Special Feature: Next Generation Network—RENA

Resonant Communication NetworkArchitecture (RENA)
Kazuhiro Nagayama†, Takashi Hanazawa,
and Nobuyuki Watanabe
Abstract
This article gives an overview of NTT’s resonant communication network architecture (RENA), which
provides superior usability—a key aspect of NTT’s vision of a new optical generation—and opens theway to a genuinely realistic communication environment, which was impossible with the narrowband
transmission capabilities of the past.

1. Concept of a resonant communicationnetwork
Based on NTT’s vision of a new optical generation,
the NTT Group committed itself in November 2002
to a major new initiative to develop and deploy technologies to support broadband-based resonant communications [1], [2]. The initiative, which is to be
implemented over the next five years, aims to make aresonant communication network environment withexceptional usability and create diverse feature-rich
new services and business opportunities based on it.
The network must satisfy several advanced requirements to create such a public infrastructure. The mostimportant ones are given below:• Support for tens of millions of broadband subscribers: The number of IP network users will continue to increase, and there will be a vast increase in
the number of terminals (including information
appliances, radio-frequency ID tags, and sensors)connected to the network.
• Ability to accommodate changing patterns of network use: It must support access by a diverse rangeof different types and modes of communication
including end-to-end and multipoint communications.
• Quality of Service (QoS) assurance: It must offer a† NTT Resonant Network Project
Chiyoda-ku, 100-8116 Japan
E-mail: nagayama.kazuhiro@lab.ntt.co.jp

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range of reliability conditions and QoS options
from best-effort to assured-quality services.
• Assured network security and reliability: Users
must have total confidence that their privacy will befully protected when they use the network.
• Good usability: The network must support safe,
secure communications without requiring any technical knowledge or difficult setup procedures on thepart of users.
• Platform functions that support and promote business opportunities: It must support authenticationand other shared functions so that anyone can easily set up a new business using the network.
To meet all of these requirements, we are developing a resonant communication network concept thatprovides reliable end-to-end communications andsupports the creation of diverse feature-rich services
and new business opportunities, and we are striving tocontinually upgrade and enhance its usability (Fig. 1).
2. Benchmark services
The concept of the resonant communication network can be understood more clearly in terms of thefollowing reference services and capabilities. Once
we have achieved the cost-effective implementationof these capabilities, we will have met our goals forthe network.
(1) Interactive real-time end-to-end communications: Ability to support interactive real-time voice,high-quality video, and other media between users
NTT Technical Review

Provides reliable end-to-end communications

Encourages the creation of feature-rich services andnew business opportunities

Ensures end-to-end realtime connectivity

Platform capabilities supporting value-added
network services and ubiquitous services

Diverse levels of quality, reliability
Platform capabilities supporting application layer

Diverse levels of security
Diverse service menus
Assured scale andfunction extensibility

Provisioning of service connection functions

Can easily accommodate
upgrades and new technologies

Automated labor-saving setup of terminals
and networks
End-to-end operation including homenetworks and terminals

Continually enhances end-user usability

Fig. 1. Concept of the resonant communication network.

in 1-to-1, N-to-N, and other distribution arrangements.
(2) IP telephony services: Support for end-to-end
voice over Internet protocol.
(3) Virtual private network (VPN) services: Ability
to configure secure VPNs connecting any numberof specified points over the public network.
(4) Content delivery services: Ability to deliver
video and other media securely with appropriatequality to large numbers of users.
(5) Nomadic services: Support for seamless user/terminal mobility even for different network connection environments.
(6) Sensor network services: Support for a ubiquitous environment using network-ready sensors andradio-frequency identification tags.
(7) Data communication services: Support for home
control, customer support, and other remote equipment control environments.
(8) Public Internet interface: Ability to access theglobal Internet.

emerge in the future. We call the network architecturethat will provide this support the Resonant Communication Network Architecture (RENA). As shown inFig. 2, it consists of user networks, access networks,a core transmission network, a control signalingtransmission network, and an operations and maintenance network, which are integrated through the centralized control functions of a service/network control platform. One notable feature of RENA is its ability to support a range of QoS levels. Starting with the
top-tier service, RENA can provide a premium bandwidth-guaranteed service comparable to a leasedline, a second-tier priority service that provides guarantees involving various factors (e.g., bandwidth,latency, delay variation, and packet loss ratio), and abest-effort economy service that provides Internetlike quality but with no service quality guarantees.
Note that to ensure stable traffic so that these guarantees can be made, several differentiated classes of
end-to-end connection reliability must also be provided.

3. Network architecture

3.1 Components of RENA
The user network provides the point of access for adiverse range of user devices and equipment. For
example, telephones, personal computers and printers,
audio-visual digital equipment such as TVs and DVD
players, and information appliances can be connectedGoing beyond the benchmark services listed above,
the resonant communication network must also support end-to-end connectivity, security, quality classes, and usability for the many new services that will
Vol. 1 No. 6 Sep. 2003

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Special Feature

Application service support functions

Supports
communications services
with multiple
QoS classes
and secure
end-to-end
communications

ISP/ASP

Resonant communication network

Service-specificfunctionsInteractive
VoIP
VPN
end-to-end
functions functions functions

CDN
functions

NomadicfunctionsCore nodeCore transmission
network

Core node

Edge node

Edge node

OLT
Access networks
HGW

OLT

ONUONUHGWTV InformationTVappliance TVPC
conferencing conferencing

User networks

Operations and maintenance network

Control signaling transmission network

Sharing functions
Service/network control platform

PSTN

OSS

PCphone

OLT: optical line terminal, ONU: optical network unit, OSS: operation support systems, CDN: contents delivery networks

Fig. 2. Resonant communication network architecture.

to home networks; IP Centrex systems and mail andweb servers can be connected to corporate networks;
and other kinds of devices such as sensors and RFID
(radio frequency identification) tag readers can also
be connected. It is essential that all these various
types of terminal equipment can be connected via theuser network regardless of the interface and can takefull advantage of RENA’s powerful features. We are
now developing a home gateway (HGW) that will
provide a point of access to the resonant communication network. Its functions include IPv4/IPv6 protocol termination, multicast protocol termination, SIP
signal termination, IP telephony termination, quality
control through Layer 2 VLAN (virtual LAN) tagsand Layer 3 traffic class, compensation of quality
degradation, security control that prevents unauthorized assess, packet routing control, address management, and remote operation.
The access network is implemented as either a dedicated or shared line connecting a user network to theedge of the core transmission network, the control
signaling transmission network, and the operations
and maintenance network. It supports a range of QoSclasses at Layers 1, 2, and 3 and robust security. The
access network for RENA will provide throughputs
ranging from 10 to 100 Mbit/s for general users and50

ranging from 10 Mbit/s to 10 Gbit/s for corporate
users including SOHO (small office home office)customers. The actual physical network could beimplemented as a passive optical network (PON), asa media converter, or as a hybrid optical and fixedwireless access line, and it is assumed that these different facilities would complement the existing
ADSL (asymmetric digital subscriber line), whose
bandwidth and QoS performance are easily influenced by external factors.
Turning next to the core transmission network, considering the growing demand for the benchmark services described above, we can anticipate a need forterabit-class networks in only a few years. Therefore,
we are developing a cost-effective, flexible networkthat combines the high-speed delivery capability ofphotonics and the practicality of IP technology. Morespecifically, we have taken an approach called“multi-layer pass-through” that identifies the destination of packets at the edge node of the core transmission network and routes the packets across the network at high speed using the best path available: thelightwaves simply pass through intermediate corenodes. To ensure quality parameters are maintained
across the service, the packets are mapped to a QoSlevel and an IP packet flow control level from edge toNTT Technical Review

Special Featureedge of the core transmission network, so the specified quality is maintained without QoS control processing at any of the intermediate nodes.
The RENA interface supports both IPv4 and IPv6
protocols, while a dual stack IPv4/IPv6 transmission
scheme is used for the core transmission network. To
enable interconnection between terminals dedicatedto only IPv4 or IPv6, the network also supports automatic conversion between these protocols.
Even though multicasting can be used on the samenetworks as unicasting, authentication-enabled multicasting protocols are supported for content delivery(the Internet Group Management Protocol for user
authentication (IGMP) and the Multicast Listener
Discovery Authentication (MLDA) protocol).
Finally, a robust security technology called Moving
Firewall (MovingFW) [3] is being implemented toprotect RENA against denial-of-service (DoS) anddistributed denial-of-service (DDoS) attacks, and toprovide a reliable, secure network environment.
When an attack is detected, this firewall technology
effectively protects large portions of the network bytracing back and stopping the attack near its source.
The service/network control platform also supports
end-to-end connectivity, quality control, security,usability, and service control functions. Moreover,the platform provides service connection capabilities
that enable corporate users and service providers toeasily link their applications to the network and takefull advantage of RENA’s features. Its functions arelisted in Table 1 on page 58. They are all implemented on servers, and to promote better reliability for alarge-scale network, clustering and multi-homing
techniques are employed across multiple servers.
The control signaling transmission network is a
dedicated network that carries control signals supporting the service/network control platform, the user
networks, and the transmission network. Its basicroles are to prevent the loss of signals used for control
functions, to minimize transmission latency, and toensure proper sequencing, and security.
The operations and maintenance network is a dedicated network supporting end-to-end operations. It
provides immediate intelligence about traffic conditions in the access, core transmission, and control signaling transmission networks, and about the working
status of equipment, thus enabling continual smooth
end-to-end operations. It also enables remote maintenance for the home gateway.

Vol. 1 No. 6 Sep. 2003

4. Conclusion
Inspired by the original vision of communications
as a means to overcome time and distance, we aremoving quickly to put in place a network that,through video and other capabilities, supports genuine more natural communications fostering theemergence of the multiplizing of individuals (acoined term meaning that one individual simultaneously plays several roles to fulfill potential “intelligence”) and Web-chain behavioral models.
References
[1]

[2]

[3]

N. Wada, “Vision for a New Optical Generation—Broadband Leading to the World of Resonant Communication,” NTT TechnicalReview, Vol. 1, No. 1, pp. 6-17, 2003.
Y. Inoue, “Achieving “Resonance of Knowledge”—NTT’s R&D
strategy to provide the basis for its envisaged resonant communications,” ibid., Vol. 1, No. 1, pp. 18-25, 2003.
Y. Yoshida and H. Takeuchi, “Applied Information Security Technologies,” NTT REVIEW, Vol. 15, No. 1, pp. 15-20, 2003.
Kazuhiro Nagayama
Producer, Resonant Network Project.
He received the B.S. degree in electrical engineering from Keio University, Kanagawa in1980. After joining NTT in 1980, he engaged inresearch and development on switching services,
satellite communication systems, and advanced
intelligent network systems. He is now studying
the next-generation broadband network. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE), theInformation Society of Japan (IPSJ), IEEE, and
the Association for Computing Machinery(ACM).

Takashi Hanazawa
Chief Producer, Resonant Network Project.
He received the B.E. and M.E. degrees fromWaseda University, Tokyo in 1974 and 1976,
respectively. Since joining NTT in 1976, he has
been engaged in research and development on
digital network structure, data transmission
equipment, processor systems for switching systems, and advanced intelligent network systems.
He became the Director of NTT Service Integration Laboratories last July and is responsible for
the RENA project. He is a senior member ofIEEE and chairman of the Network System technical committee of IEICE.

Nobuyuki Watanabe
Producer, Resonant Network Project.
He received the B.S. degree in electrical engineering from Chiba University, Chiba in 1982.
Since joining NTT in 1982, he has been engaged
in research and development on digital switchingsystems, switching services, and call agent systems. He is a member of IEEE and IEICE.

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