Internet Engineering Task Force (IETF) JC. Zuniga

Internet Engineering Task Force (IETF) JC. Zuniga
Request for Comments: 7028 InterDigital Communications, LLC
Category: Experimental LM. Contreras
ISSN: 2070-1721 Telefonica I+D
CJ. Bernardos
UC3M
S. Jeon
Instituto de Telecomunicacoes
Y. Kim
Soongsil University
September 2013

Multicast Mobility Routing Optimizations for Proxy Mobile IPv6

Abstract

This document proposes some experimental enhancements to the base
solution to support IP multicasting in a Proxy Mobile IPv6 (PMIPv6)
domain. These enhancements include the use of a multicast tree
mobility anchor as the topological anchor point for multicast
traffic, as well as a direct routing option where the Mobile Access
Gateway can provide access to multicast content in the local network.
The goal of these enhancements is to provide benefits such as
reducing multicast traffic replication and supporting different
PMIPv6 deployment scenarios.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.

This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7028.

Zuniga, et al. Experimental [Page 1]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

Copyright Notice

Copyright (c) 2013 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
2. Terminology .....................................................4
3. Overview ........................................................5
3.1. MTMA/Direct Routing Mode Selection .........................5
3.2. Multicast Tree Mobility Anchor (Subscription via MTMA) .....5
3.3. Direct Routing (Subscription via Direct Routing) ...........7
4. Mobile Access Gateway Operation .................................9
4.1. Extensions to Binding Update List Data Structure ...........9
4.2. MAG as MLD Proxy ...........................................9
4.2.1. MTMA Mode (Subscription via MTMA) ...................9
4.2.2. Direct Routing Mode (Subscription via
Direct Routing) ....................................11
5. Local Mobility Anchor Operation ................................14
5.1. Dynamic IP Multicast Selector Option ......................14
5.1.1. Option Application Rules ...........................14
5.1.2. Option Format ......................................14
6. Multicast Tree Mobility Anchor Operation .......................16
6.1. Conceptual Data Structures ................................17
7. Mobile Node Operation ..........................................17
8. IPv4 Support ...................................................17
9. IANA Considerations ............................................18
10. Security Considerations .......................................18
11. Contributors ..................................................19
12. References ....................................................20
12.1. Normative References .....................................20
12.2. Informative References ...................................21
Appendix A. MTMA Deployment Use Cases .............................22
A.1. PMIPv6 Domain with Ratio 1:1 ...............................22
A.2. PMIPv6 Domain with Ratio N:1 ...............................22
A.3. PMIPv6 Domain with Ratio 1:N ...............................24
A.4. PMIPv6 Domain with H-LMA ...................................26

Zuniga, et al. Experimental [Page 2]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

1. Introduction

Proxy Mobile IPv6 [RFC5213] is a network-based approach to solving
the IP mobility problem. In a Proxy Mobile IPv6 (PMIPv6) domain, the
Mobile Access Gateway (MAG) behaves as a proxy mobility agent in the
network and performs the mobility management on behalf of the Mobile
Node (MN). The Local Mobility Anchor (LMA) is the home agent for the
MN and the topological anchor point. PMIPv6 was originally designed
for unicast traffic. However, a PMIPv6 domain may handle data from
both unicast and multicast sources.

The Internet Group Management Protocol (IGMPv3) [RFC3376] is used by
IPv4 hosts to report their IP multicast group memberships to
neighboring multicast routers. Multicast Listener Discovery Version
2 (MLDv2) [RFC3810] is used in a similar way by IPv6 routers to
discover the presence of IPv6 multicast hosts. Also, the IGMP/MLD
proxy specification [RFC4605] allows an intermediate (i.e., edge)
node to appear as a multicast router to downstream hosts and as a
host to upstream multicast routers. IGMP- and MLD-related protocols
however were not originally designed to address the IP mobility of
multicast listeners (i.e., IGMP and MLD protocols were originally
designed for fixed networks).

A base solution to support both IPv4 and IPv6 multicast listener
mobility in a PMIPv6 domain is specified in [RFC6224], which
describes deployment options without modifying mobility and multicast
protocol standards. PMIPv6 allows a mobile access gateway to
establish multiple PMIPv6 tunnels with different local mobility
anchors, e.g., up to one per mobile node. In the presence of
multicast traffic, multiple instances of the same traffic can
converge to the same MAG. Hence, when IP multicasting is applied
into PMIPv6, it may lead to redundant traffic at a MAG. This is the
tunnel convergence problem.

In order to address this issue, this document proposes an
experimental solution, consisting of two complementary enhancements:
multicast anchor and direct routing. The first enhancement makes use
of a Multicast Tree Mobility Anchor (MTMA) as the topological anchor
point for remotely delivering multicast traffic, while the second
enhancement uses direct routing taking advantage of local multicast
source availability, allowing a mobile access gateway to connect
directly to a multicast router for simple access to local content.
Neither of the two schemes has any impact on the mobile node to
support IPv4 and IPv6 multicast listener mobility, nor on the wider
Internet, as they only affect the PMIPv6 domains where they are
deployed. Although references to "MLD proxy" are used in the
document, it should be understood to also include "IGMP/MLD proxy"
functionality (see Section 8 for details). The status of this

Zuniga, et al. Experimental [Page 3]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

proposal is Experimental. The status of this proposal may be
reconsidered in the future, once more implementation feedback and
deployment experience is gathered, reporting on the performance of
the two proposed schemes as well as operational feedback on scheme
selection.

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 [RFC2119].

This document uses the terminology defined in [RFC5213], [RFC6275],
and [RFC3810]. Specifically, the definition of PMIPv6 domain is
reused from [RFC5213] and reproduced here for completeness.

Proxy Mobile IPv6 Domain (PMIPv6-Domain): Proxy Mobile IPv6 domain
refers to the network where the mobility management of a mobile
node is handled using the Proxy Mobile IPv6 protocol as defined in
[RFC5213]. The Proxy Mobile IPv6 domain includes local mobility
anchors and mobile access gateways between which security
associations can be set up and authorization for sending proxy
binding updates on behalf of the mobile nodes can be ensured.

In this document we refine the definition from the point of view of
the kind of traffic served to the MN in the following way:

PMIPv6 unicast domain: PMIPv6 unicast domain refers to the network
covered by one LMA for unicast service. This service supports
mobility as the MN moves from one MAG to another one, both
associated with the same LMA regarding the MN unicast traffic.

PMIPv6 multicast domain: PMIPv6 multicast domain refers to the
network covered by one network element named MTMA (defined below)
for multicast service in such a way that an MN using that service
is not aware of mobility as it moves from one MAG to another.

From the definitions above, it can be stated that a PMIPv6 domain can
have several PMIPv6 unicast domains and PMIPv6 multicast domains.
Additionally, some other definitions are introduced, as follows.

MTMA or multicast tree mobility anchor: An entity working as
topological anchor point for multicast traffic. It manages the
multicast groups subscribed by all (or a subset of) the MAGs in a
PMIPv6 multicast domain, on behalf of the MNs attached to them.
Hence, an MTMA performs the functions of either a designated
multicast router or an MLD proxy.

Zuniga, et al. Experimental [Page 4]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

H-LMA or Hybrid-LMA: An entity that is dedicated to both unicast and
multicast services and able to work as both LMA and MTMA
simultaneously.

Direct routing: This scheme uses the native multicast infrastructure
for retrieving multicast data. For an operator having its own
local content, this technique also includes the case where the
content source is directly connected to the MAG.

Subscription via MTMA: Multicast subscription mode in which the
content is retrieved from the remote (or home) MTMA.

Subscription via direct routing: Multicast subscription mode in
which the content is retrieved using direct routing from the local
domain.

3. Overview

3.1. MTMA/Direct Routing Mode Selection

This specification describes two complementary operational modes that
can be used to deliver multicast traffic in a PMIPv6 domain:
multicast tree mobility anchor and direct routing. There are
different approaches that can be followed to perform this operational
mode selection, depending on the operator's preferences and PMIPv6
deployment characteristics. For example, the mode can be manually
configured at the mobile access gateway, according to the multicast
tree deployment in the PMIPv6 domain, following operator's
configuration of the multicast distribution on it. Another option is
the use of dynamic policies, conveyed in the PBU (Proxy Binding
Update) / PBA (Proxy Binding Acknowledgement) signaling using the
Dynamic IP Multicast Selector option described in Section 5.1. Next,
each of the two operational modes is introduced.

3.2. Multicast Tree Mobility Anchor (Subscription via MTMA)

A multicast tree mobility anchor is used to serve as the mobility
anchor for multicast traffic. The MTMA is either a designated
multicast router or an MLD proxy. Typically, the MTMA will be used
to get access to remote multicast content.

The multicast tree mobility anchor connects to the mobile access
gateway, as described in [RFC6224], and it can reuse native PMIPv6
features such as tunnel establishment and security [RFC5213],
heartbeat [RFC5847], etc. Unicast traffic will go normally to the
local mobility anchors in the PMIPv6 domain as described in
[RFC5213]. A MAG connecting to the MTMA acts as an MLD proxy.

Zuniga, et al. Experimental [Page 5]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

This section describes how the MTMA works in scenarios of MN
attachment and multicast mobility. It concentrates on the case of
both LMA and MTMA defining a unique PMIPv6 domain. Some other
deployment scenarios are presented in Appendix A.

Figure 1 shows an example of a PMIPv6 domain supporting multicast
mobility. The local mobility anchor is dedicated to unicast traffic,
and the multicast tree mobility anchor is dedicated to multicast
traffic. The MTMA can be considered to be a form of upstream
multicast router with tunnel interfaces allowing subscription via
MTMA for the MNs.

As shown in Figure 1, MAG1 may connect to both unicast (LMA) and
multicast (MTMA) entities. Thus, a given MN may simultaneously
receive both unicast and multicast traffic. In Figure 1, MN1 and MN2
receive unicast traffic, multicast traffic, or both, whereas MN3
receives multicast traffic only.

Zuniga, et al. Experimental [Page 6]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

+--------------+
|Content Source| || - PMIPv6 Tunnel
+--------------+ | - Multicast
| Data Path
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* Unicast Traffic * * Multicast Traffic *
* * * *
* ** ** ** * * ** ** ** *
*** *** *** ** *** *** *** ***
| |
| |
| |
+-----+ +------+
Unicast | LMA | | MTMA | Multicast
Anchor +-----+ +------+ Anchor
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
+------+ +------+
| MAG1 | | MAG2 | MLD Proxy
+------+ +------+
| | |
| | |
{MN1} {MN2} {MN3}

Figure 1: Architecture of Multicast Tree Mobility Anchor (MTMA)

3.3. Direct Routing (Subscription via Direct Routing)

Direct routing uses a native multicast infrastructure, allowing a
mobile access gateway to directly connect to a multicast router (as
next hop) in the PMIPv6 domain. A MAG acts as an MLD proxy.

The main purpose of direct routing is to provide optimal connectivity
for local content. As a consequence, it replaces the MTMA of the
channel management and data delivery of locally available content.
Unicast traffic will go as normally to the LMAs in the PMIPv6 domain.

Zuniga, et al. Experimental [Page 7]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

This section describes how the direct routing works in scenarios of
MN attachment and multicast mobility.

Multicast Tree
:
: || - PMIPv6 Tunnel
+----------+ +----------+ | - Multicast Data Path
| LMA | | MR |
+----------+ +----------+
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ |
|| /\\ |
|| / \\ |
|| / \\ |
|| / \\ |
|| / \\ |
+--------+ +--------+
| MAG1 | | MAG2 | MLD proxy
+--------+ +--------+
: :
+------+ +------+
| MN1 | -----> | MN1 |
+------+ +------+

Figure 2: Architecture for Direct-Routing-Based PMIPv6 Multicasting

Figure 2 shows the architecture for the local routing case using
native multicasting infrastructure [PMIP6-REQ].

The local mobility anchor is dedicated to unicast traffic, and the
multicast traffic is obtained from an upstream multicast router
present in the PMIPv6 domain. Note that there can be multiple LMAs
for unicast traffic (not shown in Figure 1 for simplicity) in a given
PMIPv6 domain.

As shown in Figure 2, a mobile access gateway may connect to both
unicast (LMA) and multicast routers (MRs). Thus, a given mobile node
may simultaneously receive both unicast and multicast traffic.

As seen in Figure 2, each MAG has a direct connection (i.e., not
using the PMIPv6 tunnel interface) with a multicast router.
Depending on the multicast support on the visited network, different
schemas can be used to provide this direct connection between the

Zuniga, et al. Experimental [Page 8]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

MAGs and the multicast router(s), e.g., being connected to the same
shared link or using a tunneling approach, such as Generic Routing
Encapsulation (GRE) tunnels [RFC2784] or Automatic Multicast
Tunneling (AMT) [AUTO]. To facilitate IGMP/MLD signaling and
multicast traffic forwarding, an MLD proxy function defined in
[RFC4605] SHOULD be implemented in the MAG. There SHOULD be direct
connectivity between the MAG and the local multicast router (or
additional MLD proxy).

4. Mobile Access Gateway Operation

This section describes the operation of the mobile access gateway,
considering that the MAG incorporates MLD proxy functions as per
[RFC4605].

4.1. Extensions to Binding Update List Data Structure

A Binding Update List (BUL) at the MAG, like the one specified in
[RFC5213], MUST be maintained to handle the relationship between the
serving entities (e.g., MTMA and LMA) and the mobile nodes for both
unicast and multicast traffic.

4.2. MAG as MLD Proxy

4.2.1. MTMA Mode (Subscription via MTMA)

In case of subscription via MTMA, all MAGs that are connected to the
MTMA must support the MLD proxy function [RFC4605]. Specifically in
Figure 1, each of the MAG1-MTMA and MAG2-MTMA tunnel interfaces
define an MLD proxy domain. The mobile nodes are considered to be on
the downstream interface of the MLD proxy (of the MAG), and the MTMA
is considered to be on the upstream interface (of the MAG) as per
[RFC4605]. Note that the mobile access gateway could also be an IGMP
proxy.

Figure 3 shows the procedure when MN1 attaches to a MAG, and
establishes associations with the LMA (unicast) and the MTMA
(multicast).

Zuniga, et al. Experimental [Page 9]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

MN1 MAG1 LMA MTMA
| (MLD proxy) (Unicast) (Multicast)
MN1 attaches to MAG1 | | |
| | | |
|----Rtr Sol--------->| | |
| |--PBU---->| |
| | | |
| |<----PBA--| |
| | | |
| |=Unicast==| |
| | Tunnel | |
|<---------Rtr Adv----| | |
| | | |
|< ------ Unicast Traffic------->| |
| | | |
| |==Multicast Tunnel===|
| | | |
|<-------MLD Query----| | |
| | | |
MN1 requires | | |
multicast services | | |
| | | |
|----MLD Report (G)-->| | |
| | | |
| |----Aggregated------>|
| | MLD Report (G) |
| | | |
| | | |
|<-----------Multicast Traffic------------->|
| | | |

Figure 3: MN Attachment and Multicast Service Establishment for MTMA

In Figure 3, the MAG first establishes the PMIPv6 tunnel with LMA for
unicast traffic as defined in [RFC5213] after being triggered by the
Router Solicitation message from MN1. Unicast traffic will then flow
between MN1 and LMA.

For multicast traffic, a multicast tunnel may have been pre-
configured between MAG and MTMA, or may be dynamically established
when the first MN appears at the MAG.

MN1 sends the MLD report message (when required by its upper-layer
applications) as defined in [RFC3810] in response to an MLD Query
from MAG (generated as defined by [RFC6224] upon handover). The MAG,
acting as an MLD proxy defined in [RFC4605], will then send an
Aggregated MLD Report to the multicast anchor, MTMA (assuming that
this is a new multicast group that the MAG had not previously

Zuniga, et al. Experimental [Page 10]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

subscribed to). Multicast traffic will then flow from the MTMA
towards MN1. The MTMA acts as an MLD Querier, so it will
periodically query each mobile access gateway about the subscriptions
it maintains (not shown in Figure 3).

We next consider a mobility scenario in which MN1 with an ongoing
multicast subscription moves from one MAG to another MAG. According
to the baseline solution signaling method described in [RFC6224],
after MN1 mobility, the new mobile access gateway acting in its role
of MLD proxy will send an MLD Query to the newly observed mobile node
on its downlink. Assuming that the subsequent MLD Report from MN1
requests membership for a new multicast group (from the new MAG's
point of view), this will then result in an Aggregated MLD Report
being sent to the MTMA from the new mobile access gateway. This
message will be sent through a multicast tunnel between the new MAG
and MTMA (pre-established or dynamically established).

When MN1 detaches, the old MAG may keep the multicast tunnel with the
multicast MTMA if there are still other MNs using the multicast
tunnel. Even if there are no mobile nodes currently on the multicast
tunnel, the old MAG may decide to keep the multicast tunnel
temporarily for potential future use.

As discussed above, existing MLD (and MLD proxy) signaling will
handle a large part of the multicast mobility management for the
mobile node.

4.2.2. Direct Routing Mode (Subscription via Direct Routing)

In this case, the MLD proxy instance is configured to obtain the
multicast traffic locally. Figure 4 shows an example of multicast
service establishment. The mobile access gateway first establishes
the PMIPv6 tunnel with the local mobility anchor for unicast traffic
as defined in [RFC5213] after being triggered by the Router
Solicitation message from the mobile node. Unicast traffic will then
flow between the MN and LMA.

For multicast traffic, it is assumed that the upstream interface of
the MLD proxy instance has been configured pointing to a multicast
router internal to the PMIPv6 domain (or towards an additional MLD
proxy node in the domain), for all the multicast channels (which, in
consequence, have to be local). There should be direct connectivity
between the MAG and the local multicast router (or additional MLD
proxy).

Zuniga, et al. Experimental [Page 11]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

MN1 MAG1 LMA MR
| (MLD proxy) (Unicast) (Multicast)
MN1 attaches to MAG1 | | |
| | | |
|----Rtr Sol--------->| | |
| |--PBU------->| |
| | | |
| |<-------PBA--| |
| | | |
| |===Unicast===| |
| | Tunnel | |
|<---------Rtr Adv----| | |
| | | |
|<--------Unicast Traffic---------->| |
| | | |
| | | |
|<-------MLD Query----|<-------------MLD Query----|
| | | |
MN1 requires | | |
multicast services | | |
| | | |
|--MLD Report (G)---->| | |
| | | |
| |----Aggregated------------>|
| | MLD Report (G) |
| | | |
| | | |
|<-------------Multicast Traffic----------------->|
| | | |

Figure 4: Multicast Service Establishment for Direct Routing

Upon detecting node attachment from an incoming interface, the MAG
adds each downstream interface to the MLD proxy instance with an
upstream link to an MR according to the standard MLD proxy operations
[RFC4605] and sends an MLD Query message towards the MN. The mobile
node sends the MLD report message (when required by its upper-layer
applications) in response to an MLD Query from the MAG. Upon
receiving the MLD Report message from each incoming interface, the
MAG checks the MLD proxy instance associated with the downstream
interface and then the MLD Report messages will be aggregated and
forwarded to the upstream link associated with the MR (assuming that
this is a new multicast group that the MAG had not previously
subscribed to). Multicast traffic will then flow from the local
multicast router towards the mobile node.

Zuniga, et al. Experimental [Page 12]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

MN1 P-MAG N-MAG LMA MR
| | | | |
| | | | |
|<------------|<-- Multicast Data----------------|
| | . | | |
| | . | | |
| | . | | |
Link Handover | | |
Disconnected Detection | | |
| | | | |
| | | | |
| | MN Attachment | |
| | | | |
| | | | |
|----Rtr Sol------------->| | |
| | | | |
| | |--PBU----->| |
| | | | |
| | |<-----PBA--| |
| | | | |
|<-----------MLD Query----| | |
| | | | |
|----MLD Report---------->| | |
| | | | |
| | |----Aggregated------->|
| | | MLD Report |
| | | | |
|<------------------------|<---Multicast Data----|
| | | | |

Figure 5: Multicast Mobility Signaling for Direct Routing

Figure 5 shows the handover operation procedure for the direct
routing operation mode. When MN1 hands off to the next MAG (N-MAG)
from the previous MAG (P-MAG), the N-MAG detects the newly arrived
attached mobile node and performs binding update procedure by
exchanging PBU/PBA signaling messages with LMA. At the same time, an
MLD proxy instance detecting MN1 transmits an MLD query message to
the mobile node. After receiving the MLD query message, MN1 sends an
MLD report message that includes the multicast group information.
The N-MAG then sends an aggregated MLD report message to the upstream
link associated with the MR. An upstream interface of MLD proxy
instance is chosen towards certain multicast router. The upstream
interface selection can be done according to dynamic policies
conveyed in the Dynamic IP Multicast Selector option (as described in
Section 5.1) or according to manually configured policies. Note that
in the base solution defined in [RFC6224], the interface selection is
determined for each MN based on the Binding Update List. When the

Zuniga, et al. Experimental [Page 13]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

N-MAG receives the multicast packets from the MR, it then simply
forwards them without tunnel encapsulation. The N-MAG updates MN1's
location information to the LMA by exchanging PBU/PBA signaling
messages.

5. Local Mobility Anchor Operation

This section includes a new mobility option to support dynamic
policies on subscription via MTMA/direct routing based on the local
mobility anchor conveying the required info to the mobile access
gateway in the proxy binding acknowledgement message.

5.1. Dynamic IP Multicast Selector Option

5.1.1. Option Application Rules

A new TLV-encoded mobility option, the Dynamic IP Multicast Selector
option, is defined for use with the proxy binding acknowledgement
message exchanged between an LMA and a MAG to convey dynamic policies
on subscription via MTMA/direct routing. This option is used for
exchanging the IP addresses of both the group subscribed to by the
MN, and the source(s) delivering it, as well as the applicable filter
mode. This information is carried by using directly the Multicast
Address Record format defined in [RFC3810]. There can be multiple
"Dynamic IP Multicast Selector" options present in the message, up to
one for each active subscription maintained by the MN.

5.1.2. Option Format

The format of this new option is as follows:

Zuniga, et al. Experimental [Page 14]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol |M| Reserved |Nr of Mcast Address Records (N)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Multicast Address Record [1] +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Multicast Address Record [2] +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Multicast Address Record [N] +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type:

54

Length:

8-bit unsigned integer indicating the length of the option in
octets, excluding the type and length fields.

Protocol:

Field used to identify the multicast membership protocol in use,
and the corresponding format of the next Multicast Address Record.
This field maps the type codification used in the original MLD
specifications for the Report message, namely for MLDv2 [RFC3810]
the Protocol value MUST be 143, whereas for MLDv1 [RFC2710] the
Protocol value MUST be 131.

Dynamic IP Multicast Selector Mode Flag (M-bit):

This field indicates the subscription via MTMA/direct routing
mode. If the (M) flag value is set to a value of (1), it is an
indication that the IP multicast traffic associated with the
multicast group(s) identified by the Multicast Address Record(s)

Zuniga, et al. Experimental [Page 15]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

in this mobility option SHOULD be routed locally (subscription via
direct routing mode). If the (M) flag value is set to a value of
(0), it is an indication that IP multicast traffic associated with
the multicast group(s) identified by the Multicast Address Record
in this mobility option(s) SHOULD be routed to the home network,
via the MTMA (subscription via MTMA mode). The mobile access
gateway MAY also choose to use static pre-established policies
instead of following the indications provided by the local
mobility anchor. All other IP traffic associated with the mobile
node is managed according to a default policy configured at the
PMIPv6 multicast domain.

Reserved:

This field is unused for now. The value MUST be initialized to 0
by the sender and MUST be ignored by the receiver.

Nr of Mcast Address Records (N)

16-bit unsigned integer indicating the number of Mcast Address
Records (N) present in this option.

Multicast Address Record:

Multicast subscription information corresponding to a single
multicast address as defined in [RFC3810], or as defined in
[RFC2710] for MLDv1.

6. Multicast Tree Mobility Anchor Operation

The MTMA provides connectivity to the multicast infrastructure out of
the PMIPv6 domain. The MTMA itself either could act as an additional
MLD proxy (only in the case where all the connected mobile access
gateways act also as MLD proxies), reporting to a further node an
aggregated view of the subscriptions in a PMIPv6 multicast domain, or
can act as a designated multicast router for all the MAGs in a PMIPv6
multicast domain. The multicast tree mobility anchor will then
request the multicast content on behalf of the MAGs (and mobile nodes
behind them). In addition, the MTMA will create and maintain the
corresponding multicast forwarding states per each tunnel interface
towards the MAGs. Whatever the role played, when the MAGs act as MLD
proxy, the MTMA becomes the MLD querier of the MLD proxy instance
located in each MAG.

Zuniga, et al. Experimental [Page 16]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

6.1. Conceptual Data Structures

The multicast tree mobility anchor does not directly interact with
the mobile nodes attached to any of the mobile access gateways. The
MTMA only manages the multicast groups subscribed per MAG on behalf
of the MNs attached to it. Having this in mind, the relevant
information to be stored in the MTMA should be the tunnel interface
identifier (tunnel-if-id) of the bidirectional tunnel for multicast
between the MTMA and every MAG (e.g., similar to what is stated in
[RFC5213] for the unicast case), the IP addresses of the multicast
group delivered per tunnel to each of the MAGs, and the IP addresses
of the sources injecting the multicast traffic per tunnel to the
multicast domain defined by the MTMA.

7. Mobile Node Operation

The mobile node operation is not impacted by the existence of an MTMA
as anchor for the multicast traffic being subscribed or the use of
direct routing. The MN will act according to the stated operations
in [RFC5213] and [RFC6224].

This document considers that every mobile node requesting multicast-
only services is previously registered in a PMIPv6 unicast domain to
get a unicast IP address. The registration can also be required for
several purposes such as remote management, billing, multicast
configuration, etc.

A given mobile node's policy profile information must be updated to
be able to store the IPv6 addresses of both the local mobility anchor
and multicast tree mobility anchor, the later for the subscription
via MTMA case.

8. IPv4 Support

This document does not introduce any IPv4-specific issue regarding
[RFC5844]. In order for the solution to support IPv4, all the
described network elements (i.e., MAG, MTMA, and MR) must support
IGMP. In this case, the functionalities of the MAG and MTMA would be
as described in [RFC6224], with the MTMA replicating the requirements
described for the LMA. For the case of the MR, it must also be dual-
stack (i.e., IPv6/IPv4) enabled.

Although references to "MLD proxy" have been used in the document, it
should be understood to also include "IGMP/MLD proxy" functionality.

Regarding the Dynamic IP Multicast Selector Option format, it SHOULD
consider IPv4 compatibility in the following way:

Zuniga, et al. Experimental [Page 17]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

Protocol field:

For IPv4, this field maps the type codification used in the
original IGMP specifications for the Report message, in the
following way:

It MUST be 0x12 in case of using IGMPv1.

It MUST be 0x16 in case of using IGMPv2.

It MUST be 0x22 in case of using IGMPv3.

Multicast Address Record field:

This field takes different formats depending on the IGMP version
being used by the MN, as follows:

* For IGMPv1, it takes the format given by the Group Address in
[RFC1112].

* For IGMPv2, it takes the format given by the Group Address in
[RFC2236].

* For IGMPv3, it takes the format given by the Group Record in
[RFC3376].

9. IANA Considerations

This document defines a new mobility option, the Dynamic IP Multicast
Selector, which has been assigned the Type 54 by IANA. The Type
value for these options has been assigned from the same numbering
space as allocated for the other mobility options, as defined in
[RFC6275]: http://www.iana.org/assignments/mobility-parameters.

10. Security Considerations

This document describes two complementary operational modes that can
be used to deliver multicast traffic in a PMIPv6 domain: multicast
anchor and direct routing. Different approaches are described in the
document to decide which operational mode is selected: i) the use of
pre-configured/pre-provisioned policies at the mobile access gateway,
or ii) the use of dynamic policies. Approach ii) could introduce a
potential security issue if the protocol signaling is not properly
secured. The use of the Dynamic IP Multicast Selector option
described in the document requires message integrity protection and
source authentication. Hence, the IPsec security mechanism

Zuniga, et al. Experimental [Page 18]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

recommended by Proxy Mobile IPv6 [RFC5213] MUST be used to secure the
Dynamic IP Multicast Selector option conveyed in the PBA (Proxy
Binding Acknowledgement).

This document does not introduce any additional security threats
beyond the current security considerations of PMIPv6 [RFC5213], MLD
[RFC3810], IGMP [RFC3376], and IGMP/MLD Proxying [RFC4605].

11. Contributors

The following individuals made significant contributions to this
document.

Akbar Rahman
InterDigital Communications, LLC
EMail: [email protected]

Ignacio Soto
Universidad Carlos III de Madrid
EMail: [email protected]

Zuniga, et al. Experimental [Page 19]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

12. References

12.1. Normative References

[RFC1112] Deering, S., "Host extensions for IP multicasting",
STD 5, RFC 1112, August 1989.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2236] Fenner, W., "Internet Group Management Protocol, Version
2", RFC 2236, November 1997.

[RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710,
October 1999.

[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.

[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol,
Version 3", RFC 3376, October 2002.

[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

[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.

[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury,
K., and B. Patil, "Proxy Mobile IPv6", RFC 5213,
August 2008.

[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.

[RFC5847] Devarapalli, V., Koodli, R., Lim, H., Kant, N.,
Krishnan, S., and J. Laganier, "Heartbeat Mechanism for
Proxy Mobile IPv6", RFC 5847, June 2010.

[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, July 2011.

Zuniga, et al. Experimental [Page 20]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

12.2. Informative References

[AUTO] Bumgardner, G., "Automatic Multicast Tunneling", Work in
Progress, July 2013.

[MLDPROXY] Asaeda, H. and S. Jeon, "Multiple Upstream Interface
Support for IGMP/MLD Proxy", Work in Progress,
February 2013.

[MUIIMP] Zhang, H. and T. Schmidt, "Multi-Upstream Interfaces
IGMP/MLD Proxy", Work in Progress, July 2013.

[MULTIMOB] Schmidt, T., Gao, S., Zhang, H., and M. Waehlisch,
"Mobile Multicast Sender Support in Proxy Mobile IPv6
(PMIPv6) Domains", Work in Progress, July 2013.

[PMIP6-REQ] Deng, H., Chen, G., Schmidt, T., Seite, P., and P. Yang,
"Multicast Support Requirements for Proxy Mobile IPv6",
Work in Progress, July 2009.

[RFC6224] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in Proxy
Mobile IPv6 (PMIPv6) Domains", RFC 6224, April 2011.

[UPSTREAM] Contreras, LM., Bernardos, CJ., and JC. Zuniga,
"Extension of the MLD proxy functionality to support
multiple upstream interfaces", Work in Progress,
February 2013.

Zuniga, et al. Experimental [Page 21]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

Appendix A. MTMA Deployment Use Cases

This informative appendix describes, from the network architecture
point of view, several deployment options considering the MTMA.

These options can be distinguished in terms of the number of LMAs and
MTMAs present in a PMIPv6 domain and the service relationship that a
set of MNs gets from them, in the form of a "LMA : MTMA" ratio.
According to that, it is possible to differentiate the following
approaches:

o A set of MNs is served in a PMIPv6 domain by two entities, one
MTMA for multicast service, and one LMA for unicast, in such a way
that the ratio is 1:1 (one common PMIPv6 unicast and multicast
domain).

o A set of MNs is served in a PMIPv6 domain by several entities, one
MTMA for multicast service, while the others (LMAs) for unicast,
in such a way that the ratio is N:1 (N PMIPv6 unicast domains
coexist with a unique multicast domain).

o A set of MNs is served in a PMIPv6 domain by several entities, one
LMA for unicast, while the others (MTMAs) are devoted to multicast
service, in such a way that the ratio is 1:N (one single PMIPv6
unicast domain coexists with multiple multicast domains).

Scenarios with an N:M ratio are considered to be a combination of the
previous ones.

A.1. PMIPv6 Domain with Ratio 1:1

This approach refers to the architecture presented in Figure 1.
Within this approach, a common set of MNs is served by a couple of
entities, one LMA for unicast and one MTMA for multicast. All the
MNs of the set are served by these two elements as they move in the
PMIPv6 domain.

A.2. PMIPv6 Domain with Ratio N:1

This approach refers to the situation where a common set of MNs is
served by a unique MTMA for multicast service, but simultaneously
there are subsets from that group of MNs that are served by distinct
LMAs for unicast service as they move in the PMIPv6 domain. Each
particular MN association with the LMAs (unicast) and MTMA
(multicast) remains always the same as it moves in the PMIPv6 domain.

Figure 6 shows the scenario here described.

Zuniga, et al. Experimental [Page 22]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| |
*** *** *** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** *** *** *** ***
| | |
| | |
| | |
+------+ +-----------------+ +------+
| LMA1 | | MTMA2 | | LMA3 |
+------+ +-----------------+ +------+
|| \\ oo oo oo oo // ||
|| \\ oo oo oo oo // ||
|| \\ oo oo oo oo // ||
|| \\ oo oo oo oo // ||
|| \\oo oo oo oo // ||
|| \\ oo oo oo// ||
|| oo\\ oo oo // ||
|| oo \\ oo oo //oo ||
|| oo \\ oo oo // oo ||
|| oo \\ oo oo // oo ||
+------+ +--------+ +--------+ +--------+
| MAG1 | | MAG2 | | MAG3 | | MAG4 |
+------+ +--------+ +--------+ +--------+
| | | | | | | |
| | | | | | | |
{MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41}

Figure 6: PMIPv6 Domain with Ratio N:1

Figure 6 proposes an architecture where there are two entities acting
as LMAs, LMA1 and LMA3, while there is another one, named MTMA2,
working as multicast tree mobility anchor. LMA1 and LMA3 constitute
two distinct unicast domains, whereas MTMA2 forms a single multicast
domain. The tunnels among MAGs and LMAs represented by lines ("||")
indicate a tunnel transporting unicast traffic, while the tunnels
among MAGs and MTMA2 depicted with circles ("o") show a tunnel
transporting multicast traffic.

In the figure, it can be observed that all the MNs are served by
MTMA2 for the incoming multicast traffic from sources A or B.

Zuniga, et al. Experimental [Page 23]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

However, there are different subsets regarding unicast traffic, which
maintain distinct associations within the PMIPv6 domain. For
instance, the subset formed by MN10, MN11, MN20, and MN21 is served
by LMA1 for unicast, and the rest of MNs are served by LMA3. For the
scenario described above, the association between each MN and the
corresponding LMA and MTMA is permanently maintained.

A.3. PMIPv6 Domain with Ratio 1:N

This approach is related to a scenario where a common group of MNs is
served by a unique LMA for unicast service, but simultaneously there
are subsets from that group of MNs that are served by distinct MTMAs
for multicast service as they move in the PMIPv6 domain. Different
MTMAs might be associated with serving different multicast groups.
These associations remain the same even if the MNs move within the
PMIPv6 domain.

Figure 7 shows the scenario here described.

Zuniga, et al. Experimental [Page 24]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| ******************** |
( ) * * ( )
( ) * Fixed Internet * ( )
( ) * (Unicast Traffic) * ( )
( ) * * ( )
( ) ******************** ( )
| | |
| | |
+------+ +--------------+ +------+
| MTMA1| | LMA2 | | MTMA3|
+------+ +--------------+ +------+
oo oo // \\ ^^ ^^
oo oo // \\ ^^ ^^
oo oo // \\ ^^ ^^
oo oo // \\ ^^ ^^
oo oo/ ^^ ^^
oo //oo ^^ \\ ^^
oo // oo ^^ \\ ^^
oo // oo \\ ^^
oo // ^^ oo \\ ^^
oo // ^^ oo \^^
+-------------+ +-------------+
| \ / | | \ | |
| ~o~~~~o~ | | ~o~~~~o~ |
| ( MLD w ) | | ( MLD w ) |
| ( multip ) | | ( multip ) |
| ( i/f ) | | ( i/f ) |
| ~~~~~~~~ | | ~~~~~~~~ |
| | | |
| MAG1 | | MAG2 |
/+-------------+ +-------------+\
| | | | | |
| | | | | |
{MN10} {MN11} {MN12} {MN20} {MN21} {MN22}

Figure 7: PMIPv6 Domain with Ratio 1:N

Figure 7 proposes an architecture where the LMA2 is the unique LMA
for a certain group of MNs, while there are two other entities, MTMA1
and MTMA3, acting as MTMAs for different subsets of multicast
content. MTMA1 and MTMA3 constitute two distinct multicast domains,
whereas LMA2 forms a single unicast domain. Each MTMA could be
devoted to carry on a different content (for instance, MTMA1 for
source A and MTMA3 for source B). Looking at the figure, all MNs are

Zuniga, et al. Experimental [Page 25]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

served by LMA2 for unicast, while they might be simultaneously served
by MTMA1 and MTMA3, depending on the multicast content. For the
scenario described above, the association between multicast content
and MTMA is permanently maintained. Note that this scenario would
require support for MLD proxy with multiple interfaces [MULTIMOB],
[UPSTREAM], [MLDPROXY], [MUIIMP] at the MAGs.

A.4. PMIPv6 Domain with H-LMA

The H-LMA is defined as an entity that simultaneously transports
unicast and multicast service, that is, it simultaneously works as
LMA and MTMA. In the context of the MTMA solution, an H-LMA can play
the role of MTMA for an entire group of MNs in a PMIPv6 domain, while
acting simultaneously as LMA for a subset of them. Figure 8 adapts
the PMIPv6 domain with ratio N:1 scenario of Figure 6 to the case
where MTMA2 is an H-LMA, which serves multicast traffic to all the
MNs in the picture, and simultaneously, it is able to serve unicast
traffic to the subset formed by MN21 and MN30.

Zuniga, et al. Experimental [Page 26]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| |
*** *** *** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** *** *** *** ***
| | |
| | |
| | |
+------+ +-----------------+ +------+
| LMA1 | | H-LMA | | LMA3 |
+------+ +-----------------+ +------+
|| \\ oo db db oo // ||
|| \\ oo db db oo // ||
|| \\ oo db db oo // ||
|| \\ oo db db oo // ||
|| \\oo db db oo // ||
|| \\ db db oo// ||
|| oo\\ db db // ||
|| oo \\ db db //oo ||
|| oo \\ db db // oo ||
|| oo \\ db db // oo ||
+------+ +--------+ +--------+ +--------+
| MAG1 | | MAG2 | | MAG3 | | MAG4 |
+------+ +--------+ +--------+ +--------+
| | | | | | | |
| | | | | | | |
{MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41}

Figure 8: PMIPv6 Domain with H-LMA

Figure 8 presents a PMIPv6 network where there are two pure unicast
LMAs, LMA1, and LMA3, and a hybrid LMA, labeled as H-LMA in the
figure. The H-LMA is an MTMA from the perspective of MAG1 and MAG4.
The tunnels among MAGs and LMAs represented by lines ("||") indicate
a tunnel transporting exclusively unicast traffic, the tunnels
depicted with circles ("o") show a tunnel transporting exclusively
multicast traffic, and the tunnels with mixed lines and circles
("db") describe a tunnel transporting both types of traffic
simultaneously.

Zuniga, et al. Experimental [Page 27]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

All of the MNs in the figure receive the multicast traffic from H-LMA
(one single multicast domain), but it is possible to distinguish
three subsets from the unicast service perspective (that is, three
unicast domains). The first subset is the one formed by MN10, MN11,
and MN20, which receives unicast traffic from LMA1. A second subset
is the one formed by MN21 and MN30, which receives unicast traffic
from H-LMA. And finally, a third subset is built on MN31, MN40, and
MN41, which receives unicast traffic from LMA3. For the scenario
described above, the association between each MN and the
corresponding LMA and H-LMA is permanently maintained.

Zuniga, et al. Experimental [Page 28]

RFC 7028 Multicast Mobility Routing Optimizations September 2013

Authors' Addresses

Juan Carlos Zuniga
InterDigital Communications, LLC
1000 Sherbrooke Street West, 10th floor
Montreal, Quebec H3A 3G4
Canada
EMail: [email protected]
URI: http://www.InterDigital.com/

Luis M. Contreras
Telefonica I+D
Don Ramon de la Cruz, 82-84
Madrid 28006
Spain
EMail: [email protected]

Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
EMail: [email protected]
URI: http://www.it.uc3m.es/cjbc/

Seil Jeon
Instituto de Telecomunicacoes
Campus Universitario de Santiago
Aveiro 3810-193
Portugal
EMail: [email protected]
URI: https://atnog.av.it.pt/~sjeon/

Younghan Kim
Soongsil University
Sangdo-dong, Dongjak-gu
Seoul 511
Republic of Korea
EMail: [email protected]
URI: http://dcnlab.ssu.ac.kr/

Zuniga, et al. Experimental [Page 29]