Internet Engineering Task Force (IETF) L. Giuliano
Request for Comments: 9706 Juniper Networks
Category: Informational C. Lenart
ISSN: 2070-1721 Verizon
R. Adam
GEANT
December 2024
TreeDN- Tree-based CDNs
TreeDN: Tree-Based Content Delivery Network (CDN) for Live Streaming to
Mass Audiences
Abstract
As Internet audience sizes for high-interest live events reach
unprecedented levels and bitrates climb to support 4K/8K 4K /8K / Augmented
Reality (AR), live streaming can place a unique type of stress upon
network resources. TreeDN is a tree-based CDN Content Delivery Network
(CDN) architecture designed to address the distinctive scaling
challenges of live streaming to mass audiences. TreeDN enables
operators to offer Replication-as-
a-Service Replication-as-a-Service (RaaS) at a fraction of
the cost of traditional, unicast-
based CDNs; unicast-based CDNs -- in some cases, there
is no additional cost to the infrastructure. In addition to
efficiently utilizing network resources to deliver existing multi-destination multi-
destination traffic, this architecture also enables new types of
content and use cases that previously were not possible or
economically viable using traditional CDN approaches. Finally,
TreeDN is a decentralized architecture and a democratizing technology
that makes content distribution more accessible to more people by
dramatically reducing the costs of replication.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
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/rfc9706.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction
2. Requirements Language
3. Problem Statement
4. Applicability
5. Multicast Challenges in the Past
6. TreeDN Architecture
6.1. TreeDN Overlays
6.2. TreeDN Native On-Net
7. Replication-as-a-Service (RaaS)
8. Decentralization/Democratization of Content Sourcing
9. Transport-Layer-Related Differences between TreeDN and
Traditional CDNs
9.1. Integration with Unicast
9.2. Reliability, Adaptive Bitrates, and Congestion Control
9.3. Authorization and Encryption
10. TreeDN Deployments
11. Operational Considerations
12. Security Consideration
13. IANA Considerations
14. References
14.1. Normative References
14.2. Informative References
Appendix A. Netverses
Acknowledgements
Authors' Addresses
1. Introduction
As Internet audience sizes for high-interest live events reach
unprecedented levels and bitrates climb to support 4K/8K 4K / 8K /
Augmented Reality (AR), live streaming can place a unique type of
stress upon network resources. TreeDN is a tree-based CDN Content
Delivery Network (CDN) architecture designed to address the
distinctive scaling challenges of live streaming to mass audiences.
TreeDN enables operators to offer Replication-as-
a-Service Replication-as-a-Service (RaaS) at
a fraction of the cost of traditional, unicast-
based unicast-based CDNs; in some
cases, there is no additional cost to the infrastructure. In
addition to efficiently utilizing network resources to deliver
existing multi-destination traffic, this architecture also enables
new types of content and use cases that previously were not possible
or economically viable using traditional CDN approaches. Finally,
TreeDN is a decentralized architecture and a democratizing technology
that makes content distribution more accessible to more people by
dramatically reducing the costs of replication.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Problem Statement
Live streaming to mass audiences can impose unique demands on network
resources. For example, live sporting events that broadcast over the
Internet to end users have a much lower tolerance for long playout
buffers than typical on-demand video streaming. Viewers of live
sporting events have long been conditioned by broadcast television to
expect to see the content in real time, with only very short buffers
for broadcast delays to prevent profanity and other objectionable
content from making on the air (this is known as the "seven-second
delay" [BROADCAST-DELAY]). With micro-betting, even this 5 to 10
second delay can be too long. By comparison, when watching on-demand
movies, an extra one- or two-minute playout buffer tends to be
perfectly acceptable for viewers. If playout buffers for live sports
are that long, viewers run the risk of being alerted to a game-
winning score from text messages from friends or cheers from the bar
across the street minutes before they view it themselves.
Another unique characteristic of live streaming is the join rate.
While on-demand video streaming can consume massive amounts of
network resources, the viewing rates tend to be smooth and
predictable. Service Providers (SPs) observe gradual levels of
traffic increases over the evening hours corresponding to prime-time
viewing habits. By comparison, viewing rates of live video streams
can more closely resemble a step function with much less
predictability as mass audiences of viewers tune in to watch the game
at the same time.
Previous efforts for more efficient network replication of multi-
destination traffic have experienced mixed success in terms of
adoption. IP multicast is widely deployed on financial networks,
video distribution networks, L3VPN networks, and certain enterprises.
However, most of these deployments are restricted to "walled-garden"
networks. Multicast over the global Internet has failed to gain
traction, as only a very small portion of the Internet is multicast
enabled at this time.
TreeDN is a tree-based CDN architecture that is the result of the
evolution of network-based replication mechanisms and is based on
lessons learned from what has and has not worked well in the past.
TreeDN addresses the fundamental issues of what has hindered
multicast from adoption on the global Internet and enables SPs the
opportunity to deliver new Replication-as-a-Service (RaaS) offerings
to content providers, while more efficiently utilizing network
resources by eliminating duplicated traffic. Thus, this improves the
experience of end users. TreeDN accomplishes this with the
combination of a simplified model of native multicast along with
network overlays to reach receivers on unicast-only parts of the
Internet.
By more efficiently supporting multi-destination traffic, TreeDN is
an architecture that can enable new types of content (such as AR live
streaming to mass audiences) that previously weren't possible or
economically viable on the Internet due to the inefficiencies of
unicast.
4. Applicability
While the primary use case mentioned throughout this document is live
streaming of multimedia content (e.g., audio, video, AR, and real-
time telemetry data), the TreeDN architecture can provide efficient
delivery for any content that needs to be replicated and delivered to
multiple destinations. For example, large software file updates
(e.g., OS upgrades) that need to be delivered to many end users in a
very short window of time can cause significant strain on network
resources. Using TreeDN, this use case can be handled much more
efficiently by the network.
5. Multicast Challenges in the Past
The following issues have been some of the primary challenges for
deployment of IP multicast over the global Internet. This is not
intended to be an exhaustive list but rather a list that provides
context for the solution and how it addresses these primary
challenges.
* The "All or Nothing" problem: IP multicast requires every Layer 3
hop between the source and receivers to be multicast enabled. To
achieve ubiquitous availability on the global Internet, this
essentially means that nearly every interface on every router and
firewall between all end hosts must support a multicast routing
protocol (such as Protocol Independent Multicast - Sparse Mode
(PIM-SM) [RFC7761] or the Multipoint Label Distribution Protocol
(mLDP) [RFC6388]). This requirement creates a bar to deployment
that is practically impossible to overcome.
* The "It's Too Complex" problem: Operators have long complained
that multicast routing protocols like PIM-SM are simply too
complex, making it costly to design, configure, manage, and
troubleshoot IP multicast in the network.
* The "Chicken and Egg" problem: There's not much multicast content
because there's not much of a multicast-enabled audience, but
there's not much of a multicast-enabled audience because there's
not much multicast content.
TreeDN is the evolution of network-based replication based on lessons
learned over decades and is designed to address the problems listed
above.
6. TreeDN Architecture
TreeDN leverages a simplified model for multicast deployment combined
with network overlays to deliver traffic to receiving hosts on
unicast-only networks. With network overlays, a service can be
achieved and delivered to end users while recognizing and tolerating
the practical realities of what is possible over a network as diverse
as the global Internet. That is, the replication service is
available to users and applications across the global Internet
regardless of what protocols may exist in the underlying networks
that constitute the underlay.
TreeDN Provider
+-------------------------------+
| |
| Native Multicast On-Net |
+----------+ | (PIM-SSM) |
| Content/ |----+ |
| Mcast | | |
| Source | | +-----------+
+----------+ +---|-------|-------| AMT Relay | +--------------+
| | +----|------+ | Unicast-Only |
+-+ +-+ . | Network |
+-+ +-+ ..........|........ |
Native Content AMT Tunnel +-------.------+
Receivers .
AMT +-+
Gateway +-+
|
Content
Receiver
Figure 1: TreeDN Provider Example
6.1. TreeDN Overlays
One overlay technology that TreeDN leverages is Automatic Multicast
Tunneling (AMT) [RFC7450]. With AMT, end hosts on unicast-only
networks (AMT Gateways) can dynamically build tunnels to routers on
the multicast-enabled part of the network (AMT Relays) and receive
multicast streams. The AMT Gateway is a thin software client that
typically sits on the receiving end host and initiates the tunnel at
an AMT Relay. The AMT Relay is a tunnel server that typically sits
at the border of the multicast network. AMT allows any end host on
the Internet to receive multicast content regardless of whether their
local provider supports multicast (aka, "off-net receivers"); this receivers"), which
addresses the "All or Nothing" problem. Links and devices that do
not support multicast are simply tunneled over; over -- they no longer
present a barrier to the overall replication service for end users.
Those networks that do deploy and support multicast, as well as the
content providers that serve up multicast content, are able to enjoy
the benefits of efficient replication and delivery. Further, these
benefits can serve as incentives for operators who do not yet support
multicast to enable it on their networks, which is a key benefit of
incremental deployment described in Section 4.3 of [RFC9049]. Once
the cost of carrying duplicated unicast tunnels is perceived by those
operators to exceed the cost of deploying multicast, they are more
likely to enable multicast on their networks. Thus, TreeDN
effectively supports incremental deployment in a way that was not
previously possible with traditional (non-overlay) multicast
networking. Finally, AMT also addresses the "Chicken and Egg"
problem, as all end hosts on the global Internet that have access to
an AMT Relay are capable of becoming audience members.
To support receiving on both native and non-native networks,
receiving hosts can first attempt to join the traffic natively, and
if no multicast traffic is received, they can fall back to AMT. This
fallback mechanism can be handled by the application layer.
In addition to AMT, other overlay technologies like the Locator/ID
Separation Protocol (LISP) [RFC9300] can be utilized to deliver
content from multicast-enabled networks to end hosts that are
separated by portions of the network (at the last/middle/first mile)
that do not support multicast.
6.2. TreeDN Native On-Net
Networks that support multicast provide the native on-net component
of TreeDN. The primary requirement of the native on-net component is
to support Source-Specific Multicast (SSM) [RFC4607]. PIM-SSM, which
is merely a subset of PIM-SM, is the multicast routing protocol
typically used in SSM. However, any multicast routing protocol
capable of supporting SSM can be used as a in the TreeDN native on-net, on-net
component, such as mLDP, Global Table Multicast (GTM) [RFC7716] and BGP-based
multicast [RFC7716], BGP-
based Multicast [BGP-MULTICAST], or even BGP Multicast VPN (BGP-MVPN)
[RFC6513] for those operators who carry the global routing table in a
VRF.
Virtual Routing and Forwarding (VRF) table. Likewise, any data plane
technology that supports SSM, including Bit Index Explicit
Replication (BIER) [RFC8279] and Segment Routing (SR) Point-to-Multipoint Point-to-
Multipoint (P2MP) [RFC9524], can be used.
The key benefit of SSM as the native on-net component of TreeDN is
that it radically simplifies the control plane needed to support
replication in the network. This simplification comes by moving
source discovery from the network layer to some sort of out-of-band
mechanism, usually in the application layer. In SSM, the receiver
uses the Internet Group Management Protocol Version 3 (IGMPv3)
[RFC3376] for IPv4 or the Multicast Listener Discovery Version 2
(MLDv2) protocol [RFC3810] for IPv6 to specify both the source and
group address of the multicast stream. This allows the last-hop
router to immediately join the multicast stream along the shortest-
path tree (SPT) without the need for shared trees. This benefit
addresses the "It's Too Complex" problem. By eliminating the need
for network-based source discovery, most of the complexity of
multicast is then eliminated, which reduces the cost of deploying and
operating a multicast network. Further rationale for this SSM-only
approach can be found in Any-Source Multicast (ASM) deprecation Deprecation
[RFC8815].
7. Replication-as-a-Service (RaaS)
Content providers have traditionally used CDNs to distribute content
that needs to be delivered to large audiences, essentially
outsourcing the task of replication to CDN providers. Most CDNs
utilize unicast delivery, as multicast is not an option due to its
lack of general availability on the global Internet. TreeDN is a CDN
architecture that leverages tree-based replication to more
efficiently utilize network resources to deliver simultaneous multi-
destination traffic. By leveraging overlay networking to address the
"All or Nothing" and "Chicken and Egg" problems, and leveraging SSM
to address the "It's Too Complex" problem, TreeDN avoids the
practical issues that previously prevented multicast from being a
viable option for CDN providers.
TreeDN has several advantages over traditional unicast-based CDN
approaches. First, the TreeDN functionality can be delivered
entirely by the existing network infrastructure. Specifically, for
operators with routers that support AMT natively, multicast traffic
can be delivered directly to end users without the need for
specialized CDN devices, which typically are servers that need to be
racked, powered, cooled, and connected to ports on routers that
otherwise could have been consumed by paying customers. In this way,
SPs can offer new RaaS functionality to content providers at
potentially zero additional cost in new equipment.
Additionally, TreeDN is an open architecture that leverages mature,
IETF-specified, and widely implemented network protocols. TreeDN
also requires far less coordination between the content provider and
the CDN operator. That is, there are no storage requirements for the
data, nor group-key management issues, since a TreeDN provider merely
forwards packets. A TreeDN provider simply needs to have enough
accounting data (e.g., traffic data, number of AMT tunnels, etc.) to
properly bill customers for the service. By contrast, traditional
unicast-based CDNs often incorporate proprietary, non-interoperable
technologies and require significant coordination between the content
provider and the CDN to handle such things as file storage, data
protection, and key management.
TreeDN introduces a deployment model that requires new considerations
for transport-layer mechanisms that are frequently relied upon by
traditional unicast-based CDNs. A discussion on these considerations
and differences can be found in Section 8. 9.
8. Decentralization/Democratization of Content Sourcing
TreeDN is an inherently decentralized architecture. This reduces the
cost for content sourcing, as any host connected to a multicast-
enabled network or on a source-capable overlay can send out a single
data stream that can be reached by an arbitrarily large audience. By
effectively reducing the marginal cost of reaching each additional
audience member to zero, from the perspective of the source, TreeDN
democratizes content sourcing on the Internet.
9. Transport-Layer-Related Differences between TreeDN and Traditional
CDNs
The focus of this document is on the network-layer components that
comprise the TreeDN architecture. This section introduces some of
the key transport-layer-related differences between TreeDN and
traditional unicast-based CDNs that should be taken into
consideration when deploying TreeDN-based services. In many cases,
these issues are more related to TCP-UDP differences between TCP and UDP than unicast-
multicast differences;
differences between unicast and multicast; thus, UDP-based solutions
can be leveraged to address most gaps. The aim of this section is to
point to some of the existing work to address these gaps, as well as
to suggest further work that could be undertaken within the IETF.
Further details of these transport-layer mechanisms are beyond the
scope of this document.
9.1. Integration with Unicast
Since SSM inherently implies unidirectional traffic flows from one to
many, mechanisms that rely on bidirectional communication between
receivers and the content provider, such provider (such as bespoke advertising,
telemetry data from receivers detailing end-user experience,
distribution of decryption keys, switching to higher/lower higher or lower
bandwidth streams, etc., etc.) are not well suited to SSM delivery. As
such, separate unicast streams between receivers and content
providers may be used for this type of "out-of-band" function while
SSM is used to deliver the actual content of interest. These "out-of-band" "out-
of-band" unicast streams SHOULD use the same congestion control and
authentication mechanisms that are used today for mass audience
unicast delivery. Generally speaking, this hybrid unicast-multicast
approach is best handled by the application layer and further detail
is beyond the scope of this document.
9.2. Reliability, Adaptive Bitrates, and Congestion Control
Traditional unicast-based CDNs frequently rely on HTTPS over TCP
transport; thus, they are able to leverage the granularity of TCP-
based mechanisms for reliability, congestion control, and adaptive
bitrate streaming. However, this granularity comes at a cost of
sending a separate data stream to each viewer. Multicast
transmissions usually employ UDP, which inherently lacks many of the
aforementioned benefits of TCP but can scale much better for mass
audiences of simultaneous viewers. Forward Error Correction (FEC) is
a mechanism that has demonstrated full recovery for up to 5% packet
loss and interruptions up to 400 ms for multicast data streams in
[EUMETSAT-TERRESTRIAL]. NACK-Oriented Reliable Multicast (NORM)
[RFC5740] leverages FEC-based repair and other Reliable Multicast
Transport (RMT) building blocks to provide end-to-end reliable
transport over multicast networks.
QUIC [RFC9000] is another popular transport used by traditional
unicast-based CDNs. While QUIC does use UDP, it does not currently
support multicast. Multicast extensions to QUIC have been proposed
in [QUIC-Multicast].
Section 4.1 of [RFC8085] describes how a sender can distribute data
across multiple multicast source-group channels so that each receiver
can join the most appropriate channels for its own reception rate
capability, thus providing adaptive bitrate capabilities for
multicast streams. [DVB-MABR] and [MAUD] extensively describe an
architecture that enables reliability and dynamic bitrate adaptation.
TreeDN deployments MUST follow the congestion control guidelines
described in Section 4.1.4.2 of [RFC7450]. A multicast application
that is being distributed over TreeDN deployments SHOULD implement
congestion control for its data transmission as described in
Section 4.1 of [RFC8085]. The AMT gateway SHOULD use the
topologically closest AMT relay. Section 3.1 of [RFC8777] describes
a set of procedures for optimal relay selection.
9.3. Authorization and Encryption
A multicast sender typically has little to no control or visibility
about which end hosts may receive the data stream. Encryption can be
used to ensure that only authorized receivers are able to access
meaningful data. That is, even if unauthorized end hosts (e.g., non-
paying)
paying end hosts) receive the data stream, without decryption keys,
the data is useless. [GKM-IKEv2] describes an extension to the
Internet Key Exchange Protocol Version 2 (IKEv2) for the purpose of
group key management. [DVB-MABR] and [MAUD] extensively describe an
architecture that includes encryption of multicast streams.
10. TreeDN Deployments
EUMETCast Terrestrial is a service from the European Organisation for
the Exploitation of Meteorological Satellites (EUMETSAT) that
delivers meteorological satellite data to end users for purposes such
as operational monitoring of climates and detection of global climate
changes. EUMETCast Terrestrial connects to the GEANT network, which
provides TreeDN services to deliver this real-time data natively to
end users on multicast-enabled networks and to end users on unicast-
only networks via a global deployment of AMT relays. Details of the
EUMETCast Terrestrial service over the GEANT TreeDN network are
described in [EUMETCast-TERRESTRIAL-AMT]. Additional details on how
this deployment uses encryption, authorization, reliability, and
unicast feedback channels for end-to-end file delivery monitoring can
be found in [EUMETSAT-TERRESTRIAL].
The Multicast Menu [Multicast-Menu] is a web-based portal that can
list and launch active multicast streams that are available on a
global TreeDN network of various research and education networks.
Details of this TreeDN network, as well as the Multicast Menu, are
described in
[Multicast-Menu]. [Offnet-Sourcing-Multicast-Menu].
The RARE network is a global testbed interconnecting several National
Research and Education Networks (NRENs) via routers running BIER.
AMT relays are deployed to deliver multicast traffic from sources on
the RARE network to receivers on unicast-only networks across the
Internet. Details of the RARE network are described in
[BIER-AMT-Deployment].
11. Operational Considerations
TreeDN is essentially the synthesis of SSM plus overlay networking
technologies like AMT. As such, any existing tools to manage,
operate, and troubleshoot a PIM-SSM domain and an AMT deployment can
be used to manage a TreeDN deployment. Protocol error handling for
PIM-SSM can be found in [RFC4607] and in Section 4.8 of [RFC7761];
for AMT, it can be found in [RFC7450].
One potential operational benefit of a multicast-based approach like
TreeDN over a traditional, unicast-based CDN is the visibility that
multicast state provides in the routing infrastructure. That is,
multicast routers maintain a forwarding cache of multicast flows that
usually includes the source address, group address, incoming/outgoing
interfaces, and forwarding rate. Generally speaking, such flow state
information is not typically available in core networks for unicast,
so additional tools outside the routing infrastructure are usually
required for monitoring CDN performance and troubleshooting issues
like packet loss location. Of course, this benefit comes at a cost
of additional state being maintained in the routers for multicast.
Additionally, since multicast leverages Reverse Path Forwarding
(RPF), the source of the content can potentially have a greater
influence over the path taken through the network from source to
native receivers/AMT relays. That is, the BGP peer advertising the
reachability of the source's subnet can do so in ways that can prefer where a
particular path through the network is preferred for multicast distribution that
distribution; these methods are not as easy to accomplish with
traditional, destination-based unicast routing.
12. Security Consideration
Since TreeDN is essentially the synthesis of SSM plus overlay
networking technologies like AMT, the TreeDN architecture introduces
no new security threats that are not already documented in SSM and
the overlay technologies that comprise it. In particular, Section 6
of [RFC7450] candidly notes that AMT, like UDP, IGMP, and MLD,
provides no mechanisms for ensuring message delivery or integrity,
nor does it provide confidentiality, since sources/groups joined
through IGMP/MLD could be associated with the particular content
being requested.
[RFC4609] and [RFC8815] describe the additional security benefits of
using SSM instead of ASM.
13. IANA Considerations
This document has no IANA actions.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
<https://www.rfc-editor.org/info/rfc3376>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/rfc3810>.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/info/rfc4607>.
[RFC6388] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
Thomas, "Label Distribution Protocol Extensions for Point-
to-Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
<https://www.rfc-editor.org/info/rfc6388>.
[RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450,
DOI 10.17487/RFC7450, February 2015,
<https://www.rfc-editor.org/info/rfc7450>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
14.2. Informative References
[Algorhyme]
Wikipedia, "Radia Perlman", September 2024,
<https://en.wikipedia.org/w/
index.php?title=Radia_Perlman&oldid=1245484160>.
[BGP-MULTICAST]
Zhang, Z. J., Giuliano, L., Patel, K., Wijnands, I.,
Mishra, M. P., and A. Gulko, "BGP Based Multicast", Work
in Progress, Internet-Draft, draft-ietf-bess-bgp-
multicast-08, 3 June 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-bess-
bgp-multicast-08>.
[BIER-AMT-Deployment]
Mate, C. and F. Loui, "BIER + & AMT Deployment in GEANT/RARE
Network", implementation", IETF
112 Proceedings, November 2021,
<https://datatracker.ietf.org/meeting/112/materials/
slides-112-mboned-bier-amt-depolyment-in-geantrare-
network-00>.
[BROADCAST-DELAY]
Wikipedia, "Broadcast delay", May 2024,
<https://en.wikipedia.org/w/
index.php?title=Broadcast_delay&oldid=1225656951>.
[DVB-MABR] DVB Project, "Adaptive media streaming over IP multicast",
DVB Document A176 Rev.3 (Fourth edition), March 2023,
<https://dvb.org/wp-content/uploads/2022/01/
A176r3_Adaptive-Media-Streaming-over-IP-Multicast_Interim-
Draft-TS-103-769-v121_March_2023.pdf>.
[EUMETCast-TERRESTRIAL-AMT]
Britton, R. and R. Adam, "EUMETCast Terrestrial over AMT",
IETF 115 Proceedings, September 2022,
<https://datatracker.ietf.org/meeting/115/materials/
slides-115-mboned-eumetcast-over-amt>.
[EUMETSAT-TERRESTRIAL]
Espanyol, O., "EUMETSAT Terrestrial Service", IETF 110
Proceedings, February 2021,
<https://datatracker.ietf.org/meeting/110/materials/
slides-110-mboned-eumetsat-multicast-over-the-mbone-00>.
[GKM-IKEv2]
Smyslov, V. and B. Weis, "Group Key Management using
IKEv2", Work in Progress, Internet-Draft, draft-ietf-
ipsecme-g-ikev2-18, 11 December 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-ipsecme-
g-ikev2-18>.
[MAUD] Nilsson, M. E., Turnbull, R. S., Stevens, T. S., and S.
Appleby, "Multicast-Assisted Unicast Delivery", IBC2023
Tech Papers, September 2023, <https://www.ibc.org/
technical-papers/ibc2023-tech-papers-multicast-assisted-
unicast-delivery/10235.article>.
[Multicast-Menu]
"Multicast Menu", <https://menu.treedn.net>.
[Offnet-Sourcing-Multicast-Menu]
Delwiche, L., "Offnet Sourcing with the Multicast Menu",
IETF 114 Proceedings, July 2022,
<https://datatracker.ietf.org/meeting/114/materials/
slides-114-mboned-offnet-sourcing-with-the-multicast-menu-
01>.
[QUIC-Multicast]
Holland, J., Pardue, L., and M. Franke, "Multicast
Extension for QUIC", Work in Progress, Internet-Draft,
draft-jholland-quic-multicast-05, 7 July 2024,
<https://datatracker.ietf.org/doc/html/draft-jholland-
quic-multicast-05>.
[RFC4609] Savola, P., Lehtonen, R., and D. Meyer, "Protocol
Independent Multicast - Sparse Mode (PIM-SM) Multicast
Routing Security Issues and Enhancements", RFC 4609,
DOI 10.17487/RFC4609, October 2006,
<https://www.rfc-editor.org/info/rfc4609>.
[RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker,
"NACK-Oriented Reliable Multicast (NORM) Transport
Protocol", RFC 5740, DOI 10.17487/RFC5740, November 2009,
<https://www.rfc-editor.org/info/rfc5740>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC7716] Zhang, J., Giuliano, L., Rosen, E., Ed., Subramanian, K.,
and D. Pacella, "Global Table Multicast with BGP Multicast
VPN (BGP-MVPN) Procedures", RFC 7716,
DOI 10.17487/RFC7716, December 2015,
<https://www.rfc-editor.org/info/rfc7716>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8777] Holland, J., "DNS Reverse IP Automatic Multicast Tunneling
(AMT) Discovery", RFC 8777, DOI 10.17487/RFC8777, April
2020, <https://www.rfc-editor.org/info/rfc8777>.
[RFC8815] Abrahamsson, M., Chown, T., Giuliano, L., and T. Eckert,
"Deprecating Any-Source Multicast (ASM) for Interdomain
Multicast", BCP 229, RFC 8815, DOI 10.17487/RFC8815,
August 2020, <https://www.rfc-editor.org/info/rfc8815>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9049] Dawkins, S., Ed., "Path Aware Networking: Obstacles to
Deployment (A Bestiary of Roads Not Taken)", RFC 9049,
DOI 10.17487/RFC9049, June 2021,
<https://www.rfc-editor.org/info/rfc9049>.
[RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
Cabellos, Ed., "The Locator/ID Separation Protocol
(LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022,
<https://www.rfc-editor.org/info/rfc9300>.
[RFC9524] Voyer, D., Ed., Filsfils, C., Parekh, R., Bidgoli, H., and
Z. Zhang, "Segment Routing Replication for Multipoint
Service Delivery", RFC 9524, DOI 10.17487/RFC9524,
February 2024, <https://www.rfc-editor.org/info/rfc9524>.
[Trees] Kilmer, J., "Trees", Poetry Foundation,
<https://www.poetryfoundation.org/poetrymagazine/
poems/12744/trees>.
Appendix A. Netverses
With inspiration from (and apologies to) Radia Perlman [Algorhyme]
and Joyce Kilmer [Trees], the following poem is not intended to
provide any normative or informative technical value on TreeDN beyond
(mild) amusement for the reader who made it this far in the document:
I think that I shall never see
A CDN more lovely than a tree.
A tree whose crucial property
Is efficient mass-audience delivery.
Using SSM for simplified operation
Of native branches that eliminate duplication.
A tree extended by AMT,
Enabling unicast-only receivers full delivery.
A tree that scales to reach millions of places
To viably support the highest of bitrate use cases.
A CDN is built by folks like me,
But only end users can generate enough demand to necessitate a tree.
Acknowledgements
Many thanks to those who have contributed to building and operating
the first TreeDN network on the Internet, including Pete Morasca,
William Zhang, Lauren Delwiche, Natalie Landsberg, Wayne Brassem,
Jake Holland, Andrew Gallo, Casey Russell, Janus Varmarken, Csaba
Mate, Frederic Loui, Max Franke, Todor Moskov, Erik Herz, Bradley
Cao, Katie Merrill, Karel Hendrych, Haruna Oseni, and Isabelle Xiong.
The writing of this document to describe the TreeDN architecture was
inspired by a conversation with Dino Farinacci and Mike McBride.
Thanks also to Jeff Haas, Vinod Kumar, Ron Bonica, Jeffrey Zhang, and
Éric Vyncke for their thoughtful reviews and suggestions, Chris
Lemmons for his detailed shepherd review, and Stephen Farrell, Magnus
Westerlund, Reese Enghardt, Jurgen Schonwalder, Carlos Pignataro,
Erik Kline, Gunter Van de Velde, Warren Kumari, and Zaheduzzaman
Sarker for their last call reviews.
Authors' Addresses
Lenny Giuliano
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
United States of America
Email: lenny@juniper.net
Chris Lenart
Verizon
22001 Loudoun County Parkway
Ashburn, VA 20147
United States of America
Email: chris.lenart@verizon.com
Rich Adam
GEANT
City House
126-130 Hills Road
Cambridge
CB2 1PQ
United Kingdom
Email: richard.adam@geant.org