R&D Information“GMPLS Signaling Protocol Interoperability Testin Multilayer Network”—Toward a Global
Standard for the Next-generation Photonic Network

NTT, NEC Corporation, Fujitsu Laboratories Ltd.,The Furukawa Electric Co., Ltd., and Mitsubishi
Electric Corporation are pleased to announce the successful conclusion to the world’s first GMPLS*1 signaling*2 interoperability test using a multilayer network consisting of packet, TDM*3, wavelength, andfiber layers. Given the quality requirements set by theapplication or traffic state, it is possible to select theoptimal communication path from among all possiblepaths that can be established on the multilayer network.
The results of this experiment were reported onMay 22, 2003 in the Workshop held in Kagoshima
University organized by the Technical Group on thePhotonic-Network-based Internet and the TechnicalGroup of Photonic Switching in the Institute of Electronics, Information and Communication Engineersof Japan.
Background and achievements

before. It is impossible to handle all layers in thewhole network systematically, if, for example, oneside uses TDM routing and the other side uses wavelength routing.
To avoid this problem, control software programsfor setting up and releasing paths in the multilayer
network were newly developed and installed in thenetwork control devices of each company. The factthat these control devices can be mutually interconnected is a key factor in the success of the interoperability test that examined path setup of multilayer signaling: a world first. These control devices exchange
signals based on the protocol RSVP-TE*4, extended
to GMPLS, to set up and release multilayer paths on
the multilayer network.
The test setup is shown in Fig. 1. It was designed toreplicate a multilayer network with various kinds ofnetwork equipment including packet routers, electrical connections, optical cross-connects, and opticalswitches for fiber port switching. It provides control

GMPLS enables unified control management of thenetwork layers. In the conventional network, eachlayer network is constructed independently. Conventional technology demands that each is independently controlled by operators specializing in that layer.
For example, in conventional electrical or opticalcross-connects, the network operator uses a terminalof a centralized control device. This device issues
instructions to control cross-connect equipment andhence the setup of TDM or wavelength paths. If thecross-connect equipment supports GMPLS control,then a path is set up by exchanging control packets
between these control devices as well as MPLS
routers. Therefore, a network operator who has
MPLS expertise can manage cross-connects. However, current equipment that supports GMPLS control
simply offers a unified management approach. Eachlayer network must still be managed separately as*1 GMPLS (Generalized Multi-Protocol Label Switching): GMPLS
is a protocol that establishes generalized MPLS in all layers of theIP network. The basic MPLS is a control mechanism that attaches
fixed-length labels to IP packets. The basic functions of GMPLS
were released as a Proposed Standard in February 2003, with registration number RFC 3471-3473. To make it complete and a truly
practical protocol, world-wide efforts are needed to finalize theremaining details and develop protocol code that can be directly
installed in network equipment.
*2 Signaling: An exchange of signals between network equipment
control devices, such as routers and optical cross-connects to setup and release paths. The format of the control signal and the procedure for exchanging control packets are defined in the signalingprotocol.
*3 TDM (Time Division Multiplexing): Transmission technology
using time division multiplexing. Many TDM networks use
SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical Network).
*4 RSVP-TE (Resource ReSerVation Protocol with Traffic Extensions): A signaling protocol. An extension of RSVP (a bandwidthreservation protocol) for MPLS.

Vol. 1 No. 4 July 2003

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GMPLS control signal(RSVP-TE packet)

Route A
path of packetControldevice 1

Select optimal pathbased on application
requirements ornetwork statusControl
device 2

Control
device 3

Control
device 4

Control
device 5Control
device 6NTTNECFujitsu

MELCONTT

Path of TDM
FITELRoute Bpath of TDM

Control
device 7

Path of wavelength
Path of packet

Path of wavelength

NECMELCO

Control
device 8

Control
device 9

FITELPath of optical fiber

FITEL

MELCO

NECControl
device 10

Control
device 11

Control
device 12

FITEL: Furukawa Information Technologies and Telecommunications
MELCO: Mitsubishi Electric Corporation

Fig. 1. Setup of GMPLS signaling experiment in multilayer network.

functionality for both packet and TDM paths usingcontrol devices 1 and 2. Control device 1 can freely
set the packet path of route A and the TDM path ofroute B. Control device 2 on Route A has path control
functions for both packet and wavelength paths. Control devices 2 to 6 are for optical cross-connect control, which sets up the wavelength paths. They newly
set up a wavelength path for the packet path fromdevices 1 to 7. Thus, the setup and release of a multilayer path can be performed by exchanging a control
signal among all the control devices handling a particular layer. Given the quality requirements set bythe application or traffic state, it is possible to selectthe optimal communication path from among all possible paths that can be established on the multilayernetwork.
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GMPLS allows network operations to be unified.
Significant reductions in network operation costs canbe expected because the most economic path can beselected by configuring the optimal configuration of
network resource from among all layers of the network. In addition, novel network services can be created, such as a wavelength-dedicated line thatchanges wavelength path connection points according to user demand. For this reason, GMPLS has been
attracting attention as the base technology of thenext-generation broadband IP network. GMPLS isbeing actively discussed and advanced in international standardization organizations, such as IETF (Internet Engineering Task Force), OIF (Optical Internetworking Forum), and ITU (International Telecommunication Union).
NTT Technical Review

R&D Information

Future plans
This interoperability test was carried out by thePhotonic Internet Lab (PIL)*5. Further interoperability tests with several global companies are planned.

*5 Photonic Internet Lab: Founded in September 2002 to promoteresearch on and development of the next-generation photonic network*6 and encourage global standardization activities, PIL currently consists of seven companies: the five mentioned above plus
Oki Electric Industry Co., Ltd. and Hitachi, Ltd. PIL has twoobjectives: i) to create new control technologies that can be
accepted as international standards and ii) to rigorously test theprotocol software code developed by each company. PIL is promoting R&D on next-generation photonic network technologies(see http://www.jk.ws32.arena.ne.jp). It encourages its members
to submit proposals to global standardization bodies, like ITU-T,IETF, and OIF. It also tests the photonic network control programs
developed by its member companies. Its activities are supportedby the R&D support scheme of the MPHPT (Ministry of PublicManagement, Home Affairs, Posts and Telecommunications) for
funding selected IT activities.

Vol. 1 No. 4 July 2003

For further information, please contact
NTT Science and Core Technology Laboratory
Group
Atsugi-shi, 243-0198 Japan
E-mail: st-josen@tamail.rdc.ntt.co.jp*6 Next-generation photonic network: A network that more fully
reaps the benefits of optical technology, such as optical fiber transmission and wavelength division multiplexing. At present, opticalfiber and wavelength multiplexing are mainly used for point-topoint transmission. The next-generation photonic network
requires effective optical switching technology. Most switches
today are electrical because the few existing optical switches offer
insufficient performance. A high-speed, large-scale network could
be created with advanced all-optical switching.

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