MULTIMOB Group T. Schmidt, Ed.
Internet-Draft HAW Hamburg
Updates: 5568 (if approved) M. Waehlisch
Intended status: Experimental link-lab & FU Berlin
Expires: November 23, 2014 R. Koodli
Intel
G. Fairhurst
University of Aberdeen
Dapeng. Liu
China Mobile
May 22, 2014
Multicast Listener Extensions for MIPv6 and PMIPv6 Fast Handovers
draft-ietf-multimob-fmipv6-pfmipv6-multicast-06
Abstract
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, comprise delay-
sensitive real-time traffic and will benefit from fast handover
completion. 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. An FMIPv6 access router
indicates support for multicast using an updated Proxy Router
Advertisements message format.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 23, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Use Cases and Deployment Scenarios . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Multicast Context Transfer between Access Routers . . . . 6
3.2. Protocol Operations Specific to FMIPv6 . . . . . . . . . 8
3.3. Protocol Operations Specific to PFMIPv6 . . . . . . . . . 10
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Protocol Operations Specific to FMIPv6 . . . . . . . . . 14
4.1.1. Operations of the Mobile Node . . . . . . . . . . . . 14
4.1.2. Operations of the Previous Access Router . . . . . . 14
4.1.3. Operations of the New Access Router . . . . . . . . . 15
4.1.4. Buffering Considerations . . . . . . . . . . . . . . 16
4.2. Protocol Operations Specific to PFMIPv6 . . . . . . . . . 16
4.2.1. Operations of the Mobile Node . . . . . . . . . . . . 16
4.2.2. Operations of the Previous MAG . . . . . . . . . . . 16
4.2.3. Operations of the New MAG . . . . . . . . . . . . . . 17
4.2.4. IPv4 Support Considerations . . . . . . . . . . . . . 18
5. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Multicast Indicator for Proxy Router Advertisement
(PrRtAdv) . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2. Extensions to Existing Mobility Header Messages . . . . . 19
5.3. New Multicast Mobility Option . . . . . . . . . . . . . . 20
5.4. New Multicast Acknowledgement Option . . . . . . . . . . 22
5.5. Length Considerations: Number of Records and Addresses . 23
5.6. MLD (IGMP) Compatibility Requirements . . . . . . . . . . 23
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6. Security Considerations . . . . . . . . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Considerations for Mobile Multicast Sources . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
Mobile IPv6 [RFC6275] defines a network layer mobility protocol
involving participation by mobile nodes, while Proxy Mobile IPv6
[RFC5213] 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) [RFC5568], and Fast Handovers for Proxy
Mobile IPv6 (PFMIPv6) [RFC5949] 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) [FMIPv6-Analysis].
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 in
[RFC5213], but are subject to current specification [RFC6224],
[I-D.ietf-multimob-pmipv6-source]. 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.
Mobile multicast protocols need to support applications such as IPTV
with high-volume content streams and allow distribution to
potentially large numbers of receivers. They should thus preserve
the multicast nature of packet distribution and approximate optimal
routing [RFC5757]. 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.
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This document specifies extensions to FMIPv6 and PFMIPv6 that include
multicast traffic management for fast handover operations in the
presence of any source or source specific multicast. The protocol
extensions were designed under the requirements that
o multicast context transfer shall be transparently included in
unicast fast handover operations
o neither unicast mobility protocols nor multicast routing shall be
modified or otherwise affected
o no active participation of MNs in PMIPv6 domains is defined.
The solution common to both underlying unicast protocols defines the
per-group or per channel transfer of multicast contexts between ARs
or MAGs. The protocol defines corresponding message extensions
necessary for carrying (*,G) or (S,G) 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.
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.
Section 5.1 of this memo updates the Proxy Router Advertisements
(PrRtAdv) message format defined in Section 6.1.2. of [RFC5568] to
allow an FMIPv6 AR to indicate support for multicast.
1.1. Use Cases and Deployment Scenarios
Multicast Extensions for Fast Handovers enable multicast services in
those domains that operate any of the unicast fast handover protocols
[RFC5568] or [RFC5949]. Typically, fast handover protocols are
activated within an operator network or within a dedicated service
installation.
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
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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.
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.
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 for example. 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.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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.
This document uses the terminology of [RFC5568], [RFC5949],
[RFC6275], and [RFC5213] for mobility entities.
3. Protocol Overview
This section provides an informative overview of the protocol
mechanisms without normative specifications.
The reference scenario for multicast fast handover is illustrated in
Figure 1. A Mobile Node is initially attached to the previous access
network (P-AN) via the Previous Access Router (PAR) or Previous
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Mobile Access Gateway (PMAG) and moves to the new access network
(N-AN) connected via a New AR (NAR) or New MAG (NMAG).
*** *** *** ***
* ** ** ** *
* *
* Multicast Cloud *
* *
* ** ** ** *
*** *** *** ***
/ \
/ \
/ \
+........../..+ +..\..........+
. +-------+-+ .______. +-+-------+ .
. | PAR |()_______)| NAR | .
. | (PMAG) | . . | (NMAG) | .
. +----+----+ . . +----+----+ .
. | . . | .
. ___|___ . . ___|___ .
. / \ . . / \ .
. ( P-AN ) . . ( N-AN ) .
. \_______/ . . \_______/ .
. | . . | .
. +----+ . . +----+ .
. | MN | ----------> | MN | .
. +----+ . . +----+ .
+.............+ +.............+
Figure 1: Reference Network for Fast Handover
3.1. Multicast Context Transfer between Access Routers
In a fast handover scenario (cf. Figure 1), 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 assists 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 [RFC5757]. To
accelerate the handover, multicast listeners may offer the twofold
advantage of including the multicast groups under subscription in the
context transfer. First, the NAR can proactively join the subscribed
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groups as soon as it gains knowledge of them. Second, multicast
flows can be included in traffic forwarding via the tunnel
established from the PAR to the NAR.
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 a NAR (NMAG). Details
of the signaling schemes differ between FMIPv6 and PFMIPv6 and are
outlined in Section 3.2 and Section 3.3.
In a predictive fast handover, the access router (i.e., PAR (PMAG) in
Figure 1) learns about the impending movement of the MN and
simultaneously about the multicast group context as specified in
Section 3.2 and Section 3.3. Thereafter, the PAR will initiate an
AR-binding and context transfer by transmitting a HI message to NAR
(NMAG). The Handover Initiation (HI) message is extended by
multicast group states carried in mobility header options as defined
in Section 5.3. On reception of the HI message, the NAR returns a
multicast acknowledgement in its Handover Acknowledgement (HACK)
answer that indicates its ability to support each requested group
(see Section 5.4). The NAR (NMAG) expresses its willingness to
receive multicast traffic forwarded by the 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 [RFC4605] providing host-side
behaviour towards the upstream PAR. The proxy will submit an MLD
report to the upstream tunnel interface to signal that it requests
the groups/channels to be forwarded. It will terminate multicast
forwarding from the tunnel when the group is natively received. In
parallel, the 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 a
downstream Loopback interface. Reception of the Join at the NAR
enables downstream native multicast forwarding of the subscribed
group(s).
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
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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.
In both modes of operation, it is the responsibility of the PAR
(PMAG) to properly apply multicast state management when an MN leaves
(i.e., to determine if it can prune the traffic for any unsubscribed
group). Depending on the link type and MLD parameter settings,
methods for observing the departure of an MN need to be applied (cf.,
[RFC5757]). 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.
This method allows an MN to participate in multicast group
communication with a handover performance that is comparable to
unicast handover.
3.2. Protocol Operations Specific to FMIPv6
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 Section 5.1. Additional details about the
multicast service support, e.g., flavors and groups, will be
exchanged within HI/HACK dialogs later at handover.
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 Section 5.3) to the FBU, and
thereby inform ARs about its multicast context. ARs will use these
multicast context options for inter-AR context transfer.
In predictive mode, the FBU is issued on the previous link and
received by the PAR as displayed in Figure 2. 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
Fast Binding ACK (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
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context transfer may proceed successfully, even if the MN misses the
FBACK message on the previous link.
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
| |
Figure 2: Predictive Multicast Handover for FMIPv6
The flow diagram for reactive mode is depicted in Figure 3. 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.
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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
| |
Figure 3: Reactive Multicast Handover for FMIPv6
3.3. Protocol Operations Specific to PFMIPv6
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 to which MNs are connected via node-
specific point-to-point links. 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.
o MAGs may perform explicit tracking (see [RFC4605], [RFC6224]) or
extract membership status from forwarding states at node-specific
links.
o routers can issue a general MLD query at handovers. Both methods
are equally applicable. However, a router that does not operate
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explicit tracking needs to query its downstream links after a
handover. The MLD membership information then allows the PMAG
(PAR) to learn the multicast group/channel subscriptions of the
MN.
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 Figure 4, 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 Section 5.3. NAR will extract multicast context
information and act as described in Section 3.1.
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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
| | | | |
Figure 4: Predictive Multicast Handover for PFMIPv6
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 [RFC5949]). For
multicast context transfer, the NMAG attaches to its HI message those
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group identifiers it requests to be forwarded from PMAG. Using the
identical syntax in its multicast mobility option headers as defined
in Section 5.4, 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 Figure 5.
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
| | | | |
Figure 5: Reactive Multicast Handover for PFMIPv6
4. Protocol Details
In this section the protocol operations are defined in a normative
way.
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4.1. Protocol Operations Specific to FMIPv6
4.1.1. Operations of the Mobile Node
A Mobile Node willing to manage multicast traffic by fast handover
operations MUST transfer its MLD listener state records within fast
handover negotiations.
When sensing a handover in predictive mode, an MN MUST build a
Multicast Mobility Option as described in Section 5.3 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
the Fast Binding Acknowledge (FBACK) (see Section 5.4) and learn
about unsupported or prohibited groups at the NAR. The MN MAY take
appropriate actions like home tunneling to receive groups/channels
not available from NAR. No multicast-specific operation is required
by the MN when re-attaching in the new network besides standard
FMIPv6 signaling.
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.
4.1.2. Operations of the Previous Access Router
A PAR MUST advertise its support for multicast by setting the M-bit
in PrRtAdv as specified in Section 5.1 of this document. This
indicator exclusively serves the purpose of informing MNs about the
capability of the PAR to process and exchange Multicast Mobility
Options during Fast Handover operations.
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 the NAR. In response to receiving multicast
subscriptions, the PAR SHOULD forward group data acting as a regular
multicast router or proxy. However, the PAR MAY refuse to forward
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some or all of the multicast flows (e.g., due to administrative
configurations or load conditions).
In reactive mode, the 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 the
multicast downstream and forwards data according to MLD reports
obtained from NAR, if capable of forwarding.
In both modes, the PAR MUST interpret the first of the two events -
the departure of the MN or the reception of the Multicast
Acknowledgement Option(s) - as if the MN had sent a multicast LEAVE
message and react according to the signaling scheme deployed in the
access network (i.e., MLD querying, explicit tracking).
4.1.3. Operations of the New Access Router
A NAR MUST advertise its multicast support by setting the M-bit in
PrRtAdv as specified in Section 5.1 of this document. This indicator
exclusively serves the purpose of informing MNs about the capability
of the NAR to process and exchange Multicast Mobility Options during
Fast Handover operations.
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, the
NAR builds a Multicast Acknowledgement Option(s) (see Section 5.4)
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, the NAR joins the groups the MN has
subscribed for (which are then forwarded by PAR) via the tunnel link.
In reactive mode, the NAR will learn about the multicast listener
state of a new MN from the Multicast Mobility Option appended to a HI
message at a time, when the MN has already performed local
subscriptions of the multicast service. Thus the 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.
In both modes, the NAR MUST send a LEAVE message to the tunnel after
forwarding of a group (channel) becomes unneeded, e.g., after native
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multicast traffic arrives or group membership of the MN terminates.
Sending this immediately eliminates the need for PAR and NAR to
process traffic that is not forwarded.
4.1.4. Buffering Considerations
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 the 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 reduce the multicast
packet loss, but may increase resource consumption and delay in
packet transmission. Implementors should balance the different
requirements in the context of predominant application demands (e.g.,
real-time requirements).
4.2. Protocol Operations Specific to PFMIPv6
4.2.1. Operations of the Mobile Node
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 [RFC5949] and
required by its access link-layer technology. No multicast-specific
mobility actions nor implementations are required at the MN in a
PMIPv6 domain.
4.2.2. Operations of the Previous MAG
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 Section 5.3 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.
The PMAG then waits until it receives the Multicast Acknowledgement
Option(s) with a HACK message (see Section 5.4) and the creation of
the bidirectional tunnel with NMAG. After the HACK message is
received, the PMAG adds the tunnel to its downstream interfaces in
the multicast forwarding database. For those groups (channels)
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reported in the Multicast Acknowledgement Option(s), i.e., not
supported in the new access network, the 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 for which an MLD listener report
was received from NMAG. However, it MAY deny forwarding for some or
all groups included in the listener report.
After the departure of the MN and on the reception of LEAVE messages
for groups/channels, it is RECOMMENDED that the PMAG terminates
forwarding of the specific groups and updates 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.
A MAG receiving a HI message with the 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
Section 5.4) within a HACK message 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 the NMAG. At the reception of LEAVE
messages for groups (channels), the PMAG terminates forwarding of the
specific groups and update its multicast forwarding database.
According to its multicast forwarding state, it will need to issue a
group/channel LEAVE to its upstream link, if no more listeners are
present on its downstream links.
In both modes, the 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).
4.2.3. Operations of the New MAG
A MAG receiving a HI message with a Multicast Mobility Option for a
currently unattached node follows the predictive fast handover mode
as an NMAG. It will decide on those multicast groups/channels it
selects to be forwarded from the PMAG and builds a Multicast
Acknowledgement Option (see Section 5.4) that enumerates only
unwanted groups/channels. This Mobility Option is appended to the
regular fast handover HACK messages, or - in the case of a unicast
HACK message being submitted prior to multicast state acknowledgement
- sent in an additional HACK message to the PMAG. Immediately
thereafter, the NMAG SHOULD update its MLD membership state based on
the report received in the Multicast Mobility Option. Until the MN
re-attaches, the NMAG uses its Loopback interface for downstream and
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MUST NOT forward traffic to the potential link of the MN. The 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, the NMAG additionally joins those
groups/channels on the tunnel interface that it wants to receive
forwarded from the PMAG.
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 an NMAG. Following the re-
attachment, it SHOULD immediately issue an MLD General Query to learn
about multicast subscriptions of the newly arrived MN. Using
standard multicast operations, the 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 Section 5.3
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,
the NMAG additionally joins those groups/channels on the tunnel
interface that it wants to receive by forwarding from the PMAG. When
multicast flows arrive, the NMAG forwards data to the appropriate
downlink(s).
In both modes, the NMAG MUST send a LEAVE message to the tunnel after
forwarding of a group (channel) becomes unneeded, e.g., after native
multicast traffic arrives or group membership of the MN terminates.
Sending this immediately eliminates the need for PMAG and NMAG to
process traffic that is not forwarded.
4.2.4. IPv4 Support Considerations
An MN in a PMIPv6 domain MAY use an IPv4 address transparently for
communication as specified in [RFC5844]. 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 Section 5.6 for
compatibility considerations with previous IGMP versions). Context
transfer between MAGs can transparently proceed in the HI/HACK
message exchanges by encapsulating IGMP multicast state records
within Multicast Mobility Options (see Section 5.3 and Section 5.4
for details on message formats).
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The deployment of IPv4 multicast support SHOULD be homogeneous across
a PMIP domain. This avoids multicast service breaks during
handovers.
It is worth mentioning the scenarios of a dual-stack IPv4/IPv6 access
network, and the use of GRE tunneling as specified in[RFC5845].
Corresponding implications and operations are discussed in the PMIP
Multicast Base Deployment document, see[RFC6224].
5. Message Formats
5.1. Multicast Indicator for Proxy Router Advertisement (PrRtAdv)
This document updates the Proxy Router Advertisements (PrRtAdv)
message format defined in Section 6.1.2. of [RFC5568]. The update
assigns the first bit of the Reserved field, to carry the 'M' bit, as
defined in Figure 6. An FMIPv6 AR indicates support for multicast by
assigning the setting 'M' bit to a value of 1.
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 ...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 6: Multicast Indicator Bit for Proxy Router Advertisement
(PrRtAdv) Message
This document updates the reserved field to include the 'M' bit
specified as follows.
M = 1 indicates that the specifications of this document apply
M = 0 indicates that the behaviour during Fast Handover proceeds
according to [RFC5568].
The default value (0) of this bit indicates a non-multicast capable
service.
5.2. Extensions to Existing Mobility Header Messages
The fast handover protocols use an IPv6 header type called Mobility
Header as defined in [RFC6275]. Mobility headers can carry variable
Mobility Options.
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The 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
Multicast 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).
5.3. New Multicast Mobility Option
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 Figure 7.
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 +
~ ~
~ ~
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Mobility Header Multicast Option
RFC Editor note: IANA is requested to allocate the value XXX and
remove this note prior to publication.
Type: XXX
Length: 8-bit unsigned integer. The length in four octets of this
option, not including the Option Type, Option Length, Option-Code and
Reserved fields.
Option-Code:
1: IGMPv3 Payload Type
2: MLDv2 Payload Type
3: IGMPv3 Payload Type from IGMPv2 Compatibility Mode
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4: MLDv2 Payload Type from MLDv1 Compatibility Mode
Reserved: MUST be set to zero by the sender and MUST be ignored by
the receiver.
MLD (IGMP) Report Payload: this field is composed of the MLD (IGMP)
Report message after stripping its ICMP header. This Report Payload
always contains an integer number of multicast records.
Corresponding message formats are defined for MLDv2 in [RFC3810], and
for IGMPv3 in [RFC3376]. This field MUST always contain the first
header line (reserved field and No of Mcast Address Records).
Figure 8 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 [RFC3810], or Section 4.2 of [RFC3376] for the
definition of Multicast Address Records).
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] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: MLDv2 Report Payload
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5.4. New Multicast Acknowledgement Option
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 Figure 9.
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 +
~ ~
~ ~
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Mobility Header Multicast Acknowledgement Option
RFC Editor note: IANA is requested to allocate the value XXX and
remove this note prior to publication.
Type: XXX
Length: 8-bit unsigned integer. The length in four octets of this
option, not including the Option Type, Option Length, Option-Code and
Status fields.
Option-Code: 0
Status:
1: Report Payload type unsupported
2: Requested group service unsupported
3: Requested group service administratively prohibited
MLD (IGMP) Unsupported Report Payload: this field is syntactically
identical to the MLD (IGMP) Report Payload field described in
Section 5.3, but is only composed of those multicast address records
that are not supported or prohibited in the new access network. This
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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.
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.
5.5. Length Considerations: Number of Records and Addresses
Mobility Header Messages exchanged in HI/HACK and FBU/FBACK dialogs
impose length restrictions on multicast context records due to the 8
bit Length field. The maximal payload length available in FBU/FBACK
messages is 4 octets (Mobility Option header line) + 1024 octets (MLD
Report Payload). For example, not more than 51 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, the number
of source addresses (S,.) is limited to 62.
5.6. MLD (IGMP) Compatibility Requirements
Access routers (MAGs) MUST support MLDv2 (IGMPv3). To enable
multicast service for MLDv1 (IGMPv2) listeners, the routers MUST
follow the interoperability rules defined in [RFC3810] ([RFC3376])
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 (IGMPv3) 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 Section 5.3. 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.
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6. Security Considerations
Security vulnerabilities that exceed issues discussed in the base
protocols of this document ([RFC5568], [RFC5949], [RFC3810],
[RFC3376]) are identified as follows.
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.
7. IANA Considerations
This document defines two new mobility options which need allocation
from the Mobility Header Type registry at http://www.iana.org/
assignments/mobility-parameters.
XXX Multicast Mobility Option, described in Section 5.3
XXX Multicast Acknowledgement Option, described in Section 5.4
RFC Editor note: The RFC Editor is requested to replace "XXX" by the
IANA-assigned value prior to publication and may then remove this
note.
8. Acknowledgments
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 [fmcast-mip6] was presented by Suh, Kwon, Suh, and Park in
2004.
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. The MULTIMOB working group has provided continuous
feedback during the evolution of this work. Comments, discussions
and reviewing remarks have been contributed by (in alphabetical
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order) Carlos J. Bernardos, Luis M. Contreras, Hui Deng, Shuai Gao,
Dirk von Hugo, Min Hui, Georgios Karagian, Marco Liebsch, Behcet
Sarikaya, Stig Venaas and Juan Carlos Zuniga.
Funding has been provided by the German Federal Ministry of Education
and Research within the projects Mindstone, SKIMS and SAFEST, which
is gratefully acknowledged.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5568] Koodli, R., "Mobile IPv6 Fast Handovers", RFC 5568, July
2009.
[RFC5949] Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F.
Xia, "Fast Handovers for Proxy Mobile IPv6", RFC 5949,
September 2010.
[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5,
RFC 1112, August 1989.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, August 2006.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
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9.2. Informative References
[RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast
Mobility in Mobile IP Version 6 (MIPv6): Problem Statement
and Brief Survey", RFC 5757, February 2010.
[fmcast-mip6]
Suh, K., Kwon, D., Suh, Y., and Y. Park, "Fast Multicast
Protocol for Mobile IPv6 in the fast handovers
environments", draft-suh-mipshop-fmcast-mip6-00 (work in
progress), July 2004.
[FMIPv6-Analysis]
Schmidt, TC. and M. Waehlisch, "Predictive versus Reactive
- Analysis of Handover Performance and Its Implications on
IPv6 and Multicast Mobility", Telecommunication Systems
Vol 33, No. 1-3, pp. 131-154, November 2005.
[RFC6224] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in Proxy Mobile
IPv6 (PMIPv6) Domains", RFC 6224, April 2011.
[I-D.ietf-multimob-pmipv6-source]
Schmidt, T., Gao, S., Zhang, H., and M. Waehlisch, "Mobile
Multicast Sender Support in Proxy Mobile IPv6 (PMIPv6)
Domains", draft-ietf-multimob-pmipv6-source-09 (work in
progress), March 2014.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.
[RFC5845] Muhanna, A., Khalil, M., Gundavelli, S., and K. Leung,
"Generic Routing Encapsulation (GRE) Key Option for Proxy
Mobile IPv6", RFC 5845, June 2010.
Appendix A. Considerations for Mobile Multicast Sources
This document specifies protocol operations for a fast handover of
mobile listeners, only. In this appendix, we briefly discuss aspects
of supporting mobile multicast sources.
In a multicast-enabled Proxy Mobile IPv6 domain, multicast sender
support is likely to be enabled by any one of the mechanisms
described in [I-D.ietf-multimob-pmipv6-source]. In this case,
multicast data packets from an MN are transparently forwarded either
to its associated LMA or to a multicast-enabled access network. In
any case, a mobile source can continue to transmit multicast packets
after a handover from PMAG to NMAG without additional management
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operations. Packets (with a persistent source address) will continue
to flow via the LMA or the access network into the previously
established distribution system.
In contrast, an MN will change its Care-of Address while performing
FMIPv6 handovers. Even though MNs are enabled to send packets via
the reverse NAR-PAR tunnel using their previous Care-of Address for a
limited time, Multicast sender support in such a Mobile IPv6 regime
will most likely follow one of the basic mechanisms (1) bidirectional
tunneling, (2) remote subscription, or (3) agent-based as described
in Section 5.1 of [RFC5757]. A solution for multicast senders that
is homogeneously deployed throughout the mobile access network can
support seamless services during Fast Handovers, the details of which
are beyond the scope of this document.
Authors' Addresses
Thomas C. Schmidt (editor)
HAW Hamburg
Dept. Informatik
Berliner Tor 7
Hamburg D-20099
Germany
Email: schmidt@informatik.haw-hamburg.de
Matthias Waehlisch
link-lab & FU Berlin
Hoenower Str. 35
Berlin D-10318
Germany
Email: mw@link-lab.net
Rajeev Koodli
Intel
3600 Juliette Lane
Santa Clara, CA 95054
USA
Email: rajeev.koodli@intel.com
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Godred Fairhurst
University of Aberdeen
School of Engineering
Aberdeen AB24 3UE
UK
Email: gorry@erg.abdn.ac.uk
Dapeng Liu
China Mobile
Phone: +86-123-456-7890
Email: liudapeng@chinamobile.com
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