Global Standardization Activities

ATM Forum Activities and NTT’sContributions
Tatsuro Murakami†
Abstract
The ATM Forum was established in 1991 to specify de facto standards for the global communications
market and to promote market awareness and knowledge about technical and commercial developments
utilizing ATM. The forum has three world-wide offices under its board of directors and it has greatly
influenced the ATM market. NTT joined the forum in early 1993 and made many contributions to itsefforts. This article summarizes the forum’s accomplishments and NTT’s contributions.

1. Introduction
The ATM forum [1] was founded in 1991 to makeuniform global de facto standards for ATM and to disseminate them among the world’s major carriers,
expecting ATM technology to be used to provide BISDN and major vendors supplying switches to them.
While the forum studied and specified the basic standards, the number of members increased to over 900
organizations five years after it was founded. From1991 to 1996, the market continued to grow rapidly
and ATM developed its most important basic role: toturn carriers services into B-ISDN-based services. At
the same time vendors who manufactured ATMnodes (e.g., switches, transmitters, and user interface
terminal equipment), competed to gain shares in thismarket while conforming to the proceedings of theforum’s specifications. Due to strong competition in
the market, a wide variety of ATM products had beenreleased in the data communication market by 1997.
Carriers started to implement ATM services on thecommercial level in 1996 using the ATM nodes available. The forum’s standards contributed overwhelmingly to the extensive growth of this market and managed to hold a steady position among ATM commercial technologies with the ITU-T ATM standards atthat time. In 1996, the forum agreed that its de facto† NTT Service Integration Laboratories
Musashino-shi, 180-8585 Japan
E-mail: murakami.tatsuro@lab.ntt.co.jp

88

standards were unique to the world (Anchorage
Accord). This accord accelerated the development
and commercialization of ATM products. This article
summarizes the forum’s activities and NTT’s contributions.
2. Basic technologies of ATM
ATM is a kind of packet transfer method. It uses acell with a fixed length (53 bytes) and relays cell
flows node-by-node as long as there are time slots
available for transfer.
STM (Synchronous Transfer Mode), which is usedfor PSTN (Public Switched Telephone Network) services, is based on time division multiplexing (TDM).
It allocates one time slot in a synchronous frame toone user, so there may be empty time slots that are notallocated to any users. In addition, using a cell with afixed length enables various kinds of multimedia
transfers with different bandwidth to be mixed on aline, that is, many users’ cells can be transferred aslong as empty slots are available in the frames of aTDM line. In other words, we have virtual paths(VPs) and virtual circuits or channels (VCs) on a line.
ATM controls and manages them with the manymechanisms of the ATM nodes and associated operational support system.
As ATM was developed for B-ISDN services, its
standards have a very wide range and strict conformances to provide a variety of carrier services withreliability and high quality as well as conforming toNTT Technical Review

Global Standardization Activities

ITU-T standards (Fig. 1). Tracing the process of theforum studies, the first efforts were directed at making
the basic specifications, which are very important,like UNI (User Network Interface), NNI (Network toNetwork Interface), traffic management, and network
management. Also specified were control signaling
with address and routing, the ATM adaptation layer(AAL) between upper service layers and the ATMlayer, and the physical layer under the ATM layer.
These standards enable node products from different
vendors to be connected to one another correctly,
which has resulted in market expansion. After theAnchorage Accord in 1996, the forum continued towork on extensions of the basic specifications for various applications in combination with other transfer
technologies such as the frame relay, IP-LAN (Internet Protocol Local Area Network), TDM line emulation, existing voice transfer, and IP/MPLS (IP Multi
Protocol Label Switching). All these led up to theforum’s current studies into IP network collaboration.
3. NTT’s contribution and outputs
NTT has contributed overwhelmingly to the‘91

‘92

‘93

‘94

‘95

forum’s activities since joining in 1993. Many of thestandards that have been implemented are NTT-related. The three main ones are described here. First, fortraffic management, NTT joined the studies andcoordinated the standards with our node products.
The ATM node (AHM) was first developed successfully at NTT and we proceeded to develop a series of
ATM nodes with the same standards scheme. Second,
for residential broadband, we proposed an effective
user access method using ATM-PDS (Passive DoubleStar) and contributed positively to its study, based onforum activity, resulting in NTT establishing the standardization consortium called FSAN that brings
together major carriers from around the world in
cumulative standardization policies. As a result of
this, the method that NTT proposed became an ITUT Recommendation. Third, for voice telephony overATM (VTOA), NTT suggested the carrier common
requirement for transferring voice calls packetized
into ATM cells using dedicated lines for compatibility with public network interfaces. Moreover, weaccelerated the study of voice compression, which
was being independently pursued for dedicated lines
and mobile services, to ensure that they comply with‘96

‘97

‘98

‘99

‘00
To ‘02

Establishment
EstUNI

UNI
2.0

UNI
3.0
VBR-nRTUBR
BICI1.0

NNI

Extended Specs Phase

Basic Specs Phase
UNI
3.1
Accordance with CBR
ITU-T (Q.2931)
BICI1.1IISP• PVC-based NNI• Dedicated line emulation• FR-interwork etc.
AAL3/4/5 • Traffic management• NW quality standards
p-mp• NW address plan (ver.1)

BICI2.0

UNI
4.0

Differentiated UBR
VBR-RT UBR with MDCR
GFR
FBATM
FATE

ABR

T M4.0
PNNI1.0

PNNI2.0

AINI

AP & market services support
AAL2
VTOA
VTOA-trunking
MPOA
VPN/H.323

Anchorage Accord
Agreed that the ATM Forum basic
specs are unique de-facto standards
in the global market

WAN support
Voice service
Existing services emulation Multi-Protocolp-mp: Point-Multipoint
SVC: Switched Virtual Circuit (Channel)
PVC: Permanent Virtual Circuit (Channel)
TM: Traffic Management
LES: Loop Emulation Service
FBATM: Frame-based ATM
FATE: FBATM Transport over Ethernet
FAST: FBATM over SONET/SDH Transport
VoDSL: Voice over Digital Subscriber Line

FAST

TM4.1

SVC

AAL1
LANE
L2 services emulation

AAL: ATM Adaptation Layer
BICI: B-ISDN Inter-Carrier Interface
LANE: LAN Emulation
MPOA: Multi Protocol over ATM
VBR-nRT: Variable Bit Rate–non Real-Time
UBR: Undefined Bit rate
CBR: Constant Bit RateIISP: Interim Inter-Switch Signaling Protocol

UNI
4.1

IP support
interwork
LES phase 1
LES phase 2(now studying)

VoDSL/ IP support
IP/MPLS-interwork
PNNI: Private Network-Network Interface
AINI: ATM Inter-Network Interface
MDCR: Minimum Desired Cell Rate
ABR: Available Bit Rate
GFR: Guaranteed Frame Rate
VTOA: Voice &Telephony Over ATM
VPN: Virtual Private Network
MPLS: Multi Protocol Label Switch

Fig. 1. Main activities and outputs of the ATM Forum.

Vol. 1 No. 2 May 2003

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Global Standardization Activities

each other. This suggestion became a short-term ITUT recommendation. In addition, on wireless issues,
NTT joined the study of ‘mobile ATM’ standards,including the implementation of connection-holding
functions like hand-over.
4. Current status
The ATM forum is now proceeding with extensions
and interworking issues with IP/MPLS based on thebasic forum standards. In the telecommunication
market, ATM services and products continue to beprovided but growth has flattened. The major factor
in the market recently has been the emergence of IP
services. Considering all these circumstances, NTTdecided not to renew its membership in the ATM
forum last December because we have completed ourinitial goals: that is, we have contributed to ATM
standardization, fed results back to our R&D products, promoted market awareness, and supported theprovision of various ATM services by NTT groupcompanies. We expect the current ATM services that
our companies are providing to continue smoothly
and become more profitable in the future as a resultof being built around the ATM forum standards inwhich we were involved.

Tatsuro Murakami
Director, NTT Network Service Systems Laboratories.
He received his BS and MS degrees in Physics
from the Tokyo Institute of Technology in 1979
and 1981, respectively. He is part of NTT’s main
R&D efforts and is responsible for leading developments in services and network architectures.
His primary objectives as director include establishing network architectures and service concepts, promoting technology standards, and planning the overall development of network elements and their introduction into the NTT’s service network.

Reference[1]90

http://www.atmforum.com/

NTT Technical Review