NTT Technical Review
August 2014 Vol. 12 No. 8
Feature Articles: Technological Development
for Network Virtualization
Current Status of Development of Network Virtualization Technologies
Service Function Chaining Technology for Future Networks
Network Virtualization Technology for Implementing Future Networks
Ryu SDN Framework—Open-source SDN Platform Software
Fundamental Research Activities on Network Virtualization

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Feature Articles: Technological Development for
Network Virtualization

Current Status of Development of
Network Virtualization Technologies
Hidehiro Arimitsu, Kimihide Matsumoto,Yasunori Matsubayashi, Masao Aihara,
Yasuo Makibayashi, Hisashi Kojima, and Tomoya Kosugi
Abstract

NTT laboratories have been active in researching and developing network virtualization technology as
a key technology of future networks, which will be next-generation carrier networks. In this article, weoutline the carrier network architecture, focusing specifically on the network virtualization technology
implemented in it. We also introduce the research on elemental technologies being conducted by NTT
laboratories.
Keywords: network virtualization, NFV, SDN

1. Introduction
The increased performance of general-purpose
servers and the technological advancements in software have accelerated the deployment of virtualization technologies in datacenters. Network virtualization technology, in which such information technology advancements apply to carrier networks, hasbeen the focus of a lot of attention recently and is
expected to improve the scalability and reliability ofcarrier networks at low cost. Here, we introduce the
network virtualization technology applied to thearchitecture of a future carrier network and also
describe its elemental technologies.
2. Network virtualization technology
Traditional carrier networks have been composedof many kinds of dedicated equipment, where each
network function is implemented in a different pieceof equipment. In contrast, the introduction of network
virtualization technology, in which control functions
and forwarding functions are distinctly separate, ischanging the existing network architecture (Fig. 1).
In the new architecture, intelligent control and service functions are implemented by software andaggregated in the cloud, while a forwarding network
is composed of simple hardware with a specialized
forwarding function. The development of two technologies—network functions virtualisation* (NFV)
and software-defined networking (SDN)—hasrecently been accelerated in order to structure thiskind of network architecture.
NFV is a technology in which network functions
that are conventionally implemented in dedicatedhardware are implemented by software on generalpurpose servers. Performance increases in generalpurpose servers and technological advances in virtualization technologies have led to NFV with carriergrade performance, scalability, and reliability. The
application of NFV to carrier networks is expected toenable high scalability and reliability at low cost, as
well as rapid service deployment, flexible resource
assignment according to the demand for each service,and service deployment without the EoL (end of life)
restrictions of hardware-based equipment. Additionally, because many different network functions areaggregated in general-purpose servers, reductions in
CAPEX (capital expenditures) and OPEX (operating*

The British spelling used by the European Telecommunications
Standards Institute

NTT Technical Review

Feature Articles

Intelligent control and service functions are implemented
by software and aggregated in the cloud.

Traditional network
Each piece of network equipment
has a specific network function.

Cloud
VirtualAppliance

MessagerouterDPI

Session bordercontroller

CDN

FirewallCarrier-grade
NAT

VirtualAppliance

VirtualAppliance

SGSN/GGSN

QoE monitor

NFV
Separation ofcontrol andforwarding functions

NetworkSDN
switchBRAS

Accessnode

BRAS: broadband remote access server
CDN: content delivery network
DPI: deep packet inspection
NAT: network address translation
PE: provider edge
QoE: quality of experience

VirtualAppliance

General-purpose servers

switchswitchWAN
accelerator

VirtualAppliance

Virtual machines

switchPE router

VirtualAppliance

switchswitchswitchGeneral-purpose
switchswitches

Forwarding network is composed of simple hardware
with a specialized forwarding function.
SGSN/GGSN: serving GPRS (general packet radio service) service node/
gateway GPRS service node
WAN: wide area network

Fig. 1. Network virtualization technology applied to future carrier network.

expenses), lower power consumption, and a reduced
equipment footprint are also expected. ETSI (European Telecommunications Standards Institute) has
played a leading role in studying NFV under an
Industry Specification Group. Participants frommany major carriers and equipment vendors from allover the world are actively focusing on NFV and arepushing the work forward.
SDN consists of technology to control and manage
network equipment in a centralized fashion by meansof software techniques. Applying SDN to carrier networks makes it possible to separate control and forwarding functions, which have been implemented ina single piece of equipment until now, and to aggregate control functions in a cloud. Network carriers
expect to reduce OPEX drastically and to provide
consumers and service providers with flexible network services through the use of SDN’s centralized
control and management features. Major elemental
technologies applied to realize SDN include OpenFlow, which was standardized by ONF (Open Networking Foundation), and I2RS (Interface to the
Routing System), standardized by IETF (The Internet
Engineering Task Force).

Vol. 12 No. 8 Aug. 2014

3. Network architecture in virtualization era
3.1 Future networks
NTT laboratories have been actively researchingand developing future networks, which will be nextgeneration carrier networks. As in the past, future
networks are expected to offer steady communication
services as a vital social infrastructure. These include
fixed consumer services such as Internet access andvoice services, mobile services such as mobile voice
and broadband services, and enterprise services suchas virtual private networks and wide-area LAN (local
area network) services. Such future networks are also
required to have the capability to offer new services
rapidly and flexibly in order to meet diversified
needs. Furthermore, these networks will have somemechanisms developers can use to create brand newservices in cooperation with service providers. Froma carrier viewpoint, operating and managing a network that can become increasingly complicated andsophisticated is a critical issue. NFV and SDN are
expected to be key technologies to build the future
networks, which must meet various demands andneeds. Next, we outline the architecture of thesefuture networks and describe the network virtualization technologies used in them.
Feature Articles

Service providers
Logical network forservice provider A(network slice)

Logical network forservice provider B(network slice)

1. Network-function-offering
technology for service providers• Provides service providers with
network functions and resourcesof future networks

Northbound API
2. Integrated control technology
Integrated control• Assigns computing and network
resources in response tovariations in demand

Carrier cloud
NW NW NW
func. func. func.
A
B
C
VM

VM

Big data
analysis

Orchestrator
VM
NW
controller

VM

General-purpose servers• Controls and automatesconfigurations of network
equipment

VM

3. Carrier cloud technology

VM• Offers computing resources tovirtualized network functions
with carrier-grade scalability
and reliability

Southbound API

4. Forwarding network technology
switchswitchswitchswitchswitchForwarding network

General-purpose
switches

API: application programming interface
NW: network
VM: virtual machine• Builds a forwarding network
using simple and low-cost
network equipment with a
specialized forwarding function• Southbound API technology
controls network equipmentfrom a network controller

Fig. 3. N etwork virtualization technology
for future networks.

Fig. 2. Structure of future networks.

3.2 N
 etwork virtualization technologies in future
networks
Future networks are composed of two hierarchicalstructures—a forwarding network and a carrier
cloud—and are connected to service providers thatcan offer network services using the future networks’
resources (Fig. 2). There are four key network virtualization technologies that compose the future networks, as follows (Fig. 3).
(1)	Network-function-offering technology for service providers
This technology provides service providers with
network functions and resources owned by the future
networks. For instance, a service provider can easily
create its own network service by combining its own
application with a logical network offered by thefuture networks. We can use SDN technologies tobuild a logical network.
(2) Integrated control technology
This technology manages and controls both computing resources and network resources. Computing
resources are deployed in a carrier cloud as generalpurpose servers, whereas network resources are
deployed as network equipment. Integrated control
technology consists of an orchestrator, which manages the assignment of resources throughout the network, and a network controller, which controls the
network equipment. The orchestrator reassigns
resources in response to variations in the demand foreach service and resource requests from service providers. The network controller controls a forwarding
network composed of general-purpose switches upon
NTT Technical Review

Feature Articles

request from the orchestrator. The interface and protocol specifications between a network controller anda piece of network equipment is referred to as asouthbound API (application programming interface). OpenFlow is one of the most popular southbound API protocols. Additionally, work is proceeding
to advance network operation using big data. For
instance, the network controller manages a network
based on big data analysis of traffic variations inorder to improve QoE (quality of experience) at low
cost.
(3) Carrier cloud technology
This technology offers computing resources to virtualized network functions with carrier-grade scalability and reliability. It is a fundamental technologythat enables various carrier network functions to be
implemented as NFV. It is expected to achieve rapid
and efficient development of services and improved
tolerance for traffic variations. Furthermore, it canbuild a disaster-resistant network which, for instance,
concentrates network resources on the most basic
communication services—such as voice services—asa lifeline in the event of a large-scale disaster.
(4) Forwarding network technology
This technology builds a forwarding network using
simple and low-cost network equipment with a specialized forwarding function. Extracting intelligent
control and service functions from traditional routers
and transport systems to be virtualized and implemented by a software application as a network controller enables network equipment to be specialized
to provide a forwarding function. Carriers expect thistrend to result in the commoditization of network
equipment and low-cost procurement. Additionally, it
can lead to a reduction in the amount of network
equipment needed since SDN technology can integrate multiple network devices used for each layer
into a single device. For instance, traditional routersand layer-2 switches might be integrated into a single
general-purpose switch. In the NFV environment
where a lot of network functions are accommodated
in a single physical server, virtual switches are also
necessary in order to forward packets to an appropriate virtual machine. High-performance virtual
switches are required in a carrier network in order toprevent bottlenecks in the forwarding performance.

4. Research and development of elemental
technologies for network virtualization
The network virtualization technologies for future
networks cover a very broad range of application
areas. NTT laboratories are broadly promoting
research and development of the elemental technologies that compose network virtualization technology.
We introduce some of these concrete efforts in these
Feature Articles.
In the article “Service Function Chaining Technology for Future Networks,” we introduce a service
function chaining technology as one of the networkfunction-offering technologies for service providers[1]. In the article “Network Virtualization Technology
for Implementing Future Networks,” we introduce anorchestration technology as an example of integrated
control technology, a server platform technology as
an example of carrier cloud technology, and a centralized control technology for transport networks as an
example of forwarding network technology [2]. In
the article “Ryu SDN Framework—Open-source
SDN Platform Software,” we introduce an SDN controller technology (Ryu SDN Framework), which isan essential technology for controlling a virtualized
network [3]. Finally, in the article “Fundamental
Research Activities on Network Virtualization,” weintroduce an SDN software switch (Lagopus), which
is a core technology for packet forwarding on top ofgeneral-purpose servers and switches and a substantive
industry-academia-government experimental collaboration to deploy an end-to-end virtual network on a
research network [4].
References
[1]

[2]

[3]

[4]

Vol. 12 No. 8 Aug. 2014

H. Kitada, H. Kojima, N. Takaya, and M. Aihara, “Service Function
Chaining Technology for Future Networks,” NTT Technical Review,Vol. 12, No. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa2.html
A. Shibata, H. Onishi, M. Miyasaka, and T. Hamano, “Network Virtualization Technology for Implementing Future Networks,” NTT
Technical Review, Vol. 12, No. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa3.html
R. Kubo, T. Fujita, Y. Agawa, and H. Suzuki, “Ryu SDN Framework—Open-source SDN Platform Software,” NTT Technical
Review, Vol. 12, No. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa4.html
K. Obana, K. Yamada, Y. Nakajima, H. Masutani, K. Shimano, and M.
Fukui, “Fundamental Research Activities on Network Virtualization,”
NTT Technical Review, Vol. 12, No. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa5.html

Feature Articles

Hidehiro Arimitsu

Senior Research Engineer, Network Architecture Project, NTT Network Technology Laboratories.
He received the B.E. in nuclear engineeringfrom Nagoya University, in 1997. He joined NTT
in 1997 and engaged in network planning at NTT
Plant Department. From 2004 to 2007, he wasengaged in developing IP network architecture of
the FLET’S HIKARI Premium at the R&D Center of NTT WEST. Currently, he is researching
the architecture of future networks at NTT Network Technology Laboratories.

Kimihide Matsumoto

Hisashi Kojima

Executive Manager, Network Technology
Project, NTT Network Technology Laboratories.
He received the B.S. and M.S. from Nagoya
Institute of Technology in 1988 and 1990,
respectively. He joined NTT in 1990 and engaged
in research on QoS management and traffic engineering in telecommunications networks. From1999 to 2005, he was involved in developing
systems for IP-based services at the R&D Centerof NTT EAST. Currently, he is primarily working on the architecture of future telecommunications networks. He is a member of IEICE ofJapan.

Yasunori Matsubayashi

Senior Research Engineer, Supervisor, Network Architecture Project, NTT Network Technology Laboratories.
He received the B.E. in electronic communication engineering from Meiji University, Tokyo, in
1987. He joined NTT in 1987 and engaged indeveloping business phone systems in NTT Customer Equipment Division. From 1994 to 1998,
he was engaged in investigating overseas
advanced technology at NTT America, Inc. From1999 to 2012, he worked on the development of
the FLET’S HIKARI service at the Service
Development Division of NTT EAST. Currently,
he studies the architecture of future networks at
NTT Network Technology Laboratories.

Masao Aihara

Senior Research Engineer, Supervisor, Network Technology Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in electronic
communication engineering from Waseda University, Tokyo, in 1989 and 1991, respectively. In
1991, he joined NTT Network Service Systems
Laboratories and studied ATM switching software technologies and carrier-grade IP networkarchitecture. During 2000–2011, he was engaged
in developing the FLET’S HIKARI service at the
R&D Center of NTT EAST. Since then, he has
been studying the architecture of future networks
at NTT Network Technology Laboratories. He isa member of IEICE of Japan.

Yasuo Makibayashi

Senior Research Engineer, Supervisor, Network Architecture Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in informationand communication engineering from Waseda
University, Tokyo, in 1987 and 1989, respectively. In 1989, he joined NTT Switching Systems
Laboratories and studied packet switching systems and network architecture including X.25
and FR technologies. He also studied and developed the Next Generation Network (NGN). He isa member of the Institute of Electronics, Information and Communication Engineers (IEICE)of Japan.

Senior Research Engineer, Network Technology Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in informationand communication engineering from Waseda
University, Tokyo, in 1997 and 1999, respectively. In 1999, he joined NTT Network Service
Systems Laboratories and studied IP/Optical
network architecture including MPLS and
GMPLS technologies. During 2006–2008, hewas engaged in developing IP network architecture of NGN, especially in IP routing design.
After that, he studied FMC (fixed and mobile
convergence) network architecture at NTT Service Integration Laboratories (now NTT Network Technology Laboratories). His current
study interests include network virtualization
technologies such as SDN and NFV, and network
security. He is a member of IEICE of Japan. He
received the Young Engineer Award from IEICE
in 2005.

Tomoya Kosugi

Researcher, Network Architecture Project,
NTT Network Technology Laboratories.
He received the B.S. in applied physics andphysico-informatics and the M.S. in integrated
design engineering from Keio University, Tokyo,
in 2008 and 2010, respectively. In 2010, hejoined NTT Access Network Service Systems
Laboratories and studied access network architecture of future networks. His current study
interests include network virtualization technologies such as SDN and NFV. He is a member of
IEICE of Japan.

NTT Technical Review

Feature Articles: Technological Development for
Network Virtualization

Service Function Chaining
Technology for Future Networks
Hiroyuki Kitada, Hisashi Kojima, Naoki Takaya,
and Masao Aihara
Abstract

Service function chaining enables various network functions to be used rapidly and flexibly. This
article describes methods of implementing service function chaining technology and also presents use
cases.
Keywords: SDN, NFV, service function chaining

1. Introduction

2. Service function chaining use caseAs the development of network functions virtualisation* (NFV) technology continues in the future,
network functions will become concentrated in datacenters and will be operated as a cloud service. This
will make it easier to implement new network functions and will enable network function resources tobe allocated flexibly on request and according to
demand. We expect that NFV will lead to moreadvanced carrier networks. For example, network
functions have conventionally been deployed in the
network using dedicated equipment. This means thatwhen services are added or software is updated,
modifications must be made to every piece of equipment (Fig 1(a)). In contrast, network functions arecentralized in the cloud when NFV is used to virtualize network functions (Fig. 1(b)). This makes it possible to change or add network functions simply by
updating the software on commercial-off-the-shelf(COTS) servers.
However, concentrating network functionality inthe cloud means that user packets must be sent
through the COTS servers in the cloud, where the
network functions are located. Also, if individual
users contract different services, each user uses different network functions, and consequently, routing
per user or flow is required. The technology to control
packet routing through the applicable network functions is called service function chaining technology.

We consider the example of a content service provider (CSP) that provides a service to end users
through a carrier network as a use case for service
function chaining technology (Fig. 2). In the current
network, the CSP must purchase, install, and configure customer-premises equipment (CPE) to connect
to the carrier network as well as to other equipment
such as a firewall to ensure security. However, withservice function chaining technology, functions suchas the CPE and firewall can be implemented in software and set on a carrier cloud, and the carrier canoffer them as network services. As a result, the CSP
can contract network services easily and immediately,
simply by clicking a button on the service contract
website. Thus, even if the CSP is under attack, it
could immediately contract for security services anddefend itself against the attack.



3. Service function chaining system
Some challenges arise in implementing service
function chaining with existing Internet protocol (IP)
network technology. Generally, when carrier andother large-scale networks use IP routing, routing is
implemented based on aggregated network addresses*

The British spelling used by the European Telecommunications
Standards Institute (ETSI)NTT Technical Review

Feature Articles

Networkfunction A
VirtualAppliance

Cloud
Network functions are
deployed on the network
using dedicated equipment.

User A

User B

VirtualAppliance

Networkfunction B
VirtualAppliance

External
network

External
network

User A

Carrier network

Networkfunction B: Switch: COTS
serverCloud
Traffic is selectivelytransferred to a specificnetwork function in the cloud.

Networkfunction A
Networkfunction A

VirtualAppliance

Carrier network
User B(a) Current network(b) Future network using virtualization technology

COTS: commercial-off-the-shelf server

Fig. 1. Routing required when network functions are virtualized on the cloud.

FirewallCPE

Cut off attacks.

VirtualAppliance

Cloud

CSP
Video delivery
serverConfiguration

Network
controller

Server administrator

Attacker
Configuration
Carrier network

Able to contract for
security services,even if attacked

User
Able to watch video smoothly
Firewall contract

CSP: content service provider
CPE: customer-premises equipment

Fig. 2. Use case for CSP.

to increase scalability. However, if user-based routing
as in the previously described use case is implemented with IP routing, the network equipment must learnrouting tables that contain a huge number of IP
routes. This is impractical in terms of scalability.
Therefore, a new routing method was necessary thatwas independent of the existing IP routing.
NTT Network Technology Laboratories has proposed a packet-labeling method to implement service
Vol. 12 No. 8 Aug. 2014

function chaining technology. In this method, switches in the carrier network attach labels to each packet
to identify network functions that the packets must
pass through (Fig. 3). If a packet passes through multiple network functions, multiple labels are attached,
and the order they must pass through the functions isindicated. Within the carrier network, routing is
implemented according to the labels attached to apacket. A feature of this method is that informationFeature Articles

Network function(virtual machine)
Cloud

Virtual switch checks labels andforwards packets to appropriate
network functions (virtual machines).

COTS server

SwitchCOTS server

SwitchVirtual switch

PacketLabels indicating
network functions

Carrier network
In carrier networks, packets arerouted to next network function
based on stacking labels.

Switch adds labels to packets.

Fig. 3. Service function chaining system.

about service function chaining is attached to thepackets themselves. Even as the user contract status
dynamically changes, the control is only needed forthe switches, so the method is highly scalable.
4. Prototype demonstration
To demonstrate service function chaining, we built
a prototype using actual equipment based on themethod described in the previous section (Fig. 4).
The service function chaining prototype consists ofswitches, COTS servers handling the network functions, and a network controller. A service contract site
was also prepared, enabling users to easily add orcancel services.
When a user subscribes to a service on the site, theinformation is passed to the network controller, and aflow entry on the switch is configured using thesouthbound API (application programming interface). The network controller consists of an application and a switch controller. The application computes the labels to be attached to packets using information about subscribers and network functions in
the cloud. The switch controller receives the information on the labels from the application and generates
flow entries to control the switches. In our prototype
implementation, the controller and application were
implemented on a platform called the Ryu SDN
Framework, which was developed by the NTT Software Innovation Center.
Also, to apply the service function chaining on
existing IP networks by adding minimal functionality, we used an overlay connection method in the
prototype. IP tunneling is used to connect switches in
the carrier network and virtual switches on the COTS
servers. Packets with labels are transmitted throughIP tunnels, so label processing is hidden from the core
network, which minimizes the amount of equipment
necessary for processing labels.
This environment enabled us to demonstrate that
services can be provided to users more rapidly andwith greater flexibility through use of service function chaining technology.
5. Issues
Various issues must be addressed in order to apply
service function chaining on a real carrier network.
We describe some of the issues that were identified inbuilding the prototype described above.
5.1 Ensuring interoperability
There are currently no standard methods or protocol technologies for implementing service function
chaining, so we developed original methods and usedthem to implement the prototype. This meant thatexisting network functions such as virtual appliances
could not process the labels. Therefore, the virtual
switches running on our COTS servers first removed
the labels before packets were sent to the network
NTT Technical Review

Feature Articles

CPE

Firewall: Virtual switch

VirtualAppliance: IP tunnel

Cloud
CSP
Video
distribution
serverIP Network
Network
controller

SwitchSouthbound API

Serveradministrator

Ryu
App

SwitchSouthbound API

User
App: application
Ryu: Ryu SDN (software-defined networking) Framework

Service contract site

Fig. 4. Prototype implementation example.

function and then re-attached them after they returned
from the network function. This implementation
enabled us to use existing virtual appliances as-is,
although we sacrificed some transmission performance due to the processes of attaching and removing labels. Fully introducing service function chaining on a carrier network would require securing theinteroperability by standardizing the service function
chaining technology, and making sure that virtual
appliances from various companies support the protocols.
5.2 Ensuring scalability
An environment that fully incorporates NFV on acarrier network, where many network functions are
running on COTS servers, would require many ofthese servers in order to process large amounts of traffic. Specifically, we assume that many servers would
be operating for a virtual machine implementing asingle network function. To implement service function chaining under such conditions, the labels would
need to indicate not only the type of network function
but also the virtual machine running the network
function. Thus, in addition to multiple users, multiple
virtual machines would need to be identified on the
carrier network. As such, a method of implementing
this processing without losing scalability is needed.

5.3 Improving the control plane system
An important factor with large-scale networks suchas carrier networks is how information such as subscriber information and service function chaininglabels will be managed in order to control the networkand provide fine-grained services. In the method
described above, subscriber and label information is
managed centrally by the network controller andattached to packets in the form of labels, so servers in
the cloud do not maintain any individual subscriber
information. In this way, when a subscriber changes
contract conditions, network function changes can bepropagated quickly by simply changing the labels
attached when packets enter the network, and without
controlling the cloud at all.
However, the network controller has all of the information, so network controller performance and reliability are very important. It would not be feasible fora single network controller to manage and control alarge-scale carrier network. Therefore, redundancy inthe network controller—through scaling out or using
distributed processing—must be considered. In theseways, the control-plane architecture will also need to
be improved to satisfy the requirements of a carrier
network.
6. Future prospects
Service function chaining is an important technology

Vol. 12 No. 8 Aug. 2014



Feature Articles

for future networks that can provide new services
rapidly and with flexibility. However, it is currently
still a concept-level technology, and various issues
such as protocol standardization need to be resolved
before it will be practical. Standardization of methods
and protocols for implementing service function
chaining are currently in progress by the Service
Function Chaining Working Group of the Internet

Hiroyuki Kitada

Researcher, Network Architecture Project,
NTT Network Technology Laboratories.
He received the B.E. and M.S. in engineeringfrom Shibaura Institute of Technology, Saitama,in 2008 and 2010, respectively. He joined NTT
Service Integration Laboratories in 2010 andstudied energy efficient network architecture. He
is currently studying network virtualization technology such as SDN and NFV at NTT Network
Technology Laboratories. He is a member of theInstitute of Electronics, Information and Communication Engineers (IEICE) of Japan.

Hisashi Kojima

Senior Research Engineer, Network Technology Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in informationand communication engineering from Waseda
University, Tokyo, in 1997 and 1999, respectively. In 1999, he joined NTT Network Service
Systems Laboratories and studied IP/Optical
network architecture including MPLS (MultiProtocol Label Switching) and GMPLS (Generalized Multi-Protocol Label Switching) technologies. During 2006–2008, he was engaged indeveloping IP network architecture of NGN(Next Generation Network), especially in IP
routing design. After that, he studied fixed andmobile convergence (FMC) network architecture
at NTT Service Integration Laboratories (nowNTT Network Technology Laboratories). His
current interests include network virtualization
technologies such as SDN and NFV, and network
security. He is a member of IEICE of Japan. He
received the Young Engineer Award from IEICE
in 2005.

Engineering Task Force. At the NTT Network Technology Laboratories, we are working toward achieving a scalable technology that can be applied to acarrier network based on the knowledge gained fromthe methods introduced here and the prototype wehave built. We are also working on related standardization activities.

Naoki Takaya

Senior Research Engineer, Supervisor, Network Architecture Project, NTT Network Technology Laboratories.
He joined NTT Network Service Systems
Laboratories in 1995 and studied xDSL, highspeed ATM switching systems, and call agent
systems for VoIP service. During 2003–2010, he
studied ubiquitous network services, IP Multimedia Subsystem, and service delivery platform
application architecture on FMC network environments at NTT Service Integration Laboratories. Since 2012, he has been studying network
virtualization technologies such as NFV andSDN at NTT Network Technology Laboratories.
He is a member of IEICE of Japan. He received
the IEEE IMSAA award in 2010.

Masao Aihara

Senior Research Engineer, Supervisor, Network Technology Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in electronic
communication engineering from Waseda University, Tokyo, in 1989 and 1991, respectively. In
1991, he joined NTT Network Service Systems
Laboratories and studied ATM switching software technologies and carrier-grade IP networkarchitecture. During 2000–2011, he was engaged
in developing the FLET’S HIKARI service at the
R&D Center of NTT EAST. Since then, he has
been studying the architecture of future networks
at NTT Network Technology Laboratories. He isa member of IEICE of Japan.

NTT Technical Review

Feature Articles: Technological Development for
Network Virtualization

Network Virtualization Technology
for Implementing Future Networks
Akira Shibata, Hiroyuki Onishi, Masahiro Miyasaka,
and Takafumi Hamano
Abstract

NTT Network Service Systems Laboratories has been applying network virtualization technologies
such as NFV (network functions virtualisation) and SDN (software-defined networking) as part ofefforts to develop the architecture of future networks that are efficient, flexible, and intelligent. This
article gives an overview of these efforts.
Keywords: orchestration, open innovation, transport network simplification

1. Introduction
Anticipation has been increasing recently for theapplication of network virtualization technologies
such as network functions virtualisation* (NFV) andsoftware-defined networking (SDN) in carrier networks. NTT laboratories have been carrying out
research and development (R&D) aiming to achieve
innovations in network structures and development
schemes by applying virtualization technologies. The
objectives are to: (1) centralize service and management functions in the cloud; (2) simplify transport
equipment and integrate layer processing; (3) use
orchestration functions to automate operations andreduce operations expenses (OPEX); and (4) promote
open innovation with global cooperation among carriers and vendors, as shown in Fig. 1.
NTT Network Service Systems Laboratories has
been conducting R&D focused on implementing thearchitecture of future networks based on these technology trends. We introduce three such initiatives inthis article. The first is to implement orchestration
functionality to handle virtual networks; the second isto establish new server platform technologies throughco-innovation and promotion of open innovation; andthe third is to develop centralized transport network
control technology to simplify transport networks.

2. Operations suitable for network
virtualization
With virtualized networks, equipment design canbe carried out for all resources, rather than for individual, dedicated hardware, so reductions in designand construction work can be expected througheconomies of scale. Also, general-purpose standby
servers can be allocated flexibly to the services experiencing faults, so it is no longer necessary to havestandby equipment for each type of dedicated hardware, and there are fewer faults that require urgent
attention. In these ways, network virtualization canlead to reductions in OPEX (Fig. 2).
We have been studying ways to automate virtual
network operations (adding equipment, initiating
fault recovery, etc.) more than ever before using
orchestration functionality. Specifically, we havebeen examining functions that detect when set thresholds are exceeded and automatically add resources,
functions that detect faults and automatically recoverfrom them, and other functions. We aim to achieve
dramatic reductions in OPEX through the following
orchestration technologies (Fig. 3).

*



The British spelling used by the European Telecommunications
Standards Institute

NTT Technical Review

Feature Articles

Centralize service and management
functions in the cloud.
• Improve both efficiency and reliability.
• Use technologies that can meet carrier
requirements (scalability etc.).
• Deploy functionality according toenterprise maintenance model.
Simplify transport network and minimize
types and number of devices.
• Simplify transport equipment
functionality, minimize on-site
maintenance.
• Integrate multi-layer processing
equipment.

Network
cloud

Integrated control
Orchestrator

Network Network Network
function function function
A
B
C

VM

VM

VM

General-purpose
IA servers

General-purpose
switch/routerUse orchestration
functionality to automate
operations and reduce OPEX.
• Expand automation andremote maintenance.
• Achieve integrated control forservices and layers.

Big data
analysis

VM

VM

Network
controller
VM

General-purpose
switch/router

Promote open innovation(co-innovation).
• Achieve modularization andinterface standardization.
• Speed up development andreduce costs via cooperation
based on core technologies
of laboratories.
• Avoid lock-in with specificvendors.

General-purpose
switch/router

Transport network

General-purpose
switch/router

General-purpose
switch/router

IA: Intel Architecture
VM: virtual machine

Fig. 1. Innovations of network architecture and development schemes with virtualization technologies.

(a) Equipment design(Current network)
Dedicated Dedicated DedicateddevicedevicedeviceABC(b) Fault recovery(Current network)

Equipment expansion is neededfor each service.
Traffic A

Traffic B

Traffic C

Partial operation is implemented
due to fault in active system;
maintenance is required.

Active Standby Active Standby Active Standby
Fault(Virtual network)

Provisioning is done using total
resources; expansion is required
less often.
Traffic A+B+C

App App App
A
BC(Virtual network)

Standby servers can be allocatedflexibly to recover from faults,
so a sudden rush of faults canalso be handled.

App App App App
A
B
C
A
Fault

Partial operation

Standby servers(shared for applications A, B, and C)
App: application

Fig. 2. Reducing OPEX with virtual networks.

2.1 Optimized resource allocation technology
When general-purpose servers are allocated inorder to add resources or enable fault recovery, theVol. 12 No. 8 Aug. 2014

resources used on each server must be equalized, andresources must be allocated according to service
requirements (reliability, delay, etc.). Our goal is toFeature Articles(a) Optimized resource allocation technology(b) Fault source inference technology

Allocation according to service
requirements (reliability, delay, etc.)

Achieving prompt fault recovery
based on cause of fault

Standby

ActiveRemote(VM error case)Fault recovery on same
server (reboot)Active Standby
Load

Appli- balApplication
cation ancer
Guest OSVM VM
Virtual network
vSwitchHypervisor
HV
Host OSOS
Server hardware Server 1

Physical network

Application

Loadbalancer

ActiveActiveVM VM VM error
vSwitch(Server hardware fault case)
HV
Fault recovery on differentOS
server (reboot)HardwareServer 2
fault
Router/Switch
ActiveActive: Applications requiring active and standby servers
to be separate for reliability requirements etc.
: Applications requiring low fluctuation in delay(between application and user) between active
and standby servers
OS: operating system

Fig. 3. Technical elements of orchestration functionality.

establish optimized resource allocation technologythat makes it possible to set and control multiple
policies related to allocation, including (1) selecting
servers in geographically separate locations whenallocating active and standby servers for services
requiring reliability and (2) selecting servers by location so that any network delay that occurs is equivalent between active and standby servers (for applications that are affected by delay).
2.2 Fault source inference technology
Virtual networks are implemented using multiple
layers (virtual servers, physical servers, virtual networks, physical networks), which makes administering the configuration and determining the state ofequipment rather complex. The goal of fault source
inference technology is to infer the location of a fault
when a fault occurs by combining alarms and otherinformation from each layer, and to use it to speed up
fault recovery.
3. Server platform technologies supporting
service provision
A lot of research has been done recently on virtualization of network functions using NFV, including
software implementations of service application
functionality on communication networks. Here, we
describe initiatives to implement new server architectures that will enable rapid provision of such serviceapplications.
Conventionally, communication network advances
have been driven by developments in hardware,
switching, and data processing technology. Software
has been developed and communication services provided that satisfy quality and reliability requirements
over a diversity of network devices. Consequently,
selecting hardware and middleware for each network
device, achieving reliability and extensibility withservice applications on each device, developing service applications, and building equipment and maintenance systems have consumed an enormous amountof time. As the services provided on communication
networks become more diverse, and as network functions are increasingly implemented in software on
future networks, we expect that the types and numbers of network devices will increase further, andincreasing numbers of service applications will be
developed, so it is important to resolve this issue.
NTT Network Service Systems Laboratories has
proposed new server architecture as a common distributed processing platform. This architecture maximizes the common components of communication
network functionality and is designed to be built
using only the required number of general-purpose
hardware devices by using virtualization technologies, and to realize the reliability, extensibility, andoperability cultivated by communication providers
and their partner companies (Fig. 4). By using thisarchitecture, network operators and service providers
NTT Technical Review

Feature Articles(a) Conventional server architecture

Networkfunction X
Application
X

Application
Y
Platform

High-reliability
hardwareHigh-reliability
hardwareHigh-reliability
hardwareHigh-reliability
hardwareStandby Active: Functionality for reliability: Functionality for extensibility

Networkfunction X

Networkfunction Y

Networkfunction Z

Networkfunction Z

Application
X

Application
Y

Application
Z

Application
Z

Common server platform to optimize reliability,
scalability, and operability for each service
requirement (core technology)
VM VM VM
VM VM VM
VM VM VM

Networkfunction Y

Platform

Active(b) Future server architecture

Platform
High-reliability
hardwareGeneral-purpose
hardwareGeneral-purpose
hardwareGeneral-purpose
hardwareGeneral-purpose
hardwareOrchestration

General-purpose hardware

StandbyFig. 4. Proposed server architecture.

can focus on the functional logic of their service
applications and implement them on the network
quickly and efficiently.
NTT laboratories and our partner companies havecooperated from the conceptual stages in order torealize this server architecture. We have utilized ourrespective strengths and promoted co-innovation
through collaborative research (Fig. 5). In this collaborative research, we aim to refine technologies for
distributed processing, virtualization, and maintenance and operations from multi-faceted perspectivesof the three corporations, and to create technology
through synergistic effects. NTT laboratories are providing the distributed processing technology (theengine component) related to carrier server requirements, scale-out capabilities, and redundant configurations. This technology enables system performance
to be increased in proportion to the number of general-purpose servers comprising the system. It also
distributes load appropriately across multiple servers
and controls the backup servers that load is assigned
to when hardware faults occur. Our partner companies are providing system requirements based on
global markets, server virtualization technology,
orchestration technology, the distributed processing
system technology (the core software development
capabilities), and maintenance and operations technology.
In this way, we aim to establish new server architectures that will enable service applications to be develVol. 12 No. 8 Aug. 2014

oped quickly and to develop technologies that will
provide support in fields beyond future communications networks (such as finance and medicine) that
require the results of this research: reliability, extensibility, and operability. By advancing the level ofsophistication, we also aim to promote these technologies globally and to create global standards.
4. Centralized transport control technology tosimplify transport networks
The capacity of transport networks must continually be increased in order to handle the communication traffic that increases each year, mainly due toInternet traffic. A major issue for telecommunications
carriers in such conditions is the need to achieve dramatic reductions in transport network equipment andmaintenance costs. Telecommunications carriertransport networks generally build a transport layerusing technologies such as Internet protocol (IP) and
Ethernet for flexible transport; that layer is on top ofa transmission layer that economically handles longdistance transport through the use of high-capacity
optical-wavelength or packet-transport paths. To substantially reduce costs in transport networks, it isimportant to simplify them by re-examining theimplementation of functionality within the transport
and transmission layers.
Next, we describe centralized transport control
technology, which can reduce equipment costs whenFeature Articles

Rapid creation of innovative
network server technology

Create new technology
through synergy.
Check feasibility promptly.

Virtualization
Distributed processing
technology
technology
NTT core technology
Co-Innovation
Maintenance andoperations technology
Multi-faceted
technology refinement

Global developmentof NTT technology
Alcatel-Lucent Japan• Global-market-based
system requirements• Server virtualizationand orchestration
technologies for carriers

Fujitsu• Distributed processing
system technology(core softwaredevelopment)• Maintenance andoperations technology
for scale-out communication
control server

NTT• Carrier requirements
for servers• Core distributed
processing technology(engine components)
for scale-out andredundant configurations

Fig. 5. Co-innovation initiatives.

Network
maintainer/
operator

Transport network
controller

Control of both the
IP/Ethernet transport layer
and the transmission
layer is concentrated in
the controller.

Node configuration interface

Transport network

IP/Ethernet
transport node
Transmission nodeFig. 6. Transport network architecture applying centralized transport control.

used in combination with another technique such as
substituting high-capacity optical transmission nodes
for transport nodes or integrating transmission andtransport layer equipment.
A transport network architecture that uses centralized transport control is shown in Fig. 6. A transport
network controller (controller) is placed on the transport network, and the control of the IP and Ethernet
transport layer and the transmission layer is central

ized in this controller. Centralized transport control
technology is a network virtualization technologythat separates the control plane and the data plane forthe transmission and transport layers, which facilitates control that spans these layers. There are two
objectives in using this technology:(1)	Reducing operational costs by providing a single interface for maintenance and operations of
the transmission and transport layers.
NTT Technical Review

Feature Articles

Transport network
controller (prototype)Link1
2
Real-time trafficmonitoring

7
8
0 20 40 60 80 100
Link utilization [%]Alarm for exceeding
traffic volume criteria
Traffic balancing byrerouting

Link1
2

Route optimization
application
Transport network
control platform
Ryu

7
Node configuration
8
0 20 40 60 80 100 interface
Link utilization [%] (OpenFlow)• Controls IP routing in the transport network• Configures routes for IP transport nodes• Exchanges IP routing with external IP
networks
IP routing protocol(only for external IP networks)

External IP network

Transport network

IP transport node(OpenFlow switch)
Transmission node

Ryu: Ryu SDN Framework

Fig. 7. Network architecture used in concept demonstration.

(2)	Reducing the maintenance time and operationalcosts required to update functionality of transport and transmission layer transport network
control (path and bandwidth control, etc.) when
extending service layer functionality.
NTT Network Service Systems Laboratories has
prototyped a controller that controls IP routes centrally without using the IP routing protocols that
perform distributed IP route control autonomously
between routers. This prototype was designed inorder to evaluate the feasibility of applying centralized transport control technology to the IP layer. This
prototype uses the Ryu SDN Framework [1] open
source software developed by NTT laboratories. It
implements an architecture that enables various addon functionalities to be flexibly combined on a common platform that performs basic IP route control
functions. A demonstration of the concept using thisprototype was given at the NTT R&D Forum 2014,
held in February 2014. The configuration for the concept demonstration is shown in Fig. 7. The prototype

Vol. 12 No. 8 Aug. 2014

demonstrated the feasibility of centralized IP routecontrol by combining controls to reroute faulty links
and select optimized routes in order to equalize traffic
volumes based on real traffic measurements.
5. Future developments
In this article, we have introduced some of our virtualization technology initiatives at NTT Network
Service Systems Laboratories. We will continue todevelop and actively promote various technologies
for implementing the architectures of future networks.
Reference[1]

R. Kubo, T. Fujita, Y. Agawa, and H. Suzuki, “Ryu SDN Framework—Open-source SDN Platform Software,” NTT Technical
Review, Vol. 12, No. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa4.html

Feature Articles

Akira Shibata

Masahiro Miyasaka

Hiroyuki Onishi

Takafumi Hamano

Senior Research Engineer, Supervisor, Network Systems Planning & Innovation Project,
NTT Network Service Systems Laboratories.
He received the B.E. and M.E. in electricalengineering from Waseda University, Tokyo, in1991 and 1993, respectively. In 1993, he joined
NTT Communication Switching Laboratories.
Since then, he has been engaged in R&D of network service systems. He is currently engaged in
implementing network virtualization technology
and the architecture of future networks. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE) of
Japan.

Senior Research Engineer, Operation Innovation Project, NTT Network Service Systems
Laboratories.
He received the B.E. and M.E. in mechanicalengineering from Waseda University, Tokyo, in
1996 and 1998, respectively. In 1998, he joined
NTT and studied next-generation IP mobile network architecture. His current research interests
include management and operation architecture
for NFV.



Senior Research Engineer, Server Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. in materials
physics and engineering from Osaka University,
in 1996 and 1998, respectively. In 1998, hejoined NTT Network Service Systems Laboratories. His current research interests include NFVthat allows network systems to share server
resources. He is now engaged in R&D of a network system in which resources are dynamicallyallocated.

Senior Research Engineer, Transport Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. in engineeringfrom Kyoto University in 1994 and 1996, respectively. He joined NTT in 1996 and studied IPVPN edge router systems. His current researchinterests include next-generation transport network architecture and systems. He is a memberof IEICE of Japan.

NTT Technical Review

Feature Articles: Technological Development for
Network Virtualization

Ryu SDN Framework—
Open-source SDN Platform Software
Rui Kubo, Tomonori Fujita, Yuji Agawa,and Hikaru Suzuki
Abstract

We introduce Ryu SDN Framework, an open source software (OSS) system developed by NTT, anddescribe our efforts toward promoting its wider adoption. Ryu SDN Framework is a platform that provides tools and libraries for easy use of SDN (software-defined networking). We have taken advantageof the strengths of OSS in developing Ryu, which conforms to the most recent industry-driven OpenFlow
specifications. Ryu is used by a variety of experts including SDN application developers, network device
developers, and network service maintainers.
Keywords: SDN, OpenFlow, open source software

1. Introduction

2. Ryu SDN Framework

Server virtualization and cloud computing technologies have created an unprecedented need for
network adaptability, expandability, and flexibility.
An approach to solving those problems that has been
attracting attention is SDN (software-defined networking), which enables configuration of networks
and the programming of network functions by operating software [1].
The network configuration function is divided into
a data plane for handling data transfers and a control
plane for handling control of the data plane. In theconventional approach, the two planes are tightly
linked within individual network devices, so interworking between the control planes of the devices isnecessary when constructing a single network withmultiple network devices.
In the SDN approach, on the other hand, the data
plane and control plane are separated, and their independence is maintained by specifying an application
programming interface (API). Using the API todevelop programs according to purpose and use
enables higher independence of data plane control. A
program that uses this kind of API is called an SDN
application.

Ryu SDN Framework (Ryu) is a framework thatprovides the libraries and tools that are required inorder to develop SDN applications (Fig. 1 and Fig. 2).
The framework facilitates development by providing
the basic functions for controlling the data plane andthe functions that are common to SDN applications.
The functions that are features of Ryu are describedin the following subsections.



2.1 OpenFlow controller function
OpenFlow is a set of API specifications for the control plane and the data plane formulated by the OpenNetworking Foundation (ONF); it has been attracting
broad attention as the most important API specifications for implementing the SDN approach. OpenFlow
switch is the term used for the data plane that conforms to the specifications, and OpenFlow controller
similarly refers to the control plane. SDN applications can be implemented by using these functions.
Ryu has the OpenFlow controller function, so SDN
applications that use OpenFlow switches can easily
be developed using Ryu. Although various versionsof the OpenFlow API specifications exist, Ryu iscompatible with a greater variety of versions thanother OpenFlow controllers (versions 1.0, 1.2, 1.3,
NTT Technical Review

Feature Articles

SDN application
Create and manage a network required
for a business or service with little effort.

Ryu SDN Framework
Platform software provides convenient andadvanced functions and hides complex processing.

API
OpenFlow switch

Existing network
deviceFig. 1. Overview of Ryu SDN Framework.

(1) Bundle function
Ryu

Bundledsettings set
together at
one time

Fig. 2. Ryu public site (http://osrg.github.io/ryu/).

(2) Eviction function
Ryu(3) Optical port informationcollection function
Ryu

Eviction priority
for memory
overflow

Optical port
information

Fig. 3. Functions of OpenFlow version 1.4.

and 1.4), so more OpenFlow switches can be used.
The functions of the most recent version, 1.4, which
was released in the fall of 2013, are explained as follows and presented in Fig. 3.
(1)	Bundle function: This function is for setting
multiple commands for an OpenFlow switch at
the same time. In the previous versions, it wasnecessary to confirm the setting of each command individually on the application side. This
bundle function facilitates development by making it possible to set multiple commands together as a bundle.
(2)	Eviction function: This function enables processing to be done when memory overflow
occurs in OpenFlow switches. The memory
capacity for storing the switch settings can varywith the type of machine. In the previous versions, it was necessary to implement the required
Vol. 12 No. 8 Aug. 2014

processing on the application side for each typeof machine in order to prevent memory overflow. This eviction function facilitates development of applications through automatic selection of the eviction command based on the priorities set by the application.
(3)	Optical port information collection function:
This enables OpenFlow switches to have 10Gbit/s or 40-Gbit/s broadband optical ports inthe same way as other network devices. Withprevious versions, it was not possible to obtainthe signal wavelength and strength or otherinformation that is specific to optical ports, andit was necessary to use special functions outside
the OpenFlow specifications for specific device
types to obtain such information. OpenFlow
switches that work with this function can obtain
the information that is specific to an optical portFeature Articles

in the same way as for an ordinary Ethernet port,
reducing the machine-specific implementation
required in application development.
2.2 F unctions for cooperating with existing network devices
It has been difficult to replace all of the network
devices in an existing network with new OpenFlow
switches. An OpenFlow switch can transmit various
types of data in the same way as the existing network
devices, so it is also possible to construct a networkin which the devices of the existing network co-exist
with OpenFlow switches. For example, when expanding an existing network or dealing with devices thathave complex management settings, a practical
approach would be to partially and gradually introduce OpenFlow switches by using an SDN application. Ryu provides functions for such introductions of
OpenFlow switches in an existing network.
2.2.1 Obtaining management information
Even in existing networks, it is generally common
to collect data such as the amount of traffic flow, linkstatus, and other kinds of information from network
devices that are compatible with SNMP (Simple Network Management Protocol), NetFlow, sFlow, etc.,
via network management systems, monitoring systems, or other such means, and to perform total, overall management of the data. The same kinds of information concerning OpenFlow switches can also becollected by the OpenFlow controller function. Ryu
provides a function for collecting information fromconventional network devices as well as from OpenFlow devices to avoid splitting the management system into two systems when a network configuration
includes both OpenFlow switches and conventional
network devices. Using Ryu to develop the management system makes it possible to collect information
on various network devices other than OpenFlow
switches and to perform total, integrated management. When the existing system is taken as the parent
system, the functions of the Ryu OpenFlow controller
can be called from the existing system so that information collection and total management that includes
OpenFlow switches can be performed.
2.2.2 Settings
Some users use provisioning tools for implementing automatic changes in network device ports andbandwidth settings, for example, and also for entering
settings. The NETCONF (Network Configuration
Protocol) specifications are intended to provide acommon procedure for such tasks for conventional
network devices.


ONF is also addressing the issue of a common procedure for entering settings, which is not covered by
OpenFlow specifications, by establishing the OFCONFIG (OpenFlow Management and Configuration
Protocol) specifications. Ryu accommodates both
OF-CONFIG and NETCONF in the switch settings
management function, so it is also possible to develop
provisioning tools for unified settings changes for
OpenFlow switches and existing network devices.
The Ryu OF-CONFIG function can also be calledfrom existing provisioning tools.
2.2.3 Exchange of routing data
The exchange of routing information based on the
Border Gateway Protocol (BGP) is often used foroverall cooperative operation of existing network
devices as a single network. For example, data can be
efficiently transferred by synchronizing the routing
information possessed by network devices in different locations. Because Ryu conforms to the BGP
specifications, it is possible, for example, to receive
the routing information that is exchanged among
existing network devices and send that data to OpenFlow switches. Also, changes made to routing information on the OpenFlow switch side can be sent toexisting network devices via Ryu. Thus, when OpenFlow switches coexist with an existing network, routing information can be synchronized by the samemechanism as used previously, and obstacles to theintroduction of OpenFlow switches can be reduced.
2.3 Sample applications
Ryu mainly provides tools and libraries that facilitate SDN application development, but sample applications that are easily referenced are also included.
The examples include applications that implement
firewalls and routers of the kinds that are familiar to
most of us as well as applications that implement
functions that are often used when constructing networks, such as link aggregation and spanning trees.
3. Efforts to achieve widespread adoption
In addition to developing Ryu, the NTT laboratories are actively encouraging the wider use of thisplatform. By making Ryu known and available tomany people and obtaining feedback on it that can beused to develop an even better platform, we hope tocontribute to the overall development of SDN/OpenFlow.
3.1 OSS development
Ryu is open source software (OSS). The source
NTT Technical Review

Feature Articles

Fig. 4. T est results for the OpenFlow switch (http://osrg.
github.io/ryu/certification.html).

Fig. 5. E -book reference for Ryu (http://osrg.github.io/ryu/
resources.html#books).

code is published and can be downloaded and usedfreely under an Apache license [2]. Anyone can incorporate Ryu into their products, commercial or otherwise, and some products that incorporate Ryu arealready on the market [3]. The platform was published in 2012, and development has been vigorous
ever since, with participation by switch vendors, network providers, systems integrators, academic organizations, and various others.

basic characteristics of various OpenFlow switchesby browsing the published results.
This tool is also provided together with Ryu and isbeing used by many switch developers. Using thistool from the beginning of switch development canraise the level of product conformance with thespecifications and aid in product quality management.

3.2 Wider use of OpenFlow specifications
The OpenFlow specifications do not necessarily
define all functions as essential, and there are somefunctions whose application depends on the switch.
There are also cases in which specific conditions
must be satisfied for proper operation, even when
conformance to OpenFlow specifications has beenachieved. Currently, specific development may beneeded for each particular switch because of ambiguities in the OpenFlow specifications themselves.
We are taking advantage of the high degree of Ryu
conformity to the OpenFlow controller function
specifications to develop a tool for checking thedegree of conformance to OpenFlow switch specifications. We are using that tool to test the connection
to various OpenFlow switches and are publishing theresults on the Ryu website [4] (Fig. 4). Those who aredeveloping SDN applications can understand theVol. 12 No. 8 Aug. 2014

3.3 Documentation and publications
Although there was little documentation right after
Ryu was published as OSS, more and more documentation is being made available. Currently, an e-bookthat compiles that documentation is being distributed(Fig. 5). Like the software, the book is also in open
development, so interested persons are welcome toaccess it from any handy terminal.
References
[1]

[2]
[3]
[4]

Y. Nakajima, “Standardization Progress in Software Defined Networking/OpenFlow,” NTT Technical Review, Vol. 11, No. 2, 2013.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2013
02gls.html
Ryu public website, http://osrg.github.io/ryu/
Introduction examples of Ryu, http://osrg.github.io/ryu-book/en/
html/introduction_example.html
Test results for the OpenFlow switch, http://osrg.github.io/ryu/certification.html

Feature Articles

Rui Kubo

Senior Research Engineer, Supervisor,
Advanced Information Processing Technology
SE Project, NTT Software Innovation Center.
He received the B.S. and M.S. in electricalengineering from Keio University, Tokyo, in1990 and 1992, respectively. In 1992, he joined
the NTT Network Information Systems Laboratories. During 2006–2013, he was engaged incommercial development of the Next Generation
Network (NGN). He is a member of the Instituteof Electronics, Information and Communication
Engineers (IEICE).

Tomonori Fujita

Hikaru Suzuki

Senior Research Engineer, Distributed Computing Technology Project, NTT Software Innovation Center.
He received the B.E. and M.E. from Waseda
University, Tokyo, in 1998 and 2000, respectively. He has been with NTT since 2000 and has
been engaged in research on operating systems.
He is a member of IPSJ (Information Processing
Society of Japan) and ACM (Association for
Computing Machinery).

Yuji Agawa

Manager, Smart Navigation Business Division,
NTT Resonant Inc.
He received the M.S. in electro-communications from the University of Electro-Communications, Tokyo, in 2003. He joined NTT in 2003.
As of July 1, 2014, he moved to NTT Resonant
Inc. His research interests include distributed
computing and software-defined networking. He
is a member of the Japanese Society for Artificial
Intelligence.

Vice President, Head of NTT Software Innovation Center.
He received the M.E. in industrial and management system engineering from Waseda University, Tokyo, in 1988. In April 1988, he joined
NTT Switching System Laboratory. In 2009, hemoved to NTT Communications and in 2012, hemoved to NTT Software Innovation Center. He
served as vice-chair of the IEICE TechnicalCommittee on Information Networks from May
2008 to May 2010, and as the chair from May
2010 to May 2012. He has contributed to thedevelopment of a range of network services suchas PHS, 3G-mobile, Free-Phone, and NGN. His
research interests include information network
services and operations. He is a senior member of
IEICE and a member of IEEE (Institute of Electrical and Electronics Engineers).

NTT Technical Review

Feature Articles: Technological Development for
Network Virtualization

Fundamental Research Activities on
Network Virtualization
Kazuaki Obana, Kazuhisa Yamada, Yoshihiro Nakajima,
Hitoshi Masutani, Katsuhiro Shimano,and Masaki Fukui
Abstract

NTT Network Innovation Laboratories has been conducting a great deal of research in the areas of
network virtualization and software-defined networking (SDN). In this article, we describe Lagopus, ahigh-performance OpenFlow 1.3 capable SDN software switch from the O3 Project. We also briefly
explain our research activities involving network virtualization.
Keywords: NFV, SDN, OpenFlow

1. Introduction
One requirement in building future networks or
next-generation networks is to construct a virtualized
network in which its QoS (quality of service), performance, and functions are adaptable to each user’s
needs. Thus, technology for expanding the applicablearea of fine flow control via software-defined networking (SDN) and technology for adapting the
deployment, correction, and removal of high-performance and highly functional software by means suchas network functions virtualisation (NFV) *1, arebecoming increasingly important. In this article, we
introduce NTT Network Innovation Laboratories’
research activities on SDN and network virtualization.
2. O3 Project: automating the configuration of
network nodes
We aim to establish network virtualization technology that enables many network operators and service
providers who share network resources to design andbuild networks and to manage network operations fortheir own purposes. This will enable network operators to reduce the time needed to design, build, andmodify their networks to only about 10% of the time

previously required over a wide area network. As aresult, service providers will be able to dramaticallyreduce the time required to initiate and withdraw services. Moreover, user satisfaction is expected toincrease as users gain faster access to their desired
services.
This project is known as the O3 (O Three) Project*2(Fig. 1) and is based on research on network virtualization technology consigned via the Ministry ofInternal Affairs and Communications. It is being
jointly promoted by five companies.
This project aims to verify and commercialize
research and development (R&D) results throughprototypes and verification testing of network virtualization technology. At the same time, the project also
aims to share and standardize research results globally, making some of the results open to the public
and providing them to domestic and overseas*1	 The British spelling used by the European Telecommunications
Standards Institute*2 O3 stands for the overall concepts of this project: open, organic,and optima. In June 2013, five companies (NEC Corporation,
Nippon Telegraph and Telephone Corporation, NTT Communications Corporation, Fujitsu Limited, and Hitachi, Ltd.) began
working jointly on R&D to conduct verification tests. The fivecompanies aim to verify and commercialize these technologies
and will promote the sharing and standardization of the research
results globally.

NTT Technical Review

Feature Articles

Object-oriented virtual network operating platform(1) Develop network management and control platform software.
(2) Develop network design, construction, and operation management software.
(3) Develop virtualization-compatible network devices.
Orchestration/OSS, BSS

(2)

(1)

(3)

Internet

Network design, construction, and operation management software
Design tool

Construction tool

Operation management tool

Network management and control platform software
Overlay system

Packet/Optical system

Wireless system

Virtualization-compatible network devices

Legacy carrier
network

NetworkFig. 1. Overview of O3 project.

telecommunications carriers and service providers
and vendors. An outline of the target R&D areas inthis project is as follows:(1)	Technology for developing network management and control platform softwareThis technology is used to develop SDN platform
software that enables the construction of networks
while meeting service requirements and enabling fast
provision of services. Specifically, it integrates awide area network by ensuring common handling of
information to control diverse networks such as optical, wireless, and packet communication networks(network configuration information, communication
status information, etc.), and enables development ofplatforms for flexibly and promptly performing control functions.
(2)	Technology for developing software for network
design, construction, and operation management
This technology is used to develop software for
network design, construction, and operation management that runs on the platform mentioned in item (1).
Specifically, it is used to develop design software (toverify designed networks) that is necessary in order
to apply SDN to a wide area network, construction
software (to interconnect with existing networks andtransition from existing networks to SDN), andoperation management software (to identify faults
between layers and respond to them faster and tocontrol service quality).
Vol. 12 No. 8 Aug. 2014(3)	Technology for developing virtualization-compatible network devices
This is used to develop SDN network devices thatcan be controlled by technologies outlined in (1) and(2). Specifically, it is used to develop the interfaces
and driver functions that enable use of low-cost, highperformance resources through all layers, optimization of service construction costs, and control ofexisting optical, wireless, and packet transport network devices, as well as software communication
devices that can freely change configurations andfunctions.
NTT Network Innovation Laboratories is developing software communication devices that are compatible with SDN ((3) in the list above) and that consistof software programs on general-purpose server
hardware.
3. SDN software switch: Lagopus
The use of software-oriented network nodes on
general-purpose servers is important in order to simplify transfer networks and reduce their cost. These
nodes are now more common than hardware-oriented
network nodes for this purpose. NTT Network Innovation Laboratories successfully launched a prototype high-performance SDN software switch called
Lagopus as part of the O3 project. Although SDN has
already been introduced in corporate networks suchFeature Articles

Performance
Hardware is superior to software.

Existing SDN
hardwareswitchesCorerouter

Ideal area in which performanceand flexibility are balanced

Edge router
GW router
DPI, FW

Target area of
prototypeswitchExisting SDN software
switches
Flexibility
Software is superior to hardware.
DPI: deep packet inspection
FW: firewall
GW: gateway

Fig. 2. Flexibility and performance target of Lagopus switch.

as those at datacenters, this prototype SDN software
switch achieves high performance even when large
scale flow entries are set, and it functions as a technical element enabling application of SDN to wide area
networks such as those of telecommunications carriers and Internet providers [1].The target performanceand flexibility of this prototype switch are shown in
Fig. 2. In preparation for using this prototype switch
for NFV in the future, the switch was given a modular
architecture with remarkable expandability thatmakes it easy to expand and upgrade.
This prototype is compliant with long-term-support
OpenFlow 1.3, the SDN-enabling specification, andalso achieves good results in OpenFlow conformance
tests. Furthermore, the development and implementation of the Flexible parallel Flow processing Framework (fff: Fig. 3) makes high-performance packet
transfer possible with the prototype.
In general, a kernel space program is superior to auser space one in terms of processing speed. There
are a number of problems with kernel space programs, however, including the need for the program
to be maintained for the latest kernels. This prototype
is a user space program and is implemented in parallel, with multiple threads enabling sufficient performance to be achieved.
Problems with SDN software switches are solved
as follows:(1)	Faster forwarding with parallelization (multiple


threads enabled)
Flows are identified, and packets in a flow arehandled in a single set of pipelines to avoid orderreversal of packets. The sets of pipelines are parallelized and multi-threaded to achieve greater speed [1].
(2)	Faster searching of large scale flow entries withan ‘fff’ look-up algorithm
A novel algorithm has been developed in order tospeed up the process of looking up large scale flow
entries under complicated search conditions, such as
the don’t care tolerance usually used in SDN (OpenFlow) in each set of pipelines. The prototype achieves
high performance in searching flow tables, and theperformance does not decrease much even if large
scale flow entries are set into the flow tables. In addition, an fff look-up algorithm is implemented with ashigh a cache hit ratio as possible in order to reduce thenumber of times the memory needs to be accessed[1].
When 100K entries, which suffice as the first target,
are added to flow tables, and all packet headers are
rewritten, this prototype achieves 10-Gbit/s wire ratetransferring of large packets. This makes it one of thehighest performance SDN software switches ever.
We developed an agent function, which interprets
the OpenFlow control protocol from the SDN controller and controls our software switch, in collaboration
with the NTT Software Innovation Center, which hasdeveloped Ryu, as mentioned in one of the Feature
NTT Technical Review

Feature Articles

SDN software switch with Flexible parallel Flow processing Framework ( fff )Process/Transform protocols
API

Flow
identification

OpenFlow
communication
block

High functionality
block

Pipelined
processFlowlook-up

Config/ Management blockFundamental switch block (OpenFlow based)[Performance: 10 Gbit/s, 100K flows]

Network interface (GE, 10GE)

Network: Fundamental blocks: Extended blocks

API: application programming interface
GE: gigabit Ethernet

Fig. 3. SDN software switch with fff.

Articles in this issue [2]. In the O3 project, our prototype is connected via Ryu with SDN control platform
software.
The prototype will be extended to enable it to handle larger flow entries. R&D to achieve higher performance in applying software nodes to wide area networks will be promoted, as well as R&D for handlingnew protocols and management functions with highreliability in order to make software nodes more reliable and better operable.
4. Research to provide virtual networks toservice providers
A virtual technology that can provide functions of
future networks and network resources on a logicalnetwork is necessary for service providers. Network
virtualization technology, which is one of the technologies applied to achieve SDN and NFV, can divide
a physical network into multi-layered subnetworks.
In each subnetwork, a different transport control protocol can be used, and specific applications or services can also be assigned. This is a major advantagethat enables new services to be built quickly and flexibly on a carrier network.
We have taken part in developing the Network Platform for Flexibly-Programmable Advanced Service
Composition. This platform includes routers, switches, servers, and network processors. It was developed
Vol. 12 No. 8 Aug. 2014

during the period from fiscal year (FY) 2008 to
FY2010 in a joint research project launched by NICT
(National Institute of Information and Communication Technology), the University of Tokyo, NTT,
NEC, Hitachi, and Fujitsu Laboratories in order tostudy network technology after the NGN (next-generation network).
Since 2011, a new research project to promoteresearch on a next-generation virtual network platform has been executed under the Commissioned
Research of NICT. The same organizations are participating in this project, and KDDI Laboratories andother organizations have also joined it. In this project,
we have developed a virtual network platform consisting of a node system called VNode, which enables
connections with nodes in other networks, as well as
a network management system for the entire virtual
network platform. The basic components of the
VNode system are shown in Fig. 4.
Our VNode prototype system is shown in Fig. 5.
We conducted experimental trials on a testbed (Fig. 6)that is based on overlay networks on JGN-X (Japan
Gigabit Network-eXtreme), which is operated by
NICT. As part of efforts to realize a global virtual
network, we conducted experimental trials on interconnecting our platform with foreign virtual network
platforms. Some challenges arose in the trials
between the virtual network testbed on JGN-X and a
testbed on GENI (the Global Environment forFeature Articles

VNode Manager
Integrated control ofprogrammer andredirector

VNode manager

Programmer
Juniper

Programmer
Programmableprocessing
units for routing engine(VM, NPU, etc.)
Redirector
Slice A
Slice B

Redirector• Creates tunnels forvirtual links• Configures queues
and bandwidth

NPU: network processing unit
VM: virtual machine

Fig. 4. Basic components of VNode system.

VNode

Fig. 5. Prototype VNode system.

Network Innovation), which is promoted by the
National Science Foundation in the USA. Theirarchitecture and implementation are so different that
it was difficult to interconnect them. Furthermore,ordinary virtual network technology cannot guarantee QoS (the number of transmitted packets andlatency). Thus, it is difficult to provide high-quality
service. We installed our newly developed VNode at
the University of Utah, which is a research partner of

NICT, and we connected VNode to the ProtoGENI
testbed. We then carried out the world’s first successful trial to control multi-domain networks between
Japan and the USA.

NTT Technical Review

Feature Articles

slice 3

newSW
newSW

newSW

slice 2
vOFS

vOFS
vOFS

newSW
vOFS
vOFS

slice 1
vOFS

vOFS
vOFS

vOFS

SapporovOFS

Kanazawa
OkayamaInternational Circuit

Hiroshima
10 G

Korea
Fukuoka
VN

Example

VN

1G
10 G

NICT Koganei 10 G
10 G
10 G × 2
AGW
10 G
40 G × 2
40 G
40 G
Osaka
10 G
VN
VN
Nagoya10 G × 2

40 G
10 G
1G
DF

NC

NICT
Keihanna

Tokyo Area

VN

AGW

NC

Sendai

Wireless Testbed

Tokyo

VN
AGW
NICT
OtemachiVN
AGW AGW
NICT
HakusanInternational Circuit
USA Thailand Singapore Hong Kong
VN

: VNodeNC: Network Connector

AGW: AccessGateway

SW: switch
vOFS: virtual OpenFlow switch

Fig. 6. Testbed on JGN-X.

5. Future work
We will continue to promote the implementation ofmany kinds of applications on our testbed and to conduct experimental trials. We will also work to create
the environment that will encourage many users to
install our VNode system.

Vol. 12 No. 8 Aug. 2014

References[1][2]

NTT press release, http://www.ntt.co.jp/news2013/1312e/131209a.
html
R. Kubo, T. Fujita, Y. Agawa, and H. Suzuki, “Ryu SDN Framework—Open-source SDN Platform Software,” NTT Technical
Review, No. 12, Vol. 8, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
08fa4.html

Feature Articles

Kazuaki Obana

Yoshihiro Nakajima

Kazuhisa Yamada

Katsuhiro Shimano

Senior Research Engineer, Media Innovation
Laboratory, NTT Network Innovation Laboratories.
He received the B.E. and M.E in electricalengineering from Waseda University, Tokyo, in
1995 and 1997, respectively. After joining NTT
Optical Network Systems Laboratories in 1997,
he was engaged in R&D of priority queuing bytime and place information, a reverse proxy witha shaping function, and a fast transmitting systemwith multi-lanes. From 2008 to 2012, he worked
on R&D of customer premises equipment in
Promotion Project 1, NTT Cyber Solutions Laboratories. Since moving to NTT Network Innovation Laboratories in 2012, he has been engaged in
R&D of programmable nodes.

Senior Research Engineer, Media Innovation
Laboratory, NTT Network Innovation Laboratories.
He received the B.E. in electronics engineeringfrom Gunma University in 1987, after which hejoined NTT Electrical Communication Laboratories, where he engaged in research on a programmable transport system. Since 1998, he has beendeveloping carrier network operation systems,
and since 2003, he has also been developing a
digital television relay network operation system.
His current research interests are network virtualization and network management technologies
for future networks.
He is a member of the Institute of Electronics,
Information and Communication Engineers(IEICE).

Research Engineer, Media Innovation Laboratory, NTT Network Innovation Laboratories.
He received the B.S. in information science,
the M.E. in engineering, and the Ph.D. in computer science from the University of Tsukuba,
Ibaraki, in 2003, 2005, and 2008, respectively.
He was a research fellow of the Japan Society for
the Promotion of Science from 2005 to 2008. He
joined NTT Network Innovation Laboratories in2008 and studied high-performance stream processing systems and multilayer dynamic network
provisioning/control systems. He is currently
studying SDN and network virtualization technologies. He is a member of the Association for
Computing Machinery, the Information Processing Society of Japan, and IEEE.

Senior Research Engineer, Supervisor, Media
Innovation Laboratory, NTT Network Innovation
Laboratories.
He received the B.S. in physics from Waseda
University, Tokyo, in 1991 and the M.S. in physics from the University of Tokyo in 1993. Sincejoining NTT in 1993, he has studied optical networks and network management and relatedareas such as optical network management systems, GMPLS, and traffic engineering. He also
spent time at the headquarters working on NGN
network architecture from the first phase of construction. Recently, he has been leading the
research on SDN and network virtualization at
NTT Network Innovation Laboratories.

Masaki Fukui

Hitoshi Masutani

Senior Research Engineer, Media Innovation
Laboratory, NTT Network Innovation Laboratories.
He received the B.E. in communication engineering and the M.E. in electrical, electronic andinformation engineering from Osaka University
in 1999 and 2001, respectively. After joining
NTT Network Innovation Laboratories in 2001,
he studied multicast networking and SIP-based
home networking. In 2005, He moved to the
Visual Communication Division of NTTBizlink,
where he was responsible for developing andintroducing visual communication services,
including an IP-based high-quality large scale
video conferencing system and a real-time content delivery system on IPv6 multicast. He also
worked on developing their service order management system and network management system for video conference services.



Director, Media Innovation Laboratory, NTT
Network Innovation Laboratories.
He received the B.E., M.E., and Ph.D. inapplied physics from Osaka University, in 1987,
1989, and 1995, respectively. In 1989, he joined
NTT Transmission Systems Laboratories. He
was engaged in researching optical information
processing (optical computing) and WDM transmission systems. From 2001 to 2011, he worked
for NTT EAST R&D Center, where he workedon the development of network systems for IP
services and optical transport network systems.
In 2011, he moved to NTT’s laboratories again.
He is currently engaged in research on the architecture of future networks and network virtualization (SDN).

NTT Technical Review

Regular Articles

High-temperature Superconductivity
without Doping—Synthesis ofConceptually New Superconductors
Yoshiharu Krockenberger and Hideki Yamamoto
Abstract

High-temperature superconductivity is commonly associated with cuprate superconductors as theirsuperconducting transition temperatures are still highest among all of the superconducting materials. It
is these cuprate superconductors that drive scientists to reveal the very mechanism of its superconductivity
and to derive models capable of predicting new superconducting material systems. Cuprate
superconductors are built up of copper-oxygen planes, sandwiched by rare-earth or alkaline-earth oxide
layers. The copper-oxygen layers form infinitely long planes, and it is those planes where superconductivity
takes place. In particular, the copper ions in those planes may have three distinct coordinations, i.e.,octahedral, pyramidal, and square-planar. Quite generally, electronic states are a function of crystal
structure, crystal symmetry, and the elements building up the crystal structures. Nevertheless, it has been
widely assumed that the copper-oxygen planes are inherently insulating and superconductivity is inducedby doping carriers into those copper-oxygen planes. Indeed, such an approach is suitable for the copperoxygen layers with octahedral and pyramidal coordinated copper, where superconductivity is induced byhole doping. For cuprates with square-planar coordinated copper, however, we demonstrate here thatelimination of defects by annealing is the key to inducing superconductivity and doping is not aprerequisite for the emergence of superconductivity.
Keywords: undoped superconductor, high-Tc cuprates, molecular beam epitaxy

1. Introduction
High-temperature superconductivity is a key technology for many present and future milestones ranging from transportation [1], over medical applications[2] towards elementary particle physics [3]. Among
all superconducting materials known so far, the discovery of cuprate superconductors was not only
awarded by the Nobel prize [4] but still hold record
high superconducting transition temperatures as highas 150 K [5]. Despite all efforts and progress made tounderstand the underlying mechanism driving superconductivity in those cuprates, conclusive theoreticalmodels remain elusive. Solving the enigma of cuprate
superconductivity, however, holds the key for materials with even higher superconducting transition temperatures. One of the crucial factors that drives super

conductivity in cuprates are the copper-oxygen planes
and the local environment of the Cu ions in thoseplanes. Generally, three different geometries are stabilized in cuprate superconductors, i.e., octahedral,pyramidal, and square-planar. In many cases, thosecoordination cages do not appear exclusive but ascombinations, e.g., pyramidal and square-planar in
Bi2Sr2Ca2Cu3O10+δ. The local coordination of thecopper ions has far reaching implications on the electronic structure. Revealing electronic structures subject to a specific coordination is therefore of importance. La2-xSrxCuO4 is a cuprate with solely octahedrally coordinated copper and it is one of the mostwidely studied systems among cuprate superconductors and commonly termed “T-phase.” Cuprates withsolely square-planar coordinated copper are muchless studied owing to the difficult and cumbersome
NTT Technical Review

Regular Articles

(a)

(b)

(c)
(001)Pr2CuO4

500
100

c

qz(001) (nm−1)

10

a

b
The CuO2 planes are green
shaded for clarity reasons.

(−103)
SrTiO3

2(−109)Pr2CuO45 nm(001)SrTiO3

qx(−100) (nm−1)
Vertical lines indicate that thefilm is entirely relaxed.

Fig. 1. (a) Crystal structure of Pr2CuO4, (b) high-resolution reciprocal space map of Pr2CuO4 grown on (001) SrTiO3
substrate, and (c) high-resolution transmission electron microscopy image of Pr 2CuO4 grown on (001) SrTiO3
substrate taken at the interface.

process in synthesis as well as inducing superconductivity to them. Hence, data reported for these systems
are significantly dressed and dominated by electronic
correlations stemming from impurity and defectrelated influences. In contrast to those earlier reports,
we can synthesize cuprate superconductors by molecular beam epitaxy under oxidizing conditions.
Molecular beam epitaxy is a well-known and widelyused technique for synthesizing semiconductors andsemiconductor-related devices. We further refinedand optimized this technique with the scope of ultrahigh quality cuprate materials [6]. Crystalline materials with the utmost degree of perfection are mandatory prerequisites in revealing electronic and magnetic correlations in cuprates with respect to the various coordination geometries of copper. Two cuprates,
where copper is square-planar coordinated, are
known, i.e., Nd2CuO4–structure [7, 8] and infinitelayer structure [9]. While the Nd2CuO4–structure(T’-structure) can be synthesized under ambient conditions, the formation of bulk infinite-layer cuprates
occurs only under high pressure. The T’-structure
belongs to the Ruddelsden-Popper series of transition
metal oxides [10–12], which is also the case for the
T-structure. In contrast to other transition metaloxides, where the transition metal ion is octahedrally
coordinated, the copper ion is forced to be squareplanar coordinated in the T’-structure and the force isVol. 12 No. 8 Aug. 2014brought by the tolerance factor [13]. The defects
appear at the apical position of copper, forming
locally pyramidal coordinated copper. Electronically,
this situation represents an insulating and antiferromagnetic ground state. Upon elimination of thosedefects (by elaborate annealing), the entire electronic
structure changes from an antiferromagnetic insulator to a superconducting metal. In the following we
focus on our efforts to elucidate the electronic structure of ultra-high quality T’-cuprate superconductors
where such defects have been eliminated by annealing.
2. Experimental
High quality thin films of Pr2CuO4 are grown by
molecular beam epitaxy onto (001) SrTiO3 substrates[14]. Pr and Cu are evaporated by e-beam evaporationfrom metal-sources and the evaporation rate is controlled by electron impact emission spectroscopy[15–18]. Ozone or radio frequency (RF) activatedoxygen is used as an oxidizing agent. The growth ismonitored by reflection high energy electron diffraction (RHEED) which allows not only fine tuning ofgrowth conditions but a real-time feedback of film
growth. In Fig. 1, the crystal structure of Pr2CuO4,
high-resolution reciprocal space map (HRRSM) of
the epitaxial relation, and high-resolution transmission
3. Results and discussions
3.1 Standard annealing
The term “standard annealing” may seem confusing though it simply describes annealing conditions
used for the induction of superconductivity at doping
levels of x = 0.15; i.e., Pr1.85Ce0.15CuO4 [30, 31]. As
annealing of Ce doped Pr2CuO4 is carried out underultra-high vacuum, only two annealing parameters,
time and temperature, are to be considered. Applying
the standard annealing approach leads to phase diagram of Pr2-xCexCuO4 as shown in Fig. 3. At low Ce
doping levels (x < 0.11) the system is insulating andsuperconductivity sets in for x > 0.12. This phase
diagram (Fig. 3) inevitably is identical to what has
been reported for single crystals or powder samples.



101

30

S

60

(0012)
90(0014)

S

S(0010)

(008)

S

(006)

(002)

106
Intensity (cps)electron microscopy (HRTEM) image of Pr2CuO4
films on (001) SrTiO3 substrates are shown, respectively. Here, growth conditions are tuned in order toallow for a relaxed but epitaxial growth of single
phase and c-axis oriented Pr 2 CuO 4 on SrTiO 3 .
Throughout the following experiments and discussions, the film thickness was kept constant at 100 nm.
In Fig. 2, X-ray diffraction of a Pr2CuO4 film on(001) SrTiO3 substrate is shown. Using a NelsonRiley [19] function allows for a precise determinationof c-axis lengths as this is an important control
parameter.
As discussed in the introduction, the as-grown
Pr2CuO4 is insulating due to the presence of overstoichiometric oxygen occupying the apical sites ofcopper [20–24]. As it is well known from Ce doped
Pr2-xCexCuO4, annealing is required for the inductionof superconductivity—otherwise, the system remains
insulating and antiferromagnetic. During the annealing process, the apical oxygen leaves the Pr2CuO4
crystal. Such a process is a diffusion process though
in case of Pr2CuO4 a detailed understanding remains
elusive owing to the three different oxygen positionsin the T’-crystal structure [25–29]. Here, we applieda two-step annealing process [15], which allows foran effective evacuation of apical sites, while regularoxygen positions are not affected. The annealing procedure requires that thermodynamic constraints of
Pr2CuO4 itself are not violated (this leads to decomposition). At the same time, an appropriate annealingis achieved only near or on thermodynamic boundary
on a delicate balance of kinetically driven competition.

(004)

Regular Articles

120

2θ (º)

Fig. 2. X -ray diffraction pattern taken of Pr2CuO4 grown on(001) SrTiO3 substrate.

3.2 2-step annealing
Applying standard annealing conditions toPr2-xCexCuO4 is effective for the induction of superconductivity for x > 0.11. In Pr2-xCexCuO4, the addition of Ce not only acts as a dopant but as a defect[32]. If less Ce is incorporated into the Pr2-xCexCuO4
crystal, the crystallite dimensions rapidly increase.
The path taken by oxygen leaving Pr2-xCexCuO4 crystals is predominantly along the CuO2 planes until
reaching a grain boundary. The thermodynamic environment under standard annealing conditions is
unsuitable for establishing such a condition over long
periods of time or at elevated temperatures due to thesimultaneously occuring defects at regular oxygensites. This diffusion problem of identical species atcompeting sites is not limited to thin film but to amuch larger extent to single crystals owing to their
reduced surface/volume ratio. However, this problem
can be overcome by introducing an intermediate
annealing step. This situation is visualized in the thermodynamic phase diagram plotted in Fig. 4. In contrast to the standard annealing procedure, Pr2CuO4 is
kept at a temperature comparable or even higher than
the synthesis temperature used during its growth [33].
Moreover, an environment with small but finite partial oxygen pressure is stabilized for 60 min before
the sample temperature is cooled to the second
annealing step. In Fig. 5, the temperature dependenceof resistivity is plotted for all three positions of thethermodynamic phase diagram. The as-grown
Pr 2CuO 4 is insulating and its resistivity further
increases after the 1st annealing step. This behavior
indicates that additional defects, tapering the electron
mobility, are created. Schematically, this is shown in
Fig. 6. While the as-grown Pr2CuO4 posseses defects
primarily related to occupied apical sites, the first
NTT Technical Review

Regular Articles

(a)
900

109

(b)
700 600106

500 (ºC) 400

50

MBE
(O*)

40

103

4P
r 2C

10−3

20

T (K)

30

AFI

pO2 (Torr)standard annealinguO

annealing

4

4P

10

−6

10

r 2O

SC

C
+2

3

2
+O

O
u2

10−9
0.8

1.4

1.0

1.6 0

103 T−1 (K−1)
The growth was assisted either
by ozone or RF activated oxygen.

0.05

0.10 0.15
xCe

0.20

0
0.25

The standard annealing procedurestabilizes the superconducting phasewithin a distinct range of Ce doping.

AFI: antiferromagnetic insulator
MBE: molecular beam epitaxy
SC: superconducting

Fig. 3. (a) Thermodynamic phase diagram in the vicinity of the growth conditions of Pr2-xCexCuO4 (red area) and annealing
conditions (blue area) and (b) superconducting phase diagram of Pr2-xCexCuO4 grown on (001) SrTiO3 substrates
as a result of the annealing procedure shown on the left.

10

9

(a)
900

700 600(b)

500 (ºC) 400

this work
M. Brinkmann et al.

106

MBE
(O*)

50

40

103
pO2 (Torr)

2-stepannealing

30

20

uO

r 2C
4P

10−3

T (K)

annealing
(1st)

4

r 2O
4P

10−6

annealing
(2nd)

SC

10

+2

3

+O
O
u2

C

10−9

2

0.8

1.4

1.0

1.6 0

103 T−1 (K−1)
The growth was assisted either
by ozone or RF activated oxygen.

0.05

0.10 0.15
xCe

0.20

0
0.25

The 2-step annealing procedurestabilizes the superconducting phaseover the entire range of Ce doping.

Fig. 4. (a) Thermodynamic phase diagram in the vicinity of the growth conditions of Pr2-xCexCuO4 (red area) and annealing
conditions (green and blue area) and (b) superconducting phase diagram of Pr2-xCexCuO4 grown on (001) SrTiO3
substrates as a result of the annealing procedure shown on the left. Data denoted by triangles are taken from Ref. [34].

Vol. 12 No. 8 Aug. 2014

Regular Articles

(b)

Ste

12.26
12.25
12.24
12.23
12.22
12.21
12.20

Step II

3.965

101
100

as

wn

10−2
10−3
−4

3.960

10−5

3.955

10

10−6

0

100

200

300
as grown

T (K)a0 (Å)p (Ωcm)

10−1

pI

gro

c0 (Å)

(a)
102

3.950
Step I

Step II

The 1st annealing step does not alter
the over-all crystallographic dimensions. After the 2nd annealing step,
c-axis lengths are significantly lower
due to the release of excess oxygen.
However, the in-plane lattice constantremains constant even after the 2nd
annealing step.

Fig. 5. (a) Temperature dependence of resistivity of Pr2CuO4 thin films in as-grown state (green dashed line), after the 1st
annealing step (step I), and after the 2nd annealing step (step II) and (b) trace of the crystallographic lattice parametersof Pr2CuO4 thin films.

(a)

(b)

(c)

pyramid

→
c
→
a

O3
→
b
as grown

first annealing
O1 vacancy

Cu O1
As-grown Pr2CuO4
posseses a noticableamount of oxygen,located at the apical
positions of copper.

second annealing

After the 1 annealing step,
oxygen vacancies are
generated within the CuO2
planes, resulting in an evenhigher resistivity value.
stDuring the second annealing
step, oxygen vacanies createdduring the 1st annealing step
are annihilated which allow fornearly defect-free CuO2 planes
without apical oxygen.

Fig. 6. Microscopic view of oxygen vacancies and defects at each synthesis or annealing step.

annealing step is about to increase the defects within
the CuO2 planes. Consequently, the absolute resistiv

ity value increases. Simultaneously, the overall crystallographic dimensions remain nearly unaffected.
NTT Technical Review

Regular Articles

This does change, however, dramatically after thesecond annealing step and the c-axis value shrinks
noticably. Most dramatic is the influence on the resistivity behavior as it not only changes from aninsulating to a metallic state but to superconductivity.
This behavior is again common to what is known tohappen during the conventional annealing process for
Ce-doped Pr2-xCexCuO4 (x > 0.11). Accordingly, ourstudy has revealed an intrinsic electronic phase diagram for Pr2-xCexCuO4, which was hampered byenigmatic and cumbersome processes in optimizing
annealing conditions.
4. Conclusion
It has been assumed that the high-Tc cuprates universally have an insulating ground state in theirundoped state due to electronic correlations, and doping is necessary to change the correlations and induce
superconductivity. However, a series of our studies
have revealed that the cuprates with the square-planar
coordinated Cu have a metallic ground state and showsuperconducting transition after removal of defects
from the playground of high-Tc superconductivity,
i.e., the copper-oxygen planes. This observation isagainst the main paradigm in theories of high-Tc
superconductivity. Although, at the moment, thisconclusion is still under intense debate, the very
result of our research will be a turning point in thequest for high-Tc superconductivity once further
investigations support it.
References
[1]
[2]
[3]
[4]
[5]
[6]

[7]
[8]

K. Kitazawa, “Superconductivity: 100th Anniversary of Its Discovery
and Its Future,” Japanese Journal of Applied Physics, Vol. 51, 010001,
2012.
E. M. Haacke, R. W. Brown, M. R. Thompson, and R. Venkatesan,“Magnetic Resonance Imaging: Physical Principles and Sequence
Design,” Wiley, 1999.
M. Riordan, “The Demise of the Superconducting Super Collider,”Phys. Perspect, Vol. 2, No. 4, pp. 411–425, 2000.
J. G. Bednorz and K. A. Müller, “Possible high Tc superconductivity
in the Ba−La−Cu−O system,” Z. Physik B - Condensed Matter, Vol.
64, No. 2, pp. 189–193, 1986.
N. Takeshita, A. Yamamoto, A. Iyo, and H. Eisaki, “Zero Resistivity
above 150 K in HgBa2Ca2Cu3O8+δ at High Pressure,” Journal of the
Physical Society of Japan, Vol. 82, 023711, 2013.
H. Yamamoto, Y. Krockenberger, and M. Naito, “Multi-source MBE
with High-precision Rate Control System as a Synthesis Method Sui
Generis for Multi-cation Metal Oxides,” Journal of Crystal Growth,Vol. 378, pp. 184–188, 2013.
Y. Tokura, H. Takagi, and S. Uchida, “A Superconducting Copper
Oxide Compound with Electrons as the Charge Carriers,” Nature Vol.
337, pp. 345–347, 1989.
H. Müller-Buschbaum and M. W. Wollschläger, “Über ternäre Oxocuprate. VII. Zur Kristallstruktur von Nd2CuO4,” Zeitschrift für anorganische und allgemeine Chemie, Vol. 414, No. 1, pp.76–80, 1975.

Vol. 12 No. 8 Aug. 2014[9]

Y. Krockenberger, K. Sakuma, and H. Yamamoto, “Molecular Beam
Epitaxy and Transport Properties of Infinite-layer Sr0.90La0.10CuO2Thin Films,” Applied Physics Express, Vol. 5, No.4, 043101, 2012.
[10] S. N. Ruddlesden and P. Popper, “New Compounds of the K2NiF4Type,” Acta Crystallographica, Vol. 10, No. 8, pp. 538–539, 1957.
[11] S. N. Ruddlesden and P. Popper, “The Compound Sr3Ti2O7 and Its
Structure,” Acta Crystallographica, Vol. 11, No. 1, pp. 54–55, 1958.
[12] R. E. Schaak and T. E. Mallouk, “Perovskites by Design: A Toolboxof Solid-state Reactions,” Chemistry of Materials, Vol. 14, No. 4, pp.
1455–1471, 2002.
[13] V. M. Goldschmidt, “Die Gesetze der Krystallochemie,” Die Naturwissenschaften, Vol. 14, No. 21, pp. 477–485, 1926.
[14] Y. Krockenberger, H. Yamamoto, A. Tsukada, M. Mitsuhashi, and M.
Naito, “Unconventional Transport and Superconducting Properties inElectron-doped Cuprates,” Physical Review B, Vol. 85, 184502,
2012.
[15] H. Yamamoto, O. Matsumoto, Y. Krockenberger, K. Yamagami, and
M. Naito, “Molecular Beam Epitaxy of Superconducting Pr2CuO4
Films,” Solid State Communications, Vol. 151, No. 10, pp. 771–774,
2011.
[16] H. Yamamoto, Y. Krockenberger, and M. Naito, “Augmented Methods
for Growth and Development of Novel Multi-cation Oxides,” Proc. of
SPIE 8987, Oxide-based Materials and Devices V, 89870V, 2014.
[17] C. Lu, C. D. Blissett, and G. Diehl, “An Electron Impact Emission
Spectroscopy Flux Sensor for Monitoring Deposition Rate at High
Background Gas Pressure with Improved Accuracy,” Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 26,
No. 4, pp. 956–960, 2008.
[18] C. Lu, M. J. Lightner, and C. A. Gogol, “Rate Controlling and Composition Analysis of Alloy Deposition Processes by Electron Impact
Emission Spectroscopy (EIES),” Journal of Vacuum Science & Technology, Vol. 14, No.1, pp. 103–107, 1977.
[19] J. B. Nelson and D. P. Riley, “An Experimental Investigation ofExtrapolation Methods in the Derivation of Accurate Unit-cell
Dimensions of Crystals,” Proceedings of the Physical Society, Vol. 57,
No. 3, pp. 160–177, 1945.
[20] A. J. Schultz, J. D. Jorgensen, J. L. Peng, and R. L. Greene, “Singlecrystal Neutron-diffraction Structures of Reduced and Oxygenated
Nd2−xCexCuOy,” Physical Review B, Vol. 53, 5157, 1996.
[21] P. G. Radaelli, J. D. Jorgensen, A. J. Schultz, J. L. Peng, and R. L.
Greene, “Evidence of Apical Oxygen in Nd2CuOy Determined bySingle-crystal Neutron Diffraction,” Physical Review B, Vol. 49,
15322, 1994.
[22] P. W. Klamut, “Evidence for Interstitial Oxygen and Possible Role ofReduction in Nd2−xCexCuO4 + y,” Journal of Alloys and Compounds,
Vol. 194, No. 1, pp. L5–L7, 1993.
[23] C. Sułkowski, A. Sikora, P. W. Klamut, and R. Horyñ, “Transport
Properties and Oxygen Sublattice Time Relaxation of Nd2CuO4−δ,”Solid State Communications, Vol. 112, No. 11, pp. 601–604, 1999.
[24] T. Klimczuk, W. Sadowski, J. Olchowik, and E. Walker, “Crystal
Growth and the Influence of Oxygen Stoichiometry on Electrical
Resistivity of Nd2−xCexCuO4-y Single Crystals,” Superconductor Science and Technology, Vol. 12, No. 4, pp. 199–202, 1999.
[25] N. L. Allan and W. C. Mackrodt, “Defect Chemistry of La2CuO4,
Nd2CuO4 and Pr2CuO4 Doped by Tetravalent Cations: Relevance toHigh-Tc Behaviour,” Philosophical Magazine Letters, Vol. 60, No. 5,
pp. 183–186, 1989.
[26] N. L. Allan and W. C. Mackrodt, “Oxygen Interstitial Defects in HighTc Oxides,” Molecular Simulation, Vol. 12, No. 2, pp. 89–100, 1994.
[27] P. Ghigna, G. Spinolo, A. Filipponi, A.V. Chadwick, and P. Hanmer,“EXAFS Evidence of Interstitial Oxygen Defects in Nd2CuO4+δ,”Physica C: Superconductivity, Vol. 246, pp. 345–350, 1994.
[28] Y. Idemoto, K. Fueki, and M. Sugiyama, “Diffusion Coefficients ofOxygen in Nd2CuO4−δ,” Journal of Solid State Chemistry, Vol. 92, No.
2, pp. 489–495, 1991.
[29] Y. Idemoto, K. Uchida, and K. Fueki, “Anisotropic Diffusion of Oxygen in Nd2CuO4−δ Single Crystal,” Physica C: Superconductivity, Vol.
222, No. 3–4, pp. 333–340, 1994.
[30] Y. Krockenberger, H. Yamamoto, M. Mitsuhashi, and M. Naito,Regular Articles“Universal Superconducting Ground State in Nd1.85Ce0.15CuO4 andNd2CuO4,” Japanese Journal of Applied Physics, Vol. 51, No. 1,
010106, 2012.
[31] Y. Krockenberger, J. Kurian, A. Winkler, A. Tsukada, M. Naito, and
L. Alff, “Superconductivity Phase Diagrams for the Electron-doped
Cuprates R2−xCexCuO4 (R=La, Pr, Nd, Sm, and Eu),” Physical Review
B, Vol. 77, 060505, 2008.
[32] K. Byrappa and T. Ohachi, “Crystal Growth Technology,” Springer,
2003.

Yoshiharu Krockenberger

Distinguished Researcher, Thin-Film Materials Research Group, NTT Basic Research Laboratories.
He received his diploma in physics from theTechnical University of Munich in 2002 and his
Ph.D. in physics from the Darmstadt Universityof Technology in 2006. His principal researchareas are superconductivity, strongly correlated
electron systems and thin film growth. He has
been working at NTT since 2010. In the meantime, he was a research scientist at RIKEN,
Advanced Scientific Institutes, in the cross-correlated materials research group of Prof. Y.
Tokura (2006–2010).

[33] Y. Krockenberger, H. Irie, O. Matsumoto, K. Yamagami, M. Mitsuhashi, A. Tsukada, M. Naito, and H. Yamamoto, “Emerging Superconductivity Hidden Beneath Charge-transfer Insulators,” Sci. Rep. Vol.
3, 2235, 2013.
[34] M. Brinkmann, T. Rex, H. Bach, and K. Westerholt, “Extended Superconducting Concentration Range Observed in Pr2−xCexCuO4−δ,” Phys.
Rev. Lett., Vol. 74, No. 24, pp. 4927–4930, 1995.

Hideki Yamamoto

Group Leader of Thin-Film Materials ResearchGroup, Executive Manager, Research Planning
Section, NTT Basic Research Laboratories.
He received his B.S., M.S., and Ph.D. in chemistry from the University of Tokyo in 1990, 1992,
and 1995, respectively. His principal researchareas are thin film growth, surface science, andsuperconductivity. He has been working at NTT
since 1995. He was a visiting scholar of Geballe
Laboratory for Advanced Materials, Stanford
University (2004–2005). He is a member of
JSAP (The Japan Society of Applied Physics),
JPS (The Physical Society of Japan), SSSJ (The
Surface Science Society of Japan), APS (TheAmerican Physical Society), and MRS (TheMaterials Research Society).

NTT Technical Review

Global Standardization Activities

Standardization Activities ofoneM2M
Akihiro Tsutsui and Yoshinori Goto
Abstract

Machine-to-machine (M2M) services have been developed independently in a diverse range of fields
such as industrial machinery and logistics. Demand has been increasing recently for an expansion of themarket by building a common M2M platform and using mutual exploitation of M2M data across different industries. In 2012, major regional standards development organizations of Europe, the UnitedStates, and Asia established a unified standardization body named ‘oneM2M’ for M2M-associated technologies. This article presents the current status and future activities of oneM2M.
Keywords: M2M, standardization, oneM2M

1. Introduction
The major regional telecommunications standards
development organizations (SDOs) establishedoneM2M in July 2012 in order to develop a set ofcommon technical specifications for machine-tomachine (M2M) technologies. These SDOs are:Europe: E
 TSI (European Telecommunications
Standards Institute)
USA: ATIS (Alliance for Telecommunications
Industry Solutions)
TIA (Telecommunications Industry Association)
China: C CSA (China Communications Standards
Association)
Korea: T TA (Telecommunications Technology
Association of Korea)
Japan: ARIB (Association of Radio Industries andBusinesses)
T TC (Telecommunication Technology
Committee)
These SDOs involved in establishing oneM2M arereferred to as Partners Type 1. As of March 2014,
through these type-1 SDOs, more than 200 companies had joined oneM2M as Members who are committed to contributing to the development of common
specifications. In addition, some industry organiza

tions such as Continua Health Alliance, HGI (Home
Gateway Initiative), and OMA (Open Mobile Alliance) have joined oneM2M as Partners Type 2. Members are made up of a majority of the companies thatare also ETSI members. This is because ETSI was
involved in creating standards for M2M technologies
before oneM2M was established. Most Members
consist of telecommunications operators and device
vendors. The Partners Type 2 are considered to be key
players in the dissemination of standards. However,
only a few organizations have joined oneM2M as aPartner Type 2, and the industry segments represented
by them are limited as of now. Promoting the activities of oneM2M is one of the tasks the Partner Type 2
organizations are required to carry out.
The main goal of oneM2M is to create specifications of a common platform for M2M services thathave been vertically integrated until now. One of theimportant benefits of this standardization is reducing
the cost of deploying M2M systems by using common hardware and software specifications. Common
interface specifications provided by oneM2M will
enable various applications to access M2M systems
and devices in a uniform way. In addition, various
data coming from M2M devices can be distributed
across different business fields. This is expected tohelp enlarge the market associated with M2M. After
collecting typical use cases, oneM2M creates M2M
NTT Technical Review

Global Standardization Activities

Technical Plenary
Chair:
Peter Nurse (Qualcomm)Vice Chairs: Yong Chang (Samsung)
Joachim Koss (Cinterion)
Norikazu Yamazaki (KDDI)

Steering
Committee

Finance Subcommittee

Financial planning

Legal Subcommittee

Legal advisory

Methods and Process Subcommittee

Working methods,
documentation rules

Marketing and Communications Subcommittee Dissemination
Program Management Ad-hoc

Scheduling

TP Coordination Ad-hoc

TP management

Method of Work Ad-hoc

WorkflowWG1 (Requirements)
Stage 1
(Use cases andrequirements)

WG2 (Architecture)
Stage 2
(Architecture)

WG3 (Protocol)
Stage 3
(Protocols,
technical specs.)

WG4 (Security)
Security issues
associated withall working items

WG5 (Management,
abstraction and semantics)
Device abstraction
management

Fig. 1. Organization chart of oneM2M.

technical specifications using a three-step approach:requirements (stage 1), architecture (stage 2), andprotocols (stage 3). In addition, security and management technologies for operating M2M platforms
safely and reliably are discussed. All of these work
items are discussed in working groups (WGs). An
organization chart of oneM2M is shown in Fig. 1.
The Technical Plenary (TP) is the main body working
on technical specifications and consists of five WGs.
Each WG primarily handles requirements, architecture, protocols, security, and management. The SC(Steering Committee) deals with strategic issues
including budget and IPR (intellectual property
rights). In addition, MARCOM (MARketing andCOMmunications) was established in order tostrengthen marketing activities. Currently, oneM2M
is promoting dissemination of its activities.
2. Current activities
oneM2M initiated technical discussions at its firstTP meeting held in September 2012. As of March
2014, nine TP meetings had been held (six times peryear). The meeting location rotates between Europe,
the USA, and Asia. Some WGs hold teleconferences
once a week or every two weeks, and their technicaldiscussions are very active.
Vol. 12 No. 8 Aug. 2014

The status of standardization work is shown in
Fig. 2. In the early stage of oneM2M’s establishment,
the members planned to issue the first release of
specification documents at the end of 2013. However,their work plan was delayed as a result of someexhaustive discussions. Consequently, the first releaseof the common specifications is expected to be in the
middle of 2014. As of April 2014, the technicalspecifications of the requirements and the associatedtechnical reports had been completed. The architectural work is in the final stage. At the 8th and 9th TP
meetings, held respectively in December 2013 andFebruary 2014, many contributions regarding architectural work were discussed and agreed. Moreover,the protocol WG also started technical discussions on
protocol specifications.
oneM2M has accelerated standardization activities
as mentioned before, and some completed deliverables have been published. The documents of usecase collections and requirements have been approvedby a oneM2M TP and have been published by some
SDOs. The oneM2M standards release 1 will beapproved in the 12th TP meeting scheduled for August
2014. This release is called the minimum deployablemodel. Further discussion will be required in order tocreate more practical and detailed specifications.
After the first version of specifications is released,Global Standardization Activities

Preparation meeting( — Jul. 2012)

Release 1: Discussion and documentation(Sept. 2012 — Aug. 2014)
TP#1

Agreement
among SDOs

TP#8

TP#9

Release 2(Sept. 2014 — )TP#10 TP#11 TP#12

Face-to-face meetings (6 times per year)
Release 2

Stage 1: Requirements
Stage 2: Architecture
Stage 3: Protocols
Release 1 approval
August 2014 (target)

Fig. 2. oneM2M working status.

oneM2M will continue its standardization work andproduce documents using the point release method,which means that specification documents will be
released sequentially as soon as they are approved.
The following documents will be included in release 1.
• Definitions and Acronyms• M2M Architecture• M2M Requirements• oneM2M Security Solutions• oneM2M Protocol Technical Specifications
At least one of the following documents will also be
included.
oneM2M Management Enablement (OMA)	oneM2M Management Enablement (BBF:
Broadband Forum)
Finally, at least one of the following documents will
be included.
	CoAP (Constrained Application Protocol)
Protocol Binding Technical Specification
	HTTP (Hypertext Transfer Protocol) Protocol
Binding Technical Specification
	MQTT (Message Queuing Telemetry Transport) Protocol Binding Technical Specification
Continua Health Alliance, a Partner Type 2, provided feedback in the form of an analysis of the gap
between their own architecture model and a model
discussed in oneM2M. However, other Partners Type 2
do not seem to be as actively involved. The expectation is that the first release will trigger greater interest
from these partners and other specification users.



3. Overview of architecture specifications
The basic architecture model discussed in oneM2M
is shown in Fig. 3. CSEs (Common Service Entities)
are defined as entities located between an AE (Application Entity) and NSE (Network Service Entity).
These three basic entities communicate with eachother in this model. Generally, M2M services should
be deployed on a wide variety of networks, both
mobile and fixed. Therefore, detailed technical issues
that are specific to the underlying network technologies are avoided in principle. This basic architecture
model enables M2M applications to communicate
with CSEs implemented in servers, M2M terminal
devices, and gateways via reference points (Mca,Mcc, Mcn, and Mcc’ in Fig. 3). CSEs are collectionsof common functions utilized by various M2M services such as device management. When CSEs are
implemented in M2M servers and devices, the M2M
applications can easily handle various sensors andactuators. This platform architecture supports installation and separation of applications. It is possible toutilize an M2M device by using different applications
independently of each other. Data separation andsharing is also supported between different applications using the appropriate authentication mechanism. The physical components such as M2M servers
and devices with CSEs are called nodes. An example
structure of a network and M2M nodes is shown in
Fig. 4. The CSEs are the key of this architecture
model, and they include 12 functions, as shown in
Fig. 5. These functions include device discovery,
device and application management, data management and repository, and authentication and security
NTT Technical Review

Global Standardization Activities

Terminal

Server

AE

AE
Mca

Mca

Mca

Mcc

CSE

Application Entity (AE)

Mcc’

CSE

Mcn

Other providers

Mcn
Common Service Entity (CSE)

NSE

NSE

Network Service Entity (NSE)

Fig. 3. Basic architecture model.

Infrastructure node
AE
CSE
Network
AE
Application
service nodeAE

AE

Application
dedicated node

CSE

NononeM2M
deviceNononeM2M
deviceMiddle node

CSE

AE

AE

Application
dedicated node

CSE

Application
service node

NononeM2M
deviceFig. 4. Example structure of nodes and network.

associated functions. Completing the protocol specifications for communication between nodes is one of
the most important tasks of oneM2M. WG3 is currently discussing this issue. As of June 2014, they hadfinished analyzing existing protocols related to M2M
services. HTTP, CoAP (a lightweight HTTP), and
MQTT (a scalable protocol designed for M2M communication), are the presumed standardization targets.

Vol. 12 No. 8 Aug. 2014

4. Future work
oneM2M is accelerating its activities as it prepares
to issue the first release of specifications. The firstrelease will, however, provide limited capabilities.
Further work will be necessary to produce moredetailed and practical specifications that can be utilized for implementation of actual M2M platforms.
TP meetings will continue to be held six times per
year, and further technical specifications will be
released sequentially as soon as they are approved.
Global attention on oneM2M is expected to increaseGlobal Standardization ActivitiesAE

Mca reference point

CSE
Application andservice layer
management

Security

Service session
management

Service charging
and accounting

Datamanagement
and repository

Communication
management
delivery handling

Devicemanagement

Discovery

Location

Registration

Subscription
notification

Network service
exposure, service
Ex + Triggering

Mcn reference point

NSE

Fig. 5. CSE functions.

when its first set of specifications is released.
Reference
Website of oneM2M, http://www.onem2m.org/

Akihiro Tsutsui

Senior Research Engineer, Supervisor, NTT
Network Innovation Laboratories.
He received the B.E. and M.E. in systems
engineering from Kobe University, Hyogo, in1988 and 1990, respectively. Since joining NTT
in 1990, he has been researching programmablenetwork devices, high-performance Internet protocols, and home networking. His current interests include ubiquitous computing technologies
and personal data distribution platform architecture in the IoT service domain.

Yoshinori Goto

Senior Research Engineer, Network Technology Project, NTT Network Technology Laboratories.
He received the B.E. and M.E. in applied physics from Tohoku University, Miyagi, in 1992 and1994, respectively. He joined NTT Basic
Research Laboratories in 1994. He has been
involved in standardization activities in various
areas such as cable television, IPTV (Internet
Protocol television), NGN (Next Generation
Network), and M2M, primarily with the International Telecommunication Union, Telecommunication Standardization Sector (ITU-T); he is also
active in many forums and does regional coordination work. He is serving as vice chairman of
ITU-T Study Group 13. He is a member of theInstitute of Electronics, Information and Communication Engineers.

NTT Technical Review

Practical Field Information about
Telecommunication Technologies

Fault Cases in an IP Phone Circuit
Accommodating a PBX via a
VoIP-GW
Abstract

This article introduces fault cases in an Internet protocol (IP) phone circuit accommodating a PBX(private branch exchange) via a VoIP-GW (voice over IP gateway). This is the twenty-fourth of abimonthly series on the theme of practical field information on telecommunication technologies. This
month’s contribution is from the Network Interface Engineering Group, Technical Assistance and Support Center, Maintenance and Service Operations Department, Network Business Headquarters, NTT
EAST.
Keywords: IP phone, PBX, VoIP-GW

1. Introduction
The penetration of broadband services has alsoreached telephone services, which has led to a migration from analog phones to Internet protocol (IP)phones. We introduce here two cases of faults occurring in a configuration that accommodates a private
branch exchange (PBX) via a voice over IP gateway(VoIP-GW) in an IP phone circuit. These examples
show how faults can be investigated by collecting
data at various troubleshooting points, and they also
demonstrate the importance of maintaining therequired values stipulated in product specifications.
2. Overview of fault cases
2.1 L ine disconnect occurs when PBX receives
an outside call
2.1.1 Equipment configuration
The equipment configuration of a customer thatuses NTT’s IP phone service called Hikari Denwa isshown in Fig. 1. The PBX is connected to the optical
network unit (ONU) through the VoIP-GW with three
analog lines. One of the lines leads to the interactive
voice response (IVR) equipment as a result of branching off the path from the VoIP-GW into the PBX
equipment. The VoIP-GW is also connected to anEthernet line, and it bidirectionally converts analog
signals into IP packets or IP packets into analog signals.
2.1.2 Fault description
When incoming calls came in from the outside, theline would sometimes disconnect before answering.
This problem had been occurring since the time ofanalog-line use prior to introducing Hikari Denwa.
2.1.3 Inspection method
Since we could not confirm the occurrence of a line
disconnect before answering in an on-site incomingcall connection test, we decided to conduct long-termmonitoring and analyze the collected data. The
inspection setup is shown in Fig. 2 and described
below.
a)	We used a maintenance console installed in apersonal computer (PC) to collect and analyze
the VoIP-GW call log.
b)	We used a packet capturing tool installed in a
PC to capture packets in the Ethernet section
between the ONU and the VoIP-GW and thenanalyzed the captured data.
c)	We used a waveform recorder to monitor signals in the analog-interface section between the
VoIP-GW and the PBX equipment.
2.1.4 Inspection resultsa)	The call log collected from the VoIP-GW
NTT Technical Review

Practical Field Information about Telecommunication Technologies

Branch connection

3 lines
Hikari Denwa
ONU

VoIP-GWPBX equipment
Extension phones
IVR equipment
EthernetsectionAnalog-interface
sectionFig. 1. Equipment configuration.

VoIP-GW 3 lines

Branch connection

Hikari Denwa
ONU
PBX equipment
Extension phones

PC for packet
capturing

PC formaintenanceconsoleIVR equipment
Waveform
recorderFig. 2. Inspection setup.

revealed the existence of calls in which the timeinterval from incoming-call response to line
disconnect was less than one second. It was
confirmed that all of these calls were disconnected by the VoIP-GW on the call-terminatingside. These results are shown in Fig. 3.
b)	No packets that could be considered abnormal
were found from the analysis of packet-capture
data. However, packet sequences also revealed
calls in which the time interval from call initiation to termination was less than one second,which was in agreement with the VoIP-GW calllog. These results are shown in Fig. 4.
c)	At the times this fault occurred, signal monitoring between the VoIP-GW and PBX equipment
revealed that the line would disconnect immediately after the PBX responded to the interrupted ringing (IR) signal sent by the VoIP-GW.
The signal waveform at this time is shown in
Fig. 5.
2.1.5 Cause of fault
Given that all incoming-call responses and disconnect operations were normal up to the analog-interface section between the VoIP-GW and PBX equipment, we surmised that a problem existed on the PBXVol. 12 No. 8 Aug. 2014

Call-responsetime
3/07T15:04:37
3/07T14:14:08
3/07T13:59:38
3/07T13:26:52
3/05T16:48:34

Disconnect
time
3/07T15:04:37
3/07T14:14:09
3/07T13:59:39
3/07T13:26:52
3/05T16:48:35

Line
A1
A1
A1
A1
A1

Disconnect
source
G=200
G=200
G=200
G=200
G=200

Within 1 s
Line
A: Analog
1: Line number

Disconnect source
G: This equipment
200: Normal disconnect

Fig. 3. Excerpt of VoIP-GW call log.

side. We considered, for example, that a defective
hook switch on a specific extension phone to the PBX
could cause the line to disconnect when responding toan incoming call.
2.1.6 Countermeasure and effect
To further troubleshoot this fault, we decided toequip the PBX with a function for saving and managing the call history, which would enable us to collectand analyze data and thereby identify the extension
Practical Field Information about Telecommunication Technologies

CallCalloriginating terminating
side
side

Call initiation
Call termination

Disconnect by
call-terminatingside within 1 s

Fig. 4. Capture data (packet sequence) at time of fault occurrence.

Voltage (DC)0between
L1–L2StandbyInterrupted
ringing (IR)Respond toincoming signal
disconnect(line released)

Fig. 5. Respond/disconnect waveform at time of incoming call.

phone of the PBX that was disconnecting the line
when responding to an incoming call. The results oftroubleshooting after implementing this countermeasure showed that the cause of this fault was an operational error by the customer of this PBX. In otherwords, the cause of this fault lay on the PBX side as
we had surmised.
2.1.7 Summary
In this inspection, we collected and analyzed theVoIP-GW call log and inferred that equipment positioned below the VoIP-GW was disconnecting thecalls. Although checking the analog-interface intervalwith instrumentation normally used in fault troubleshooting presents some difficulties, checking the logs
of various types of equipment is relatively easy andmakes for a useful and important fault-troubleshooting technique.
2.2 N
 o ringing sound when the PBX receives an
outside call
2.2.1 Equipment configuration
This configuration was the same as that in the fault
case described in 2.1.


2.2.2 Fault description
After the analog line was changed over to Hikari
Denwa, sometimes no ringing would occur at thetime of an incoming call even though the caller could
hear a ring sound. It had already been confirmed that
this would not occur if the IVR equipment were disconnected.
2.2.3 Inspection method
After confirming the occurrence of no incomingcall ringing in an on-site incoming-call connection
test, we configured some test equipment and conducted a reproducibility experiment. This configuration is shown in Fig. 6.
a)	In this reproducibility experiment, we monitored signals in the analog-interface section
between the VoIP-GW and PBX equipmentusing an oscilloscope while varying the resistance using a variable resistor in place of the
IVR equipment.
b)	We examined the conditions under which no
ringing occurred when a call came in from theoutside.

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Practical Field Information about Telecommunication Technologies

3 lines

Branch connection

Hikari Denwa
ONU

VoIP-GWPBX equipment
Extension phones
Oscilloscope

Variable
resistor

Fig. 6. Configuration of test equipment.

Voltage(DC)
between
L1–L2

Unstable potential
0

About –28 V
About –48 V
On-hook(disconnect
release)StandbyStandbyFig. 7. Waveform depicting unstable potential (when DC resistance between L1–L2 is 0.62 MΩ).

2.2.4 Inspection resultsa)	Signal monitoring in the analog-interface section revealed the following. If the value of DC(direct current) resistance between the L1–L2
lines at the time of circuit release happened tobe less than 0.74 MΩ, the potential between
L1–L2 would become unstable, fluctuating
roughly between –48 V and –28 V directly after
the on-hook operation*. The waveform at thistime is shown in Fig. 7.
b)	We confirmed that no IR signal would be issued
if an incoming-call polarity reversal occurred
while the L1–L2 potential in the analog-interface interval was unstable. The waveform at
this time is shown in Fig. 8.
2.2.5 Cause of fault
Specifications of the VoIP-GW installed on thecustomer’s premises stipulated various electrical conditions with respect to branch connections, so wechecked whether the customer’s equipment setup
conformed to those conditions. One of the conditions
was that the value of DC resistance between L1–L2
was to be 1 MΩ or greater, but we found from measurements that the value was only 0.6 MΩ.
We therefore surmised that VoIP-GW operation
Vol. 12 No. 8 Aug. 2014

Voltage(DC)0
between
L1–L2Calling state
on-hookStandbyPotential isunstable

Incoming
call

No IR

Fig. 8. W aveform at time of incoming call with no ringing
sound.

would be unstable and that this fault would occur
since the stipulated conditions for branch connections
were not being observed.

*

Potential was stable when using another analog-interface circuit.

Practical Field Information about Telecommunication Technologies

2.2.6 Countermeasure and effect
The countermeasure that we implemented to keep
DC resistance between L1–L2 at 1 MΩ or greater andto prevent this fault from occurring was to install aswitching device instead of branch connections andto apply a switching method to be used in the PBX
and IVR equipment.
2.2.7 Summary
We surmised that no ringing occurred when receiving calls from the outside since branch-connection
conditions stipulated in the specifications of VoIPGW equipment installed after the change from ananalog line to Hikari Denwa were not being
observed.



3. Conclusion
This article introduced two case studies of faults
occurring in an IP phone circuit accommodating a
PBX via a VoIP-GW. The first case was solved byanalyzing a call log and the signals/packets in theanalog-interface/Ethernet sections. In the second
case, investigating the customer’s network system todetermine whether it satisfied the required specifications led to the solution. To achieve these troubleshooting results, it is necessary to be familiar withanalog and IP technologies as well as the equipment
or system requirements. With current technologies, aswitchover to an analog interface can occur by using
a VoIP-GW when accommodating a PBX in an IP
phone circuit, so it is essential that knowledge oflegacy systems in addition to that of IP systems bebrought to the troubleshooting process.

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External Awards
Spectroscopy & Innovation Award
Winner: Yuko Ueno, NTT Basic Research Laboratories
Date: May 29, 2014
Organization: Spectroscopy & Innovation Consortium
For “Introduction of My Research Career at NTT R&D Center”.
The lecture discussed applications of spectroscopy in the industrial field.
Best Paper Award
Winner: Akisato Kimura, NTT Communication Science Laboratories; Ryo Yonetani, The University of Tokyo; Takatsugu Hirayama,
Nagoya University
Date: June 11, 2014
Organization: IEICE-ISS (Information and Systems Society of The
Institute of Electronics, Information and Communication Engineers)

For “Computational Models of Human Visual Attention and Their
Implementations: A Survey”.
We humans are easily able to instantaneously detect the regions ina visual scene that are most likely to contain something of interest.
Exploiting this pre-selection mechanism called visual attention forimage and video processing systems would make them more sophisticated and therefore more useful. This paper briefly describes various computational models of human visual attention and their development, as well as related psychophysical findings. In particular, ourobjective is to carefully distinguish several types of studies related tohuman visual attention and saliency as a measure of attentiveness,and to provide a taxonomy from several viewpoints such as the main
objective, the use of additional cues, and mathematical principles.
This survey finally discusses possible future directions for research
into human visual attention and saliency computation.

Papers Published in Technical Journals andConference Proceedings
Giving Context to Sounds through Mediation of PhysicalObjects
S. Sato, M. Takahashi, and M. Matsuo
Proc. of The 2013 ACM International Joint Conference on Pervasive and Ubiquitous Computing (UbiComp 2013), Session of Poster,Demo, & Video Presentations, pp. 91–94, Zurich, Switzerland, September 2013.
We describe the concept of and approach for combining conceptual information produced by humans and data that convey situationsof the real world without any modification or interpretation, which
can be thought of as a method for bridging the web and the real world.
We conducted an experiment to validate our concept by making associations between everyday topics or situations and their characteristic
sounds. We discuss the preliminary results obtained in the experiment.

An Evaluation of Method for Encouraging Participation
H. Kawasaki, A. Yamamoto, H. Kurasawa, H. Sato, M. Nakamura,and R. Kakinuma
Proc. of UbiComp 2013, Session of 2nd ACM International Workshop on Mobile Systems for Computational Social Science, pp.
883–890, Zurich, Switzerland, September 2013.
Much attention is being focused on participatory sensing, in which
real-world data are collected using personal mobile devices as sensor



nodes to sense various conditions of the world we live in. In participatory sensing, there is a problem in that the supply of data is insufficient if users are not motivated to participate in sensing services. We
previously proposed Top of Worlds, a method for encouraging user
participation by presenting rankings in multidimensional hierarchicalsets. In this paper, we describe the development of a ranking system
and a real-world evaluation to confirm that Top of Worlds can encourage user participation.

Maximum Likelihood Factor Analysis with a Large Numberof Missing Values
K. Hirose, S. Kim, Y. Kano, M. Imada, M. Yoshida, and M. Matsuo
Proc. of ERCIM 2013 (The 6th International Conference of the
ERCIM WG on Computational and Methodological Statistics), pp.
585–612, London, England, December 2013.
We considered the problem of full information maximum likelihood (FIML) estimation in a factor analysis model when a majorityof the data values are missing. The expectation-maximization (EM)algorithm is often used to ﬁnd the FIML estimates, in which the missing values on observed variables are included in complete data.
However, the EM algorithm has an extremely high computational
cost when the number of observations is large and/or plenty of missing values are involved. We propose a new algorithm that is based on

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

the EM algorithm but that efﬁciently computes the FIML estimates.
A signiﬁcant improvement in the computational speed is realized by
not treating the missing values on observed variables as part of thecomplete data. Our algorithm is applied to a real data set collectedfrom a web questionnaire that asks about ﬁrst impressions of human;almost 90% of the data values are missing. When there are many
missing data values, it is not clear if the FIML procedure can achieve
good estimation accuracy even if the number of observations is large.
In order to investigate this, we conduct Monte Carlo simulations
under a wide variety of sample sizes.

Dynamic Load-distribution Method of uTupleSpace Datasharing Mechanism for Ubiquitous Data
Y. Arakawa, K. Kashiwagi, T. Nakamura, and M. Nakamura
IEICE Trans. on Information and Systems, Vol. E97-D, No. 4, pp.
644–653, April 2014.
We propose a new load-distribution method using a DHT (distributed hash table) called the dynamic-help method. The proposed
method enables one or more peers to handle loads related to the samehash value redundantly. This makes it possible to handle the large
load related to one hash value by distributing the load among peers.
Moreover, the proposed method reduces the load caused by dynamic
load-redistribution. Evaluation experiments showed that the proposed method achieved sufficient load-distribution even when theload was concentrated on one hash value with low overhead. We also
confirmed that the proposed method enabled uTupleSpace to accommodate the increasing load with simple operational rules stably andwith economic efficiency.

Evaluating Translation Quality with Word Order Correlations
T. Hirao, H. Isozaki, K. Sudoh, K. Duh, H, Tsukada, and M.
NagataJournal of Natural Language Processing, Vol. 21, No. 3, pp. 421–
444, June 2014.
Automatic evaluation of machine translation (MT) quality isessential to develop high-quality MT systems. Various evaluation
metrics have been proposed, and among them, BLEU is widely usedas the de facto standard metric. However, the previous methods havesome problems. BLEU does not care about global word order, andthis severe mistake is not penalized very much. In order to consider
global word order, this paper proposes a lenient automatic evaluation
metric based on rank correlation of word order. By focusing on only
words common between the two translations, this method is lenientwith the use of alternative words. The difference of words is measured by the precision of words, and its weight is controlled by aparameter. When the proposed method was applied using submissions of NTCIR-7 & 9’s Patent Translation task, it outperformed
conventional measures in terms of system level comparison.

Automatic Vocabulary Adaptation Based on Semantic andAcoustic Similarities
S. Yamahata, H. Masataki, Y. Yamaguchi, A. Ogawa, O. Yoshioka,
and S. Takahashi
IEICE Trans. on Information and Systems, Vol. E97-D, No. 6, pp.
1488–1496, June 2014.
Recognition errors caused by out-of-vocabulary (OOV) words leadto critical problems when developing spoken language understanding

Vol. 12 No. 8 Aug. 2014

systems based on automatic speech recognition technology. Automatic vocabulary adaptation is an essential technique to solve these
problems. In this paper, we propose a novel and effective automatic
vocabulary adaptation method. Our method selects OOV words fromrelevant documents using combined scores of semantic and acoustic
similarities. With this combined score that reflects both semantic andacoustic aspects, only necessary OOV words can be selected without
registering redundant words. In addition, our method estimates probabilities of OOV words using semantic similarity and a class-based
N-gram language model. Experimental results show that our method
improves OOV selection accuracy and recognition accuracy of newly
registered words in comparison with conventional methods.

Creating Stories from Socially Curated Microblog Messages
K. Duh, A. Kimura, T. Hirao, K. Ishiguro, T. Iwata, and A. Yeung
IEICE Trans. on Information and Systems, Vol. E97-D, No. 6, pp.
1557–1566, June 2014.
Social curation is characterized as a human-in-the-loop and sometimes crowd-sourced mechanism for exploiting social media as sensors. Although social curation web services such as Togetter, Naver
Matome, and Storify are gaining popularity, little academic researchhas been done to study the phenomenon. In this paper, our goal is toinvestigate the phenomenon and potential of this new field of social
curation. First, we perform an in-depth analysis of a large corpus of
curated microblog data. We seek to understand why and how people
participate in this laborious curation process. We then explore new
ways in which information retrieval and machine learning technologies can be used to assist curators. In particular, we propose a novel
method based on a learning-to-rank framework that increases thecurator’s productivity and breadth of perspective by suggesting
which novel microblogs should be added to the curated content.

Probing the Time Course of Head-motion Cues Integration
during Auditory Scene Analysis
H. Kondo, I. Toshima, D. Pressnitzer, and M. Kashino
Frontiers in Neuroscience, Vol. 8, No. 6, Article 170, June 2014.
We showed that motor cues had a different time course comparedto acoustic or subjective location cues; motor cues impacted perceptual organization earlier and for a short time than other cues, withsuccessive positive and negative contributions to auditory streaming.
An additional experiment controlled for volitional control components, and found that arm or leg movements did not have any impact
on scene analysis.

Mechanical Resonance Characteristics of a Cylindrical
Semiconductor Heterostructure Containing a High Mobility Two-dimensional Electron Gas
H. Okamoto, W. Izumida, Y. Hirayama, H. Yamaguchi, A. Riedel,and K.-J. Friedland
Physical Review B, Vol. 89, 245304, June 2014.
We investigate the mechanical resonance characteristics of semiconductor rolled-up tubes containing a high-mobility two-dimensional electron gas (HM2DEG) by optical and electrical means. The
observed mode frequencies are in an excellent agreement with thetheoretically calculated frequencies for the ground bending andexcited bending and axial modes. The effect of the curvature is toincrease the frequencies of the ground bending modes and the axialPapers Published in Technical Journals and Conference Proceedings

wave modes, while decreasing the frequencies of the first excited
bending modes. We find significant splitting of the bending and twisting modes by the residual stress effects due to axial shear relaxationin z-dependent modes. The HM2DEG interacts with the mechanicalmotion due to Eddy currents and embedded impedances. A prominent asymmetry appears in the vibration amplitude with respect to thedirection of the magnetic field. This originates from the broken symmetry of the HM2DEG on the curved surfaces.

Single-electron Thermal Noise
K. Nishiguchi, Y. Ono, and A. Fujiwara
Nanotechnology, Vol. 25, No. 27, June 2014.



We report the observation of thermal noise in the motion of single
electrons in an ultimately small dynamic random access memory(DRAM). The nanometer-scale transistors that compose the DRAM
resolve the thermal noise in single-electron motion. A complete set offundamental tests conducted on this single-electron thermal noiseshows that the noise perfectly follows all the aspects predicted bystatistical mechanics, which include the occupation probability, thelaw of equipartition, a detailed balance, and the law of kT/C. In addition, the counting statistics on the directional motion, i.e., the current,of the single-electron thermal noise indicate that this noise can be
described as hot noise as well.

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