Internet DRAFT - draft-giuliano-treedn
draft-giuliano-treedn
MOPS L. Giuliano
Internet-Draft Juniper Networks
Intended status: Informational C. Lenart
Expires: 5 June 2023 Verizon
R. Adam
GEANT
2 December 2022
TreeDN- Tree-based CDNs for Live Streaming to Mass Audiences
draft-giuliano-treedn-02
Abstract
As Internet audience sizes for high-interest live events reach
unprecedented levels and bitrates climb to support 4K/8K/AR, live
streaming can place a unique type of stress upon network resources.
TreeDN is a tree-based CDN architecture designed to address the
distinctive scaling challenges of live streaming to mass audiences.
TreeDN enables operators to offer Replication-as-a-Service (RaaS) at
a fraction the cost of traditional, unicast-based CDNs- in some
cases, at 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 weren't possible or
economically viable using traditional CDN approaches. Finally,
TreeDN is a decentralized architecture and a democratizing technology
for content distribution.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 June 2023.
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Copyright Notice
Copyright (c) 2022 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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
4. TreeDN Architecture . . . . . . . . . . . . . . . . . . . . . 4
4.1. TreeDN Overlays . . . . . . . . . . . . . . . . . . . . . 5
4.2. TreeDN Native On-Net . . . . . . . . . . . . . . . . . . 5
5. Replication-as-a-Service (RaaS) . . . . . . . . . . . . . . . 6
6. Decentralization/Democratization of Content Sourcing . . . . 7
7. Integration with Unicast . . . . . . . . . . . . . . . . . . 7
8. Security Consideration . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Live streaming to mass audiences can impose unique demands on network
resources. For example, live sporting events broadcast over the
Internet to end users has 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 (the "seven-second delay"). With
micro-betting, even this 5-10 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
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risk of being alerted to the 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 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 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 step functions with much less predictability as mass
audiences of viewers tune in to watch the game at the same time.
Previous efforts at 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.
But 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 the result of the evolution of network-based replication
mechanisms 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 service providers the opportunity to deliver new Replication-
as-a-Service (RaaS) offerings to content providers, while more
efficiently utilizing network resources, and thus, improving the
experience of end users. Further, by more efficiently supporting
multi-destination traffic, TreeDN is an architecture that can enable
new types of content, such as Augmented Reality (AR) live streaming
to mass audiences, that previously weren't possible or economically
viable on the Internet due to the inefficiencies of unicast.
1.1. 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.
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2. Applicability
While the primary use case mentioned throughout this document is live
streaming of multimedia content (audio, video, AR, real-time
telemetry data), the TreeDN architecture is ideal for any content
that needs to be replicated and delivered to multiple destinations.
For example, large software file updates (eg, 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 be handled much more efficiently by the network.
3. Problem Statement
The following issues have been the primary challenges for deployment
of IP multicast over the global Internet:
* The "All or Nothing" Problem: IP multicast requires every layer 3
hop between source and receivers to be multicast-enabled. To
achieve ubiquitous availability on the global Internet, this
essentially means nearly every interface on every router and
firewall on the Internet must support a multicast routing protocol
like PIM-SM [RFC7761] or 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.
4. TreeDN Architecture
TreeDN leverages advances in the availability and understanding of
overlay and underlay networking. 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 regardless of what protocols
may exist in the underlying networks.
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4.1. TreeDN Overlays
One overlay technology that TreeDN leverages is Automatic Multicast
Tunneling (AMT) [RFC7450]. With AMT, users 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 which
typically sits on the receiving end host and initiates the tunnel at
an AMT Relay, which 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"), which
addresses the "All or Nothing" Problem. Links and devices that do
not support multicast are simply tunneled 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. 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. In this way, 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
potential audience members.
In addition to AMT, other overlay technologies like Locator/ID
Separation Protocol (LISP) [RFC6830] 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.
4.2. TreeDN Native On-Net
Networks that support multicast provide the native on-net component
of TreeDN. The primary requirement of the native on-net 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 TreeDN native on-net, such
as mLDP, GTM [RFC7716] and BGP-based Multicast
[I-D.ietf-bess-bgp-multicast], or even BGP-MVPN [RFC6513] for those
operators who carry the global routing table in a VRF. Likewise, any
data plane technology that supports SSM, including BIER [RFC8279] and
SR-P2MP [I-D.ietf-spring-sr-replication-segment] can be used.
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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 benefit addresses the "It's Too
Complex" Problem. Most of the complexity of multicast is eliminated
in SSM, which reduces the cost of deploying and operating a multicast
network. Further rationale for this SSM-only approach can be found
in ASM Deprecation [RFC8815].
5. 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 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 and connected to revenue-generating ports on routers.
In this way, SPs can offer new RaaS functionality to content
providers at potentially zero additional cost in new equipment
(modulo the additional bandwidth consumption).
Additionally, TreeDN is an open, standards-based architecture based
on mature, widely implemented 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 (eg, 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.
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6. 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 to zero the marginal cost to the
source of reaching each additional audience member, TreeDN
democratizes content sourcing on the Internet.
7. 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 as bespoke advertising,
telemetry data from receivers detailing end user experience,
distribution of decryption keys, switching to higher/lower bandwidth
streams, 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" functions while SSM is used to deliver
the actual content of interest. Further details on this hybrid
unicast-multicast model for content delivery are beyond the scope of
this document.
8. Security Consideration
TreeDN is essentially the synthesis of SSM plus overlay networking
technologies like AMT. As such, the TreeDN architecture introduces
no new security threats that aren't already documented in SSM and the
overlay technologies that comprise it. Further, RFC 4609 and RFC
8815 describes the additional security benefits of using SSM instead
of ASM.
9. IANA Considerations
This document has no IANA actions.
10. 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 and Erik Herz. 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 and Vinod Kumar for their thoughtful reviews
and suggestions.
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11. References
11.1. 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>.
[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>.
11.2. Informative References
[I-D.ietf-bess-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-04, 7 January 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-bgp-
multicast-04.txt>.
[I-D.ietf-spring-sr-replication-segment]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
J. Zhang, "SR Replication Segment for Multi-point Service
Delivery", Work in Progress, Internet-Draft, draft-ietf-
spring-sr-replication-segment-10, 20 October 2022,
<https://www.ietf.org/archive/id/draft-ietf-spring-sr-
replication-segment-10.txt>.
[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>.
[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>.
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[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>.
[RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450,
DOI 10.17487/RFC7450, February 2015,
<https://www.rfc-editor.org/info/rfc7450>.
[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>.
[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>.
[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>.
[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>.
Authors' Addresses
Lenny Giuliano
Juniper Networks
2251 Corporate Park Drive
Herndon, 20171
United States of America
Email: lenny@juniper.net
Chris Lenart
Verizon
22001 Loudoun County Parkway
Ashburn, 95134
United States of America
Email: chris.lenart@verizon.com
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Rich Adam
GEANT
City House
126-130 Hills Road
Cambridge
CB2 1PQ
United Kingdom
Email: richard.adam@geant.org
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