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Versions: 00 01 02 03                                                   
IETF Mobile IP Working Group                          Hemant Chaskar
INTERNET-DRAFT                                                Editor
Expires: November 2001                         Nokia Research Center
                                                           June 2001


               Requirements of a QoS Solution for Mobile IP

                draft-ietf-mobileip-qos-requirements-00.txt


Status of This Memo

   This document is an Internet-Draft and is in full conformance
   with all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
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   as reference material or to cite them other than as "work in
   progress."

   The list of current Internet-Drafts can be accessed at
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   The  list of Internet-Draft Shadow Directories can be accessed at
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Copyright Notice

   Copyright (c) The Internet Society (2001). All rights reserved.

Abstract

   Mobile IP protocol ensures correct routing of packets to mobile
   node as the mobile node changes its point of attachment with the
   Internet. However, it is also required to provide proper QoS
   forwarding treatment to 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 of an IP QoS mechanism for its satisfactory operation
   with Mobile IP.








Hemant Chaskar                                               [Page i]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


1.0 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, 2]. 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 a 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 the new care-of address after
   handover, and hence, may not be recognized by some forwarding
   functions along the old path that use IP address as a key.
   Finally, handover may occur between the subnets that are under
   different administrative control.

   In the light of this scenario, it is essential to establish proper
   QoS support at the intermediate nodes in the new end-to-end path
   of the MN's packet stream.

1.2 An approach for solving 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 the 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 draft. The last three steps are not dealt with here in
   detail. However, so as to create useful insight into the Mobile IP
   QoS problem, wherever relevant, this draft highlights the
   shortcomings of some popular current practices (proposals) for
   establishing QoS support along the packet path, in the light of
   the requirements imposed by Mobile IP.



Hemant Chaskar                                               [Page 1]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


2 0 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 RFC 2119.


3 0 Requirements of a QoS solution for Mobile IP

   This section describes the requirements of a QoS solution for
   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.

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 end-to-end 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 get served with "default" QoS at the
   time of handover. The number of such packets MUST be minimized.

   As an example, this performance metric is computed in [3] for the
   case of end-to-end RSVP signaling [4] 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 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

Hemant Chaskar                                               [Page 2]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


   to the affected segment of the end-to-end path only. Of course, if
   the end-to-end path changes at large after handover, the QoS
   mechanism MUST be able to address that in a manner that is
   consistent with the QoS scheme(s) used along the new
   end-to-end packet path.

   Note that the QoS signaling protocol such as RSVP [5] 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
   fails to localize the QoS signaling [see 6]. In addition, it will
   cause double reservations on the part of end-to-end path that
   remains unchanged after handover.

   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.

   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 Seamless Mobility working groups.
   Examples are Fast Handover [7, 8], Regional Registrations [9],
   Hierarchical MIPv6 [10], Context Transfer [11] etc. The QoS
   mechanism for Mobile IP SHOULD take advantage of these mobility
   protocols for 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.



Hemant Chaskar                                               [Page 3]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


   2. Interoperability with heterogeneous end-to-end packet paths as
   regards QoS paradigms:

   The new end-to-end path of MN's packet stream may encounter
   network domains employing a variety of QoS paradigms, such as
   IntServ, DiffServ and MPLS. Each of the networks/routers along
   this path may require a different kind of information about the
   MN's packet stream, so that proper QoS forwarding treatment can
   be established for the MN's packet stream. The QoS mechanism for
   Mobile IP MUST be able to establish proper QoS forwarding
   treatment for the MN's packet stream in these QoS-heterogeneous
   network domains in the new end-to-end path.

   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 somehow programmed in this access router. Further,
   assume that the QoS policy in this access network takes care of
   SLAs with other networks that it attaches to. 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. Here is another example of
   cross-QoS-technology handover. Suppose that the MN is currently
   attached to an access router that is a part of access network X
   and is to be handed over to the access router that is a part of
   access network Y. In network X, the access router acts as a proxy
   (and possibly communicates with some QoS agent in the network) to
   program (possibly end-to-end) QoS forwarding treatment for the
   MN's packet stream. On the other hand, network Y expects the end
   hosts attached to it to send explicit QoS request messages along
   the data path.

   The QoS solution for Mobile IP MUST be able to establish QoS
   support for MN's packet stream over the packet paths that use
   diverse (best current practices) end-to-end QoS mechanisms.

3.3 Miscellaneous requirements

   1. QoS support along multiple 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 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


Hemant Chaskar                                               [Page 4]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


   external mechanisms such as, say, mobility management, policy,
   location privacy requirement etc. Further, the same QoS mechanism
   may not be able to support all the three alternatives.

   2. Interactions with link-layer support for QoS:

   The QoS mechanism MAY provide some information to the link
   layers for them to support the required QoS. Since a vast number
   of devices using Mobile IP will be connected to the Internet via
   wireless links, wireless link significant QoS parameters such as
   error rate MAY have to be included in the set of QoS parameters to
   be possibly considered and supported by the underlying link layer.

   An example scenario will be two UDP streams requiring different
   levels of error protection at the link layer. For such cases, an
   IP-layer QoS mechanism may indicate some generic parameters such
   as acceptable IP packet loss rate to link layers.

3.4. Obvious requirements

   The QoS solution for Mobile IP SHOULD satisfy obvious 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.


4.0 Concluding Remarks

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


5.0 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, Marc Greis
   (Nokia), Glenn Morrow (Nortel), Phil Roberts and Michael Thomas
  (Cisco) for their comments during the preparation of this document.





Hemant Chaskar                                               [Page 5]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


6.0 References

[1] IP Mobility Support, C. Perkins (Editor), RFC 2002, October 1996.

[2] Mobility Support in IPv6, D. Johnson and C. Perkins,
    draft-ietf-mobileip-ipv6-13.txt,
    work in progress, November 2000.

[3] A Framework for QoS Support in Mobile IPv6, H. Chaskar and
    R. Koodli, draft-chaskar-mobileip-qos-01.txt,
    work in progress, March 2001.

[4] A Framework for Integrated Services Operation over Diffserv
    Networks, Yoram Bernet et. al., RFC 2998, November 2000.

[5] Analysis of Mobile IP and RSVP Interactions, Michael Thomas,
    draft-thomas-seamoby-rsvp-analysis-00.txt,
    work in progress, February 2001.

[6] Resource ReSerVation Protocol -- Version 1 Functional
    Specification, R. Braden et. al., RFC 2750, September 1997.

[7] Low Latency Handoffs in Mobile IPv4, MIPv4 Handoffs Design Team,
    draft-ietf-mobileip-lowlatency-handoffs-v4-00.txt,
    work in progress, February 2001.

[8] Fast Handovers for Mobile IPv6, MIPv6 Handover Design Team,
    draft-ietf-mobileip-fast-mipv6-01.txt,
    work in progress, April 2001.

[9] Mobile IPv6 Regional Registrations, J. Malinen, Frank Le , and
    C. Perkins, draft-malinen-mobileip-regreg6-01.txt,
    work in progress, March 2001.

[10] Hierarchical MIPv6 Mobility Management, H. Soliman,
    C. Castelluccia, K. El-Malki, and L. Bellier,
    draft-ietf-mobileip-hmipv6-02.txt,
    work in progress, February 2001.

[11] Context Transfer Framework for Seamless Mobility, R. Koodli and
    C. Perkins, draft-koodli-seamoby-ctv6-00.txt,
    work in progress, February 2001.










Hemant Chaskar                                               [Page 6]


INTERNET-DRAFT         Mobile IP QoS Requirements          June, 2001


7.0 Addresses

  The working group can be contacted via the current chairs:

    Basavaraj Patil                     Phil Roberts
    Nokia Corporation
    6000 Connection Drive               20251 Century Blvd
    M/S M8-540                          Suite 120
    Irving, Texas 75039, USA            Germantown, MD 20874
    Phone:  +1 972-894-6709             Phone:  +1 847-202-9314
    EMail:  Basavaraj.Patil@nokia.com   EMail:  proberts@MEGISTO.com

  Questions about this memo can be directed to the authors:

   Hemant Chaskar
   Nokia Research Center
   5 Wayside Road
   Burlington, MA 01803, USA
   Phone: +1 781-993-3785
   EMail: hemant.chaskar@nokia.com
































Hemant Chaskar                                               [Page 7]