THE PRESIDENT’S 

NATIONAL SECURITY TELECOMMUNICATIONS 

ADVISORY COMMITTEE 

INTERNET SECURITY/ARCHITECTURE 

TASK FORCE REPORT

DEFINING THE EDGE OF THE INTERNET

June 25, 2003 

President’s National Security Telecommunications Advisory Committee 

INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT i 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY ..................................................................................................................ES-1 

1.0 INTRODUCTION AND CHARGE..................................................................................................1 

2.0 DISCUSSION .....................................................................................................................................1 

2.1 Defending the National Edge Is Critical—Defining the National Edge Is Not........ 1 

2.1.1 Non-Routing Systems ................................................................................... 2 

2.1.2 The Composition of Information Systems...................................................... 2 

2.1.3 Zones of Responsibility ................................................................................. 3 

2.2 Factors That Should Not Define the Edge ............................................................ 3 

2.2.1 The Internet Edge Should Not Be Defined Geographically ........................... 3 

2.3.2 The Internet Edge Should Not Be Defined By Applications........................... 4 

2.3.3 The Internet Edge Should Not Be Defined By The Terminal ......................... 4 

3.0 DEVELOPING KEY WARNINGS AND INDICATORS..............................................................4 

3.1 Finding the Edge For Red Networks..................................................................... 5 

4.0 CONCLUSIONS.................................................................................................................................5 

5.0 RECOMMENDATIONS...................................................................................................................6 

APPENDIX A—TASK FORCE MEMBERS, OTHER PARTICIPANTS, AND BRIEFERS........A-1 

President’s National Security Telecommunications Advisory Committee 

INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT ES-1 

EXECUTIVE SUMMARY 

During the President’s National Security Telecommunications Advisory Committee (NSTAC) 

XXV Principals’ Meeting of March 12–13, 2002, concern was expressed over the ability to 

protect the “edges” of the Internet against attack or exploitation. In response to these concerns, 

the NSTAC formed the Internet Security/Architecture Task Force (ISATF) and tasked the group 

to provide guidance to the President on how to define the edge of the Internet. The ISATF 

developed this report in response to the NSTAC tasking. 

Through detailed analysis, the ISATF determined that because the Internet is not a single 

network but a network of interconnected networks, no single definition of the edge exists. 

Although an Internet service provider’s (ISP) view of the edge may be the end-user customer at a 

home computer or the dial-up modem bank from which those end users gain access to the 

network, a backbone ISP may view the edge as the point where another ISP interconnects with 

the backbone network. The ISATF noted that three different, additional ways to define the edge 

include, but are not limited to, all systems that contain Internet Protocol (IP) addresses that do 

not route IP packets; the composition of information systems; and zones of responsibility for 

network operators versus end users. In addition, the group noted that the adoption of a single 

definition of the edge could prevent critical security precautions from being addressed in other 

areas. 

The ISATF also identified several factors that should not be used to define the edge of the 

Internet: geographic, physical boundaries lacking physical connection to the networks that 

compose the Internet; applications; and the needs of home users and small businesses. 

As there is no single definition of the edge of the Internet, the ISATF agreed that further 

discussion to define the edge is not critical. Instead, additional attention should be given to 

defending the Internet as a whole. The ISATF suggested that efforts be undertaken by 

Government to identify the critical NS/EP missions and functions supporting those missions that 

rely on the Internet and encourage the parties responsible for those missions to ensure that they 

are adequately protected through redundancy and alternate capabilities. Industry, standards 

bodies, software vendors, equipment vendors, network operators, and end users of all products 

and services that make up the Internet should ensure that these products have built-in baseline 

security features and that these features are appropriately configured and kept up to date. 

Finally, Government should work with industry to identify key warnings and indicators that 

service providers can use as a baseline to measure security threats and trigger notification 

processes to relevant stakeholders. On the basis of its analysis of issues related to defining the 

edge of the Internet, the NSTAC offers the following recommendations: 

The NSTAC recommends that — 

The Government should continue its work to identify the critical NS/EP missions and 

functions supporting those missions that rely on the Internet and encourage the parties 

responsible for those missions to ensure that they are adequately protected through 

redundancy and alternate capabilities; 
D R A F T 

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ES-2 INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT 

Industry, standards bodies, software vendors, equipment vendors, network operators and 

end users of all products and services that make up the Internet should ensure that these 

products have built-in baseline security features and that these capabilities are 

appropriately configured and kept up to date; and 

The Government should work with Internet security experts and standards bodies to 

develop a standard set of “key warnings and indicators” that all service providers can use 

as a baseline to measure security threats. 
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INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT 1 

1.0 INTRODUCTION AND CHARGE 

During the President’s National Security Telecommunications Advisory Committee (NSTAC) 

XXV Principals’ Meeting of March 12–13, 2002, concern was expressed over the ability to 

protect the “edges” of the Internet against attack or exploitation. To defend the edge, it is first 

necessary to define the edge and to understand the relevant perimeter that is needed to protect the 

Nation’s critical infrastructures. However, there is no universal definition for the edge of the 

Internet. Many consider the Internet borderless or without any edge. Some consider the edge of 

the Internet to be the end-user terminal level—the millions and millions of desktops in homes 

and small businesses around the Nation and around the world—while others believe it to be the 

point at which an Internet service provider (ISP) interconnects with the backbone network. 

Consequently, the task force concluded that to protect the critical infrastructure of the United 

States, the focus should involve all elements of the Internet rather than attempt to focus security 

efforts at the edge. Security practices throughout the Internet must be as fluid and dynamic as 

the Internet itself. 

2.0 DISCUSSION 

2.1 Defending the National Edge Is Critical—Defining the National Edge Is Not 

During the NSTAC Principals’ meeting, participants sought a definition for the boundaries and 

edge of the Internet, and the means by which the boundaries and edge can be monitored. There 

are many different interpretations and definitions of the edge of the Internet. The concept, 

however, is clouded by the fact that the Internet is not a single, tangible thing, but a fabric of 

separate and distinct networks that are interconnected. Instead of a single edge, there is an everchanging series of concentric circles that make up the Internet, extending all the way to the end 

device or user. This dynamic network of networks results in a perspective of the domain under 

one’s management control based on where that individual sits in the overall architecture at any 

point in time. For instance, the edge concept as defined by the operators of the backbone 

networks—the large, long-haul fibers that help bring hundreds or thousands of networks 

together—may differ from that of the ISP network operators, which can either own a network or 

lease fiber from backbone operators or from network operators at large corporations or 

universities that can also act as de facto ISPs. 

The definition of the edge may even vary within the ISP and backbone operator communities 

themselves. For ISPs, the end-user customer could be considered the edge, as could the dial-up 

modem bank accessed by those end users. For backbone providers, the edge could be the point 

at which an ISP interconnects with the backbone, or it could be the outermost edge of the 

downstream ISP. Both definitions are equally plausible. 
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Other methods of defining the edge include the following: 

Non-routing systems—all the systems with Internet Protocol (IP) addresses that do not 

route IP packets, e.g., leaf nodes;1

The composition of information systems; or 

Zones of responsibility—the space between the network operator’s zone of responsibility 

and the end-user’s zone of responsibility. This could be considered the boundary 

between a customer edge and a provider edge.2

2.1.1 Non-Routing Systems 

As noted in Request for Comment (RFC) 1958, the most robust end-to-end network functions are 

realized by end-to-end protocols. By keeping information about the end-to-end communications 

at the edge of the network, the network becomes more secure. Information about the state of 

end-to-end communications “should be maintained only in the endpoints, in such a way that the 

[end-to-end communications] can only be destroyed when the endpoint itself breaks (known as 

fate-sharing).”3 

2.1.2 The Composition of Information Systems 

The composition of information systems is important to the edge discussion because the Internet 

must accomplish business functions, e.g., e-commerce, e-government, to be considered useful. 

The components of an information system are as follow: 

The infrastructure, e.g., the Internet and the local access (including wireless systems) 

right out to the wall plug (utility model); 

The performing (user) computing elements or the “seats”; and 

The software applications. 

In this case, the edge is the wall plug because users do not want to “own” the seats or take 

responsibility for the applications when viewed from an Internet provider perspective. It is 

necessary to monitor the security and performance of the edge to maintain the ultimate business 

applications/continuity. 

 

1 This concept is consistent with the Internet Engineering Task Force’s (IETF) RFC 1958, Architectural Principles of the 

Internet. RFC 1958 defines an end-to-end argument for implementing complex functions. One could interpret “end” as 

“edge” from this context, which would assert that “certain required end-to-end functions can only be performed correctly by 

the end-systems themselves.” RFC 1958 at 2.3, p. 2.

2 The IETF’s Provider Provisioned VPN Working Group is currently studying this issue. The customer edge, or customer 

edge device, “faces the users at a customer site that has an access connection to a provider edge (PE) device. It may be a 

router switching-router, or a switch that allows users at a customer site to communicate over the access network with other 

sites in the VPN.” Provider edge devices are defined as “facing the provider network on one side and attached via an access 

connection over one or more access networks to one or more consumer electronic devices. It may be a router or a switching 

router.” 

3 RFC 1958 at 2.3, p.2-3. 
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INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT 3 

2.1.3 Zones of Responsibility 

Each network service provider or ISP is responsible for the equipment it needs to operate and 

maintain its network. This responsibility can include equipment that it owns and operates on the 

premises of one of its customers as well as equipment that it leases to a customer and maintains 

under a service agreement. If a piece of equipment fails or a group of customers experience 

latency or packet loss issues, the network operator or ISP responds accordingly. In this instance, 

the edge is the point at which the network service provider or ISP no longer has responsibility to 

act to protect its own assets, or by contract, the assets of its customers. 

Nevertheless, instead of defining the edge, emphasis should be placed on defending the edge 

because the adoption of a single definition of the edge may prevent critical security precautions 

from being addressed in other areas. The concept of a single edge is impractical because the 

Internet is not a single network. Defensive measures focused only at the edge of a network are 

less effective than security measures employed in every software application and network 

element that constitutes the Internet. All network operators have responsibility for their 

networks and all of their components that make up the network. By encouraging network 

operators to regularly scan, monitor, and maintain not only the perimeter but the interior of the 

network, the Internet as a fabric becomes stronger. Treating each network as a separate and 

distinct component of the Internet allows for the reasonable identification of areas of 

responsibility for network security as defined and controlled by the individual network 

administrators. Responsibility for security can be extended to the users of the network through 

customer agreements, acceptable use policies, or terms and conditions. 

2.2 Factors That Should Not Define the Edge 

The Internet edge should not be defined using any of the following factors: 

Geographically by physical boundaries lacking physical connection to the networks that 

compose the Internet as a whole; 

By applications, such as e-mail or the World Wide Web, neither of which should be 

considered an acceptable boundary for the Internet; or 

By the needs of home users and small business users. 

2.2.1 The Internet Edge Should Not Be Defined Geographically 

Due to its continually evolving configuration, the Internet should not be defined geographically 

or geo-politically. The very word “Internet” belies its intangible nature. The Internet cannot be 

correlated with geography because permanent geographical features that pose physical barriers to 

the movement of people and goods are neutralized by the Internet’s multiple technological 

pathways. Examples of this are the submarine fiber optic cables that crisscross under oceans and 

rivers, the fiber optic cables that pass through mountain passes and mountain tunnels, and the 

communications satellites that fly over these physical obstructions altogether. Nor can the 

Internet be defined geo-politically. As recent developments have shown, geopolitical boundaries 

are porous to the movement of people and are even more porous to streams of data packets. 
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Authoritarian governments have become increasingly aware of this phenomenon as they have 

sought to “turn off” the diverse pathways of ideas and information. 

2.3.2 The Internet Edge Should Not Be Defined By Applications 

Some may choose to define the edge of the Internet by examining the applications that touch all 

persons and working to ensure the security of those applications. E-mail, the World Wide Web, 

and the “walled gardens” of an ISP’s closed community all provide areas of focus and interest in 

defining a national perimeter. Applications also exist that are not oriented towards the end user, 

but are machine-to-machine applications. However, while these applications have some 

common elements, they appear to be too generic to provide significant benefit (e.g., both classes 

can run on end-user terminals, some common protocols, or software platforms). Given that 

Americans do not use a standard suite of applications, the “edge” becomes too jagged to use 

applications as a defining factor for the Internet’s edge. 

2.3.3 The Internet Edge Should Not Be Defined By The Terminal 

Another suggested method is to define the edge desktop by desktop. If all Americans were to 

install a base level of security on their computers, conceptually, it would become more 

challenging for that computer to be hacked and used as an attack node against the core network. 

However, defining the edge by end user presents significant security challenges and risks. 

Requiring secure terminals for every home user will automatically increase the cost of ISP 

service. ISPs simply do not have the resources or ability to proactively monitor home users’ 

machines—especially when the purpose of monitoring is to ensure the currency of another 

company’s software products. Liability issues also make this avenue significantly less inviting 

for the ISPs. 

3.0 DEVELOPING KEY WARNINGS AND INDICATORS 

In today’s technology environment, monitoring networks for denial of service (DOS) attacks is 

extremely challenging. Many in the Government are calling for the development of network 

monitoring capabilities that will allow the detection of DOS attacks as they are launched. 

This will, someday, be a possibility; however, without significant advancements in router 

functionality, the processing power needed to examine each and every packet as it travels across 

the Internet will slow the Internet to a crawl or shut it down entirely. 

That does not mean that the Nation is defenseless against cyber-attacks. From any perspective, 

crucial steps exist that must be taken to improve the security of the Internet as a whole. 

Companies and home users alike can implement best practices in their networks or home 

computers and can install and update anti-virus and firewall software to protect their systems 

from hackers and other intruders. 

The Government can and should work with Internet security experts and standards bodies to 

develop a standard set of “key warnings and indicators” that all service providers can use as a 

baseline to measure security threats. Service providers and network operators are in the best 

position to monitor their networks. Although certain service providers can meet and exceed 

those baselines as a matter of customer service, standardized key indicators and warnings will 

provide earlier notice of national security level network events to downstream customers, 
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INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT 5 

upstream providers, and relevant security groups or Government organizations that may then 

react accordingly. 

Several existing organizations are able to develop key warnings and indicators. The Network 

Reliability and Interoperability Council’s (NRIC) Focus Group 2 is involved in studying 

voluntary outage reporting for both Internet network operators and ISPs. The NSTAC Network 

Security Information Exchange (NSIE) is also equipped with the membership and technical 

expertise necessary to initiate publication of warning and indicator guidelines. Additional efforts 

to develop key warnings and indicators are included in the President’s National Strategy for 

Cyberspace Security. These initiatives should be encouraged to combine with those efforts 

currently under way within the National Communications System (now part of the Department 

of Homeland Security) and privately, within organizations such as Dshield.org, Incidents.org, 

and others. 

3.1 Finding the Edge For Red Networks 

Historically, the Federal Government established a “red network” program for the transportation 

and containment of classified information. In essence, the edge of a red network exists at the 

point where the classified or sensitive data leaves the “red” (classified information) side and 

mixes into the “black” (unclassified information) side. These networks attempt to bound the 

traffic by a range of techniques ranging from “air gapping” through protective hardware and 

software elements to establishing laws and policies. Although these boundaries are the most 

easily identifiable, logical places to monitor the integrity of the edge of the red networks, these 

boundaries and protective measures institute a protected edge. Prudently, an operator of a red 

network should monitor traffic both well outside and inside the boundary between the red and 

black networks. The network operator can enhance protection and protect the network by 

blocking sensitive traffic, or reroute it somewhere else to allow the traffic to proceed. Ensuring 

the integrity of red or classified networks is an increasingly complex task as these red networks 

become more complex and intertwined with the rest of the public network. Thus, even in the red 

network program, defining the “edge” of the red network is becoming even more difficult. Even 

though the red network program is a good model to evaluate for protection of key assets within 

the Internet, various factors prevent its application to the entire Internet. 

4.0 CONCLUSIONS 

Defending—not defining—the national edge of the Internet is most important. Yet, defense of 

the Internet is a concept that is almost impossible, given that it implies that the Internet is 

defensible everywhere it touches—across every border around the world. The concept of a 

secure Internet will remain a global work in progress as it addresses a global dynamic problem. 

Neither hard nor soft technologies are currently at the level that allows for a totally secure 

Internet worldwide. Until these technologies become available, the United States Government 

should continue to focus its attention on critical NS/EP missions and functions supporting those 

missions that rely on the Internet and encourage the parties responsible for those missions to 

ensure that they are adequately protected through redundancy and alternate capabilities. 

Industry, standards bodies, software vendors, equipment vendors, network operators, and end 
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6 INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT 

users of all products and services that make up the Internet should ensure that these products 

have built-in baseline security features and that these features are appropriately configured and 

kept up to date. Finally, Government should work with industry to identify key warnings and 

indicators that service providers can use as a baseline to measure security threats and trigger 

notification processes to relevant stakeholders. 

5.0 RECOMMENDATIONS 

The Government should continue its work to identify the critical NS/EP missions and 

functions supporting those missions that rely on the Internet and encourage the parties 

responsible for those missions to ensure that they are adequately protected through 

redundancy and alternate capabilities; 

Industry, standards bodies, software vendors, equipment vendors, network operators and 

end users of all products and services that make up the Internet should ensure that these 

products have built-in baseline security features and that these capabilities are 

appropriately configured and kept up to date; and 

The Government should work with Internet security experts and standards bodies to 

develop a standard set of “key warnings and indicators” that all service providers can use 

as a baseline to measure security threats. 
President’s National Security Telecommunications Advisory Committee 

INTERNET SECURITY/ARCHITECTURE TASK FORCE REPORT A-1 

APPENDIX A—TASK FORCE MEMBERS, OTHER PARTICIPANTS, AND BRIEFERS 

TASK FORCE MEMBERS 

MCI, Inc. Ms. Joan Grewe, Chair 

Raytheon Company Mr. Sebastian Taphanel, Vice-Chair 

AT&T Corporation Mr. Harry Underhill 

Bank of America Corporation Mr. Roger Callahan 

BellSouth Corporation Mr. Shawn Cochran 

The Boeing Company Mr. Robert Steele 

Cisco Systems Mr. James Massa 

Computer Sciences Corporation Mr. Guy Copeland 

Lockheed Martin Corporation Mr. Daniel Tolley 

Lucent Technologies Mr. David Massarik 

Nortel Networks Dr. Jack Edwards 

Northrop Grumman Corporation Mr. Scott Freber 

Science Applications International Corporation Mr. Hank Kluepfel 

SBC Communications, Inc. Ms. Rosemary Leffler 

VeriSign, Inc. Mr. Ken Silva 

Verizon Communications, Inc. Mr. James Bean 

OTHER PARTICIPANTS

Cisco Systems, Inc. Mr. Brian O’Connor 

George Washington University Dr. Jack Oslund 

Juniper Networks, Inc. Mr. Pejhan Peymani 

Microsoft Corporation Mr. Sean Finnegan 

National Security Council Mr. Marcus Sachs 

Raytheon Company Mr. James Craft 

SBC Communications, Inc. Mr. Paul Hart 

VeriSign, Inc. Mr. Michael Aisenberg 

MCI, Inc. Ms. Cristin Flynn 

BRIEFERS 

CanSecWest Mr. Dragos Ruiu 

Equinix, Inc. Mr. Jay Adelson 

The Honeynet Project Mr. Shane Macaulay 

National Security Council Ms. Marjorie Gilbert 

Sun Microsystems, Inc. Mr. Lance Spitzner 

University of Washington Mr. David Dittrich