A-B

Adaptability

A user requirement for the system to be able to adapt to users' changing needs.

Address

For IP, a 32-bit number that identifies a device at the network layer.

Addressing

Applying identifiers (addresses) to devices at various protocol layers (e.g., data-link and network).

Address mask

For IP, a 32-bit number that identifies which bits in the address are considered part of the network and (by default) which bits are considered part of the device.

Address prefix

When an address mask is noted by its length (N) in bits, as /N.

Addressing

Assigning local or global, private or public, temporary or persistent identifiers to devices.

Affordability

A user requirement for what users or management can afford to purchase for the network.

Alarm

A network management event that triggers a real-time notification to network personnel.

See also Event.

Application requirements

Requirements that are determined from application information, experience, or testing and are what are needed by applications to successfully operate on the system.

Architectural components

These are functional areas of the network, whose relationships define the network architecture. Examples of architectural components include IP services, security and privacy, network management, and addressing and routing.

Areas

Segments of a network design that are the result of sizing the network.

Asynchronous applications

Applications that are relatively insensitive to time, either assuming no timing relationship between source and destination or that the timing relationship is outside the bounds of the applications session.

Audit trail

The set of documents, data, and decisions for the architecture and design.

Autonomous system (AS)

A collection of networks that are under the same management control.

Availability

The relationship between the frequency of mission-critical failures and the time to restore service. This is also known as operational availability.

Bandwidth

The theoretical capacity of one or more network elements in the system.

Bandwidth*delay product

An estimate of the maximum amount of information that may be in transit across a particular technology at any given time.

Best-effort service

Network service in which there is no control over how the network will satisfy the service request and there are no guarantees associated with this service. Service will be both unpredictable and unreliable, with variable performance across a range of values (from the network being unavailable [0 performance] to the lowest common denominator of performance across all of the technologies in the end-to-end path).

BGPv4

A path-vector-based External Gateway Protocol.

Blocking

When computing devices halt their computations, waiting for information from other computing devices.

Broadcast domain

A group of network-addressable devices where all of the devices in that group can be reached by a single network address, the broadcast address.

Broadcast technologies

Network technologies that support the ability of a device to communicate simultaneously with all other devices on their network or subnet, through using a well-known broadcast address specific to the network technology.