R&D Information
Successful Demonstration of Simultaneous Wide-area Multipoint
Transmission of High-definition Streams for the Broadband
Ubiquitous Era—The World’s First Large-scale Confirmation ofBroadband Content Distribution by End Users

The Telecommunications Advancement Organization of Japan (TAO) and NTT succeeded in jointly
demonstrating multi-origin, multi-program simultaneous content distribution of high-definition(HD)class IP streams on May 15, 2003. The experiment
was conducted on the Japan Gigabit Network(JGN*1), a research network operated and administered by TAO, and the streams were transmitted usingFlexcast, which is multipoint transmission technology developed by NTT, and TAO’s load balancing
technology (details are described later). It involved
more than twenty video receivers located at fourTAO-owned research facilities.
The experiment was carried out by TAO Makuhari
Research Center and NTT Network Innovation Laboratories using an IP network constructed by linking
MPLS*2 routers via JGN. One goal was to verify thepotential of wide-area multipoint stream distribution,
specifically to prove the feasibility of simultaneous
multipoint distribution of high-volume IP streams
generated by end users.
Prior to this trial, only simultaneous distribution ofsingle HD streams to a few sites on Internet2*3 basedon IP multicast technology had been reported. This
trial is the world’s first to achieve simultaneous distribution involving multiple sources and several tensof destinations. As such, it opens the door to the fullscale distribution of high-volume streaming contentsfrom end users, which presages the broadband ubiquitous era.
The experiment verified capabilities and identified
issues requiring further study with regard to (1) transmitting technologies (Flexcast*4) to handle extensive
multiple areas and (2) quality-of-service (QoS) technologies based on dynamic load balancing that suit
MPLS routers. There were two main achievements.
(1) Simultaneous transmission of HD-class (25Mbit/s) IP stream contents from three servers tomore than twenty receivers at four sites, while98

minimizing the load on networks and servers.
(2) Equalization of network usage by autonomously switching a path between two sites, when
two independent paths were prepared and theserver traffic was increased to produce congestion. This proved the effectiveness of thedynamic load balancing among MPLS routers
to maintain quality and high-volume IP stream
distribution.
The experiment confirmed the successful resolution of the image distortion problem, caused byexcessive loading of the streaming servers or insufficient bandwidth, which previously hindered highvolume IP streaming from end users. Thus, users can*1 JGN (Japan Gigabit Network) is an open testbed administered andoperated by TAO to conduct R&D on high-speed networking andhigh-performance application technologies such as next-generation Internet technology. JGN has been open to both public andprivate entities for five years since 1999, providing a wide rangeof research opportunities. For details, see http://www.jgn.tao.go.jp/english/index_E.html(1) Ultrahigh-speed optical-fiber networks with links up to 2.4
Gbit/s and 66 access points covering all prefectures in Japan.
(2) Five shared-use research facilities (Gigabit Laboratories)(3) Ten research centers have been established by TAO to perform its own research.
*2 MPLS (Multiprotocol Label Switching) is a packet forwarding
framework standardized in the Internet Engineering Task Force,
which integrates ATM-like label swapping with network-layer
routing. In MPLS, packets are fast-forwarded at each routeraccording to short labels attached by the ingress router. Thisavoids the slow process of consulting IP headers.
*3 Internet2 is a consortium lead by over 200 universities working in
partnership with industry and government to develop and deploy
advanced IP network applications and technologies(http://www.internet2.org/).
*4 Flexcast (Flexible Stream Multicast) independently constructs thebest transmission route by adapting to traffic variations as triggered by user requests. This is an autonomous large-area multipoint transmission technology that can automatically constructand maintain optimal delivery trees as the number and location oftransmitters and receivers changes and as IP network routingchanges. Flexcast was developed by NTT.

NTT Technical Review

R&D Information

LegendHD TV sender

Conventional
distribution

Flexcast &MPLS adaptive routing

HD TV receiver

Flexcast relay nodes
branch data packets
transparently| Minimum load on
network and servers.
Distribution trees
spanned on demand.

MPLS routerF

Flexcast
relay nodes

Tohoku U.

U. Tokyo

Tohoku U.
FU. TokyoFFFFF

MakuhariKita-Kyushu

Makuhari

Kita-Kyushu

FKochi

Separate flows for each
receiver| Excessive data rate andserver overload

Kochi

Detect congestion andtake detour to equalize
network usage.

Fig. 1. Overview of the experiment.

receive images whose quality equals that of the original material. This will lead to the streaming distribution of motion pictures and videos with high quality,
which will satisfy sophisticated audiences anywhereand anytime.
Overview of the experiment (Fig. 1)(1) Network configuration• TAO’s Makuhari and Kochi Research Centers(RCs) and Annexes of Tohoku Univ. and theUniv. of Tokyo were connected via JGN (OC-3,155 Mbit/s) using MPLS routers. Multiple
Flexcast relay nodes were installed in each site.
• Multiple HD decoders were set up in each site,
more than twenty in total.
(2) The applicability and effectiveness of the transmitting technology supporting extensive multiple areas (Flexcast) was verified.
• HD streaming sets were placed in Makuhari
and Kochi RCs and an HD camera was placedin the Univ. of Tokyo Annex. UDP (user datagram protocol) video streams from these threesources were transmitted simultaneously byFlexcast.
• The number of receivers at sites was increased
randomly and multicast distribution trees wereVol. 1 No. 5 Aug. 2003

built autonomously.
• Flexcast was confirmed to use less bandwidth,
whereas the network usage in conventional distribution using multiple unicast flows increases
in proportion to the number of receivers.
(3) QoS technology based on dynamic load balancing using MPLS routers was verified.
• When congestion was intentionally created oncommunication links by introducing multiple
HD streams, MPLS routers autonomously
switched to a detour path to equalize network
usage and successfully maintained the qualityof the HD streams.
Future plans
Based on the results of this experiment, we intend
to establish technology for IP-based high-volume
wide-area multipoint stream transmission that can beused easily by everyone. We will consider businessand service-related issues regarding its application.
For further information, please contact
NTT Science and Core Technology Laboratory
GroupAtsugi-shi, 243-0198, Japan
E-mail: st-josen@tamail.rdc.ntt.co.jp
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