draft-ietf-mboned-deprecate-interdomain-asm-07.txt   rfc8815.txt 
Mboned M. Abrahamsson Internet Engineering Task Force (IETF) M. Abrahamsson
Internet-Draft Request for Comments: 8815
Intended status: Best Current Practice T. Chown BCP: 229 T. Chown
Expires: September 10, 2020 Jisc Category: Best Current Practice Jisc
L. Giuliano ISSN: 2070-1721 L. Giuliano
Juniper Networks, Inc. Juniper Networks, Inc.
T. Eckert T. Eckert
Futurewei Technologies Inc. Futurewei Technologies Inc.
March 9, 2020 August 2020
Deprecating ASM for Interdomain Multicast Deprecating Any-Source Multicast (ASM) for Interdomain Multicast
draft-ietf-mboned-deprecate-interdomain-asm-07
Abstract Abstract
This document recommends deprecation of the use of Any-Source This document recommends deprecation of the use of Any-Source
Multicast (ASM) for interdomain multicast. It recommends the use of Multicast (ASM) for interdomain multicast. It recommends the use of
Source-Specific Multicast (SSM) for interdomain multicast Source-Specific Multicast (SSM) for interdomain multicast
applications and recommends that hosts and routers in these applications and recommends that hosts and routers in these
deployments fully support SSM. The recommendations in this document deployments fully support SSM. The recommendations in this document
do not preclude the continued use of ASM within a single organisation do not preclude the continued use of ASM within a single organization
or domain and are especially easy to adopt in existing intradomain or domain and are especially easy to adopt in existing deployments of
ASM/PIM-SM deployments. intradomain ASM using PIM Sparse Mode (PIM-SM).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This memo documents an Internet Best Current Practice.
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 7841.
This Internet-Draft will expire on September 10, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8815.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background
2.1. Multicast service models . . . . . . . . . . . . . . . . 3 2.1. Multicast Service Models
2.2. ASM routing protocols . . . . . . . . . . . . . . . . . . 4 2.2. ASM Routing Protocols
2.2.1. PIM Sparse Mode (PIM-SM) . . . . . . . . . . . . . . 4 2.2.1. PIM Sparse Mode (PIM-SM)
2.2.2. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 4 2.2.2. Embedded-RP
2.2.3. Bidir-RP . . . . . . . . . . . . . . . . . . . . . . 5 2.2.3. BIDIR-RP
2.3. SSM Routing protocols . . . . . . . . . . . . . . . . . . 5 2.3. SSM Routing Protocols
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Discussion
3.1. Observations on ASM and SSM deployments . . . . . . . . . 5 3.1. Observations on ASM and SSM Deployments
3.2. Advantages of SSM for interdomain multicast . . . . . . . 6 3.2. Advantages of SSM for Interdomain Multicast
3.2.1. Reduced network operations complexity . . . . . . . . 7 3.2.1. Reduced Network Operations Complexity
3.2.2. No network-wide IP multicast group-address management 7 3.2.2. No Network-Wide IP Multicast Group-Address Management
3.2.3. Intrinsic source-control security . . . . . . . . . . 7 3.2.3. Intrinsic Source-Control Security
4. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 8 4. Recommendations
4.1. Deprecating use of ASM for interdomain multicast . . . . 8 4.1. Deprecating Use of ASM for Interdomain Multicast
4.2. Including network support for IGMPv3/MLDv2 . . . . . . . 9 4.2. Including Network Support for IGMPv3/MLDv2
4.3. Building application support for SSM . . . . . . . . . . 9 4.3. Building Application Support for SSM
4.4. Developing application guidance: SSM, ASM, service 4.4. Developing Application Guidance: SSM, ASM, Service
discovery . . . . . . . . . . . . . . . . . . . . . . . . 10 Discovery
4.5. Preferring SSM applications intradomain . . . . . . . . . 10 4.5. Preferring SSM Applications Intradomain
4.6. Documenting an ASM/SSM protocol mapping mechanism . . . . 10 4.6. Documenting an ASM/SSM Protocol Mapping Mechanism
4.7. Not filtering ASM addressing between domains . . . . . . 11 4.7. Not Filtering ASM Addressing between Domains
4.8. Not precluding Intradomain ASM . . . . . . . . . . . . . 11 4.8. Not Precluding Intradomain ASM
4.9. Evolving PIM deployments for SSM . . . . . . . . . . . . 11 4.9. Evolving PIM Deployments for SSM
5. Future interdomain ASM work . . . . . . . . . . . . . . . . . 12 5. Future Interdomain ASM Work
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 8. References
9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8.1. Normative References
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 8.2. Informative References
10.1. Normative References . . . . . . . . . . . . . . . . . . 13 Acknowledgments
10.2. Informative References . . . . . . . . . . . . . . . . . 14 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
IP Multicast has been deployed in various forms, within private IP Multicast has been deployed in various forms, within private
networks, the wider Internet, and federated networks such as national networks, the wider Internet, and federated networks such as national
or regional research networks. While a number of service models have or regional research networks. While a number of service models have
been published, and in many cases revised over time, there has been been published, and in many cases revised over time, there has been
no strong recommendation made by the IETF on the appropriateness of no strong recommendation made by the IETF on the appropriateness of
those models to certain scenarios, even though vendors and those models to certain scenarios, even though vendors and
federations have often made such recommendations. federations have often made such recommendations.
This document addresses this gap by making a BCP-level recommendation This document addresses this gap by making a BCP-level recommendation
to deprecate the use of Any-Source Multicast (ASM) for interdomain to deprecate the use of Any-Source Multicast (ASM) for interdomain
multicast, leaving Source-Specific Multicast (SSM) as the recommended multicast, leaving Source-Specific Multicast (SSM) as the recommended
interdomain mode of multicast. This document further recommends that interdomain mode of multicast. Therefore, this document recommends
all hosts and routers which support interdomain multicast that all hosts and routers that support interdomain multicast
applications fully support SSM. applications fully support SSM.
This document does not make any statement on the use of ASM within a This document does not make any statement on the use of ASM within a
single domain or organisation, and therefore does not preclude its single domain or organization and, therefore, does not preclude its
use. Indeed, there are application contexts for which ASM is use. Indeed, there are application contexts for which ASM is
currently still widely considered well-suited within a single domain. currently still widely considered well suited within a single domain.
The main issue in most cases with moving to SSM is application The main issue in most cases with moving to SSM is application
support. Many applications are initially deployed for intradomain support. Many applications are initially deployed for intradomain
use and are later deployed interdomain. Therefore, this document use and are later deployed interdomain. Therefore, this document
recommends applications support SSM, even when they are initially recommends that applications support SSM, even when they are
intended for intradomain use. As explained below, SSM applications initially intended for intradomain use. As explained below, SSM
are readily compatible with existing intradomain ASM deployments as applications are readily compatible with existing intradomain ASM
SSM is merely a subset of ASM. deployments using PIM-SM, as PIM-SSM is merely a subset of PIM-SM.
2. Background 2. Background
2.1. Multicast service models 2.1. Multicast Service Models
Any-Source Multicast (ASM) and Source-Specific Multicast (SSM) are Any-Source Multicast (ASM) and Source-Specific Multicast (SSM) are
the two multicast service models in use today. In ASM, as originally the two multicast service models in use today. In ASM, as originally
described in [RFC1112], receivers express interest in joining a described in [RFC1112], receivers express interest in joining a
multicast group address and routers use multicast routing protocols multicast group address, and routers use multicast routing protocols
to deliver traffic from the sender(s) to the receivers. If there are to deliver traffic from the sender(s) to the receivers. If there are
multiple senders for a given group, traffic from all senders will be multiple senders for a given group, traffic from all senders will be
delivered to the receivers. Since receivers specify only the group delivered to the receivers. Since receivers specify only the group
address, the network, and therefore the multicast routing protocols, address, the network -- and therefore the multicast routing protocols
are responsible for source discovery. -- are responsible for source discovery.
In SSM, by contrast, receivers specify both group and source when In SSM, by contrast, receivers specify both group and source when
expressing interest in joining a multicast stream. Source discovery expressing interest in joining a multicast stream. Source discovery
in SSM is handled by some out-of-band mechanism in the application in SSM is handled by some out-of-band mechanism (typically in the
layer, which drastically simplifies the network and how the multicast application layer), which drastically simplifies the network and how
routing protocols operate. the multicast routing protocols operate.
IANA has reserved specific ranges of IPv4 and IPv6 address space for IANA has reserved specific ranges of IPv4 and IPv6 address space for
multicast addressing. Guidelines for IPv4 multicast address multicast addressing. Guidelines for IPv4 multicast address
assignments can be found in [RFC5771], while guidelines for IPv6 assignments can be found in [RFC5771], while guidelines for IPv6
multicast address assignments can be found in [RFC2375] and multicast address assignments can be found in [RFC2375] and
[RFC3307]. The IPv6 multicast address format is described in [RFC3307]. The IPv6 multicast address format is described in
[RFC4291]. [RFC4291].
2.2. ASM routing protocols 2.2. ASM Routing Protocols
2.2.1. PIM Sparse Mode (PIM-SM) 2.2.1. PIM Sparse Mode (PIM-SM)
The most commonly deployed ASM routing protocol is Protocol The most commonly deployed ASM routing protocol is Protocol
Independent Multicast - Sparse Mode (PIM-SM), as detailed in Independent Multicast - Sparse Mode (PIM-SM), as detailed in
[RFC7761]. PIM-SM, as the name suggests, was designed to be used in [RFC7761]. PIM-SM, as the name suggests, was designed to be used in
scenarios where the subnets with receivers are sparsely distributed scenarios where the subnets with receivers are sparsely distributed
throughout the network. Because receivers do not indicate sender throughout the network. Because receivers do not indicate sender
addresses in ASM (but only group addresses), PIM-SM uses the concept addresses in ASM (but only group addresses), PIM-SM uses the concept
of a Rendezvous Point (RP) as a 'meeting point' for sources and of a Rendezvous Point (RP) as a "meeting point" for sources and
receivers, and all routers in a PIM-SM domain are configured to use receivers, and all routers in a PIM-SM domain are configured to use a
specific RP(s), either explicitly or through dynamic RP discovery specific RP(s), either explicitly or through dynamic RP-discovery
protocols. protocols.
To enable PIM-SM to work between multiple domains, an interdomain, To enable PIM-SM to work between multiple domains, an interdomain,
inter-RP signalling protocol known as Multicast Source Discovery inter-RP signaling protocol known as Multicast Source Discovery
Protocol (MSDP) [RFC3618] is used to allow an RP in one domain to Protocol (MSDP) [RFC3618] is used to allow an RP in one domain to
learn the existence of a source in another domain. Deployment learn of the existence of a source in another domain. Deployment
scenarios for MSDP are given in [RFC4611]. MSDP floods information scenarios for MSDP are given in [RFC4611]. MSDP floods information
about all active sources for all multicast streams to all RPs in all about all active sources for all multicast streams to all RPs in all
the domains - even if there is no receiver for a given application in the domains -- even if there is no receiver for a given application
a domain. As a result of this key scalability and security issue, in a domain. As a result of this key scalability and security issue,
along with other deployment challenges with the protocol, MSDP was along with other deployment challenges with the protocol, MSDP was
never extended to support IPv6 and remains an Experimental protocol. never extended to support IPv6 and remains an Experimental protocol.
At the time of writing, there is no IETF Proposed Standard level At the time of writing, there is no IETF interdomain solution at the
interdomain solution for IPv4 ASM multicast because MSDP was the de level of Proposed Standard for IPv4 ASM multicast, because MSDP was
facto mechanism for the interdomain source discovery problem, and it the de facto mechanism for the interdomain source discovery problem,
is Experimental. Other protocol options were investigated at the and it is Experimental. Other protocol options were investigated at
same time but were never implemented or deployed and are now historic the same time but were never implemented or deployed and are now
(e.g: [RFC3913]). historic (e.g., [RFC3913]).
2.2.2. Embedded-RP 2.2.2. Embedded-RP
Due to the availability of more bits in an IPv6 address than in IPv4, Due to the availability of more bits in an IPv6 address than in IPv4,
an IPv6-specific mechanism was designed in support of interdomain ASM an IPv6-specific mechanism was designed in support of interdomain
with PIM-SM leveraging those bits. Embedded-RP [RFC3956] allows ASM, with PIM-SM leveraging those bits. Embedded-RP [RFC3956] allows
routers supporting the protocol to determine the RP for the group routers supporting the protocol to determine the RP for the group
without any prior configuration or discovery protocols, simply by without any prior configuration or discovery protocols, simply by
observing the unicast RP address that is embedded (included) in the observing the unicast RP address that is embedded (included) in the
IPv6 multicast group address. Embedded-RP allows PIM-SM operation IPv6 multicast group address. Embedded-RP allows PIM-SM operation
across any IPv6 network in which there is an end-to-end path of across any IPv6 network in which there is an end-to-end path of
routers supporting this mechanism, including interdomain deployment. routers supporting this mechanism, including interdomain deployment.
2.2.3. Bidir-RP 2.2.3. BIDIR-RP
Bidir-PIM [RFC5015] is another protocol to support ASM. There is no BIDIR-PIM [RFC5015] is another protocol to support ASM. There is no
standardized option to operate Bidir-PIM interdomain. It is deployed standardized option to operate BIDIR-PIM interdomain. It is deployed
intradomain for applications where many sources send traffic to the intradomain for applications where many sources send traffic to the
same IP multicast groups because unlike PIM-SM it does not create same IP multicast groups because, unlike PIM-SM, it does not create
per-source state. Bidir-PIM is one of the important reasons for this per-source state. BIDIR-PIM is one of the important reasons for this
document to not deprecate intradomain ASM. document to not deprecate intradomain ASM.
2.3. SSM Routing protocols 2.3. SSM Routing Protocols
SSM is detailed in [RFC4607]. It mandates the use of PIM-SSM for SSM is detailed in [RFC4607]. It mandates the use of PIM-SSM for
routing of SSM. PIM-SSM is merely a subset of PIM-SM ([RFC7761]). routing of SSM. PIM-SSM is merely a subset of PIM-SM [RFC7761].
PIM-SSM expects the sender's source address(es) to be known in PIM-SSM expects the sender's source address(es) to be known in
advance by receivers through some out-of-band mechanism (typically in advance by receivers through some out-of-band mechanism (typically in
the application layer), and thus the receiver's designated router can the application layer); thus, the receiver's designated router can
send a PIM JOIN directly towards the source without needing to use an send a PIM Join message directly towards the source without needing
RP. to use an RP.
IPv4 addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are IPv4 addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are
designated as source-specific multicast (SSM) destination addresses designated as Source-Specific Multicast (SSM) destination addresses
and are reserved for use by source-specific applications and and are reserved for use by source-specific applications and
protocols. See [RFC4607]. For IPv6, the address prefix ff3x::/32 is protocols. For IPv6, the address prefix ff3x::/32 is reserved for
reserved for source-specific multicast use. source-specific multicast use. See [RFC4607].
3. Discussion 3. Discussion
3.1. Observations on ASM and SSM deployments 3.1. Observations on ASM and SSM Deployments
In enterprise and campus scenarios, ASM in the form of PIM-SM is In enterprise and campus scenarios, ASM in the form of PIM-SM is
likely the most commonly deployed multicast protocol. The likely the most commonly deployed multicast protocol. The
configuration and management of an RP (including RP redundancy) configuration and management of an RP (including RP redundancy)
within a single domain is a well understood operational practice. within a single domain is a well-understood operational practice.
However, if interworking with external PIM domains is needed in IPv4 However, if interworking with external PIM domains is needed in IPv4
multicast deployments, interdomain MSDP is required to exchange multicast deployments, interdomain MSDP is required to exchange
information about sources between domain RPs. Deployment experience information about sources between domain RPs. Deployment experience
has shown MSDP to be a complex and fragile protocol to manage and has shown MSDP to be a complex and fragile protocol to manage and
troubleshoot. Some of these issues include complex Reverse Path troubleshoot. Some of these issues include complex Reverse Path
Forwarding (RPF) rules, state attack protection, and filtering of Forwarding (RPF) rules, state attack protection, and filtering of
undesired sources. undesired sources.
PIM-SM is a general purpose protocol that can handle all use cases. PIM-SM is a general-purpose protocol that can handle all use cases.
In particular, it was designed for cases such as videoconferencing In particular, it was designed for cases such as videoconferencing
where multiple sources may come and go during a multicast session. where multiple sources may come and go during a multicast session.
But for cases where a single, persistent source for a group is used, But for cases where a single, persistent source for a group is used,
and receivers can be configured to know of that source, PIM-SM has and receivers can be configured to know of that source, PIM-SM has
unnecessary complexity. Therefore, SSM removes the need for many of unnecessary complexity. Therefore, SSM removes the need for many of
the most complex components of PIM-SM. the most complex components of PIM-SM.
As explained above, MSDP was not extended to support IPv6. Instead, As explained above, MSDP was not extended to support IPv6. Instead,
the proposed interdomain ASM solution for PIM-SM with IPv6 is the proposed interdomain ASM solution for PIM-SM with IPv6 is
Embedded-RP, which allows the RP address for a multicast group to be Embedded-RP, which allows the RP address for a multicast group to be
embedded in the group address, making RP discovery automatic for all embedded in the group address, making RP discovery automatic for all
routers on the path between a receiver and a sender. Embedded-RP can routers on the path between a receiver and a sender. Embedded-RP can
support lightweight ad-hoc deployments. However, it relies on a support lightweight ad hoc deployments. However, it relies on a
single RP for an entire group that could only be made resilient single RP for an entire group that could only be made resilient
within one domain. While this approach solves the MSDP issues, it within one domain. While this approach solves the MSDP issues, it
does not solve the problem of unauthorised sources sending traffic to does not solve the problem of unauthorized sources sending traffic to
ASM multicast groups; this security issue is one of biggest problems ASM multicast groups; this security issue is one of biggest problems
of interdomain multicast. of interdomain multicast.
As stated in RFC 4607, SSM is particularly well-suited to As stated in RFC 4607, SSM is particularly well suited to either
dissemination-style applications with one or more senders whose dissemination-style applications with one or more senders whose
identities are known (by some out-of-band mechanism) before the identities are known (by some out-of-band mechanism) before the
application starts running or applications that utilize some application starts running or applications that utilize some
signaling to indicate the source address of the multicast stream signaling to indicate the source address of the multicast stream
(e.g., electronic programming guide in IPTV applications). PIM-SSM (e.g., an electronic programming guide in IPTV applications).
is therefore very well-suited to applications such as classic linear Therefore, SSM through PIM-SSM is very well suited to applications
broadcast TV over IP. such as classic linear-broadcast TV over IP.
SSM requires applications, host operating systems and the designated SSM requires applications, host operating systems, and the designated
routers connected to receiving hosts to support Internet Group routers connected to receiving hosts to support Internet Group
Management Protocol, Version 3 (IGMPv3) [RFC3376] and Multicast Management Protocol, Version 3 (IGMPv3) [RFC3376] and Multicast
Listener Discovery, Version 2 (MLDv2) [RFC3810]. While support for Listener Discovery, Version 2 (MLDv2) [RFC3810]. While support for
IGMPv3 and MLDv2 has been commonplace in routing platforms for a long IGMPv3 and MLDv2 has been commonplace in routing platforms for a long
time, it has also now become widespread in common operating systems time, it has also now become widespread in common operating systems
for several years (Windows, MacOS, Linux/Android) and is no longer an for several years (Windows, Mac OS, Linux/Android) and is no longer
impediment to SSM deployment. an impediment to SSM deployment.
3.2. Advantages of SSM for interdomain multicast 3.2. Advantages of SSM for Interdomain Multicast
This section describes the three key benefits that SSM with PIM-SSM This section describes the three key benefits that SSM with PIM-SSM
has over ASM. These benefits also apply to intradomain deployment has over ASM. These benefits also apply to intradomain deployment
but are even more important in interdomain deployments. See but are even more important in interdomain deployments. See
[RFC4607] for more details. [RFC4607] for more details.
3.2.1. Reduced network operations complexity 3.2.1. Reduced Network Operations Complexity
A significant benefit of SSM is the reduced complexity that comes A significant benefit of SSM is the reduced complexity that comes
through eliminating the network-based source discovery required in through eliminating the network-based source discovery required in
ASM with PIM-SM. Specifically, SSM eliminates the need for RPs, ASM with PIM-SM. Specifically, SSM eliminates the need for RPs,
shared trees, Shortest Path Tree (SPT) switchovers, PIM registers, shared trees, Shortest Path Tree (SPT) switchovers, PIM registers,
MSDP, dynamic RP discovery mechanisms (BSR/AutoRP) and data-driven MSDP, dynamic RP-discovery mechanisms (Bootstrap Router (BSR) /
state creation. SSM simply utilizes a small subset of PIM-SM, AutoRP), and data-driven state creation. SSM simply utilizes a small
alongside the integration with IGMPv3/MLDv2, where the source address subset of PIM-SM, alongside the integration with IGMPv3/MLDv2, where
signaled from the receiver is immediately used to create (S,G) state. the source address signaled from the receiver is immediately used to
Eliminating network-based source discovery for interdomain multicast create (S,G) state. Eliminating network-based source discovery for
means the vast majority of the complexity of multicast goes away. interdomain multicast means the vast majority of the complexity of
multicast goes away.
This reduced complexity makes SSM radically simpler to manage, This reduced complexity makes SSM radically simpler to manage,
troubleshoot and operate, particularly for backbone network troubleshoot, and operate, particularly for backbone network
operators. This is the main operator motivation for the operators. This is the main operator motivation for the
recommendation to deprecate the use of ASM in interdomain scenarios. recommendation to deprecate the use of ASM in interdomain scenarios.
Note that this discussion does not apply to Bidir-PIM, and there is Note that this discussion does not apply to BIDIR-PIM, and there is
(as mentioned above) no standardized interdomain solution for Bidir- (as mentioned above) no standardized interdomain solution for BIDIR-
PIM. In Bidir-PIM, traffic is forwarded to the RP instead of PIM. In BIDIR-PIM, traffic is forwarded to the RP instead of
building state as in PIM-SM. This occurs even in the absence of building state as in PIM-SM. This occurs even in the absence of
receivers. Bidir-PIM therefore trades state complexity with receivers. Therefore, BIDIR-PIM offers a trade-off of state
unnecessary traffic (potentially a large amount). complexity at the cost of creating unnecessary traffic (potentially a
large amount).
3.2.2. No network-wide IP multicast group-address management 3.2.2. No Network-Wide IP Multicast Group-Address Management
In ASM, IP multicast group addresses need to be assigned to In ASM, IP multicast group addresses need to be assigned to
applications and instances thereof, so that two simultaneously active applications and instances thereof, so that two simultaneously active
application instances will not share the same group address and application instances will not share the same group address and
receive IP multicast traffic from each other. receive IP multicast traffic from each other.
In SSM, no such IP multicast group management is necessary. Instead, In SSM, no such IP multicast group management is necessary. Instead,
the IP multicast group address simply needs to be assigned locally on the IP multicast group address simply needs to be assigned locally on
a source like a unicast transport protocol port number: the only a source like a unicast transport protocol port number: the only
coordination required is to ensure that different applications coordination required is to ensure that different applications
running on the same host don't send to the same group address. This running on the same host don't send to the same group address. This
does not require any network operator involvement. does not require any network-operator involvement.
3.2.3. Intrinsic source-control security 3.2.3. Intrinsic Source-Control Security
SSM is implicitly secure against off-path unauthorized/undesired SSM is implicitly secure against off-path unauthorized/undesired
sources. Receivers only receive packets from the sources they sources. Receivers only receive packets from the sources they
explicitly specify in their IGMPv3/MLDv2 membership messages, as explicitly specify in their IGMPv3/MLDv2 membership messages, as
opposed to ASM where any host can send traffic to a group address and opposed to ASM, where any host can send traffic to a group address
have it transmitted to all receivers. With PIM-SSM, traffic from and have it transmitted to all receivers. With PIM-SSM, traffic from
sources not requested by any receiver will be discarded by the first- sources not requested by any receiver will be discarded by the First-
hop router (FHR) of that source, minimizing source attacks against Hop Router (FHR) of that source, minimizing source attacks against
shared network bandwidth and receivers. shared network bandwidth and receivers.
This benefit is particularly important in interdomain deployments This benefit is particularly important in interdomain deployments
because there are no standardized solutions for ASM control of because there are no standardized solutions for ASM control of
sources and the most common intradomain operational practices such as sources and the most common intradomain operational practices such as
Access Control Lists (ACL) on the sender's FHR are not feasible for Access Control Lists (ACLs) on the sender's FHR are not feasible for
interdomain deployments. interdomain deployments.
This topic is expanded upon in [RFC4609]. This topic is expanded upon in [RFC4609].
4. Recommendations 4. Recommendations
This section provides recommendations for a variety of stakeholders This section provides recommendations for a variety of stakeholders
in SSM deployment, including vendors, operators and application in SSM deployment, including vendors, operators, and application
developers, and also suggests further work that could be undertaken developers. It also suggests further work that could be undertaken
within the IETF. within the IETF.
4.1. Deprecating use of ASM for interdomain multicast 4.1. Deprecating Use of ASM for Interdomain Multicast
This document recommends that the use of ASM be deprecated for This document recommends that the use of ASM be deprecated for
interdomain multicast, and thus implicitly, that hosts and routers interdomain multicast; thus, implicitly, it recommends that hosts and
that support such interdomain applications fully support SSM and its routers that support such interdomain applications fully support SSM
associated protocols. Best current practices for deploying and its associated protocols. Best current practices for deploying
interdomain multicast using SSM are documented in [RFC8313]. interdomain multicast using SSM are documented in [RFC8313].
The recommendation applies to the use of ASM between domains where The recommendation applies to the use of ASM between domains where
either MSDP (IPv4) or Embedded-RP (IPv6) is used. either MSDP (IPv4) or Embedded-RP (IPv6) is used.
An interdomain use of ASM multicast in the context of this document An interdomain use of ASM multicast in the context of this document
is one where PIM-SM with RPs/MSDP/Embedded-RP is run on routers is one where PIM-SM with RPs/MSDP/Embedded-RP is run on routers
operated by two or more separate administrative entities. operated by two or more separate administrative entities.
The focus of this document is deprecation of inter-domain ASM The focus of this document is deprecation of interdomain ASM
multicast, and while encouraging the use of SSM within domains, it multicast, and while encouraging the use of SSM within domains, it
leaves operators free to choose to use ASM within their own domains. leaves operators free to choose to use ASM within their own domains.
A more inclusive interpretation of this recommendation is that it A more inclusive interpretation of this recommendation is that it
also extends to deprecating use of ASM in the case where PIM is also extends to deprecating use of ASM in the case where PIM is
operated in a single operator domain, but where user hosts or non-PIM operated in a single operator domain, but where user hosts or non-PIM
network edge devices are under different operator control. A typical network edge devices are under different operator control. A typical
example of this case is a service provider offering IPTV (single example of this case is a service provider offering IPTV (single
operator domain for PIM) to subscribers operating an IGMP proxy home operator domain for PIM) to subscribers operating an IGMP proxy home
gateway and IGMPv3/MLDv2 hosts (computer, tablets, set-top boxes). gateway and IGMPv3/MLDv2 hosts (computer, tablets, set-top boxes).
4.2. Including network support for IGMPv3/MLDv2 4.2. Including Network Support for IGMPv3/MLDv2
This document recommends that all hosts, router platforms and This document recommends that all hosts, router platforms, and
security appliances used for deploying multicast support the security appliances used for deploying multicast support the
components of IGMPv3 [RFC3376] and MLDv2 [RFC3810] necessary to components of IGMPv3 [RFC3376] and MLDv2 [RFC3810] necessary to
support SSM (i.e., explicitly sending source-specific reports). The support SSM (i.e., explicitly sending source-specific reports).
updated IPv6 Node Requirements RFC [RFC8504] states that MLDv2 must "IPv6 Node Requirements" [RFC8504] states that MLDv2 must be
be supported in all implementations. Such support is already supported in all implementations. Such support is already widespread
widespread in common host and router platforms. in common host and router platforms.
Further guidance on IGMPv3 and MLDv2 is given in [RFC4604]. Further guidance on IGMPv3 and MLDv2 is given in [RFC4604].
Multicast snooping is often used to limit the flooding of multicast Multicast snooping is often used to limit the flooding of multicast
traffic in a layer 2 network. With snooping, a L2 switch will traffic in a Layer 2 network. With snooping, an L2 switch will
monitor IGMP/MLD messages and only forward multicast traffic out on monitor IGMP/MLD messages and only forward multicast traffic out on
host ports that have interested receivers connected. Such snooping host ports that have interested receivers connected. Such snooping
capability should therefore support IGMPv3 and MLDv2. There is capability should therefore support IGMPv3 and MLDv2. There is
further discussion in [RFC4541]. further discussion in [RFC4541].
4.3. Building application support for SSM 4.3. Building Application Support for SSM
The recommendation to use SSM for interdomain multicast means that The recommendation to use SSM for interdomain multicast means that
applications should properly trigger the sending of IGMPv3/MLDv2 applications should properly trigger the sending of IGMPv3/MLDv2
source-specific report messages. It should be noted, however, there source-specific report messages. It should be noted, however, that
is a wide range of applications today that only support ASM. In many there is a wide range of applications today that only support ASM.
cases this is due to application developers being unaware of the In many cases, this is due to application developers being unaware of
operational concerns of networks, and the implications of using ASM the operational concerns of networks and the implications of using
versus using SSM. This document serves to provide clear direction ASM versus SSM. This document serves to provide clear direction for
for application developers who might currently only consider using application developers who might currently only consider using ASM to
ASM to instead support SSM, which only requires relatively minor instead support SSM, which only requires relatively minor changes for
changes for many applications, particularly those with single many applications, particularly those with single sources.
sources.
It is often thought that ASM is required for multicast applications It is often thought that ASM is required for multicast applications
where there are multiple sources. However, RFC 4607 also describes where there are multiple sources. However, RFC 4607 also describes
how SSM can be used instead of PIM-SM for multi-party applications: how SSM can be used instead of PIM-SM for multi-party applications:
"SSM can be used to build multi-source applications where all | SSM can be used to build multi-source applications where all
participants' identities are not known in advance, but the multi- | participants' identities are not known in advance, but the multi-
source "rendezvous" functionality does not occur in the network | source "rendezvous" functionality does not occur in the network
layer in this case. Just like in an application that uses unicast | layer in this case. Just like in an application that uses unicast
as the underlying transport, this functionality can be implemented | as the underlying transport, this functionality can be implemented
by the application or by an application-layer library." | by the application or by an application-layer library.
Some useful considerations for multicast applications can be found in Some useful considerations for multicast applications can be found in
[RFC3170]. [RFC3170].
4.4. Developing application guidance: SSM, ASM, service discovery 4.4. Developing Application Guidance: SSM, ASM, Service Discovery
Applications with many-to-many communication patterns can create more Applications with many-to-many communication patterns can create more
(S,G) state than is feasible for networks to manage, whether the (S,G) state than is feasible for networks to manage, whether the
source discovery is done by ASM with PIM-SM or at the application source discovery is done by ASM with PIM-SM or at the application
level and SSM/PIM-SM. These applications are not best supported by level and SSM/PIM-SSM. These applications are not best supported by
either SSM/PIM-SSM or ASM/PIM-SM. either SSM/PIM-SSM or ASM/PIM-SM.
Instead, these applications are better served by routing protocols Instead, these applications are better served by routing protocols
that do not create (S,G), such as Bidir-PIM. Unfortunately, today that do not create (S,G), such as BIDIR-PIM. Unfortunately, many
many applications use ASM solely for service discovery. One example applications today use ASM solely for service discovery. One example
is where clients send IP multicast packets to elicit unicast replies is where clients send IP multicast packets to elicit unicast replies
from server(s). Deploying any form of IP multicast solely in support from server(s). Deploying any form of IP multicast solely in support
of such service discovery is in general not recommended. Dedicated of such service discovery is, in general, not recommended. Dedicated
service discovery via DNS-SD [RFC6763] should be used for this service discovery via DNS-based Service Discovery (DNS-SD) [RFC6763]
instead. should be used for this instead.
This document describes best practices to explain when to use SSM in This document describes best practices to explain when to use SSM in
applications, e.g, when ASM without (S,G) state in the network is applications -- e.g., when ASM without (S,G) state in the network is
better, or when dedicated service-discovery mechanisms should be better, or when dedicated service-discovery mechanisms should be
used, but specifying these practices is outside the scope of this used. However, specifying how applications can support these
document. Further work on this subject may be expected within the practices is outside the scope of this document. Further work on
IETF. this subject may be expected within the IETF.
4.5. Preferring SSM applications intradomain 4.5. Preferring SSM Applications Intradomain
If feasible, it is recommended for applications to use SSM even if If feasible, it is recommended for applications to use SSM even if
they are initially only meant to be used in intradomain environments they are initially only meant to be used in intradomain environments
supporting ASM. Because PIM-SSM is a subset of PIM-SM, existing supporting ASM. Because PIM-SSM is a subset of PIM-SM, existing
intradomain PIM-SM networks are automatically compatible with SSM intradomain PIM-SM networks are automatically compatible with SSM
applications. Thus, SSM applications can operate alongside existing applications. Thus, SSM applications can operate alongside existing
ASM applications. SSM's benefits of simplified address management ASM applications. SSM's benefits of simplified address management
and significantly reduced operational complexity apply equally to and significantly reduced operational complexity apply equally to
intradomain use. intradomain use.
However, for some applications it may be prohibitively difficult to However, for some applications, it may be prohibitively difficult to
add support for source discovery, so intradomain ASM may still be add support for source discovery, so intradomain ASM may still be
appropriate. appropriate.
4.6. Documenting an ASM/SSM protocol mapping mechanism 4.6. Documenting an ASM/SSM Protocol Mapping Mechanism
In the case of existing ASM applications that cannot readily be In the case of existing ASM applications that cannot readily be
ported to SSM, it may be possible to use some form of protocol ported to SSM, it may be possible to use some form of protocol
mapping, i.e., to have a mechanism to translate a (*,G) join or leave mapping -- i.e., to have a mechanism to translate a (*,G) join or
to a (S,G) join or leave for a specific source S. The general leave to a (S,G) join or leave for a specific source S. The general
challenge in performing such mapping is determining where the challenge in performing such mapping is determining where the
configured source address, S, comes from. configured source address, S, comes from.
There are existing vendor-specific mechanisms deployed that achieve There are existing vendor-specific mechanisms deployed that achieve
this function, but none are documented in IETF documents. This may this function, but none are documented in IETF documents. This may
be a useful area for the IETF to work on as an interim transition be a useful area for the IETF to work on as an interim transition
mechanism. However, these mechanisms would introduce additional mechanism. However, these mechanisms would introduce additional
administrative burdens, along with the need for some form of address administrative burdens, along with the need for some form of address
management, neither of which are required in SSM. Hence, this should management, neither of which are required in SSM. Hence, this should
not be considered a long-term solution. not be considered a long-term solution.
4.7. Not filtering ASM addressing between domains 4.7. Not Filtering ASM Addressing between Domains
A key benefit of SSM is that the receiver specifies the source-group A key benefit of SSM is that the receiver specifies the source-group
tuple when signaling interest in a multicast stream. Hence, the tuple when signaling interest in a multicast stream. Hence, the
group address need not be globally unique, so there is no need for group address need not be globally unique, so there is no need for
multicast address allocation as long the reserved SSM range is used. multicast address allocation as long the reserved SSM range is used.
Despite the deprecation of interdomain ASM, it is recommended that Despite the deprecation of interdomain ASM, it is recommended that
operators should not filter ASM group ranges at domain boundaries, as operators not filter ASM group ranges at domain boundaries, as some
some form of ASM-SSM mappings may continue to be used for some time. form of ASM-SSM mappings may continue to be used for some time.
4.8. Not precluding Intradomain ASM 4.8. Not Precluding Intradomain ASM
The use of ASM within a single multicast domain such as a campus or The use of ASM within a single multicast domain such as a campus or
enterprise is still relatively common today. There are even global enterprise is still relatively common today. There are even global
enterprise networks that have successfully been using PIM-SM for many enterprise networks that have successfully been using PIM-SM for many
years. The operators of such networks most often use Anycast-RP years. The operators of such networks most often use Anycast-RP
[RFC4610] or MSDP (with IPv4) for RP resilience, at the expense of [RFC4610] or MSDP (with IPv4) for RP resilience, at the expense of
the extra operational complexity. These existing practices are the extra operational complexity. These existing practices are
unaffected by this document. unaffected by this document.
In the past decade, some Bidir-PIM deployments have scaled In the past decade, some BIDIR-PIM deployments have scaled
interdomain ASM deployments beyond the capabilities of PIM-SM. This interdomain ASM deployments beyond the capabilities of PIM-SM. This,
too is unaffected by this document, instead it is encouraged where too, is unaffected by this document; instead, it is encouraged where
necessary due to application requirements (see Section 4.4). necessary due to application requirements (see Section 4.4).
This document also does not preclude continued use of ASM with This document also does not preclude continued use of ASM with
multiple PIM-SM domains inside organisations, such as with IPv4 MSDP multiple PIM-SM domains inside organizations, such as with IPv4 MSDP
or IPv6 Embedded-RP. This includes organizations that are or IPv6 Embedded-RP. This includes organizations that are
federations and have appropriate, non-standardized mechanisms to deal federations and have appropriate, nonstandardized mechanisms to deal
with the interdomain ASM issues explained in Section 3.2. with the interdomain ASM issues explained in Section 3.2.
4.9. Evolving PIM deployments for SSM 4.9. Evolving PIM Deployments for SSM
Existing PIM-SM deployments can usually be used to run SSM Existing PIM-SM deployments can usually be used to run SSM
applications with little to no changes. In some widely available applications with few-to-no changes. In some widely available router
router implementations of PIM-SM, PIM-SSM is simply enabled by implementations of PIM-SM, PIM-SSM is simply enabled by default in
default in the designated SSM address spaces whenever PIM-SM is the designated SSM address spaces whenever PIM-SM is enabled. In
enabled. In other implementations, simple configuration options other implementations, simple configuration options exist to enable
exist to enable it. This allows migration of ASM applications to it. This allows migration of ASM applications to SSM/PIM-SSM solely
SSM/PIM-SSM solely through application-side development to handle through application-side development to handle source-signaling via
source-signaling via IGMPv3/MLDv2 and using SSM addresses. No IGMPv3/MLDv2 and using SSM addresses. No network actions are
network actions are required for this transition; unchanged ASM required for this transition; unchanged ASM applications can continue
applications can continue to co-exist without issues. to coexist without issues.
When running PIM-SM, IGMPv3/MLDv2 (S,G) membership reports may also When running PIM-SM, IGMPv3/MLDv2 (S,G) membership reports may also
result in the desired PIM-SSM (S,G) operations and bypass any RP result in the desired PIM-SSM (S,G) operations and bypass any RP
procedures. This is not standardized but depends on implementation procedures. This is not standardized but depends on implementation
and may require additional configuration in available products. In and may require additional configuration in available products. In
general, it is recommended to always use SSM address space for SSM general, it is recommended to always use SSM address space for SSM
applications. For example, the interaction of IGMPv3/MLDv2 (S,G) applications. For example, the interaction of IGMPv3/MLDv2 (S,G)
membership reports and Bidir-PIM is undefined and may not result in membership reports and BIDIR-PIM is undefined and may not result in
forwarding of any traffic. forwarding of any traffic.
Note that these migration recommendations do not include Note that these migration recommendations do not include
considerations on when or how to evolve those intradomain considerations on when or how to evolve those intradomain
applications best served by ASM/Bidir-PIM from PIM-SM to Bidir-PIM. applications best served by ASM/BIDIR-PIM from PIM-SM to BIDIR-PIM.
This may also be important but is outside the scope of this document. This may also be important but is outside the scope of this document.
5. Future interdomain ASM work 5. Future Interdomain ASM Work
Future work may attempt to overcome current limitations of ASM Future work may attempt to overcome current limitations of ASM
solutions, such as interdomain deployment solutions for Bidir-PIM, or solutions, such as interdomain deployment solutions for BIDIR-PIM or
source access control mechanisms for IPv6 PIM-SM with embedded-RP. source-access-control mechanisms for IPv6 PIM-SM with embedded-RP.
Such work could modify or amend the recommendations of this document Such work could modify or amend the recommendations of this document
(like any future IETF standards/BCP work). (like any future IETF Standards Track / BCP work).
Nevertheless, it is very unlikely that any ASM solution, even with Nevertheless, it is very unlikely that any ASM solution, even with
such future work, can ever provide the same intrinsic security and such future work, can ever provide the same intrinsic security and
network and address management simplicity as SSM (see Section 3.2). network- and address-management simplicity as SSM (see Section 3.2).
Accordingly, this document recommends that future work for general- Accordingly, this document recommends that future work for general-
purpose interdomain IP multicast focus on SSM items listed in purpose interdomain IP multicast focus on SSM items listed in
Section 4. Section 4.
6. Security Considerations 6. Security Considerations
This document adds no new security considerations. It instead This document adds no new security considerations. It instead
removes security issues incurred by interdomain ASM with PIM-SM/MSDP removes security issues incurred by interdomain ASM with PIM-SM/MSDP,
such as infrastructure control plane attacks and application and such as infrastructure control-plane attacks and application and
bandwidth/congestion attacks from unauthorised sources sending to ASM bandwidth/congestion attacks from unauthorized sources sending to ASM
multicast groups. RFC 4609 describes the additional security multicast groups. RFC 4609 describes the additional security
benefits of using SSM instead of ASM. benefits of using SSM instead of ASM.
7. IANA Considerations 7. IANA Considerations
This document makes no request of IANA. This document has no IANA actions.
Note to RFC Editor: this section may be removed upon publication as
an RFC.
8. Acknowledgments
The authors would like to thank members of the IETF mboned WG for
discussions on the content of this document, with specific thanks to
the following people for their contributions to the document: Hitoshi
Asaeda, Dale Carder, Jake Holland, Albert Manfredi, Mike McBride, Per
Nihlen, Greg Shepherd, James Stevens, Stig Venaas, Nils Warnke, and
Sandy Zhang.
9. Changelog
[RFC-Editor: Please remove this section.]
02 - Toerless: Attempt to document the issues brought up on the list
and discussion by James Stevens re. use of Bidir-PIM intradomain and
IGMP/MLD interop issues.
- NOTE: Text was not vetted by co-authors, so rev'ed just as
discussion basis.
- more subsection to highlight content. Added more detailled
discussion about downsides of ASM wrt. address management and
intrinsic source-control in SSM. Added recommendation to work on
guidance when apps are best suited for SSM vs. ASM/Bidir vs. service
discovery. Added recommendation how to evolve from PIM-SM to SSM in
existing deployments. Added section on possible future interdomain
ASM work (and why not to focus on it).
01 - Lenny: cleanup of text version, removed redundancies.
00 - initial IETF WG version. See draft-acg-mboned-deprecate-
interdomain-asm for work leading to this document.
10. References 8. References
10.1. Normative References 8.1. Normative References
[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5,
RFC 1112, DOI 10.17487/RFC1112, August 1989, RFC 1112, DOI 10.17487/RFC1112, August 1989,
<https://www.rfc-editor.org/info/rfc1112>. <https://www.rfc-editor.org/info/rfc1112>.
[RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Addresses", RFC 3307, DOI 10.17487/RFC3307, August 2002, Addresses", RFC 3307, DOI 10.17487/RFC3307, August 2002,
<https://www.rfc-editor.org/info/rfc3307>. <https://www.rfc-editor.org/info/rfc3307>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
skipping to change at page 14, line 45 skipping to change at line 613
Multicast - Sparse Mode (PIM-SM): Protocol Specification Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>. 2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8313] Tarapore, P., Ed., Sayko, R., Shepherd, G., Eckert, T., [RFC8313] Tarapore, P., Ed., Sayko, R., Shepherd, G., Eckert, T.,
Ed., and R. Krishnan, "Use of Multicast across Inter- Ed., and R. Krishnan, "Use of Multicast across Inter-
domain Peering Points", BCP 213, RFC 8313, domain Peering Points", BCP 213, RFC 8313,
DOI 10.17487/RFC8313, January 2018, DOI 10.17487/RFC8313, January 2018,
<https://www.rfc-editor.org/info/rfc8313>. <https://www.rfc-editor.org/info/rfc8313>.
10.2. Informative References 8.2. Informative References
[RFC2375] Hinden, R. and S. Deering, "IPv6 Multicast Address [RFC2375] Hinden, R. and S. Deering, "IPv6 Multicast Address
Assignments", RFC 2375, DOI 10.17487/RFC2375, July 1998, Assignments", RFC 2375, DOI 10.17487/RFC2375, July 1998,
<https://www.rfc-editor.org/info/rfc2375>. <https://www.rfc-editor.org/info/rfc2375>.
[RFC3170] Quinn, B. and K. Almeroth, "IP Multicast Applications: [RFC3170] Quinn, B. and K. Almeroth, "IP Multicast Applications:
Challenges and Solutions", RFC 3170, DOI 10.17487/RFC3170, Challenges and Solutions", RFC 3170, DOI 10.17487/RFC3170,
September 2001, <https://www.rfc-editor.org/info/rfc3170>. September 2001, <https://www.rfc-editor.org/info/rfc3170>.
[RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source
skipping to change at page 16, line 13 skipping to change at line 673
<https://www.rfc-editor.org/info/rfc5015>. <https://www.rfc-editor.org/info/rfc5015>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>. <https://www.rfc-editor.org/info/rfc6763>.
[RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node
Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504,
January 2019, <https://www.rfc-editor.org/info/rfc8504>. January 2019, <https://www.rfc-editor.org/info/rfc8504>.
Acknowledgments
The authors would like to thank members of the IETF MBONE Deployment
Working Group for discussions on the content of this document, with
specific thanks to the following people for their contributions to
the document: Hitoshi Asaeda, Dale Carder, Jake Holland, Albert
Manfredi, Mike McBride, Per Nihlen, Greg Shepherd, James Stevens,
Stig Venaas, Nils Warnke, and Sandy Zhang.
Authors' Addresses Authors' Addresses
Mikael Abrahamsson Mikael Abrahamsson
Stockholm
Sweden
Stockholm Email: swmike@swm.pp.se
Sweden
Email: swmike@swm.pp.se
Tim Chown Tim Chown
Jisc Jisc
Lumen House, Library Avenue Harwell Oxford
Harwell Oxford, Didcot OX11 0SG Lumen House, Library Avenue
United Kingdom Didcot
OX11 0SG
United Kingdom
Email: tim.chown@jisc.ac.uk Email: tim.chown@jisc.ac.uk
Lenny Giuliano Lenny Giuliano
Juniper Networks, Inc. Juniper Networks, Inc.
2251 Corporate Park Drive 2251 Corporate Park Drive
Herndon, Virginia 20171 Herndon, Virginia 20171
United States United States of America
Email: lenny@juniper.net Email: lenny@juniper.net
Toerless Eckert Toerless Eckert
Futurewei Technologies Inc. Futurewei Technologies Inc.
2330 Central Expy 2330 Central Expy
Santa Clara 95050 Santa Clara, California 95050
USA United States of America
Email: tte+ietf@cs.fau.de Email: tte@cs.fau.de
 End of changes. 100 change blocks. 
264 lines changed or deleted 234 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/