Network Working Group T C. Schmidt
Internet-Draft HAW Hamburg
Intended status: Standards Track M. Waehlisch
Expires: September 7, 2010 link-lab & FU Berlin
R. Koodli
Cisco Systems
G. Fairhurst
University of Aberdeen
March 06, 2010
Multicast Listener Extensions for MIPv6 and PMIPv6 Fast Handovers
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-01
Abstract
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 could strongly 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.
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), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
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This Internet-Draft will expire on September 7, 2010.
Copyright Notice
Copyright (c) 2010 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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Multicast Context Transfer between Access Routers . . . . 5
3.2. Protocol Operations Specific to FMIPv6 . . . . . . . . . . 7
3.3. Protocol Operations Specific to PFMIPv6 . . . . . . . . . 9
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Common Protocol Operations . . . . . . . . . . . . . . . . 12
4.2. Protocol Operations Specific to FMIPv6 . . . . . . . . . . 12
4.3. Protocol Operations Specific to PFMIPv6 . . . . . . . . . 12
4.3.1. IPv4 Support Considerations . . . . . . . . . . . . . 12
5. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Multicast Indicator for Proxy Router Advertisement
(PrRtAdv) . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. Extensions to Existing Mobility Header Messages . . . . . 12
5.3. New Multicast Mobility Option . . . . . . . . . . . . . . 13
5.4. New Multicast Acknowledgement Option . . . . . . . . . . . 14
5.5. Length Considerations: Number of Records and Addresses . . 16
5.6. MLD (IGMP) Compatibility Aspects . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
Mobile IPv6 [RFC3775] defines a network layer mobility protocol
involving mobile nodes participation, 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 application
scenarios. Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568], and Fast
Handovers for Proxy Mobile IPv6 (PFMIPv6) [I-D.ietf-mipshop-pfmipv6]
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)
[FMIPv6-Analysis].
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 [RFC5213], but are subject to current specification
[I-D.ietf-multimob-pmipv6-base-solution]. It is assumed throughout
this document that mechanisms and protocol operations are in place to
transport multicast traffic to ARs. Symbolically, 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 serve applications like IPTV with
voluminous 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
[RFC5757]. It is undesirable to rely on home tunneling for
optimizing multicast. Unencapsulated, native multicast forwarding
requires forwarding states, 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 continuously
perform remote subscriptions in the visited networks.
This document specifies extension 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
in use. ARs or MAGs are then enabled to treat multicast traffic in
correspondence to fast unicast handovers and with analogous
performance. No protocol changes are introduced that prevent a
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multicast unaware node from performing fast handovers with multicast
aware ARs or MAGs.
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 pose any requirements on
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.
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],
[I-D.ietf-mipshop-pfmipv6], [RFC3775], and [RFC5213]. In addition,
the following terms are introduced:
3. Protocol Overview
The reference scenario for multicast fast handover is illustrated in
Figure 1.
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*** *** *** ***
* ** ** ** *
* *
* 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 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 such that
traffic follows the MN. This process may be significantly slower
than fast handover management [RFC5757]. Multicast listeners at
handover may take 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
thereof. Second, multicast streams may be included in traffic
forwarding via the tunnel established from PAR to NAR.
There are two modes of operation in FMIPv6 and in PFMIPv6. The
predictive mode allows for AR-binding and context transfer prior to
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MN's handover, while in the reactive mode, these steps are executed
after the MN's re-attachment to NAR has been detected. 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 (e.g., PAR 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, 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 Section 5.3. On reception of the HI message,
NAR returns a multicast acknowledgement in its HACK answer that per
group indicates its ability to support the requested group, as well
as its willingness to receive multicast traffic forwarded from PAR
(see Section 5.4). 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 [RFC4605] with the upstream tunnel interface to PAR, will
submit an MLD report to request for the desired groups, but will
terminate multicast forwarding [RFC3810] 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 multicast forwarding after the MN has arrived.
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. Depending on the
specific network topology, multicast traffic for some groups may
natively arrive before it is forwarded from PAR. However, PAR-NAR
forwarding SHOULD be procured for groups in far reach.
In both modes of operation, it is the responsibility of the PAR
(PMAG) to properly consider the departure of the MN for the local
group management. Depending on the multicast state management, link
type and MLD parameters deployed (cf., [RFC5757]), it SHOULD take
appropriate actions to adjust multicast service to requirements of
the remaining nodes.
In this way, the MN will be able to participate in multicast group
communication with handover experiences comparable to unicast
performance, while network resources are preserved whenever possible.
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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 handovers.
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, FBU is issued on the previous link and received
by PAR as displayed in Figure 2. 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.
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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
| |
Figure 2: Predictive Multicast Handover for FMIPv6
The call flow for reactive mode is visualized in Figure 3. 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, 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 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.
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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)|
| | |
| forward |
| packets(including FBack)=====>|
| | |
|<=================================== 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 operations are pursued 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
states at the mobile node. There are two ways to obtain record of
MN's multicast membership. First, MAGs may perform an explicit
tracking (cf., [RFC4605], [I-D.ietf-multimob-pmipv6-base-solution])
or extract membership status from forwarding states at node-specific
point-to-point links. Second, routers may perform general queries at
handovers. Both methods are equally applicable, which leaves a final
choice to the implementation. In either case, the PAR will become
knowledgeable about multicast group subscriptions of the MN.
In predictive mode, the PMAG (PAR) will learn about the upcoming
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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 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.
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
| | | | |
Figure 4: Predictive Multicast Handover for PFMIPv6
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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
states at the MN. Triggered by MN's attachment, the NMAG will
inquire on group memberships by submitting 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 [I-D.ietf-mipshop-pfmipv6]). For multicast
context transfer, the NMAG attaches those group identifiers in
multicast mobility options which it requests for forwarding. Using
the identical syntax in its option headers as defined in Section 5.4,
PMAG acknowledges the group forwarding request in its HACK answer.
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)
| | | |<- - - - - ->|
| | | | |
| | | forward |
| | | packets =======>|
| | | | |
|<======================================== deliver packets
| | | | |
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Figure 5: Reactive Multicast Handover for PFMIPv6
4. Protocol Details
4.1. Common Protocol Operations
:::TODO:
4.2. Protocol Operations Specific to FMIPv6
:::TODO:
4.3. Protocol Operations Specific to PFMIPv6
:::TODO:
4.3.1. IPv4 Support Considerations
:::TODO:
5. Message Formats
5.1. Multicast Indicator for Proxy Router Advertisement (PrRtAdv)
An FMIPv6 AR will indicate its multicast support by activating an
M-bit in its Proxy Router Advertisements (PrRtAdv). The message
extension is of the following form.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subtype |M| Reserved | Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 6: Multicast Indicator Bit for Proxy Router Advertisement
(PrRtAdv) Message
5.2. Extensions to Existing Mobility Header Messages
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
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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
The Multicast Mobility Option contains the current listener state
record of the MN as 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
Type: TBD
Length: 8-bit unsigned integer. The size of this option in 8 octets
including the Type, Option-Code, and Length fields.
Option-Code:
1: IGMPv3 Payload Type
2: MLDv2 Payload Type
3: IGMPv3 Payload Type from IGMPv2 Compatibility Mode
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 line. Corresponding
message formats are defined for MLDv2 in [RFC3810], and for IGMPv3 in
[RFC3376].
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Figure 8 shows the Report Payload for MLDv2, while the payload format
for IGMPv3 is defined correspondingly (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
5.4. New Multicast Acknowledgement Option
The Multicast Acknowledgement Option reports on the status of context
transfer and contains the list of state records that could not
successfully be transferred to the next access network. It has the
format displayed in Figure 9.
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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
Type: TBD
Length: 8-bit unsigned integer. The size of this option in 8 octets.
The length is 1 when MLD (IGMP) Unsupported Report Payload field
contains no Mcast Address Record.
Option-Code: 0
Status:
1: Report Payload type unsupported
2: Requested group service unsupported
3: Requested group service administratively prohibited
Reserved: MUST be set to zero by the sender and MUST be ignored by
the receiver.
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
field MUST always contain the first header line (reserved field and
No of Mcast Address Records), but MUST not contain any Mcast Address
Record, if 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)
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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. The maximal
payload length available in FBU/FBACK messages is 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 typical handover
scenarios, this number reduces further according to unicast context
and Binding Authorization data. Context information may be
fragmented in PFMIPv6 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.
5.6. MLD (IGMP) Compatibility Aspects
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 set the Multicast Address Compatibility Mode appropriately. When
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 Section 5.3. A NAR (nMAG) receiving a Multicast Mobility
Option during handover will switch to the minimum obtained of its
previous and newly learned value of MLD (IGMP) Compatibility Mode for
continued operation.
6. Security Considerations
Security vulnerabilities that exceed issues discussed in the base
protocols of this document ([RFC5568], [I-D.ietf-mipshop-pfmipv6],
[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 place
significant burdens of route establishment and traffic management
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onto the backbone infrastructure and the access router itself. Rapid
re-routing or traffic overloads can be mitigated by a rate control at
the AR that applies to the frequency of traffic redirects and to 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 new Mobility Options that need Type assignment
from the Mobility Options Type registry at
http://www.iana.org/assignments/mobility-parameters ....
8. Acknowledgments
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 [fmcast-mip6] was presented by Suh, Kwon, Suh, and Park already
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.
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.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[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.
[I-D.ietf-mipshop-pfmipv6]
Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F.
Xia, "Fast Handovers for Proxy Mobile IPv6",
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draft-ietf-mipshop-pfmipv6-12 (work in progress),
December 2009.
[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.
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.
[I-D.ietf-multimob-pmipv6-base-solution]
Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in PMIPv6
Domains", draft-ietf-multimob-pmipv6-base-solution-00
(work in progress), February 2010.
[PMIPv6v4]
Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-04
(work in progress), July 2008.
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Appendix A. Change Log
The following changes have been made from
draft-schmidt-multimob-fmipv6-pfmipv6-multicast-00.
1. Editorial improvements & clarifications.
2. Section on length considerations for multicast context records
added.
3. Section on MLD/IGMP compatibility aspects added.
4. Security section added.
Authors' Addresses
Thomas C. Schmidt
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
Cisco Systems
30 International Place
Xuanwu District,
Tewksbury MA 01876
USA
Email: rkoodli@cisco.com
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Godred Fairhurst
University of Aberdeen
School of Engineering
Aberdeen AB24 3UE
UK
Email: gorry@erg.abdn.ac.uk
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