Internet DRAFT - draft-zuniga-multimob-pmipv6-ropt
draft-zuniga-multimob-pmipv6-ropt
MULTIMOB Group J. C. Zuniga
INTERNET-DRAFT (InterDigital Communications, LLC)
Intended Status: Standards Track L. M. Contreras
Expires: May 2, 2012 (Telefonica I+D)
C. J. Bernardos
(Universidad Carlos III de Madrid)
S. Jeon
Y. Kim
(Soongsil University)
October 30, 2011
Multicast Mobility Routing Optimizations for Proxy Mobile IPv6
<draft-zuniga-multimob-pmipv6-ropt-01.txt>
Abstract
The MULTIMOB group has specified a base solution to support IP
multicasting in a PMIPv6 domain [RFC6224]. In this document, some
enhancements are proposed to the base solution. 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 MAG can provide access to multicast content
in the local network. These enhancements provide benefits such as
reducing multicast traffic replication and supporting different
PMIPv6 deployments scenarios.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
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The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Copyright and License Notice
Copyright (c) 2011 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
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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 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Conventions and Terminology . . . . . . . . . . . . . . . . . . 4
3 Multicast Tree Mobility Anchor (MTMA) . . . . . . . . . . . . . 5
3.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 7
3.2.1 PMIPv6 domain with ratio 1:1 . . . . . . . . . . . . . 8
3.2.2 PMIPv6 domain with ratio N:1 . . . . . . . . . . . . . 8
3.2.3 PMIPv6 domain with ratio 1:N . . . . . . . . . . . . 10
3.2.4 PMIPv6 domain with H-LMA . . . . . . . . . . . . . . 11
3.3 Multicast Establishment . . . . . . . . . . . . . . . . . 14
3.4 Multicast Mobility . . . . . . . . . . . . . . . . . . . 15
3.5 PMIPv6 enhancements . . . . . . . . . . . . . . . . . . . 16
3.5.1 New Binding Update List in MAG . . . . . . . . . . . 16
3.5.2 Policy Profile Information with Multicast Parameters 17
3.5.3 MAG to MTMA attach requirements . . . . . . . . . . 17
3.5.4. Data structure stored by MTMA . . . . . . . . . . . 17
3.6 Advantages . . . . . . . . . . . . . . . . . . . . . . . 17
4 Direct routing . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 MAG as MLD proxy . . . . . . . . . . . . . . . . . . . . . 22
4.1.1 Local subscription when the MAG implements MLD proxy
functionality . . . . . . . . . . . . . . . . . . . 22
4.1.1.1 Local subscription architecture . . . . . . . . 22
4.1.1.2 Handover procedure for local routing . . . . . . 23
4.1.2 Remote subscription when the MAG implements MLD
proxy functionality . . . . . . . . . . . . . . . . . 24
4.2 MAG as multicast router . . . . . . . . . . . . . . . . . 25
4.2.1 Local subscription when the MAG implements a
multicast routing protocol . . . . . . . . . . . . . 25
4.2.2 Remote subscription when the MAG implements a
multicast routing protocol . . . . . . . . . . . . . 25
5 Dynamic selection of local versus remote multicast subscription 25
5.1 Any source multicast scenario . . . . . . . . . . . . . . 26
5.2 Source specific multicast scenario . . . . . . . . . . . . 26
6 Security Considerations . . . . . . . . . . . . . . . . . . . 27
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
8 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1 Normative References . . . . . . . . . . . . . . . . . . 27
9.2 Informative References . . . . . . . . . . . . . . . . . 28
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
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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 does 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.
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 (MLDv2)
[RFC3810] is used in a similar way by IPv6 routers to discover the
presence of IPv6 multicast hosts. Also, the IGMP/MLD proxy [RFC4605]
allows an intermediate (edge) node to appear as a multicast router to
downstream hosts, and as a host to upstream multicast routers. IGMP
and MLD related protocols were not originally designed to address IP
mobility of multicast listeners (i.e. IGMP and MLD protocols were
originally designed for fixed networks).
The MULTIMOB group has specified a base solution to support IP
multicast listener mobility in a PMIPv6 domain [RFC6224], which
describes deployment options without modifying mobility and multicast
protocol standards. The PMIPv6 allows a MAG to establish a multiple
of PMIPv6 tunnels with LMAs. Hence, when IP multicasting is applied
into PMIPv6, it leads to redundant traffic at a MAG called "Tunnel
Convergence problem". To address this issue, two enhancements are
proposed in this document; multicast anchor and direct routing. The
former uses a multicast tree mobility anchor (MTMA) as the
topological anchor point for delivering multicast traffic, while the
latter uses direct routing, allowing a MAG to connect directly to a
multicast router for simple access to local content. Both schemes
have no impact on the MN to support multicast listener mobility.
The MTMA architecture and solution are described in section 3.
Section 4 describes the direct routing solution and the enhancements
details. Section 5 describes the details about the selection at the
MAG between direct routing (e.g. for local access) and MTMA (e.g. for
remote access).
2 Conventions and 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].
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This document uses the terminology defined in [RFC5213], [RFC3775],
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 draft we refine such 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 in such a way that
an MN using that service is not aware of mobility as it moves from
one MAG to another associated to that LMA regarding its 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.
- Direct routing: it uses native multicast infrastructure for
retrieving multicast data. For the operator having its own local
content, this technique also includes the case that content source
is directly connected to a MAG.
This means 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 exclusively.
- H-LMA or Hybrid-LMA: an entity dedicated to both unicast and
multicast services, that is, it is able to work as both LMA and
MTMA simultaneously.
3 Multicast Tree Mobility Anchor (MTMA)
A PMIPv6 domain may handle data from both unicast and multicast
sources. This document addresses optimizations to the base solution
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specified for multicast support in PMIPv6 domains [RFC6224] by
firstly introducing a complementary network entity, named multicast
tree mobility anchor (MTMA), and defining the architecture and
protocol flows derived from it; and secondly by defining a direct
routing option where a MAG can directly receive packets from a
multicast router.
An MTMA can be used to serve as the mobility anchor for multicast
traffic. The MTMA connects to the MAG 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 LMAs in the PMIPv6 domain.
This section describes how the MTMA works in scenarios of MN
attachment and multicast mobility. We first concentrate on the case
of both LMA and MTMA defining a unique PMIPv6 domain, and then
different deployment scenarios are presented.
3.1 Architecture
Figure 1 shows an example of a PMIPv6 domain supporting multicast
mobility. LMA1 is dedicated to unicast traffic, and MTMA1 is
dedicated to multicast traffic. The tree mobility anchor MTMA1 can be
considered to be a form of upstream multicast router with tunnel
interfaces allowing remote subscription for the MNs. Note that there
can be multiple LMAs for unicast traffic (not shown in Figure 1) in a
given PMIPv6 domain. Similarly, more than one MTMA can be deployed by
the operator (not shown in Figure 1).
Also in this architecture, all MAGs that are connected to the MTMA
must support the MLD proxy [RFC4605] function. Specifically in Figure
1, each of the MAG1-MTMA1 and MAG2-MTMA1 tunnel interfaces defines an
MLD proxy domain. The MNs are considered to be on the downstream
interface of the MLD proxy (in the MAG), and MTMA1 is considered to
be on the upstream interface (of the MAG) as per [RFC4605]. Note
that MAG could also be an IGMP proxy. For brevity this document will
refer primarily to MLD proxy, but all references to "MLD proxy"
should be understood to also include "IGMP/MLD proxy" functionality.
As shown in Figure 1, MAG1 may connect to both unicast (LMAs) and
multicast (MTMAs) 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, despite of that, this draft
considers that every MN demanding multicast-only services is
previously registered in a PMIPv6 unicast domain to get a unicast IP
address. This registration can be required also for several purposes
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such as remote management, billing, etc.
+--------------+
|Content Source|
+--------------+
|
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* Unicast Traffic * * Multicast Traffic *
* * * *
* ** ** ** * * ** ** ** *
*** *** *** *** *** *** *** ***
| |
| |
| |
+-----+ +------+
Unicast | LMA1| | MTMA1| Multicast
Anchor +-----+ +------+ Anchor
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
+-----+ +-----+
| MAG1| | MAG2| MLD Proxy
+-----+ +-----+
| | |
| | |
{MN1} {MN2} {MN3}
Figure 1. Architecture of Multicast Tree Mobility Anchor (MTMA)
3.2 Deployment Scenarios
From the network architecture point of view, there are several
options when considering the multicast tree mobility anchor (MTMA)
approach. 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:
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- 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).
- 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).
- 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.
3.2.1 PMIPv6 domain with ratio 1:1
This approach basically 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.
3.2.2 PMIPv6 domain with ratio N:1
This approach basically 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 which 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 2 shows the scenario here described.
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+----------------+ +----------------+
|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 2. PMIPv6 domain with ratio N:1
The figure 2 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. However,
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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 being served by LMA3. For the
scenario described above, the association between each MN and the
corresponding LMA and MTMA is permanently maintained.
3.2.3 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 which are served by distinct MTMAs
for multicast service as they move in the PMIPv6 domain. Each
particular MN association with the LMA and MTMAs (unicast and
multicast respectively) remains always the same as it moves in the
PMIPv6 domain.
Figure 3 shows the scenario here described.
The figure 3 proposes an architecture where the LMA2 is the unique
LMA for a certain group of MNs, while there are two others entities,
MTMA1 and MTMA3, acting as MTMAs for different subsets of MNs of the
same group. 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) or not. Looking at the picture, the
subset formed by MN10, MN11, MN20 and MN21 is served by MTMA1 for
multicast. The rest of MNs are being served by MTMA3 also for
multicast. Finally, all of them are served by LMA2 for unicast. For
the scenario described above, the association between each MN and the
corresponding LMA and MTMA is permanently maintained.
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+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| |
*** *** *** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** *** *** *** ***
| | |
| | |
| | |
+-------+ +-----------------+ +-------+
| MTMA1 | | LMA2 | | MTMA3 |
+-------+ +-----------------+ +-------+
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 \\ oo
+------+ +--------+ +--------+ +--------+
| MAG1 | | MAG2 | | MAG3 | | MAG4 |
+------+ +--------+ +--------+ +--------+
| | | | | | | |
| | | | | | | |
{MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41}
Figure 3. PMIPv6 domain with ratio 1:N
3.2.4 PMIPv6 domain with H-LMA
The H-LMA is defined as an entity which 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. The figure 4
adapts the PMIPv6 domain with ratio N:1 scenario of figure 2 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
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unicast traffic to the subset formed by MN30, MN40 and MN41.
Figure 4 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.
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 MN 20, 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.
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+----------------+ +----------------+
|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 4. PMIPv6 domain with H-LMA
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3.3 Multicast Establishment
Figure 5 shows the procedure when MN1 attaches to MAG1, and
establishes associations with LMA (unicast) and MTMA (multicast).
MN1 MAG1 LMA MTMA
| (MLD Proxy) (Unicast) (Multicast)
MN attaches to MAG1 | | |
| | | |
|------Rtr Sol----- ->| | |
| |--PBU -- >| |
| | | |
| |<-- PBA --| |
| | | |
| |=Unicast= | |
| | Tunnel | |
|<-----Rtr Adv ------ | | |
| | | |
|< ------ Unicast Traffic------ >| |
| | | |
| |==Multicast Tunnel ==|
| | | |
|<--MLD Query --------| | |
| | | |
MN requires | | |
multicast services | | |
| | | |
|---MLD Report (G) -->| | |
| | | |
| |---- Aggregated ---> |
| | MLD Report (G) |
| | | |
| | | |
|< --------- Multicast Traffic ----------- >|
| | | |
Figure 5. MN Attachment and Multicast Service Establishment
In Figure 5, MAG1 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 MAG1 and MTMA. Or the multicast tunnel may be
dynamically established when the first MN appears at the MAG.
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MN1 sends the MLD report message (when required by its upper layer
applications) as defined in [RFC3810] in response to an MLD Query
from MAG1. MAG1 acting as a MLD Proxy as defined in [RFC4605] will
then send an Aggregated MLD Report to the multicast anchor, MTMA
(assuming that this is a new multicast group which MAG1 had not
previously subscribed to). Multicast traffic will then flow from
MTMA towards MN1.
3.4 Multicast Mobility
Figure 6 illustrates the mobility scenario for multicast traffic.
Specifically, MN2 with ongoing multicast subscription moves from MAG1
to MAG2. Note that, for simplicity, in this scenario we only
consider the tunnel of MAG2 with MTMA (for multicast traffic) and we
assume that MN2 does not receive unicast traffic. Of course, if it
was desired to support unicast traffic, this is served by a tunnel
between MAG2 and LMA to transfer unicast traffic.
According to baseline solution signaling method described in
[RFC6224], after MN2 mobility, MAG2 acting in its role of MLD proxy
will send an MLD Query to the newly observed MN on its downlink.
Assuming that the subsequent MLD Report from MN2 requests membership
of a new multicast group (from MAG2's point of view), this will then
result in an Aggregated MLD Report being sent to MTMA from MAG2. This
message will be sent through a pre-established (or dynamically
established) multicast tunnel between MAG2 and MTMA.
When MN2 detaches, MAG1 may keep the multicast tunnel with the
multicast MTMA if there are still other MNs using the multicast
tunnel. Even if there are no MNs currently on the multicast tunnel,
MAG1 may decide to keep the multicast tunnel for potential future
use.
As discussed above, existing MLD (and Proxy MLD) signaling will
handle a large part of the multicast mobility management for the MN.
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MN2 MAG1 MAG2 LMA MTMA
| (MLD Proxy) (MLD Proxy) (Unicast)(Multicast)
| | | | |
MN Attached | | | |
To MAG1 | | | |
| | | | |
| |========= Multicast Tunnel ======= |
| | | | |
MN Detaches | | | |
From MAG1 | | | |
| | | | |
| | | | |
MN Attaches | | | |
To MAG2 | | | |
| | | | |
| | |==Multicast Tunnel === |
| | | | |
|---------Rtr Sol------ >| | |
| | |--- PBU --->| |
| | | | |
| | |<-- PBA ----| |
|<-----Rtr Adv --------- | | |
| | | | |
| | | | |
|<---------MLD Query---- | | |
| | | | |
|---MLD Report (G) ----> | | |
| | | | |
| | |---- Aggregated -----> |
| | | MLD Report (G) |
| | | | |
|< --------- Multicast Traffic ---------------- >|
| | | | |
| | | | |
Figure 6. Multicast Mobility Signaling
3.5 PMIPv6 enhancements
This section describes the enhancements to the Proxy Mobile IPv6
[RFC5213] protocol required to support the MTMA architecture.
3.5.1 New Binding Update List in MAG
The Binding Update List in the MAG must be updated to be able to
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handle the fact that more than one entity (i.e. LMA and MTMA) may be
serving the mobile node.
3.5.2 Policy Profile Information with Multicast Parameters
A given mobile node's policy profile information must be updated to
be able to store the IPv6 addresses of both the LMA and MTMA.
3.5.3 MAG to MTMA attach requirements
The MAG procedures must be updated to be able to handle simultaneous
attach for a given mobile node to both the LMA and MTMA. For example,
packets coming from a given mobile node must be screened to determine
if it should be sent to the LMA or to the MTMA.
3.5.4. Data structure stored by MTMA
The MTMA does not directly interact with the MNs attached to any of
the MAGs. 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 bi-directional tunnel for
multicast between the MTMA and every MAG (as 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.
3.6 Advantages
An advantage of the proposed MTMA architecture is that it allows a
PMIPv6 domain to closely follow a simple multicast tree topology for
Proxy MLD forwarding (cf., sections 1.1 and 1.2 of [RFC4605]). In
contrast, the combined unicast/multicast LMA as proposed in [RFC6224]
will be a more complex set of trees.
Another advantage of the proposed dedicated multicast solution is
that it allows a gradual network upgrade of a PMIPv6 domain to
support multicast functionality. This is because the operator does
not have to upgrade all the LMAs in the network to support multicast
functionality. Only certain nodes (MTMAs), dedicated to multicast
support, will have to be upgraded to support the new multicast
functionality. Also, multiple deployment scenarios are supported as
required by the operator for expected traffic distributions.
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A final advantage is that a specific multicast elements minimize the
replication of multicast packets (the Tunnel Convergence problem), in
certain scenarios, compared to [RFC6224]. Figures 7 and 8 illustrate
this point visually. For this simple scenario, it can be observed
that the multicast MTMA topology (Figure 7) generates 6 packets for
one input multicast packet. In comparison, the combined
unicast/multicast LMA topology (Figure 8) generates 8 packets for one
input multicast packet.
In general, it can be seen that the extra multiplication of packets
in the combined unicast/multicast LMA topology will be proportional
to the number of LMAs, and the number of MNs (in a given MAG)
associated to different LMAs, for a given multicast group. The
packet multiplication problem aggravates as more MNs associated to
different LMAs receive the same multicast traffic when attached to
the same MAG. Hence, the MTMA architecture significantly decreases
the network capacity requirements in this scenario.
(Note that in Figure 7, it is assumed that MN1 and MN2 are associated
with MAG1-LMA1, and MN3 is associated with MAG2-MTMA2 for multicast
traffic. In Figure 8, it is assumed that MN1 is associated with
MAG1-LMA1, MN2 is associated with MAG1-LMA2, and MN3 is associated
with MAG2-LMA2 for multicast traffic. In both Figures 7 and 8, it is
assumed that the packets are transmitted point to point on the last
hop wireless link.)
Additional results can be found in [ERCIM], where both solutions are
compared by simulation under realistic traffic conditions. It can be
shown that, for multicast traffic, the number of channels that a node
(LMA in the base solution, MTMA in the proposed multicast
architecture) has to serve does not decrease linearly with the
reduction of the number of MNs associated to that node. The key
factor is the set of channels subscribed by the MNs. In fact, as the
number of MNs increases in the PMIPv6 domain, we have less advantage
for having several nodes serving multicast, as each of them will
probably manage all the multicast channels (or at least the popular
ones) anyway.
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+--------------+
|Content Source|
+--------------+
|
|
+---+ Packet destined
| 1 | for Multicast group "G"
+---+
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* Unicast Traffic * * Multicast Traffic *
* * * *
* ** ** ** * * ** ** ** *
*** *** *** *** *** *** *** ***
| |
| +---+
| | 2 |
| +---+
| |
+-----+ +------+
Unicast | LMA1| | MTMA2| Multicast
Anchor +-----+ +------+ Anchor
\\ //||
\\ // ||
\\ // ||
\\ // ||
\\ +---+ +---+
\\ | 3 | | 4 |
\\ +---+ +---+
\\ // ||
\\ // ||
\\ // ||
\\ // ||
+-----+ +-----+
| MAG1| | MAG2| MLD Proxy
+-----+ +-----+
| | |
+---+ +---+ +---+
| 5 | | 6 | | 7 |
+---+ +---+ +---+
| | | All MNs in same
| | | multicast group "G"
{MN1} {MN2} {MN3}
Figure 7. Packet Flow in the MTMA architecture
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+--------------+
|Content Source|
+--------------+
|
|
+---+ Packet destined
| 1 | for Multicast group "G"
+---+
|
*** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** ***
| |
+---+ +---+
| 2 | | 3 |
+---+ +---+
| |
+-----+ +------+
| LMA1| | LMA2 | Combined
+-----+ +------+ Unicast/Multicast
\\ // || Anchor
\\ // ||
\\ // ||
\\ // ||
+---+ +---+ +---+
| 4 | | 5 | | 6 |
+---+ +---+ +---+
\\ // ||
\\ // ||
\\ // ||
\\ // ||
+-----+ +-----+
| MAG1| | MAG2| MLD Proxy
+-----+ +-----+
| | |
+---+ +---+ +---+
| 7 | | 8 | | 9 |
+---+ +---+ +---+
| | | All MNs in same
| | | multicast group "G"
{MN1} {MN2} {MN3}
Figure 8. Packet Flow in a Combined Unicast/Multicast LMA
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4 Direct routing
Direct routing uses native multicast infrastructure, allowing a MAG
to connect a multicast router directly. A MAG can act as a MLD proxy
or multicast router for redirecting multicast packets. The key idea
of direct routing is to provide optimal routing for local content. As
a consequence, it does not give the LMA processing burden for channel
management and data delivery of locally available content. Direct
routing is simple and easy to deploy.
When thinking on the MAG reception of the multicast flow being
forwarded to the attached MNs, two models for the MAG subscription to
the multicast flow (on behalf of the MNs) can be considered:
- Local subscription, which refers to the situation where the
multicast channel is forwarded to the MAG by a multicast router
within the PMIPv6 domain
- Remote subscription, which refers to the situation where the
multicast channel is forwarded to the MAG through the tunnel
interface from the home network
In the architecture described in [RFC6224], if MLD proxy is installed
on a MAG, all MAGs that participate in the multicast traffic
distribution in a PMIPv6 domain are considered to act as MLD proxies.
An important consequence derived from such characterization is that
every MLD proxy instance defined in the MAG has a unique upstream
interface, and thus, an MLD proxy instance cannot dynamically choose
among local or remote multicast subscription. For instance, one
possible scenario pushing for local source deployment, and
consequently local subscription, could be the one where there is an
extremely high number of multicast channels, all of them with active
subscriptions in all the MAGs along the PMIPv6 domain, resulting in
the MTMA replicating the totally of the multicast flows to all the
MAGs (leading to the known as "avalanche problem").
Once a decision is taken (at configuration time) about what kind of
subscription, either local or remote, is applicable for a certain
instance regarding all the multicast channels for all the attached
MNs, this cannot be changed without resetting and reconfiguring the
whole MLD instance.
In order to have such kind of flexibility, the MAG needs to act as a
multicast router, that is, it must implement some multicast routing
protocol able to choose between local or remote subscription, for one
or all the subscribed multicast channels, by using some routing
criteria leveraged by the network routing information or by the
network management systems. The most commonly deployed multicast
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routing protocol nowadays is PIM [RFC4601].
So it is possible to distinguish among two situations depending on
the MAG functionality. The following sub-sections describe the
applying constraints.
4.1 MAG as MLD proxy
In case of the MAG only incorporates MLD proxy functionality, for
every one of the MLD proxy instances invoked in the MAG it is
necessary to define at configuration time the upstream interface from
where the multicast traffic will be received. This decision actually
requires to define whether the multicast subscription by an MLD proxy
instance for all the multicast channels will be local (if the
upstream interface points to a multicast router internal to the
PMIPv6 domain) or remote (in case of the upstream interface is the
bi-directional tunnel towards the LMA, for the architecture in
[RFC6224], or the MTMA, for the multicast listener optimization
described in this document).
4.1.1 Local subscription when the MAG implements MLD proxy functionality
If the MAG has MLD proxy functionality only, once this MLD proxy
instance is configured to obtain the multicast traffic locally, the
system behavior when operating with local subscription remains
static.
4.1.1.1 Local subscription architecture
Figure 9 shows the proposed local routing architecture using native
multicasting infrastructure [I-D.deng-multimob-pmip6-requirement]. To
forward IGMP/MLD signaling and multicast packets, a MLD proxy
function defined in [RFC4605], SHOULD be placed on a MAG. This
solution is much simpler than the base solution and easy to deploy
because multicasting functions are totally separated from mobility
anchor by using a native multicasting infrastructure.
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Multicast Tree
:
: || - PMIPv6 Tunnel
+----------+ +----------+ | - Multicast Data Path
| LMA | | MR |
+----------+ +----------+
||\\ /|
|| \\ / |
|| \\ / |
|| \\ / |
|| \\/ |
|| / \\ |
|| / \\ |
|| / \\ |
+----------+ +----------+
| P-MAG | | N-MAG |
|(M-Proxy) | |(M-Proxy) |
+----------+ +----------+
: :
+------+ +------+
| MN | -----> | MN |
+------+ +------+
Figure 9. Direct routing solution for PMIPv6 Multicasting
4.1.1.2 Handover procedure for local routing
Figure 10 shows the handover operation in local routing architecture.
When an MN hands off to the next MAG (N-MAG) from the previous MAG
(P-MAG), the N-MAG detects the newly arrived MN and transmits an MLD
query message to the MN. After receiving the MLD query message, the
MN sends an MLD report message that includes the multicast group
information. The N-MAG then sends an aggregated MLD report message to
the MR. When the N-MAG receives the multicast packets from the MR, it
then simply forwards them without tunnel encapsulation. The N-MAG
updates the MN's location information to the LMA by exchanging
PBU/PBA signaling messages.
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MN P-MAG N-MAG LMA MR Tree
| | | | | |
| | | | | |
|<----------|<-- Multicast Data--------------|<-------|
| | . | | | |
| | . | | | |
| | . | | | |
Link->| Handover | | | |
Disconnected Detection | | | |
| | | | | |
| | | | | |
| | MN Attachment | | |
| | | | | |
| | | | | |
|------ Rtr. Sol. ----->| | | |
| | | | | |
|<----- MLD Query ------| | | |
| | | | | |
|------ MLD Report ---->| | | |
| | | Aggregated | |
| | |--- MLD Report ---->| |
| | | | | |
| | | | | |
|<----------------------|<-- Multicast Data--|<-------|
| | | | | |
| | | | | |
| | | Proxy | | |
| | |--Binding->| | |
| | | Update | | |
| | | | | |
| | | Proxy | | |
| | |<-Binding--| | |
| | | Ack. | | |
| | | | | |
Figure 10. Handover procedure in direct routing architecture
4.1.2 Remote subscription when the MAG implements MLD proxy
functionality
If the MAG has only MLD proxy functionality, the system behavior when
operating with remote subscription is as described in chapter 3. Once
the MLD proxy instance is configured to obtain the multicast traffic
remotely, this remains static.
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4.2 MAG as multicast router
If the MAG behaves as a multicast router, the MAG then implements a
multicast routing protocol. This allows the MAG to make decisions
about from where to receive the traffic of any multicast channel,
based in routing information and/or network management criteria. The
selected incoming interface for receiving multicast traffic will be
then the one matching such criteria, and it could drive to either a
local or remote subscription. Some situations are introduced in the
next section.
4.2.1 Local subscription when the MAG implements a multicast routing
protocol
If the MAG is a multicast router, the system behavior when operating
with local subscription is as before, but extending the role of the
MAG to be a multicast router, and running a multicast routing
protocol among the MAG and local multicast router serving the
multicast traffic. Once the MAG decides to obtain the multicast
traffic locally based in routing information and/or network
management criteria, this can be dynamically changed if such criteria
change.
4.2.2 Remote subscription when the MAG implements a multicast routing
protocol
If the MAG is a multicast router, the system behavior when operating
with remote subscription is as described in chapter 3, considering
that a multicast routing protocol is running among the MAG and the
MTMA on the tunnel interface. Once the MAG decides to obtain the
multicast traffic remotely based in routing information and/or
network management criteria, this can be dynamically changed if such
criteria change.
5 Dynamic selection of local versus remote multicast subscription
As mentioned above, the MAG as multicast router provides some
flexibility for choosing local versus remote multicast subscription.
Considering PIM as the multicast routing protocol running on the MAG,
it is possible to find out two situations where such dynamic
selection can occur, according to the PIM flavor on place. For all
the scenarios below we consider a certain multicast flow being
injected by two different sources, one local to the PMIPv6 domain and
one remote through the home network, by using an MTMA.
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5.1 Any source multicast scenario
This situation applies for both PIM-SM and BIDIR PIM variants. In
this case, once the MAG receives the MLD report from the MN
requesting the multicast channel in the form (*,G), the MAG could
decide what multicast flow subscribes to (the local or the remote
one).
The subscription can be statically pre-configured or dynamically
configured based on some rule. For instance, static configuration can
be made per MN (user), such as "multicast traffic from user X should
always go through the home (i.e., via the tunnel with the MTMA/LMA-
as-per-RFC6224), while traffic from user Y should go via local
subscription". Also, configuration profiles can also be more complex
and include considerations on types of traffic or IP flows, such as
"traffic of type A from user X should always go through the home,
traffic of type B from user X should be subscribed locally" using
routing information and/or network management criteria. Similarly,
routing information can be received dynamically, for example, at
user's registration time PBU/PBA signaling can be used to carry the
profile information similar to what is described in [I-D.gundavelli-
netext-pmipv6-sipto-option]. Also, routing information can be
exchanged dynamically when the multicast group subscription is made.
When focusing on PIM-SM, another scenario is possible. PIM-SM allows
for switching from a multicast shared-tree to a source-specific tree
to optimize the path for traffic delivery. The location of the
rendezvous point and the multicast source can be either in the PMIPv6
domain or the home network, so the optimization could be from local
subscription to remote subscription or vice versa. The possibility of
switching to a source-based tree, and the time for doing is
implementation-dependent, and it could be triggered immediately
(after reception of the first multicast packet) or last to some time,
or even not switching never.
5.2 Source specific multicast scenario
This situation applies for PIM-SSM. Then, in a source-specific
multicast scenario [RFC4607], the MAG would send the PIM request to
the corresponding interface based on the multicast source address
indicated on the (S,G) subscription requested by the MN in the MLD
Report, using the routing information.
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6 Security Considerations
This draft discusses the operations of existing protocols without
modifications. It does not introduce new security threats beyond the
current security considerations of PMIPv6 [RFC5213], MLD [RFC3810],
IGMP [RFC3376] and IGMP/MLD Proxying [RFC4605].
7 IANA Considerations
This document makes no request of IANA.
8 Contributors
The following people have considerably contributed to this draft:
Akbar Rahman
InterDigital Communications, LLC
Email: Akbar.Rahman@InterDigital.com
Ignacio Soto
Universidad Politecnica de Madrid
Email: isoto@dit.upm.es
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.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury,
K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August
2008.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in Ipv6", RFC 3775, June 2004.
[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.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
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"Internet Group Management Protocol (IGMP)/ Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, August 2006.
[RFC5847] Devarapalli, V., Koodli, R., Lim, H., Kant, N., Krishnan,
S., Laganier, J., "Heartbeat Mechanism for Proxy Mobile
IPv6", RFC 5847, June 2010.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4607] Holbrook, H., and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
9.2 Informative References
[RFC6224] Schmidt, T.C., Waehlisch, M., and S.Krishnan, "Base
Deployment for Multicast Listener Support in PMIPv6
Domains", RFC 6224, April 2011.
[ERCIM] L.M. Contreras, C.J. Bernardos, I. Soto, "On the
efficiency of a dedicated LMA for multicast traffic
distribution in PMIPv6 domains", 5th ERCIM Workshop in
eMobility, Vilanova i la Geltru, Spain, June 2011.
[I-D.deng-multimob-pmip6-requirement] H. Deng, T. Schmidt, P. Seite,
and P. Yang, "Multicast Support Requirements for Proxy
Mobile IPv6", draft-deng-multimob-pmip6-requirement-
02.txt (work in progress), July 2009.
[I-D.gundavelli-netext-pmipv6-sipto-option] S. Gundavelli, X. Zhou,
J. Korhonen, G. Feige, R. Koodli, "IP Traffic Offload
Selector Option for Proxy Mobile IPv6", draft-gundavelli-
netext-pmipv6-sipto-option-01.txt (work in progress),
July 2011.
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Author's Addresses
Juan Carlos Zuniga
InterDigital Communications, LLC
EMail: JuanCarlos.Zuniga@InterDigital.com
Luis M. Contreras
Telefonica I+D
EMail: lmcm@tid.es
Carlos J. Bernardos
Universidad Carlos III de Madrid
EMail: cjbc@it.uc3m.es
Seil Jeon
Soongsil University
Email: sijeon@dcn.ssu.ac.kr
Younghan Kim
Soongsil University
Email: yhkim@dcn.ssu.ac.kr
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