draft-ietf-mboned-v4v6-mcast-ps-01.txt   draft-ietf-mboned-v4v6-mcast-ps-02.txt 
MBONED Working Group C. Jacquenet MBONED Working Group C. Jacquenet
Internet-Draft M. Boucadair Internet-Draft M. Boucadair
Intended status: Informational France Telecom Orange Intended status: Informational France Telecom Orange
Expires: May 13, 2013 Y. Lee Expires: September 14, 2013 Y. Lee
Comcast Comcast
J. Qin J. Qin
Cisco Systems Cisco Systems
T. Tsou T. Tsou
Huawei Technologies (USA) Huawei Technologies (USA)
Q. Sun Q. Sun
China Telecom China Telecom
November 09, 2012 March 13, 2013
IPv4-IPv6 Multicast: Problem Statement and Use Cases IPv4-IPv6 Multicast: Problem Statement and Use Cases
draft-ietf-mboned-v4v6-mcast-ps-01 draft-ietf-mboned-v4v6-mcast-ps-02
Abstract Abstract
This document discusses issues and requirements raised by IPv4-IPv6 This document discusses issues and requirements raised by IPv4-IPv6
multicast interconnection and co-existence scenarios. It also multicast interconnection and co-existence scenarios. It also
discusses various multicast use cases which may occur during IPv6 discusses various multicast use cases which may occur during IPv6
transitioning. transitioning.
Requirements Language Status of This Memo
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 13, 2013. This Internet-Draft will expire on September 14, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Organization of the Document . . . . . . . . . . . . . . 4
1.3. Organization of the Document . . . . . . . . . . . . . . . 5 2. Scope and Service Requirements . . . . . . . . . . . . . . . 5
2. Scope and Service Requirements . . . . . . . . . . . . . . . . 5 2.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Service Requirements . . . . . . . . . . . . . . . . . . 5
2.2. Service Requirements . . . . . . . . . . . . . . . . . . . 6 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. IPv4 Receiver and Source Connected to an IPv6-Only 3.1. IPv4 Receiver and Source Connected to an IPv6-Only
Network . . . . . . . . . . . . . . . . . . . . . . . . . 7 Network . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. IPv6 Receiver and Source Connected to an IPv4-Only 3.2. IPv6 Receiver and Source Connected to an IPv4-Only
Network . . . . . . . . . . . . . . . . . . . . . . . . . 9 Network . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. IPv6 Receiver and IPv4 Source . . . . . . . . . . . . . . 11 3.3. IPv6 Receiver and IPv4 Source . . . . . . . . . . . . . . 10
3.4. IPv4 Receiver and IPv6 Source . . . . . . . . . . . . . . 13 3.4. IPv4 Receiver and IPv6 Source . . . . . . . . . . . . . . 11
3.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 13
4. Design Considerations . . . . . . . . . . . . . . . . . . . . 15 4. Design Considerations . . . . . . . . . . . . . . . . . . . . 13
4.1. Group and Source Discovery Considerations . . . . . . . . 15 4.1. Group and Source Discovery Considerations . . . . . . . . 13
4.2. Subscription . . . . . . . . . . . . . . . . . . . . . . . 16 4.2. Subscription . . . . . . . . . . . . . . . . . . . . . . 13
4.3. Multicast Tree Computation . . . . . . . . . . . . . . . . 16 4.3. Multicast Tree Computation . . . . . . . . . . . . . . . 14
4.4. Multicast Adaptation Functions (AF) . . . . . . . . . . . 17 4.4. Multicast Adaptation Functions (AF) . . . . . . . . . . . 14
4.4.1. AF For Control Flows . . . . . . . . . . . . . . . . . 17 4.4.1. AF For Control Flows . . . . . . . . . . . . . . . . 14
4.4.2. AF For Data Flows . . . . . . . . . . . . . . . . . . 18 4.4.2. AF For Data Flows . . . . . . . . . . . . . . . . . . 16
4.4.3. Address Mapping . . . . . . . . . . . . . . . . . . . 18 4.4.3. Address Mapping . . . . . . . . . . . . . . . . . . . 16
4.5. Combination of ASM and SSM Modes . . . . . . . . . . . . . 19 4.5. Combination of ASM and SSM Modes . . . . . . . . . . . . 16
5. What Is Expected From The IETF . . . . . . . . . . . . . . . . 19 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 8.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20 8.2. Informative References . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
Global IPv4 address depletion inevitably challenges service providers Global IPv4 address depletion inevitably challenges service providers
who must guarantee IPv4 service continuity during the forthcoming who must guarantee IPv4 service continuity during the forthcoming
transition period. In particular, access to IPv4 contents that are transition period. In particular, access to IPv4 contents that are
multicast to IPv4 receivers becomes an issue when the forwarding of multicast to IPv4 receivers becomes an issue when the forwarding of
multicast data assumes the use of global IPv4 addresses. multicast data assumes the use of global IPv4 addresses.
The rarefaction of global IPv4 addresses may indeed affect the The rarefaction of global IPv4 addresses may indeed affect the
skipping to change at page 4, line 21 skipping to change at page 4, line 13
therefore suffer from IPv4 address depletion. therefore suffer from IPv4 address depletion.
o The progressive introduction of IPv6 as the only perennial o The progressive introduction of IPv6 as the only perennial
solution to global IPv4 address depletion does not necessarily solution to global IPv4 address depletion does not necessarily
assume that multicast-based IPv4 services will be migrated assume that multicast-based IPv4 services will be migrated
accordingly. Access to IPv4 multicast contents when no global accordingly. Access to IPv4 multicast contents when no global
IPv4 address can be assigned to a customer raises several issues: IPv4 address can be assigned to a customer raises several issues:
(1) The completion of the IGMP-based multicast group subscription (1) The completion of the IGMP-based multicast group subscription
procedure, (2) The computation of the IPv4 multicast distribution procedure, (2) The computation of the IPv4 multicast distribution
tree, and (3) The IPv4-inferred addressing scheme to be used in a tree, and (3) The IPv4-inferred addressing scheme to be used in a
networking environment which will progressively become IPv6- networking environment which will progressively become
enabled. IPv6-enabled.
This document does not make any assumption on the techniques used for This document does not make any assumption on the techniques used for
the delivery of multicast traffic (e.g., native IP multicast with or the delivery of multicast traffic (e.g., native IP multicast with or
without traffic isolation features, etc.) without traffic isolation features, etc.)
This document elaborates on the context and discusses multicast- This document elaborates on the context and discusses multicast-
related issues and requirements. related issues and requirements.
1.1. Goals 1.1. Terminology
The objective of this document is to clarify the problem space. In
particular, this document elaborates on the following issues:
o What are the hurdles encountered for the delivery of multicast-
based service offerings when both IPv4 and IPv6 co-exist?
o What standardization effort is needed: are there any missing
function and protocol extension?
o Does the work on multicast transition have to cover both
encapsulation and translation schemes, considering the requirement
of multicast network performance among others?
1.2. Terminology
This document uses the following terms: This document uses the following terms:
o Multicast Source: Source of contents that are multicast to o Multicast Source: Source of contents that are multicast to
receivers. A video streaming server is an example of such source. receivers. A video streaming server is an example of such source.
o Multicast Receiver: Receiver, in short. A Set Top Box (STB) is an o Multicast Receiver: Receiver, in short. A Set Top Box (STB) is an
example of such receiver. example of such receiver.
o Multicast Delivery Network: Network in short, covers the realm o Multicast Delivery Network: Network in short, covers the realm
from Designated Routers that are directly connected to sources to from Designated Routers that are directly connected to sources to
IGMP/MLD (Internet Group Management Protocol/Multicast Listener IGMP/MLD (Internet Group Management Protocol/Multicast Listener
Discovery) Querier devices that process IGMP/MLD signalling Discovery) Querier devices that process IGMP/MLD signalling
traffic exchanged with receivers. traffic exchanged with receivers.
1.3. Organization of the Document 1.2. Organization of the Document
This document is organized as follows: This document is organized as follows:
o Section 2 details basic requirements that should be addressed by o Section 2 details basic requirements that should be addressed by
providers involved in the delivery of multicast-based services providers involved in the delivery of multicast-based services
during the transition period, during the transition period,
o Section 3 discusses several use cases that reflect issues raised o Section 3 discusses several use cases that reflect issues raised
by the forthcoming transition period, by the forthcoming transition period,
o Section 4 details design considerations, o Section 4 details design considerations.
o Section 5 summarizes the standardization effort that should be
tackled by the IETF.
2. Scope and Service Requirements 2. Scope and Service Requirements
2.1. Scope 2.1. Scope
Intra-domain only: The delivery of multicast services such as live Intra-domain only: The delivery of multicast services such as live
TV broadcasting often relies upon walled garden designs that TV broadcasting often relies upon walled garden designs that
restrict the scope to the domain where such services can be restrict the scope to the domain where such services can be
subscribed. As a consequence, considerations about inter-domain subscribed. As a consequence, considerations about inter-domain
multicast are out of the scope of this document. multicast are out of the scope of this document.
Multicast-enabled networks only: This document assumes that the Multicast-enabled networks only: This document assumes that the
network is *IP multicast-enabled*. That is, whatever the IP network is IP multicast-enabled. That is, whatever the IP address
address family of the content, this content will be multicast family of the content, this content will be multicast along
along distribution trees that should be terminated as close to the distribution trees that should be terminated as close to the
receivers as possible for the sake of bandwidth optimization. In receivers as possible for the sake of bandwidth optimization. In
other words, *considerations about forwarding multicast traffic other words, considerations about forwarding multicast traffic
over unicast-only (access) networks are out of the scope of this over unicast-only (access) networks are out of the scope of this
document.* document.
Multicast to the receivers, not from the receivers: This document Multicast to the receivers, not from the receivers: This document
only covers the case where multicast traffic is forwarded by the only covers the case where multicast traffic is forwarded by the
service provider network to the receivers. This document does not service provider network to the receivers. This document does not
cover the case where the receivers send multicast traffic to the cover the case where the receivers send multicast traffic to the
network. network.
2.2. Service Requirements 2.2. Service Requirements
The delivery of multicast contents during the forthcoming transition The delivery of multicast contents during the forthcoming transition
period needs to address the following requirements. Note that some period needs to address the following requirements. Note that some
of these requirements are not necessarily specific to the IPv4-to- of these requirements are not necessarily specific to the IPv4-to-
IPv6 transition context, but rather apply to a wide range of IPv6 transition context, but rather apply to a wide range of
multicast-based services whatever the environmental constraints, but multicast-based services whatever the environmental constraints, but
the forthcoming transition period further stresses these requirements the forthcoming transition period further stresses these requirements
(see Section 4.4.1 for more details). (see Section 4.4.1 for more details).
o Optimize bandwidth. Contents SHOULD NOT be multicast twice (i.e., o Optimize bandwidth. Contents should not be multicast twice (i.e.,
using both versions of IP) to optimize bandwidth usage. Injecting using both versions of IP) to optimize bandwidth usage. Injecting
multicast content using both IPv4 and IPv6 raises some multicast content using both IPv4 and IPv6 raises some
dimensioning issues that should be carefully evaluated by service dimensioning issues that should be carefully evaluated by service
providers during network planning operations. For instance, if providers during network planning operations. For instance, if
only few IPv6-enabled receivers are in use, it can be more only few IPv6-enabled receivers are in use, it can be more
convenient to convey multicast traffic over IPv4 rather than convenient to convey multicast traffic over IPv4 rather than
doubling the consumed resources for few users. IPv4/IPv6 co- doubling the consumed resources for few users. IPv4/IPv6 co-
existence solutions SHOULD be designed to optimize network existence solutions should be designed to optimize network
resource utilization. resource utilization.
o Zap rapidly. The time it takes to switch from one content to o Zap rapidly. The time it takes to switch from one content to
another MUST be as short as possible. For example, zapping times another must be as short as possible. For example, zapping times
between two TV channels should be in the magnitude of a few between two TV channels should be in the magnitude of a few
seconds at most, whatever the conditions to access the multicast seconds at most, whatever the conditions to access the multicast
network. A procedure called "IGMP fast-leave" is sometimes used network. A procedure called "IGMP fast-leave" is sometimes used
to minimize this issue so that the corresponding multicast stream to minimize this issue so that the corresponding multicast stream
is stopped as soon as the IGMP Leave message is received by the is stopped as soon as the IGMP Leave message is received by the
Querier. In current deployments, IGMP fast-leave often assumes Querier. In current deployments, IGMP fast-leave often assumes
the activation of the IGMP Proxy function in DSLAMs. The the activation of the IGMP Proxy function in DSLAMs. The
complexity of such design is aggravated within a context where complexity of such design is aggravated within a context where
IPv4 multicast control messages are encapsulated in IPv6. IPv4 multicast control messages are encapsulated in IPv6.
o Preserve the integrity of contents. Some contract agreements may o Preserve the integrity of contents. Some contract agreements may
prevent a service provider from altering the content owned by the prevent a service provider from altering the content owned by the
content provider, because of copyright, confidentiality and SLA content provider, because of copyright, confidentiality and SLA
assurance reasons. Multicast streams SHOULD be delivered without assurance reasons. Multicast streams should be delivered without
altering their content. altering their content.
o Preserve service quality. Crossing a CGN or performing multicast o Preserve service quality. Crossing a CGN or performing multicast
packet encapsulation may lead to fragmentation or extra delays and packet encapsulation may lead to fragmentation or extra delays and
may therefore impact the perceived quality of service. Such may therefore impact the perceived quality of service. Such
degradation MUST be avoided. degradation must be avoided.
o Optimize IPv4-IPv6 inter-working design. In some operational o Optimize IPv4-IPv6 inter-working design. In some operational
networks, a source-based stateful NAT function is sometimes used networks, a source-based stateful NAT function is sometimes used
for load balancing purposes, for example. Because of the for load balancing purposes, for example. Because of the
operational issues raised by such a stateful design, the operational issues raised by such a stateful design, the
deployment of stateless IPv4-IPv6 interworking functions SHOULD be deployment of stateless IPv4-IPv6 interworking functions should be
privileged. privileged.
3. Use Cases 3. Use Cases
During the IPv4-to-IPv6 transition period, there might be a mix of During the IPv4-to-IPv6 transition period, there might be a mix of
multicast receivers, sources, and networks running in different multicast receivers, sources, and networks running in different
address families. However, service providers must guarantee the address families. However, service providers must guarantee the
delivery of multicast services to IPv4 receivers and, presumably, delivery of multicast services to IPv4 receivers and, presumably,
IPv6 receivers. Because of the inevitable combination of different IPv6 receivers. Because of the inevitable combination of different
IP version-related environments (sources, receivers and networks), IP version-related environments (sources, receivers and networks),
skipping to change at page 9, line 5 skipping to change at page 7, line 49
Function AF2 is needed at the border between the IPv6 multicast Function AF2 is needed at the border between the IPv6 multicast
domain and the IPv4 multicast domain where the source resides. AF2 domain and the IPv4 multicast domain where the source resides. AF2
is typically embedded in a multicast router that either terminates or is typically embedded in a multicast router that either terminates or
propagates PIM signalling directed toward the IPv4 source in the IPv6 propagates PIM signalling directed toward the IPv4 source in the IPv6
multicast domain. multicast domain.
On the IPv4 side, AF2 also acts as a multicast router, and uses PIMv4 On the IPv4 side, AF2 also acts as a multicast router, and uses PIMv4
signalling to join the IPv4 multicast group. The return path taken signalling to join the IPv4 multicast group. The return path taken
by multicast traffic is shown in Figure 2. by multicast traffic is shown in Figure 2.
+------+ +-----+ +------+ +------+ +-----+ +------+ +-----+ +------+ +------+ +-----+
| Host | | DS | | MR | | MR | | | | Host | | DS | | MR | | MR | | |
| Rcvr |------| AF1 | | | . . . | |------| Src | | Rcvr |------| AF1 | | | . . . | |------| Src |
| | IPv4 | | | (BG) | IPv4 | (DR) | IPv4 | | | | IPv4 | | | (BG) | IPv4 | (DR) | IPv4 | |
+------+ +-----+ +------+ +------+ +-----+ +------+ +-----+ +------+ +------+ +-----+
/ \ / \
/ IPv6 \ IPv4 / IPv6 \ IPv4
/ \ / \
+------+ +----+ +------+ +------+ +----+ +------+
| MR | | | | DS | | MR | | | | DS |
| |------| MR | . . . | AF2 | | |------| MR | . . . | AF2 |
| (DR) | IPv6 | | IPv6 | (BG) | | (DR) | IPv6 | | IPv6 | (BG) |
+------+ +----+ +------+ +------+ +----+ +------+
<------------------------------------- <-------------------------------------
Rcvr: Multicast receiver Rcvr: Multicast receiver
DS : Dual Stack DS : Dual Stack
AF : Adaptation Function AF : Adaptation Function
MR : Multicast router MR : Multicast router
DR : Designated Router DR : Designated Router
BG : Border Gateway BG : Border Gateway
Src : Multicast source Src : Multicast source
Figure 2: Multicast Traffic Forwarding Path for the 4-6-4 Scenario. Figure 2: Multicast Traffic Forwarding Path for the 4-6-4 Scenario.
Again, adaptation functions are needed whenever the IP protocol Again, adaptation functions are needed whenever the IP protocol
version changes. The adaptation function instance AF2 at the version changes. The adaptation function instance AF2 at the
boundary between the source network and the IPv6 network may either boundary between the source network and the IPv6 network may either
encapsulate or translate the headers of the IPv4 packets to allow the encapsulate or translate the headers of the IPv4 packets to allow the
content to cross the IPv6 network. The adaptation function instance content to cross the IPv6 network. The adaptation function instance
at the boundary between the IPv6 network and the receiver network at the boundary between the IPv6 network and the receiver network
performs the reverse operation to deliver IPv4 packets. performs the reverse operation to deliver IPv4 packets.
Given the current state-of-the-art where multicast content is likely Given the current state-of-the-art where multicast content is likely
skipping to change at page 11, line 5 skipping to change at page 9, line 36
AF : Adaptation Function AF : Adaptation Function
MR : Multicast Router MR : Multicast Router
DR : Designated Router DR : Designated Router
BG : Border Gateway BG : Border Gateway
Figure 3: Signalling Path For the 6-4-6 Scenario. Figure 3: Signalling Path For the 6-4-6 Scenario.
Figure 4 shows the path taken by multicast traffic flowing from the Figure 4 shows the path taken by multicast traffic flowing from the
IPv6 source to the IPv6 receiver. IPv6 source to the IPv6 receiver.
+------+ +-----+ +------+ +------+ +------+ +-----+ +------+ +------+
| Host | | DS | | MR | | MR | | Host | | DS | | MR | | MR |
| Rcvr |------| AF1 | | | . . . | | | Rcvr |------| AF1 | | | . . . | |
| | IPv6 | | | (BG) | IPv6 | (DR) | | | IPv6 | | | (BG) | IPv6 | (DR) |
+------+ +-----+ +------+ +------+ +------+ +-----+ +------+ +------+
/ \ \ / \ \
/ IPv4 \ IPv6 \ IPv6 / IPv4 \ IPv6 \ IPv6
/ \ \ / \ \
+------+ +----+ +------+ +-----+ +------+ +----+ +------+ +-----+
| MR | | | | DS | | | | MR | | | | DS | | |
| |------| MR | . . . | AF2 | | Src | | |------| MR | . . . | AF2 | | Src |
| (DR) | IPv4 | | IPv4 | (BG) | | | | (DR) | IPv4 | | IPv4 | (BG) | | |
+------+ +----+ +------+ +-----+ +------+ +----+ +------+ +-----+
<------------------------------------- <-------------------------------------
Rcvr: Multicast receiver Rcvr: Multicast receiver
DS : Dual Stack DS : Dual Stack
AF : Adaptation Function AF : Adaptation Function
MR : Multicast Router MR : Multicast Router
DR : Designated Router DR : Designated Router
BG : Border Gateway BG : Border Gateway
Src : Multicast source Src : Multicast source
Figure 4: Multicast Traffic Forwarding Path For the 6-4-6 Scenario. Figure 4: Multicast Traffic Forwarding Path For the 6-4-6 Scenario.
3.3. IPv6 Receiver and IPv4 Source 3.3. IPv6 Receiver and IPv4 Source
We refer to this scenario as 6-4. An example of such use case is the We refer to this scenario as 6-4. An example of such use case is the
context of some mobile networks, where terminal devices are only context of some mobile networks, where terminal devices are only
provisioned with an IPv6 prefix. Accessing IPv4-formatted multicast provisioned with an IPv6 prefix. Accessing IPv4-formatted multicast
content from an IPv6-only receiver requires additional functions to content from an IPv6-only receiver requires additional functions to
be enabled. be enabled.
This scenario is privileged by mobile operators who deploy NAT64 This scenario is privileged by mobile operators who deploy NAT64
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Such ALG (Application Level Gateway) may also be required to help an Such ALG (Application Level Gateway) may also be required to help an
IPv6 receiver select the appropriate multicast group address when IPv6 receiver select the appropriate multicast group address when
only the IPv4 address is advertised (e.g., when the SDP (Session only the IPv4 address is advertised (e.g., when the SDP (Session
Description Protocol) protocol is used to advertise some contents); Description Protocol) protocol is used to advertise some contents);
otherwise, access to IPv4 multicast content from an IPv6 receiver may otherwise, access to IPv4 multicast content from an IPv6 receiver may
be compromised. be compromised.
ALGs may be located upstream in the network. As a consequence, these ALGs may be located upstream in the network. As a consequence, these
ALGs do not know in advance whether the receiver is dual-stack or ALGs do not know in advance whether the receiver is dual-stack or
IPv6-only. In order to avoid the use of an ALG in the path, an IPv4- IPv6-only. In order to avoid the use of an ALG in the path, an
only source can advertise both an IPv4 multicast group address and IPv4-only source can advertise both an IPv4 multicast group address
the corresponding IPv4-embedded IPv6 multicast group address and the corresponding IPv4-embedded IPv6 multicast group address
[I-D.ietf-mboned-64-multicast-address-format]. [I-D.ietf-mboned-64-multicast-address-format].
However, a dual-stack receiver may prefer to use the IPv6 address to However, a dual-stack receiver may prefer to use the IPv6 address to
receive the multicast content. The selection of the IPv6 multicast receive the multicast content. The selection of the IPv6 multicast
address would then require multicast flows to cross an IPv4-IPv6 address would then require multicast flows to cross an IPv4-IPv6
interworking function. interworking function.
The receiver should therefore be able to unambiguously distinguish an The receiver should therefore be able to unambiguously distinguish an
IPv4-embedded IPv6 multicast address from a native IPv6 multicast IPv4-embedded IPv6 multicast address from a native IPv6 multicast
address. address.
skipping to change at page 16, line 36 skipping to change at page 14, line 11
In case the underlying access network is IPv6, the information In case the underlying access network is IPv6, the information
conveyed in IGMP messages should be relayed by corresponding MLD conveyed in IGMP messages should be relayed by corresponding MLD
messages. messages.
4.3. Multicast Tree Computation 4.3. Multicast Tree Computation
Grafting to an IPv4 multicast distribution tree through an IPv6 Grafting to an IPv4 multicast distribution tree through an IPv6
multicast domain suggests that IPv4 multicast traffic will have to be multicast domain suggests that IPv4 multicast traffic will have to be
conveyed along an "IPv6-equivalent" multicast distribution tree. conveyed along an "IPv6-equivalent" multicast distribution tree.
That is, part of the multicast distribution tree along which IPv4 That is, part of the multicast distribution tree along which IPv4
multicast traffic will be forwarded SHOULD be computed and maintained multicast traffic will be forwarded should be computed and maintained
by means of the PIMv6 machinery, so that the distribution tree can be by means of the PIMv6 machinery, so that the distribution tree can be
terminated as close to the IPv4 receivers as possible for the sake of terminated as close to the IPv4 receivers as possible for the sake of
the multicast forwarding efficiency. This assumes a close the multicast forwarding efficiency.
interaction between the PIM designs enforced in both IPv4 and IPv6
multicast domains, by means of specific Inter-Working Functions that This assumes a close interaction between the PIM designs enforced in
are further discussed in Section 4.4. both IPv4 and IPv6 multicast domains, by means of specific Inter-
Working Functions that are further discussed in Section 4.4.
Such interaction may be complicated by different combinations: the Such interaction may be complicated by different combinations: the
IPv4 multicast domain is SSM-enabled (with no RP (Rendezvous Point) IPv4 multicast domain is SSM-enabled (with no RP (Rendezvous Point)
routers), while the IPv6 multicast domain may support both ASM (Any routers), while the IPv6 multicast domain may support both ASM (Any
Source Multicast) and SSM (Source Specific Multicast) [RFC3569] Source Multicast) and SSM (Source Specific Multicast) [RFC3569]
modes. modes.
4.4. Multicast Adaptation Functions (AF) 4.4. Multicast Adaptation Functions (AF)
IPv4-IPv6 multicast interworking functions are required for both IPv4-IPv6 multicast interworking functions are required for both
translation (one address family to another) and traversal (one translation (one address family to another) and traversal (one
address family over another) contexts. address family over another) contexts.
Given the multiple versions of Group Membership management protocols, Given the multiple versions of Group Membership management protocols,
issues may be raised when, for example, IGMPv2 is running in the IPv4 issues may be raised when, for example, IGMPv2 is running in the IPv4
multicast domain that is connected to the IPv6 multicast domain by multicast domain that is connected to the IPv6 multicast domain by
means of an IWF, while MLDv2 is running in the IPv6 multicast domain. means of an IWF, while MLDv2 is running in the IPv6 multicast domain.
To solve these problems, the design of the IWF function SHOULD adhere To solve these problems, the design of the IWF function should adhere
to the IP version-independent, protocol interaction approach to the IP version-independent, protocol interaction approach
documented in Section 8 of [RFC3810] and Section 7 of [RFC3376]. documented in Section 8 of [RFC3810] and Section 7 of [RFC3376].
Note that, for traversal cases, to improve the efficiency of the Note that, for traversal cases, to improve the efficiency of the
multicast service delivery, traffic will be multicast along multicast service delivery, traffic will be multicast along
distribution trees that should be terminated as close to the distribution trees that should be terminated as close to the
receivers as possible for bandwidth optimization purposes. As a receivers as possible for bandwidth optimization purposes. As a
reminder, the traversal of unicast-only (access) networks is not reminder, the traversal of unicast-only (access) networks is not
considered in this document. considered in this document.
4.4.1. AF For Control Flows 4.4.1. AF For Control Flows
The IWF to process multicast signalling flows (such as IGMP or MLD The IWF to process multicast signalling flows (such as IGMP or MLD
Report messages) should be independent of the IP version and consist Report messages) should be independent of the IP version and consist
mainly of an IPv4-IPv6 adaptation element and an IP address mainly of an IPv4-IPv6 adaptation element and an IP address
translation element. The message format adaptation must follow what translation element. The message format adaptation must follow what
is specified in [RFC3810] or [RFC4601], and the device that embeds is specified in [RFC3810] or [RFC4601], and the device that embeds
the IWF device must be multicast-enabled, i.e., support IGMP, MLD the IWF device must be multicast-enabled, i.e., support IGMP, MLD and
and/or PIM, depending on the context (address family-wise) and the /or PIM, depending on the context (address family-wise) and the
design (e.g., this device could be a PIM DR in addition to a MLD design (e.g., this device could be a PIM DR in addition to a MLD
Querier). Querier).
The IWF can then be operated in the following modes: IGMP-MLD, PIMv4- The IWF can then be operated in the following modes: IGMP-MLD,
PIMv6, MLD-PIMv4 and IGMP-PIMv6. In particular, Source-Specific PIMv4-PIMv6, MLD-PIMv4 and IGMP-PIMv6. In particular, Source-
Multicast (SSM) must be supported (i.e., IGMPv3/MLDv2 signalling Specific Multicast (SSM) must be supported (i.e., IGMPv3/MLDv2
traffic as well as the ability to directly send PIM (S, G) Join signalling traffic as well as the ability to directly send PIM (S, G)
messages towards the source). Join messages towards the source).
The following sub-sections describe some interworking functions which The following sub-sections describe some interworking functions which
may be solicited, depending on the environment. may be solicited, depending on the environment.
4.4.1.1. IGMP-MLD Interworking 4.4.1.1. IGMP-MLD Interworking
The IGMP-MLD Interworking Function combines the IGMP/MLD Proxying The IGMP-MLD Interworking Function combines the IGMP/MLD Proxying
function specified in [RFC4605] and the IGMP/MLD adaptation function function specified in [RFC4605] and the IGMP/MLD adaptation function
which is meant to reflect the contents of IGMP messages into MLD which is meant to reflect the contents of IGMP messages into MLD
messages, and vice versa. messages, and vice versa.
For example, when an IGMP Report message is received to subscribe to For example, when an IGMP Report message is received to subscribe to
a given multicast group (which may be associated to a source address a given multicast group (which may be associated to a source address
if SSM mode is used), the IGMP-MLD Interworking Function MUST send an if SSM mode is used), the IGMP-MLD Interworking Function must send an
MLD Report message to subscribe to the corresponding IPv6 multicast MLD Report message to subscribe to the corresponding IPv6 multicast
group. group.
4.4.1.2. IPv4-IPv6 PIM Interworking 4.4.1.2. IPv4-IPv6 PIM Interworking
[RFC4601] allows the computation of PIM-based IPv4 or IPv6 [RFC4601] allows the computation of PIM-based IPv4 or IPv6
distribution trees; PIM is IP version agnostic. There is no specific distribution trees; PIM is IP version agnostic. There is no specific
IPv6 PIM machinery that would work differently than an IPv4 PIM IPv6 PIM machinery that would work differently than an IPv4 PIM
machinery. The new features needed for the IPv4-IPv6 PIM machinery. The new features needed for the IPv4-IPv6 PIM
Interworking Function consist in dynamically triggering the PIM Interworking Function consist in dynamically triggering the PIM
message of Address Family 1 upon receipt of the equivalent PIM message of Address Family 1 upon receipt of the equivalent PIM
message of Address Family 2. message of Address Family 2.
The address mapping MUST be performed similarly to that of the IGMP- The address mapping must be performed similarly to that of the IGMP-
MLD Interworking Function. MLD Interworking Function.
4.4.1.3. MLD-IPv4 PIM Interworking 4.4.1.3. MLD-IPv4 PIM Interworking
This IWF function is required when the MLD Querier is connected to an This IWF function is required when the MLD Querier is connected to an
IPv4 PIM domain. IPv4 PIM domain.
The address mapping MUST be performed similarly to that of the IGMP- The address mapping must be performed similarly to that of the IGMP-
MLD Interworking Function. MLD Interworking Function.
4.4.1.4. IGMP-IPv6 PIM Interworking 4.4.1.4. IGMP-IPv6 PIM Interworking
The address mapping MUST be performed similarly to that of the IGMP- The address mapping must be performed similarly to that of the IGMP-
MLD Interworking Function. MLD Interworking Function.
4.4.2. AF For Data Flows 4.4.2. AF For Data Flows
The IWF to be used for multicast data flows is operated at the The IWF to be used for multicast data flows is operated at the
boundary between IPv4 and IPv6 multicast networks. Either boundary between IPv4 and IPv6 multicast networks. Either
encapsulation/de-capsulation or translation modes can be enforced, encapsulation/de-capsulation or translation modes can be enforced,
depending on the design. Note that translation operations must depending on the design. Note that translation operations must
follow the algorithm specified in [RFC6145]. follow the algorithm specified in [RFC6145].
4.4.3. Address Mapping 4.4.3. Address Mapping
The address mapping mechanisms to be used in either a stateful or The address mapping mechanisms to be used in either a stateful or
stateless fashion need to be specified for the translation from one stateless fashion need to be specified for the translation from one
address family to the other. address family to the other.
The address formats have been defined in The address formats have been defined in
[I-D.ietf-mboned-64-multicast-address-format] and [RFC6052] for IPv4- [I-D.ietf-mboned-64-multicast-address-format] and [RFC6052] for
embedded IPv6 multicast and unicast addresses. Mapping operations IPv4-embedded IPv6 multicast and unicast addresses. Mapping
are performed in a stateless manner by the algorithms specified in operations are performed in a stateless manner by the algorithms
the aforementioned documents. specified in the aforementioned documents.
In this context, the IPv6 prefixes required for embedding IPv4 In this context, the IPv6 prefixes required for embedding IPv4
addresses can be assigned to devices that support IWF features by addresses can be assigned to devices that support IWF features by
various means (e.g., static or dynamic configuration, out-of-band various means (e.g., static or dynamic configuration, out-of-band
mechanisms, etc.). mechanisms, etc.).
If stateful approaches are used, it is recommended to carefully If stateful approaches are used, it is recommended to carefully
investigate the need to synchronize mapping states between multiple investigate the need to synchronize mapping states between multiple
boxes, and the coordination of the IWF and source/group discovery boxes, and the coordination of the IWF and source/group discovery
elements is also required, at the cost of extra complexity. elements is also required, at the cost of extra complexity.
skipping to change at page 19, line 28 skipping to change at page 16, line 50
4.5. Combination of ASM and SSM Modes 4.5. Combination of ASM and SSM Modes
The ASM (Any Source Multicast) mode could be used to optimize the The ASM (Any Source Multicast) mode could be used to optimize the
forwarding of IPv4 multicast traffic sent by different sources into forwarding of IPv4 multicast traffic sent by different sources into
the IPv6 multicast domain by selecting RP routers that could be the IPv6 multicast domain by selecting RP routers that could be
located at the border between the IPv6 and the IPv4 multicast located at the border between the IPv6 and the IPv4 multicast
domains. This design may optimize the multicast forwarding domains. This design may optimize the multicast forwarding
efficiency in the IPv6 domain when access to several IPv4 multicast efficiency in the IPv6 domain when access to several IPv4 multicast
sources needs to be granted. sources needs to be granted.
5. What Is Expected From The IETF 5. IANA Considerations
This document highlights the following IETF standardization needs:
o Specify the inter-working function as described in Sections 4.4.1
and 4.4.2. In particular:
* Specify the algorithms used by various inter-working functions,
covering both encapsulation and translation approaches
* Specify the multicast IPv4-embedded address format
* Document a 6-4 multicast architecture
* Document a 4-6-4 multicast architecture
o Document a Management Information Base (MIB) to be used for the
management of IWF functions
o Encourage the publication of various Applicability Statement
documents to reflect IWF operational experience in different
contexts
6. IANA Considerations
This document makes no request to IANA. This document makes no request to IANA.
Note to RFC Editor: this section may be removed on publication as an Note to RFC Editor: this section may be removed on publication as an
RFC. RFC.
7. Security Considerations 6. Security Considerations
Access to contents in a multicast-enabled environment raises Access to contents in a multicast-enabled environment raises
different security issues that have been already documented. This different security issues that have been already documented. This
draft does not introduce any specific security issue. draft does not introduce any specific security issue.
8. Acknowledgments 7. Acknowledgments
Special thanks to T. Taylor for providing the figures and some of the
text that illustrate the use cases depicted in Section 3. Thanks
also to H. Asaeda, M. Eubanks, N. Leymann and S. Venaas for their
valuable comments.
9. References Special thanks to T. Taylor for providing the figures and some of
the text that illustrate the use cases depicted in Section 3. Thanks
also to H. Asaeda, M. Blanchet, M. Eubanks, N. Leymann, S.
Perrault and S. Venaas for their valuable comments and support.
9.1. Normative References 8. References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 8.1. Normative References
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2236] Fenner, W., "Internet Group Management Protocol, Version [RFC2236] Fenner, W.C., "Internet Group Management Protocol, Version
2", RFC 2236, November 1997. 2", RFC 2236, November 1997.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002. 3", RFC 3376, October 2002.
[RFC3569] Bhattacharyya, S., "An Overview of Source-Specific [RFC3569] Bhattacharyya, S., "An Overview of Source-Specific
Multicast (SSM)", RFC 3569, July 2003. Multicast (SSM)", RFC 3569, July 2003.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM): "Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006. Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast "Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP
("IGMP/MLD Proxying")", RFC 4605, August 2006. /MLD Proxying")", RFC 4605, August 2006.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation [RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011. Algorithm", RFC 6145, April 2011.
9.2. Informative References 8.2. Informative References
[I-D.ietf-mboned-64-multicast-address-format] [I-D.ietf-mboned-64-multicast-address-format]
Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and
M. Xu, "IPv6 Multicast Address With Embedded IPv4 M. Xu, "IPv6 Multicast Address With Embedded IPv4
Multicast Address", Multicast Address", draft-ietf-mboned-64-multicast-
draft-ietf-mboned-64-multicast-address-format-04 (work in address-format-04 (work in progress), August 2012.
progress), August 2012.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
Authors' Addresses Authors' Addresses
Christian Jacquenet Christian Jacquenet
France Telecom Orange France Telecom Orange
4 rue du Clos Courtel 4 rue du Clos Courtel
Cesson-Sevigne 35512 Cesson-Sevigne 35512
France France
Phone: +33 2 99 12 43 82 Phone: +33 2 99 12 43 82
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