MULTIMOB Group J.C. Zuniga
INTERNET-DRAFT A. Rahman
Intended Status: Standards Track InterDigital Communications, LLC
Expires: September 2011 L.M. Contreras
C.J. Bernardos
Universidad Carlos III de Madrid
I. Soto
Universidad Politecnica de Madrid
March 14, 2011
Support Multicast Services Using Proxy Mobile IPv6
draft-zuniga-multimob-smspmip-05.txt
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Abstract
The MULTIMOB group has specified a base solution to support IP
multicasting in a PMIPv6 domain [I-D.draft-ietf-multimob-pmipv6-base-
solution]. In this document, an enhancement is proposed to the base
solution to use a dedicated multicast LMA as the topological anchor
point for multicast traffic, while the MAG remains as an IGMP/MLD
proxy. This enhancement provides benefits such as reducing multicast
traffic replication and supporting different PMIPv6 deployments
scenarios.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Conventions and Terminology . . . . . . . . . . . . . . . . . . 3
3 Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 6
3.2.1 PMIPv6 domain with ratio 1:1 . . . . . . . . . . . . . 7
3.2.2 PMIPv6 domain with ratio N:1 . . . . . . . . . . . . . 7
3.2.3 PMIPv6 domain with ratio 1:N . . . . . . . . . . . . . 9
3.2.4 PMIPv6 domain with H-LMA . . . . . . . . . . . . . . 11
3.3 Multicast Establishment . . . . . . . . . . . . . . . . . 13
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 M-LMA attach requirements . . . . . . . . . . 17
3.5.4. Data structure stored by M-LMA . . . . . . . . . . . 17
3.6 Advantages . . . . . . . . . . . . . . . . . . . . . . . 17
4 Security Considerations . . . . . . . . . . . . . . . . . . . 21
5 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.1 Normative References . . . . . . . . . . . . . . . . . . 21
6.2 Informative References . . . . . . . . . . . . . . . . . 21
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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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 [I-D.draft-ietf-
multimob-pmipv6-base-solution]. In this document, an enhancement is
proposed to the base solution to use a dedicated multicast LMA (M-
LMA) as the topological anchor point for multicast traffic, while the
MAG remains as an IGMP/MLD proxy. This enhancement allows different
PMIPv6 deployment scenarios. It also eliminates the so called
"Tunnel Convergence problem" where the MAG may receive the same
multicast packet from several LMAs. There are no impacts to the MN to
support multicast listener mobility from this document.
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].
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
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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 LMA 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 associated to that LMA regarding its
multicast traffic.
This means that a PMIPv6 domain can have several PMIPv6 unicast
domains and PMIPv6 multicast domains.
Additionally, some other definitions are introduced, as follows.
- U-LMA or Unicast-LMA: LMA entity dedicated to unicast service
exclusively.
- M-LMA or Multicast-LMA: LMA entity dedicated to multicast
service exclusively.
- H-LMA or Hybrid-LMA: LMA entity dedicated to both unicast and
multicast services.
3 Solution
A PMIPv6 domain may handle data from both unicast and multicast
sources. A dedicated multicast LMA can be used to serve as the
mobility anchor for multicast traffic. Unicast traffic will go
normally to the other LMAs in the PMIPv6 domain. This section
describes how the multicast LMA works in scenarios of MN attachment
and multicast mobility. We first concentrate on the case of both LMAs
(multicast and unicast) 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 LMA2 is dedicated
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to multicast traffic. The multicast traffic LMA (LMA2) 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 multicast dedicated LMA
can be deployed by the operator (not shown in Figure 1).
Also in this architecture, all MAGs that are connected to the
multicast LMA must support the MLD proxy [RFC4605] function.
Specifically in Figure 1, each of the MAG1-LMA2 and MAG2-LMA2 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 LMA2
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 and multicast
LMAs. 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 such as remote management, billing, etc.
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+--------------+
|Content Source|
+--------------+
|
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* Unicast Traffic * * Multicast Traffic *
* * * *
* ** ** ** * * ** ** ** *
*** *** *** *** *** *** *** ***
| |
| |
| |
+-----+ +------+
Unicast | LMA1| | LMA2 | Multicast
Anchor +-----+ +------+ Anchor
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
\\ // ||
+-----+ +-----+
| MAG1| | MAG2| MLD Proxy
+-----+ +-----+
| | |
| | |
{MN1} {MN2} {MN3}
Figure 1. Architecture of Dedicated LMA as Multicast Anchor
3.2 Deployment Scenarios
From the network architecture point of view, there are several
options when considering the dedicated multicast LMA (M-LMA)
approach. These options can be distinguished in terms of the number
of unicast and multicast LMAs present in a PMIPv6 domain and the
service relationship that a set of MNs gets from them, in the form of
a "U-LMA : M-LMA" ratio. According to that, it is possible to
differentiate the following approaches:
- A set of MNs is served in a PMIPv6 domain by two LMAs, one for
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multicast service, the other one 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 LMAs, one
for multicast service, while the rest 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 LMAs, one
for unicast, while the rest 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 LMAs, one for unicast and the other one for multicast. All
the MNs of the set are served by these two LMAs 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 LMA 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 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 | | LMA2 | | LMA3 |
|(U-LMA)| | (M-LMA) | |(U-LMA)|
+-------+ +-----------------+ +-------+
|| \\ 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 LMAs, LMA1
and LMA3, acting as U-LMAs, while there is another one, the LMA2,
working as dedicated M-LMA. LMA1 and LMA3 constitute two distinct
unicast domains, whereas LMA2 forms a single multicast domain. The
tunnels among MAGs and LMAs represented by lines ("||") indicate a
tunnel transporting unicast traffic, while the tunnels depicted with
circles ("o") show a tunnel transporting multicast traffic.
In the figure it can be observed that all the MNs are served by LMA2
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 U-LMA and M-LMA 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 LMAs
for multicast service as they move in the PMIPv6 domain. Each
particular MN association with the LMAs (unicast and multicast)
remains always the same as it moves in the PMIPv6 domain.
Figure 3 shows the scenario here described.
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+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| |
*** *** *** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** *** *** *** ***
| | |
| | |
| | |
+-------+ +-----------------+ +-------+
| LMA1 | | LMA2 | | LMA3 |
|(M-LMA)| | (U-LMA) | |(M-LMA)|
+-------+ +-----------------+ +-------+
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
The figure 3 proposes an architecture where the LMA2 is the unique U-
LMA for a certain group of MNs, while there are two others LMAs, LMA1
and LMA3, act as M-LMAs for different subsets of MNs of the same
group. LMA1 and LMA3 constitute two distinct multicast domains,
whereas LMA2 forms a single unicast domain. Each M-LMA could be
devoted to carry on a different content (for instance, LMA1 for
source A and LMA3 for source B) or not. Looking at the picture, the
subset formed by MN10, MN11, MN20 and MN21 is served by LMA1 for
multicast. The rest of MNs are being served by LMA3 also for
multicast. Finally, all of them are served by LMA2 for unicast. For
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the scenario described above, the association between each MN and the
corresponding U-LMA and M-LMA is permanently maintained.
3.2.4 PMIPv6 domain with H-LMA
The H-LMA is defined as an LMA which simultaneously transports
unicast and multicast service. In the context of the dedicated M-LMA
solution, an H-LMA can play the role of M-LMA for an entire group of
MNs in a PMIPv6 domain, while acting simultaneously as U-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 LMA2 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 MN30,
MN40 and MN41.
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+----------------+ +----------------+
|Content Source A| |Content Source B|
+----------------+ +----------------+
| |
| |
*** *** *** *** *** *** *** *** *** *** ***
* ** ** ** ** ** ** ** ** ** ** *
* *
* Fixed Internet *
* (Unicast & Multicast Traffic) *
* ** ** ** ** ** ** ** ** ** ** *
*** *** *** *** *** *** *** *** *** *** ***
| | |
| | |
| | |
+-------+ +-----------------+ +-------+
| LMA1 | | LMA2 | | LMA3 |
|(U-LMA)| | (H-LMA) | |(U-LMA)|
+-------+ +-----------------+ +-------+
|| \\ 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
Figure 4 presents a PMIPv6 network where there are two pure unicast
LMAs, LMA1 and LMA3, and a hybrid LMA, the LMA2. The LMA2 is a
dedicated M-LMA 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 LMA2
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(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 LMA2. 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 U-LMA and M-LMA is permanently maintained.
3.3 Multicast Establishment
Figure 5 shows the procedure when MN1 attaches to MAG1, and
establishes associations with LMA1 (unicast) and LMA2 (multicast).
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MN1 MAG1 LMA1 LMA2
| (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 LMA1 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 LMA1.
For multicast traffic, a multicast tunnel may have been pre-
configured between MAG1 and the multicast LMA (LMA2). Or the
multicast tunnel 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 MAG1. MAG1 acting as a MLD Proxy as defined in [RFC4605] will
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then send an Aggregated MLD Report to the multicast anchor, LMA2
(assuming that this is a new multicast group which MAG1 had not
previously subscribed to). Multicast traffic will then flow from
LMA2 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 LMA2 (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 LMA1 to transfer unicast traffic.
According to baseline solution signaling method described in [I-
D.draft-ietf-multimob-pmipv6-base-solution], 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 LMA2 from MAG2. This message will be sent through a
pre-established (or dynamically established) multicast tunnel between
MAG2 and LMA2.
When MN2 detaches, MAG1 may keep the multicast tunnel with the
multicast LMA2 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 LMA1 LMA2
| (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 M-LMA 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 LMA (i.e. U-LMA and M-LMA) 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 U-LMA and M-LMA.
3.5.3 MAG to M-LMA attach requirements
The MAG procedures must be updated to be able to handle simultaneous
attach for a given mobile node to both the U-LMA and M-LMA. For
example, packets coming from a given mobile node must be screened to
determine if it should be sent to the U-LMA or to the M-LMA.
3.5.4. Data structure stored by M-LMA
The M-LMA does not directly interact with the MNs attached to any of
the MAGs. The M-LMA 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 M-LMA should be the tunnel
interface identifier (tunnel-if-id) of the bi-directional tunnel for
multicast between the M-LMA 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 M-LMA.
3.6 Advantages
An advantage of the proposed dedicated multicast LMA (M-LMA)
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 [I-D.draft-ietf-multimob-pmipv6-
base-solution] 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 LMAs, 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
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operator for expected traffic distributions.
A final advantage is that a dedicated multicast LMA minimizes
replication of multicast packets (the Tunnel Convergence problem), in
certain scenarios, compared to [I-D.draft-ietf-multimob-pmipv6-base-
solution]. Figures 7 and 8 illustrate this point visually. For this
simple scenario, it can be observed that the dedicated multicast LMA
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 dedicated multicast 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-LMA2 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.)
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+--------------+
|Content Source|
+--------------+
|
|
+---+ Packet destined
| 1 | for Multicast group "G"
+---+
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* Unicast Traffic * * Multicast Traffic *
* * * *
* ** ** ** * * ** ** ** *
*** *** *** *** *** *** *** ***
| |
| +---+
| | 2 |
| +---+
| |
+-----+ +------+
Unicast | LMA1| | LMA2 | 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 a Dedicated Multicast LMA
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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 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].
5 IANA Considerations
This document makes no request of IANA.
6 References
6.1 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,
"Internet Group Management Protocol (IGMP)/ Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, August 2006.
6.2 Informative References
[I-D.draft-ietf-multimob-pmipv6-base-solution] Schmidt, T.C.,
Waehlisch, M., and S.Krishnan, "Base Deployment for
Multicast Listener Support in PMIPv6 Domains", draft-
ietf-multimob-pmipv6-base-solution-07 (Work in progress),
December 29, 2010.
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Author's Addresses
Juan Carlos Zuniga
InterDigital Communications, LLC
Email: JuanCarlos.Zuniga@InterDigital.com
Akbar Rahman
InterDigital Communications, LLC
Email: Akbar.Rahman@InterDigital.com
Luis M. Contreras
Universidad Carlos III de Madrid
Email: contreras.uc3m@gmail.com
Carlos J. Bernardos
Universidad Carlos III de Madrid
Email: cjbc@it.uc3m.es
Ignacio Soto
Universidad Politecnica de Madrid
Email: isoto@dit.upm.es
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