One document matched: draft-ietf-multimob-fmipv6-pfmipv6-multicast-03.xml
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<front>
<title abbrev="Multicast for FMIPv6/PFMIPv6">Multicast Listener Extensions
for MIPv6 and PMIPv6 Fast Handovers</title>
<author fullname="Thomas C. Schmidt" initials="T C." role="editor"
surname="Schmidt">
<organization>HAW Hamburg</organization>
<address>
<postal>
<street>Dept. Informatik</street>
<street>Berliner Tor 7</street>
<city>Hamburg</city>
<region></region>
<code>D-20099</code>
<country>Germany</country>
</postal>
<email>schmidt@informatik.haw-hamburg.de</email>
</address>
</author>
<author fullname="Matthias Waehlisch" initials="M." surname="Waehlisch">
<organization>link-lab & FU Berlin</organization>
<address>
<postal>
<street>Hoenower Str. 35</street>
<city>Berlin</city>
<code>D-10318</code>
<country>Germany</country>
</postal>
<email>mw@link-lab.net</email>
</address>
</author>
<author fullname="Rajeev Koodli" initials="R." surname="Koodli">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>30 International Place</street>
<street>Xuanwu District,</street>
<city>Tewksbury</city>
<code>MA 01876</code>
<country>USA</country>
</postal>
<email>rkoodli@cisco.com</email>
</address>
</author>
<author fullname="Godred Fairhurst" initials="G." surname="Fairhurst">
<organization>University of Aberdeen</organization>
<address>
<postal>
<street>School of Engineering</street>
<city>Aberdeen</city>
<code>AB24 3UE</code>
<country>UK</country>
</postal>
<email>gorry@erg.abdn.ac.uk</email>
</address>
</author>
<author fullname="Dapeng Liu" initials="Dapeng" surname="Liu">
<organization>China Mobile</organization>
<address>
<phone>+86-123-456-7890</phone>
<email>liudapeng@chinamobile.com</email>
</address>
</author>
<date />
<workgroup>MULTIMOB Group</workgroup>
<abstract>
<t>Fast handover protocols for MIPv6 and PMIPv6 define mobility
management procedures that support unicast communication at reduced
handover latency. Fast handover base operations do not affect multicast
communication, and hence do not accelerate handover management for
native multicast listeners. Many multicast applications like IPTV or
conferencing, though, are comprised of delay-sensitive real-time traffic
and will benefit from fast handover execution. This document specifies
extension of the Mobile IPv6 Fast Handovers (FMIPv6) and the Fast
Handovers for Proxy Mobile IPv6 (PFMIPv6) protocols to include multicast
traffic management in fast handover operations. This multicast support
is provided first at the control plane by a management of rapid context
transfer between access routers, second at the data plane by an optional
fast traffic forwarding that may include buffering.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Mobile IPv6 <xref target="RFC6275"></xref> defines a network layer
mobility protocol involving participation by mobile nodes, while Proxy
Mobile IPv6 <xref target="RFC5213"></xref> provides a mechanism without
requiring mobility protocol operations at a Mobile Node (MN). Both
protocols introduce traffic disruptions on handovers that may be
intolerable in many real-time application scenarios such as gaming or
conferencing. Mobile IPv6 Fast Handovers (FMIPv6) <xref
target="RFC5568"></xref>, and Fast Handovers for Proxy Mobile IPv6
(PFMIPv6) <xref target="RFC5949"></xref> improve the performance of
these handover delays for unicast communication to the order of the
maximum of the delays needed for link switching and signaling between
Access Routers (ARs) or Mobile Access Gateways (MAGs) <xref
target="FMIPv6-Analysis"></xref>.</t>
<t>No dedicated treatment of seamless multicast data service has been
proposed by any of the above protocols. MIPv6 only roughly defines
multicast for Mobile Nodes using a remote subscription approach or a
home subscription through bi-directional tunneling via the Home Agent
(HA). Multicast forwarding services have not been specified at all in
<xref target="RFC5213"></xref>, but are subject to current specification
<xref target="RFC6224"></xref>, <xref
target="I-D.ietf-multimob-pmipv6-source"></xref>. It is assumed
throughout this document that mechanisms and protocol operations are in
place to transport multicast traffic to ARs. These operations are
referred to as 'JOIN/LEAVE' of an AR, while the explicit techniques to
manage multicast transmission are beyond the scope of this document.</t>
<t>Mobile multicast protocols need to serve applications such as IPTV
with high-volume content streams to be distributed to potentially large
numbers of receivers, and therefore should preserve the multicast nature
of packet distribution and approximate optimal routing <xref
target="RFC5757"></xref>. It is undesirable to rely on home tunneling
for optimizing multicast. Unencapsulated, native multicast transmission
requires establishing forwarding state, which will not be transferred
between access routers by the unicast fast handover protocols. Thus
multicast traffic will not experience expedited handover performance,
but an MN - or its corresponding MAG in PMIPv6 - can perform remote
subscriptions in each visited network.</t>
<t>This document specifies extensions to FMIPv6 and PFMIPv6 that include
multicast traffic management for fast handover operations. The protocol
extensions were designed under the requirements that</t>
<t><list style="symbols">
<t>multicast context transfer shall be transparently included in
unicast fast handover operations</t>
<t>neither unicast mobility protocols nor multicast routing shall be
modified or otherwise affected</t>
<t>no active participation of MNs in PMIPv6 domains is defined.</t>
</list></t>
<t>The solution common to both underlying unicast protocols defines the
per-group transfer of multicast contexts between ARs or MAGs. The
protocol defines corresponding message extensions necessary for carrying
group context information independent of the particular handover
protocol. ARs or MAGs are then enabled to treat multicast traffic
according to fast unicast handovers and with similar performance. No
protocol changes are introduced that prevent a multicast unaware node
from performing fast handovers with multicast aware ARs or MAGs.</t>
<t>The specified mechanisms apply when a mobile node has joined and
maintains one or several multicast group subscriptions prior to
undergoing a fast handover. It does not introduce any requirements on
the multicast routing protocols in use, nor are the ARs or MAGs assumed
to be multicast routers. It assumes network conditions, though, that
allow native multicast reception in both, the previous and new access
network. Methods to bridge regions without native multicast connectivity
are beyond the scope of this document.</t>
<section title="Use Cases and Deployment Scenarios">
<t>Multicast Extensions for Fast Handovers enable multicast services
in those domains that operate any of the unicast fast handover
protocols <xref target="RFC5568"></xref> or <xref
target="RFC5949"></xref>. Typically, fast handover protocols are
activated within an operator network or within a dedicated service
installation.</t>
<t>Multicast group communication has a variety of dominant use cases.
One traditional application area is infotainment with voluminous
multimedia streams delivered to a large number of receivers (e.g.,
IPTV). Other time-critical news items like stock-exchange prices are
commonly transmitted via multicast to support fair and fast updates.
Both may be mobile and both largely benefit from fast handover
operations. Operators may enhance their operational quality or offer
premium services by enabling fast handovers.</t>
<t>Another traditional application area for multicast is
conversational group communication in scenarios like conferencing or
gaming, but also in dedicated collaborative environments or teams.
Machine-to-machine communication in the emerging Internet of Things is
expected to generate various additional mobile use cases (e.g., among
cars). High demands on transmission quality and rapidly moving parties
may require fast handovers.</t>
<t>Most of the deployment scenarios above are bound to a fixed
infrastructure with consumer equipment at the edge. Today, they are
thus likely to follow an operator-centric approach like PFMIPv6.
However, Internet technologies evolve for adoption in
infrastructureless scenarios at disaster recovery, rescue, crisis
prevention and civil safety. Mobile end-to-end communication in groups
is needed in Public Protection and Disaster Relief (PPDR) scenarios,
where mobile multicast communication needs to be supported between
members of rescue teams, police officers, fire brigade teams,
paramedic teams, command control offices in order to support the
protection and health of citizens. These use cases require fast and
reliable mobile services which cannot rely on operator infrastructure.
They are thus predestined to running multicast with FMIPv6.</t>
</section>
</section>
<section title="Terminology">
<t>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 <xref
target="RFC2119"></xref>. The use of the term, "silently ignore" is not
defined in RFC 2119. However, the term is used in this document and can
be similarly construed.</t>
<t>This document uses the terminology of <xref target="RFC5568"></xref>,
<xref target="RFC5949"></xref>, <xref target="RFC6275"></xref>, and
<xref target="RFC5213"></xref> for mobility entities.</t>
</section>
<section title="Protocol Overview">
<t>This section provides an informative overview of the protocol
mechanisms without normative specifications.</t>
<t>The reference scenario for multicast fast handover is illustrated in
<xref target="fig1"></xref>.</t>
<figure anchor="fig1" title="Reference Network for Fast Handover">
<artwork><![CDATA[
*** *** *** ***
* ** ** ** *
* *
* Multicast Cloud *
* *
* ** ** ** *
*** *** *** ***
/ \
/ \
/ \
+........../..+ +..\..........+
. +-------+-+ .______. +-+-------+ .
. | PAR |()_______)| NAR | .
. | (PMAG) | . . | (NMAG) | .
. +----+----+ . . +----+----+ .
. | . . | .
. ___|___ . . ___|___ .
. / \ . . / \ .
. ( P-AN ) . . ( N-AN ) .
. \_______/ . . \_______/ .
. | . . | .
. +----+ . . +----+ .
. | MN | ----------> | MN | .
. +----+ . . +----+ .
+.............+ +.............+
]]></artwork>
</figure>
<section anchor="AR-context-transfer"
title="Multicast Context Transfer between Access Routers">
<t>In a fast handover scenario (cf. <xref target="fig1"></xref>),
ARs/MAGs establish a mutual binding and provide the capability to
exchange context information concerning the MN. This context transfer
will be triggered by detecting the forthcoming movement of an MN to a
new AR and assist the MN to immediately resume communication on the
new subnet using its previous IP address. In contrast to unicast,
multicast flow reception does not primarily depend on address and
binding cache management, but requires distribution trees to adapt so
that traffic follows the movement of the MN. This process may be
significantly slower than fast handover management <xref
target="RFC5757"></xref>. Multicast listeners at handover may offer
the twofold advantage of including the multicast groups under
subscription in context transfer. First, the NAR can proactively join
the subscribed groups as soon as it gains knowledge of them. Second,
multicast flows can be included in traffic forwarding via the tunnel
established from PAR to NAR.</t>
<t>There are two modes of operation in FMIPv6 and in PFMIPv6. The
predictive mode allows for AR-binding and context transfer prior to an
MN handover, while in the reactive mode, these steps are executed
after detection that the MN has re-attached to NAR. Details of the
signaling schemes differ between FMIPv6 and PFMIPv6 and are outlined
in <xref target="FMIPv6-overview"></xref> and <xref
target="PFMIPv6-overview"></xref>.</t>
<t>In a predictive fast handover, the access router (i.e., PAR (PMAG)
in <xref target="fig1"></xref>) learns about the impending movement of
the MN and simultaneously about the multicast group context as
specified in <xref target="FMIPv6-overview"></xref> and <xref
target="PFMIPv6-overview"></xref>. Thereafter, the PAR will initiate
an AR-binding and context transfer by transmitting a HI message to NAR
(NMAG). HI is extended by multicast group states carried in mobility
header options as defined in <xref target="multicast-option"></xref>.
On reception of the HI message, NAR returns a multicast
acknowledgement in its HACK answer that indicates its ability to
support each requested group (see <xref
target="multicast-ack"></xref>). NAR (NMAG) expresses its willingness
to receive multicast traffic from forwarding by PAR using standard MLD
signaling. There are several reasons to waive forwarding, e.g., the
NAR could already have a native subscription for the group(s), or
capacity constraints can hinder decapsulation of additional streams.
At the previous network, there may be policy of capacity constraints
that make it undesirable to forward the multicast traffic. The PAR can
add the tunnel interface to its multicast forwarding database for
those groups the MN wishes to receive, so that multicast flows can be
forwarded in parallel to the unicast traffic. The NAR implements an
MLD proxy <xref target="RFC4605"></xref> providing host-side behaviour
towards the upstream PAR. The proxy will submit an MLD report to the
upstream tunnel interface to indicate the set of groups to be
forwarded. It will terminate multicast forwarding from the tunnel when
the group is natively received. In parallel, NAR joins all groups that
are not already under subscription using its native multicast upstream
interface. While the MN has not arrived at a downstream interface of
the NAR, multicast subscriptions on behalf of the MN are associated
with Loopback as a downstream interface. Reception of the Join at the
NAR enables downstream native multicast forwarding of the subscribed
group(s).</t>
<t>In a reactive fast handover, the PAR will learn about the movement
of the MN, after the latter has re-associated with the new access
network. Also from the new link, it will be informed about the
multicast context of the MN. As group membership information is
present at the new access network prior to context transfer, MLD join
signaling can proceed in parallel to HI/HACK exchange. Following the
context transfer, multicast data can be forwarded to the new access
network using the PAR-NAR tunnel of the fast handover protocol.
Depending on the specific network topology multicast traffic for some
groups may natively arrive before it is forwarded from PAR.</t>
<t>In both modes of operation, it is the responsibility of the PAR
(PMAG) to properly apply multicast state management when an MN leaves.
Depending on the link type and MLD parameter settings, methods for
observing the departure of an MN need to be applied (cf., <xref
target="RFC5757"></xref>). While considering subscriptions of the
remaining nodes and from the tunnel interfaces, the PAR uses normal
multicast forwarding rules to determine whether multicast traffic can
be pruned.</t>
<t>This method allows an MN to participate in multicast group
communication with a handover performance that is comparable to
unicast handover.</t>
</section>
<section anchor="FMIPv6-overview"
title="Protocol Operations Specific to FMIPv6">
<t>ARs that provide multicast support in FMIPv6 will advertise this
general service by setting an indicator bit (M-bit) in its PrRtAdv
message as defined in <xref target="m-prtrtadv"></xref>. Additional
details about the multicast service support, e.g., flavors and groups,
will be exchanged within HI/HACK dialogs later at handovers.</t>
<t>An MN operating FMIPv6 will actively initiate the handover
management by submitting a fast binding update (FBU). The MN, which is
aware of the multicast groups it wishes to maintain, will attach
mobility options containing its group states (see <xref
target="multicast-option"></xref>) to the FBU, and thereby inform ARs
about its multicast context. ARs will use these multicast context
options for inter-AR context transfer.</t>
<t>In predictive mode, the FBU is issued on the previous link and
received by the PAR as displayed in <xref target="fmip-pred"></xref>.
The PAR will extract the multicast context options and append them to
its HI message. From the HACK message, PAR will redistribute the
multicast acknowledgement by adding the corresponding mobility options
to its FBACK message. From receiving the FBACK message, the MN will
group-wise learn about the multicast support in the new access
network. If some groups or multicast service models are not supported,
it can decide on taking actions to overcome the missing service (e.g.,
by tunneling). Note that the proactive multicast context transfer may
proceed successfully, even if the MN misses the FBACK message on the
previous link.</t>
<figure anchor="fmip-pred"
title="Predictive Multicast Handover for FMIPv6">
<artwork><![CDATA[
MN PAR NAR
| | |
|------RtSolPr------->| |
|<-----PrRtAdv--------| |
| | |
| | |
|---------FBU-------->|----------HI--------->|
| (Multicast MobOpt) | (Multicast MobOpt) |
| | |
| |<--------HAck---------|
| | (Multicast AckOpt) |
| | Join to
| | Multicast
| | Groups
| | |
| <-----FBack---|--FBack------> |
| (Multicast AckOpt) | (Multicast AckOpt) |
| | |
disconnect optional |
| packet ================>|
| forwarding |
| | |
connect | |
| | |
|------------UNA --------------------------->|
|<=================================== deliver packets
| |
]]></artwork>
</figure>
<t>The flow diagram for reactive mode is visualized in <xref
target="fmip-react"></xref>. After attaching to the new access link
and performing an unsolicited neighbor advertisement (UNA), the MN
issues an FBU which the NAR forwards to the PAR without processing. At
this time, the MN is able to re-join all subscribed multicast groups
without relying on AR assistance. Nevertheless, multicast context
options are exchanged in the HI/HACK dialog to facilitate intermediate
forwarding of requested flows. The multicast traffic could arrive from
a MN subscription at the same time the NAR receives the HI message.
Such multicast flows may be transparently excluded from forwarding by
setting an appropriate multicast acknowledge option. In either case,
the NAR MUST ensure that not more than one flow of the same group is
forwarded to the MN.</t>
<figure anchor="fmip-react"
title="Reactive Multicast Handover for FMIPv6">
<artwork><![CDATA[
MN PAR NAR
| | |
|------RtSolPr------->| |
|<-----PrRtAdv--------| |
| | |
disconnect | |
| | |
| | |
connect | |
|-------UNA-----------|--------------------->|
|-------FBU-----------|---------------------)|
| (Multicast MobOpt) |<-------FBU----------)|
| | |
Join to | |
Multicast | |
Groups | |
| |----------HI--------->|
| | (Multicast MobOpt) |
| |<-------HAck----------|
| | (Multicast AckOpt) |
| | |
| |(HI/HAck if necessary)|
| | |
| FBack, optional |
| packet forwarding ==========>|
| | |
|<=================================== deliver packets
| |
]]></artwork>
</figure>
</section>
<section anchor="PFMIPv6-overview"
title="Protocol Operations Specific to PFMIPv6">
<t>In a proxy mobile IPv6 environment, the MN remains agnostic of
network layer changes, and fast handover procedures are operated by
the access routers or MAGs. The handover initiation, or the
re-association respectively are managed by the access networks.
Consequently, access routers need to be aware of multicast membership
state at the mobile node. There are two ways to obtain the multicast
membership of an MN. First, MAGs may perform explicit tracking (see
<xref target="RFC4605"></xref>, <xref target="RFC6224"></xref>) or
extract membership status from forwarding states at node-specific
point-to-point links. Second, routers can issue a general MLD query at
handovers. Both methods are equally applicable. However, a router that
does not operate explicit tracking needs to query its downstream links
after a handover. The MLD membership information then allows the PAR
to know the multicast group subscriptions of the MN.</t>
<t>In predictive mode, the PMAG (PAR) will learn about the upcoming
movement of the mobile node. Without explicit tracking, it will
immediately submit a general MLD query and receive MLD reports for the
subscribed group(s). As displayed in <xref
target="pfmip-pred"></xref>, it will initiate binding and context
transfer with the NMAG (NAR) by issuing a HI message that is augmented
by multicast contexts in the mobility options defined in <xref
target="multicast-option"></xref>. NAR will extract multicast context
information and act as described in <xref
target="AR-context-transfer"></xref>.</t>
<figure anchor="pfmip-pred"
title="Predictive Multicast Handover for PFMIPv6">
<artwork><![CDATA[
PMAG NMAG
MN P-AN N-AN (PAR) (NAR)
| | | | |
| Report | | | |
|---(MN ID,-->| | | |
| New AP ID) | | | |
| | HO Indication | |
| |--(MN ID, New AP ID)-->| |
| | | | |
| | | Optional: |
| | | MLD Query |
| | | | |
| | | |------HI---->|
| | | |(Multicast MobOpt)
| | | | |
| | | |<---HAck-----|
| | | |(Multicast AckOpt)
| | | | |
| | | | Join to
| | | | Multicast
| | | | Groups
| | | | |
| | | |HI/HAck(optional)
| | | |<- - - - - ->|
| | | | |
| | | optional packet |
| | | forwarding =======>|
disconnect | | | |
| | | | |
connect | | | |
| MN-AN connection | AN-MAG connection |
|<----establishment----->|<----establishment------->|
| | | (substitute for UNA) |
| | | | |
|<========================================== deliver packets
| | | | |
]]></artwork>
</figure>
<t>In reactive mode, the NMAG (NAR) will learn the attachment of the
MN to the N-AN and establish connectivity using the PMIPv6 protocol
operations. However, it will have no knowledge about multicast state
at the MN. Triggered by a MN attachment, the NMAG will send a general
MLD query and thereafter join the requested groups. In the case of a
reactive handover, the binding is initiated by the NMAG, and the
HI/HACK message semantic is inverted (see <xref
target="RFC5949"></xref>). For multicast context transfer, the NMAG
attaches to its HI message those group identifiers it requests to be
forwarded from PMAG. Using the identical syntax in its multicast
mobility option headers as defined in <xref
target="multicast-ack"></xref>, the PMAG acknowledges the set of
requested groups in a HACK answer, indicating the group(s) it is
willing to forward . The corresponding call flow is displayed in <xref
target="pfmip-react"></xref>.</t>
<figure anchor="pfmip-react"
title="Reactive Multicast Handover for PFMIPv6">
<artwork><![CDATA[
PMAG NMAG
MN P-AN N-AN (PAR) (NAR)
| | | | |
disconnect | | | |
| | | | |
connect | | | |
| | | | |
| MN-AN connection | AN-MAG connection |
|<---establishment---->|<----establishment------->|
| | |(substitute for UNA & FBU)|
| | | | |
| | | | MLD Query
| | | | |
| | | | Join to
| | | | Multicast
| | | | Groups
| | | |
| | | |<------HI----|
| | | |(Multicast MobOpt)
| | | | |
| | | |---HAck----->|
| | | |(Multicast AckOpt)
| | | | |
| | | | |
| | | |HI/HAck(optional)
| | | |<- - - - - ->|
| | | | |
| | | optional packet |
| | | forwarding =======>|
| | | | |
|<======================================== deliver packets
| | | | |
]]></artwork>
</figure>
<t></t>
</section>
</section>
<section title="Protocol Details">
<t>In this section the protocol operations are defined in a normative
way.</t>
<section title="Protocol Operations Specific to FMIPv6">
<t></t>
<section title="Operations of the Mobile Node">
<t>A Mobile Node willing to manage multicast traffic by fast
handover operations MUST inform about its MLD listener state records
within the process of handover signaling.</t>
<t>When sensing a handover in predictive mode, an MN MUST build a
Multicast Mobility Option as described in <xref
target="multicast-option"></xref> that contains the MLD (IGMP)
multicast listener state and append it to the Fast Binding Update
(FBU) prior to signaling with PAR. It will receive the Multicast
Acknowledgement Option(s) as part of Fast Binding Acknowledge
(FBack) (see <xref target="multicast-ack"></xref>) and learn about
unsupported or prohibited groups at the NAR. The MN MAY take
appropriate actions like home tunneling to bridge missing multicast
services in the new access network. No multicast-specific operation
is required by the MN when re-attaching in the new network besides
standard FMIPv6 signaling.</t>
<t>In reactive mode, the MN MUST append the identical Multicast
Mobility Option to FBU sent after its reconnect. In response, it
will learn about the Multicast Acknowledgement Option(s) from FBACK
and expect corresponding multicast data. Concurrently it joins all
subscribed multicast groups (channels) directly on its newly
established access link.</t>
</section>
<section title="Operations of the Previous Access Router">
<t>A PAR MUST advertise its multicast support by setting the M-bit
in PrRtAdv.</t>
<t>In predictive mode, a PAR will receive the multicast listener
state of an MN prior to handover from the Multicast Mobility Option
appended to the FBU. It forwards these records to NAR within HI
messages and will expect Multicast Acknowledgement Option(s) in
HACK, which itself is returned to the MN as an appendix to FBACK. In
performing multicast context exchange, the PAR is instructed to
include the PAR-to-NAR tunnel obtained from unicast handover
management in its multicast downstream interfaces and await MLD
listener reports from NAR. In response to receiving multicast
subscriptions, PAR SHOULD normally forward group data acting as a
regular multicast router or proxy. However, PAR MAY refuse to
forward some or all of the multicast flows (e.g., due to
administrative configurations or load conditions).</t>
<t>In reactive mode, PAR will receive the FBU augmented by the
Multicast Mobility Option from the new network, but continues with
an identical multicast record exchange in the HI/HACk dialog. As in
the predictive case, it configures the PAR-to-NAR tunnel for
multicast downstream and SHOULD forward data according to MLD
reports obtained from NAR, if capable of forwarding.</t>
<t>In both modes, PAR SHOULD interpret the first of the two events -
the departure of the MN or the reception of the Multicast
Acknowledgement Option(s) - as a multicast LEAVE message of the MN
and react according to the signaling scheme deployed in the access
network (i.e., MLD querying, explicit tracking).</t>
</section>
<section title="Operations of the New Access Router">
<t>NAR MUST advertise its multicast support by setting the M-bit in
PrRtAdv.</t>
<t>In predictive mode, a NAR will receive the multicast listener
state of an expected MN from the Multicast Mobility Option appended
to the HI message. It will extract the MLD/IGMP records from the
message and intersect the request subscription with its multicast
service offer. Further on it will adjoin the supported groups
(channels) to the MLD listener state using loopback as downstream
interface. This will lead to suitable regular subscriptions on its
native multicast upstream interface without additional forwarding.
Concurrently, NAR builds a Multicast Acknowledgement Option(s) (see
<xref target="multicast-ack"></xref>) listing those groups
(channels) unsupported on the new access link and returns them
within HACK. As soon as the bidirectional tunnel from PAR to NAR is
operational, NAR joins the groups subscribed for forwarding on the
tunnel link.</t>
<t>In reactive mode, NAR will learn about the multicast listener
state of a new MN from the Multicast Mobility Option appended to HI
at a time, when the MN has already performed local subscriptions of
the multicast service. Thus NAR solely determines the intersection
of requested and supported groups (channels) and issues the join
requests for group forwarding on the PAR-NAR tunnel interface.</t>
<t>In both modes, NAR MUST send a LEAVE message to the tunnel
immediately after forwarding of a group (channel) becomes unneeded,
e.g., after native multicast traffic arrives or group membership of
the MN terminates.</t>
</section>
<section title="Buffering Considerations">
<t>Multicast packets may be lost during handover. For example, in
predictive mode as illustrated by figure 2, packets may be lost
while the MN is - already or still - detached from the networks,
even though they are forwarded to NAR. In reactive mode as
illustrated by figure 3, the situation may be worse since there will
be a delay for joining the multicast group after the MN re-attaches
to the NAR. Multicast packets cannot be delivered during this time.
Buffering the multicast packets at the PAR can ease the multicast
packet loss problem, but may increase resource consumption and delay
in packet transmission. Implementors should carefully balance the
different requirements in the context of predominant application
demands (e.g., real-time requirements).</t>
</section>
</section>
<section anchor="det-pfmipv6"
title="Protocol Operations Specific to PFMIPv6">
<t></t>
<section title="Operations of the Mobile Node">
<t>A Mobile Node willing to participate in multicast traffic will
join, maintain and leave groups as if located in the fixed Internet.
It will cooperate in handover indication as specified in <xref
target="RFC5949"></xref> and required by its access link-layer
technology. No multicast-specific mobility actions nor
implementations are required at the MN in a PMIPv6 domain.</t>
</section>
<section title="Operations of the Previous MAG">
<t>A MAG receiving a handover indication for one of its MNs follows
the predictive fast handover mode as a PMAG. It MUST issue an MLD
General Query immediately on its corresponding link unless it
performs an explicit tracking on that link. After knowledge of the
multicast subscriptions of the MN is acquired, the PMAG builds a
Multicast Mobility Option as described in <xref
target="multicast-option"></xref> that contains the MLD (IGMP)
multicast listener state. If not empty, this Mobility Option is
appended to the regular fast handover HI messages, or - in the case
of unicast HI message being submitted prior to multicast state
detection - sent in an additional HI message to the NMAG. PMAG then
waits for receiving the Multicast Acknowledgement Option(s) with
HACK (see <xref target="multicast-ack"></xref>) and the creation of
the bidirectional tunnel with NMAG. After HACK is received, the PMAG
adds the tunnel to its downstream interfaces in the multicast
forwarding database. For those groups (channels) reported in the
Multicast Acknowledgement Option(s), i.e., not supported in the new
access network, PMAG normally takes appropriate actions (e.g.,
forwarding, termination) in concordance with the network policy. It
SHOULD start forwarding traffic down the tunnel interface for those
groups an MLD listener report was received from NMAG. However, it
MAY deny forwarding service. After the departure of the MN and on
the reception of LEAVE messages for groups/channels, PMAG MUST
terminate forwarding of the specific groups and update its multicast
forwarding database. Correspondingly it issues a group/channel LEAVE
to its upstream link, if no more listeners are present on its
downstream links.</t>
<t>A MAG receiving a HI message with Multicast Mobility Option for a
currently attached node follows the reactive fast handover mode as a
PMAG. It will return Multicast Acknowledgement Option(s) (see <xref
target="multicast-ack"></xref>) within HACK listing those
groups/channels it does not support to forward to the NMAG. It will
add the bidirectional tunnel with NMAG to its downstream interfaces
and will start forwarding multicast traffic for those groups it
receives an MLD listener report message from NMAG. At the reception
of LEAVE messages for groups (channels), PMAG MUST terminate
forwarding of the specific groups and update its multicast
forwarding database. According to its multicast forwarding state, it
MAY need to issue a group/channel LEAVE to its upstream link, if no
more listeners are present on its downstream links.</t>
<t>In both modes, PMAG will interpret the departure of the MN as a
multicast LEAVE message of the MN and react according to the
signaling scheme deployed in the access network (i.e., MLD querying,
explicit tracking).</t>
</section>
<section title="Operations of the New MAG">
<t>A MAG receiving a HI message with Multicast Mobility Option for a
currently unattached node follows the predictive fast handover mode
as NMAG. It will decide on those multicast groups/channels it
selects to be forwarded from the PMAG and builds a Multicast
Acknowledgement Option (see <xref target="multicast-ack"></xref>)
that enumerates only unwanted groups/channels. This Mobility Option
is appended to the regular fast handover HACK messages, or - in the
case of unicast HACK message being submitted prior to multicast
state acknowledgement - sent in an additional HACK message to the
PMAG. Immediately thereafter, NMAG SHOULD update its MLD listener
state by the new groups/channels obtained from the Multicast
Mobility Option. Until the MN re-attaches, NMAG uses its loopback
interface for downstream and MUST not forward traffic to the
potential link of the MN. NMAG SHOULD issue JOIN messages for those
newly selected groups to its regular multicast upstream interface.
As soon as the bidirectional tunnel with PMAG is established, NMAG
additionally joins those groups/channels on the tunnel interface
that it wants to receive forwarded from PMAG. NMAG MUST send a LEAVE
message to the tunnel immediately after the forwarding of a
group/channel becomes unneeded, e.g., after native multicast traffic
arrives or group membership of the MN terminates.</t>
<t>A MAG experiencing a connection request for an MN without prior
reception of a corresponding Multicast Mobility Option is operating
in the reactive fast handover mode as NMAG. Following the
re-attachment, it immediately issues an MLD General Query to learn
about multicast subscriptions of the newly arrived MN. Using
standard multicast operations, NMAG joins the missing groups
(channels) on its regular multicast upstream interface.
Concurrently, it selects groups (channels) for forwarding from PMAG
and builds a Multicast Mobility Option as described in <xref
target="multicast-option"></xref> that contains the MLD (IGMP)
multicast listener state. If not empty, this Mobility Option is
appended to the regular fast handover HI messages with the F flag
set, or - in the case of unicast HI message being submitted prior to
multicast state detection - sent in an additional HI message to the
PMAG. Upon reception of the Multicast Acknowledgement Option and
establishment of the bidirectional tunnel, NMAG additionally joins
those groups/channels on the tunnel interface that it wants to
receive by forwarding from PMAG. When multicast flows arrive, the
NMAG forwards data to the appropriate downlink(s). NMAG MUST send a
LEAVE message to the tunnel immediately after forwarding of a
group/channel becomes obsolete, e.g., after native multicast traffic
arrives or group membership of the MN terminates.</t>
</section>
<section anchor="det-IPv4" title="IPv4 Support Considerations">
<t>An MN in a PMIPv6 domain MAY use an IPv4 address transparently
for communication as specified in <xref target="RFC5844"></xref>.
For this purpose, LMAs can register IPv4-Proxy-CoAs in its Binding
Caches and MAGs can provide IPv4 support in access networks.
Correspondingly, multicast membership management will be performed
by the MN using IGMP. For multi-protocol multicast support on the
network side, IGMPv3 router functions are required at both MAGs (see
<xref target="MLD-compat"></xref> for compatibility considerations
with previous IGMP versions). Context transfer between MAGs can
transparently proceed in HI/HACK message exchanges by encapsulating
IGMP multicast state records within Multicast Mobility Options (see
<xref target="multicast-option"></xref> and <xref
target="multicast-ack"></xref> for details on message formats).</t>
<t>The deployment of IPv4 multicast support SHOULD be homogeneous
across a PMIP domain, as network services break across handovers,
otherwise.</t>
<t>It is worth mentioning the scenarios of a dual-stack IPv4/IPv6
access network, and the use of GRE tunneling as specified in<xref
target="RFC5845"></xref>. Corresponding implications and operations
are discussed in the PMIP Multicast Base Deployment document,
see<xref target="RFC6224"></xref>.</t>
</section>
</section>
</section>
<section title="Message Formats">
<t></t>
<section anchor="m-prtrtadv"
title="Multicast Indicator for Proxy Router Advertisement (PrRtAdv)">
<t>An FMIPv6 AR will indicate its multicast support by activating the
M-bit in its Proxy Router Advertisements (PrRtAdv). The message
extension has the following format.</t>
<figure anchor="fig-m-PrRtAdv"
title="Multicast Indicator Bit for Proxy Router Advertisement (PrRtAdv) Message">
<artwork><![CDATA[ 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subtype |M| Reserved | Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
]]></artwork>
</figure>
<t></t>
</section>
<section anchor="m-mobheader"
title="Extensions to Existing Mobility Header Messages">
<t>The fast handover protocols use a new IPv6 header type called
Mobility Header as defined in <xref target="RFC6275"></xref>. Mobility
headers can carry variable Mobility Options.</t>
<t>Multicast Listener context of an MN is transferred in fast handover
operations from PAR/PMAG to NAR/NMAG within a new Multicast Mobility
Option, and MUST be acknowledged by a corresponding Acknowledgement
Option. Depending on the specific handover scenario and protocol in
use, the corresponding option is included within the mobility option
list of HI/HAck only (PFMIPv6), or of FBU/FBAck/HI/HAck (FMIPv6).</t>
</section>
<section anchor="multicast-option" title="New Multicast Mobility Option">
<t>This section defines the Multicast Mobility Option. It contains the
current listener state record of the MN obtained from the MLD Report
message, and has the format displayed in <xref
target="mcast-mobopt"></xref>.</t>
<figure anchor="mcast-mobopt" title="Mobility Header Multicast Option">
<artwork><![CDATA[ 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 | Option-Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ MLD (IGMP) Report Payload +
~ ~
~ ~
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t></t>
<t>RFC Editor note: IANA is requested to allocate the value XXX and
remove this note prior to publication.</t>
<t>Type: XXX</t>
<t>Length: 8-bit unsigned integer. The size of this option is 8 octets
including the Type, Option-Code, and Length fields.</t>
<t><list style="hanging">
<t hangText="Option-Code:"><list style="hanging">
<t hangText="1:">IGMPv3 Payload Type</t>
<t hangText="2:">MLDv2 Payload Type</t>
<t hangText="3:">IGMPv3 Payload Type from IGMPv2 Compatibility
Mode</t>
<t hangText="4:">MLDv2 Payload Type from MLDv1 Compatibility
Mode</t>
</list></t>
</list>Reserved: MUST be set to zero by the sender and MUST be
ignored by the receiver.</t>
<t>MLD (IGMP) Report Payload: this field is composed of the MLD (IGMP)
Report message after stripping its ICMP header. Corresponding message
formats are defined for MLDv2 in <xref target="RFC3810"></xref>, and
for IGMPv3 in <xref target="RFC3376"></xref>.</t>
<t><xref target="mld-payload"></xref> shows the Report Payload for
MLDv2, while the payload format for IGMPv3 is defined corresponding to
the IGMPv3 payload format (see Section 5.2. of <xref
target="RFC3810"></xref>, or Section 4.2 of <xref
target="RFC3376"></xref>) for the definition of Multicast Address
Records).</t>
<figure anchor="mld-payload" title="MLDv2 Report Payload">
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |No of Mcast Address Records (M)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | . .
. Multicast Address Record [1] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Multicast Address Record [2] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
. . .
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Multicast Address Record [M] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</section>
<section anchor="multicast-ack"
title="New Multicast Acknowledgement Option">
<t>The Multicast Acknowledgement Option reports the status of the
context transfer and contains the list of state records that could not
be successfully transferred to the next access network. It has the
format displayed in <xref target="mcast-AckOpt"></xref>.</t>
<figure anchor="mcast-AckOpt"
title="Mobility Header Multicast Acknowledgement Option">
<artwork><![CDATA[ 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 | Option-Code | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ MLD (IGMP) Unsupported Report Payload +
~ ~
~ ~
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t></t>
<t>RFC Editor note: IANA is requested to allocate the value XXX and
remove this note prior to publication.</t>
<t>Type: XXX</t>
<t>Length: 8-bit unsigned integer. The size of this option in 8
octets. The length is 1 when the MLD (IGMP) Unsupported Report Payload
field contains no Mcast Address Record.</t>
<t>Option-Code: 0</t>
<t><list style="hanging">
<t hangText="Status:"><list style="hanging">
<t hangText="1:">Report Payload type unsupported</t>
<t hangText="2:">Requested group service unsupported</t>
<t hangText="3:">Requested group service administratively
prohibited</t>
</list></t>
</list>Reserved: MUST be set to zero by the sender and MUST be
ignored by the receiver.</t>
<t>MLD (IGMP) Unsupported Report Payload: this field is syntactically
identical to the MLD (IGMP) Report Payload field described in <xref
target="multicast-option"></xref>, but is only composed of those
multicast address records that are not supported or prohibited in the
new access network. This field MUST always contain the first header
line (reserved field and No of Mcast Address Records), but MUST NOT
contain any Mcast Address Records, if the status code equals 1.</t>
<t>Note that group subscriptions to specific sources may be rejected
at the destination network, and thus the composition of multicast
address records may differ from initial requests within an MLD (IGMP)
Report Payload option.</t>
</section>
<section anchor="number-of-addresses"
title="Length Considerations: Number of Records and Addresses">
<t>Mobility Header Messages exchanged in HI/HACK and FBU/FBACK dialogs
impose length restrictions on multicast context records. The maximal
payload length available in FBU/FBACK messages is the PATH-MTU - 40
octets (IPv6 Header) - 6 octets (Mobility Header) - 6 octets
(FBU/FBACK Header). For example, on an Ethernet link with an MTU of
1500 octets, not more than 72 Multicast Address Records of minimal
length (without source states) may be exchanged in one message pair.
In typical handover scenarios, this number reduces further according
to unicast context and Binding Authorization data. A larger number of
MLD Reports that exceed the available payload size MAY be sent within
multiple HI/HACK or FBU/FBACK message pairs. In PFMIPv6, context
information can be fragmented over several HI/HACK messages. However,
a single MLDv2 Report Payload MUST NOT be fragmented. Hence, for a
single Multicast Address Record on an Ethernet link, the number of
source addresses (S,.) is limited to 89.</t>
</section>
<section anchor="MLD-compat"
title="MLD (IGMP) Compatibility Requirements">
<t>Access routers (MAGs) MUST support MLDv2 (IGMPv3). To enable
multicast service for MLDv1 (IGMPv2) listeners, the routers MUST
follow the interoperability rules defined in <xref
target="RFC3810"></xref> (<xref target="RFC3376"></xref>) and
appropriately set the Multicast Address Compatibility Mode.</t>
<t>When the Multicast Address Compatibility Mode is MLDv1 (IGMPv2), a
router internally translates the following MLDv1 (IGMPv2) messages for
that multicast address to their MLDv2 (IGMPv2) equivalents and uses
these messages in the context transfer. The current state of
Compatibility Mode is translated into the code of the Multicast
Mobility Option as defined in <xref target="multicast-option"></xref>.
A NAR (nMAG) receiving a Multicast Mobility Option during handover
will switch to the lowest level of MLD (IGMP) Compatibility Mode that
it learned from its previous and new option values. This minimal
compatibility agreement is used to allow for continued operation.</t>
</section>
</section>
<section title="Security Considerations">
<t>Security vulnerabilities that exceed issues discussed in the base
protocols of this document (<xref target="RFC5568"></xref>, <xref
target="RFC5949"></xref>, <xref target="RFC3810"></xref>, <xref
target="RFC3376"></xref>) are identified as follows.</t>
<t>Multicast context transfer at predictive handovers implements group
states at remote access routers and may lead to group subscriptions
without further validation of the multicast service requests. Thereby a
NAR (nMAG) is requested to cooperate in potentially complex multicast
re-routing and may receive large volumes of traffic. Malicious or
inadvertent multicast context transfers may result in a significant
burden of route establishment and traffic management onto the backbone
infrastructure and the access router itself. Rapid re-routing or traffic
overload can be mitigated by a rate control at the AR that restricts the
frequency of traffic redirects and the total number of subscriptions. In
addition, the wireless access network remains protected from multicast
data injection until the requesting MN attaches to the new location.</t>
</section>
<section title="IANA Considerations">
<t>This document defines new flags and status codes in the HI and HAck
messages as well as two new mobility options. The Type values for these
mobility options are assigned from the same numbering space as allocated
for the other mobility options defined in <xref
target="RFC6275"></xref>. Those for the flags and status codes are
assigned from the corresponding numbering space defined in <xref
target="RFC5568"></xref>, or <xref target="RFC5949"></xref> and
requested to be created as new tables in the IANA registry (marked with
asterisks). New values for these registries can be allocated by
Standards Action or IESG approval <xref target="RFC5226"></xref>.</t>
</section>
<section title="Acknowledgments">
<t>Protocol extensions to support multicast in Fast Mobile IPv6 have
been loosely discussed for several years. Repeated attempts have been
taken to define corresponding protocol extensions. The first draft <xref
target="fmcast-mip6"></xref> was presented by Suh, Kwon, Suh, and Park
in 2004.</t>
<t>This work was stimulated by many fruitful discussions in the MobOpts
research group. We would like to thank all active members for
constructive thoughts and contributions on the subject of multicast
mobility. Comments, discussions and reviewing remarks have been
contributed by (in alphabetical order) Carlos J. Bernardos, Luis M.
Contreras, Shuai Gao, Dirk von Hugo, Georgios Karagian, Marco Liebsch,
Behcet Sarikaya, Stig Venaas and Juan Carlos Zuniga.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.6275"?>
<?rfc include="reference.RFC.5213"?>
<?rfc include="reference.RFC.5568"?>
<?rfc include="reference.RFC.5949"?>
<?rfc include="reference.RFC.1112"?>
<?rfc include="reference.RFC.4605"?>
<?rfc include="reference.RFC.3810"?>
<?rfc include="reference.RFC.3376"?>
<?rfc include="reference.RFC.5226"?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.5757"?>
<reference anchor="fmcast-mip6">
<front>
<title>Fast Multicast Protocol for Mobile IPv6 in the fast handovers
environments</title>
<author initials="K." surname="Suh">
<organization>Samsung Electronics</organization>
</author>
<author initials="D." surname="Kwon">
<organization>Postech</organization>
</author>
<author initials="Y." surname="Suh">
<organization>Postech</organization>
</author>
<author initials="Y." surname="Park">
<organization>Samsung Electronics</organization>
</author>
<date month="July" year="2004" />
</front>
<seriesInfo name="Internet-Draft"
value="draft-suh-mipshop-fmcast-mip6-00" />
<format target="http://tools.ietf.org/html/draft-suh-mipshop-fmcast-mip6-00"
type="TXT" />
</reference>
<reference anchor="FMIPv6-Analysis">
<front>
<title>Predictive versus Reactive - Analysis of Handover Performance
and Its Implications on IPv6 and Multicast Mobility</title>
<author initials="TC." surname="Schmidt">
<organization>HAW Hamburg</organization>
</author>
<author initials="M." surname="Waehlisch">
<organization>link-lab</organization>
</author>
<date month="November" year="2005" />
</front>
<seriesInfo name="Telecommunication Systems"
value="Vol 33, No. 1-3, pp. 131-154" />
<format target="http://dx.doi.org/10.1007/s11235-005-4321-4"
type="PDF" />
</reference>
<?rfc include="reference.RFC.6224"?>
<?rfc include="reference.I-D.ietf-multimob-pmipv6-source"?>
<?rfc include="reference.RFC.5844"?>
<?rfc include="reference.RFC.5845"?>
</references>
<section title="Change Log ">
<t>The following changes have been made from
draft-ietf-multimob-fmipv6-pfmipv6-multicast-02.<list style="numbers">
<t>Design requirements and motoviation section added in response to
WG feedback.</t>
<t>Clarifications according to WG feedback. </t>
<t>Several editorial improvements.</t>
<t>Updated references.</t>
</list></t>
<t>The following changes have been made from
draft-ietf-multimob-fmipv6-pfmipv6-multicast-01.<list style="numbers">
<t>Several editorial improvements.</t>
<t>Updated references.</t>
</list></t>
<t>The following changes have been made from
draft-ietf-multimob-fmipv6-pfmipv6-multicast-00.<list style="numbers">
<t>Buffering text added from new co-author Dapeng.</t>
<t>Several editorial improvements.</t>
</list>The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-04. <list
style="numbers">
<t>Following working group feedback, multicast traffic forwarding is
now a two-sided option between PAR (PMAG) and NAR (NMAG): Either
access router can decide on its contribution to the data plane.</t>
<t>Several editorial improvements.</t>
</list></t>
<t>The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-03. <list
style="numbers">
<t>References updated.</t>
</list></t>
<t>The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-02. <list
style="numbers">
<t>Detailed operations on PFMIPv6 entities completed.</t>
<t>Some editorial improvements & clarifications.</t>
<t>References updated.</t>
</list></t>
<t>The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-01. <list
style="numbers">
<t>First detailed operations on PFMIPv6 added.</t>
<t>IPv4 support considerations for PFMIPv6 added.</t>
<t>Section on length considerations for multicast context records
corrected.</t>
<t>Many editorial improvements & clarifications.</t>
<t>References updated.</t>
</list></t>
<t>The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-00. <list
style="numbers">
<t>Editorial improvements & clarifications.</t>
<t>Section on length considerations for multicast context records
added.</t>
<t>Section on MLD/IGMP compatibility aspects added.</t>
<t>Security section added.</t>
</list></t>
</section>
</back>
</rfc>
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