Evolution of the DISN-Pacific Towards an Integrated ATM Infrastructure

Evolution of the DISN-Pacific Towards an Integrated ATM Infrastructure

Ferial El-Mokadem, Ph.D.

The MITRE Corporation Reston, Virginia

J. Allen Geraci

Defense Information Systems Agency Reston, Virginia

Abstract- The Defense Information Systems Agency (DISA) is currently upgrading the Defense Information System Network (DISN) in the Pacific into an operational wide area network service based on Asynchronous Transfer Mode (ATM) technology. The fielding of ATM technology in the DISN Pacific will adhere to DISA established system specifications, which are based on the ATM Forum and ITU-T standards. The transition to ATM will provide high bandwidth information transfer for all of the day-to-day business transactions for DOD users. The DISN-Pacific transition to an integrated ATM infrastructure is scheduled to be completed in three defined phases: near-term, mid-term, and far-term. Each phase will encompass a series of discrete steps or enhancements that together will form a single, integrated infrastructure of systems and services. This paper provides information on the progress of planned activities for realizing the transition of the DISN-Pacific into an integrated infrastructure that will contribute to the end goal of a worldwide ATM network across DISN.

I. INTRODUCTION

The Pacific theater served by the DISN-Pacific is characterized by great distances between major regions/land areas separated by water that include Alaska, Hawaii, mainland Japan, Okinawa, Korea, and Guam. It also includes several strategic locations in the Pacific where there is a significant Department of Defense (DoD) presence. The most significant of these locations include Kwajalein, Johnston Island, Diego Garcia, Singapore, Wake Island, and Australia. The telecommunications infrastructure in the DISN-Pacific is currently composed of various systems that provide a variety of telecommunications services to DISN users, including voice, data, video and message services. DISN services are provided using a combination of DoD-owned and operated network components, as well as leased (commercially provided) trunk and access circuits that are derived from a variety of transmission resources. Existing common user systems/services include the following:

Defense Switched Network (DSN)

Defense Red Switch Network (DRSN)

Secret Internet Protocol Router (IPR) Network (SIPRNET)

Non-secure Internet Protocol Router Network (NIPRNET)

Joint Worldwide Intelligence Communications System (JWICS)

Automatic Digital Network (AUTODIN)

Defense Message System (DMS)

Pacific Video Teleconferencing Network (PACVTC)

Mobile Satellite Service (MSS)

The management and/or control of these systems are performed at the local, regional, and global level. The global DISN network control is centralized under the DISA Global Network Operations and Security Center (GNOSC) in Arlington, Virginia, with day-to-day management of the DISN-Pacific being performed by the Pacific Regional Network Operations and Security Center (RNOSC) at Wheeler Army Airfield in Hawaii.

II. OVERVIEW OF DISN-PACIFC ATM INFRASTRUCTURE

The existing DISN-Pacific topology is being upgraded into an integrated, responsive, and optimized infrastructure to meet the projected growth in telecommunications requirements for the Warfighter. The integrated infrastructure will provide DISN long-haul switching and bandwidth management services using government-owned ATM Backbone Switches/Bandwidth Managers (BS/BWMs) interconnected by commercial transmission services and/or government facilities. ATM Service Delivery Nodes (SDNs) located at bases/posts/camps/stations across the Pacific will provide direct DISN services to customers served by each SDN. The ATM SDNs will provide service-unique interfaces and adaptation for customer legacy systems for transport across the DISN ATM infrastructure. Adaptation is accomplished through various interworking functions (IWFs) and support of ATM adaptation layer standards. ATM SDNs will be established in accordance with technical standards and specifications published by DISA [1]. The key architectural concepts that apply to the DISN-Pacific transmission infrastructure are summarized below.

A. Backbone Transmission Services

The backbone network will be designed to the maximum extent possible in a ring configuration with alternate paths provided to enable quick recovery from faults. DS-3 links, based on Plesiochronous Digital Hierarchy (PDH), will be used in the early implementation phase to interconnect the ATM backbone switches. 3 and higher (12, and OC-48) links based on the Synchronous Optical Network (SONET)/Synchronous Digital Hierarchy (SDH) standards will be utilized in later implementation phases to satisfy

demands for higher bandwidth as more SDH-capable submarine fiber optic cable capacity becomes commercially available in the Pacific region. ATM backbone switches will have the capability to support SONET/SDH automatic protection switching (APS) to work hand-in-hand with automated restoration in the modern SDH network. Fig. 1

illustrates the projected connectivity for the DISN-Pacific fiber-based backbone transmission infrastructure, for fiscal year (FY) 2002, extending from the CONUS to Korea, and traversing Alaska, Hawaii, mainland Japan, Okinawa, and Guam.

Fig. 1. DISN-Pacific Projected Fiber-Optic Based Connectivity for FY 02

Satellite services will also be utilized to provide connectivity and access to DISN backbone services for locations in the Pacific that do not have direct, local access to the SDH-based fiber optic cable network. The satellite connectivity will also provide a degree of backup for the SDH-based backbone network. The DISN-Pacific infrastructure (fiber optic cable and satellite) will be sized based on validated bandwidth requirements, to include projected surge requirements for support of military operations. It will evolve toward centralized provisioning and network management services for terrestrial and submarine fiber optic cable and satellite bandwidth resources.

B. Access Transmission Configuration

ATM SDNs will concentrate demands for transmission bandwidth and multiplex/allocate them onto DS-1, DS-3, OC-3, or higher links between bases/posts and ATM backbone nodes. ATM SDNs will concentrate demands for

transmission bandwidth and multiplex/allocate them onto DS 1, DS-3, OC-3, or higher links between bases/posts and ATM backbone nodes. Where required, two independent or dual access routes between ATM SDNs at bases/posts and ATM backbone nodes will be provided to support critical availability requirements. Access transmission between customers and ATM SDNs will be provided by the on-base infrastructure and will be part of the sustaining base block of the DISN-Pacific. Access from remote locations to the nearest SDN will normally use commercial leased circuits or services when available and cost-effective. In other cases, military systems will be used. Unless deployed forces are located where they have immediate local access to the DISN infrastructure, access to deployed users will be via a military satellite link to a Standardized Tactical Entry Point (STEP) normally collocated with an SDN, as illustrated in Fig. 2.

Fig. 2. ATM SDN Access Configuration III. DISN-PACIFIC MIGRATION STRATEGY

The migration of the DISN-Pacific from the current telecommunications systems/networks to the integrated ATM infrastructure will be achieved gradually to minimize risks to existing applications and network services. The following three phases are defined.

A. Near-Term – FY 99-01

The Near-Term phase includes on-going incremental systems upgrades that have already begun in the Pacific region and interim operational service capabilities that will generally take place in the FY 00-01 timeframe. During this phase, the major focus will be placed on establishing the ATM backbone transport network and verifying its operation.

B. Mid-Term – FY 02-04

The Mid-Term phase includes the deployment of the SDNs to base/post/camp/station locations across the Pacific and upgrading the backbone transmission connectivity to OC-3 or greater. During this phase, the major focus will be placed on the transition of DISN services (i.e., voice, data, and video) from the legacy systems to the ATM infrastructure while ensuring uninterrupted services to users.

C. Far-Term – Beyond FY 04

The Far-Term phase will complete the DISN-Pacific transition to the envisioned seamless architecture in which all

voice, data, video, and imagery services are fully integrated into the worldwide DISN ATM infrastructure.

IV. INTEGRATION OF DISN SERVICES/SYSTEMS WITH ATM

The ultimate goal of the ATM infrastructure is to provide an integrated network for all DISN services to take advantages of the bandwidth and quality of service capabilities offered by ATM. Support of existing DISN services on the ATM infrastructure will be provided through the interworking functions (IWFs) that are necessary to adapt legacy services for transport across the ATM infrastructure. DISA published technical specifications and standards for IWFs [1], that effectively present standards-based interface for all required DISN services using a mix of ATM adaptation layers (AALs). The IWFs may be resident in a DISA-provided SDN ATM switch or a user-provided switch that then connects to the SDN. DISA is planning to achieve the transition of DISN services from existing systems into ATM within the next five years. The plan is to introduce these systems into the ATM infrastructure in a phased approach that protects the investment in existing systems and minimizes disruptions to user services. The evolution of DISN services from the year 1999 to the year 2004 is outlined in the following subsections.

A. Data Services

The current DISN data services are the NIPRNET and the SIPRNET. Although both networks provide different levels

STEP JTF User ATM Switch Base ATM Classified Voice, Video, Data Premise Router

Base

STEP = Standardized Tactical Entry Point JTF = Joint Task Force

DISN ATM SDN MFS or Base Switch User ATM Switch

of security classifications, they have similar network architectures. Both networks interconnect geographically dispersed LANs via IP addressing and routing structures.

The growing aggregate demands of DoD users, generally in the areas of LANs use and client-server applications will prompt the migration of data services into ATM. In the near-term, support of DISN data services will be based on implementation of LAN Emulation version 1.0 (LANE v1.0) services for interworking between the NIPRNET and SIPRNET LANs and the ATM network. LAN emulation essentially hides the ATM network from the legacy LANs by emulating LAN behavior, so that LAN-based devices can continue to use existing LAN based protocols over ATM networks without requiring any changes to the applications. Similar LANE services will also be used to support gateways to DISN-CONUS, DISN-Europe, the Internet, and the Joint Interconnection Service (JIS).

Each DISN ATM Pacific site supporting a NIPRNET node will have a distributed LAN Emulation Configuration Server (LECS) configured on the ATM switch. The LECS will provide initial information on the Emulated LANs (ELANs) that the LAN Emulation Client (LEC) may join. The LEC configured on the Powerhub will provide physical interface to Ethernet LAN, and provide data forwarding and address resolution (IP to ATM). Two DISN Pacific locations will be chosen to provide the LAN Emulation Server (LES) and a Broadcast Unknown Server (BUS). The LES registers and resolves MAC addresses to ATM addresses for the Emulated LAN. The BUS services connectionless network traffic types such as broadcast, multi-cast, and unknown uni-cast in the connection-oriented ATM environment. Fig. 3 illustrates the components for the Pacific NIPRNET ELAN.

Fig. 3. Pacific NIPRNET ELAN Components

By the year 2000, some users will begin migrating from LANE v1.0 to LANE v2.0 or Multiple Protocol over ATM (MPOA). LANE v2.0 extends LANE v1.0 and allows greater operational flexibility, reliability, and performance. MPOA offers advanced networking functions, such as "cut-through routing," which will substantially improve user performance

while reducing network overhead. MPOA is currently undergoing risk reduction and integration testing at various Government and commercial facilities and is expected to be introduced into DISN services beginning in FY 1999. As MPOA becomes stable and commonly available, it will begin to perform most of the internetworking functions currently done with LANE.

C

B

D ATM

Switch

Site A Site B

Broadcast and Unknown Server (BUS)

Router Router PowerHub (LEC) PowerHub (LEC) Pacific NIPRNET ELAN

LANE Emulation Server (LES) LANE Emulation Configuration Server (LECS)

A C B D ATM Switch ATM Backbone

B. IDNX Services

DISA plans to replace the DISN IDNXs with ATM cell multiplexers to take advantage of ATM dynamic bandwidth allocation capabilities. ATM cell multiplexers are expected to replace the majority of the DISN Pacific backbone IDNX infrastructure by FY 02-03. The ATM cell multiplexers will support various types of service interfaces for voice, data, and video, and will provide circuit emulation service IWFs for mapping the Time Division Multiplexed (TDM)-based user traffic into cell-based streams for transport across the ATM network. To simplify the provisioning of end-to-end circuit emulation service in a large network environment such as the DISN-Pacific, DISA’s goal is to use cell multiplexer equipment that support the Soft Permanent Virtual Circuit (SPVC) signaling functionality and are manageable by the DISN ATM Network Management System (AMS). The SPVC functionality eliminates the need for hop by hop provisioning by allowing the automatic establishment, termination, and restoral of emulated circuits using the same basic signaling protocols that are used for Switched Virtual Circuits (SVCs).

C. Voice Services

Voice services represent perhaps the greatest challenge to the ATM network as an integrated backbone infrastructure. Traditional Plain Old Telephone Service (POTS) has evolved over a century to provide a globally accepted suite of functions and features that raises the level of expectation for Voice Telephony over ATM (VTOA). The current methodology for transitioning the Defense Switched Network (DSN) voice services to ATM is described in the following paragraphs.

The intermediate capability is to replace the TDM-based inter-switch trunks (ISTs) with Permanent Virtual Circuits (PVCs) using both structured and unstructured T1-to-ATM interworking. This approach will be done in limited locations because transport of voice as Constant Bit Rate (CBR) traffic requires more bandwidth than is necessary in TDM and requires full-time capacity allocation across the ATM network, eliminating any potential savings from statistical bandwidth sharing.

The final voice capability will use Variable Bit Rate real-time (VBR-rt) virtual circuits in conjunction with voice compression and silence suppression for efficient transport of voice traffic across the ATM network. The implementation of VBR voice in the DSN-Pacific will be achieved incrementally in line with the pace of technology and availability of standards-based commercial products. Products that implement the recently approved ATM Forum’s VTOA specification “ATM Trunking Using AAL2 for Narrowband Services”, af-vtoa-0113.000, are expected to be available within twelve to eighteen months. Meanwhile,

DISA plans to conduct operational testing in the Pacific in 1999 with pre-standard implementations that use proprietary AAL to carry voice as VBR traffic and provide compression and suppression features. These tests will help DISA gain insight into the dynamics of VBR voice transport across the ATM infrastructure in anticipation of the deployment of the standards-based products when they become available.

It is expected that ATM technology will replace the current tandem functions in the DSN at the multifunction switch level in the far-term.

D. Video Services

Specific plans and schedules for transitioning video services to ATM are not developed but a general vision for transition is described here. Initial video teleconferencing (VTC) capability will be based on DISN Video Services -Global (DVS-G) contract to replace existing systems, with a DISN-Pacific switching hub planned to be located in Pearl Harbor, Hawaii. DVS-G services will provide some of its connectivity through the ATM network, using CBR PVCs between locations. Interworking functions (IWFs) will be used to map VTC synchronous serial data streams to ATM PVCs with a fixed amount of bandwidth.

Future video teleconferencing (VTC) capability will be based on emerging ATM broadband standards in order to satisfy the growing user requirements, such as distance learning and medical imaging. A potential alternative for future implementation of VTC services includes the use of products supporting ITU-T Recommendation H.323. VTC over ATM based on H.323 will enable end-points to establish quality of service negotiated streams using SVCs and AAL5. It is anticipated that this system approach will provide a high conference quality using a VBR-rt service that matches the quality of today VTC systems employing CBR transmission. Commercial VTC products designed to support H.323, revision 2, are expected to be available in year 2000. Future engineering and business case analyses will be needed to evaluate the new VTC technologies and products.

V. CONCLUDING REMARKS

The upgrading of the DISN-Pacific into an integrated ATM infrastructure presents some unique challenges. These include technical and operational issues associated with transmission backbone enhancement to a DS-3, OC-3, and higher rate connectivity, deployment of ATM service delivery nodes, and the integration of user services with ATM to take advantages of the bandwidth and quality of service capabilities offered by ATM.

REFERENCES

[1]