Special Feature

Globalization of Next-generation Core
Network Control Technology
Takumi Ohba†, Tomonori Takeda, Kaori Shimizu,
Ichiro Inoue, and Shigeo Urushidani
Abstract
This article introduces globalization trends in the architecture and protocols for controlling the nextgeneration core network, which will efficiently accommodate various kinds of services and rapidly
growing traffic using both IP (Internet protocol) control technology and photonic technology. It also
describes some activities of NTT Network Service Systems Laboratories in this area as examples: a multilayer service network architecture, L1VPN (layer-1 virtual private network), and GMPLS (generalizedmultiprotocol label switching) interoperability testing.

1. Need for globalization
As the next-generation core network utilizes bothIP (Internet protocol) control technology and photonic technology, a wide range of consensus and cooperation among carriers and vendors is essential toenable the use of advanced equipment of both types
from the world’s markets. The architecture and protocols must be standardized to assure global reachability, which is one of the most significant merits of
the Internet. At the same time, interoperability verification through various channels, such as forums, academic organizations, and interoperability test events,
is also important to assure the connectivity of realequipment that embodies the standards in a multivendor environment. Thus, globalization (i.e., standardization and interoperability verification on theworldwide scale) will play an important role inachieving the next-generation core network and providing service systems economically in the near
future (Fig. 1).
2. Standardization
NTT Network Service Systems Laboratories is† NTT Network Service Systems Laboratories
Musashino-shi, 180-8585 Japan
E-mail: ohba.takumi@lab.ntt.co.jpVol. 2 No. 11 Nov. 2004

active in standardizing the architecture and protocols
for the next-generation core network. The most relevant standards bodies in this area are ITU-T (International Telecommunication Union, Telecommunication Standardization Sector), the IETF (Internet Engineering Task Force), and the OIF (Optical Internetworking Forum). The following subsections explain
the standardization activities for the multilayer service network architecture and L1VPN (layer-1 virtual private network). The former is one example ofarchitecture standardization, which is most significant as the first step in globalization. The latter isexpected to be one of the new services that the nextgeneration core network will provide.
2.1 Multilayer service network architecture
ITU-T Study Group 13 (SG13), which is actively
studying networks and architectures, is studying therequirements and architecture of the next-generation
network (NGN), which makes use of various broadband and QoS-enabled transport technologies andsupports generalized mobility, which will allow consistent and ubiquitous provision of services to users(QoS: quality of service). The multilayer service network architecture is included in draft Recommendation Y.2011 [1] as part of the NGN architecture basedon NTT’s proposals. Consent for Y.2011 to become a
new recommendation was given in June 2004.
Y.2011 shows the multilayer network scenario in37

Special Feature

Network architecture
and protocols- Proposal for
network andservice vision- Support for
protocolinteroperability- Economicalsystem- Interoperability

Standardization
ForumsAcademicorganizations
Interoperability
test events
Various channels- Know-how- Policy

NTT operatingcompanies

Fig. 1. Globalization in Optical+IP technology.

Inter-layer interaction

Intra-layer interaction

Higher-layer control plane
Lower-layer control planeControl plane

User plane

Higher-layer network #1

Higher-layer network #2

Functional entity

Lower-layer network
Control plane equipment

Interaction between entities

Fig. 2. Multilayer network scenario specified in NGN.

the multilayer service network architecture (Fig. 2). It
shows that two functions are required to achieve thecharacteristics of the multilayer service networkarchitecture. They will support cooperation between
layered networks and accommodate various service
networks.
(1) Inter-layer interaction
A coordination function between higher andlower layers is needed to manage and control
multilayer information simultaneously.
(2) Intra-layer interaction
A coordination function between functional enti38

ties in the lower layer (one being common for
multiple higher layers and the other being for anindividual higher layer) is needed to accommodate multiple higher-layer networks, or service
networks, with the single lower-layer network.
It is also necessary to study protocols in standardization bodies, such as IETF or ITU-T, to enableequipment to be implemented. Architecture standardization that includes NTT’s proposals aligns the starting points of various activities for studying protocols
for the multilayer service network architecture.

NTT Technical Review

Special Feature

2.2 Layer-1 virtual private network
L1VPN is a new service being created by combining IP control and photonic technologies (Fig. 3). It
provides super broadband dynamic networking services to large-scale users, such as Internet service
providers (ISPs), by treating a carrier’s optical network as multiple virtual optical networks. L1VPN
also provides network control customization, such as
routing within a carrier’s network or selection of protection levels, by opening the network control tousers by means of generalized multiprotocol label
switching (GMPLS) protocols.
SG13, which is responsible for studying VPNs in
ITU-T, gave consent for Y.1312 [2] as the carrier’s
service requirements for L1VPN and for Y.1313 [3]as the service and network architecture of L1VPN in
July 2003 and February 2004, respectively. NTT
acted as the editor of these recommendations andgreatly contributed to L1VPN standardization. As acarrier, NTT widely promoted the need for L1VPN
service in the marketplace and accelerated technicalstudies for achieving L1VPN.
In addition, protocol enhancements, such as
exchanging VPN-IDs, member information, andtopology information, need to be standardized. As thefirst step, NTT has proposed the framework of
L1VPN to IETF based on discussions in SG13. The
next steps involve studying the applicability of theexisting GMPLS-related protocols and proposing anddiscussing the detailed specifications required for
Each division can manage and operate its VPN as an individual network.

L1VPN.
3. Interoperability verification
Constructing a network with the architecture andservices mentioned above will require a wide range ofadvanced equipment based on both IP and opticaltechnologies. As this equipment will be provided bymultiple vendors, it is becoming more and more
important to verify interoperability of real network
equipment. Furthermore, in the development stage ofstandardization, as in the case of the next-generationcore network, feedback from interoperability verification to standardization activities and cooperation
between them will accelerate progress in related technologies.
UNH-IOL (University of New Hampshire Interoperability Laboratory), ISOCORE, and OIF in theUSA and PIL (Photonic Internet Lab.) [4] in Japanare major bodies performing interoperability verification related to the Optical+IP field. UNH-IOL andISOCORE were founded as interoperability sites toverify protocols, such as ATM and MPLS. Universities in the USA act as neutral organizations to test theinteroperability of multiple vendors’ equipment that
implement multiple carriers’ requirements. The protocols discussed in the standardization bodies, suchas IETF and OIF, are tested in the interoperabilitysites and then modified and implemented as practicalprotocols. PIL aims to promote standard technology
Multiple virtual optical networks are provided on a single optical network.

Control and monitoring functions, such as routing and signaling

VPN #1Division A

VPN #2Division B

Division C
VPN #3
Transport division

Fig. 3. Services of a layer-1 VPN.

Vol. 2 No. 11 Nov. 2004

39

Special Featurefrom Japan and interoperability in the photonic field.
It is supported by the Japanese government.
Many interoperability test events of basic protocols
for the next-generation core network, such as
GMPLS, have been performed through publicdemonstrations and the results have been publishedopenly [5], [6]. It is getting more important to promote interoperability verification at the level of providing real network services.
NTT Network Service Systems Laboratories isproposing test items necessary for the provision ofcarrier-grade services to UNH-IOL and ISOCORE
and is promoting interoperability test events; thus, theLabs., as a carrier, is determining the order of priority of the functions to be achieved in terms of the test
items. In addition, the verification of the interoperability demonstrates the achieved levels of relatedtechnologies.
3.1 GMPLS interoperability testing in UNH-IOL
The first OSRM (optical signaling, routing andmanagement) test event was held from January 12thto 16th 2004 in UNH-IOL. The participants were one
router vendor, three OXC (optical cross-connect)
vendors, two tester vendors, and NTT Network Service Systems Laboratories as a service provider.
NTT Network Service Systems Laboratories led
the development of advanced test items from theviewpoint of providing carrier-grade services. Basedon NTT’s proposals, test items for stable network
operations, such as operation in the event of a control
channel failure and re-routing after a link failure (Fig.
4), as well as basic path setup and release, were performed and the interoperability of equipment frommultiple vendors was checked [7].
Re-routing after a link failure is an essential function for providing network services and there are various ways of doing it. In this event, the simplest
method, which requires minimum implementation
but can bypass the failed link quickly, was verified. In
the tested method, once a link failure occurs, the bestroute is re-calculated and the path is re-established.
Test steps for the link failure re-routing are as follows:
1. Edge node #1 (EN1) requests a fiber-level path
between EN1 and EN2.
• Confirm that the best route, EN1→CN3→CN5→EN2, was selected and the path established on that route.
• Confirm that route EN1→CN1→CN2→EN2
was not selected because CN1 and CN2 have a
different switching capability (lambda level)from the request (fiber level), even though it is athree-hop route and has the same cost as theselected route.
• Confirm that route EN1→CN3→CN4→CN5→
EN2 was not selected because it has one more
hop than the selected route even though theCN1

CN2

1. EN1 requests a fiber-level path.

2. The link between CN3
and CN5 is torn down.

EN1EN2
CN3

Re-routing

CN5

3. EN1 requests a fiber-level path again.
: Lambda-level switch: Fiber-level switch
CN4
Assumptions:- EN1 requests a fiber-level path.
- Each link cost is 1.

EN: edge node
CN: core nodeFig. 4. Re-routing after a link failure.

40

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Special Featureswitching capability matches the request.
2. Tear down the link between CN3 and CN5.
3. EN1 requests a fiber level path again.
• Confirm that the current best route,
EN1→CN3→CN4→CN5→EN2, was selected
and the path established on that route, based on
the route re-calculation without the link between
CN3 and CN5.
• Confirm that route EN1→CN1→CN2→EN2
was not selected because CN1 and CN2 have adifferent switching capability (lambda level)from the request (fiber level) even though it is athree-hop route and has a lower cost than theselected route.
Some issues in the current specifications were clarified through the interoperability testing, and they
were proposed to key persons in the GMPLS study inIETF. They were then discussed in the mailing list of
the IETF CCAMP WG (Common Control And Man-agement Plane Working Group), which is responsible
for GMPLS specifications, and the related specifications were upgraded.
In future, NTT Network Service Systems Laboratories will contribute to the progress of the Optical+IP
field by performing interoperability testing using
more advanced test items or service-related items,
such as L1VPN, and by publicizing the results ofevents through public demonstrations.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]

ITU-T Recommendation Y.2011, “General principles and general reference model for NGNs,” 2004.
ITU-T Recommendation Y.1312, “Layer 1 Virtual Private Network
Generic requirements and architecture elements,” 2003.
ITU-T Recommendation Y.1313, “Layer 1 Virtual Private Network
service and network architectures,” 2004.
http://www.pilab.org/
http://isocore.com/PR/june2004.htm
http://www.oiforum.com/public/pressroom/Demo04-June9.pdf
http://www.iol.unh.edu/consortiums/osrm/

Takumi Ohba

Ichiro Inoue

Senior Research Engineer, Network System
Innovation Project, NTT Network Service Systems Laboratories.
He received the M.S. degree in physics fromthe University of Tokyo, Tokyo in 1993. He
joined NTT the same year and has been studyingATM signaling. Since April 2004, he has beenpromoting globalization of the next-generation
network. He is a member of the Institute of Electronics, Information and Communication Engineers (IEICE).

Senior Research Engineer, Supervisor, Network System Innovation Project, NTT Network
Service Systems Laboratories.
He received the M.E. degree in electrical engineering from the University of Tokyo, Tokyo in
1990. He joined NTT the same year. Since then,his research interests have included telecommunication protocols such as IP and ATM. He has
been active in standardization such as ISO/ISC(as a national committee member), ITU-T, andIETF. He was a visiting researcher at Columbia
University, USA in 1995.

Tomonori Takeda

Shigeo Urushidani

Engineer, Network System Innovation Project,
NTT Network Service Systems Laboratories.
He received the M.E. degree from Waseda
University, Tokyo in 2001. He joined NTT thesame year and has been engaged in research on
the next-generation network architecture, IP
optical network architecture and related protocols. He is a member of IEICE and IEEE.

Senior Manager and Research Group Leader,
NTT Network Service Systems Laboratories.
He received the B.E. degree in electrical engineering and M.E. degree in electronic engineering from Kobe University, Kobe, Hyogo in 1983
and 1985, respectively. He received the Ph.D.
degree in electronic engineering from the University of Tokyo, Tokyo in 2002. In 1985, hejoined NTT, where he engaged in R&D of ATM
switching systems and optical switching systems. In 1992, he moved to NTT Network Engineering Headquarters and began working on
strategic planning and construction of intelligent,broadband, public communication networks. He
is currently involved in R&D of next-generation
IP optical networks at NTT Network Service
Systems Laboratories. He is also a Visiting Professor at the National Institute of Informatics(NII). He received the excellent paper award(1988) and the young engineering award (1990)
from IEICE. He is a member of IEEE.

Kaori Shimizu
Engineer, Network System Innovation Project,NTT Network Service Systems Laboratories.
She received the B.S. degree from the University of Electro-Communications, Chofu, Tokyoin1995. She joined NTT the same year. Currently, she is studying IP optical network architecture
and protocols. She is a member of IEICE.

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