R&D Spirits
Innovating the Future Backbone Network throughIP + Optical Technology
Kohei Shiomoto
Senior Research Engineer, Supervisor,
Group Leader, IP Optical Networking Group
Broadband Network Systems Project
NTT Network Service Systems Laboratories

NTT Network Service Systems Laboratories is researching and developing “IP + optical”
technology, which integrates IP (Internet protocol) and optical layers, as the core technology forinnovating the future backbone network. How will IP + optical technology change the way that
networks operate, and what will it mean for society? We put these questions to Senior ResearchEngineer Kohei Shiomoto, the leader of the IP Optical Networking Group.

Achieving advanced network operations
through “IP + optical” technology—Dr. Shiomoto, what is your current R&D theme?

cal transport node, which operates at ultrahigh speed
by eliminating electrical processing of packets.
Examples of core nodes include reconfigurable optical add/drop multiplexers (ROADMs) and opticalcross connects (OXCs). The border and core nodes
are controlled by a common control plane called gen-The research group that I am currently leading is
working on “IP + optical” network
technology. Up to now, the optical• IP+optical MLN consists of border and core nodes.
network and IP (Internet protocol)- Border node: IP router
network have been managed sepa- Core node: optical transport node system (ROADM, OXC, etc.)• Optical label switched path (OLSP) is used to carry traffic.
rately, but we are integrating them in• Client network (e.g., IP/MPLS) network may be provided on top of MLN.
the form of an IP + optical multilayer network (MLN), as shown in Fig.
1. The idea here is to introduce a
IP optical TE server
server-based traffic engineering (TE)approach into a multilayer network
consisting of IP and optical layers. In
other words, the IP optical TE server
controls both the IP and optical layers and optimizes all the network
Client network
resources in both the IP and opticallayers. This new network consists ofclient and server networks. The servBorder nodeer network provides the optical layer
Server network
Core node
except for electrical IP packet forwarding at border nodes. A coreFig. 1. IP optical multilayer network (MLN).
node of the server network is an opti6

NTT Technical Review

R&D Spirits

eralized multiprotocol label switching (GMPLS) in
the server network. The client network is an IP network with or without MPLS, which provides various
network services. Part of the client network is instantiated by using the resources provisioned in the server network. The IP optical TE server controls network
resources in both the IP and optical layers so that the
IP + optical MLN can be used as a common network
for providing various client networks such as an
IP/MPLS network. In short, the ultimate goal of ourresearch is to innovate the future backbone networkby introducing advanced and intelligent network
operations offered by the IP optical TE server.
—What are the main technical features of this R&D
work?
One would be constraint-based route computation.
Routes must be computed to satisfy various constraints expressed as functions of cost, loss, delay,reliability, etc. Constraints could be complex and different for different networks. This task should be performed on a carrier-side server rather than at vendorprovided network nodes. Another feature is the ability to reconfigure the network topology dynamically,called virtual network topology (VNT) control (Fig.
2). Conventionally, a network topology is created inadvance on the basis of traffic-demand forecasts.
However, this makes it difficult to adapt to abruptchanges in traffic demand in the network. Suchabrupt changes in traffic demand could be triggeredby the unpredictable emergence of heavy traffic

sources and by failures caused by unexpected natural
disaster or network equipment malfunctions. In thesystem that we have developed, the network topology
can be reconfigured as needed by creating and/or
deleting optical paths.
By the way, enabling carriers to differentiate theirservices by server-based control implies the use of astandard interface between nodes and server (Fig. 3).
We have been very active in standardization activities
for this interface [1], [2]. I would like to describe
these activities in more detail later, but let me say herethat we have been submitting specifications to standardization bodies in cooperation with major carriersand vendors in the USA and Europe. My colleagues
and I have written a book on GMPLS technologies[3] to evangelize these new technologies.
—How will this technology contribute to NTT andsociety?
Integrating what used to be separate layers opens
up new possibilities in network services and has thepotential to reduce network operation costs. The latter is especially important in terms of maintaining
service quality. This relates to the much discussed“2007 problem,” which refers to the expected shortfall in Japan’s workforce as the generation that has
been supporting society up to now enters retirement
en masse. The world of information-communications
is no exception, and the forecast calls for a rapid
decrease in the number of engineers for network
operations and maintenance. Our aim is to help solve• Multilayer path sets up/releases control.
- Unified control of IP and optical layers- Virtual network topology (VNT) control• Manual control triggered by operators• Automatic control triggered by traffic change, topology change, failures

P2P,
P
2P
P, V
P,
Video,
iddeo, Voice,
Vo ce
ce …

IP optical TE server

P2P: peer-to-peer

VNT1

VNT2

Fig. 2. IP optical multilayer traffic engineering.

Vol. 4 No. 12 Dec. 2006

7

R&D Spirits• IP optical TE server- Multilayer TE algorithm based on carrier’s traffic control policy is implemented.
• Standard interface- Interface between IP optical TE server and network elements (IP routers,opticaltransport node system) is being standardized in IETF’s pce Working Group.

TE algorithmalgalgorith
lgoritiththmthBasic TE algorithm

Standard interface
TE algorithm

Network element

IP optical
TE server

Carrier’s policy isimplemented(multilayer, QoS,
reliability, etc.).

Network element
QoS: quality of service

Fig. 3. Server-based approach.

this problem by integrating the network.
Furthermore, by replacing the traditional telephone
network that we have been using for about 100 years
with an IP + optical network, we should be able to do
things never even thought of in the past. The communications network, which is now becoming a truesocial infrastructure, will not merely affect the way
we communicate. It is, of course, expected to givebirth to new business models and advance educationand medical care, but it should also help establish
government countermeasures to natural disasters bymaking the network even more robust. I believe that
we are going to face hard-to-manage changes in traffic demand as those new services emerge.
—What problems are you currently facing?
Though we have a good outlook for the future interms of technology, a big problem for us now is how
we can successfully introduce new technology in realbusiness situations. This is very difficult to do in general, and especially difficult in the case of backbone
network technology. People often believe that newtechnology is risky until it has been proven to be safe
after considerable practical use. They are naturally
afraid of it and therefore reluctant to introduce it. To
overcome such misgivings we need to prove that the
new technology is safe by using it in real business situations. It is a kind of chicken-and-egg problem inwhich the question of which comes first is continuously being argued. The infrastructure and applications should not be treated as a chicken-and-egg
problem. Rather, they should be developed in a mutually cooperative way. They should also be discussed
8

not just in terms of R&D, but also in terms of technology management. We need to find innovators
and/or early adoptors for the new technology we havedeveloped. In order to meet innovators and potential
early adopters, we need a watering hole where people
with different business backgrounds get together. In
nature, all kinds of animals gather together to drink
from the same watering hole. It is this kind of facility
that I believe we should also create for the world oftechnology. I have been working on IP + optical technology extensively from the technical viewpoint. But
I think that we need to work more extensively fromthe viewpoint of technology management. I think wemust serve as a contact point between the infrastructure and applications by creating a mechanism for
incubating and promoting services that make full useof IP + optical technology.
—How do you think IP + optical technology willdevelop from here on?
I believe that technologies like GMPLS that aretreated as future core technologies must still undergo
some improvements taking into account actual operating scenarios. At this stage, nobody can tell how
these technologies will look like at the time of implementation, but I think that the need to increase thespeed, capacity, and reliability of the network willcontinue to be demanded from here on. For this reason, I believe that IP + optical technology will
become all the more important in the years to comeand that it will become a core technology for highcapacity, high-speed networks within a matter ofyears.
NTT Technical Review

R&D Spirits

Working to deploy and spread IP + opticaltechnology through academic andinternational standardization activities—What is the worldwide trend in this research?
Academic research in this field is quite active in theUSA, but testbeds are being constructed and actual
GMPLS operations are being performed in Japan andEurope. Discussions are also progressing at the Internet Engineering Task Force (IETF), an international
standardization conference, with participation byleading carriers such as NTT, AT&T, and France
Telecom and global vendors such as Nortel, Cisco,and Juniper. And last year, NTT hosted the International Conference on IP + Optical Network (iPOP),an international gathering that promotes IP + optical
network technology. This conference does not simply
hold discussions on technology—it also provides aforum for carriers and vendors to perform interconnectivity experiments and public demonstrations. In
this sense, it also has the important role of a showcase
for technology and is attracting much attention as acontact point between academia and industry. The
iPOP conference has so far been held twice in Tokyo.
It is hoped that iPOP will come to function as thewatering hole for IP + optical network technology.
The iPOP is mainly organized by a Japanese organization called the Photonic Internet Laboratory(PIL) [2]. This consortium was formed by NTT andleading Japanese information-equipment makers topromote international standards for IP + optical network technology originating in Japan.
—How is NTT perceived in this field on the worldstage?
My feeling is that NTT, with many technologicalachievements in the field, is highly regarded. For
example, Layer-1 VPN (virtual private network),
which is now a common term in standardization
activities, was originally NTT technology. NTT
strongly influenced the inauguration of two of the
IETF’s working groups, l1vpn (layer 1 VPNs) andpce (path computation element). I served as a cochair on iPOP’s Technical Program Committee tomake iPOP a big success. Conference participantsfrom many countries gave NTT high marks for driving the latest trends in IP + optical network technology.

Vol. 4 No. 12 Dec. 2006

—Are you now involved in any collaborative projects
with other companies or research institutions?
As I have explained, we are now promoting the ideathat node equipment should be standardized and thatserver-based technology should be the means of differentiating a carrier’s services. For this reason, we
will strengthen the cooperation and ties with vendors
and other carriers. We are also collaborating withacademia in leading-edge technologies.

In pursuit of highly original technology thatcan make far-reaching contributions tosociety—Dr. Shiomoto, what was your motivation for entering NTT Laboratories?
In graduate school, I majored in information engineering and evaluated the performance of ATM(asynchronous transfer mode) switches and tokenring LANs (local area networks). I was therefore specializing in the field of communications from the very
start, and it was only natural that I would see NTT, thedominant institution in network research in Japan, as
the place to work. In 1989, when I entered the company, ATM was regarded as the way to go for the
coming era of multimedia communications, andATM research was quite active at NTT. I also had avery strong interest in ATM, and I very much wanted
to continue ATM research here at NTT.
—Could you give us a brief history of your R&D
activities to date?
I was first assigned to the ATM-switching-node
research group, where I was involved in the development of ATM switching system architecture designs.
Our research team successfully developed the world’s
first ATM switching system. This assignment wasexactly what I wanted, and from 1989 to 1995, I was
engaged in R&D of ATM traffic control and ATM
switching systems, my specialty. During that period,
I become involved in all of the processes related to
ATM switches, from the study of specifications totheir development, testing, and implementation.
Those switches came to be deployed in important
NTT networks and academic networks.
Then, in 1996, I joined Washington University in
St. Louis, Missouri, as a visiting researcher for one
year. At that time, the trend in network research was“IP over ATM,” and the problem was to find ways of9

R&D Spirits

controlling IP traffic on an ATM network. As part ofthis trend, I also researched IP with ATM at the core,and eventually I came to the realization that network
control would come to be performed by IP. On returning to Japan, I immediately advised my superior of
my desire to take up IP research even though our
research group still devoted itself to ATM technology.
As you may easily imagine, it is very difficult tochange the R&D strategy in a big company like NTT.
But I never gave up my desire to change it. I discussedwith him over and over again until I was finally able
to begin IP research, though on my own. That was in1997. Then, after about a year of preparations, I
developed an IP + ATM-node system based on ATM
switches. It was just around that time that a rapid shift
toward IP began to take place around the world, and
NTT R&D also began the conversion to IP. My R&D
work likewise expanded to include IP routers andmulti-service network nodes, and I worked on thoseIP themes until 2001. During that time, my R&D target shifted to IP + optical technology, and here I am
now.
—Looking back, is there any one incident that you
would regard as a turning point?
Yes. During the time that I was in the USA, I participated in a workshop on IP over ATM. There wasmuch heated discussion on the IP-over-ATM scheme,
and one researcher in particular stated that “everything can be done by IP, so ATM is not really necessary.” That was Stephen Deering, who has made aname for himself in IP multicast research. At first, I
had no idea what he was talking about, but on doingsome self study, I came to understand that thisapproach could help increase network capacity significantly, and I gradually learned how such an IP
system could be achieved. While ATM is capable ofvery detailed control, IP has plenty of horsepower. In
terms of pure research, ATM is a very interesting subject, but when it comes to high-speed and largecapacity systems, which the world demands, I’ve
come to think that IP is the better choice. That, I
would say, was my turning point. Since winning thebattle against ATM, IP has become sophisticated withhelp from MPLS technology. This is a typical example of how technology evolves. The technical viewpoint is not the only important one; the businessviewpoint also matters.

10—What has been your goal throughout your R&D
activities?
More than anything else, I want to be useful to society. And I want to create things that never existed
before. I want to come up with technology that people describe as “this is something new,” or technology that no one has even thought of before, and thenprovide that technology to the world by incorporating
it into the communications infrastructure. It is withthis feeling that I undertake R&D. Of course, one wayof pursuing R&D is to concentrate on only those
things that you find interesting without regard totrends or needs in society. I, myself, however, feelthat the meaning of R&D work is to create things that
not only possess originality but that are also useful topeople in society. This is why I entered NTT. From
here on as well, with a perspective that I could have
only at NTT, I would like to do work that has greatsocial impact beyond what is possible from the viewpoint of a single company.

Aiming for better application of R&D results
as a contact point between infrastructureand services—What direction would you personally like to takefrom here on?
Creating an advanced infrastructure will not, in
itself, give birth to new things. And, of course, thereverse is also true. I believe one’s attention must be
turned to both the infrastructure and services if one is
to make contributions to society through communications technology. Accordingly, while continuing topromote R&D in the IP + optical MLN, I would liketo channel much of my energy into creating a forum
where network researchers and application developers can gather freely and hold open discussions.
And as another future direction, I would like to pursue development work from a wider perspective. In thedevelopment process, it is often found that a certain
technology, if available, would make a great difference, but alas, for one reason or another, it cannot be
obtained. This is more of a problem of methodology
than creativity. But it should be possible to minimize
this problem if good advice on development methods
and appropriate technology-related information were
to be provided and if industry and academia were tocollaborate and produce results in an appropriate way.
The picture I’m painting here is of development consulting, which I am very interested in. Making use of
NTT Technical Review

R&D Spirits

my extensive experience in development work and in
the administration of international conferences, I think
it would be very interesting to become a catalyst forthe matchmaking of technologies.

challenge other opinions if necessary. Otherwise,
new and novel things will not be created. By allmeans, have conviction as a researcher and be readyto refute the opinions of even your superiors.

—What is your ultimate dream as an engineer?
My first and foremost desire is to contribute to society through the R&D of communications technologies. This may sound rather simplistic, but I would
like to be involved in creating communication services that people are happy to use and really find necessary.
—What is it like working at NTT Laboratories for you
personally?
NTT is a leading carrier in the world, and the quality and size of its R&D program are world-class.
Though it is a private enterprise, its influence on society is great, and the technologies researched anddeveloped there are used by NTT communication
businesses to bring genuine changes to the world ofcommunications in Japan. Being a part of thisendeavor gives me a great feeling of worth. There arealso many excellent researchers at NTT Laboratories,
and the range of research fields is extensive, whichmakes it very easy for me to obtain information fromoutside my field of specialty. Being able to carry on
my research in such an environment is something that
I value greatly and appreciate very much.
—Dr. Shiomoto, what would you say to young
researchers?
More than anything else, I would say “have conviction.” From what I have seen in recent years, young
researchers need a more confident and independent
attitude. Young researchers should not be reluctant tovoice different opinions even against their superiors.
In order to maintain creativity, we must continue tohave active discussion. We need more debate to findthe truth. A former superior of mine once told me that
“If someone presents a particular idea, be sure to suggest modifications or alternatives. Even if you also
believe that the original idea is right, you should stillplay the devil’s advocate. It is only in this way that thetruth can come out.” Perhaps that is an extreme example, but I also favor this kind of interplay in discussions. Of course, I’m not saying that it’s good to takean opposing stance no matter what the issue. The
important thing here is that one has the confidence toVol. 4 No. 12 Dec. 2006

References
[1]
[2]

[3]

K. Shiomoto, “Overview of GMPLS Protocols and Standardization,”
NTT Technical Review, Vol. 2, No. 6, pp. 76-80, 2004.
A. Misawa, K. Shiomoto, S. Okamoto, and N. Yamanaka, “Promotionof Next-generation Photonic Network Protocol Standardization by
Photonic Internet Lab (PIL),” NTT Technical Review, Vol. 2, No. 2,
pp. 85-88, 2004.
N. Yamanaka, K. Shiomoto, and E. Oki, “GMPLS Technologies:
Broadband Backbone Networks and Systems,” Marcel Dekker, Inc.
2005.

Interviewee profile■ Career highlights
Kohei Shiomoto received the B.E., M.E., and Ph.D.
degrees in information and computer sciences from
Osaka University, Osaka, in 1987, 1989, and 1998,
respectively. He joined NTT in April 1989 andengaged in R&D of ATM traffic control and ATM
switching system architecture design. From August
1996 to September 1997, he was engaged in researchon high-speed networking as a Visiting Scholar at
Washington University in St. Louis, MO, USA. From
September 1997 to June 2001, he was directing architecture design for the high-speed IP/MPLS label
switching router research project at NTT Network Service Systems Laboratories. Since July 2001, he has
been engaged in the research fields of photonic IP
router design and routing algorithms and in GMPLS
routing and signaling standardization, first at NTT
Network Innovation Laboratories and then at NTT
Network Service Systems Laboratories. He is active in
GMPLS standardization in IETF. He is a member of
the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan, IEEE, and the
Association for Computing Machinery. He was the
Secretary for International Relations of the Communications Society of IEICE from June 2003 to May 2005.
He was the Vice Chair of Information Services of theIEEE ComSoc Asia Pacific Board from January 2004
to December 2005. He has been involved in the organization of several international conferences including
HPSR 2002, WTC 2002, HPSR 2004, WTC 2004,
MPLS 2004, iPOP 2005, MPLS 2005, iPOP 2006, and
MPLS 2006. He received the Young Engineer Award
from IEICE in 1995. He received the Switching System Research Award from IEICE in 1995 and 2000.
He was one of the authors of “GMPLS Technologies:
Broadband Backbone Networks and Systems”.

11