MULTIMOB Working Group JC. Zuniga
Internet-Draft InterDigital
Intended status: Informational LM. Contreras
Expires: September 5, 2012 Telefonica I+D
CJ. Bernardos
UC3M
S. Jeon
Instituto de Telecomunicacoes
Y. Kim
Soongsil University
March 4, 2012
Multicast Mobility Routing Optimizations for Proxy Mobile IPv6
draft-ietf-multimob-pmipv6-ropt-00
Abstract
The MULTIMOB group has specified a base solution to support IP
multicasting in a PMIPv6 domain [RFC6224]. In this document, some
enhancements to the base solution are described. 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 in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 5, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Multicast Tree Mobility Anchor (MTMA) . . . . . . . . . . . . 6
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Operations of the Mobile Node . . . . . . . . . . . . . . 7
3.3. Operations of the Mobile Access Gateway . . . . . . . . . 8
3.3.1. MAG as MLD Proxy . . . . . . . . . . . . . . . . . . . 8
3.3.2. MAG as Multicast Router . . . . . . . . . . . . . . . 11
3.4. Operations of the Multicast Tree Mobility Anchor . . . . . 12
4. Direct Routing . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Operations of the Mobile Node . . . . . . . . . . . . . . 13
4.3. Operations of the Mobile Access Gateway . . . . . . . . . 13
4.3.1. MAG as MLD Proxy . . . . . . . . . . . . . . . . . . . 14
4.3.2. MAG as multicast router . . . . . . . . . . . . . . . 17
5. Functions and Requirements . . . . . . . . . . . . . . . . . . 17
5.1. Extension to the Binding Update List in MAG . . . . . . . 17
5.2. Extension of the Policy Profile Information including
multicast related parameters . . . . . . . . . . . . . . . 17
5.3. Data Structure in MTMA . . . . . . . . . . . . . . . . . . 18
6. Dynamic Selection Support . . . . . . . . . . . . . . . . . . 18
6.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 18
6.2. Any Source Multicast Scenario . . . . . . . . . . . . . . 19
6.3. Source Specific Multicast Scenario . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
9. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . . 21
10.2. 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
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28
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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. 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 (MLDv2)
[RFC3810] is used in a similar way by IPv6 routers to discover the
presence of IPv6 multicast hosts. Also, the IGMP/MLD proxy [RFC4065]
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 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 multiple
PMIPv6 tunnels with different LMAs, e.g. up to one per MN. 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 leads to redundant traffic at a MAG. This is the so-
called "Tunnel Convergence problem".
To address this issue, a comprehensive solution is proposed in this
document, consisting of two complementary enhancements: multicast
anchor and direct routing. The former uses a multicast tree mobility
anchor (MTMA) as the topological anchor point for remotely delivering
multicast traffic, while the latter uses direct routing taking
advantage of local multicast source availability, allowing a MAG to
connect directly to a multicast router for simple access to local
content. Neither of the schemes has any impact on the MN to support
multicast listener mobility.
The MTMA details are described in section 3. Section 4 describes the
direct routing technique. Section 5 describes the details about the
dynamic selection at the MAG between direct routing (e.g. for local
access) and MTMA (e.g. for remote access).
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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 [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 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. This service allows MN
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.
From the definitions above, it can 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.
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.
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3. Multicast Tree Mobility Anchor (MTMA)
An MTMA can be used to serve as the mobility anchor for multicast
traffic. Typically, the MTMA will be used to get access to multicast
content remotely.
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 as described in
[RFC5213].
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
different deployment scenarios are presented in Appendix A.
3.1. Overview
Figure 1 shows an example of a PMIPv6 domain supporting multicast
mobility. The LMA is dedicated to unicast traffic, and the MTMA is
dedicated to multicast traffic. The MTMA 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 in a given PMIPv6 domain (not shown in
Figure 1 for simplicity). Similarly, more than one MTMA could be
deployed by the operator (not shown in Figure 1).
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.
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+--------------+
|Content Source|
+--------------+
|
|
*** *** *** *** *** *** *** ***
* ** ** ** * * ** ** ** *
* * * *
* 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)
3.2. Operations of the Mobile Node
The MN operation is not impacted by the existence of an MTMA as
anchor for the multicast traffic being subscribed. The MN will act
according to the stated operations in [RFC5213] and [RFC6224].
This draft considers that every MN requesting multicast-only services
is previously registered in a PMIPv6 unicast domain to get a unicast
IP address. The registration can also be required also for several
purposes such as remote management, billing, etc.
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3.3. Operations of the Mobile Access Gateway
There are two main functionalities in the MAG when it is connected to
an MTMA. One when the MAG incorporates MLD proxy functions as per
[RFC4605]. The other case is when the MAG functions as a multicast
router as per [RFC4601] or [RFC4607].
The following sections describe the MAG for both cases in more
detail.
3.3.1. MAG as MLD Proxy
If the MAG has MLD proxy functionality only, once the MLD proxy
instance is configured to obtain the multicast traffic remotely from
the MTMA, the system behavior remains static.
In case of remote subscription, all MAGs that are connected to the
MTMA must support the MLD proxy [RFC4605] function. Specifically in
Figure 1, each of the MAG1-MTMA and MAG2-MTMA tunnel interfaces
define an MLD proxy domain. The MNs 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 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.
3.3.1.1. Multicast Establishment
Figure 2 shows the procedure when MN1 attaches to MAG, and
establishes associations with LMA (unicast) and MTMA (multicast).
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MN1 MAG 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 2: MN Attachment and Multicast Service Establishment for MTMA
In Figure 2, 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. The MAG, acting as a 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 which the MAG had not
previously subscribed to). Multicast traffic will then flow from the
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MTMA towards MN1.
3.3.1.2. Multicast Mobility
Figure 3 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
does not show any unicast traffic. Of course, if it was desired to
support unicast traffic, it would be served by a tunnel between MAG2
and LMA.
According to the 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
for a new multicast group (from MAG2's point of view), this will then
result in an Aggregated MLD Report being sent to the MTMA from MAG2.
This message will be sent through a multicast tunnel between MAG2 and
MTMA (pre-established or dynamically established) .
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 MLD proxy) 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 | | | |
| | | | |
|---------Rtr Sol------ >| | |
| | |--- PBU -- >| |
| | | | |
| | |<-- PBA ----| |
| | | | |
|<-----Rtr Adv --------- | | |
| | | | |
| | |==Multicast Tunnel === |
| | | | |
|<---------MLD Query---- | | |
| | | | |
|---MLD Report (G) ----> | | |
| | | | |
| | |---- Aggregated -----> |
| | | MLD Report (G) |
| | | | |
| | | | |
|< --------- Multicast Traffic ---------------- >|
| | | | |
| | | | |
Figure 3: Multicast Mobility Signaling for MTMA
3.3.2. MAG as Multicast Router
If the MAG is a multicast router, the system behavior when operating
with remote subscription is as described before, considering that a
multicast routing protocol is running between the MAG and the MTMA on
the tunnel interface. Even once the MAG has decided to obtain the
multicast traffic remotely based for instance on routing information
and/or network management criteria, this decision can be dynamically
changed if such criteria changes. This behavior is further described
in section Section 6.2.
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3.4. Operations of the Multicast Tree Mobility Anchor
The MTMA provides connectivity to the multicast infrastructure out of
the PMIPv6 domain. The MTMA itself could either act as an additional
MLD proxy (only in the case where all the connected MAGs act also as
MLD proxies), reporting to a further node an aggregated view of the
subscriptions in a PMIPv6 multicast domain; or it can act as a
designated multicast router for all the MAGs in a PMIPv6 multicast
domain. The MTMA will then request the multicast content on behalf
of the MAGs (and MNs 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.
4. Direct Routing
Direct routing uses native multicast infrastructure, allowing a MAG
to directly connect a multicast router in the PMIPv6 domain. A MAG
can act as a MLD proxy or multicast router for redirecting multicast
packets.
The main purpose of direct routing is to provide optimal routing for
local content. As a consequence, it alleviates the MTMA of the
channel management and data delivery of locally available content.
Unicast traffic will go normally to the LMAs in the PMIPv6 domain.
This section describes how the direct routing works in scenarios of
MN attachment and multicast mobility.
4.1. Overview
Figure 4 shows the architecture for the local routing case using
native multicasting infrastructure
[I-D.deng-multimob-pmip6-requirement].
The LMA 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) in a given PMIPv6 domain.
As shown in Figure 4, a MAG may connect to both unicast (LMA) and
multicast (MR) nodes. Thus, a given MN may simultaneously receive
both unicast and multicast traffic.
As seen in Figure 4, each MAG has a direct connection (i.e., not
using the tunnel interface) with a multicast router. To facilitate
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IGMP/MLD signaling and multicast packets forwarding, a MLD proxy
function defined in [RFC4605], or multicast routing function SHOULD
be placed on the MAG.
Multicast Tree
:
: || - PMIPv6 Tunnel
+----------+ +----------+ | - Multicast Data Path
| LMA | | MR |
+----------+ +----------+
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ / |
|| \\ |
|| /\\ |
|| / \\ |
|| / \\ |
|| / \\ |
|| / \\ |
+----------+ +----------+
| P-MAG | | N-MAG | MLD Proxy or Multicast Router
+----------+ +----------+
: :
+------+ +------+
| MN | -----> | MN |
+------+ +------+
Figure 4: Architecture for direct routing based PMIPv6 multicasting
4.2. Operations of the Mobile Node
The MN operation is not impacted by the direct routing option. The
MN will act according to the stated operations in [RFC5213] and
[RFC6224].
This draft considers that every MN requesting multicast-only services
is previously registered in a PMIPv6 unicast domain to get a unicast
IP address. This registration can also be required for several
purposes such as remote management, billing, etc.
4.3. Operations of the Mobile Access Gateway
There are two main functionalities in the MAG when it supports direct
routing. One is the when the MAG incorporates MLD proxy functions as
per [RFC4605]. The other case is when the MAG functions as a
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multicast router as per [RFC4601] or [RFC4607].
The following sections describe the MAG for both cases in more
detail.
4.3.1. MAG as MLD Proxy
In case 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 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).
4.3.1.1. Multicast Establishment
If the MAG has MLD proxy functionality only, once the MLD proxy
instance is configured to obtain the multicast traffic locally, the
system behavior remains static.
In Figure 5, 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 the MN. 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).
Upon detecting node attachment from an incoming interface, the MAG
adds each downstream interface to the MLD Proxy instance with
upstream link to a MR according to the standard MLD proxy operations
and sends an MLD Query message towards the MN. The MN sends the MLD
report message (when required by its upper layer applications) as
defined in [RFC3810] in response to an MLD Query from 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 which the MAG had not previously
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subscribed to). Multicast traffic will then flow from the local
multicast router towards the MN.
MN MAG LMA MR
| (MLD Proxy) (Unicast) (Multicast)
MN attaches to MAG1 | | |
| | | |
|------Rtr Sol----- ->| | |
| |---- PBU --->| |
| | | |
| |<--- PBA ----| |
| | | |
| |== Unicast ==| |
| | Tunnel | |
|<---- Rtr Adv -------| | |
| | | |
|<------- Unicast Traffic --------->| |
| | | |
| | | |
|<--- MLD Query ------|<------ MLD Query ---------|
| | | |
MN requires | | |
multicast services | | |
| | | |
|-- MLD Report (G) -->| | |
| | | |
| |------- Aggregated ------->|
| | MLD Report (G) |
| | | |
| | | |
|<------------ Multicast Traffic ---------------->|
| | | |
Figure 5: Multicast service establishment for direct routing
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4.3.1.2. Multicast mobility
MN P-MAG N-MAG LMA MR
| | | | |
| | | | |
|<------------|<-- Multicast Data----------------|
| | . | | |
| | . | | |
| | . | | |
Link Handover | | |
Disconnected Detection | | |
| | | | |
| | | | |
| | MN Attachment | |
| | | | |
| | | | |
|------- Rtr. Sol. ------>| | |
| | | | |
|<------ MLD Query -------| | |
| | | | |
|------- MLD Report ----->| | |
| | | Aggregated |
| | |---- MLD Report ----->|
| | | | |
| | | | |
|<------------------------|<-- Multicast Data ---|
| | | | |
| | | | |
| | |--- PBU -->| |
| | | | |
| | |<-- PBA ---| |
| | | | |
Figure 6: Multicast mobility signaling for direct routing
Figure 6 shows the handover operation procedure in the local direct
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
attached MN and performs binding update procedure by exchanging PBU/
PBA signaling messages with LMA. At the same time, a MLD Proxy
instance detecting the new MN 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 upstream
link associated with the MR. In the direct routing case, an upstream
interface of MLD Proxy instance is decided towards certain multicast
router based on the operator's configuration or multicast routing, as
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compared to the base solution defined in [RFC6224] where it is
determined for each MN based on the Proxy Binding Update List. 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.
4.3.2. 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 on 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.
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.
5. Functions and Requirements
A set of new functions and structures are needed in PMIPv6 to allow
the use of the solution described in this document. The following
sub-sections describe these required extensions.
5.1. Extension to the Binding Update List in MAG
The Binding Update List in the MAG must be updated to be able to
handle the fact that more than one entity (i.e. LMA and MTMA) may be
serving the mobile node.
5.2. Extension of the Policy Profile Information including multicast
related 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, for the
remote subscription case.
Additionally, when the MAG act as multicast router in the local
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subscription case it is required to keep registration of the IP
address for the rendez-vous point in the PMIPv6 domain, when PIM-SM
is used. When using PIM-SSM, the IP addresses of the local multicast
sources have to be also registered.
5.3. Data Structure in 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 (e.g. similar to what it 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.
6. Dynamic Selection Support
As mentioned above, the MAG as multicast router provides some
flexibility for choosing local versus remote multicast subscription.
With this approach IP multicast traffic can selectively be received
from the home, visited or local domains, and the selection of traffic
can be based on operator policies. 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.
6.1. Use Cases
The MAG has different options to subscribe to a multicast group, such
as:
- Via the tunnel with the LMA unicast [RFC6224]
- Via the tunnel with the MTMA (as described in Section 3)
- Via local subscription/routing (as described in Section 4)
Also, the content can be located in different places. For instance,
the content might be locally available (e.g. TV channels offered in
the visited domain), or the content might be remote (e.g. TV
channels offered in the home domain). In case the content is
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available remotely at the home network it is preferred to subscribe
via the MTMA tunnel to home. However, if the content is available
locally, it is preferred to subscribe at the MAG (local break point)
instead of via the home network. The MAG may therefore have to
choose which approach needs to be taken to subscribe to a particular
content requested by a particular MN.
- If the IP address of the source injecting a certain multicast
group is local (scope: local domain), the MAG should get access to
it via local subscription (or routing, if the MAG is a multicast
router).
- If IP address of the source injecting a certain multicast group
is global (or the scope is broader than the local domain), the MAG
may have to decide among the different available options (i.e.
RFC6224, Local Routing, or MTMA). This can be achieved through
some static or dynamic configuration at the MAG.
6.2. 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 (either 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.ietf-netext-pmipv6-sipto-option]. Also, routing information can
be exchanged dynamically when the multicast group subscription is
made.
In case of using PIM-SM, another scenario is possible. PIM-SM allows
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 either be in the PMIPv6
domain or the home network, so the optimization could be from local
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subscription to remote subscription or vice versa. The possibility
of switching to a source-based tree, and the time for doing so is
implementation-dependent, and this could be triggered immediately
(e.g. after reception of the first multicast packet) or after some
time, or may not even switch at all.
6.3. 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.
7. IANA Considerations
TBD.
8. 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].
9. Authors
Additional co-authors of this document are:
Akbar Rahman
InterDigital Communications, LLC
E-mail: akbar.rahman@interdigital.com
Ignacio Soto
Universidad Politecnica de Madrid
E-mail: isoto@dit.upm.es
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC4065] Kempf, J., "Instructions for Seamoby and Experimental
Mobility Protocol IANA Allocations", RFC 4065, July 2005.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[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.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[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.
10.2. Informative References
[I-D.deng-multimob-pmip6-requirement]
Deng, H., Chen, G., Schmidt, T., Seite, P., and P. Yang,
"Multicast Support Requirements for Proxy Mobile IPv6",
draft-deng-multimob-pmip6-requirement-02 (work in
progress), July 2009.
[I-D.ietf-netext-pmipv6-sipto-option]
Gundavelli, G., Zhou, X., Korhonen, J., and R. Koodli,
"IPv4 Traffic Offload Selector Option for Proxy Mobile
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IPv6", draft-ietf-netext-pmipv6-sipto-option-04 (work in
progress), February 2012.
[RFC6224] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
Deployment for Multicast Listener Support in Proxy Mobile
IPv6 (PMIPv6) Domains", RFC 6224, April 2011.
Appendix A. MTMA Deployment Use Cases
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:
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.
A.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.
A.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
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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 7 shows the scenario here described.
+----------------+ +----------------+
|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 7: PMIPv6 domain with ratio N:1
The Figure 7 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
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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,
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.
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 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 8 shows the scenario here described.
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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 8: PMIPv6 domain with ratio 1:N
The Figure 8 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
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corresponding LMA and MTMA is permanently maintained.
A.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 9
adapts the PMIPv6 domain with ratio N:1 scenario of figure 7 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 MN30, MN40 and MN41.
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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 9: 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.
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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.
Authors' Addresses
Juan Carlos Zuniga
InterDigital Communications, LLC
1000 Sherbrooke Street West, 10th floor
Montreal, Quebec H3A 3G4
Canada
Email: JuanCarlos.Zuniga@InterDigital.com
URI: http://www.InterDigital.com/
Luis M. Contreras
Telefonica I+D
Don Ramon de la Cruz, 82-84
Madrid 28006
Spain
Email: lmcm@tid.es
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
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Seil Jeon
Instituto de Telecomunicacoes
Campus Universitario de Santiago
Aveiro 3810-193
Portugal
Email: seiljeon@av.it.pt
URI: https://atnog.av.it.pt/~sjeon/
Younghan Kim
Soongsil University
Sangdo-dong, Dongjak-gu
Seoul 511
Republic of Korea
Email: yhkim@dcn.ssu.ac.kr
URI: http://dcnlab.ssu.ac.kr/
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