[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04

MULTIMOB Group                                                 H. Asaeda
Internet-Draft                                           Keio University
Intended status: Standards Track                            T C. Schmidt
Expires: January 14, 2010                                    HAW Hamburg
                                                           July 13, 2009


         IGMP and MLD Hold and Release Extensions for Mobility
         draft-asaeda-multimob-igmp-mld-mobility-extensions-03

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may contain material
   from IETF Documents or IETF Contributions published or made publicly
   available before November 10, 2008.  The person(s) controlling the
   copyright in some of this material may not have granted the IETF
   Trust the right to allow modifications of such material outside the
   IETF Standards Process.  Without obtaining an adequate license from
   the person(s) controlling the copyright in such materials, this
   document may not be modified outside the IETF Standards Process, and
   derivative works of it may not be created outside the IETF Standards
   Process, except to format it for publication as an RFC or to
   translate it into languages other than English.

   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.

   This Internet-Draft will expire on January 14, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




Asaeda & Schmidt        Expires January 14, 2010                [Page 1]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.














































Asaeda & Schmidt        Expires January 14, 2010                [Page 2]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


Abstract

   This document describes IGMP and MLD Hold and Release protocol
   extensions for hosts and routers.  The interoperability with the
   standard IGMPv3/MLDv2 protocols and these previous versions is also
   taken into account.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  IGMP/MLD Hold and Release  . . . . . . . . . . . . . . . . . .  6
     3.1.  Action for IGMP/MLD Hold Request . . . . . . . . . . . . .  6
     3.2.  Action for IGMP/MLD Release Request  . . . . . . . . . . .  6
     3.3.  Action for IGMP/MLD Hold Reception . . . . . . . . . . . .  7
     3.4.  Action for IGMP/MLD Release Reception  . . . . . . . . . .  8
     3.5.  IGMP/MLD Hold Message Format . . . . . . . . . . . . . . .  8
     3.6.  IGMP/MLD Hold Interval Timer . . . . . . . . . . . . . . . 11
     3.7.  Interoperability of IGMP/MLD Hold and Release  . . . . . . 11
   4.  Interoperability with Older Protocols  . . . . . . . . . . . . 12
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
























Asaeda & Schmidt        Expires January 14, 2010                [Page 3]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


1.  Introduction

   The Internet Group Management Protocol (IGMP) [2] for IPv4 and the
   Multicast Listener Discovery Protocol (MLD) [3] for IPv6 are the
   standard protocols used by hosts and multicast routers.  A mobile
   host sends a join/leave request for particular multicast session or
   channel to its upstream router (i.e., an adjacent router or IGMP/MLD
   proxy [8]), and the router will maintain the multicast reception (or
   membership) state of the host and serve multicast data to the host.

   Conceptually, IGMP and MLD work for mobile communications such with
   MIPv6 [11] or PMIPv6 [12].  However, wireless access technologies and
   mobile communications need to preserve the limited resources of
   mobile hosts and networks [10] and smooth handover.  According to a
   smooth handover scenario, a mobile host wants to accelerate multicast
   service termination in the previous network before handoff and
   immediately rejoin the session after the movement.  As the router's
   behavior, when the router remains part of the multicast delivery
   tree, it keeps the session active without leaving from the session,
   while the data transmission is paused until the host completes the
   movement and resumed after the movement.

   This document describes the IGMPv3 and MLDv2 Hold and Release
   protocol extensions for mobile hosts and routers.  The IGMP/MLD Hold
   operation enables to keep the membership state for fast packet
   forwarding, and the IGMP/MLD Release operation ressumes forwarding
   the multicast data after the host movement.  Originally, an idea of
   MLD Hold was proposed in [13].

   Note that discussing the procedure of context transfer (CT) for
   mobility protocols and the message format for CT will be defined in
   other documents.  Discussing how a mobile host or a router detects
   the movement and triggers to send an IGMP/MLD Hold message is depend
   on mobility protocols, and hence out of scope of this document.

   The proposed solution interoperates with the IGMPv3 and MLDv2
   protocols and preserves compatibility with older versions of IGMP/
   MLD.













Asaeda & Schmidt        Expires January 14, 2010                [Page 4]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


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 RFC 2119 [1].

   IGMP/MLD Hold:
   IGMP/MLD Hold is an operation in which a neighboring mobile host or
   IGMP/MLD proxy requests a multicast router to suspend data forwarding
   for temporal period (during mobile host movement).

   IGMP/MLD Release:
   IGMP/MLD Release is an operation in which a neighboring mobile host
   or IGMP/MLD proxy requests a multicast router to resume data
   forwarding that was suspended by the router.

   Hold-Req Records:
   Hold-Req Records are IGMP/MLD Multicast Address Records (group and
   source address records with filter-mode) a mobile hosts requests to
   suspend.  Hold-Req Records are specified in an IGMP/MLD Hold message
   and MAY correspond to the set of Current-State Records the mobile
   host has joined.

   Release-Req Records:
   Release-Req Records are IGMP/MLD Multicast Address Records a mobile
   hosts requests to resume.  Release-Req Records are specified in an
   IGMP/MLD Release message and MAY correspond to the Hold-Req Records
   the mobile host has sent.

   Hold Records:
   Hold Records are the IGMP/MLD records for which a multicast router
   decides to suspend data forwarding.



















Asaeda & Schmidt        Expires January 14, 2010                [Page 5]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


3.  IGMP/MLD Hold and Release

3.1.  Action for IGMP/MLD Hold Request

   When a mobile host moves from a current network (i.e. a mobile host's
   point of attachment) to a different network, an IGMP/MLD Hold message
   is sent by either the mobile host itself or a neighboring IGMP/MLD
   proxy to which the mobile host currently attached.  The IGMP/MLD Hold
   message will be sent by the mobile host or the proxy depending on
   which mobile protocol is in use.  For instance, in MIPv6 [11], a
   mobile host detects its own movement and sends the IGMP/MLD Hold
   message to its upstream router (or Home Agent).  On the other hand,
   in PMIPv6 [12], while a mobile host initiates multicast join/leave
   requests by sending regular IGMP/MLD messages [2][3], it does not
   send the IGMP/MLD Hold message.  The reason is that a mobile host (or
   Mobile Node (MN) in [12]) does not manage its movement but the mobile
   access gateway (MAG) detects its movement.  In this case, MAG sends
   the corresponding IGMP/MLD Hold messages to its upstream router (in
   case of local routing) or local mobility anchor (LMA) (in case of
   bidirectional tunneling) upon the host movement.

   An IGMP/MLD Hold message is received by either the adjacent upstream
   router or an IGMP/MLD proxy that the mobile host attached.  An IGMP/
   MLD proxy performs a host portion of the IGMP/MLD protocol on the
   upstream interface, and an IGMP/MLD Hold message will be finally
   proceeded by a multicast router.  Therefore if an IGMP/MLD proxy
   receives an IGMP/MLD Hold message, it forwards the Hold message with
   the link-local IPv6 source address of its upstream interface.  (Note
   that there is a case that an IGMP/MLD proxy does not forward the Hold
   message.  See Section 3.3.)  If the upstream interface of the IGMP/
   MLD proxy is attached to another (cascaded) IGMP/MLD proxy, then the
   IGMP/MLD Hold message is forwarded to that cascaded proxy, and the
   cascaded proxy forwards the Hold message toward its upstream router.

3.2.  Action for IGMP/MLD Release Request

   When a mobile host completes its movement and attaches a new network,
   the host or the neighboring IGMP/MLD proxy immediately sends an IGMP/
   MLD Release message.  The Release-Req Records specified in the IGMP/
   MLD Release message MAY be the same as that of the Hold-Req Records
   the host sent (since the host does not know the Hold Records, and
   only knows Hold-Req Records).

   As well as an IGMP/MLD Hold message, an IGMP/MLD Release message MUST
   also be finally proceeded by a multicast router.  Hence if an IGMP/
   MLD proxy receives an IGMP/MLD Release message, it forwards the
   Release message with the link-local IPv6 source address of its
   upstream interface.  If proxies are cascaded, the IGMP/MLD Release



Asaeda & Schmidt        Expires January 14, 2010                [Page 6]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


   message is forwarded toward its upstream router.

3.3.  Action for IGMP/MLD Hold Reception

   When a multicast router receives an IGMP/MLD Hold message from a
   neighboring mobile host or IGMP/MLD proxy, it records the following
   information; 1) the source IP address of the IGMP/MLD Hold message,
   and 2) the Hold-Req Records.  After that, the router needs to decide
   whether it suspends the data forwarding or not.  Since the decision
   has to be made whether to know the message sender is the last member
   for notified sessions/channels, the router sends the Group-Specific
   or Group-and-Source Specific Queries for all Hold-Req Records in the
   Hold messages.  If the router receives the inquired IGMP/MLD reports,
   it eliminates the records from the Hold-Req Records and keeps
   forwarding the data.  If it does not receive the IGMP/MLD reports for
   some of the Hold-Req Records, it recognizes that the Hold message
   sender is the last member host joining the sessions or channels on
   the interface, keeps them as the Hold Records, and suspends the data
   forwarding.

   The multicast router maintains Hold Records until it receives the
   corresponding IGMP/MLD Release message (described in the next
   section) or the IGMP/MLD Hold Interval timer (described in
   Section 3.6) is expired.  When either the Release message reception
   or the timer expiration occurs, the router resume data forwarding for
   the Hold Records and discards the Hold Records.

   If a multicast router receives an IGMP/MLD Hold message whose
   Multicast Address Records have already kept in the Hold Records, the
   router restarts the IGMP/MLD Hold Interval timer for the
   corresponding Multicast Address Records.

   As described in [10], there is an advantage if a router has been
   tracking multicast memberships of all downstream hosts, as it can
   recognize whether the message sender host is the last member joining
   the sessions/channels without sending the Group-Specific or Group-
   and-Source Specific Queries.

   When an IGMP/MLD proxy receives an IGMP/MLD Hold message from a
   downstream mobile host, it forwards the message to its upstream
   router as described in Section 3.1.  Since the IGMP/MLD information
   presented by the proxy to its upstream routers is the aggregation of
   all its downstream group membership information, prior to forwarding
   the Hold message, an IGMP/MLD proxy MUST inquire downstream
   memberships and organize new Hold-Req Records.  Then it forwards the
   appropriate IGMP/MLD Hold message including the newly organized Hold-
   Req Records to its upstream router.




Asaeda & Schmidt        Expires January 14, 2010                [Page 7]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


3.4.  Action for IGMP/MLD Release Reception

   When a mobile host moves to a new network, the host or the
   neighboring IGMP/MLD proxy immediately sends an IGMP/MLD Release
   message to request its upstream router to release the hold request
   previously sent.  The format of the Release message is the same as
   that of the standard IGMP/MLD Current-State Report message.  (See
   Section 3.5.)

   When a multicast router receives an IGMP/MLD Release (i.e.  Current-
   State Report) message, the router examines the message sender and an
   IGMP/MLD Hold Interval timer.  If the router has the Hold Records
   given from the Release message sender, it compares the Hold Records
   with the notified Multicast Address Records specified in the IGMP/MLD
   Current-State Report message.  For the matched Multicast Address
   Records, the router then removes the entries from the Hold Records
   and resume data forwarding with restarting the group or source
   timers.  For the mismatched Multicast Address Records, the router
   keeps untouched (then removed by timeout) or explicitly starts the
   leave (or prune) procedures for the sessions/channels, while it
   depends on the implementation.

   If either the router does not have the corresponding Hold Records or
   the IGMP/MLD Hold Interval timer has expired, then the router does
   not take any action.

   If a router that did not recognize an IGMP/MLD Hold message (e.g.,
   due to packet loss or some troubles in its transmission) receives an
   IGMP/MLD Current-State Report message, it will accept the message as
   a regular Current-State Report IGMP/MLD message as specified in
   Section 3.7.

3.5.  IGMP/MLD Hold Message Format

   The following figure is the Report message format defined in IGMPv3
   [2] and MLDv2 [3].  Type field is either IGMP Version 3 Membership
   Report (0x22) or Version 2 Multicast Listener Report (decimal 143);
   it is not necessary to change IGMP/MLD Report message format to
   support IGMP/MLD Hold messages.












Asaeda & Schmidt        Expires January 14, 2010                [Page 8]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Type     |    Reserved   |           Checksum            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Reserved            |Nr of Mcast Address Records (M)|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .               Multicast Address Record [1]                    .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                               .                               .
     .                               .                               .
     .                               .                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .               Multicast Address Record [M]                    .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Multicast Address Record shown in the following figure defines
   new Record Types that express an IGMP/MLD Hold message.  For an IGMP/
   MLD Release operation, the standard IGMP/MLD Current-State Report
   message is used.























Asaeda & Schmidt        Expires January 14, 2010                [Page 9]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Record Type  |  Aux Data Len |     Number of Sources (N)     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                       Multicast Address                       .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                       Source Address [1]                      .
     .                                                               .
     |                                                               |
     +-                                                             -+
     .                               .                               .
     .                               .                               .
     .                               .                               .
     +-                                                             -+
     |                                                               |
     .                                                               .
     .                       Source Address [N]                      .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                         Auxiliary Data                        .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Value  Name and Meaning
   -----  ----------------

   7      HOLD_INCLUDE - indicates that the interface has a filter mode
          of INCLUDE for the specified multicast address.  The Source
          Address [i] fields in this Multicast Address Record contain
          the interface's source list for the specified multicast
          address.  A HOLD_INCLUDE Record is never sent with an empty
          source list.

   8      HOLD_EXCLUDE - indicates that the interface has a filter mode
          of EXCLUDE for the specified multicast address.  The Source
          Address [i] fields in this Multicast Address Record contain
          the interface's source list for the specified multicast
          address, if it is non-empty.  When a mobile host works with



Asaeda & Schmidt        Expires January 14, 2010               [Page 10]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


          LW-IGMPv3/LW-MLDv2 ([9]), the Multicast Address Record does
          not contain the Source Address [i] field with HOLD_EXCLUDE
          type value.

3.6.  IGMP/MLD Hold Interval Timer

   After a multicast router receiving an IGMP/MLD Hold message will
   identify the corresponding multicast sessions/channels, it suspends
   data forwarding and keeps the Hold Records until the given amount of
   timer value is expired.  This timer is named the "IGMP/MLD Hold
   Interval timer", which is a configurable value.

   The Hold Interval is used to allow a multicast router to resume the
   multicast session.  Therefore, if the multicast router does not
   receive the corresponding IGMP/MLD Release (or Current-State Record)
   message for the IGMP/MLD Release operation within the Hold Interval,
   it leaves the sessions/channels recorded in the Hold Records and
   discards the Hold Records.  Note that the router does not send any
   IGMP/MLD Query message for the timeout sessions/channels and
   immediately leave them.

   [TODO: We will provide the default Hold Interval value based on some
   experimental results in the revised version.  Note that this value
   will depend on each mobile protocol; hence the default value will be
   adjusted by operators.]

3.7.  Interoperability of IGMP/MLD Hold and Release

   If a multicast router does not support an IGMP/MLD Hold operation, it
   will ignore the IGMP/MLD Hold message.  In this case, an IGMP/MLD
   Current-State Report message sent by a mobile host that previously
   requested an IGMP/MLD Hold operation to stop forwarding data is dealt
   with as a new join request for the specified multicast sessions (when
   the corresponding group or source timer is expired) or simply updates
   the corresponding group and/or source timer (when these timers are
   not expired and the membership status has been still active).















Asaeda & Schmidt        Expires January 14, 2010               [Page 11]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


4.  Interoperability with Older Protocols

   This document assumes multicast routers that deal with mobile hosts
   MUST be IGMPv3/MLDv2 capable (regardless whether the protocols are
   the full version or not).  Therefore this document does not need to
   consider interoperability with older version protocols.













































Asaeda & Schmidt        Expires January 14, 2010               [Page 12]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


5.  Security Considerations

   TBD.

   For the use of IGMP/MLD Hold message, it may be required to confirm
   that the IGMP/MLD Hold messages sender is the IGMP/MLD Release
   sender.  This document assumes the use of the simplest way of
   comparing the sender's IP address of each message, while it may
   require a more secure mechanism which is robust for IP address
   spoofing.









































Asaeda & Schmidt        Expires January 14, 2010               [Page 13]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


6.  Acknowledgements

   Gorry Fairhurst, Dave Thaler, Matthias Waehlisch, and others provided
   many constructive and insightful comments.















































Asaeda & Schmidt        Expires January 14, 2010               [Page 14]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


7.  References

7.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to indicate requirement
         levels", RFC 2119, March 1997.

   [2]   Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
         Thyagarajan, "Internet Group Management Protocol, Version 3",
         RFC 3376, October 2002.

   [3]   Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
         (MLDv2) for IPv6", RFC 3810, June 2004.

   [4]   Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
         "Protocol Independent Multicast - Sparse Mode (PIM-SM):
         Protocol Specification (Revised)", RFC 4601, August 2006.

   [5]   Deering, S., "Host Extensions for IP Multicasting", RFC 1112,
         August 1989.

   [6]   Fenner, W., "Internet Group Management Protocol, Version 2",
         RFC 2373, July 1997.

   [7]   Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
         Discovery (MLD) for IPv6", RFC 2710, October 1999.

   [8]   Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet
         Group Management Protocol (IGMP) / Multicast Listener Discovery
         (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")",
         RFC 4605, August 2006.

   [9]   Liu, H., Cao, W., and H. Asaeda, "Lightweight IGMPv3 and MLDv2
         Protocols",
         draft-ietf-mboned-lightweight-igmpv3-mldv2-05.txt (work in
         progress), May 2009.

7.2.  Informative References

   [10]  Asaeda, H., "IGMP and MLD Optimization for Mobile Hosts and
         Routers",
         draft-asaeda-multimob-igmp-mld-optimization-00.txt (work in
         progress), July 2009.

   [11]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

   [12]  Gundavelli, S, Ed., Leung, K., Devarapalli, V., Chowdhury, K.,



Asaeda & Schmidt        Expires January 14, 2010               [Page 15]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


         and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [13]  Jelger, C. and T. Noel, "Multicast for Mobile Hosts in IP
         Networks: Progress and Challenges", IEEE Wireless
         Comm. pp.58-64, October 2002.














































Asaeda & Schmidt        Expires January 14, 2010               [Page 16]


Internet-Draft  IGMP and MLD Hold and Release Extensions       July 2009


Authors' Addresses

   Hitoshi Asaeda
   Keio University
   Graduate School of Media and Governance
   5322 Endo
   Fujisawa, Kanagawa  252-8520
   Japan

   Email: asaeda@wide.ad.jp
   URI:   http://www.sfc.wide.ad.jp/~asaeda/


   Thomas C. Schmidt
   HAW Hamburg
   Dept. Informatik
   Berliner Tor 7
   Hamburg,   D-20099
   Germany

   Email: Schmidt@informatik.haw-hamburg.de






























Asaeda & Schmidt        Expires January 14, 2010               [Page 17]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/