Click one of the letters above to advance the page to terms beginning with that letter.


Advisory Message

Any message generated by the operating system that informs the operator about a system error, an unprivileged entry, or the status of an event.

ATM Switched

A synchronous transfer mode switched service - high speed packet (cell) switching using fixed cell size for all media (voice, video, and data).


To establish the validity of a claimed identity. 


An entity recognized by some set of secure systems as a trusted source of security information.


A measure of equipment, system, or network performance, usually expressed in percent; the ratio of operating time to the sum of operating time plus down- time. 


The Acquisition Working Group is a working group established by the Interagency Management Council to recommend acquisition policy and strategy in the Post-FTS2000 environment. 



A quantified description of the information-carrying capacity of a communications path or link. It can apply to telephone or network wiring as well as system buses, radio frequency signals, and monitors. Bandwidth is measured in (1) cycles per second, or hertz (Hz), which is the difference between the lowest and highest frequencies transmitted or (2) in terms of data bits or data bytes per second. 

Basic E-mail

Electronic mail service aimed at providing the most basic end-to-end capabilities commercially available.

Briefing Message

A message containing operational information and prepared in the format(s) prescribed in document number 532-SIP-NCC/STDN. This document may be found on-line in a Portable Data File format (PDF) by doing a document number search at the following URL: http://tip.gsfc.nasa. gov/webpgs/query-topic.htm. 

Bulletin Board

Electronic storage and retrieval systems serving as a bulletin board from which government and the public can post and disseminate questions, responses, and general information.  




Class C2, Controlled Access Protection, is described in DoD 5200.28-STD, Department of Defense Trusted Computer System Evaluation Criteria. Systems in this class make users individually accountable for their actions through login procedures, auditing of security-relevant events, and resource isolation. More information may be obtained on-line by visiting the web site at URL soft/ ds5200.281.html and scrolling down to paragraph 2.2.  


Certificate Security

Data sealed by an Authority. The certificate contains the security data and the seal.


The cost of providing NISN services to a customer is billed to and debited from the customer's budget.


A voice or data oriented switched service arrangement that initiates a switched connection on a message or voice call basis. 

Closed Network

There is neither access to nor from The Internet. Communications are limited to a defined set of authorized addresses.


Customers are those organizational entities which validate a network requirement and either directly funds or arranges funding for the requirement. Examples of customers are officials in NASA Enterprises, Program Offices, the Associate Administrator for Headquarters Operations, and the Directors of NASA Centers and Field Installations. 

Customer Located Equipment

To provide NISN services to a user, the service provider often must install equipment on the premises of the user. Though this equipment belongs to the service provider, the user may be authorized to perform limited "operator maintenance" functions to facilitate service restoral. 


Dedicated Services

Services in which communications resources are permanently assigned to one user.


Electronic Commerce

A combination of electronic data interchange and electronic funds transfer services aimed at enhancing commerce and business exchanges between organizations. 

Enhanced E-mail

Electronic mail service which has functionality beyond that provided under a basic E-mail offering (e.g., supports electronic commerce requirements, signature authentication, direct facsimile transfer, groupware support, security features). 



The process of discarding packets that do not meet the network's criteria for forwarding.  



A firewall is either the program or the computer it runs on, usually an Internet gateway server, that protects the resources of one network from users from other networks. Typically, an enterprise with an intranet that allows its workers access to the wider Internet will want a firewall to prevent outsiders from accessing its own private data resources. There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain names and IP addresses. Another is to not allow Telnet access into your network (although you may permit your own users to request Telnet connections outside your network). 

Frame Relay

A packet service arrangement in which digital information is switched directly across networks with minimal error control or intermediate switching (as in packet switched arrangements) to minimize delay.  


Full Cost Accounting

The process of collecting cost information from each element of a provided service and producing a total cost over a period of time for providing that service. Cost elements include civil service labor, facilities, utilities, engineering, installation, operation and maintenance, circuit lease, equipment, etc.  




The Interagency Management Council consists of senior government information resources management officials from agencies using FTS2000, and provides oversight to General Services Administration in administering telecommunications contracts. 

Interface Control Document

A document prepared between two or more parties which defines the interfaces between the users of the services and between the user of the service and the service itself. These documents delineate responsibility for each interface and include physical and electronic attributes of each interface as well as the protocols to be used. 


Internet Protocol version 6 is a version of the Internet Protocol (IP) intended to succeed IPv4, which is the protocol currently used to direct almost all Internet traffic.


Integrated Services Digital Network services operating in the narrowband data transmission range (e.g., 64 kilobits per second information channels). 


LAN Interconnection

 A service in which local area networks can be directly interconnected over long haul communications services at their primary data rates (e.g., the interconnection of Ethernet local area networks at 10 megabits per second). 


The time it takes for a data packet to move across a network connection. 


Mission Services Manager

The SOMO liaison person who coordinates the mission operations functions for a program or center and provides the mission operations communications requirements to the NISN Center Representative  


Multimedia Oriented

Services that provide full motion video, data, and switched voice concurrent operation among users.



The National Information Infrastructure is envisioned to be an advanced, digital network that will allow individuals, businesses, government service providers, academia, and others to send, receive, and share information, whether audio, data, video, text, imagery, or multimedia, at reasonable cost. It is anticipated that the National Information Infrastructure will largely be financed, built, and operated by the private sector. 

NISN Center/Program Representative

The liaison person who coordinates customer functions for a program or center with the NISN project.

Number Services

An assignment of specific services to a dialed number (e.g., 700-, 800-, 900-) used to support bill consolidation, emergency operations contact, or special information access arrangements by the general public.  



Open Network

Access to and from The Internet is permitted.


PCS Applications Personal Communications Service

The provision of reliable, ubiquitous communications to individuals who use portable, low-power terminals. 


Restricted Network

Access to The Internet is permitted but access from The Internet is strictly controlled.


Scheduling Message

An operational message that requests specific assets of the Space Network ground segment be scheduled for a specific support at a particular date and time. 

Security Services

The offering of special interface devices, equipment, or transmission facilities that supports secure telecommunications operations between users. 


Switched Multi-megabit Data Service is a broadband packet switched service offering.


Synchronous Optical Network Transmission service is the transmission of byte interleaved multiplexed data synchronously over a fiber optic media at data rates that are multiples of 51.84 megabits per second. 

Special Staff

Employees with expert skills in a narrowly defined area, e.g., information technology security. Employees assigned to special staff functions are made available on an as-needed basis, performing duties in support of other organizations when not engaged by NISN. 


Services in which communications resources are shared among many users through the use of a switching device.  




(Also known as Trojan Horse) A program that does something undocumented that the programmer intended, but that some users would not approve of if they knew about it. Some consider that a virus is a particular case of a Trojan Horse, namely one which is able to spread to other programs (i.e., it turns them into Trojans too). Others consider that a virus which does not do any deliberate damage (other than merely replicating) is not a Trojan. Finally, many use the term "Trojan" to refer only to "non-replicating" malware, in which instance the set of Trojans and the set of viruses are disjoint. 


A trusted computer system is one that employs sufficient hardware and software integrity measures to allow its use for processing simultaneously a range of sensitive (or classified) information.  



Value Added

Services that provide functions above and beyond those necessary for the transport of information.


A computer virus is defined by Symantec as being a parasitic program written intentionally to enter a computer without the user's permission or knowledge. The word parasite is used because a virus attaches to files or boot sectors and replicates itself, thus continuing to spread. Though some viruses do little but replicate, others can cause serious damage or affect program and system performance. A virus should never be assumed harmless and left on a system.  



Voice over IP commonly refers to the communication protocols, technologies, methodologies, and transmission techniques involved in the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, and broadband phone.


A Virtual Private Network is a secure network that uses primarily public telecommunication infrastructures, such as the Internet, to provide remote offices or traveling users an access to a central organizational network.



Wide Area Network is a telecommunication network that covers a broad area (i.e., any network that links across metropolitan, regional, or national boundaries). Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence this mode of telecommunication allows a business to effectively carry out its daily function regardless of location.

Wireless Voice/Data

A general term for radio communications such as cellular, satellite, microwave, and other services aimed at increasing the mobility and spatial coverage of telecommunications offerings beyond those reachable via wire-line arrangements. 


A computer worm is a self-contained program (or set of programs), that is able to spread functional copies of itself or its segments to other computer systems (usually via network connections).