Internet Draft Thomas C. Schmidt
HAW Hamburg
Matthias Waehlisch
Expires: May 2006 FHTW Berlin
November 2005

Seamless Multicast Handover in a
Hierarchical Mobile IPv6 Environment (M-HMIPv6)

IPR Statement

By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79[1].

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This document extends the Hierarchical Mobile IPv6 Internet Draft to
include the reception and transmission of Any Source Multicast
traffic at the Mobile Node. It introduces handover mechanisms for
IPv6 mobile multicast listeners and mobile multicast senders.
Operations are based on a Mobile IPv6 environment with local mobility
anchor points. These local anchor points are conformal with a
Hierarchical Mobile IPv6 proxy infrastructure. Handover latencies in
the proposed scheme remain bound to link switching delays with
respect to these local proxy points. Thus the M-HMIPv6 achieves

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seamless mobility, even though no bicasting of multicast streams is
used. Multicast listeners in addition encounter the option to
optimize multicast routing by turning to a direct data reception.
The mechanisms described in this document do not rely on assumptions
of any specific multicast routing protocol in use. The M-HMIPv6
protocol operations utilize the existing HMIPv6, MIPv6 and MLDv2
messages under minor extensions.

Table of Contents

1. Terminology....................................................3

2. Introduction...................................................3

3. Overview of M-HMIPv6...........................................4
3.1 Operations of a multicast listener.........................5
3.2 Operations of a multicast sender...........................5

4. Multicast specific extensions of MIPv6, HMIPv6 and MLDv2.......6
4.1 M-HMIPv6 flag in MAP option message........................6
4.2 Use of Home Address Destination Option in mobile multicast.7
4.3 Binding Cache processing at Correspondent Node.............7
4.4 Home Agent Multicast Membership control....................7
4.5 Router attendance control in MLD...........................8

5. Protocol Details...............................................9
5.1 Operations of all Mobile Nodes............................10
5.2 Mobile multicast listener.................................10
5.2.1 Operations of the Mobile Node........................10
5.2.2 Operations of the MAP................................11
5.2.3 Buffering............................................12
5.3 Mobile multicast source...................................12
5.3.1 Operations of the Mobile Node........................12
5.3.2 Operations of the MAP................................13
5.3.3 Tree initialization procedure........................13
5.3.4 Buffering............................................14
5.4 Protocol Timer............................................14

6. Security Considerations.......................................14

7. IANA Considerations...........................................14

8. References....................................................15


Author's Addresses...............................................16

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A. A Note on Tunneling...........................................16

Copyright Notice.................................................17

Disclaimer of Validity...........................................17


1. Terminology

The terminology used in this document remains conformal to the
definitions in MIPv6 [4] and HMIPv6 [6].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
document are to be interpreted as described in RFC-2119 [2].

2. Introduction

Multicast-based packet distribution plays an important role in real-
time applications, as it provides the only efficient, scalable scheme
for group communication. However, any source multicasting itself
conceals complex mechanisms for group membership management and
routing, which both are of slow convergence. To achieve seamless
mobility here is one of the most challenging and demanded
developments in IP networks today.

In multimedia conference scenarios each member commonly operates as
receiver and as sender for multicast based group communication.
In addition, real-time communication such as voice or video over IP
places severe temporal requirement on mobility protocols: Seamless
handover scenarios need to limit disruptions or delay to less than
100 ms. Jitter disturbances are not to exceed 50 ms. Note that 100 ms
is about the duration of a spoken syllable in real-time audio

The fundamental approach to deal with mobility in IPv6 [3] is stated
in the Mobile IPv6 RFCs [4,5]. MIPv6 operates address changes on the
IP layer transparent to the transport layer as a device moves from
one network to the other. MIPv6 involves roundtrip messages for
location updates directly with the MNs Home Agent and the
Correspondent Node. As these nodes can be far away, MIPv6 may exhibit
slow handover performance. The Hierarchical Mobility Management
(HMIPv6) Internet Draft [6] introduces a proxy architecture of
Mobility Anchor Points (MAPs) to reduce communication delays with

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respect to the HA. In addition the Fast Handover for Mobile IPv6
Internet Draft [7] proposes predictive delay hiding techniques to
further reduce handover times in unicast data.

MIPv6 only roughly treats multicast mobility, in a pure remote
subscription approach or through bi-directional tunneling via the
Home Agent. It thereby suffers from slow handovers and inefficient,
triangular forwarding. It is the issue of this document to extend the
improved HMIPv6 mobility infrastructure by mechanisms of sending and
receiving multicast traffic for the MN. Local MAPs serve as temporary
multicast relays to hide partly movement, partly handoff latency of
the MN. The multicast support through a MAP infrastructure may
significantly reduce the attained handover frequencies [11]. Handover
procedures between MAPs solely built on MIPv6 and HMIPv6 signaling
are described within this draft. They are designed to limit any
disruption or disturbance to the time scale needed for reconnecting
to neighboring MAPs. An additional option in multicast data delivery
allows for turning to optimal routing, after a receiver handover has
been completed. Minor MLD [9,10] extensions are required to operate
this optimization option. All mechanisms remain transparent to any
specific multicast routing protocol in use.

3. Overview of M-HMIPv6

This multicast mobility scheme is built on a HMIPv6 environment.
HMIPv6 introduces Mobility Anchor Points as proxy elements, which may
be best viewed as functions on regional routers. For implementing
multicast mobility it is advantageous, but not necessary, that these
regional routers provide multicast routing functionality.

In M-HMIPv6 a mobile multicast node uses its local MAP as anchor
point for multicast communication. All multicast traffic is directed
through this MAP using the Regional Care-of Address RCoA as multicast
subscriber or source address. Traffic forwarding between MN and its
MAP is done using a bi-directional tunnel [8].

If a MN changes location within its MAP domain, it only registers its
new LCoA with the MAP as defined in [6]. This does not affect
multicast routing trees. When entering a new MAP domain a MN will be
eager to sustain multicast connectivity via its previously
established MAP. Eventually it will learn of M-HMIPv6 support through
router advertisements with MAP option messages, and will then perform
a reactive handover. Multicast handover procedures will occur only if
the MN changes into a new M-HMIPv6 enabled MAP domain and will then
transfer multicast traffic from the previous to the current MAP.

An M-HMIPv6-aware MN SHOULD use the MAP for multicast communication.
However, the MN MAY prefer to use its HA as a multicast anchor point,

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e.g. in visited networks within its home site. A mobile node, which
is not M-HMIPv6 aware, will not use its MAP as a multicast anchor
point, but will use the MIPv6 tunnel through the HA instead. In this
sense M-HMIPv6 is simply a smooth extension of HMIPv6, which itself
smoothly extends MIPv6.

3.1 Operations of a multicast listener

To join a multicast group away from home the MN tunnels the MLD
[9,10] listener report to its current MAP using RCoA as source
address. The MAP records the group address in its Binding Cache in
order to forward multicast packets to the MN and to subscribe for and
preserve MNs multicast group membership.

When changing its MAP domain, the MN submits a Binding Update with
its new LCoA to the previous MAP in addition to regular HMIPv6
handover signaling. On its reception the previous MAP redirects
multicast packet forwarding to the MN's new LCoA.

If multicast support is advertised in the new domain the MN
immediately SHOULD join the multicast group through the new MAP. Once
multicast group traffic arrives the MN SHOULD send a Binding Update
with zero lifetime to its previous MAP to eliminate its Binding Cache
entry and end packet forwarding.

3.2 Operations of a multicast sender

In a foreign MAP domain a MN initiates multicast-based communication
by sending packets through its MAP using RCoA as its source address.
As receivers are aware of source addresses and as the mobile RCoA
address may change, a Home Address Destination Option MUST be
included (s. section 4.2). By transmitting multicast packets along
this path a routing tree originating at the MAP will be constructed.
Local movement of the MN within a MAP domain thereby remains
transparent to multicast routing.

Sending MCast Traffic to receivers
MAP-Domain1 /------------------------------------>
/-----| MAP1 |-----\
|| ||
|| ||
+-----+ ||
| AR1 | ||
+-----+ ||
|| ||
|| ||

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|\-----+-----+ || ||
\------| MN | || ||
+-----+ || ||
|| || Movement
|| ||
MAP-Domain2 || ||
+-----+-----/| \/
/------| MN |------/
| AR2 |
\-----| MAP2 |
+-------+ Sending MCast Traffic to receivers

Figure 1: Intra-MAP-domain Handover for mobile multicast senders

Upon arrival in a new MAP domain the MN submits a Binding Update with
its new LCoA to the previously established multicast-forwarding MAP
and continues its multicast delivery via this previous MAP (s. figure
1). If multicast support is advertised in the new domain the MN
immediately initiates a new multicast routing tree with the new RCoA
as source address anchored at its current MAP. The routing tree
SHOULD be initiated via the tree initialization procedure described
in section 5.3.3. Alternatively, bi-casting of data streams MAY be

The handover procedure completes after a predefined timeout is
reached: The mobile multicast source continues to deliver data only
via its new MAP and stops forwarding through its previous MAP.

4. Multicast specific extensions of MIPv6, HMIPv6 and MLDv2

4.1 M-HMIPv6 flag in MAP option message

M-HMIPv6 support is advertised within the MAP option message as used
for router advertisements according to HMIPv6 [6]. For this purpose
an appropriate flag is added in the following way

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 | Length | Dist | Pref |*|M| Reserved |

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| Valid Lifetime |
| |
+ +
| |
+ Global IP Address for MAP +
| |
+ +
| |


* Used by HMIPv6
M When set indicates that M-HMIPv6 is supported by
the current MAP

4.2 Use of Home Address Destination Option in mobile multicast

Multicast applications normally are aware of source addresses, which
MUST NOT change during ongoing communication. A mobile multicast
sender therefore MUST include a home address destination option as
defined in [4]. This requirement deviates from MIPv6 multicast

4.3 Binding Cache processing at Correspondent Node

A Correspondent Node receiving multicast packets with Home Address
Option in general need not have a Binding Cache Entry for the home
address included. A CN therefore SHALL NOT verify multicast packets
with respect to its Binding Cache. This requirement deviates from
MIPv6 unicast scheme.

4.4 Home Agent Multicast Membership control

To provide multicast connectivity to a mobile multicast listener away
from home, a HA needs to take care of the local multicast group
management. This essentially can be done by either supplying full
multicast routing functionalities at the HA, or by a proxy agent

In the first case it suffices for the HA to observe MNs group
membership at the (tunnel) interface. For a multicast proxy function

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a HA must answer MLD queries according to group membership states of
the MN. This is an extension of the specifications in [4].

4.5 Router attendance control in MLD

To enable route optimization at a mobile multicast listener away from
home, a specific multicast router (e.g. MAP) MAY terminate its packet
forwarding to the MN. However, to preserve its ability to restart
fast packet forwarding, it may be desirable for this router to remain
part of the multicast delivery tree. To support such router
attendance control (see [14] for preliminary ideas), a minor code
extension of the Multicast Listener Discovery Protocol [9,10] is

A multicast router (e.g. it encounters low link resources in a
multilinked environment) MAY submit an MLD Listener Query for one or
several multicast groups with an attendance code field in place.
Activating the attendance code field will initiate multicast
receivers to actively search for an alternate multicast subscription.
The attendance code field in MLD Listener Query attains the following

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 = 130 | Code | Checksum |
| Maximum Response Code | Reserved |
| |
. .
. .
| |

Type Multicast Listener Query (Type = decimal 130)

0: Query on actively forwarded multicast groups
1: Query on multicast groups intended for attendance

The corresponding attendance code field in MLDv2 Listener Report
attains the following form:

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 = 143 | Code | Checksum |

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| Reserved |Nr of Mcast Address Records (M)|
| |
. .
. ... .
| |

Type Version 2 Multicast Listener Report Message
(Type = decimal 143)

0: Report on multicast address records,
requested for active forwarding
1: Report on multicast address records,
requested for attendance

On reception of an attendance coded router query a multicast listener
SHOULD attempt to receive multicast data through an alternate
interface. After initiation of the attendance coded report the
multicast router MUST continue to deliver multicast data. It also
MUST continue to submit (possibly attendance coded) Listener Queries
according to the rules in [9,10]. If in return of a query (with or
without attendance code) a router does only receive Listener Reports
containing an attendance code, the router SHOULD stop to forward the
specific group traffic onto the corresponding link, but sustain
membership in the appropriate multicast delivery tree. After a
multicast router has turned into attendance mode, it MUST continue to
query onto the 'attended' groups. These queries MUST carry the
attendance code field.

If a multicast listener has succeeded to receive multicast traffic
for one or several groups via a new interface (as reaction on
attendance coded router query or on its own initiative), it MAY wish
to preserve fast forwarding capabilities on the previous link. To do
so a listener MAY submit an MLDv2 Listener Report for the groups in
common, containing an attendance code. After such termination of
multicast forwarding, any receiver MAY re-initiate multicast
forwarding for any desired multicast group under 'attendance' on such
link by submitting an MLDv2 Listener Report without the attendance
code. Attendance coded router queries MUST be answered according to
the rules in [9,10], either with or without attendance code.

5. Protocol Details

This section describes M-HMIPv6 operations as are to be performed for
multicast traffic in addition to the MIPv6 and HMIPv6 protocols. Two
perspectives need a general distinction: Multicast processing of a
mobile listener and a mobile sender.

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Mobility Anchor Points as defined in [6] attain the role of multicast
mobility anchor points (M-MAPs) for mobile group members in M-HMIPv6.
All multicast traffic is directed through M-MAPs using RCoA
consistently as identifier with respect to the multicast routing
tree. M-MAPs may be viewed as HA proxies for multicast streams, just
as MAPs in the unicast case.

5.1 Operations of all Mobile Nodes

Being at home the MN may either use its Home Agent or, a possibly
distinct, regional M-MAP as multicast anchor point. Away from home
the MN will learn about regional M-MAPs through router advertisements
(s. section 4.1). A MN SHOULD register with the regional M-MAP having
the highest preference value. If M-HMIPv6 is not supported regionally
the MN first SHOULD attempt to employ a previously established M-MAP
relation, second register with its HA.

M-MAP presence is advertised via router advertisements with MAP
option message as described in section 4.1.

5.2 Mobile multicast listener

Any node on a multicast enabled network may remotely subscribe to
multicast group membership by using its link-local address in MLD
membership reports. In doing so a MN cannot expect to experience a
smooth handover performance while changing from one network to

A MN utilizing an HMIPv6 MAP infrastructure can be regarded as eager
for decreased handover delays and therefore SHOULD use the M-HMIPv6
M-MAP functionality for other than link locally scoped multicast

5.2.1 Operations of the Mobile Node

A mobile multicast listener registers with its local M-MAP (or HA),
where both communicate via a bi-directional tunnel. The MN submits
its MLD group membership listener report through this tunnel and
answers membership queries of the anchor point.

When a Mobile Node changes its network, it performs a Binding Update
with its previous M-MAP and re-establishes the tunnel at its new
LCoA. Thereafter it continues to receive multicast group traffic.

On entering a new M-MAP domain a MN - in addition to the above BU -
registers with the new M-MAP and establishes a bi-directional tunnel.
It immediately sends a MLD listener report through the newly
available connection, one for each group/flow to be handed over. Once

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multicast group traffic arrives from the new M-MAP, the MN SHOULD
submit a BU with zero lifetime to its previous M-MAP and terminate
the corresponding tunnel. If previous binding of the MN had been with
the HA, the MN MUST NOT terminate its binding, but SHOULD tunnel an
MLD listener done message instead.

Note that a MN SHOULD preserve a previously established M-MAP
relation until a new multicast forwarding is completely established.
In the case of rapid movement this may lead to a previous multicast
anchor point persisting through several hops.

As an optional extension to optimize routing a MN MAY be enabled to
directly subscribe to multicast groups in its visited subnet. This
remote subscription SHOULD be performed, if triggered by M-MAP MLD
listener queries marked with attendance code as described in section
4.5. It MAY be performed on MN's own reasons, the recognition of slow
handover frequencies or significant M-MAP distance, for instance.

To optimize routing for a specific multicast group the MN undertakes
a regular MLD subscription at its link local interface using its
LCoA. After receiving multicast data on this link local interface,
the MN MUST tunnel an MLD listener report to its M-MAP with
attendance code as described in section 4.5. On further MLD listener
queries of its M-MAP the MN MUST reply with listener reports. These
reports SHOULD carry the attendance code as long as the MN receives
multicast streams locally.

5.2.2 Operations of the MAP

M-MAP operations for multicast listener support are completely analog
to Home Agent functions as described in [4] and section 4.4. An M-MAP
receiving a HMIPv6 BU from a MN will establish a bi-directional
tunnel. On reception of a tunneled MLD listener report it will

o record multicast group membership in its Binding Cache;
o observe and maintain multicast group membership on its specific
tunnel interface;
o inquire on MNs current group membership as described in [4];
o forward multicast group traffic to the MN (see [4] on
multicast packet forwarding rules).

The M-MAP may control multicast group membership either as a
multicast router or as a multicast proxy agent (s. section 4.4).

As an optional extension to optimize routing the M-MAP MAY be enabled
to direct MNs do directly subscribe to multicast groups within their
visited subnets by using the MLD attendance extensions described in
section 4.5. The M-MAP MAY decide to initiate remote subscriptions of
MNs by tunneling MLD queries with attendance code. This decision

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could be based on the number of attached MNs subscribed to the same
multicast groups or link capacities or forwarding load, for instance.
If the M-MAP itself acts as a multicast router, it will operate
exactly as described in section 4.5 for each tunnel interface
associated with a MN. Otherwise the M-MAP will intercept MLD queries
from multicast routers to add attendance codes. Similar it will
intercept listener reports from its attached MNs to remove attendance

Regardless of its own queries the M-MAP must continue to deliver
multicast streams to any attached MN, which reports on group
membership without attendance code.

5.2.3 Buffering

Some L2 technologies imply a noticeable offline period for a MN
during handover. To compensate for possible packet loss, buffering
mechanisms are needed. In M-HMIPv6 M-MAPs may provide automatic
replay buffers at the tunnel entry points, to be played out after a
MN's Binding Update occurred.

5.3 Mobile multicast source

A multicast source sending with its link-local address is immobile
with respect to multicast application persistence. A mobile multicast
sender MAY tunnel multicast traffic through its HA, using its home
address as source address [4]. Triangular routing and significant
binding update times lead to expected large handover delays, in

A MN utilizing a HMIPv6 MAP infrastructure therefore SHOULD use the
M-HMIPv6 M-MAP functionality for other than link locally scoped
multicast transmissions.

5.3.1 Operations of the Mobile Node

A mobile multicast sender is registered with its local M-MAP, where
both communicate via a bi-directional tunnel. The MN submits
multicast packets through this tunnel with the RCoA as the source
address and the home address included in a home address destination
option as defined in [4].

When a Mobile Node changes networks, it performs a Binding Update
with its previous M-MAP and re-establishes the tunnel at its new
LCoA. Thereafter it continues to send its multicast group traffic,
using previous RCoA as its source address.

On entering a new M-MAP domain a MN - in addition to the above BU -
registers with the new M-MAP and establishes a bi-directional tunnel.

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It immediately SHOULD start the tree initialization procedure as
defined in section 5.3.3 and start a timer. As soon as this timer
exceeds MAX_MCASTTREEINIT_TIMEOUT the MN MUST complete the handover
by terminating multicast group forwarding through its previous M-MAP
and submit all subsequent traffic to its current M-MAP using its
current RCoA as source address. Note that these handover steps can be
performed stream wise.

A MN, which moves to a new link within the same M-MAP domain before
the timeout is reached, performs a BU with its current M-MAP and
continues the handover procedure without resetting its timers.

A MN, which moves into a new M-MAP domain before the timeout
occurred, continues to forward multicast traffic through its
previously established old M-MAP, discontinues to communicate via its
previously not fully established intermediate M-MAP, resets its timer
and restarts the tree initialization procedure for its current M-MAP.

Thus in case of rapid movement the MN stays bound with its formerly
fully established (or first) M-MAP, serving the last completely
erected multicast routing tree.

5.3.2 Operations of the MAP

M-MAP operations for multicast sender support are completely analog
to MAP functions for unicast support as described in [6].

5.3.3 Tree initialization procedure

In preparation for a seamless handover of a multicast sender, a
distribution tree needs to be constructed by the routers, which
originates at the new M-MAP. In general, Any Source Multicast routing
trees will be initiated by submitting packets into the appropriate
multicast group. Depending on the routing protocol in use, this can
be a tardy procedure. A multicast sender MAY initiate a new group
tree by bi-casting its packets to its previous and its new point of
attachment. Bi-casting in the presence of slow routing protocols,
though, may result in a significant amount of duplicate traffic. In
many cases it may be highly desirable to proceed with less
communication overhead. The tree initialization procedure provides a
way for the MN to efficiently bridge the multicast routing
convergence gap.

In performing the tree initialization procedure, the source starts to
send probe packets, destined to all multicast groups under migration,
with complete IPv6 header, but without transport payload. In detail,
the next header field of tree initialization packets contains IPv6-
NoNxt (59) value. Subsequent packets SHOULD be sent with a random
delay uniformly chosen between 0 and MCASTTREEINIT_FREQUENCY.

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The tree initialization procedure ends after
MAX_MCASTTREEINIT_TIMEOUT is reached with continuous submission of
regular traffic to the initiated delivery tree.

5.3.4 Buffering

To prevent or reduce packet loss during handover, the mobile source
MAY buffer packets to be sent, while its tunnel to the M-MAP is not
established. This buffer should be played out as soon as the tunnel
re-establishment to the previous MAP has completed.

5.4 Protocol Timer

160 seconds (For DVMRP regimes)
0.5 seconds (For PIM-SM regimes)


Mobile nodes must allow these variables to be configured by system

6. Security Considerations

This specification uses the concepts of Mobile IPv6 and Hierarchical
Mobile IPv6 mobility management. All security provisions regarding
the relation between the Mobile Node and the Home Agents and between
the Mobile Node and the Mobility Anchor Points apply equally to this
M-HMIPv6 concept.
Threats of hijacking unicast sessions derive from attempts of a MN to
operate binding updates within multicast sessions. Any binding update
received within a multicast session therefore MUST be ignored.

7. IANA Considerations

This document defines extension codes for two ICMPv6 messages. For

Type Multicast Listener Query (Type = decimal 130)

and the

Type Version 2 Multicast Listener Report Message
(Type = decimal 143)

this requires the registration of two codes. The suggested values for
these codes are:

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0: Query on actively forwarded multicast groups
1: Query on multicast groups intended for attendance.

8. References

Normative References

1 Bradner, S., "Intellectual Property Rights in IETF Technology",
BCP 79, RFC 3979, March 2005.

2 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.

3 Hinden, R. and Deering, S. "Internet Protocol Version 6
Specification", RFC 2460, December 1998.

4 Johnson, D.B., Perkins, C., Arkko, J. "Mobility Support in IPv6",
RFC 3775, June 2004.

5 Arkko, J., Devarapalli, V., Dupont, F "Using IPsec to Protect
Mobile IPv6 Signaling Between Mobile Nodes and Home Agents", RFC
3776, June 2004.

6 Soliman, H., Castelluccia, C., El-Malki, K., Bellier, L.
"Hierarchical Mobile IPv6 mobility management", RFC 4140, August

7 Koodli, R. "Fast Handovers for Mobile IPv6", RFC 4068, July 2005.

8 Conta, A., Deering, S. "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998.

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

10 R. Vida and L. Costa (Eds.) "Multicast Listener Discovery Version
2 (MLDv2) for IPv6", RFC3810, June 2004.

Informative References

11 Schmidt, T.C. and Waehlisch, M. "Predictive versus Reactive -
Analysis of Handover Performance and Its Implications on IPv6 and
Multicast Mobility", Telecommunication Systems, Vol. 30, No. 1,
pp. 123-142, Berlin Heidelberg:Springer, 2005.

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M-HMIPv6 November 2005

12 Romdhani, I., Kellil, M., Lach, H.-Y. et. al. "IP Mobile
Multicast: Challenges and Solutions", IEEE Comm. Surveys, 6, 1,

13 Suh, K., Kwon, D.-H., Suh, Y.-J. and Park, Y. "Fast Multicast
Protocol for Mobile IPv6 in the fast handovers environments",
IETF, Internet Draft - (work in progress), February 2004.

14 Jelger, C., Noel, T. "Multicast for Mobile Hosts in IP Networks:
Progress and Challenges", IEEE Wireless Comm., pp 58-64, Oct.

15 Schmidt, T.C. and Waehlisch, M. "Multicast Mobility in MIPv6:
Problem Statement", draft-schmidt-mobopts-mmcastv6-ps-00.txt -
(work in progress), October 2005.


The authors would like to thank Stefan Zech (FHTW Berlin), Mark
Palkow (DaViKo GmbH) and Hans L. Cycon (FHTW Berlin) for valuable
discussions and a joyful collaboration.

Author's Addresses

Thomas C. Schmidt
HAW Hamburg, Dept. Informatik
Berliner Tor 7
D-20099 Hamburg
Phone: +49-40-42875-8157
Email: Schmidt@informatik.haw-hamburg.de

Matthias Waehlisch
FHTW Berlin, HRZ
Treskowallee 8
D-10318 Berlin
Email: mw@fhtw-berlin.de

A. A Note on Tunneling

Following the concepts of MIPv6 and HMIPv6 the packet forwarding to
and from the Mobile Node is organized by means of a tunnel section
spanned to a static anchor component such as a MAP or a Home Agent.

Schmidt, Waehlisch Expires - May 2006 [Page 16]
M-HMIPv6 November 2005

Through this technique a MN can hide its movement to CNs or to the
routing infrastructure.

However, keeping in mind real-time data requirements it is highly
desirable to avoid packet encapsulation. Besides the unwanted
overhead, a tunnel may hide QoS information of the original packet
headers and may require load and jitter generating packet
fragmentation, if the tunnel entry point is distinguished from the

Tunnelling can be avoided by a direct packet forwarding of the static
anchor components. Such forwarding requires a change of packet's
source or destination address at the forwarder, which usually
conflicts with checksums covering IPv6 pseudo headers. In M-MIPv6
multicast communication from a Mobile Node though carries a MIPv6
extension header, the home address destination option header. This
header denotes an alternate source address which enters the pseudo
header instead of the original IPv6 header address.

Multicast packets sent from the MN therefore could be forwarded by
the MAP to the network by replacing source addresses without
recalculation of header checksums. Employing such direct packet
forwarding would allow a MN to distribute multicast streams without a

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"This document and the information contained herein are provided on


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