MULTIMOB Group H. Asaeda
Internet-Draft Keio University
Intended status: Standards Track P. Seite
Expires: September 9, 2009 France Telecom
J. Xia
Huawei Technologies Co., Ltd.
March 8, 2009
PMIPv6 Extensions for Multicast
draft-asaeda-multimob-pmip6-extension-01
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Abstract
This document describes Proxy Mobile IPv6 (PMIPv6) extensions and
solutions to support IP multicast. The Mobile Access Gateway (MAG)
and the Local Mobility Anchor (LMA) are the mobility entities defined
in the PMIPv6 protocol and establish a bi-directional tunnel to
manage mobility for mobile nodes within the Proxy Mobile IPv6 domain.
This document defines the roles of LMA and MAG to support IP
multicast for the mobile nodes.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 6
2.1. Conventions Used in This Document . . . . . . . . . . . . 6
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Multicast Communication in PMIPv6 . . . . . . . . . . . . 7
3.2. Protocol Sequence for Joining and Leaving Multicast
Channels . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Local Mobility Anchor Operation . . . . . . . . . . . . . . . 11
4.1. LMA Operating As PIM-SM Router . . . . . . . . . . . . . . 11
4.2. LMA Operating As MLD Proxy . . . . . . . . . . . . . . . . 11
4.3. LMA Operating As AMT Relay . . . . . . . . . . . . . . . . 11
5. Mobile Access Gateway Operation . . . . . . . . . . . . . . . 12
5.1. MAG Operating As MLD Proxy . . . . . . . . . . . . . . . . 12
5.2. MAG Operating As PIM-SM Router . . . . . . . . . . . . . . 12
5.3. MAG Operating As AMT Gateway . . . . . . . . . . . . . . . 13
6. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 14
7. Dual-Mode Implementation . . . . . . . . . . . . . . . . . . . 15
8. Handover Process . . . . . . . . . . . . . . . . . . . . . . . 16
8.1. MAG Operating As MLD Proxy . . . . . . . . . . . . . . . . 16
8.2. MAG Operating As Multicast Router . . . . . . . . . . . . 19
8.3. Multicast Context Transfer Data Format . . . . . . . . . . 22
8.4. Proxy Binding Update with Multicast Extension . . . . . . 23
9. IPv4-Only and Dual-Stack Node Support . . . . . . . . . . . . 27
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
11. Security Considerations . . . . . . . . . . . . . . . . . . . 29
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
13.1. Normative References . . . . . . . . . . . . . . . . . . . 31
13.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
Proxy Mobile IPv6 (PMIPv6) [2] enables network-based mobility for
IPv6 mobile nodes (MNs) that do not implement any mobility protocols.
The Local Mobility Anchor (LMA) is the topological anchor point to
manages the mobile node's binding state. The Mobile Access Gateway
(MAG) is an access router or gateway that manages the mobility-
related signaling for a mobile node. MN is attached to the Proxy
Mobile IPv6 Domain (PMIPv6-Domain) that includes LMA and MAG(s), and
is able to receive data coming from outside of the PMIPv6-Domain
through LMA and MAG.
Network-based mobility support for unicast is addressed in [2], while
multicast support in PMIPv6 is not discussed in it. This document
describes PMIPv6 extensions and solutions to support IP multicast
communication for mobile nodes in PMIPv6-Domain. The problem
statements and the requirements for multicast communication in a
network-based mobility protocol have been documented in [12]. In
this document, multicast listener mobility is considered, while
multicast source mobility will be discussed in another draft.
Functions required on LMA and MAG for multicast communication are
described in this document. LMA and MAG set up the bi-directional
tunnel and set up the forwarding for the mobile node's traffic. LMA
must be capable of forwarding multicast packets through MAG toward
the corresponding mobile nodes. This condition requires LMA to
attach multicast networks by supporting multicast routing protocols
such as Protocol-Independent Multicast - Sparse Mode (PIM-SM) [3] or
other methods, and make traffic and QoS control if needed. On the
other hand, MAG must maintain multicast membership status for the
attached mobile nodes at the edge and forwards the multicast data
from LMA to the member nodes. This condition requires MAG to support
MLD [4]. Since each mobile node connects MAG with a point-to-point
access link, scalable operations and extensions for MAG must be
considered.
Seamless and fast handover must also be considered. When a host
receiving multicast data moves from an access link to another access
link, the host continuously receives the multicast data through newly
attached MAG. The handover procedure should guarantee multicast
session continuity and avoid extra packet loss and session
disruption. Context transfer will be the required function to
support seamless handover, while its effective procedure should be
taken into account interaction with multicast communication
protocols.
The PMIPv6 extension proposed in this document does not require to
change unicast communication methods or protocols defined in [2], and
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therefore both unicast and multicast communications for mobile nodes
in PMIPv6-Domain are enabled after all.
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2. Conventions and Terminology
2.1. Conventions Used in This Document
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 [1].
2.2. Terminology
The following terms used in this document are to be interpreted as
defined in the Proxy Mobile IPv6 specification [2]; Mobile Access
Gateway (MAG), Local Mobility Anchor (LMA), Mobile Node (MN), Proxy
Mobile IPv6 Domain (PMIPv6-Domain), LMA Address (LMAA), Proxy Care-of
Address (Proxy-CoA), Mobile Node's Home Network Prefix (MN-HNP),
Mobile Node Identifier (MN-Identifier), Proxy Binding Update (PBU),
and Proxy Binding Acknowledgement (PBA).
As defined in [8], "upstream interface" or "host interface" is an MLD
proxy device's interface in the direction of the root of the tree.
Each of an MLD proxy device's interfaces that is not in the direction
of the root of the tree is called "downstream interface" or "router
interface".
The Context Transfer Protocol (CXTP) specification [13] describes the
mechanism that allows better support for minimizes service disruption
during handover. In this document, CXTP is adopted for the multicast
context transfer protocol in PMIPv6, and "Multicast-Context Transfer
Data (M-CTD)" is defined as the new terminology for transferring MLD
state from previously attached MAG (p-MAG) to newly attached MAG
(n-MAG).
Mobile Node's Policy Profile includes "multicast channel
information", whose contents are the same one M-CTD contains, and the
mandatory fields of the policy profile specified in [2]. MN's Policy
Profile is provided by "policy store" whose definition is the same as
of [2], or by CXTP.
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3. Overview
3.1. Multicast Communication in PMIPv6
Required components to enable IP multicast are multicast routing
protocols and host-and-router communication protocols. This document
assumes PIM-SM [3] as the multicast routing protocol and MLDv2 [4] or
LW-MLDv2 [5] as the host-and-router communication protocol.
The architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.
LMA and MAG are the core functional entities in PMIPv6-Domain. The
entire PMIPv6-Domain appears as a single link from the perspective of
each mobile node.
+---------+
| Content |
| Source |
+---------+
|
*** *** *** *** ***
* ** ** ** ** *
* *
* Fixed Internet *
* *
* ** ** ** ** *
*** *** *** *** ***
/ \
+----+ +----+
|LMA1| |LMA2|
+----+ +----+
LMAA1 -> | | <-- LMAA2
| |
\\ //\\
\\ // \\
\\ // \\
\\ // \\
\\ // \\
\\ // \\
Proxy-CoA1--> | | <-- Proxy-CoA2
+----+ +----+
|MAG1|---{MN2} |MAG2|
+----+ | +----+
| | |
MN-HNP1 --> | MN-HNP2 | <-- MN-HNP3, MN-HNP4
{MN1} {MN3}
Figure 1: Proxy Mobile IPv6 Domain
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When a mobile node wants to subscribe/unsubscribe a multicast
channel, the node sends MLD Report messages with specifying
interesting/uninteresting sender and multicast addresses to the
access link. The attached MAG detects this membership information
and transfers the information to the corresponding LMA over a bi-
directional tunnel when needed, or transfers the information to the
adjacent multicast router.
When an LMA receives the membership information with MLD Report
messages or with PIM Join/Prune messages, it coordinates the
corresponding multicast routing tree if necessary. This operation
requires multicast routing protocols or proxy functions for LMA.
When a MAG detects mobile node's handover, it can proceed the
seamless handover procedures. Since both PMIPv6 and multicast
protocols (i.e., MLD and PIM-SM) do not have the functions for
handover in the original protocol specifications, external functions
or protocols such as CXTP [13] can be additionally used with PMIPv6
Proxy Binding Update (PBU).
3.2. Protocol Sequence for Joining and Leaving Multicast Channels
Upon multicast data reception, a mobile node sends MLD Report
messages including source and multicast addresses. Although MLDv2
specification [4] permits to use the unspecified address (::) for a
host whose interface has not acquired a valid link-local address yet,
MLDv2 Report messages MUST be sent with a valid IPv6 link-local
source address in PMIPv6 as defined in [10]. As well, MLDv2 Report
messages MAY be sent with an IP destination address of FF02:0:0:0:0:
0:0:16, to which all MLDv2-capable multicast routers listen, but the
IP unicast address of the attached MAG SHALL be used in many cases as
explained in [10].
An MLD proxy [8] can simplify the implementation of multicast data
forwarding. By not supporting complicated multicast routing
protocols, it reduces the implementation cost and the operational
overhead. Reducing the operational overhead will also contribute to
faster routing convergence. Another advantage is that an MLD proxy
can be independent of the multicast routing protocol used by the core
network routers.
When a MAG operates as an MLD proxy and receives MLD Report messages
from attached mobile nodes, it sends MLD messages on behalf of the
mobile nodes. MLD messages are always transferred over pre-
configured bi-directional tunnels as seen in Figure 2. MAG operating
as an MLD proxy always registers "downstream interface (or router
interface)" upon MLD message reception, but does not send MLD Report
when the received source and multicast addresses have been already
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reported to the same LMA through the same "upstream interface (or
host interface)".
MN1 MN2 MAG LMA
| | | |
|------MLD Report--------->| |
| (S1,G1) join | MLD Report |
| | |===bi-dir tunnel==>|
| | | |---> PIM (S1,G1) join
| | | |
| |--MLD Report-->| |
| | (S2,G2) join | MLD Report |
| | |===bi-dir tunnel==>|
| | | |---> PIM (S2,G2) join
| | | |
| |--MLD Report-->| |
| | (S1,G1) join | |
| | | |
Figure 2: MLD Report Messages Transmission
When a MAG operates as a PIM-SM router and receives MLD report
messages from attached mobile nodes, it joins the multicast delivery
tree by sending PIM join messages. At the same time, the MAG sends
MLD report messages with the Hold extension [10] with the
corresponding multicast channel information to the LMA (Figure 3).
When receiving the MLD Hold, the LMA joins the multicast delivery
tree but does not forward multicast data to the MAG; the idea is to
make the LMA ready to forward data while a new MAG completes the
handover routing update (detailed in Section 8).
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MN1 MN2 MAG LMA
| | | |
|------MLD Report--------->| |
| (S1,G1) join |---> PIM (S1,G1) join
| | | |
| | | MLD Hold |
| | |===bi-dir tunnel==>|
| | | |---> PIM (S1,G1) join
| | | | (No data forwarding)
| |--MLD Report-->| |
| | (S2,G2) join |---> PIM (S2,G2) join
| | | |
| | | MLD Hold |
| | |===bi-dir tunnel==>|
| | | |---> PIM (S2,G2) join
| | | | (No data forwarding)
| |--MLD Report-->| |
| | (S1,G1) join | |
| | | |
Figure 3: MLD Report Messages Transmission when MAG acts as a router
Whether a MAG works as an MLD proxy or a PIM-SM router, it MAY store
multicast channel information reported by attached mobile nodes in
the MN's policy profile (as defined in [2]). This information may be
used by the new MAG during the handover process (see Section 8).
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4. Local Mobility Anchor Operation
4.1. LMA Operating As PIM-SM Router
An LMA is responsible for maintaining the mobile node's reachability
state and is the topological anchor point for the mobile node's home
network prefix(es). When an LMA acts as a PIM-SM [3] multicast
router, it serves MAGs as listener nodes. Each MAG is connected
through a bi-directional tunnel, and each tunnel end-point address is
a Proxy-CoA.
An LMA sets up the multicast state and joins the group. Multicast
packets are tunneled to a MAG that requested to receive the
corresponding multicast session after being received by the LMA. The
MAG forwards these packets to the MN according to the multicast
listener state in the MAG.
[TODO: What is the required function for an LMA as a multicast
router? There is a case that a number of mobile nodes, let us say
more than 1,000 nodes, attach MAG and they are listening multicast
sessions. In addition, these mobile nodes connect to MAG with point-
to-point links with different prefixes. This condition will require
some protocol modification?]
4.2. LMA Operating As MLD Proxy
An LMA may act as an MLD proxy [8]. When LMA acts as an MLD proxy,
multicast data is forwarded from outside to mobile nodes through a
bi-directional tunnel to MAG.
When LMA acts as an MLD proxy, the attached MAGs must also act as an
MLD proxy.
4.3. LMA Operating As AMT Relay
It is possible for an LMA to support the AMT [9]. In this case, LMA
acts as an AMT Relay and the attached MAGs must act as AMT Gateways.
When LMA acts as an AMT Relay, it MUST also work as a PIM-SM router.
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5. Mobile Access Gateway Operation
The mobile access gateway (MAG) is the entity that performs the
mobility management on behalf of a mobile node. MAG is responsible
for detecting the mobile node's movements to and from the access
link.
5.1. MAG Operating As MLD Proxy
[2] supports only point-to-point access link types for MAG and MN
connection; hence an MN and a MAG are the only two nodes on an access
link, where the link is assumed to be multicast capable. Since a MAG
will deal with mobile nodes' membership states reported by a large
number of the downstream mobile nodes with MLD Report messages, the
protocol scalability must be taken into account.
A MAG acting as an MLD proxy sends MLD Query messages to all or some
of attached mobile nodes as described in [10]. After MAG receives
MLD Report messages from the mobile nodes, it forwards the MLD Report
messages on behalf of these mobile nodes to LMA. Mobile nodes send
MLD messages with their link-local address to MAG, and MAG forwards
the MLD messages through the bi-directional tunnel to LMA with the
MAG's link-local address.
An MLD proxy requires that the upstream and downstream interfaces
must be statistically configured. As well, MAG MUST configure an
upstream interface that is the interface MLD Report messages are sent
to LMA and downstream interfaces that are the interfaces MLD Report
messages are received from mobile nodes.
5.2. MAG Operating As PIM-SM Router
The optimal multicast routing path does not always include LMA,
especially in local routing described in [12]. The local routing
option is designed to support node-to-node communication within
PMIPv6-Domain where a local content source exists.
When LMA is not on a multicast delivery tree, MAG runs multicast
routing protocols to attach the optimal multicast routing path. This
document assume use of PIM-SM [3] as the supported multicast routing
protocol.
Because of its implementation or operational costs, operators may not
want to support PIM-SM on MAG. However, an MLD proxy requires to
statically configure its upstream interface, which is a bi-
directional tunnel as specified in Section 5.1, to receive all
multicast data, because there is no method to dynamically change the
upstream interface. Therefore, if operators need to take into
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account the case that an upstream interface for the optimized
multicast path is NOT a bi-directional tunnel to LMA but other
interface, and want MAG to "select" optimized routing path, MAG must
act as a PIM-SM router.
5.3. MAG Operating As AMT Gateway
It is possible for MN and MAG to perform with AMT [9]. In this case,
MAG acts as an AMT Gateway. MAG then summarizes all downstream
membership states. Since AMT data message that is a UDP packet
encapsulating IP multicast data is transmitted as a regular unicast
packet, the AMT data is not transmitted through a bi-directional
tunnel between MAG and LMA but forwarded toward the LMA by hop-by-hop
manner.
When MAG acts as an AMT Gateway, it SHOULD also work as an MLD proxy
as specified in [9].
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6. Mobile Node Operation
Mobile nodes attached to MAG can behave as the regular receiver
hosts. A mobile node sends MLD messages to MAG when it wants to
subscribe and unsubscribe IP multicast channels. And mobile nodes do
not change their behaviors whether MAG is acting as an MLD proxy or
an AMT Gateway. All MLD related considerations are described in
[10], which will give some advantage for its resource saving and
seamless handover for PMIPv6 multicast.
[2] allows a mobile node is a router. However, if MN is a multicast
router, it requires to make MAG act as a multicast router. To avoid
the complexity, in this document, MN may behave as an MLD proxy [8]
but should not work as a PIM-SM router, when MN needs to forward
multicast data to its downstream nodes.
[TODO: What is the other function for MN needed? Any specific
requirement?]
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7. Dual-Mode Implementation
Operators may want to make LMA or MAG act as both an MLD proxy and a
PIM-SM multicast router to support different customers. This
document proposes a "dual-mode" implementation that enables LMA or
MAG to support both an MLD proxy function and a multicast routing
function simultaneously.
To simplify mobile node's handover procedure among dual-mode MAGs,
p-MAG and n-MAG should not change the behaviors for the same mobile
node. For instance, in dual-mode, if p-MAG that a mobile node
attaches is working as an MLD proxy, n-MAG that the mobile node will
attach must also work as an MLD proxy. It is same as of PIM-SM.
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8. Handover Process
MAG is responsible for detecting the mobile node's movements to and
from the access link and for initiating binding registrations to the
mobile node's LMA. MAG tracks the mobile node's movements to and
from the access link and for signaling the mobile node's LMA. In
PMIPv6, it SHOULD NOT require for mobile nodes to initiate to re-
subscribe multicast channels, and MAG SHOULD keep multicast channel
subscription status for mobile nodes even if they attach a different
MAG in PMIPv6-Domain. In this section, mobility handover procedures
are described.
8.1. MAG Operating As MLD Proxy
When MAG operates as an MLD proxy, there are two possible ways to
proceed MLD listener handover; MLD listener handover with CXTP and
MLD listener handover with MN's Policy Profile. A Proxy Binding
Update with multicast extension (PBU-M) (defined in Section 8.4) is
always used to request the LMA to forward multicast data.
The MLD listener handover with CXTP shown in Figure 4 is defined as
follows;
1. Whenever MN attaches to n-MAG, the n-MAG requests multicast
context transfer to p-MAG.
2. p-MAG provides the multicast states corresponding to the moving
MN-Identifier to n-MAG. p-MAG utilizes a context transfer
protocol to deliver MN's profile to n-MAG, and sends Multicast
Context Transfer Data (M-CTD) (defined in Section 8.3) to n-MAG.
3. n-MAG records MN's profile including multicast channel
information.
4. n-MAG subscribes multicast channel on behalf of MN. PBU-M is
transmitted to LMA to establish a bi-directional tunnel for
forwarding corresponding multicast data.
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MN p-MAG n-MAG LMA
| | | |
|-MLD Report->| MLD Report |
| |===========bi-dir tunnel==========>|
| | | |---> PIM join
| | Multicast data |
|<------------|<==========bi-dir tunnel===========|
| | | |
Detach | | |
| | | |
Attach | | |
| | | |
|------------RS-------------->| |
| |<---CT-Req-----| |
| | | |
| |-----CXTP----->| |
| | M-CTD | MLD Report |
| | |-------PBU-M------>|
| | | |
| | |<-------PBA--------|
| | | |
|<-----------RA---------------| |
| | | |
| | | Multicast data |
|<----------------------------|<==bi-dir tunnel===|
| | | |
|<---------MLD Query----------| MLD Report |
|----------MLD Report-------->|===bi-dir tunnel==>|
| | | |
Figure 4: MLD listener handover with CXTP
After MN attaches to n-MAG, the multicast data will be delivered to
the MN immediately. MN's multicast membership state is maintained
with MLD Query and Report messages exchanged by MN and n-MAG.
Mobile node's multicast state is kept in MN's profile. If MN's
policy profile is stored in a policy store [2], it is not necessary
to use a context transfer protocol between p-MAG and n-MAG. In such
a case, n-MAG obtains MN's mulicast state by the same mechanism used
to acquire MN-ID and profile during MN's attachment process [2].
The procedure for MLD listener handover with MN's Policy Profile
(Figure 5) is shown as follows;
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1. n-MAG obtains the MN-Identifier and learns multicast channel
information described in Mobile Node's Policy Profile associated
to this MN-Identifier.
2. n-MAG prepares the PBU-M that includes multicast channel
information the MN has subscribed.
3. n-MAG transmits PBU-M to LMA to establish a bi-directional
tunnel for forwarding corresponding multicast data.
4. LMA forwards requested multicast data through a bi-directional
tunnel between the LMA and n-MAG.
MN p-MAG n-MAG LMA
| | | |
|-MLD Report->| MLD Report |
| |===========bi-dir tunnel==========>|
| | | |---> PIM join
| | Multicast data |
|<------------|<==========bi-dir tunnel===========|
| | | |
Detach | | |
| | | |
Attach | MN attachment event |
| | (Acquire MN-Id and Profile) |
| | | |
|------------RS-------------->| |
| | | MLD Report |
| | |-------PBU-M------>|
| | | |
| | |<-------PBA--------|
| | | |
|<-----------RA---------------| |
| | | |
| | | Multicast data |
|<----------------------------|<==bi-dir tunnel===|
| | | |
|<---------MLD Query----------| MLD Report |
|----------MLD Report-------->|===bi-dir tunnel==>|
| | | |
Figure 5: MLD listener handover with MN's Policy Profile
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8.2. MAG Operating As Multicast Router
MAG operating PIM-SM multicast routing protocol joins the multicast
delivery tree when an attached mobile node subscribes a multicast
channel. In order to reduce handover latency, LMA forwards multicast
data to n-MAG until n-MAG has joined the multicast delivery tree. A
Proxy Binding Update with multicast extension (PBU-M) is always used
to request the LMA to forward multicast data.
When MAG operates PIM-SM routing protocol, leveraging CXTP is the
possible handover scenario as in the following procedure;
1. Whenever MN attaches to n-MAG, the n-MAG requests multicast
context transfer to p-MAG.
2. p-MAG provides the multicast states corresponding to the moving
MN-Identifier to n-MAG. p-MAG utilizes a context transfer
protocol to deliver MN's profile to n-MAG, and sends M-CTD to
n-MAG.
3. n-MAG initiates the process to subscribe the multicast channels.
4. n-MAG requests LMA to forward multicast data in the meantime.
n-MAG prepares the PBU-M that includes multicast channel
information the MN has subscribed and has not yet received at
n-MAG.
5. LMA forwards requested multicast data through a bi-directional
tunnel between the LMA and n-MAG.
6. Whenever n-MAG joins the multicast delivery tree, it notifies
the LMA to stop forwarding the data and switches to the optimal
multicast routing path.
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MN p-MAG n-MAG LMA
| | | |
|--MLD Report->| MLD Hold |
| |==========bi-dir tunnel===========>|
| |---> PIM join | |---> PIM join
| | | |
|<--Multicast--| | |
| data | | |
Detach | | |
| | | |
Attach | | |
| | | |
|-------------RS-------------->| |
| | | |
| |<---CT-Req-----| |
| | | |
| |-----CXTP----->| |
| | M-CTD |---> PIM join |
| | | |
| | | MLD Report (join) |
| | |-------PBU-M------>|
| | | |
| | |<-------PBA--------|
| | | |
|<------------RA---------------| |
| | | |
| | | Multicast data |
| | |<==bi-dir tunnel===|
|<-------Multicast data--------| |
| | | |
| | Join process completed |
| | | |
| | | MLD Hold |
| | |-------PBU-M------>|
| | | |
|<-------Multicast data--------| |
| | | |
Figure 6: PIM-SM handover with CXTP
The following procedure is for PIM-SM handover using MN's Policy
Profile;
1. When n-MAG detects a moving mobile node, it obtains the MN-
Identifier and learns multicast channel information described in
Mobile Node's Policy Profile associated to this MN-Identifier.
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2. n-MAG prepares the PBU-M that includes multicast channel
information the MN has subscribed and has not yet received at
n-MAG.
3. n-MAG transmits PBU-M to LMA to establish a bi-directional
tunnel for forwarding corresponding multicast data.
4. LMA subscribes requested multicast channels and forwards the
data through a bi-directional tunnel between the LMA and n-MAG.
5. Whenever n-MAG joins the multicast delivery tree, it notifies
the LMA to stop forwarding the data and switches to the optimal
multicast routing path.
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MN p-MAG n-MAG LMA
| | | |
|--MLD Report->| | |
| | MLD Hold |
| |==========bi-dir tunnel===========>|
| |---> PIM join | |---> PIM join
| | | |
|<--Multicast--| | |
| data | | |
| | | |
Detach | | |
| | | |
Attach | MN attachment event |
| | (Acquire MN-Id and Profile) |
|-------------RS-------------->| |
| | |---> PIM join |
| | | |
| | | MLD Report (join) |
| | |-------PBU-M------>|
| | | |
| | |<-------PBA--------|
| | | |
|<------------RA---------------| |
| | | |
| | | Multicast data |
| | |<==bi-dir tunnel===|
|<-------Multicast data--------| |
| | | |
| | Join process completed |
| | | |
| | | MLD Hold |
| | |-------PBU-M------>|
| | | |
|<-------Multicast data--------| |
| | | |
Figure 7: PIM-SM handover with MN's Policy Profile
8.3. Multicast Context Transfer Data Format
The following information is necessary to keep mobile node's
membership status, and hence M-CTD includes the information;
1. Receiver address - indicates an address of a receiver host
sending the Current-State Report.
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2. Last membership report - indicates the time that the router
receives the last Current-State Report.
3. Filter mode - indicates either INCLUDE or EXCLUDE as defined in
[4].
4. Source addresses and multicast address - indicates the address
pair that the receiver has joined.
8.4. Proxy Binding Update with Multicast Extension
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R|P|C| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Proxy Binding Update Message with Multicast Extension
A Binding Update message that is sent by MAG to LMA is referred to as
the "Proxy Binding Update" message. A new flag (C) is included in
the Binding Update message with multicast extension. The rest of the
Binding Update message format remains the same as defined in [11] and
with the additional (R), (M), and (P) flags, as specified in [14],
[15], and [2], respectively.
Multicast Channel Subscription Flag
A new flag (C) is included in the Binding Update message to
indicate to LMA that the Binding Update message is a multicast
channel subscription.
When (C) flag is specified in PBU-M message, the mobility options
field includes the same information of MLDv2 Report message [4]:
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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 = 143 | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |Nr of Mcast Address Records (M)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Multicast Address Record [1] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Multicast Address Record [2] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
. . .
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Multicast Address Record [M] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9
Each Multicast Address Record has the following internal format:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record Type | Aux Data Len | Number of Sources (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
* *
| |
* Multicast Address *
| |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
* *
| |
* Source Address [1] *
| |
* *
| |
+- -+
| |
* *
| |
* Source Address [2] *
| |
* *
| |
+- -+
. . .
. . .
. . .
+- -+
| |
* *
| |
* Source Address [N] *
| |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Auxiliary Data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10
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All the above fields contain data with the same definitions in [4].
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9. IPv4-Only and Dual-Stack Node Support
The mobile node may be an IPv4-only node, IPv6-only node, or a dual-
stack (IPv4/v6) node. Although this document mainly describes IPv6
address/prefix mobility with the transport network being IPv6, it
proposes the tunneling method by which IPv4-only mobile node or a
dual-stack mobile node that wants to subscribe IPv4 multicast
channels. As with the discussion in the MBONE working group, AMT [9]
is the possible candidate to fulfill the requirement. AMT provides
the multicast connectivity to the unicast-only inter-network. To do
this, multicast packets being sent to or from a site are encapsulated
in unicast packets.
When MAG behaves as an AMT Gateway, it sends an MLD report message
via its AMT Pseudo-Interface that encapsulates the message to a
particular AMT Relay (i.e., LMA).
While MLD messages or multicast packets are always encapsulated with
both IPv4 and IPv6 headers, AMT messages, which are the regular IPv6
unicast packets, are not transmitted over a bi-directional tunnel.
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10. IANA Considerations
This document creates a new registry for the flags in the Binding
Update message called the "Binding Update Flags".
The following flags are reserved:
(A) 0x8000 [RFC3775]
(H) 0x4000 [RFC3775]
(L) 0x2000 [RFC3775]
(K) 0x1000 [RFC3775]
(M) 0x0800 [RFC4140]
(R) 0x0400 [RFC3963]
(P) 0x0200 [RFC5213]
This document reserves a new flag (C) for "Proxy Binding Update with
Multicast Extension" as described in Section 8.4 as follows:
(C) 0x0100
The rest of the values in the 16-bit field are reserved. New values
can be assigned by Standards Action or IESG approval.
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11. Security Considerations
TBD.
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12. Acknowledgements
Many of the specifications described in this document are discussed
and provided by the PMIPv6 multicast support design team members.
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13. References
13.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
[2] Gundavelli, S, Ed., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[3] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[4] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004.
[5] Liu, H., Cao, W., and H. Asaeda, "Lightweight IGMPv3 and MLDv2
Protocols",
draft-ietf-mboned-lightweight-igmpv3-mldv2-04.txt (work in
progress), September 2008.
[6] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999.
[7] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP",
RFC 4607, August 2006.
[8] 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.
[9] Thaler, D., Talwar, M., Aggarwal, A., Vicisano, L., and T.
Pusateri, "Automatic IP Multicast Without Explicit Tunnels
(AMT)", draft-ietf-mboned-auto-multicast-08.txt (work in
progress), October 2007.
[10] Asaeda, H. and T. Schmidt, "IGMP and MLD Extensions for Mobile
Hosts and Routers",
draft-asaeda-multimob-igmp-mld-mobility-extensions-02.txt (work
in progress), March 2009.
[11] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[12] Deng, H., Schmidt, T., Seite, P., and P. Yang, "Multicast
Support Requirements for Proxy Mobile IPv6",
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draft-deng-multimob-pmip6-requirement-01.txt (work in
progress), October 2008.
[13] Loughney, Ed., J., Nakhjiri, M., Perkins, C., and R. Koodli,
"Context Transfer Protocol (CXTP)", RFC 4067, July 2005.
13.2. Informative References
[14] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
[15] Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,
"Hierarchical Mobile IPv6 Mobility Management (HMIPv6)",
RFC 4140, August 2005.
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Authors' Addresses
Hitoshi Asaeda
Keio University
Graduate School of Media and Governance
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Email: asaeda@wide.ad.jp
URI: http://www.sfc.wide.ad.jp/~asaeda/
Pierrick Seite
France Telecom
4, rue du Clos Courtel
BP 91226, Cesson-Sevigne 35512
France
Email: pierrick.seite@orange-ftgroup.com
Jinwei Xia
Huawei Technologies Co., Ltd.
Huihong Mansion, No.91 Baixia Rd.
Nanjing, Jiangsu 21001
China
Email: xiajinwei@huawei.com
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