One document matched: draft-schmidt-multimob-fmipv6-pfmipv6-multicast-02.xml
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<rfc category="std"
docName="draft-schmidt-multimob-fmipv6-pfmipv6-multicast-02"
ipr="trust200902">
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<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." 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>
<date day="06" month="September" year="2010" />
<abstract>
<t>Fast handover protocols for MIPv6 and PMIPv6 define mobility
management procedures that support unicast communication at reduced
handover latencies. 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.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Mobile IPv6 <xref target="RFC3775"></xref> defines a network layer
mobility protocol involving mobile nodes participation, 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 application scenarios. Mobile IPv6 Fast Handovers
(FMIPv6) <xref target="RFC5568"></xref>, and Fast Handovers for Proxy
Mobile IPv6 (PFMIPv6) <xref target="I-D.ietf-mipshop-pfmipv6"></xref>
improve these handover delays for unicast communication to the order of
the maximum delay 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 reception 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="I-D.ietf-multimob-pmipv6-base-solution"></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 of FMIPv6 and PFMIPv6 for
including multicast traffic management in fast handover operations. The
solution common to both underlying 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>This specification is applicable 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>
<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="I-D.ietf-mipshop-pfmipv6"></xref>, <xref
target="RFC3775"></xref>, and <xref target="RFC5213"></xref>. In
addition, the following terms are introduced:</t>
</section>
<section title="Protocol Overview">
<t></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 MN's forthcoming move to a new AR and
assist the MN to immediately resume communication on the new subnet
link using its previous IP address. In contrast to unicast, multicast
stream 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 take the
twofold advantage of including the multicast groups under subscription
in context transfer. First, the NAR can proactively join the desired
groups as soon as it gains knowledge of them. Second, multicast
streams may 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 (e.g., PAR 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, PAR will initiate an
AR-binding and context transfer by transmitting a HI message to NAR.
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, as well as its willingness to receive multicast
traffic forwarded from PAR (see <xref target="multicast-ack"></xref>).
There are several reasons to waive forwarding, e.g., the group may
already be under native subscription or capacity constraints may
hinder decapsulation of additional streams at the NAR. For the groups
requested, PAR will add the tunnel interface to its multicast
forwarding database, so that multicast streams are forwarded in
parallel to unicast traffic. NAR, taking the role of an MLD proxy
<xref target="RFC4605"></xref> with the upstream tunnel interface to
PAR, will submit an MLD report to request the desired groups, but will
terminate multicast forwarding <xref target="RFC3810"></xref> from
PAR, as soon as group traffic natively arrives. In addition, NAR
immediately joins all groups that are not already under subscription
using its loopback interface, and starts downstream multicast
forwarding after the MN has arrived.</t>
<t>In a reactive fast handover, 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 are
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 though, 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 react on the departure of the MN in the context of
local group management. Depending on the multicast state management,
link type and MLD parameters deployed (cf., <xref
target="RFC5757"></xref>), it is requested to take appropriate actions
to adjust multicast service to requirements of the remaining
nodes.</t>
<t>In this way, the MN will be able to participate in multicast group
communication with a handover performance comparable to that for
unicast, while network resources consumption is minimized.</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, FBU is issued on the previous link and received
by PAR as displayed in <xref target="fmip-pred"></xref>. 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 FBACK, the MN will learn about a per
group multicast support in the new access network. If some groups or a
multicast flavour are not supported, it may decide on taking actions
to compensate the missing service. 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 forward |
| packets ===============>|
| | |
| | |
connect | |
| | |
|------------UNA --------------------------->|
|<=================================== deliver packets
| |
]]></artwork>
</figure>
<t>The call flow 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 NAR forwards to PAR without processing. At this
time, the MN is able to re-join all desired multicast groups without
relying on AR assistance. Nevertheless, multicast context options are
exchanged in the HI/HACK dialog to facilitate intermediate forwarding
of requested streams. Note that group traffic may already arrive from
a MN's subscription at the time NAR receives the HI message. Such
streams may be transparently excluded from forwarding by setting an
appropriate multicast acknowledge option. In any case, NAR MUST ensure
that not more than one stream 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)|
| | |
| forward |
| packets(including FBack)=====>|
| | |
|<=================================== 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 record of MN's
multicast membership. First, MAGs MAY perform an explicit tracking
(cf., <xref target="RFC4605"></xref>, <xref
target="I-D.ietf-multimob-pmipv6-base-solution"></xref>) or extract
membership status from forwarding states at node-specific
point-to-point links. Second, routers can perform general queries at
handovers. Both methods are equally applicable. However, a router that
does not do explicit tracking MUST query its downstream links
subsequent to handovers. In either case, the PAR will become
knowledgeable about 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 learn about the multicast
groups under subscription. 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)
| | | |<- - - - - ->|
| | | | |
| | | forward |
| | | packets =======>|
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 about MN's attachment
to the N-AN and establish connectivity by means of 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 NMAG, and the HI/HACK
message semantic is inverted (see <xref
target="I-D.ietf-mipshop-pfmipv6"></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>, PMAG acknowledges the group forwarding
request in its HACK answer. 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)
| | | |<- - - - - ->|
| | | | |
| | | forward |
| | | packets =======>|
| | | | |
|<======================================== deliver packets
| | | | |
]]></artwork>
</figure>
<t></t>
</section>
</section>
<section title="Protocol Details">
<t></t>
<section title="Common Protocol Operations ">
<t>:::TODO:</t>
</section>
<section title="Protocol Operations Specific to FMIPv6">
<t></t>
<section title="Operations of the Mobile Node">
<t></t>
</section>
<section title="Operations of the Previous Access Router">
<t></t>
</section>
<section title="Operations of the New Access Router">
<t></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 manage 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="I-D.ietf-mipshop-pfmipv6"></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 a general
MLD Query immediately on its corresponding link unless it performs
an explicit tracking on that link. After gaining knowledge of the
multicast subscriptions of the MN, the PMAG builds a Multicast
Mobility Option as described in <xref
target="multicast-option"></xref> that contains the MLD (IGMP)
multicast listener state. 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 with HACK (see <xref
target="multicast-ack"></xref>) and the creation of the
bidirectional tunnel with NMAG. Thereafter PMAG will add the tunnel
to its downstream interfaces in the multicast forwarding database.
For those groups (channels) reported in the Multicast
Acknowledgement Option, i.e., not supported in the new access
network, PMAG 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 it
receives an MLD listener report message from NAR. 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 a Multicast Acknowledgement Option (see <xref
target="multicast-ack"></xref>) within HACK listing those
groups/channels it is not willing to support or forward to NMAG. It
will add the bidirectional tunnel with NMAG to its downstream
interfaces and will start forwarding multicast traffic. 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 states it
MAY need to issue a group/channel LEAVE to its upstream link if no
more listeners are present on its downstream links.</t>
</section>
<section title="Operations of the New MAG">
<t></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 multiprotocol 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>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, cf.,
<xref target="I-D.ietf-multimob-pmipv6-base-solution"></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="RFC3775"></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 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>The Multicast Mobility Option 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>Type: TBD</t>
<t>Length: 8-bit unsigned integer. The size of this option in 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>Type: TBD</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 Report Payloads 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 is limited to 89.</t>
</section>
<section anchor="MLD-compat" title="MLD (IGMP) Compatibility Aspects">
<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. 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 minimum obtained from its previous and newly learned value of MLD
(IGMP) Compatibility Mode 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="I-D.ietf-mipshop-pfmipv6"></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="RFC3775"></xref>. Those for the flags and status codes are
assigned from the corresponding numbering space defined in <xref
target="RFC5568"></xref>, or <xref
target="I-D.ietf-mipshop-pfmipv6"></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 since 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
already 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.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.3775"?>
<?rfc include="reference.RFC.5213"?>
<?rfc include="reference.RFC.5568"?>
<?rfc include="reference.I-D.ietf-mipshop-pfmipv6"?>
<?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.I-D.ietf-multimob-pmipv6-base-solution"?>
<?rfc include="reference.RFC.5844"?>
<?rfc include="reference.RFC.5845"?>
</references>
<section title="Change Log ">
<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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