other protocols.  For example,
 Seamoby working group has started work on the candidate access router
 discovery protocols [7].  Thus, any QoS-capability specific
 negotiations that may affect the handover decision are outside the
 scope of QoS solution as such, rather need to be performed by
 candidate and target access router selection protocols.

Chaskar Informational [Page 3] RFC 3583 Mobile IP QoS Requirements September 2003

3.1. Performance requirements

 1. Minimize the interruption in QoS at the time of handover:
    At the time of handover, interruption in QoS would occur if the
    packets sent by or destined to the MN arrive at the intermediate
    node in the new packet path without that node having information
    about their QoS forwarding requirement.  Then, those packets will
    receive default forwarding treatment.  Such QoS interruption MUST
    be minimized.  A good metric for this performance is the number of
    packets that may potentially get served with the "default" QoS at
    the time of handover.  The number of such packets MUST be
    minimized.
    As an example, this performance metric is computed in [8] for the
    case of end-to-end RSVP signaling [3] with Mobile IPv6.  It is
    shown there that when the end-to-end path of packets changes at
    large after handover or when the care-of address changes after
    handover, OPWA (One Pass With Advertisement) model of reservation
    used by RSVP causes the latency of about one round-trip time
    between the MN and the CN before QoS can be established along the
    new packet path.  In other words, the packets using the new care-
    of address that would be released by the MN or the CN during one
    round-trip time, after these nodes are ready to use the new care-
    of address, may get default forwarding treatment at the
    intermediate nodes.  Such a latency in QoS programming may be
    acceptable at the time of session initiation, but it is not
    acceptable in the middle of an active session as would be the case
    with handover.
 2. Localize the QoS (re)establishment to the affected parts of the
    packet path in the network:
    In many cases, handover changes only a small segment of the end-
    to-end path of MN's packet stream near the extremity.  Then, the
    QoS mechanism MUST limit the extent of QoS (re)establishment to
    the affected segment of the end-to-end path only.
    However, note that handover may sometimes cause the end-to-end
    path of MN's packet stream in the network to change at large.
    This may happen, for example, in the case of handover between
    different administrative domains.  If the QoS mechanism used to
    establish QoS support for the MN's packet stream along the new
    packet path in the network is based on the explicit end-to-end
    provisioning as such, it MUST perform so at the time of such
    handover.

Chaskar Informational [Page 4] RFC 3583 Mobile IP QoS Requirements September 2003

    When the care-of address changes upon handover, it may be required
    to perform some signaling even over the unchanged part of the
    end-to-end path if the path contains any QoS mechanisms that use
    IP address as a key to forwarding functions.  Examples are FILTER
    SPECs in the IntServ nodes or packet classifiers at the edges of
    DiffServ networks.  However, double provisioning of resources over
    the unchanged part of the packet path MUST be avoided.
    Note that the QoS signaling protocol such as RSVP [9] can localize
    the QoS signaling to the affected parts of the end-to-end path if
    the care-of address does not change upon handover.  However, if
    the care-of address changes upon handover, RSVP as currently
    defined [4] fails to localize the QoS signaling.  In addition, it
    will cause double reservations on the part of end-to-end path that
    remains unchanged after handover.
 3. Releasing after handover the QoS state (if any) along the old
    packet path:
    The QoS mechanism MUST provide some means (explicit or timer-
    based) to release any QoS state along the old packet path that is
    not required after handover.  It is desirable that the unwarranted
    QoS states, if any, along the old path are released as quickly as
    possible at the time of handover.  Note that, during handover, the
    MN may not always get a chance to send explicit tear down message
    along the old path because of the loss of link layer connectivity
    with the old access router.

3.2. Interoperability requirements

 1. Interoperability with mobility protocols:
    A number of mobility protocols that are complementary to Mobile IP
    are already defined or may be defined in future in IETF,
    particularly in Mobile IP and Seamoby working groups.  Examples
    are fast handover [10, 11], localized mobility management [12,
    13], context transfer [5] etc.  The QoS mechanism for Mobile IP
    SHOULD take advantage of these mobility protocols for the
    optimized operation.  However, the QoS scheme MUST have provisions
    to accomplish its tasks even if one or more of these mobility
    protocols are not used.
 2. Interoperability with heterogeneous packet paths as regards QoS
    paradigms:
    The new path after handover, of the MN's packet stream, may
    traverse network domains employing different QoS paradigms
    compared to those along the old path.  The QoS mechanism for

Chaskar Informational [Page 5] RFC 3583 Mobile IP QoS Requirements September 2003

    Mobile IP SHOULD be able to establish proper QoS forwarding
    treatment for the MN's packet stream along the packet paths
    deploying different QoS paradigms (best current practices), in a
    manner consistent with the QoS mechanism deployed along those
    paths.
    As an illustration, suppose that the MN is currently attached to
    an access router which is the edge router of a DiffServ network,
    and that the packet classifier and traffic policer for the MN's
    flows are presently programmed in this access router.  Now,
    suppose that the MN needs to be handed over to the access router
    which is at the edge of an IntServ network.  The new access
    network would expect the exchange of RSVP messages so that proper
    QoS forwarding treatment can be established for the MN's packet
    stream in that access network.  QoS mechanism for Mobile IP SHOULD
    have provisions to handle such heterogeneity as regards the QoS
    mechanisms deployed along different packet paths.

3.3. Miscellaneous requirements

 1. QoS support along multiple packet paths:
    After MN undergoes handover from one access router to another,
    potentially, there could be multiple paths over which MN's packet
    may propagate.  Examples of these path are: route-optimized path
    between the MN and its CN, triangle route via Home Agent (HA),
    temporary tunnel between old and new access routers, reverse
    tunnel from the new access router (Foreign Agent) to HA etc.  A
    QoS mechanism SHOULD be able to support QoS along the different
    potential packet paths.  However, whether all paths are supported
    or only a subset of them is supported will be determined by
    external mechanisms such as mobility management, policy, location
    privacy requirement and so on.  Further, the same QoS mechanism
    may not be able to support all these paths.
 2. Interactions with wireless link-layer support for QoS:
    Since a vast number of devices using Mobile IP will be connected
    to the Internet via wireless links, the QoS mechanism for Mobile
    IP MAY provide some information to the wireless link layers for
    them to support the required QoS.
    An example scenario that may benefit from such information is that
    of the two UDP streams associated with the same media, but
    requiring different levels of error protection at the wireless
    link layer due to certain characteristics of their respective
    encoding schemes.  The packets of these two streams are equally
    delay sensitive (so as to maintain playout synchronization at the

Chaskar Informational [Page 6] RFC 3583 Mobile IP QoS Requirements September 2003

    receiver), and hence, may be treated equally (as regards queuing)
    by IP layer.  But they may need to be transmitted on wireless
    channels of different error characteristics (say different FEC
    coding or power levels).
    The QoS information included for the benefit of wireless link
    layers SHOULD be such that it is meaningful both ways: to
    applications that reside over IP so that they can choose the IP
    service of certain QoS characteristics and to wireless link QoS
    managers so that they can then map this information to the details
    of lower layer mechanisms and their parameters.
    In the example scenario described above, such a QoS information
    could be expressed as the acceptable loss rate of IP packets in
    the UDP stream.  This parameter enables the UDP application to
    choose the IP service having QoS that matches its requirements,
    and it also enables the wireless link QoS managers to choose the
    right wireless channel to transmit the packets of this UDP stream.

3.4. Standard requirements

 The QoS solution for Mobile IP SHOULD satisfy standard requirements
 such as scalability, security, conservation of wireless bandwidth,
 low processing overhead on mobile terminals, providing hooks for
 authorization and accounting, and robustness against failures of any
 Mobile IP-specific QoS components in the network.  While it is not
 possible to set quantitative targets for these desirable properties,
 the QoS solution MUST be evaluated against these criteria.

4. Security Considerations

 The QoS (re)establishment triggered by node mobility MUST be guarded
 against security attacks.  Such attacks could be launched by
 malicious nodes that spoof the QoS signaling to make it appear to the
 intermediate nodes that the MN has undergone handover.  Such an
 attack could disrupt the QoS offered to MN's ongoing sessions as the
 intermediate nodes may then tear down the QoS along some segments of
 the true packet paths between MN and CN.  The malicious nodes may
 also request a reduced level of QoS or supply fake packet
 classifiers, thereby affecting QoS over some segments (e.g., that do
 not get affected by the spoofed handover) of the true packet paths
 between MN and CN.  Further, network resources may be wasted or used
 in an unauthorized manner by the malicious nodes that spoof MN's
 handover.  To prevent this, QoS mechanism MUST provide means for
 intermediate nodes to verify the authenticity of handover-induced QoS
 (re)establishment.

Chaskar Informational [Page 7] RFC 3583 Mobile IP QoS Requirements September 2003

5. Recommendation

 In this document, we described the requirements for a QoS solution
 for its satisfactory operation with Mobile IP.  The expectation is
 that the appropriate working group will use this requirements
 document to provide a QoS solution for Mobile IP.

6. Acknowledgment

 I would like to acknowledge the participants of the mailing list that
 was set up to discuss the above requirements.  Their contributions
 and active participation in the discussion on the mailing list were
 very useful in the preparation of this document.  Special thanks are
 due to, in alphabetical order, Brian Carpenter (IBM), Marc Greis
 (Nokia), Glenn Morrow (Nortel), Phil Roberts (Megisto) and Michael
 Thomas (Cisco) for their input during the preparation of this
 document.

7. References

7.1. Normative References

 [1]  Perkins, C., Ed., "IP mobility support for IPv4", RFC 3344,
      August 2002.
 [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [3]  Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L., Speer,
      M., Braden, R., Davie, B., Wroclawski, J. and E. Felstaine, "A
      Framework for Integrated Services Operation over Diffserv
      Networks", RFC 2998, November 2000.
 [4]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and S. Jamin,
      "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
      Specification", RFC 2205, September 1997.
 [5]  Kempf, J., Ed., "Problem description: Reasons for performing
      context transfers between nodes in an IP Access Network", RFC
      3374, September 2002.

7.2. Informative References

 [6]  Johnson, D., Perkins, C. and J. Arkko, "Mobility support in
      IPv6", Work in Progress, May 2003.

Chaskar Informational [Page 8] RFC 3583 Mobile IP QoS Requirements September 2003

 [7]  Trossen, D., et al., "Issues in Candidate Access Router
      discovery for seamless IP handoffs", Work in Progress, October
      2002.
 [8]  Chaskar, H. and R. Koodli, "QoS support in Mobile IP version 6",
      IEEE Broadband Wireless Summit (Networld+Interop), May 2001.
 [9]  Thomas, M., "Analysis of Mobile IP and RSVP interactions", Work
      in Progress, February 2001.
 [10] MIPv4 Handoffs Design Team, "Low latency handoffs in Mobile
      IPv4", Work in Progress, June 2002.
 [11] Koodli, R., Ed., "Fast handovers for Mobile IPv6", Work in
      Progress, March 2003.
 [12] Williams, C., Ed., "Localized mobility management requirements",
      Work in Progress, March 2003.
 [13] Soliman, H., et al., "Hierarchical MIPv6 mobility management
      (HMIPv6)", Work in Progress, October 2002.

8. Authors' Addresses

 The working group can be contacted via the current chair:
 John Loughney
 Nokia Research Center
 11-13 Italahdenkatu
 00180 Helsinki
 Finland
 EMail: john.loughney@nokia.com
 Questions about this memo can be directed to the editor:
 Hemant Chaskar
 Nokia Research Center
 5 Wayside Road
 Burlington, MA 01803, USA
 Phone: +1 781-993-3785
 EMail: hemant.chaskar@nokia.com

Chaskar Informational [Page 9] RFC 3583 Mobile IP QoS Requirements September 2003

9. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  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 assignees.
 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.

Chaskar Informational [Page 10]

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