D-E

Data flows

See Flows.

Data sink

A device that collects or terminates data on a network.

Data source

A device that produces data on a network.

De facto standard

A standard that is generally accepted through being widely implemented and used.

Default route

The route used when there is no other route for that destination. It is the route of last resort.

Default route propagation

The technique used to inform the network (or subnets or functional areas) of the default route.

Delay

A measure of the time difference in the transmission of information across the system.

Differentiated services

A quality-of-service mechanism that defines a set of values (termed differentiated services code points [DSCPs]) for classes of traffic flows to be used by resource control mechanisms.

Directionality

The preference of a flow to have more requirements in one direction than in another.

Distributed-computing architectural model

An architectural model that follows the distributed-computing flow model and in which the data sources and sinks are obvious locations for architectural features.

Distributed-computing flow model

A flow model that either has the inverse of the characteristics of the client-server flow model or is a hybrid of peer-to-peer and client-server flow models.

Distributed management

When there are multiple separate components to the management system and these components are strategically placed across the network, localizing network management traffic and distributing management domains.

Downstream

Traffic flowing in the direction from the source to the destination.

Dropping

In traffic conditioning, discarding nonconforming traffic.

Encryption

A security mechanism in which cipher algorithms are applied together with a secret key to encrypt data so that they are unreadable if intercepted.

End-to-end architectural model

Architectural model that focuses on all components in the end-to-end path of a traffic flow.

End-to-end (network element) characteristics

Characteristics that can be measured across multiple network elements in the path of one or more traffic flows and may extend across the entire network or between devices.

Environment-specific thresholds

Performance thresholds that are determined for the environment of the current network project on which you are working.

Event

Something that occurs in the network that is worthy of noting, whether informational, as a problem, or as an alarm.

Exterior Gateway Protocols

Routing protocols that communicate routing information (reachability and metrics) primarily between ASs.

External interfaces

The network interfaces between your network and other, outside (external) networks.