R&D Information

Development of Multicast MPLS for Nextgeneration Broadband Services—For Nationwide
Video Communication Service with High-qualityand High-reliability Point-to-point and Point-tomultipoint Transmission

NTT and Motorola*1 have succeeded in developing
Multicast MPLS*2 protocol and router software for it.
These enable multicast streaming and interactive
multimedia communication services with high quality and high reliability. With current IP (Internet protocol) multicasting, it is hard to configure point-topoint and point-to-multipoint paths simultaneouslywith such high quality and reliability. Multicast
MPLS solves this problem by using functions thatprovide guaranteed quality-of-service and trafficengineering. It will enable service providers to provide their customers with various high-quality andhigh-reliability video communication services, which
are expected to be next-generation broadband services.
Background
Service providers are in tough competition andneed to respond to various customer needs. Their customers require high-quality, high-reliability, fast, andreasonably priced services. In future, such next-generation services will include i) contents streaming
services, such as video-on-demand (VOD), IP/TV(TV over Internet protocol), and live streaming; ii)
IP-VPN (IP-based virtual private network); and iii)
interactive multimedia service, such as high-quality
VoIP (voice over IP), TV conferences, and video
chatting. For these services, multimedia service and*1 Motorola is a global company handling communication systems/components and electronic devices. Its head office is in theUSA. It provides router software to many companies and has considerable influence in this area.
*2 MPLS (multiprotocol label switching): Packets are forwarded
according to a label in the packet header, instead of according to
the IP address. Many large networks use the technology as a basis
for supporting the rapid expansion of the broadband Internet.

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quality control for point-to-point and point-to-multipoint traffic are becoming important technicalrequirements. However IP multicasting forces automatic path changes, so it needs a lot of control traffic
between nodes, which may cause service quality
degradation, and it does not support enough scalability for a nationwide service.
To solve these problems, NTT has researched thecore network functions required for next-generation
broadband service. NTT has been developing Multicast MPLS as an extension of MPLS in collaboration
with Motorola and has succeeded in developing
router software using it. NTT demonstrated Multicast
MPLS at the international conference “MPLS2003”
held in Washington D.C. from 26 to 28 Oct., 2003. A
formal announcement in the USA is made byMotorola on 27 Oct.
Features of Multicast MPLS and the routersoftware(1) Nationwide multicastingMulticast MPLS is the newest technology supporting multicasting, which is required for nextgeneration broadband service, and it retains themerits of the current MPLS. It can support multicast streaming such as IP/TV, live streaming, personal broadcasting, and video chatting for nationwide users.
(2) QoS for multiple services
Multicast MPLS supports the provision of various levels of QoS (quality of service) according
to the needs of users and services, and can provide high-quality and high-reliability broadband
service. Users can enjoy watching streamed
movies etc. without being disturbed by heavyusers.
NTT Technical Review

R&D Information

IP technology

Multicast MPLS

300 Mbit/s

200 Mbit/s

400 Mbit/s

500 Mbit/s
1 Gbit/s

1 Gbit/s

400 Mbit/s
500 Mbit/s
Congestion-avoidanceby traffic admission
control

Packets lost
because of buffer
overflow
Burst traffic

Restriction oftransmission rate

: Router: Multicast MPLS routerFig. 1. QoS functions.
IP technology

A route is determinedby the middle router.

Multicast MPLS

Dispersing
traffic

Avoiding congestion
and failure points: Router: Multicast MPLS routerFig. 2. Multicast traffic engineering functions.

(3) Simple implementation on router
The router software is an extension of current
commercial router software, so multicast MPLS
is simple to implement.
(4) Adaptable to next-generation optical network
Multicast MPLS is adaptable to various networks including next-generation optical networks because it is compatible with optical networks implementing GMPLS*3.

Vol. 1 No. 9 Dec. 2003

Technological features(1) Multicast path configuration
Multicast MPLS has good scalability for a
growing number of users because each router canconfigure a point-to-multipoint path with one
message.
*3 GMPLS (generalized multiprotocol label switching): A recent
proposed standard that extends MPLS to lower network layers
such as optical fiber and wavelength.

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R&D Information

IP technology

Multicast MPLSSource
The delay distribution
to an egress router islarge because thetransmission uses
the shortest path.

SourceSince it is not theminimum tree,
network resource
consumption is large.

D1

Distribution of delay
time is small because
the tree structure has
good symmetry.

Remaining
Remaining bandwidth
large
bandwidth is large.
is small.
small

D1

Remaining
bandwidth ismedium.
D2

DnNetwork resource
consumption is small as aresult of optimal
rendezvous point design.

Route calculationengine determines apath, by recognizing
traffic congestion.
Remaining
bandwidthis large.

D2

D3Dn
D3Fig. 3. Route calculation.

(2) Guaranteed QoSMulticast MPLS can provide quality-guaranteed and bandwidth-sharing services over pointto-multipoint communication because it can allocate bandwidth on a per-path basis (Fig. 1).
(3) Multicast traffic engineering
Multicast MPLS helps the ingress router avoid
congestion and failure points by configuring
point-to-point and point-to-multipoint traffic over
the route with guaranteed QoS. This enhances
network utility and network reliability by dispersing traffic (Fig. 2).
(4) Route calculation considering traffic information
Multicast MPLS supports the calculation ofsuitable routes with guaranteed QoS considering
network topology information, link attributes,
and residual bandwidth collected by a unicast
routing protocol. When route calculation functions are implemented in each node, multicast

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MPLS will be able to calculate suitable routes
independent of the source location (Fig. 3).
Future plans
To enable the core network to provide various
broadband services, NTT is promoting the standardization of multicast MPLS in the Internet Engineering Task Force (IETF). NTT is cooperating with software/protocol and router vendors to enhance thistechnology to better compete in the broadband market and is considering adapting it for various future
networks including the next-generation optical network.
For further information, please contact
NTT Information Sharing Laboratory Group
Musashino-shi, 180-8585 Japan
E-mail: koho@mail.rdc.ntt.co.jp

NTT Technical Review