Growing Vulnerability of the Public Switched Networks Implications for National Security Emergency Preparedness (1989) / Chapter Skim
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5 Technology
5 Technology
Pages 46-66
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From page 46... ...
Optical fiber is becoming the transmission medium of choice; digital switching is becoming the dominant switching technique; and software-based processing, linked to very large scale integrated (VESI) circuitry, is becoming the preferred technology for network management and control.
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From page 47... ...
The sections that follow present a more detailed picture of how transmission, switching, integrated circuit technology, and network technologies are being deployed in the public networks and will briefly assess the implications of each of these technological trends for NSEP. TRANSMISSION Optical Fiber Background As copper-based systems become obsolete, the media that will provide transmission in the public networks will be optical fiber, satellite radio, and terrestrial radio.
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From page 48... ...
By 1995, fiber will be the most common mode of transmission in network interoffice bunking systems (that is, the long distance portion of the public switched networks)
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From page 49... ...
The increased dependence of the public networks on power supplied by electric utility adds a new source of network vulnerability: electric power outages (Samuelson, 1988~. Satellite Radio Background The principal alternative transmission medium for long distance service has been satellite radio.
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From page 50... ...
Cellular mobile radio systems divide service areas into "cells," which have low-power microwave antennas at their center, with each antenna linked terrestrially to a centralized switching center (mobile telephone switching office, or MTSO) , which, in turn, is interconnected with the landline telephone network.
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From page 51... ...
SWITCHING BaLkground Switching technology is marked by two divergent trends: advances in microprocessing technology are driving switching capabilities toward the customer's premises; but the econorn~cs of digital switching is driving telephone companies to build large-hub switching centers with huge capacities. The technologies that are providing the impetus for these trends are very-high-performance integrated circuits and highly sophisticated distributed processing technologies.
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From page 52... ...
Distributed nodes serve as routing points for network control, linking the central node with remote databases. Central nodes perform specified functions for the distributed nodes, thus permitting economical deployment of the remote nodes.
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From page 53... ...
INTEGRATED CIRCUIT TECHNOLOGY Backgrolmd Very large scale integration continues to stretch the imagination. The realization of 1-million-bit chips today has brought memory costs to the point where software developers consider memory to be free.
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From page 54... ...
Not only will the merging of analog signal processing and digital signal processing continue but, at the system level, the advanced microprocessors will allow switching and transmission to merge as well. By the year 2000, the trend of today to bring switching and transmission multiplexors together will only weld the switching multiplexer into a practically indistinguishable system element within a fiber network.
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From page 55... ...
As indicated above, large switches have software programs of up to 10 million lines of code, and massive databases used for network control result in concentration of network software assets. Further, the Federal Communications Comrn~ssion has mandated that the Regional Bell Operating Companies provide Open Network Architecture (ONA)
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From page 56... ...
Cornrnon channel signaling will change that: All signaling takes place over separate data links, which connect the switching systems of the network. In a typical application, the calling party signals his or her central office by using multifrequency touch tone.
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From page 57... ...
Another source of software vulnerability arises from a concept called the "intelligent network." These networks employ the packet signaling networks to provide access to remote databases used for offering such services as the national 800 number. Some of the intelligence that would normally reside in a local switching office is now removed and concentrated at a distant point reached by the packet-switched network.
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From page 58... ...
, all develop voluntary standards for data communications. Two major trends affecting the entire telecommunications industry can be expected to have a major impact on the traditional role of standards in the evolution and operation for the public networks and for the private networks that may be used in an emergency to bridge breaks in the public network.
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From page 59... ...
The deterioration of network interoperability resulting from standards degradation is, additionally, a matter of serious concern from a NSEP standpoint. NETWORK SYNCHRONIZATION Background With an increasing number of carriers deploying digital networks, the public network configuration is evolving toward a set of separate islands, each having their own means for accessing and distributing a primary frequency reference.
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From page 60... ...
No significant synchronization timing issues for national security emergency preparedness appear to exist, because timing is set by the connected surviving access tandem. A SUMMARY OF PUBLIC SWITCHED NETWOlill VU[NERABIIITY TRENDS Among the technology trends that are increasing network vuInerability are the development and perfection of fiber optic technology, the advances in digital switching, and the reliance on software for network control.
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From page 61... ...
. The evolution of switching technology is resulting in fewer switches, a concentration of control, and thus greater vuinerability of the public switched networks.
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From page 62... ...
The competitive environment will provide backup for some threats, but not for correlated events in which damage is inJ7icted at several points by an intelligent adversary or by a widespread natural disaster. This vulnerability to correlated events is a natural product of common channel signaling (CCS)
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From page 63... ...
., RECOMMENDATIONS Based on the foregoing discussion and analysis the committee makes the following recommendations. Recommendation: Use More Terknology Diversity Because public network evolution is increasingly being driven by economic considerations, the National Communications System should am the National Security Telecommunications Advisory Committee to examine how national security emergency preparedness needs can be met; the National Security Telecommunications Advisory Committee should recommend steps to make critical network nodes more secure, reduce concentration of network traffic, and increase alternate route diversity.
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From page 64... ...
Recommendation: Increase Radio Access Capabilities Since radio technologies can provide a valuable source of alternative routing in emergencies, the National Communications System should consider how terrestrial and satellite radio transmission can be employed to provide route di~rersity for national security emergency prepare(lness purposes; in particular, consideration should be given as to how very small aperture tenninals can be used to back up the public switched networks. Advances in radio technology offer great promise for augmenting network route diversity.
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From page 65... ...
However, because users have full freedom to connect registered terminal devices to the public networks, it is incumbent upon equipment designers to provide units that function properly within existing network synchronization standards. REFERENCES Buckley, W
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From page 66... ...
Presentation to the Committee on Review of Switching, Synchronization and Network Control in National Security Telecommunications, Washington, D.C., March 15.
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