Special Feature: Broadband Stream Distribution andLive Streaming Switch System for Wide-area,Low-cost, and High-quality Internet Broadcasting
Masaki Tanikawa†, Takashi Ikeda, Shigehiko Ushijima,and Hirohide Mikami
Abstract
Although there are high hopes for broadband stream broadcasting, there are many problems to besolved, such as how to increase the capacity of the delivery server and how to reduce the operation cost,
before high-quality broadcasting can be provided on a large scale and at a low cost. This article reviews
stream broadcasting technologies and introduces the Live Streaming Switch being developed in NTT
Laboratories, which enables a low-cost, stable-delivery, automated streaming service.

1. Introduction
Broadband access to the Internet, such as by ADSL
(asymmetric digital subscriber line), is spreading at
an accelerating pace. The number of broadband service users exceeded 8.8 million in Japan at the end ofAugust 2003. In parallel, streaming delivery over theInternet is gaining attention as a new means of adding
value to portal sites. For example, at a product selling
portal site, streaming delivery is used to introduce
products, or Internet broadcasting is provided in combination with a chatting capability. Broadband
streaming delivery enhances the value of IP (Internet† NTT Information Sharing Platform Laboratories
Musashino-shi, 180-8585 Japan
E-mail: tanikawa.masaki@lab.ntt.co.jp

protocol) streaming delivery, thereby increasing business opportunities (Fig. 1).
Although expectations are high for broadband
streaming delivery, there are still many problems if
high-quality Internet broadcasting is to be provided
on a large scale. The following sections of this article
review stream broadcasting technology and show
how NTT Laboratories are solving the problems.
2. Overview of stream broadcasting technology
Content can be delivered to an individual user when
he/she requests it (on-demand streaming delivery) orit can be broadcast to many users simultaneously(stream broadcasting). The primary concerns in ondemand streaming delivery are request navigation,
which involves locating servers that hold the file

Narrowband
Circuit rate (bit/s)

28.8 kService examples

Dialup/ISDN

Display quality

56 k

Picture-card show

Broadband
300 k

6MADSL

B-FLET’s

Small display VHSVHSTV

PC or set-top boxPlayer
MPEG-4

Format
Usage

1.5 M

Free/promotion

MPEG-2
Free/promotion⇔charged content

Fig. 1. Expansion of bandwidth used in stream broadcasting.

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Broadcasting Technologies and Services

requested by a user and guiding the user to the nearest server, and mirroring (caching), which reduces theload on the central server by either copying or temporarily storing popular content files in other servers.
In stream broadcasting, content, such as a live concert program, is simultaneously viewed by a large
number of users. Therefore, additional technologies
are needed for simultaneous delivery and quality controlled delivery to maintain stable viewing quality
throughout the broadcast.
Figure 2 compares three stream broadcasting
schemes. When Internet broadcasting is provided on
narrowband lines to a small number of viewers, theserver copy scheme is commonly used. One advantage of this scheme is that the service is easy to implement and operate because the existing IP network canbe used and because all servers are installed at a central site. However, if broadband content is to be delivered to a large number of users, the volume of traffic
from the central site is so huge that the circuit andserver costs can become prohibitive. For example, if
an item of content is broadcast at 1 Mbit/s to 10,000people, a bandwidth of 10 Gbit/s is needed, making it
unrealistic to deliver the content from a single center.
To solve this problem, the splitter copy scheme has
begun to be used. A proxy server (splitter) is installedat each site of the existing IP network, and stream
broadcast data from the center is copied and broadcast at each site. Since request navigation can be used
to guide the user to the nearest splitter, traffic can be
confined to the Internet service provider (ISP) serving that user. However, since there is a splitter at eachsite, the cost of operating and maintaining the splitters is high. For example, to maintain a stable service,
Server copy

it would be necessary for each site to monitor video
quality.
Instead of this unicast splitter-copy, IP multicast
broadcasting is often tried. Although this scheme
looks effective at first glance, it actually raises many
problems in its application to a broadcasting service
because of the intrinsic problems of the IP multicast
service model. For example, since the basic IP multicast service model allows anyone to deliver content
and anyone to receive content (the “any source–anyclient” model), some mechanism must be implemented separately to prevent unauthorized delivery or
reception of content when the service is to be provided commercially. In addition, owing to the lack of ascalable multicast routing protocol covering multiple
domains, a tremendous quantity of resources isrequired to manage the routing table at each multicast
router in a large-scale, multi-channel broadcasting
service [1]. In addition, delivery performance tends
to decrease as the volume of routing tables increases.
Because of these problems, IP multicasting has notbeen applied to a commercial service even though 15years have passed since the emergence of the technology. J/Splash and numerous other multicast trials
have been carried out, but they have ended. A technological breakthrough is needed for IP multicasting.
Besides the broadcasting schemes shown in Fig. 2,
streaming broadcasting using the peer-to-peer (P2P)
scheme has recently emerged. At present, this technology is mainly applied to narrowband content
delivery because it is difficult to control the performance/circuit quality of the client. The application ofthe P2P scheme to broadband stream broadcasting is
introduced in the next article: “Peer-to-peer-based,

Splitter copy

IP multicast router copy
Copy

Copy

Copy

Relay

Multicast
RouterSplitter

End user

Relay

RouterRouter

Video

Video
Splitter

Existing
IP network

EncoderStreamserver

Relay
Multicast
RouterRouterEncoderStreamserverExisting
IP network

Multicast
RouterVideo

EncoderStreamMulticast server
IP network

Player (PC)

Fig. 2. Comparison of stream broadcasting schemes.

Vol. 1 No. 7 Oct. 2003

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Special Feature

High-quality Live Video Delivery System for Business-to-business Applications”.
3. Overview of Live Streaming Switch system

combination with an already commonly used off-theshelf streaming system and requires no special software or plug-ins at client terminals. Thus, it enables
an existing streaming system to be upgraded smoothly.

NTT Information Sharing Platform Laboratories isdeveloping a Live Streaming Switch (LSS) for highquality, large-scale, and low-cost Internet broadcasting [2]. LSS is a software program that runs on a general-purpose PC server. The software is installed in
the central content servers and other sites in an existing IP network to provide Internet broadcasting on alarge scale and at a low cost (Fig. 3). The LSS system
consists of splitters (LSS-SPLs), which enable a single general-purpose PC server to achieve a delivery
performance on the order of gigabits per second, andan integrated stream broadcasting management system (LSS-SMS), which enables centralized management to perform integrated monitoring/control of distributed splitters and stream servers. LSS is used in3.1 LSS-SPL system
In conventional stream servers, session control anddelivery are usually not separated. In contrast, inLSS-SPL, they are separated (Fig. 4). This server
architecture prevents the operating system socket
processing load from becoming a processing bottleneck, as it does in conventional servers, and enables
stream copying at the driver layer. With this architecture, even a general-purpose server can achieve
broadcasting performance nearly equivalent to theperformance of the gigabit Ethernet network interface card (GbE-NIC), which is more than ten times
the performance of an existing server (Fig. 5).
In addition, LSS-SPL changes the streaming rateand controls packet retransmission based on the line

1. Reduction in delivery cost
2. Enhanced video quality

3. Reduction inoperation andmaintenance cost

LSS-SMS

Content holder

Data center

LSS-SPL
LSS-SPL

LSS-SPL

StreamEncoder
serverEnd
user

Business
content
Consumer
content

Local IP network
Router/ (FLET’s)switchRouter/switch
Enduser

ISP
network
Router/switch

Fig. 3. Overview of Live Streaming Switch (LSS) system.

Conventional technology: Existing stream server

Session control:• Performed by application layer• Stream protocol processing

Performed by server software on PC or workstation
LSS

Control

Bottlenecks
Processing load on application layer
Socket processing load on
general-purpose OSDelivery

General-purpose
OS
Stream playerSetting

Control packet

Transport network

Stream server•••Gbit/s stream
delivery capability

Stream datapacket

Delivery:• Performed by OS/driver layer• High-speed packet copying processing

Fig. 4. LSS-SPL software architecture.

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Broadcasting throughput ratio

Special Feature

LSS-SMS

12(2) Simultaneous display ofserver’s status

10Player

8
Existing server
LSS-SPL

6Referenceperformance

4Server(1) Autonomous
quality monitoringEncoderServer

20

Delivery status
notification
Management
agent

0500
1000
1500
Content bandwidth (kbit/s)

ServerFig. 5. Comparison of broadcasting
throughput.

condition and packet reception status ofeach client to keep the quality of stream
broadcasting on an existing IP network.
These capabilities minimize the degradation of viewing quality even when the IP
network is congested or packets are lost.
Moreover, when a stream server runningon a general-purpose OS is used continuously for a long time, packet arrival fluctuation gradually happens, which
degrades viewing quality [3]. To preventthis, LSS-SPL has a connection refreshing function, which monitors the quality
at the streaming level. If it detects an
unstable streaming session, the session isrefreshed so that stream broadcasting service can be provided stably 24 hours aday.
3.2 LSS-SMS system
Since stream broadcasting requires the continuous
stable delivery of programs, it has been necessary tomonitor from an operations center as well as at everysite to visually inspect the delivery status so that not
only service interruptions or network failures but alsodegradation in video quality can be detected as soonas possible. That is to say, maintenance staff must not
only monitor service status, traffic conditions, and thenumber of simultaneously operating stream connections, but also determine whether video and audio
signals are being delivered satisfactorily throughout
the live broadcast.
Our LSS-SMS system has a management agent
built into each delivery server/splitter. The management agent monitors not only service status but also
streaming delivery quality, and, if it detects any
degradation in quality, it switches the delivery routes(Fig. 6). Specifically, the management agent monitorsVol. 1 No. 7 Oct. 2003

Server(3) Autonomous switching control

Fig. 6. Outline of LSS-SMS configuration.

Fig. 7. LSS-SMS display window example.

streaming delivery quality at the content level, and,based on this quality information, such as fluctuations in packet arrivals, switches the upstream servers
without requiring human judgment or control bymaintenance staff. This eliminates the need for constant visual inspection by maintenance staff, so
reducing the operation cost dramatically.
LSS-SMS also allows centralized monitoring andcan display the service status and stream flow statusof each item of content at each site (Fig. 7). It also
allows bulk control of deliveries based on our streaming expertise. This enables 24-hour-a-day operationof a stream broadcasting service. The time it takes todetect degradation in quality, analyze status, andrestore quality has been reduced from over ten minutes in conventional systems to less than one minute(mainly for detecting quality degradation and buffering data at each client after failure recovery).

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4. Examples of existing installations and futurestudies
LSS has been deployed by NTT operating companies in many trial and commercial services. For
example, it was used to build, at a quite a low cost, alarge live broadcasting network with widely distributed sites, which provides Japan’s first and largest
commercial live 1-Mbit/s delivery 24 hours a day. Inaddition, the application of connection refreshingtechnology has made it possible to provide a stabledelivery of live broadband content 24 hours a day,something that was difficult to achieve with conventional systems.
LSS was also used to provide a late-night radio
broadcasting service in combination with an existingP2P system. LSS provided a stable stream flow
(packet flow) to the P2P system, and made it possible
to operate and maintain the late-night broadcasts
from a remote operating center managed by operators
who are not skilled in streaming delivery.
We will continue to develop systems that will support the expansion of steam broadcasting business by
NTT operating companies.
References
[1]

[2]

[3]

62

I. Stoica, T. S. Eugene Ng, H. Zhang, “REUNITE: A Recursive Unicast Approach to Multicast,” INFOCOM’00, Tel-Aviv, Israel, Mar.
2000.
K. Yamada, T. Shiroshita, and S. Ushijima, “Large-capacity Content
Delivery System for B-to-E and B-to-C: MDS-Dome/Megacast,LSS,” NTT Technical Journal, Vol. 14, No. 4, pp. 46-49, 2002 (inJapanese).
M. Tanikawa, T. Ikeda, and S. Ushijima, “Proposal and Evaluation ofLarge-scale Stream Broadcasting Management System Architecture,”
IEICE Technical Report IN2002-238, 2003 (in Japanese).

Masaki Tanikawa
Research Engineer, Communication Platform
SE Project, NTT Information Sharing Platform
Laboratories.
He received the B.E. and M.E. degrees in systems science from Tokyo Institute of Technology, Tokyo in 1993 and 1995, respectively. In1995, he joined NTT. He is engaged in researchand development of a wide-area Internet streaming system. He is a member of the Institute ofElectronics, Information and Communication
Engineers (IEICE).

Takashi Ikeda
Communication Platform SE Project, NTT
Information Sharing Platform Laboratories.
He received the B.S. and M.S. degrees in electrical engineering from Keio University, Kanagawa in 1998 and 2000, respectively. In 2000, hejoined NTT Information Sharing Platform Laboratories, Tokyo, Japan. He is engaged in thedevelopment of an architecture for a wide-area
streaming broadcast network.

Shigehiko Ushijima
Senior Research Engineer, Supervisor, Communication Platform SE Project, NTT Information Sharing Platform Laboratories.
He received the B.E. and M.E. degrees in electronic engineering from Keio University, Kanagawa in 1986 and 1988, respectively. In 1988, hejoined NTT Communication Switching Laboratories, Tokyo, Japan. His recent research area iscontent delivery networks. He is a member ofIEICE.

Hirohide Mikami
Senior Research Engineer, Supervisor, Development Project Leader, Communication Platform SE Project, NTT Information Sharing Platform Laboratories.
He received the B.E. and M.E. degrees in engineering from the University of Electro-Communications,Tokyo in 1976 and 1978, respectively.
In 1978, he joined the Electrical Communication
Laboratories, Nippon Telegraph and Telephone
Public Corporation (now NTT), Tokyo, Japan,
where he engaged in research on dataflow
machines, LISP machines, visual programming,
object-oriented programming, the Internet, andIPv6 next-generation networks. He is currently
engaged in the development of nomadic systems
and content delivery systems. He is a member ofIEICE, the Information Processing Society ofJapan, and IEEE.

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