United States General Accounting Office

GAO Report to the Congress

January 1995 INFORMATION

SUPERHIGHWAY

An Overview of

Technology Challenges

GAO/AIMD-95-23

GAO United States

General Accounting Office

Washington, D.C. 20548

Comptroller General

of the United States

B-259205 

January 23, 1995

To the President of the Senate and the

Speaker of the House of Representatives

In light of the strategic importance of the information superhighway, we summarized the

socioeconomic, regulatory, and technical issues associated with its development in a

September 1994 report. The enclosed report focuses in more detail on the major technical

issues facing the industry and federal regulators in planning and implementing the

superhighway.

We are sending copies of this report to all Members of Congress; the Secretary of Defense; the

Secretary of Commerce; and the Chairman, Federal Communications Commission. Copies will

also be made available to others on request.

This report was prepared under the direction of Joel C. Willemssen, Director, Information

Resources Management/Resources, Community, and Economic Development Issues, who can

be reached at (202) 512-6253. Other major contributors to this report are listed in appendix V.

Charles A. Bowsher

Comptroller General

of the United States
Executive Summary

Purpose To take advantage of emerging technologies to create, manage, and use

information that could be of strategic importance to the United States, the

administration has launched an ambitious initiative—known as the

National Information Infrastructure program—to guide industry’s

development of the national information superhighway. The Congress,

while sharing the administration’s vision, has been examining what impact

the high stakes race among the major industry players to carve out

portions of the superhighway will have on competition and service

choices.

Because of the importance of the information superhighway, GAO initiated

work to identify the socioeconomic, regulatory, and technical issues

associated with this initiative in detail. GAO summarized these issues in a

prior report.1

 This current report focuses in more depth on the pivotal

technical issues—security and privacy, interoperability, and reliability.

Failure by the private and public sectors to address these challenges could

adversely affect the future of the emerging information superhighway.

Background The administration envisions the superhighway as a seamless web of

communications networks, computers, databases, and consumer

electronics—built, owned, and operated principally by the private

sector—that will put vast amounts of information at users’ fingertips. It

believes that the superhighway, if freed from the constraints imposed by

rigid regulatory regimes, can fundamentally change the way we work,

learn, get health care and public services, shop, communicate, and

entertain ourselves.

While initial versions of some of these advanced capabilities and services

are already provided by the existing infrastructure, albeit at relatively high

cost and low transmission speeds, much remains to be done to achieve the

superhighway’s potential. For example, although some of the services

envisioned for the information superhighway are being provided by the

Internet, various on-line information services, and thousands of electronic

bulletin boards, these services are not ubiquitous, secure, or consistently

user friendly. Building the superhighway will require deploying and

integrating advanced communications technologies with the existing

communications networks, and investing tens of billions of dollars to build

the “on ramps” to connect residential, institutional, and business users.

1

Information Superhighway: Issues Affecting Development (GAO/RCED-94-285, Sept. 30, 1994).

Page 2 GAO/AIMD-95-23 Information Superhighway
Executive Summary

The administration has formed a multiagency group—the Information

Infrastructure Task Force—to articulate a vision for the information

superhighway and to guide its development. The task force is examining a

wide range of technical issues relevant to the development and growth of

the superhighway.

Results in Brief While the structure and services to be offered by the information

superhighway have not yet been determined, several critical technical

challenges are emerging. First, if it is to provide critical communications

services to manufacturing, health care, and other business sectors, the

superhighway must ensure data security and protect users’ privacy.

Because existing public networks are largely unsecured and are vulnerable

to damage from intruders, achieving security and privacy will require

careful and thoughtful design.

Second, the superhighway should provide a “seamless” web of features

and services to users, with thousands of systems and components

interacting, or interoperating, in a way that is transparent to users.

Achieving interoperability will require manufacturers to cooperate with

standards-setting bodies to establish common interfaces and protocols.

Third, to prevent network failures, the superhighway must be reliable,

end-to-end, from users to service providers. Recent outages on the existing

networks that will form the foundation for the superhighway have raised

concerns about achieving this goal.

Principal Findings

Ensuring Security and

Privacy Will Pose a Major

Challenge

A large volume of the information that will traverse the superhighway will

be proprietary or privacy sensitive and therefore will need to be protected.

Unauthorized disclosure, theft, modification, or malicious destruction of

such information could bankrupt a business, interrupt vital public service,

or destroy lives. As it evolves, the infrastructure will likely become a

tempting target for intruders with the technical expertise and resources to

cause great harm. These intruders could include hackers, foreign

governments conducting political and military intelligence operations,

domestic and foreign enterprises engaged in industrial espionage, or

terrorist groups seeking to disrupt our society or cripple our economy.

Page 3 GAO/AIMD-95-23 Information Superhighway
Executive Summary

Significant effort will be needed to define, develop, test, and implement

measures to overcome the security challenge posed by the development of

the superhighway. These measures include identifying the superhighway’s

security and privacy requirements and developing tools and techniques to

satisfy the requirements.

The federal government, because of its extensive experience and expertise

in developing secure networks, could play a leading role in ensuring the

superhighway’s security. However, critics of federal involvement argue

that current federal initiatives represent a danger to civil liberties, and that

individuals should be free to choose the technical means for achieving

information security. As a result, the challenge will be establishing a

reasonable level of consensus among the major players—the government,

the computer and communications industry, the business community, and

civil liberty groups—on how to ensure information security and privacy.

Achieving Interoperability

Is a Critical Goal

An essential goal of the superhighway will be achieving interoperability

among the thousands of networks and components. Such interoperability

is critical for ensuring the delivery of seamless features and services to

users.

Achieving this goal will be difficult because the components and services

of the superhighway will be designed, provided, and maintained by

thousands of suppliers. Further, ensuring interoperability will also require

the development and use of standards for voice, video, data, and

multimedia services. However, many of the standards needed to ensure

the superhighway’s interoperability do not currently exist, while in other

cases, systems, including digital cellular system and some high-speed

optical transmission systems, are being deployed based on ill-defined,

immature, or competing standards. The federal and private sectors are

beginning to deal with certain aspects of network interoperability, such as

the development of industry-wide standards and the establishment of

interoperability test beds.

Network Reliability Is

Emerging as a Key

Challenge

The superhighway will rely on complex hardware and software

components to link thousands of networks serving hundreds of millions of

users worldwide. While these components are beginning to provide a host

of new services, they are also becoming one of the largest causes of

network failures. As fewer and fewer components handle more and more

connections, a failure of one component could cause the loss of service for

Page 4 GAO/AIMD-95-23 Information Superhighway
Executive Summary

several million customers. In addition, the introduction of new

technologies and growth in the number of networks will likely increase

vulnerability. The government and industry have recently taken steps,

including the establishment of the Network Reliability Council and the

Networks Operations Forum, to address these issues.

Recommendations Because this report is intended to serve as an overview of key technical

issues, it makes no recommendations.

Agency Comments GAO provided and discussed a draft of this report with officials from the

Federal Communications Commission, the National Telecommunications

and Information Administration, the Information Infrastructure Task

Force, the National Institute of Standards and Technology, the Department

of Defense, the Advanced Research Projects Agency, and the National

Security Agency. These officials generally agreed with the contents of this

report. GAO incorporated their comments where appropriate.

Page 5 GAO/AIMD-95-23 Information Superhighway
Contents

Executive Summary 2

Chapter 1 

Introduction

10

The Grand Vision of the Information Superhighway 11

Objective, Scope, and Methodology 16

Chapter 2 

Ensuring Security and

Privacy Will Pose a

Major Challenge

18

Networks and Computer Systems Are Increasingly Vulnerable to

Attacks

19

Security Measures Are Critical to Minimizing Risk 20

Federal Role in Security and Privacy Is Subject to Debate 23

Chapter 3 

Achieving

Interoperability Is a

Critical Goal

31

Interoperability Will Be Difficult to Achieve 31

The Federal and Private Sectors Have Initiated Efforts to Address

Interoperability

33

Chapter 4 

Network Reliability Is

Emerging as a Key

Challenge

35

Reliability of the Superhighway Will Be Essential 35

The Government and Industry Are Taking Steps to Address

Reliability

39

Chapter 5 

Conclusions

41

Appendixes Appendix I: Information Infrastructure Task Force Is Addressing

Selected Technical Issues

42

Appendix II: Description of Existing Network Technologies 45

Appendix III: Description of Advanced Technologies 53

Appendix IV: Ensuring the Portability of Telephone Numbers

Poses a Challenge

62

Appendix V: Major Contributors to This Report 65

Glossary 66

Page 6 GAO/AIMD-95-23 Information Superhighway
Contents

Related GAO Products 84

Figures Figure 1.1: Functional Layers of the Information Superhighway 12

Figure 1.2: Telephone, Cable, and Wireless Networks 15

Figure 2.1: Secret and Public Key Encryption Systems 22

Figure 2.2: Tessera Crypto Card 23

Figure 2.3: The Capstone and the Clipper Chips 26

Figure 2.4: Message Encrypted With the Pretty Good Privacy

Encryption System

30

Figure 4.1: Fiber Optic Cable “Dig-up” Accident 38

Figure II.1: A Typical Local Telephone Network 47

Figure II.2: A Typical Cable System Architecture 48

Figure II.3: A Typical Cellular System Architecture 50

Figure II.4: Broadcast and VSAT Satellites 52

Figure III.1: ISDN Architecture 54

Figure III.2: AIN Architecture 56

Figure III.3: B-ISDN Architecture 57

Figure III.4: Low Earth Orbit Satellite System 59

Figure III.5: Broadband in the Local Loop 61

Page 7 GAO/AIMD-95-23 Information Superhighway
Contents

Abbreviations

AIN advanced intelligent network

ARPA Advanced Research Projects Agency

ATM asynchronous transfer mode

B-ISDN Broadband Integrated Services Digital Network

DOD Department of Defense

FCC Federal Communications Commission

GEO geosynchronous Earth orbit

HPCC High Performance Computing and Communications

Hz Hertz

IDEA international data encryption algorithm

IITF Information Infrastructure Task Force

ISDN integrated services digital network

Kbps thousand bits per second

LAN local area network

LEO low Earth orbit

Mbps million bits per second

NANP North American Numbering Plan

NII national information infrastructure

NIST National Institute of Standards and Technology

NSA National Security Agency

OSI Office of Special Investigations

PCN personal communications network

PCS personal communication system

SAC service access code

SONET synchronous optical network

SS7 Signaling System 7

VF voice frequency

VSAT very small aperture terminal

Page 8 GAO/AIMD-95-23 Information Superhighway
Page 9 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

A global technological upheaval, fueled by rapid advances in information

processing, storage, switching, and transmission technologies, is beginning

to blur the lines between computing, telephony, television, and publishing.

This convergence is creating a new breed of information service industry,

and permitting the development of the much discussed National

Information Infrastructure (NII), commonly known as the information

superhighway. The administration envisions the superhighway as a

seamless web of communications networks, computers, databases, and

consumer electronics—built, owned, and operated principally by the

private sector—that will put vast amounts of information at users’

fingertips. It believes that the superhighway, if freed from the constraints

imposed by rigid regulatory regimes, will fundamentally change the way

we work, learn, shop, communicate, entertain ourselves, and get health

care and public services.

Despite the dramatic advances in technology and the changes sweeping

the communications industry, the superhighway’s development is

expected to be slow and arduous. As such, its development should not be

viewed as a cliff that is suddenly confronted, but rather an increasingly

steep slope that society has been climbing since the early communications

networks were established.1

 A national and global information

infrastructure, which will serve as the foundation for the superhighway,

already exists. Telephones, televisions, radios, computers, and fax

machines—interconnected through a complex web of fiber optics, wires,

cables, satellites, and other communications technologies—are used every

day to receive, store, process, display, and transmit data, text, voice,

sound, and images in homes and businesses throughout the world.

However, the information superhighway is expected to offer much more

than separate telephone, data, or video services; it is expected to integrate

these services into an advanced high-speed, interactive, broadband, digital

communications system.2

Some of the advanced capabilities and services envisioned for the

superhighway are beginning to be provided—albeit at a relatively high cost

and at low transmission speeds—by the existing information

1

What it Takes to Make It Happen: Key Issues for Applications of the National Information

Infrastructure, Committee on Applications and Technology, Information Infrastructure Task Force,

January 25, 1994.

2

In digital networks, analog messages (such as voice) are converted to digital signals (ones and

zeroes). Once in digital form, voice, video, graphics, and text can be combined and efficiently stored,

compressed, and transmitted. The capacity of a digital network may be described in terms of the

number of bits that the network can transmit every second. In general, narrowband networks transmit

at rates below 1.5 million bits per second (1.5 Mbps); broadband networks transmit at rates above 1.5

Mbps.

Page 10 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

infrastructure. For example, the Internet—a global metanetwork, or

“network of networks,” linking over 59,000 networks, 2.2 million computer

systems, and over 15 million users in 92 countries—provides many of the

services envisioned for the information superhighway.3

 Similarly, a

growing number of on-line services, such as CompuServe, America Online,

and Prodigy, provide their subscribers with a rich array of information

services. Finally, hundreds of communities across America are served by

electronic bulletin boards dispensing information to hundreds of

thousands of users.

The administration, believing that the technologies to create, manipulate,

manage, and use information are of strategic importance to the United

States, has formed a multiagency group—the Information Infrastructure

Task Force (IITF)—to articulate a vision for the information superhighway

and to guide its development. The task force, chaired by the Secretary of

Commerce, is responsible for addressing a wide range of regulatory and

technical issues related to the information superhighway and for the

coordination of existing federal efforts in the communications area. The

task force is examining, through its committees and working groups, a

wide range of technical issues relevant to the development and growth of

the information superhighway. A more detailed description of the IITF

structure and its activities is presented in appendix I.

The Grand Vision of

the Information

Superhighway

While industry is beginning to build the information superhighway, little is

known about how the superhighway will be structured and what services

it will provide. Nevertheless, a common vision of its capabilities is

beginning to form among policymakers and public interest groups. First,

there is an emerging agreement that the superhighway should be

structured as a metanetwork that will seamlessly link thousands of

broadband digital networks. Second, it should allow a two-way flow of

information, with users being able to both receive and transmit large

volumes of digital information. Third, it should be open, ensuring equal

access for service and network providers. Finally, it should ensure the

security and privacy of databases and users’ communications, and provide

a high degree of interoperability and reliability.

3

Internet users with access to a transmission speed of 56 thousand bits per second (56 Kbps) can

receive digital radio or transmit and receive digital files containing embedded text, voice, video, and

images. However, at current commercial rates, the average fee for attachment to the Internet at 56

Kbps is about $15,000 per year. Users not requiring sophisticated multimedia services may access

Internet for about $25 per month.

Page 11 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

Achieving the grand vision will depend largely on how successfully

industry integrates advanced technologies and capabilities into the various

layers of the information superhighway. To better understand the

integration of advanced telecommunication technologies into the existing

communication infrastructure, we developed a conceptual model of the

information superhighway, as shown in figure 1.1.

Figure 1.1: Functional Layers of the Information Superhighway Mellville: Moby Dick Mellville: Moby Dick Mellville: Moby Dick

Mellville: Moby Dick

Page 12 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

The model presents the following five critical layers—management,

applications, information, networks, and transport—linked with pervasive

security, interoperability, and reliability requirements:

• the transport layer consists of optical fibers, coaxial cable, copper wire,

switches, routers, satellites, and transmitters

• the networks layer consists of thousands of logical networks

superimposed on the transport layer

• the information layer includes databases and electronic libraries

containing text, images, and video

• the applications layer contains software and consumer electronics needed

to access the superhighway’s information and services

• the management layer consists of operations and administrative centers,

emergency response teams, and security services.

Today’s Networks Provide

the Foundation for the

Superhighway

With a few exceptions, such as the recently proposed global satellite

networks, most experts anticipate that the superhighway will be built on

the foundation of the existing communications infrastructure. Over the

years, this infrastructure has evolved into three separate, and frequently

incompatible, communications networks.4

 These are

• the wire-based voice and data telephone networks,

• the cable-based video networks, and

• the wireless voice, data, and video networks.

The wire-based voice and data telephone networks are part of the global

telephone network.5

 The voice networks provide ubiquitous, highly

interoperable, high-speed, and flexible telephone service to millions of

users. The data networks provide high-speed digital data communications

services. The cable-based video networks rely on various approaches to

broadcast a one-way broadband video signal to individual subscribers.

Finally, the wireless networks use a wide range of analog and digital radio

technologies to deliver voice, data, and video services.

The principal shortcoming of the existing communications infrastructure

is its inability to provide integrated voice, data, and video services. Over

4

An additional type of data network—the fiber optic networks used by electric power utilities to

manage their power distribution systems—also exists. These networks may eventually become part of

the information superhighway.

5

Unlike the private networks developed for the exclusive use of one organization, the U.S. common

carrier networks are shared-resource networks that offer communications services to public

subscribers.

Page 13 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

the years, the voice and data networks have evolved separately, with voice

networks relying on circuit switching while data networks largely using

packet switching techniques. Thus, a business user requiring voice, data,

and videoconferencing services may have to use three separate

networks—a voice network, a data network, and a videoconferencing

network. The emergence of multimedia applications and the high

bandwidth applications in health care, industry, education, and business

are beginning to require a network infrastructure capable of supporting

multiple types of information.

The basic architecture of the three types of networks is shown in figure 1.2

(see appendix II for an overview of each of these networks).

Page 14 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

Figure 1.2: Telephone, Cable, and Wireless Networks

Local telephone

company’s central

office

Local telephone

company’s access

tandem switch

Long distance

carrier point

of presence

Large

business

customer

Head end

Amplifiers

Cable

company

Copper

wire

Optical

fiber

Satellite

antenna

Optical

fiber

Optical

fiber

Cellular system

Coaxial

cable

Long distance network

Coaxial

cable

Page 15 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

The communications industry is beginning to introduce several new and

innovative technologies that could enable the superhighway’s developers

to achieve the administration’s vision of the information superhighway.

These technologies include

• narrowband Integrated Services Digital Network (ISDN),

• advanced signaling and intelligent networks,

• broadband ISDN (B-ISDN),

• personal communications networks, and

• broadband in the local loop.

These technologies, described in more detail in appendix III, will help

provide many of the advanced services and capabilities of the information

superhighway. The development of the superhighway will also require the

expenditure of tens of billions of dollars to build the local broadband

“on-ramps” connecting residential, institutional, and business users with

the evolving superhighway.6

 Further, its users are expected to be offered

viable services and information products beyond the much touted 500

channels of high-definition television.7

Objective, Scope, and

Methodology

In light of the strategic importance of the information superhighway, we

identified the socioeconomic, regulatory, and technical issues and

challenges associated with the development of the information

superhighway. Our previous report addressed all three areas.8

 Our

objective in this report is to address in more detail the key technical

issues: security and privacy, interoperability, and network reliability.

To accomplish our objective, we surveyed an extensive body of technical

literature and industry journals, searched and reviewed related documents

from Internet networks, and reviewed postings to various Internet news

groups with interest in telecommunications and information security

issues. To obtain the views of federal officials on the technical challenges

related to the development of the information superhighway, we met with

representatives from the Federal Communications Commission (FCC), the

National Telecommunications and Information Administration, the

Information Infrastructure Task Force (IITF), the National Institute of

6

Cable Television Laboratories estimates that the replacement of the copper wire in the local loop will

cost hundreds of billions of dollars.

7

Many argue that once the industry provides the on-ramps, a rich array of services requiring

interactive, broadband transmission capabilities will be developed. Others believe that the response to

the view “if we build it, they will come” is “yes, but will they bring any money?”

8

Information Superhighway: Issues Affecting Development (GAO/RCED-94-285, Sept. 30, 1994).

Page 16 GAO/AIMD-95-23 Information Superhighway
Chapter 1 

Introduction

Standards and Technology (NIST), the National Science Foundation, the

Department of Defense (DOD), the Advanced Research Projects Agency

(ARPA), and the National Security Agency (NSA). We also met with

representatives of the telephone, cable, and communication industry to

obtain their views on technical issues related to the superhighway.

We conducted our work in Washington, D.C., and vicinity between

September 1993 and October 1994, in accordance with generally accepted

government auditing standards. In addition, we discussed the contents of

this report with representatives of the National Telecommunications and

Information Administration, IITF, FCC, NIST, DOD, ARPA, and NSA, and have

incorporated their comments where appropriate.

Page 17 GAO/AIMD-95-23 Information Superhighway
Chapter 2 

Ensuring Security and Privacy Will Pose a

Major Challenge

Much of the information that will be on the superhighway, including health

care records, business documents, engineering drawings, purchase orders,

or credit card transactions, will be proprietary or privacy sensitive and

must be protected. As it evolves, the superhighway will become an

increasingly tempting target for intruders with the technical expertise and

resources to cause great harm, including insiders,1

 hackers, foreign

governments conducting political and military intelligence operations,

domestic and foreign enterprises engaged in industrial espionage, and

terrorist groups seeking to disrupt our society or cripple our economy.2

Unauthorized disclosure, theft, modification, or malicious destruction of

such information could bankrupt a business, interrupt vital public service,

or destroy lives.

Information security plays a key role in protecting computer systems,

networks, and information—including voice, fax, and data

communications—from harm, disclosure, or loss. Privacy depends heavily

on security.3

 In essence, there is little or no privacy protection afforded by

poorly secured information systems and networks. While

privacy-enhancing legislation, regulations, and management practices play

an important role in reducing the threat to individual privacy, it is security

technology that will provide many of the safeguards.4

Significant effort will be needed to define, develop, test, and implement

measures to overcome the security challenge posed by the increasing

complexity, interconnectivity, and the sheer size of the evolving

superhighway. These measures include identifying the superhighway’s

security and privacy requirements and developing tools and techniques to

satisfy the requirements.

The federal government, because of its extensive experience and expertise

in developing secure networks, is addressing selected aspects of security

and privacy. However, critics of federal involvement argue that the current

federal strategy represents a danger to civil liberties and that individuals

1

Many violations of information safeguards are perpetrated by trusted personnel who engage in

unauthorized activities or activities that exceed their authority. These insiders may copy, steal, or

sabotage information, yet their actions may remain undetected.

2

Economic Espionage: The Threat to U.S. Industry (GAO/T-OSI-92-6, Apr. 29, 1992).

3

Privacy is the state of being free from unsanctioned intrusion; a condition in which an individual can

determine when, how, and to what extent information about him or her is collected, used, and

communicated to others.

4

Information Security and Privacy in Network Environments, Office of Technology Assessment,

Washington, D.C: September 1994.

Page 18 GAO/AIMD-95-23 Information Superhighway
Chapter 2 

Ensuring Security and Privacy Will Pose a

Major Challenge

should be free to choose the technical means for achieving information

security. As a result, the challenge will be establishing a reasonable level

of consensus among the major players—the government, the computer

and communications industry, the business community, and civil liberty

groups—on how to ensure information security and privacy on the

information superhighway.

Networks and

Computer Systems

Are Increasingly

Vulnerable to Attacks

The vulnerability of interconnected computer systems is periodically

highlighted by attacks on the thousands of computer systems connected to

the Internet. These attacks provide an important lesson. The Internet—the

world’s largest network of networks—has many of the same attributes that

will eventually be found in the information superhighway. The information

superhighway may not only share similar vulnerabilities, but it may face

similar, albeit greatly magnified, threats.

Two major security incidents affecting the Internet illustrate the risk to the

evolving information infrastructure. On November 8, 1988, thousands of

computers connected to the Internet were attacked by a worm.5

 While the

worm did not damage or compromise data, it did deny service to

thousands of users working at the nation’s major research centers. We

found that a number of vulnerabilities facilitated this attack, including the

lack of a central focal point to address Internet-wide security problems;

security weaknesses at host computer sites; and problems in developing,

distributing, and installing software patches to operating system software.6

 In response to this incident, the Advanced Research Projects Agency

established a Computer Emergency Response Team to assist the Internet

community in responding to attacks. Several federal agencies and

private-sector organizations also established additional computer

emergency response teams coordinated by NIST.

Five years later, in January 1994, intruders again exploited similar

weaknesses. This time, the attack was more serious. The intruders gained

access to a number of hosts (computer systems) linked to the Internet.

The intruders then installed software that captured user names,

passwords, and hosts’ addresses for Internet traffic terminating at, or

passing through, the attacked sites. In addition, they installed two Trojan

5

Worms are self-contained programs containing malicious code that copy versions of themselves

across electronically connected nodes.

6

Computer Security: Virus Highlights Need for Improved Internet Management, (GAO/IMTEC-89-57,

June 12, 1989).

Page 19 GAO/AIMD-95-23 Information Superhighway
Chapter 2 

Ensuring Security and Privacy Will Pose a

Major Challenge

horse programs,7 one program to provide back-door access for the

intruders to retrieve the captured passwords, and a second program to

disguise the network monitoring process. With this information, the

intruders could access 100,000 Internet accounts.8

 The Department of

Defense reported that the attacks compromised a major portion of the

international commercial networks as well as major portions of the

unclassified Defense information infrastructure. Defense functions

affected by the attacks included ballistic weapons research, ocean

surveillance, and the military health care systems.

Security Measures Are

Critical to Minimizing

Risk

Reducing the frequency and damage of attacks against the national

networks will require a significant effort to provide the tools and

resources necessary for the development and deployment of

infrastructure-wide security services. These services include

• identification and authentication—the ability to verify a user’s identity and

a message’s authenticity,

• access control and authorization9—the protection of information from

unauthorized access,

• confidentiality—the protection of information from unauthorized

disclosure,

• integrity—the protection of information from unauthorized modification

or accidental loss,

• nonrepudiation—the ability to prevent senders from denying they have

sent messages and receivers from denying they have received messages,

and

• availability—the ability to prevent denial of service, that is, to ensure that

service to authorized users is not disrupted.

Cryptography10 will play a key role in the development of five of the six

security services for the information superhighway. It helps, through

password encryption, to improve identification and access control; it

protects confidentiality and data integrity by encrypting the data; and

finally, it improves, through encrypted electronic signature and related

means, nonrepudiation services.

7

A Trojan horse is a program that conceals malicious computer code. Typically, a Trojan horse

masquerades as a useful program that users would want or need to execute. It performs, or appears to

perform, as expected, but also does surreptitious harm.

8

Computer Incident Advisory Capability team, Department of Energy.

9

Authorization involves two steps—identification and authentication.

10Cryptography is a technique for transforming ordinary text (plaintext) into unintelligible ciphertext

through encryption.

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Chapter 2 

Ensuring Security and Privacy Will Pose a

Major Challenge

Two basic types of cryptographic systems exist: secret key systems (also

called symmetric systems) and public key systems (also called asymmetric

systems).11 In secret key cryptography, two or more parties use the same

key to encrypt and decrypt data. As the name implies, secret key

cryptography relies on keeping the key secret. If this key is compromised,

the security offered by cryptography is eliminated. The best known secret

key algorithm is the Data Encryption Standard. It is currently the most

widely accepted, publicly available symmetric cryptographic algorithm.

Secret key systems also require that a secure communications channel be

established for the delivery of the secret key from the sender to receiver.

Such a secure, nonelectronic communications channel for the distribution

of secret keys is costly to establish and maintain.

Unlike secret key cryptography, which employs a single key shared by two

or more parties, public key cryptography uses a pair of matched keys for

each party. One of these keys is public and the other private. The public

key is made known to other parties—mainly through electronic

directories—while the private key must be kept confidential. Thus, under

the public key system, there is no need to establish a secure channel to

distribute keys. The sender encrypts the message with the recipient’s

freely disclosed, unique public key. The recipient, in turn, uses her unique

private key to decrypt the message.

Public key cryptography also enables the user to produce an electronic

signature. The user encrypts the signature using the private key, which,

when decrypted with the public key, provides verification that the

message originated from that user. The best known public key algorithm is

the Rivest-Shamir-Adelman algorithm.12 The Pretty Good Privacy software,

which implements the Rivest-Shamir-Adelman algorithm, is probably one

of the best known public key cryptographic systems.13 Figure 2.1

highlights the principal features of the secret and public key cryptographic

systems.

11A key is a unique sequence of letters, numbers, or combination of both that is used to encrypt and

decrypt messages.

12Rivest-Shamir-Adelman is a public key algorithm used for both encryption and authentication; it was

invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adelman.

13The Pretty Good Privacy is a public key cryptographic system developed by Philip Zimmerman.

Page 21 GAO/AIMD-95-23 Information Superhighway
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Ensuring Security and Privacy Will Pose a

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Figure 2.1: Secret and Public Key Encryption Systems

Alice Bob

Secret Key System

Public Key System

ar%thRd3#qwW@1aknHg&8

Kl*0=+56gfr#erv=BuER!2~fn

Cryptographic

device or

software

Attack at dawn

Plaintext Ciphertext

Cryptographic

device or

software

Unsecured communication channel

Attack at dawn

Plaintext

Shared

secret

key

Bob’s

public

key

Alice uses her secret key to encrypt

message to Bob. She must also

send her secret key to Bob.

Alice uses Bob’s public key to encrypt

her message to Bob.

Bob uses Alice’s secret key to decrypt

her message. He must use Alice’s

secret key to encrypt his response.

Bob uses his private key to decrypt

Alice’s message. He will use Alice’s

public key to encrypt his response.

Public key directory

Bob

Alice

Alice’s

public

key

Alice’s

private

key

Bob’s

private

key

A host of related security technologies, including computer memory cards,

will also play an important role in securing the information superhighway.

Computer memory technology uses a credit-card-size electronic module to

store digital information that can be recognized by a network or a host

system. Figure 2.2 shows a computer memory card—the Tessera Crypto

Card—developed by the National Security Agency.14 The Tessera Crypto

14The Tessera crypto card, based on the Personal Computer Memory Card International Association

Industry standard, was recently renamed Fortezza. The card is a key element of the Department of

Defense’s Multilevel Information Systems Security Initiative.

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Card is a small, portable cryptographic module that provides high-speed

authentication and encryption services.

Figure 2.2: Tessera Crypto Card

Federal Role in

Security and Privacy

Is Subject to Debate

Federal involvement in communication security is fueling a debate over

the federal role in regulating the development and use of encryption and

communications technologies. Critics of federal involvement, such as the

Electronic Frontier Foundation—a public interest organization focused on

protecting civil liberties in digital environments—believe that government

control of encryption technologies and their implementation represents a

danger to civil liberties, and that individuals should be free to choose the

technical means for meeting their security requirements. Others, including

NIST and Defense officials, maintain that the federal government’s

participation and guidance in securing the information superhighway may

be needed for several reasons. First, the government is a major consumer

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of telecommunications services and has unique national security and law

enforcement needs that must be addressed. Second, the government, and

particularly the Department of Defense, has considerable experience in

the areas of computer and communications security. Defense, the

developer and operator of the world’s largest secure communications

network, could provide expertise needed to help develop the

superhighway’s security architecture. The need for such an architecture

was underscored by a recent study which noted that it is “imperative to

develop at the outset a security architecture that will lay the foundation

for protections of privacy, security, and intellectual property

rights—safeguards that cannot be supplied as effectively on an add-on

basis.”15

Since the invention of the telegraph and telephone, intelligence and law

enforcement agencies have conducted legal intercepts of communications

both here and abroad. In general, these agencies used technically simple

intercepts that targeted unprotected communications. However, the

emergence of digital technologies and the increased availability of

sophisticated encryption tools has dramatically eroded the government’s

electronic intelligence and analysis capabilities. The proliferation of digital

communications is making wiretapping increasingly difficult, while robust

encryption prevents third parties, including law enforcement and

intelligence agencies, from deciphering and understanding intercepted

messages.

The administration, after coordination with the Congress, industry, and

public advocacy groups, has developed a strategy designed to preserve the

government’s ability to conduct electronic surveillance, wiretapping, and

analysis of voice and data communications between criminals, terrorists,

drug dealers, and foreign agents. This strategy includes

• a major new federal cryptography initiative known as the Key Escrow

Standard (popularly known as the “Clipper chip” program),

• the Communications Assistance for Law Enforcement Act requiring the

information industry to provide “built-in” wiretapping support in its digital

communications systems, and

• restrictions on the export of encryption technology.

15Realizing the Information Future, National Research Council, National Academy Press. 

Washington, D.C.: 1994, p. 5.

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Key Escrow Initiative

Intended to Improve

Communication Security

The Key Escrow initiative is a voluntary program to improve the security

and privacy of telephone communications in the private sector while

meeting the legitimate needs of law enforcement. In essence, the initiative

is the government’s attempt to preempt the threat posed by sophisticated

encryption capabilities by offering the industry a relatively inexpensive,

albeit government-controlled, hardware-based encryption system capable

of providing secure voice, fax, and data services. To ensure that law

enforcement agencies are able to understand Clipper-encrypted voice

communications, the private encryption keys assigned to each individual

Clipper chip are to be escrowed with the government. These keys will be

made available to law enforcement agencies for court-ordered wiretaps.

The Clipper chip, developed by NSA, is a microcircuit incorporating a

classified encryption algorithm known as Skipjack.16 The chip, and its

close relative, the Capstone chip, contain a unique key that is used to

encrypt and decrypt messages, programmed by the escrow agents.17 This

unique key is then split into two components and delivered to two federal

agencies—or escrow agents—for safekeeping. When federal authorities

encounter Clipper chip encrypted voice or Capstone chip encrypted data

communications during the course of court-authorized wiretapping, they

may obtain the unique key necessary for the decryption of the wiretapped

communications from the escrow agents. Figure 2.3 shows a Capstone

chip and three prototypes of a Clipper chip.

16The power of the Clipper chip technology is highlighted by comparing it to earlier voice encryption

devices. For example, in the early 1940s, the administration asked scientists at the Bell Telephone

Laboratories to develop a telephone scrambler that would allow Winston Churchill and President

Roosevelt to have secure conversations. Code named “Sigsaly,” this transatlantic scrambler needed, at

the London end, not only a five foot high intermediate scrambler cabinet, but also over 30 seven foot

tall relay racks weighing eighty tons, 72 different radio frequencies, a large air-conditioned room, and

30 kW of energy to encipher one short conversation (The Cabinet War Rooms, Imperial War Museum,

London, 1994).

17The Clipper chip is designed to encrypt voice transmission; the Capstone chip is designed to encrypt

data and video transmission.

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Figure 2.3: The Capstone and the

Clipper Chips

Source: National Security Agency.

In April 1993, the President directed the Attorney General to (1) request

manufacturers of communications hardware that incorporates encryption

to install the Clipper chip in their products, and (2) designate two

government organizations as “key escrow” holders. The President also

directed the Secretary of Commerce to initiate, through NIST, a process to

develop federal key escrow encryption standards. Despite strong industry

opposition,18 the administration reaffirmed its 1993 directive and

instructed the Secretary of Commerce to approve the Clipper chip as a

voluntary national standard for encrypted telephone communications. In

February 1994, NIST formally approved the new standard. At the same time,

the Attorney General designated NIST and the Automated Systems Design

Division of the Department of the Treasury as the key escrow agents.

Critics of the Key Escrow initiative argue that NSA’s refusal to declassify

and publish the Skipjack encryption algorithm raises the possibility that

18In July 1993, NIST asked industry to comment on the proposed standard. Of the 320 respondents,

only 2 supported the proposed standard.

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the algorithm may have a built-in “trap door.”19 Such a trap door would

allow intelligence agencies to decrypt Clipper and Capstone encrypted

communications at will, without obtaining the private keys from the

escrow agents.20 The critics also note that since robust encryption

technology is available both in the U.S. and abroad, there is no incentive

for domestic and international industry or private citizens to adopt the

Clipper/Capstone technology.

The misgivings about the Key Escrow initiative were also shared by the

Computer System Security and Privacy Advisory Board.21 In its 

June 4, 1993, resolution, the Board stated that the administration has not

(1) provided a convincing statement of the problem that Clipper attempts

to solve, (2) considered other escrow alternatives including the

designation of a third, non-government escrow agent, and (3) fully

examined the legal and economic implications of the Clipper chip

initiative. The Board recommended that the Key Escrow encryption

technology not be deployed beyond current implementations planned

within the Executive Branch until the significant public policy and

technical issues inherent with this encryption technique are fully

understood. The Congress asked the National Research Council to

conduct a comprehensive study of national cryptography policy and

submit, within 2 years, a report to the Secretary of Defense.22 In

December 1993, the Board endorsed the proposal, noting that the study

should be conducted as quickly as possible.

In July 1994, the administration reaffirmed its commitment to the Key

Escrow scheme in general, and to the use of the Clipper chip for telephone

communications in particular. It also offered a compromise on the

development of the Capstone chip for computer and video networks.

Specifically, the administration said that it understood the concerns that

industry has regarding the Capstone chip and welcomed the opportunity

to work with industry to design a more versatile, less expensive system.

NIST and the information security industry have now initiated a joint effort

to explore alternative approaches. Such alternative key escrow schemes

19A trap door is a hidden software or hardware mechanism that allows systems controls to be

circumvented. Software developers often introduce trap doors in their code to enable them to reenter

the system later and perform certain functions.

20On more than one occasion, administration officials, including the Deputy Director of NIST, have

testified before Congress that the Skipjack algorithm does not incorporate a trap door mechanism.

21The Board, composed of representatives from the computer and telecommunications industry,

independent experts in telecommunications, and federal employees, was established by the Computer

Security Act of 1987 to advise the Secretary of Commerce and the Director of NIST on security and

privacy issues.

22Public Law 103-160, Section 267.

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would be implemented in software, firmware, or hardware, or a

combination thereof; would not rely on a classified algorithm; would be

voluntary; and would be exportable.23

Legislation Enacted to

Facilitate Digital Wiretaps

To address concerns about the potential loss of wiretapping capability due

to the rapid deployment of digital communications,24 in October 1994 the

Congress enacted the Communications Assistance for Law Enforcement

Act.25 The act requires common carriers to ensure that they posses

sufficient capability and capacity to accommodate law enforcement’s

wiretapping needs. Specifically, the act requires that telecommunications

carriers develop the capability to expeditiously isolate the content and

call-identifying information of a targeted communication and enable the

government to access targeted communication at a point away from the

carrier’s premise. The act requires the government to reimburse carriers

for all reasonable costs associated with complying with the act’s

requirements. Critics of the act—including the Electronic Frontier

Foundation—argue that it further erodes communication privacy, and that

the Federal Bureau of Investigation has not adequately documented its

need for sophisticated digital wiretap capability.

Federal Government

Restricts the Export of

Encryption Technology

Many of the U.S. encryption technologies, whether developed

commercially or by the government, are subject to export controls. The

Departments of State and Commerce share responsibility for controlling

the exports of these technologies.26 However, computer industry

representatives view the encryption export controls as counterproductive

and economically damaging. For example, the representatives noted that

because robust, sophisticated encryption technologies, including

technologies on the U.S. Munitions List, are widely available in foreign

markets, the export controls are reducing their international sales.27

Our brief search of foreign Internet sites confirms industry’s assertion that

sophisticated encryption software is widely available to foreign users. For

23Letter from Vice President Al Gore to the Honorable Maria Cantwell, House of Representatives,

July 20, 1994.

24Electronic Surveillance: Technologies Continue to Pose Challenges (GAO/T-AIMD-94-173, 

Aug. 11, 1994).

25Public Law 103-414.

26Certain encryption products are placed on the U.S. Munitions List. These products require a

munitions license for export to foreign countries.

27Communications Privacy: Federal Policy and Actions, (GAO/OSI-94-2, Nov. 4, 1993).

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example, we found that a number of European Internet sites are offering

U.S.-made encryption software. In less than two hours, we identified

several European sites offering the Pretty Good Privacy software, obtained

it from an Internet site in Great Britain, installed the software on our

computer, and encrypted a message (shown in figure 2.4).

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Figure 2.4: Message Encrypted With

the Pretty Good Privacy Encryption

System

Page 30 GAO/AIMD-95-23 Information Superhighway
Chapter 3 

Achieving Interoperability Is a Critical Goal

Interoperability—the ability of two or more components of a system or

network to interact with each other in a meaningful way—is a key goal of

the information superhighway. However, full interoperability among the

thousands of networks, communications devices, and services that will

comprise the information superhighway will be difficult to achieve. To do

so, governments, industry, and standards-setting organizations must agree

on well-defined international standards for rapidly advancing

communications technologies, while manufacturers and service providers

need to provide products and services conforming to these standards.

However, the telecommunications industry is already deploying, or plans

to deploy, a host of technologies and services that are based on ill-defined,

anticipatory, or competing standards. To address this dilemma, the federal

and private sectors have initiated interoperability efforts, including the

assessment of various “open network” architectures.1

Interoperability Will

Be Difficult to

Achieve

Interoperability will define the information superhighway. Without

interoperability, the information superhighway will be fragmented into

thousands of poorly integrated communications networks providing a

bewildering choice of incompatible services. While policymakers, public

interest groups, and industry agree that interoperability is a key

requirement, they also agree that it will be difficult to achieve among the

thousands of communications networks, computers, databases, and

consumer electronics that will comprise the information superhighway. As

discussed in chapter 1, the existing infrastructure suffers from significant

interoperability problems.

New Technologies Being

Deployed Are Based on

Ill-Defined, Anticipatory,

and Competing Standards

Because of competitive pressures, the desire to provide new capabilities,

and a belief that the traditional standards-setting process is unable to keep

up with the fast pace of technological change, industry is deploying, or is

planning to deploy, a host of new technologies and services. However,

many of these technologies and services are based on ill-defined,

anticipatory, or competing standards, thereby further complicating efforts

to achieve interoperability.

The effects of deploying new technology based on ill-defined standards is

illustrated by the implementation of the ISDN. ISDN is an end-to-end digital

network evolving from the existing telephone network. It is viewed as the

first step in the conversion to a fully digital network. However, the initial

1

The National Research Council defines an open network as one that is capable of carrying

information services of all kinds, from suppliers to customers, across network service providers of all

kinds, in a seamless, accessible fashion.

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deployment of ISDN resulted in the proliferation of “island” ISDN services

that could not interoperate because the ISDN standards provided only a

broad outline and lacked enough detail to ensure that all implementations

would be identical. For example, ISDN users in New York and New England

are unable to communicate data with ISDN users in the middle atlantic

states. To alleviate the ISDN interoperability problems, the industry

announced a plan to establish a consistent interface that would provide

interoperability between local telephone companies, long distance

telephone companies, and equipment manufacturers.

The deployment of the Asynchronous Transfer Mode (ATM) services

provides an example of a technology deployed based on anticipatory

standards. The broadband ISDN (B-ISDN) technology, which is expected to

lay the foundation for the superhighway’s interactive, high-speed digital

communications infrastructure, will rely on ATM/SONET optical fiber

networks.2

 However, critical ATM standards including global routing and

addressing, resource management, multicast,3

 and network management

remain undefined. The industry is also developing products and services in

the absence of less visible, but equally important standards, for data

display and exchange, accounting and billing, network addressing and

naming, and telephone number portability (see appendix IV).

The introduction of competing technologies is highlighted by the

deployment of digital cellular systems. Digital cellular systems are viewed

as a key component of the evolving personal communications networks.

While digital systems will offer dramatically better performance than their

analog counterparts, their near-term value in serving as a key link in the

emerging B-ISDN network is reduced by compatibility problems. There are

three principal digital cellular standards—the U.S. standard, known as the

North American Dual-Mode Cellular System; the European standard,

known as Global System for Mobile Communications; and the Japanese

Digital Cellular standard. Although all three standards are based on the

time division multiple mode access technique,4

 they are not interoperable.

2

ATM is a fast packet switching technology utilizing small, fixed-size cells. Synchronous Optical

Network (SONET) is the U.S. implementation of an international synchronous digital hierarchy

standard for optical carrier networks.

3

Multicast is a variant of broadcast, where information can be sent to selected recipients instead of all

subscribers of a particular communications systems.

4

A digital encoding scheme that allows users to simultaneously transmit on the same frequency by

allocating each user a discrete time slot.

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The Federal and

Private Sectors Have

Initiated Efforts to

Address

Interoperability

While the key players—the federal government, the computer and

communication industries, and various user groups—appear to agree on

the need for a fully interoperable information superhighway, there is no

agreement yet on how it should be achieved. The principal federal

organizations focused on superhighway interoperability include NIST and

the National Research Council’s Computer Science and

Telecommunications Board.5

 The overall coordination of federal

interoperability efforts is being examined by IITF’s Technology Policy

Working Group. In the private sector, the FCC is working with industry to

ensure the interoperability of selected technologies deployed in public

networks. Industry has also established a consortium for the development

and testing of superhighway applications.

National Research Council

Advocates High-Level

Architecture to Guide

Interoperability Efforts

One promising approach to the planning for interoperability is to develop a

high-level architecture—or framework—of the superhighway. This

approach was advocated by a recent National Research Council report

that presented a vision of the superhighway based on an open data

network concept.6

 Under this concept, the superhighway must be

• open to users: it does not force users into closed groups or deny access to

any sector of society, but permits universal connectivity, as does the

telephone system,

• open to service providers: it provides an open and accessible environment

for competing commercial or intellectual interests, including information

providers,

• open to network providers: it makes it possible for any network providers

to meet the necessary requirements to attach and become a part of the

aggregate of interconnected networks, and

• open to change: it permits the introduction of new applications and

services over time; it also permits the introduction of new transmission,

switching, and control technologies as these become available.

This concept, expressed as a high-level network architecture, could

provide a set of specifications to guide the detailed design of the

information superhighway. Without such a framework, the pieces of the

emerging superhighway may not fit together. The IITF’s Technology Policy

Working Group is planning to examine the open data network concept and

5

The federal interagency High Performance Computing and Communications program is also

addressing a wide range of network interoperability issues.

6

Realizing the Information Future, National Research Council, National Academy Press. Washington,

D.C.: 1994.

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Achieving Interoperability Is a Critical Goal

its applicability to various industries, including cable television,

broadcasting, communications and computer.

Industry Responds to

Interoperability Problems

In an attempt to improve interoperability, the Network Operation Forum

of the Alliance for Telecommunications Industry Solutions established the

Internetwork Interoperability Test Plan Ad Hoc Committee. However, the

committee’s effort was limited to solving problems with the Signaling

System 7 (SS7)7

 switching systems. The requirements for intranetwork,

product-to-product, and stand-alone equipment modeling and testing were

considered to be outside of the committee’s charter. Other aspects of

existing networks such as interoperability testing requirements of newer

technologies were also not addressed. So far, the committee has

developed scenarios designed to test the interoperability of SS7 systems.

7

SS7 is an international common-channel signaling system.

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Chapter 4 

Network Reliability Is Emerging as a Key

Challenge

Ensuring the reliability1 of the information superhighway will be essential.

The public and private sectors are increasingly dependent on the existing

telecommunications networks, which will be the foundation of the

information superhighway, to meet their business needs. Yet recent

outages on these networks have raised concerns and caused economic

losses. Moreover, new technologies and industry trends will likely increase

network vulnerability, making reliability of the superhighway a key

challenge. The government and industry have recently taken several steps

to address reliability, including the formation of the Network Reliability

Council and the Alliance for Telecommunications Industry Solutions.

Reliability of the

Superhighway Will Be

Essential

In providing critical commercial and personal services, the superhighway

will require a highly reliable network. The nation is already dependent on

the existing networks, which will provide the underpinning for the

superhighway. For example, in addition to conventional telephone

services, computers are networked together, facsimile machines provide

almost instant access to images and documents, and teleconferencing and

videoconferencing have emerged as substitutes for travel. The number of

electronic transactions conducted over these networks is enormous. For

example, the value of the telephone transactions that take place daily on

Wall Street exceeds one trillion dollars. Similarly, the Federal Aviation

Administration relies on the public network to transmit air traffic control

information between individual airports.

Public telephone networks are also being increasingly relied upon for

emergency services. For example, the telephone has replaced fire alarm

boxes as the primary method for reporting fires. Emergency 911 service

can be obtained from personal or public pay phones. Telephones are also

used to report medical emergencies requiring emergency medical

technicians, and burglaries and domestic problems requiring responses

from the police. Enhanced 911 service, available in many locations, is even

capable of automatically routing the emergency call to a public service

answering point, the facility in charge of answering calls and dispatching

appropriate services in the caller’s area. The system also searches phone

company databases to determine and report the caller’s location and

telephone number to the dispatcher.

1

Reliability is the probability that a system will not fail over a given period of time and under specified

conditions. It is based on the combined reliability of all of the components that make up the system,

their interconnections, and the environment in which the system operates.

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Recent Network Outages

Have Raised Concerns and

Caused Economic Losses

While the public and private sectors are becoming more dependent on

networks, a growing number of major outages have raised concerns,

triggered losses of service, potentially risked lives, and affected the

economy. Several of these outages are highlighted below.

May 8, 1988: More than 500,000 business and residential customers lost

telephone service due to a fire at the Hinsdale, Illinois, central office.

During the following two weeks, approximately 3.5 million calls were

disrupted. Hospitals with centrex service in the affected area could not

make calls from one floor to another. Twenty percent of the departing

flights from O’Hare International Airport were canceled and flights from

other airports around the country had to be rescheduled. In a study of the

Hinsdale outage, the University of Minnesota concluded that the cost of

network failures to airlines could be between $2 and $3 million per hour

and investment bankers could lose up to $5 million per hour.

Jan. 4, 1991: Maintenance workers in a cable vault in New Jersey

accidentally cut an optical fiber transmission line that provided service to

lower Manhattan. Sixty percent of the calls into and out of the city were

disrupted for eight hours. The New York Mercantile Exchange and the

Commodity Exchange had to shut down operations. Voice and radar

systems that are used to control air traffic from facilities in New York,

Washington, and Boston were disabled for five hours.

Sept. 17, 1991: Through a power sharing arrangement with New York’s

Consolidated Edison, AT&T agreed to use its own power when

Consolidated Edison’s facilities were heavily loaded.2

 On this particularly

warm day in September, AT&T switched to its own power. Batteries

designed to meet the initial instantaneous power demand performed as

intended. However, alarms that were intended to inform technicians to

start the facility’s diesel generator had been manually disabled. When the

batteries discharged, all telephone transmission systems in the facility shut

down and voice and data communications controlled by the facility failed.

Voice and data communications between the New York, Boston, and

Washington Air Route Traffic Control Centers stopped. Three New York

area airports closed for several hours. Flights destined for New York were

either delayed or canceled. Air traffic at Boston was severely disrupted

and delays occurred nationwide. More than 1,174 flights were canceled or

delayed and approximately 85,000 passengers were affected. The day after

the phone outage, flight schedules were still disrupted because aircraft

were not at the right airports for the scheduled morning flights.

2

Wall Street Journal, December 12, 1991.

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Sept. 10, 1993: A road crew boring holes for highway road signs in Ohio

cut a high-capacity fiber-optic cable belonging to MCI.3

 The cable, which

carries most of the company’s east-to-west traffic, was repaired in about

seven hours. However, millions of residential and business customers

were unable to make coast-to-coast calls during that period.

March 15, 1994: During the early morning hours a fire broke out in

Pacific Bell’s Los Angeles central office known as the Madison Complex.

Before complete service was restored, almost 17 hours later,

approximately 395,000 customers may have been affected and over

5 million calls were blocked.

Cable cuts, a source of major outages, occurred 160 times during the

period between March 1, 1992, and February 4, 1993, with 93 (58 percent)

of them caused by “dig-up” incidents, such as the one illustrated in figure

4.1. The average time needed to restore service after a cable cut was 5.2

hours with a maximum of 21.4 hours. The average time required to repair a

fiber cable cut was 14.2 hours with a maximum of 97.5 hours.

3

Wall Street Journal, September 13, 1993.

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Figure 4.1: Fiber Optic Cable “Dig-Up”

Accident

Source: AT&T Technology Magazine.

On February 13, 1992, the FCC instituted mandatory outage reporting

requirements for outages that affect more than 30,000 customers for

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durations lasting 30 minutes or longer. As of June 1994, more than 314

outages were reported. The calculation of the cost of an outage is difficult

because of the variety of users that could be affected.

New Technologies,

Network Growth, and

Complexity Will Likely

Increase Network

Vulnerability

The deployment of advanced technologies, such as intelligent network

architectures, common channel signaling, integrated services digital

network, broadband transport facilities, customer control, and

user-programmability, is increasing network complexity and vulnerability.

The new technologies, described in appendix III, are also allowing

network designers to concentrate more traffic into larger and fewer

switches, and to rely on fewer higher capacity fiber optic cables to

transmit hundreds of thousands of telephone calls. Failure of any of these

high-capacity elements could be potentially devastating.

As the information superhighway grows, the number of networks and

service providers is also expected to grow. Telecommunications

consumers will increasingly acquire services from combinations of

suppliers’ products, service providers, and network providers. Increasing

network complexity will make it more difficult to isolate and correct

problems.

The Government and

Industry Are Taking

Steps to Address

Reliability

In 1991, the FCC, concerned about the spate of telephone network outages

that affected a large number of subscribers on both the east and west

coasts, established the Network Reliability Council. The council’s goal was

to bring together leaders of the telecommunications industry,

telecommunications experts from academia, and consumer organizations,

to explore and recommend measures that would enhance network

reliability. Members include the executive officers of most of the major

U.S. telephone companies, principal equipment suppliers, long-distance

companies, consumer organizations, corporate and federal user

representatives, and state regulatory agencies.

The council established a steering committee and seven focus groups to

deal with the key problem areas—signaling network systems, digital

cross-connect systems, fiber cable cuts, fire prevention, enhanced 911

service, power systems, and switching systems (with a focus on software).

The groups formulated recommendations for developing and

implementing countermeasures to reduce the number of outages;

monitoring the results; and modifying, as necessary, the countermeasures.

The commission is now looking at these recommendations and

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Chapter 4 

Network Reliability Is Emerging as a Key

Challenge

considering regulations that would require the carriers and equipment

suppliers to implement them.

In 1994, the Network Reliability Council restructured and created four

focus groups. The first group will concentrate on network reliability; the

second will examine reliability issues arising from expanded

interconnection of networks; the third will study network technology and

examine reliability concerns related to providing telephone service

through cable, satellites, and wireless systems; and the fourth group will

study the reliability of critical services, including 911, Federal Aviation

Administration, military, and government.

The Alliance for Telecommunications Industry Solutions—a private sector

organization—was formed to promote the timely establishment of

telecommunications standards and operational guidelines. Its members

include representatives of local exchange carriers, interexchange carriers,

enhanced service providers, manufacturers, vendors, and end users who

participate in a number of sponsored committees.

The alliance also sponsors the Network Operations Forum, a group of

telecommunications industry access providers and customers who meet

periodically to identify national operations issues involving the

installation, testing, and maintenance of access services. In July 1991, the

alliance began focusing on the area of network reliability. One of the

forum’s subcommittees has developed traffic management guidelines that

provide network management personnel with alternatives when

emergencies occur. The forum also maintains contact directories for use

in emergency situations.

Page 40 GAO/AIMD-95-23 Information Superhighway
Chapter 5 

Conclusions

While the information superhighway’s development is expected to be

arduous, a grand vision of its capabilities is beginning to emerge among

policymakers, industry leaders, and public interest groups. Viewed as a

global metanetwork that will seamlessly and reliably link millions of users

through broadband terrestrial and satellite digital networks, it is hoped

that the superhighway will allow users to routinely receive and transmit

large volumes of digital information, and ensure equal access for service

and network providers. Achieving the grand vision will depend largely on

how successfully industry and government meet the key technical

challenges of security and privacy, interoperability, and reliability.

Security and privacy of databases and users’ communications is a critical

issue. The superhighway will become an increasingly enticing target for

intruders with the technical expertise and resources to cause damage.

Given the complexity, size, and importance of the evolving superhighway,

significant effort will be needed to define, develop, test, and implement

security measures.

Interoperability among the thousands of networks, communications

devices, and services that will comprise the superhighway is also essential,

but will be difficult to achieve. The telecommunications industry is

deploying, or plans to deploy, a host of technologies and services that are

based on ill-defined, anticipatory, or competing standards. A coordinated

approach will help reduce the risk of the superhighway being fragmented

into thousands of poorly integrated networks providing a bewildering

choice of incompatible services.

Because the proposed superhighway is intended to provide critical

commercial and personal services, its end-to-end reliability requirements

will be very high. The public and private sectors are already highly

dependent on the existing telecommunications infrastructure and

networks that will be the foundation of the superhighway. Outages on

these networks have raised concerns about achieving reliability.

Government and industry are beginning to recognize these challenges. The

administration’s Information Infrastructure Task Force, working together

with the private sector, has formed committees and working groups

charged with addressing security and privacy, interoperability, and

reliability issues. The challenge remains for the major public and private

players to work together to resolve these issues. With effective

cooperation, the promise of the information superhighway can be attained.

Page 41 GAO/AIMD-95-23 Information Superhighway
Appendix I 

Information Infrastructure Task Force Is

Addressing Selected Technical Issues

The administration formed the Information Infrastructure Task Force

(IITF) to articulate and implement its vision for the information

superhighway. The task force includes high-level representatives of federal

agencies that play a major role in the development and application of

information and telecommunications technologies. Working together with

the private sector, the participating agencies plan to develop

comprehensive technology, telecommunications, and information policies

and promote applications that best meet the needs of both the agencies

and the country. By helping build consensus on difficult policy issues, the

IITF is planning to enable agencies to make and implement policy more

quickly and effectively.

The Secretary of Commerce chairs the IITF, and much of the staff work and

administrative support for the task force is being done by Commerce’s

National Telecommunications and Information Administration. The task

force operates under the aegis of the White House Office of Science and

Technology Policy and the National Economic Council. The administration

has also established the United States Advisory Council on the National

Information Infrastructure to facilitate private sector input to the IITF. The

Secretary appointed 37 members to serve a two-year term on the advisory

council. The council members represent the many different stakeholders

in the information superhighway, including industry, labor, academic,

public interest groups, and state and local governments.

The task force is undertaking a wide-ranging examination of all issues

relevant to the development and growth of the information superhighway.

The Administration’s Agenda for Action, released September 15, 1993,

identified nine specific principles and goals to guide government action:

• promoting private sector investment,

• extending the “universal service” concept to ensure that information

resources are available to all at affordable prices,

• promoting technological innovation and new applications,

• promoting seamless and interactive operation,

• ensuring information security and network reliability,

• improving management of the radio frequency spectrum,

• protecting intellectual property rights,

• coordinating with other levels of government and with other nations, and

• providing access to government information and improving government

procurement.

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Appendix I 

Information Infrastructure Task Force Is

Addressing Selected Technical Issues

To carry out its responsibilities, the IITF established three

committees—Telecommunications Policy, Information Policy, and

Applications and Technology. The Telecommunications Policy Committee

is responsible for formulating a consistent administration position on key

telecommunications issues. The committee has established the following

four working groups:

• The universal service working group works to ensure that all Americans

have access to and can enjoy the benefits of the information

superhighway.

• The network reliability and vulnerability working group works to

(1) ensure that the superhighway will provide protection for all users from

catastrophic failure of the network, along with mechanisms for recovery

from threats ranging from natural disasters to overt attacks; and (2) define

and monitor national security and emergency preparedness requirements.

• The international telecommunications working group examines

international telecommunications issues. This working group is

subdivided into five subworking groups that are addressing:

• the participation of foreign governments/foreign corporations in the

superhighway and the use of the superhighway to open overseas

markets,

• the effects of current law on setting policy, and legislative efforts to

change the law,

• the federal government’s controls of technology exports,

• U.S. participation in international organizations and standards-setting

bodies, and

• international use of research networks.

• The legislative drafting task force is to formulate the administration’s

telecommunications legislative reform initiatives.

The Information Policy Committee has five working groups that are

addressing critical information policy issues:

• The intellectual property rights working group is to develop proposals for

protecting copyrights and other intellectual property rights in an

electronic world.

• The privacy working group is to develop proposals to protect individual

privacy.

• The government information working group is to focus on ways to

promote dissemination of government data in electronic form.

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Appendix I 

Information Infrastructure Task Force Is

Addressing Selected Technical Issues

• The Freedom of Information Act legislation working group is to define

public access rights to government electronic records.

• The scientific and technical information group is to focus on ways to

manage technical and scientific information.

The Committee on Applications and Technology coordinates the

administration’s efforts to develop, demonstrate, and promote applications

of information technology in manufacturing, education, health care,

government services, libraries, environmental monitoring, electronic

commerce, and other applications. It has three working groups:

• The government information technology services working group

coordinates efforts to improve the application of information technology

by federal agencies.

• The technology policy working group addresses cross-cutting technology

issues related to interoperability and scalability of new

telecommunications and information services.

• The health information and applications working group coordinates

efforts that affect use of the superhighway for health care.

The IITF has also established the NII Security Issues Forum to coordinate

security efforts across the committees and working groups of the IITF.

Page 44 GAO/AIMD-95-23 Information Superhighway
Appendix II 

Description of Existing Network

Technologies

The following provides a brief overview of the three major types of

communication networks that comprise the existing communication

infrastructure—the wire-based voice and data telephone networks; the

cable-based video networks; and the wireless, voice, data, and video

networks.

The Telephone

Networks

The telephone system is the world’s largest switched distributed network

providing point-to-point voice, fax, data, and videoconferencing services to

hundreds of millions of subscribers. It is also, at first glance, the primary

foundation for the information superhighway. It is ubiquitous, highly

interoperable, and reliable. It is capable of handling millions of

simultaneous calls, and it provides accurate usage tracking and billing. In

the U.S., voice, data, and videoconferencing services are provided by the

local exchange carriers (local telephone companies) serving the local

access and transport areas, and by the interexchange carriers (long

distance carriers) providing long distance and international dialing

services through their long distance networks.1

 Although the industry is

rapidly introducing advanced digital communication technologies, the

telephone network continues to be dependent on analog transmission.2

Much of today’s telephone service is based on two analog-oriented

transmission technologies—the analog voice frequency (VF) systems and

the digital T-carrier system. The VF system supports voice transmission

over a pair of copper wires—also known as the local loop—connecting

millions of residential and business subscribers with the local telephone

company’s central offices. The T-carrier system plays a major role in the

first step in the transition from analog to digital capabilities. One of the

fastest growing segments of services offered by the local telephone

companies and the long distance carriers, the system can provide

transmission speeds up to 274.176 Mbps. The basic building block of the

T-carrier technology is a single VF voice channel digitized into a 64 Kbps

data stream; a T-1 line carries 24 digitized voice channels, an aggregate of

1.544 Mbps. The T-carrier digital hierarchy allows T-1 lines to be combined

to provide transmission rates of up to 274.176 Mbps.

1

The local telephone companies, created in the wake of the breakup of AT&T, include 22 Bell

Operating Companies organized into seven regional Bell holding companies—Pacific Telesis, US West,

Ameritech, Southwestern Bell, BellSouth, Bell Atlantic, and NYNEX. Many local area and transport

areas are also served by independent telephone companies. The major long distance carriers include

AT&T, MCI, U.S. Sprint, Advanced Telecommunications Corporation, and Wiltel.

2

During the 1980s, the telephone service providers replaced most of their older electromechanical

switches with analog or digital computer-driven switches.

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Appendix II 

Description of Existing Network

Technologies

The telephone network’s capabilities are unevenly distributed. Most of the

high-capacity fiber optic lines capable of carrying interactive video and

other bandwidth-intensive applications are either part of the long distance

or the local telephone area interoffice networks, or are used by the

telephone companies to provide private voice, data, and

videoconferencing services to business, government, and institutions. The

bandwidth available to residential subscribers is effectively constrained by

the limited transmission capacity of the copper wire linking the local

telephone company’s central office with the subscriber’s instrument, and

the lack of subscriber’s equipment capable of providing broadband

services. Similarly, although the local telephone companies generally use

digital switches to route telephone calls, in most cases the calls are

converted back to analog format for transmission to individual

subscribers. The basic architecture of a typical telephone network is

shown in figure II.1.

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Appendix II 

Description of Existing Network

Technologies

Figure II.1: A Typical Local Telephone Network

Optical Fiber

Tandem

access

Remote

terminal

Optical fiber

Twisted pair copper wire

Long distance

telephone company’s

point of presence

Long distance

network

Optical fiber

Large

business

customer

Local

telephone

company

B C

A

A A long distance carrier’s facility within a telephone company service area established

for the purpose of providing access to its long distance network.

.

B A local telephone company switching system used to concentrate and distribute

functions for telephone calls originating or terminating in the local service area.

.

C A remote switch or distribution center serving portions of the local

telephone company’s service area.

.

Source: Adapted from the “Hybridizing the Local Loop,” Craig J. Burnet, IEEE Spectrum,

June 1994.

Cable Television Network The nation’s cable television network links thousands of cable systems

with millions of subscribers via broadband coaxial cable.3

 This web of

coaxial cables is, in many respects, a counterpart of the local loop linking

telephone subscribers with the local telephone companies. However, there

are considerable differences between the transmission technologies and

network architectures deployed in the telephone and the cable systems.

3

During the last decade, the cable television industry experienced considerable growth, from 4,225

systems serving 17.7 million subscribers in 1980, to 11,075 cable systems serving over 57 million

subscribers. Today, cable service—or ready access to the service provider’s coaxial cable—is available

to over 96 percent of the nation’s homes.

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Appendix II 

Description of Existing Network

Technologies

The telephone system is based on a switched, distributed network

architecture, and uses standard switching and transmission protocols

capable of supporting global, narrowband, two-way, point-to-point

communications. The cable systems, on the other hand, are based on a

tree-and-branch network architecture and proprietary transmission

protocols designed to support one-way broadband analog transmission

with little or no provision for “upstream” communications. The basic

architecture of a typical cable system is shown in figure II.2.

Figure II.2: A Typical Cable System Architecture

Wireless Networks Wireless networks are an important element of the communications

infrastructure. These systems—including cellular and space-based systems

and networks—are providing users with an unprecedented degree of

mobility and flexibility. The cellular and satellite networks have

advantages over terrestrial networks because they are potentially

accessible from any point on the globe without the cost of installing wire

or a cable. The current analog cellular services were developed in the early

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Appendix II 

Description of Existing Network

Technologies

1970s to alleviate growing radio frequency spectrum congestion and to

overcome the limited capacity of the early mobile radio systems. In the

cellular systems, this is accomplished by dividing a large geographic

service area into discrete regions—or cells—each of which is served by a

low-power base station transmitting to and receiving from mobile

telephones within its area. The use of low-powered transmitters operating

on short-wavelengths allows the cellular systems to efficiently exploit the

available radio spectrum by “reusing” the assigned radio frequencies

throughout the service area.4

 However, the analog cellular systems have

not fulfilled their early promise. In many large metropolitan markets, the

systems are saturated and will be slowly supplemented, and eventually

replaced, with digital systems.5

 The architecture of a typical cellular

system is shown in figure II.3.

4

In the U.S. and in several other countries, the analog cellular systems are based on the Advanced

Mobile Phone Services standard. This standard provides 416 voice channels and employs a seven-cell

frequency reuse pattern.

5

The FCC requires that any new digital cellular system be fully compatible with the current analog

system. The new hand-held mobile units will be capable of either analog or digital operation.

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Appendix II 

Description of Existing Network

Technologies

Figure II.3: A Typical Cellular System Architecture

Local telephone

company

Base station

with an antenna

Mobile telephone

switching office

Cell

Hand-held

cellular

telephone

Mobile

cellular

telephone

Satellite networks have advantages over terrestrial networks because they

are accessible from any spot on the globe; can provide broadband digital

services, including voice, data, and video, to many points without the cost

of acquiring right-of-way and cable installation; and can add receiving and

transmitting sites without significant additional costs. Commercially

available since 1965, communications satellites are a critical part of the

global communications infrastructure. Today, there are about 150

communications satellites in geosynchronous orbit (GEO) providing a wide

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Appendix II 

Description of Existing Network

Technologies

range of services, including broadcast video and overseas telephone links.6

In general, GEO satellites are designed to broadcast a wide beam to ensure

the coverage of a large geographic area. Although such a large broadcast

“footprint” allows only three GEO satellites to provide nearly global

coverage, the network’s receiving stations require large antennas to

capture the relatively weak signal.

In the 1980s, industry introduced a new class of satellites using a narrow

beam to focus the transmitted energy on a small geographic areas. Known

as very small aperture terminal (VSAT) satellites, the new breed of satellites

use small ground antennas to provide low data rate point-to-point network

services. VSAT networks are being increasingly used by large corporations

to link hundreds of motel/hotel or retail sites. Figure II.4 shows a typical

GEO broadcast and VSAT satellite system based on a hub and spoke relay

configuration. Because this configuration does not allow direct

terminal-satellite-terminal relays, all communications must be routed

through the hub terminal.

6

GEO satellites are placed in a high circular orbit 22,300 miles above the equator. Because GEO

satellites rotate with the Earth, they appear to be stationary.

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Appendix II 

Description of Existing Network

Technologies

Figure II.4: Broadcast and VSAT Satellites

22,300 miles

VSAT Satellite

User

terminal Hub

terminal

22,300 miles

Geosynchronous

Satellite

Page 52 GAO/AIMD-95-23 Information Superhighway
Appendix III 

Description of Advanced Technologies

The communications industry is beginning to introduce several new and

innovative technologies that will allow the delivery of many of the

advanced services and capabilities of the information superhighway.

These technologies include

• narrowband ISDN,

• advanced signaling and intelligent networks,

• B-ISDN,

• personal communications networks, and

• broadband in the local loop.

The Narrowband

ISDN

One of the emerging technologies that will be key to the future

superhighway is the narrowband ISDN. Deployment of this technology is

the first step in the conversion from the existing networks to a fully digital

network. ISDN is an end-to-end digital network that is evolving from the

existing telephone network. It is already providing some users with direct

access to digital transmissions—at speeds ranging from 144,000 bits per

second (144 Kbps) to 1.544 Mbps—capable of handling many different forms

and types of information, including conventional analog voice, digital

voice, and packet data.

Because of poorly defined standards, the early implementations of ISDN

were plagued with interoperability problems. In an effort to effectively

manage the integration of the ISDN technology with the public switched

networks, the industry has adopted a set of standards known as the

National ISDN. National ISDN will include advance signaling capabilities, as

well as a wide range of digital services.

Telecommuting or work-at-home is one area where the benefits of ISDN

service can be readily identified. Currently, an employee working at home

may have to install additional telephone lines to handle computer and fax

communications. Using ISDN, the telecommuter can communicate—over a

single line—with the employer’s local area network, while simultaneously

carrying on a telephone conversation with a colleague and receiving a fax

from the employer’s office. Similarly, as shown in figure III.1, a large

business or institutional ISDN customer can use ISDN to consolidate voice,

data, and videoconferencing services.

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Appendix III 

Description of Advanced Technologies

Figure III.1: ISDN Architecture

ISDN

network

termination

Standard

interface

23 B+D channels

ISDN

network

termination

Standard

interface

2 B+D channels Circuit

switching

Signaling

Central Office

ISDN

exchange

termination

144 Kbps

Residence

Business

Public network

Local

area

network

Digital

PBX

Video

1.54 Mbps

Packet

switching

Source: Adapted from A Guide to New Technologies and Services, Bellcore, 1993; figure 4-1, pp.

4-7.

Advanced Signaling

and Intelligent

Networks

In order to offer new services and advanced capabilities, such as 800

number and ISDN services, the telephone industry is deploying common

channel signaling networks. These networks are based on the Signaling

System 7 (SS7) protocol. An SS7 network is a packet-switched

communications network that transports call control and signaling

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Appendix III 

Description of Advanced Technologies

messages on a dedicated high-speed data network separate from the voice

or data communications networks. The SS7 provides capabilities critical to

the development of advanced intelligent networks (AIN). A programmable

AIN network provides the capability for network switches to interrogate

remote processors, databases, and mobile communications devices. The

network intelligence resides in on-line, real-time databases, rather than in

every switch, and is accessed through the SS7 signaling system. Such

intelligent networks allow greater customer control, provide the tools for

the creation of virtual private networks, increase competition by allowing

competing carriers to use the AIN capabilities to offer custom services, and

provide the mechanisms for alternative call destination routing required by

the emerging personal communications services (PCS).1

 Figure III.2 shows

a simplified view of an AIN architecture.

1

PCS is a new type of service designed to support hand-held personal voice and data communications

terminals. Mobile PCS users are expected to be able to receive services such as high-quality voice,

data, facsimile, and video at any terminal anywhere the user has directed his or her calls.

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Appendix III 

Description of Advanced Technologies

Figure III.2: AIN Architecture

Transport lines

Signaling

circuit

Intelligent

peripheral

Operations

support

system

Service

switching

point

Database

Service

management

system

Signal

transfer

point

Intelligent

peripheral

Service

control

point

Operations

support

system

Service

switching

point

Database

Service

management

system

Signal

transfer

point

SS7

Common channel

signaling system

Digital

switch

Digital

switch

Service

control

point

Source: Adapted from A Guide to New Technologies and Services, Bellcore, 1993; figure 1-1, pp.

1-5.

B-ISDN Technologies The B-ISDN technology is a dramatic departure both from the existing

digital infrastructure and the narrowband ISDN concept. Because it will

provide transmission rates up to 2,488 Mbps, B-ISDN will not be able to use

the existing digital infrastructure, but will largely rely on the

Asynchronous Transfer Mode (ATM)/Synchronous Optical Network (SONET)

optical fiber networks. SONET, an international standard for optical carrier

networks, provides a variety of transmission rates in multiples of 

51.84 Mbps, with currently deployed optical circuits operating between 

156 to 622 Mbps, and with future circuits expected to operate at up to 2,488

Mbps. SONET will support B-ISDN using the ATM standard. While SONET is one

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Appendix III 

Description of Advanced Technologies

of the transmission technologies that provides the high-speed transmission

system required by the information superhighway, ATM will allow users to

transmit a rich mix of data during a single transmission session. Figure

III.3 provides an overview of the B-ISDN architecture.

Figure III.3: B-ISDN Architecture

Video

ATM

access

node

Local area networks

ATM cell

relay

Frame

relay

Switched

multi-megabit

data service

(SMDS)

SMDS

conectioneless

service

Circuit

switch

ATM

hub

switch

Public Switched ATM Network

Private

branch

exchange

ISDN

ATM

access

node

ATM

access

node

Source: Adapted from A Guide to New Technologies and Services, Bellcore, 1993; figure 2-6, pp.

2-11.

Much remains to be done to develop a global integrated B-ISDN network.

Although the local and long distance telephone companies are beginning

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Appendix III 

Description of Advanced Technologies

to deploy ATM/SONET networks, ATM standards are continuing to evolve. For

example, several standards, including service quality, transmission

routing, and encryption standards, have not yet been defined. The

Advanced Research Projects Agency and the National Science Foundation,

in coordination with industry, are actively pursuing investigations focused

on the development of ATM standards and network management tools.

These two agencies established five gigabit network research testbeds

focused on ATM network technology, alternative network architectures,

and applications. In addition, the Advanced Research Projects Agency is

evaluating the best commercial prototypes of ATM/SONET technology and

related applications, including ATM satellite connections and the

encryption of gigabit data streams.

Personal

Communications

Networks

Some observers believe that we are moving toward a ubiquitous, tetherless

global metanetwork composed of cellular and satellite communications

systems supplemented by wire-based ground networks. Personal

communications networks (PCN) and the related personal communications

services (PCS) are expected to be an important part of this tetherless

metanetwork. PCNs are based on a concept of tetherless digital

communications systems providing mobile users with worldwide

connectivity. Unlike the station-to-station connectivity provided by the

existing telephone systems, PCNs will provide person-to-person access

using a national—and potentially worldwide—personal numbering

concept.

Digital wireless communications, cellular systems, and the AIN capabilities

of the evolving B-ISDN networks are expected to play a crucial role in the

development of PCNs. Initially, PCNs will include a diverse mix of analog

and digital technologies and services—cellular systems, mobile satellite

systems, paging, and local area networks—based on radio access

technology and interfaced with the wire-based public networks. It is

expected that a full-scale PCN will deploy a combination of technologies,

mostly because the terrestrial wire and cellular networks will not provide

worldwide connectivity, particularly to users in remote areas. To achieve

this objective, the terrestrial cellular systems may be complemented by

space-based cellular type services.

There are two basic approaches to space-based PCNs. One uses satellites in

high geosynchronous earth orbit (GEO), while the other relies on a

constellation of low-earth orbit (LEO) satellites. The GEO systems, being in

higher orbit, require more power at both the transmitter and the receiver

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Description of Advanced Technologies

than the LEOs, but provide more earth coverage with fewer spacecraft. On

the other hand, LEO systems, while cheaper on a unit-basis, require far

more satellites to provide earth coverage. In general, most of the recently

proposed space-based PCNs are focused on LEO systems, including

Motorola’s Iridium system (77 satellites), TRW’s Odyssey system (12

satellites), Leosat’s system (18 satellites), and the recently announced

network of 840 satellites proposed by the Teledesic Corp. Figure III.4

show a typical LEO satellite network.

Figure III.4: Low Earth Orbit Satellite System

LEO Satellite

413 to 5,600 miles

Broadband in the

Local Loop

While industry is upgrading the transport layer and laying thousands of

miles of optical fiber, the on-ramps that will link the high-speed portions of

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Appendix III 

Description of Advanced Technologies

the national information infrastructure with homes, business, and

institutions continue to form a bottleneck to high-speed information flow.

In the near term, the primary challenge will be to provide broadband

digital services over the existing plant—the hundreds of thousands of

miles of copper wire and coaxial cable—although ultimately it may be

preferable to provide fiber optics to each residence. The replacement cost

for this “last mile” of the superhighway—linking the broadband backbone

with residences, business, and institutions—continues to be high, not only

because there is so much copper wire and coaxial cable to be replaced,

but also because of the need for special equipment to process the optical

signal on the customer’s premises.

The telephone and cable companies are adopting a mix of technologies

and strategies to cope with the bottleneck in the local loop—the portion of

the telephone communication circuit connecting individual subscribers

with the telephone company’s central office. For the telephone companies,

the most promising approaches are the asymmetrical digital subscriber

line and the fiber-to-the-curb architectures. The asymmetrical digital

subscriber line allows telephone companies to use a single copper wire to

simultaneously transmit video and telephone signals by increasing the

transmission speed from 64 Kbps to 1.5 Mbps while providing an upstream

channel between 16 to 384 Kbps. The fiber-to-the-curb architecture provides

high-capacity switched digital network services to optical network units

serving multiple residences. Optical network units house the necessary

equipment to convert the optical signals to electrical impulses and

distribute them to individual homes over a copper wire or coaxial cable.

Most of the newer or rebuilt cable systems also use a hybrid fiber

optics/coaxial cable architecture, commonly known as fiber trunk feeder.

This hybrid fiber optics/coaxial cable architecture is capable of supporting

all digital, fully switched ATM/SONET services. Figure III.5 highlights two

fiber-to-the-curb architectures that may be used by the telephone and

cable industries to deliver broadband services to subscribers.

Page 60 GAO/AIMD-95-23 Information Superhighway
Appendix III 

Description of Advanced Technologies

Figure III.5: Broadband in the Local Loop

Optical

network

unit

Existing cable TV or

telephone wiring

Remote

terminal

Fiber optics cable

Video

Telephone

TV cable

head end

Local

telephone

company

Optical

network

unit

8 homes

Coaxial cable

video/

telephone/

data and power

Fiber optics cable

Video/

telephone/

data

Information/

Service

Providers

Information/

service

providers

Optical

network

unit

Information/

Service

Providers

Optical

network

unit

12-24 homes

Fiber-to-the-Curb With Coaxial Cable Overlay

Fiber-to-the-Curb With Coaxial Cable Drop

Coaxial cable

video and

power

Page 61 GAO/AIMD-95-23 Information Superhighway
Appendix IV 

Ensuring the Portability of Telephone

Numbers Poses a Challenge

The ability of the public networks to efficiently route and deliver

electronic communications is heavily dependent on the efficient allocation

and use of a limited resource—the pool of available ten-digit telephone

numbers. In recent years, the proliferation of telecommunications services

and providers has placed increasing demands on this resource. More

importantly, new requirements, such as demands for (1) personal mobility,

whereby communications services are provided to individuals, rather than

to fixed geographic locations (for example geographic mobility), and

(2) number portability, whereby customers are able to change service

features and providers quickly without needing to change their telephone

number, will significantly alter the way we manage the numbering

resources.

The first demand—the provision of services to individuals rather than

fixed geographic locations—will be largely satisfied by emerging PCSs. PCSs

will exploit the capabilities of AIN and nongeographic telephone numbers

to provide wireless or land-line based services to “roaming” individuals.

The second demand—the assignment of a permanent “personal” telephone

number to individuals—will require the development of national or

regional databases containing the personal numbers and customer service

profiles. Although there are no insurmountable technical barriers to

number portability, industry’s experience with the development of full

portability for the 800 number services indicates that it will be a lengthy

and arduous process.1

The North American

Numbering Plan

Guides the

Management of

Numbering Resources

The basic telephone numbering scheme, known as the North American

Numbering Plan (NANP), was developed the Bell System. In 1984, following

the AT&T divestiture, the numbering plan functions performed by AT&T

were transferred to Bell Communications Research (Bellcore). Since that

time, Bellcore has served as the NANP administrator. Under NANP, each

telephone within the World Zone 12

 can be reached by dialing a unique

ten-digit number generally composed of three parts—a three-digit

geographic area code, a three-digit secondary code, and a four-digit

“station” or “line” code.

1

It took almost 7 years for industry to implement full portability for 800 service.

2

The World Zone 1 includes the United States, Canada, Bermuda, and most of the Caribbean. It

provides a uniform dialing scheme applicable in 18 countries, and serves more than a thousand local

exchange carriers, several hundred long distance carriers, and over one hundred million customers.

International calls to countries not included in the NANP require the dialing of country codes; thus

telephone numbers can differ in length from country to country.

Page 62 GAO/AIMD-95-23 Information Superhighway
Appendix IV 

Ensuring the Portability of Telephone

Numbers Poses a Challenge

However, under the current format, there are only 160 possible area codes.

These represent the number of combinations available when the first digit

cannot be zero or one, and the second digit is always zero or one. Sixteen

of the codes have a unique format: eight have a double “0” (“N00” codes)

and eight have a double “1” (“N11” codes). The N00 codes are called

Service Access Codes (SAC).3

 The most widely recognized SACs are the 800

and 900 codes. The N11 codes are known as “service codes” and are set

aside for special functions, the most widely used being the 911 emergency

code. All of the remaining 144 codes are assigned and it has been long

expected that the present stock of codes would be exhausted sometime in

the 1990s.

A numbering relief plan, scheduled to be implemented in January 1995,

will expand the number of potential codes from 160 to 800. This expansion

will be accomplished by allowing the second digit of the area code to

include the digits “2” through “9” in addition to “1” and “0”. For example,

area code 334 is scheduled to be placed in service in northern Alabama on

January 15, 1995. The addition of 640 new codes will not only significantly

increase the numbering resource, but may also provide additional codes

for nongeographic assignment such as the “personal” numbers needed for

PCS users. Because the new codes will not be available until 1995, carriers

anxious to offer PCS asked Bellcore for the assignment of one of the four

nongeographic codes (500 SAC) for PCS. The carriers plan to offer PCS that

includes personal mobility, terminal mobility, and service profile services,

but not, at least initially, number portability. In essence, PCS users would

have to be issued a new telephone number every time they changed a PCS

provider.

Portability Issues

Remain Unresolved

In June 1993, Bellcore informed the FCC that it had decided, absent

instructions to the contrary, to proceed with the assignment of 500 SAC for

PCS service to carriers that had expressed an urgent need for these

assignments. In response to Bellcore’s notification, the FCC requested

public comments on the proposed assignment of the 500 SAC for PCS, and

directed Bellcore to delay the assignments until it had a chance to

consider the comments. At the same time, FCC asked Bellcore to submit,

within 30 days, a detailed proposal for achieving 500 number portability. In

response, Bellcore noted that there were many ways to achieve number

portability, but did not offer a concrete proposal. An industry workgroup

is addressing the issue of PCS number portability. Bellcore began assigining

3

Three SACs (700, 800, and 900) are currently in use through World Zone 1; one (600) is assigned to the

Canadian government, while the 500 SAC has been assigned for roaming PCS.

Page 63 GAO/AIMD-95-23 Information Superhighway
Appendix IV 

Ensuring the Portability of Telephone

Numbers Poses a Challenge

numbering resources within the 500 SAC for roaming services after the FCC

considered the comments on the issue and gave its approval in May 1994.

Bellcore also notified the FCC that because of the many changes in the

telecommunications environment which have resulted in increased

controversy regarding numbering, Bellcore and its owners believed that it

was time to relinquish Bellcore’s voluntary administration of the NANP.

The FCC has yet to take final action in finding a replacement for Bellcore or

to act on the 500 SAC portability issues. According to the United States

Telephone Association, it appears unlikely that the initial PCS services will

provide number portability. Full national number portability may not be

available for years, given that the design and deployment of a database

architecture for the 500 SAC will take considerable time.

Page 64 GAO/AIMD-95-23 Information Superhighway
Appendix V 

Major Contributors to This Report

Accounting and

Information

Management Division,

Washington D.C.

Rona B. Stillman, Chief Scientist for Computers and Communications

Ronald W. Beers, Assistant Director

Mirko J. Dolak, Evaluator-in-Charge

John P. Rehberger, Staff Evaluator

Shane D. Hartzler, Reports Analyst

Susan B. Willson, Secretary

Office of General

Counsel

John A. Carter, Senior Attorney

Resources,

Community, and

Economic

Development Division

Paul J. O’Neill, Assistant Director

Edmond E. Menoche, Senior Evaluator

Boston Regional

Office

Bruce Holmes, Assistant Director

Page 65 GAO/AIMD-95-23 Information Superhighway
Glossary

The definitions in this glossary are drawn from several sources, including

the Computer Dictionary: The Comprehensive Standards for Business,

School, Library, and Home, Microsoft Press, 1991, Washington, D.C.; The

McGraw-Hill Telecommunications Factbook, McGraw-Hill, New York,

1993; The New IEEE Standard Dictionary of Electrical and Electronic

Terms, The Institute of Electrical and Electronic Engineers, New York,

1993; and the Auerbach Data Communication Management, Auerbach

Publishers, Pennsauken, New Jersey, 1994.

Address A sequence of bits or characters that identifies the destination and the

source of a transmission.

Advanced Intelligent

Network

An evolving architecture that allows rapid creation and modification of

telecommunications services.

Agile Manufacturing An approach to industrial production that allows a manufacturer to rapidly

respond to market demand by reducing the time it takes to design and

manufacture a product. Also known as rapid response or demand

activated manufacturing.

Amplitude A relative magnitude of a signal.

Analog A term applied to any device, usually electronic, that represents values by

a continuously variable physical property, such as voltage in an electronic

circuit. An analog device can represent an infinite number of values within

the range the device can handle. In contrast, digital representation maps

values onto discrete numbers, limiting the possible range of values to the

resolution of the digital device.

Analog Signal A continuous electrical signal whose amplitude varies in direct correlation

with the original input.

Architecture A general term referring to the structure of all or part of a computer

system. The term also covers the design of system software, such as the

operating system, as well as refers to the combination of hardware and

basic software that links the machines on a computer network. Computer

architecture refers to an entire structure and to the details needed to make

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Glossary

it functional. Thus, computer architecture covers computer systems, chips,

circuits, and system programs, but typically does not cover applications,

which are required to perform a task but not to make the system run.

Asynchronous Operation Generally, an operation that proceeds independently of any timing

mechanism, such as a clock. In communications, for example, two

modems communicating asynchronously rely upon each one sending the

other start and stop signals in order to pace the exchange of information.

Asynchronous Transfer

Mode

A fast-packet technology that was developed for use in area networks

using fixed-length cells. Current ATM standards allow it to scale from

speeds of 155 Mbps to 622 Mbps over fiber networks. ATM appears to be the

best alternative for multimedia applications where data are mixed with

voice, images, or full-motion video.

Bandwidth In communications, the difference between the highest and lowest

frequencies in a given range. For example, a telephone accommodates a

bandwidth of 3000 hertz (Hz), the difference between the lowest (300 Hz)

and highest (3300 Hz) frequencies it can carry. In computer networks,

greater bandwidth indicates faster data-transfer capabilities.

Basic Rate Interface Transmission rates for the integrated service digital network. Basic rate

interface consists of two 64 Kbps channels and one 16 Kbps channel

packet-switched data channel used for signaling and packet data

transmission functions.

Bit Short for “binary digit”; either 1 or 0 in the binary number system. In

processing and storage, a bit is the smallest unit of information handled by

a computer and is represented physically by an element such as a single

pulse sent through a circuit or a small spot on a magnetic disk capable of

storing either a 1 or a 0. Considered singly, bits convey little information a

human would consider meaningful. In groups of eight, however, bits

become the familiar bytes used to represent all types of information,

including the letters of the alphabet and the digits.

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Glossary

Broadband Network A type of local area network on which transmissions travel as

radio-frequency signals over separate inbound and outbound channels.

Stations on a broadband network are connected by coaxial or fiber-optic

cable. The cable itself can be made to carry data, voice, and video

simultaneously over multiple transmission channels. This complex

transmission is accomplished by the technique called frequency-division

multiplexing, in which individual channels are separated by frequency and

buffered from one another by guard bands of frequencies that are not used

for transmission. A broadband network is capable of high-speed operation

(20 megabits or more), but it is more expensive than a baseband network

and can be difficult to install. Such a network is based on the same

technology as is used by cable television. Broadband transmission is

sometimes called wideband transmission.

Capstone Chip A data security chip. The Capstone chip, also known as MYK-80,

incorporates NSA’s Skipjack, key exchange algorithms, and the NIST digital

signature and secure hash algorithms.

Cell In cellular systems, the smallest geographic area defined for mobile

communications systems.

Cellular Systems Mobile telephony systems employing hexagonal geographic areas, or cells,

with group frequencies allocated to each cell. Typically, seven cells make a

block, and no adjacent cell uses the same set of frequencies.

Ciphertext The encrypted form of a plaintext message or data.

Circuit Switching A method of opening communications lines, as through the telephone

system, creating a physical link between the initiating and receiving

parties. In circuit switching, the connection is made at a switching center,

which physically connects the two parties and maintains an open line

between them for as long as needed. Circuit switching is typically used in

modem communications on the dial-up telephone network, and it is also

used on a smaller scale in privately maintained communications networks.

Clipper Chip A microcircuit that contains a classified secret-key encryption algorithm

known as Skipjack. The Clipper chip family, manufactured by Mykotronx,

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Glossary

Inc., includes three prototypes chips—the MYK-78E, MYK-78T, and

MYK-77. MYK-78E and MYK-78T are designed for wirebased digital

telephony. MYK-77 is designed for use in digital radios operating at low

data rates. Also see Capstone Chip.

Coaxial Cable Often referred to as coax or coax cable. A cable that consists of two

conductors, a center wire inside a cylindrical shield that is grounded. The

shield is typically made of braided wire and is insulated from the center

wire. The shield minimizes electrical and radio-frequency interference;

signals in a coaxial cable do not affect nearby components, and potential

interference from these components does not affect the signal carried on

the cable.

Code Division Multiple

Access

A cellular digital standard that deploys frequency hopping—rapid change

of frequency—with the carrier frequency continually shifted through a

wideband channel.

Common Channel

Signaling

A method of carrying signaling and supervisory information between

telephone central offices in a separate, dedicated channel.

Communications Protocol A set of rules or standards designed to enable computers to connect with

one another and to exchange information with as little error as possible.

The word “protocol” is used, sometimes confusingly, in reference to a

multitude of standards affecting different aspects of communication. Some

standards affect hardware connections, while other standards govern data

transmission. Still other protocols govern file transfer, and others define

the methods by which messages are passed around the stations on a local

area network. Taken as a whole, these various and sometimes conflicting

protocols represent attempts to facilitate communication among

computers of different makes and models.

Computer Network A group of computers and associated devices that are connected by

communications facilities. A network can involve permanent connections,

such as cables, or temporary connections made through telephone or

other communications links. A network can be as small as a local area

network consisting of a few computers, printers, and other devices, or it

can consist of many small and large computers distributed over a vast

geographic area. Small or large, a computer network exists to provide

Page 69 GAO/AIMD-95-23 Information Superhighway
Glossary

computer users with the means of communicating and transferring

information electronically. Some types of communication are simple

user-to-user messages; others, of the type known as distributed processes,

can involve several computers and the sharing of workloads or

cooperative efforts in performing a task.

Cryptanalysis The process of converting encrypted messages into plaintext without

knowledge of the key employed in the encryption algorithm.

Cryptography The transformation of ordinary text—or plaintext—and other data into

coded form by encryption and the transformation of the coded text or data

back to plaintext or data by decryption.

Cryptographic Algorithm A mathematical procedure used for such purposes as encrypting and

decrypting messages and signing documents digitally.

Cryptographic System The hardware, software, documents, and associated techniques and

processes that together provide a means of encryption.

Data Encryption Standard A NIST Federal Information Processing Standard and a commonly used

secret-key cryptographic algorithm for encrypting and decrypting data.

Digital Related to digits or the way they are represented. In computing, digital is

virtually synonymous with binary because the computers familiar to most

people process information coded as combinations of binary digits, or

bits—zeros and ones. One bit can represent at most two values—0 or 1.

Two bits can represent up to 4 different values—00, 01, 11, and 10. Eight

bits can represent 256 values—00000000, 00000001, 00000011, and so on.

Digital Signature A cryptographic method, provided by public-key cryptography, used by a

message’s recipient or any third party to verify the identity of the

message’s sender and the integrity of the message. A sender creates a

digital signature or a message by transforming the message with his or her

private key. A recipient, using the sender’s public key, verifies the digital

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Glossary

signature by applying a corresponding transformation to the message and

the signature.

Digital Signature Standard A NIST Federal Information Processing Standard that supports digital

signature.

Electronic Signature See digital signature.

Encryption The transformation of data into a form readable only by using the

appropriate key, held only by authorized parties. The key rearranges the

data into its original form by reversing the encryption.

Escrow Encryption

Standard

A Federal Information Processing Standard specifying technology that

provides a mechanism for the secure escrow of encryption keys, which

can be used to intercept message only by government officials acting

under proper legal authorization. The standard relies on a key escrow

chip, known as Clipper, programmed with the classified Skipjack

algorithm. Also see Clipper Chip, Capstone Chip, Skipjack, key escrow

system, private key, public key cryptography.

Fiber-Optics A method of transmitting light beams along optical fibers. A light beam,

such as that produced in a laser, can be modulated to carry information. A

single fiber-optic channel can carry significantly more information than

most other means of information transmission. Optical fibers are thin

strands of glass or other transparent material.

Frame Relay A type of fast packet technology using variable length packets called

frames. By contrast, a cell relay system, such as ATM, transports user data

in fixed-sized cells.

Geosynchronous Orbit The orbit of a satellite in which the speed and path are precisely timed to

position it 22,300 miles over a fixed location on Earth.

Giga A prefix for one billion (109

) times a specific unit.

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Glossary

Gigabyte The precise meaning often varies with the context; strictly, a gigabyte is

1 billion bytes. In reference to computers, however, bytes are often

expressed in multiples of powers of two. Therefore, a gigabyte can also be

either 1,000 megabytes or 1,024 megabytes, where a megabyte is

considered to be 1,048,576 bytes.

Global System for Mobile

Communications

A European standard for digital cellular services.

Hacker A person who accesses or attempts to access a computer without

authorization. For the purpose of this report, the term hacker refers to an

external threat of unauthorized access to communications networks and

related systems.

Hash Function A technique for computing a hash total. Hash total is an error-checking

value derived from the addition of a set of numbers taken from text or

data. In cryptography, the recipient may use the hash function to verify a

message’s integrity by recalculating and verifying the hash total. If the two

do not match, the original information has been changed in some way.

Hertz A unit of frequency equal to one cycle per second.

Information Superhighway A popular term for the emerging global broadband digital metanetwork.

Also known as the national information infrastructure, infobahn, or global

grid.

Interactive Operating in a back-and-forth, often conversational manner, as when a

user enters a question or command and the system immediately responds.

Microcomputers are interactive machines; this interactivity is one of the

features that make them approachable and easy to use.

International Data

Encryption Algorithm

A block-encryption algorithm that operates on 64 bits of plaintext at a

time. Developed by James Massay and Xuejia Lai at ETH, a technical

institute in Zurich, the International Data Encryption Algorithm (IDEA) is

perceived as a potential replacement for Data Encryption Standard. Also

see Pretty Good Privacy.

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Glossary

Internet Abbreviation for “internetwork.” In communications, a set of computer

networks—possibly dissimilar—joined together by means of gateways that

handle data transfer and the conversion of messages from the sending

network to the protocols used by the receiving network (with packets if

necessary). When capitalized, the term “Internet” refers to the collection of

networks and gateways that use the Transmission Control

Protocol/Internet Protocol suite of protocols.

Interoperability The ability of two or more systems or components to exchange

information and to use the information that has been exchanged.

ISDN Abbreviation for “Integrated Services Digital Network”—a worldwide

digital communications network evolving from existing telephone

services. The goal of ISDN is to replace the current analog telephone system

with totally digital switching and transmission facilities capable of

carrying data ranging from voice to computer transmissions, music, and

video. ISDN is built on two main types of communications channels: a B

channel, which carries data at a rate of 64 Kbps (kilobits per second), and a

D channel, which carries control information at either 16 or 64 Kbps.

Computers and other devices are connected to ISDN lines through simple,

standardized interfaces. When fully implemented (possibly around the turn

of the century), ISDN is expected to provide users with faster, more

extensive communications services.

Japanese Digital Cellular A Japanese standard for digital cellular services.

Key A long stream of seemingly random bits used with cryptographic

algorithms. The keys must be known or guessed to forge a digital signature

or decrypt an encrypted message.

Key Escrow System A mechanism for the secure escrow, and controlled release, of secret or

private encryption keys to law enforcement officials. Also see Escrow

Encryption Standard.

Kilo A prefix for one thousand (103

) times a specific unit.

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Glossary

Last Mile A popular term for the last segment of the connection between a

communication provider and the customer. Also see local loop and

on-ramps.

Local Area Network A group of computers and other devices dispersed over a relatively limited

area and connected by a communications link that enables a device to

interact with any other on the network. Local area networks (LANs)

commonly include microcomputers and shared (often expensive)

resources such as laser printers and large hard disks. Most modern LANs

can support a wide variety of computers and other devices. Each device

must use the proper physical and data-link protocols for the particular LAN,

and all devices that want to communicate with each other on the LAN must

use the same upper-level communications protocol. Although single LANs

are geographically limited (to a department or an office building, for

example), separate LANs can be connected to form larger networks. Similar

LANs are linked by bridges that act as transfer points between networks;

dissimilar LANs are linked by gateways, which both transfer data and

convert it according to the protocols used by the receiving network.

The devices on a LAN are known as nodes, and the nodes are connected by

cables through which messages are transmitted. Types of cables include

twisted-pair wiring, coaxial cable, or fiber-optic (light-transmitting) cable.

Nodes on a LAN can be wired together in any of three basic layouts, known

as bus, ring, and star. As implied by their names, a bus network is more or

less linear, a ring network forms a loop, and a star network radiates from a

central hub. To avoid potential collisions when two or more nodes attempt

to transmit at the same time, LANs use either contention and collision

detection or token passing to regulate traffic.

Local Loop A communication circuit connecting the telephone company central office

with a subscriber’s instrument. Also see last mile and on-ramps.

Mega Abbreviated M. A prefix meaning 1 million (106

). In computing, which is

based on the binary (base-2) numbering system, mega has a literal value of

1,048,576, which is the power of 2 closest to one million.

Megabit Abbreviated Mb or Mbit. Usually, 1,048,576 bits; sometimes interpreted as

1 million bits.

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Glossary

Megabyte Abbreviated MB. Either 1 million bytes or 1,048,576 bytes.

Metanetwork A “super” network connecting many other networks. A network of

networks.

Multicast A variant of broadcast, where information can be sent to selected

recipients instead of all subscribers of a particular communications

system.

Multimedia A popular term for the integration of information in a single format, for

example an electronic document that may contain text, embedded voice,

video, or images.

Narrowband Network A flexible, all purpose, two-way medium that supports transmission rates

under 1.5 Mbps. Also see broadband network.

National Information

Infrastructure

The administration’s term for the information superhighway.

Network Architecture The underlying structure of a computer network, including hardware,

functional layers, interfaces, and protocols (rules) used to establish

communications and ensure the reliable transfer of information. Because a

computer network is a mixture of hardware and software, network

architectures are designed to provide both philosophical and physical

standards for enabling computers and other devices to handle the

complexities of establishing communications links and transferring

information without conflict. Various network architectures exist, among

them the internationally accepted seven-layer open systems

interconnection model and International Business Machine (IBM) Systems

Network Architecture. Both the open systems interconnection model and

the Systems Network Architecture organize network functions in layers,

each layer dedicated to a particular aspect of communication or

transmission and each requiring protocols that define how functions are

carried out. The ultimate objective of these and other network

architectures is the creation of communications standards that will enable

computers of many kinds to exchange information freely.

Page 75 GAO/AIMD-95-23 Information Superhighway
Glossary

North American

Dual-Mode Cellular System

A North American standard for digital cellular services.

On Ramp A popular term for a digital broadband connection linking a subscriber

with the information superhighway. Also see local loop and last mile.

Operating System The software responsible for controlling the allocation and usage of

hardware resources such as memory, the central processing unit, disk

space, and peripheral devices.

Optical Fiber A lightguide for electromagnetic waves traveling in the infrared and visible

light spectrum. An optical fiber consists of two different types of glass,

core and cladding, surrounded by a protective coating. The core is the

light-guiding region of the fiber, while the cladding ensures that the light

pulses remain within the core. One mile of fiber, capable of transmission

speeds of 2,500 Mbps (2.5 gigabits per second) weighs about 1/7 of a pound.

A copper cable with the same information-carrying capacity would weigh

33 tons.

Packet In general usage, a unit of information transmitted as a whole from one

device to another on a network. In packet-switching networks, a packet is

defined more specifically as a transmission unit of fixed maximum size

that consists of binary digits representing both data and a header

containing an identification number, source and destination addresses,

and, sometimes, error-control data.

Packet Switching A message-delivery technique in which small units of information

(packets) are relayed through stations in a computer network along the

best route currently available between the source and the destination. A

packet-switching network handles information in small units, breaking

long messages into multiple packets before routing. Although each packet

may travel along a different path, and the packets composing a message

may arrive at different times or out of sequence, the receiving computer

reassembles the original message. Packet-switching networks are

considered to be fast and efficient. To manage the tasks of routing traffic

and assembling/disassembling packets, such networks require some

“intelligence” from the computers and software that control delivery.

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Glossary

Personal Communications

Network

Advanced cellular communications and the internetworking of both wire

and wireless networks that are expected to offer new communications

services via very small portable handsets. The network will rely on

microcellular technology—many low-power, small-coverage cells—and a

common channel signaling technology, to provide a wide variety of

features in addition to the basic two-way telephone service.

Plaintext Plain, unencrypted text or data.

Point of Presence A long distance carrier’s network access facility located within the service

area of a local telephone company.

Pretty Good Privacy A cryptographic software application for the protection of computer files

and electronic mail. It combines the convenience of the

Rivest-Shamir-Adelman public key algorithm with the speed of the

secret-key IDEA algorithm, digital signature, and key management. It was

developed by Philip Zimmerman, and is available globally as freeware

from Internet sites or as commercial software.

Primary Rate Interface A transmission rate interface for the integrated service digital network. It

consists of 23 64 Kbps channels and one 64 Kbps channel used for signaling.

Six of the 64 Kbps channels can be combined into a single 384 Kbps channel,

or 24 64 Kbps channels can be combined to form a single 1.536 Mbps

channel. These bundles can support applications requiring high data rates,

such as video or host-to-host bulk data transfers.

Private Key The undisclosed key in a matched key pair—private key and public

key—used in public key cryptographic systems.

Private Branch Exchange A private telephone exchange connected to the public telephone network.

Public Key The key in a matched key pair—private key and public key—that is made

public, for example, posted in a public directory, for public key

cryptography.

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Glossary

Public Key Cryptography Cryptography using two matched keys (or asymmetric cryptography) in

which a single private key is not shared by a pair of users. Instead, each

user has a key pair. Each key pair consists of a private key that is kept

secret by the user and a public key that is posted in a public directory.

Public key cryptography is used to perform (1) digital signature, (2) secure

transmission or exchange of secret keys, and/or (3) encryption and

decryption.

Real-Time System A computer and/or a software system that reacts to events before the

events become obsolete. For example, airline collision avoidance systems

must process radar input, detect a possible collision, and warn air traffic

controllers or pilots while they still have time to react.

Rivest-Shamir-Adelman

Algorithm

A public key algorithm invented by Ronald L. Rivest, Adi Shamir, and

Leonard M. Adelman. The algorithm can be used to generate digital

signatures, encrypt messages, and provide key management for Data

Encryption Standard and other secret key algorithms.

Secret Key The single key that two or more parties share and keep secret for secret

key cryptography. Given secret key algorithms of equal strength, the

approximate difficulty of decrypting encrypted messages by brute force

search can be measured by the number of possible keys. For example, a

key length of 56 bits is over 65,000 times stronger or more resistant to

attack than a key length of 40 bits.

Secret Key Cryptography Cryptography based on a single key (or symmetric cryptography). It uses

the same secret key for encryption and decryption.

Signaling The process of generating and exchanging information between

components of telecommunications systems to establish, monitor, or

release connections (call handling functions) and to control related

network and system operations and functions.

Signaling System 7 An international common channel signaling system.

Page 78 GAO/AIMD-95-23 Information Superhighway
Glossary

Skipjack A classified encryption algorithm. Skipjack provides high-speed

encryption when implemented in a Clipper chip.

Standard In computing, a set of detailed technical guidelines used as a means of

establishing uniformity in an area of hardware or software development.

Computer standards have traditionally developed in either of two ways.

The first, a highly informal process, occurs when a product or philosophy

is developed by a single company and, through success and imitation,

becomes so widely used that deviation from the norm causes compatibility

problems or limits marketability. This type of de facto standard setting is

typified by such products as Hayes modems and IBM Personal Computers.

The second type of standard setting is a far more formal process in which

specifications are drafted by a cooperative group or committee after an

intensive study of existing methods, approaches, and technological trends

and developments. The proposed standards are later ratified by consensus

through an accredited organization and are adopted over time as products

based on the standards become increasingly prevalent in the market.

Synchronous Operation Generally, any operation that proceeds under control of a clock or timing

mechanism.

Synchronous Optical

Network (SONET)

An international standard for transmitting information over optical fiber at

high speeds.

Synchronous Transmission The serial transmission of a bit stream in which each bit occurs at a fixed

time interval and the entire stream is preceded by a specific combination

of bits that initiate the timing.

T-Carrier System A hierarchy of digital transmission capabilities designed to operate at

various rates, designated T1 (1.544 Mbps), T2 (6.312 Mbps), T3 (44.736 Mbps),

and T4 (274.176 Mbps).

Telecommunications A general term for the electronic transmission of information of any type,

including data, television pictures, sound, facsimiles, and so on.

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Glossary

Telecommuting Also called electronic commuting. The practice of working in one location

(often, at home) and communicating with a main office in a different

location through a personal computer equipped with a modem and

communications software.

Time Division Multiple

Access

A digital encoding scheme used in cellular service, this transmission

method allows users to simultaneously transmit on the same frequency by

allocating each user a discrete time slot.

Trojan Horse A computer program that conceals harmful code. A Trojan horse usually

masquerades as a useful program that a user would wish to execute.

Twisted-Pair Wire A wire made of two separately insulated strands of wire twisted together.

Virus A computer program that can infect, replicate, and spread among

computer systems. Unlike the computer worm, a virus requires human

involvement (usually unwitting) to propagate.

Wide Area Network A communications network that connects geographically separated areas.

Wiretapping The real-time collection of transmitted voice or data, and the sending of

that data in real time to a listening device. (“Real time” is defined as the

actual time that something, such as communication of information, takes

place.)

Worm An independent computer program that reproduces by copying itself from

one system to another while traveling from machine to machine across the

network. Unlike computer viruses, worms do not require human

involvement to propagate. Most worms and viruses are closely

related—they both spread and reproduce and their effects can be

identical.

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Page 81 GAO/AIMD-95-23 Information Superhighway
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Page 82 GAO/AIMD-95-23 Information Superhighway
Glossary

Page 83 GAO/AIMD-95-23 Information Superhighway
Related GAO Products

Information Superhighway: Issues Affecting Development (GAO/RCED-94-285,

Sept. 30, 1994).

Electronic Surveillance: Technologies Continue to Pose Challenges

(GAO/T-AIMD-94-173, Aug. 11, 1994).

IRS Automation: Controlling Electronic Filing Fraud and Improper Access

to Taxpayer Data (GAO/T-AIMD/GGD-94-183, July 19, 1994).

Communications Privacy: Federal Policy and Actions (GAO/OSI-94-2, Nov. 4,

1993).

IRS Information Systems: Weaknesses Increase Risk of Fraud and Impair

Reliability of Management Information (GAO/AIMD-93-34, Sept. 22, 1993).

Telecommunications: Interruptions of Telephone Service (GAO/RCED-93-79FS,

Mar. 5, 1993).

FBI: Advanced Communications Technologies Pose Wiretapping

Challenges (GAO/IMTEC-92-68BR, July 17, 1992).

Economic Espionage: The Threat to U.S. Industry (GAO/T-OSI-92-6, Apr. 29,

1992).

Computer Security: Hackers Penetrate DOD Computer Systems

(GAO/T-IMTEC-92-5, Nov. 20, 1991).

Computers and Privacy: How the Government Obtains, Verifies, Uses, and

Protects Personal Data (GAO/IMTEC-90-70BR, Aug. 3, 1990).

Computer Security: Unauthorized Access to a NASA Scientific Network

(GAO/IMTEC-90-2, Nov. 13, 1989).

Computer Security: Virus Highlights Need for Improved Internet

Management (GAO/IMTEC-89-57, June 12, 1989).

(510963) Page 84 GAO/AIMD-95-23 Information Superhighway
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