Letters

IPv6 Multi-service Networking
Technologies
Takaaki Moriya†, Hiroyuki Ohnishi, Yasuhiro Seki,and Tadashi Ito
Abstract
This article reports our study on connecting IPv6 (Internet protocol version 6) equipment in user networks to multiple service networks. With the spread of various information appliances and devices, e.g.,
digital televisions and DVD recorders, there is a growing need to provide a way to connect them to network services. This will lead to a lot of equipment using multiple services over the network. Therefore,
in the near future, as IPv6 addresses are widely deployed in a large number of devices, it will be important to consider connectivity models suitable for the future expansion of network access with IPv6.

1. What is a multi-service network?
Today, personal computers (PCs) at home can easily connect to the Internet through broadband accesslike ADSL (asymmetric digital subscriber line) and
FTTH (fiber to the home), which are widely available. The spread of the broadband environment is
expected to increase the number of devices connected to IP networks. PCs and other information appliances and devices should be connected to the network
because they will then be able to utilize various network-based services, such as remote maintenanceand remote control.
Since the Japanese government’s IT Strategy Headquarters adopted the e-Japan strategy in 2003, IPv6
(Internet protocol version 6) technology has been
considered a necessary step to enhance and upgrade
the network infrastructure (IT: information technology). IPv6, which has been developed as the next-generation Internet protocol, has a much larger address
space, security features, automatic network configuration, guaranteed communication quality, and manyother features. It is assumed that IPv6 functions will
be deployed in a large number of devices in homes orbuildings in the near future. Service providers need† NTT Network Service Systems Laboratories
Musashino-shi, 180-8585 Japan
E-mail: moriya.takaaki@lab.ntt.co.jp

Vol. 3 No. 6 June 2005

IPv6 equipment to be controlled flexibly because
they want to deploy attractive services suitable for thecharacteristics of each device. End users, on the other
hand, should connect devices they own to the IP network and simultaneously use various network services depending on each device’s type and purpose.
For example, a user could simultaneously use multiple services via a PC: she could watch a movie athome by accessing a streaming service while monitoring her children via a live camera installed in thekindergarten by a security service provider; she could
also access her company’s internal server in order towork from home. In another example, a home appliance could be controlled by multiple service
providers: a refrigerator could be remotely maintained by the manufacturer and simultaneously controlled remotely by the user to check the amount ofjuice and vegetables via an information appliance service. Thus, large numbers of mixed IPv6 devices suchas computers and sensors with different functions
will be connected. Furthermore, such devices will be
independently connected to the network to obtainappropriate services. To accommodate the increasing
number of IPv6 devices and the variety of services,
we must consider IPv6 connectivity models for discriminating between different types of network use ata particular location and simultaneously connecting
to several destinations.
To meet such requirements, NTT Network Service
55Letters

Systems Laboratories is studying a new platform that
supports easy connection between service networks
and user networks. Service networks are ones belonging to service providers who offer network services,e.g., a security service. User networks are expected to
be an IPv6 environment in a home or apartment building, where a lot of equipment including non-PC
devices will be connected to network services. In ourplatform, we assume the user network is simultaneously connected to multiple service networks. We
examined if such a model is feasible, effective, andpractical. NTT Network Service Systems Laboratories is studying network control technologies to create a platform called a multi-service network (Fig. 1).
This article reports our study on connecting IPv6
equipment in user networks to multiple service networks.
2. Requirements for a multi-service network
2.1 Identifying each device
Every user device must be identified by service networks because remote control and maintenance services are based on push-type communication fromthe service provider to the devices in the user network. IPv4 (Internet protocol version 4), which iscurrently used on the Internet, does not provide
enough global addresses and needs network addresstranslation, so it is difficult for IPv4 to provide pushtype communication from outside the user network.
However, IPv6, which has been developed based on
IPv4 as a protocol for the next-generation Internet,
has a huge number of addresses and can assign a

global address to each device, making it easy for aservice provider to manage user equipment. Thus, themulti-service platform should be based on IPv6 technology because IPv6 has the advantage of easy
deployment of push-type communication service.
2.2 Assigning the IP address space
For service providers in particular, systematic
assignment of network addresses to equipment
belonging to the service network makes it possible tomanage many devices efficiently, considering adevice’s type, location, user name, and so on. If
providers and users independently obtained IP
address spaces from an Internet service provider(ISP) and assigned those IP addresses to the users’
devices, then the service provider would have to manage a lot of “scattered” addresses of equipment
belonging to its service network. It would be troublesome for the service provider to control the user’s
devices flexibly and manage the network.
To avoid this, we need a mechanism for assigning
unified and coordinated addresses to both service anduser networks in order to enable service providers toeasily control equipment in the user network. For
example, a service provider can set static filtering tocontrol access to its server by assigning specificaddresses to the user network.
2.3 Supporting access to multiple service
providers
To achieve simultaneous access to multiple services
and apply push-type service, multiple IP address
spaces of service providers should be assigned to theCompany
intranet
Contents
deliveryHeadquarters

Security
agencyDevicevendorService networks(networks of service providers)IPv6
network

Intranetconnection
service

Contents
deliveryserviceSecurity
service

Remotemaintenanceservice
User network(in homes and buildings)

PCs

Air-conditioners, lights(information appliances)

Security devices,sensors

Fig. 1. IPv6 multi-service network.

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user’s network. Of course, those assigned IP addresses must be properly chosen when a device accesses
the service provider. In addition to the address assignment, access by a device that has not been authenticated and authorized to use its service must be rejected.
3. Solutions
To meet the above three requirements, we havedeveloped two techniques: virtual network construction and multi-path distribution [1] (Fig. 2).
3.1 Virtual network construction
This technique expands part of the service network
into the user network in a virtual manner. It alsoenables secure IPv6 address prefix assignment fromthe service provider to the user network. The technique consists of i) dynamic IPv6 prefix assignment
with authentication and ii) dynamic IPv6 prefix
acquisition and IPv6 prefix advertisement using a service profile. These two functions are achieved as follows.
The user and service networks are connected via a
virtual tunnel, provided between the multi-homing
function (MHF) on the user network and the service
network delegating function (SNDF) on the service
network. MHF and SNDF are expected to be implemented in gateway routers of the user network andservice provider, respectively. The virtual tunnel
between MHF and SNDF is not established until after

3.2 Multi-path distribution
This technique provides simultaneous/selective
access to multiple service networks. It consists of i)an IP routing function based on the source address
and ii) an access control function. These functions arecooperatively achieved by both MHF and the user
equipment, as shown in Table 1. As mentioned in
section 3.1, the user equipment acquires multiple
addresses of service providers. To resolve the hostname in the service provider, a DNS (domain namesystem) proxy is implemented in MHF.
When accessing a host in the service network, auser’s device can select a source address among multiple addresses using the source address selection
mechanism [2] that can choose the longest-matching

Service provider 2Service provider 1

1. Virtual network construction• Dynamic IPv6 prefix assignment
with authentication• Dynamic IPv6 prefix acquisition
and IPv6 prefix advertisement

SNDF has verified that MHF is authorized to accessthe service network. Using the virtual tunnel, SNDF
dynamically assigns part of the provider’s address
space to MHF. Then MHF broadcasts the information
about all of the acquired address spaces, and the user
equipment automatically configures multiple IPv6
addresses by using every prefix announced by MHF.
Dynamic assignment is effective because it prevents
the address space from being used wastefully. In thisway, part of the IP address space of the service network is assigned to a user’s devices so that the service
provider can directly access and control them. This
technique can not only assign a systematic IP address
to each user device, but can also enable the service
provider to identify devices related to its service.

Service provider 3Service networks

IPv6
network

Assigns IPv6 prefix foruser network

2. Multi-path distribution• IP routing function based on
source address• Access control function
Prefix 1
Prefix 1

Each device automaticallyconfigures multiple IPv6
addresses by using prefixes
assigned by service providers.
UE-1

UE-2

Prefix 1

Prefix 1

Prefix 2

Prefix 3

User network

UE-3

UE-4

UE: user equipment

Fig. 2. Multi-service networking technologies.

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Table 1. Deployment of functions.
Deployment of functions
Function

Virtual network
construction

Multi-path distribution

IPv6 basic technology

Userequipment

MHF

SNDF

Dynamic IPv6 prefix assignment
with authentication

—

—

√

Dynamic IPv6 prefix acquisition
and IPv6 prefix advertisement

—

√

√

IP routing based on source address

√

√

—

Access control function

—

√

—

DNS

√

√

—

Tunneling—√√

prefix with respect to the destination address. Whenthe device communicates using the source address
selected by the above function, MHF checks whether
the source address was assigned by the proper service
provider and authorized to use the service. If this verification fails, the communication is filtered out by
MHF. Then, MHF chooses an appropriate route forconnecting the user’s device to an appropriate service
provider.
However, we have not yet concluded that this is thebest approach. In the current approach, access filtering is executed after the device configures the IP
address. Another approach would be to have MHF

refer to the service access policy before the service
network address space is assigned. MHF would
authenticate devices and permit only authenticatedones to configure the IP address. Investigating whichapproach is the best for a multi-service network is a
topic for future study.
4. Implementation
NTT Network Service Systems Laboratories
implemented the MHF/SNDF model and evaluatedboth the feasibility and effectiveness of the technologies. Figure 3 shows the prototype network for eval-Company
intranet
Contents delivery

Headquarters

Security agency

SNDF

SNDF

SNDF

Device vendor

Internet connection

SNDF

SNDF

Security
service

Remotemaintenanceservice

Service networks

IPv6
network

MHF
Contents
delivery service

Intranetconnection
service

Internetconnection

User network

PCs

Air-conditioners, lights(information appliance)
Security devices, sensors

Fig. 3. Prototype network.

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uating our multi-service networking technologies
with five service networks and one of the six user networks, in which IPv6 equipment and applications areallocated. The results show that multiple IPv6
addresses were correctly assigned to user equipment
and the equipment could connect to appropriate service providers depending on type of application. For
example, Fig. 4 shows an ordinary Windows XP
computer in a user network connecting to three service providers: a contents delivery service provider(provider 1) and two remote-camera service
providers (providers 2 and 3). This means that a commonly used PC supporting IPv6 can simultaneously
connect to three services. In fact, by capturing forwarded packets in the user network, we showed thatsource addresses assigned by multiple service
providers were correctly distinguished and chosen.
This evaluation showed that the multi-service networking technologies made it possible to connect
between multiple user networks and multiple service
networks with the required performance. Therefore,
the multi-service network platform is feasible forconnectivity models suitable for the future expansionof IPv6 equipment and services.
Streaming service offeredby service provider 1(prefix: 3100)

Captured packets show thatsource addresses assignedby service providers werecorrectly distinguished.

5. Future work
Our future work will be focused on creating network services with our platform. The multi-service
networking technologies introduced in this reportwere applied to an IPv6 deployment field trial sponsored by the Ministry of Internal Affairs and Communications with the participation of NTT East in
2004. During this trial, which is still continuing, we
will not only examine the feasibility of cooperation
between various service providers, but also continue
to gain knowledge about multi-service networks. In
addition to the functions mentioned in this report, we
will study the functions needed for network service,
such as QoS (quality of service) control for service
providers and applications.
References
[1]

[2]

H. Ohnishi, T. Moriya, T. Jocha, and Y. Seki, “A path selection
method in IPv6 multi-homing network,” IEICE Society Conference,
Sep. 2004.
R. Draves, “Default Address Selection for Internet Protocol version 6(IPv6),” RFC3484, Feb. 2003.

Remote-camera service
offered by service provider 2(prefix: 3200)

Remote-camera service
offered by service provider 3(prefix: 3500)

Fig. 4. Simultaneous connection to three service providers.

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60

Takaaki Moriya

Yasuhiro Seki

Emerging Communication Architecture Project, NTT Network Service Systems Laboratories.
He received the B.E. degree in electronics
engineering and the M.S. degree in frontier informatics from the University of Tokyo, Tokyo in2001 and 2003, respectively. In 2003, he joined
NTT Network Service Systems Laboratories,
Tokyo, Japan. His research interests include
mobile ad hoc networks, ubiquitous networks,
and network measurement technology. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE) of
Japan and the Information Processing Society ofJapan (IPSJ).

Senior Research Engineer, Emerging Communication Architecture Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. degrees in information sciences from the University of Tsukuba,
Tsukuba, Ibaraki in 1988 and 1990, respectively.
In 1990, he joined NTT Switching Systems Laboratories, Tokyo, Japan. He has been engaged in
R&D of switching software for ISDN packet,
ATM, and IMT-2000 systems. His researchinterests are now focused on mobile networking
and ubiquitous networking. He is a member of
IPSJ.

Hiroyuki Ohnishi

Tadashi Ito

Emerging Communication Architecture Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. degrees inmechanical engineering from Waseda University, Tokyo in 1996 and 1998, respectively. In
1998, he joined NTT Network Service Systems
Laboratories, Tokyo, Japan. His research interests include ubiquitous and mobile networks. He
has played an active role in IETF (The Internet
Engineering Task Force) in developing and disseminating mobile networking technology. He
received the Switching System Research Award
from IEICE in 1999. He is a member of IEICE.

Senior Research Engineer, Supervisor, Group
Leader, Emerging Communication Architecture
Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. degrees inmechanical engineering from Keio University,
Tokyo in 1985 and 1987, respectively. Sincejoining NTT Network Service Systems Laboratories in 1987, he has been engaged in researchon ATM-LAN systems and MPLS systems. His
research interests are now focused on ubiquitous
networking. He is a member of IEICE and IEEE.

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