[Search] [txt|pdf|bibtex] [Tracker] [Email] [Nits]

Versions: 00                                                            
NEMO Working Group                                           E. K. Paik
Internet-Draft                                                H. S. Cho
Expires: April 16, 2004                       Seoul National University
                                                                T.Ernst
                                                        Keio University
                                                       October 17, 2003


             Multihomed Mobile Networks Problem Statements
              <draft-paik-nemo-multihoming-problem-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
     other groups may also distribute working documents as Internet-
     Drafts.

     Internet-Drafts are draft documents valid for a maximum of six
     months and may be updated, replaced, or obsoleted by other
     documents at any time. It is inappropriate to use Internet-Drafts
     as reference material or to cite them other than as "work in
     progress."

     The list of current Internet-Drafts can be accessed at
     http://www.ietf.org/ietf/1id-abstracts.txt

     The list of Internet-Draft Shadow Directories can be accessed at
     http://www.ietf.org/shadow.html.


Copyright Notice

     Copyright (C) The Internet Society (2003). All Rights Reserved.



Abstract

     This document describes the needs for multihoming support in
     network mobility (NEMO). Issues from designing and implementing
     multihomed mobile networks are analyzed in terms of mutiple
     connections management and usage.



Table of Contents





Paik, et al.                  Apr. 16, 2004                    [Page 1]


INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003


     1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
     2. Terms and Abbreviation . . . . . . . . . . . . . . . . . . . . 2
     3. The need for Multihoming. . . . . . . . . . . . . . . .. . . . 2
     4. Issue Statements . . . . . . . . . . . . . . . . . . . . . . . 3
     5. Route Optimization Considerations. . . . . . . . . . . . . . . 4
     6. Security Considerations. . . . . . . . . . . . . . . . . . . . 4
     References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . . 5



1. Introduction

     Multihomed mobile networks [1] provide advantage of enhancing
     session continuity and load balancing to the whole mobile networks.

     NEMO is based on mobile IPv6 [2], but multihoming in NEMO raises
     new problems that do not arise in mobile IPv6.

     In this document, a case is made for why multihoming is needed for
     NEMO and what the prerequisite issues for developing multihomed
     mobile networks.


2. Terms and Abbreviation

     It is assumed that readers are familar with the terminologies and
     abbreviations as defined in [1] and [2], and classifications in
     [3].


3. The need for multihoming

     There are two basic motivations for multihoming.

     1) Multihomed mobile networks enhance the session preservation of
     the mobile router (MR) used for mobile network nodes (MNNs).  Since
     a wireless link is not as stable as a wired link, session
     preservation is an important issue in the case of mobile networks.
     Especially in the case of NEMO, the session preservation of the MR
     concerns not only the MR itself but also the one or more MNNs
     behind it. If the MR can not maintain a continuous session, more
     than one or more MNNs will not be able maintain their sessions
     either. As the number of MNNs increases, the impact of MR session
     disconnection also increases. Therefore the session preservation of
     the MR is critical in NEMO.

     2) Multihomed mobile networks share traffic load more efficiently
     by selecting the best available connection or enabling multiple
     connections simultaneously. Since all traffic goes through the MR
     in a mobile network, load sharing at the MR is critical.





Paik, et al.                  Apr. 16, 2004                    [Page 2]


INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003


4. Issue Statements

4.1 Connection availability

     Multiple connections of MRs can be used simultaneously or one at a
     time.

     1) When multiple connections are used simultaneously, the mode of
     operation can be either primary-secondary or peer-to-peer.  These
     configurations can be useful especially for large mobile networks,
     but there are many implementation issues which need to be
     addressed, e.g. which connection will be selected for each traffic
     folw that goes into/out of the mobile network ?

     2) When only one connection can be used at a time, e.g. in the case
     where a single connection has to substitute for all of the other
     failed connections, a connection selection mechanism is needed. The
     connection selection can depend on which connection is available at
     that time.


4.2 Connection selection

4.2.1 Who selects a connection ?

     The connection can be selected by the home agent (HA), the MR,
     and/or the MNN.

     1) The HA can select a connection based on the binding update
     information in the binding cache.

     2) The MR can select a connection since the MR is one of the main
     bodies of the connection.

     3) The MNN should be able to select a connection, e.g. in case
     where a user wants to select a particular access technology among
     the available technologies for reasons of cost or data rate.

     4) A hybrid mechanism should be also available, e.g. one in which
     the HA, the MR, and/or the MNN coordinate to select a connection.


4.2.2 Connection selection problem analysis

     Connection selection problem can be analyzed as follows.

     1) Selection by the HA: HAs coordination is needed when there are
     multiple HAs.

     2) Selection by the MR: This should allow communication between MRs
     in the case where there is multihoming with multiple MRs. [4] is an
     examples of MRs coordination for selecting a connection.




Paik, et al.                  Apr. 16, 2004                    [Page 3]


INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003


     3) Selection by the MNN: The MNN selects an MR when there are
     multiple MRs. For example, it can be a problem of prefix selection
     when MRs advertise different prefixes.

     The MNN selects a HA when there are multiple HAs. For example, it
     can be a problem of Internet service provider (ISP) selection when
     each HA is associated with different ISP.  Multiple HAs can be
     associated with different locations, access technologies, ISPs, and
     so on.


4.3 Scalability

     Should a new solution meets the all the eight configurations and
     the scenarios mentioned in [3]?


5. Route Optimization Considerations

     RO problems in multihomed mobile networks are dependant on how the
     connections are available and selected.

     1) In case of multiple HAs and HoAs, new route optimization may be
     possible by routing between CN and multiple HAs with different
     HoAs.

     2) When multiple connections are available simultaneously, how the
     CN knows about the availability and optimizes route ?


6. Security Considerations

     Security threats are dependant on how the connections are available
     and selected. So we will add security problems when they are
     encountered as the basic multihoming issues in NEMO are analyzed.



References

     [1]   Ernst, T. and H. Lach, "Network Mobility Support
           Terminology", Internet Draft:
           draft-ietf-nemo-terminology-00.txt, Work In Progress,
           May 2003.

     [2]   Johnson, D. B., Perkins, C. E. and Arkko, J., "Mobility
           Support in IPv6", Internet Draft:
           draft-ietf-mobileip-ipv6-24.txt, Work In Progress,
           June 2003.

     [3]  C. Ng, J. Charbon, í—Multi-Homing Issues in Bi-directional
           Tunneling,í˜ Internet Draft:




Paik, et al.                  Apr. 16, 2004                    [Page 4]


INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003


           draft-ng-nemo-multihoming-issues-01.txt, Work In Progress,
           May 2003.

     [4]  Eun Kyoung Paik and Yanghee Choi, "Management of Multiple
           Mobile Routers for Continuous Multimedia in Mobile WLANs,"
           Lecture Notes in Computer Science, Springer-Verlag,
           vol. 2532, Dec. 2002, pp.680-687.


Authors' Addresses

  Eun Kyoung Paik
  Multimedia and Computer Communications Lab.
  Seoul National University
  ENG4190, School of Electronic Engineering and Computer Science
  Seoul National University
  Seoul 151-744, Korea

  Phone: +82 2 880 1832
  Fax: +82 2 872 2045
  EMail: eun@mmlab.snu.ac.kr
  URL:   htpp://mmlab.snu.ac.kr/~eun


  Ho-Sik Cho
  Multimedia and Computer Communications Lab.
  Seoul National University
  ENG4190, School of Electronic Engineering and Computer Science
  Seoul National University
  Seoul 151-744, Korea

  Phone: +82 2 880 1832
  Fax: +82 2 872 2045
  EMail: hscho@mmlab.snu.ac.kr
  URL:   htpp://mmlab.snu.ac.kr/~hscho


  Thierry Ernst
  Jun Murai Lab.
  Keio University K2 Town Campus
  1488-8 Ogura, Saiwai-ku, Kawasaki
  Kanagawa  212-0054
  Japan

  Phone: +81-44-580-1600
  EMail: ernst@sfc.wide.ad.jp
  URL:   htpp://www.sfc.wide.ad.jp/~ernst









Paik, et al.                  Apr. 16, 2004                    [Page 5]