Traffic Engineering Terminology

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Common Traffic Engineering Terms

(from IETF RFC 3272bis)

Baseline analysis: A study conducted to serve as a baseline for comparison to the actual behavior of the network.

Busy hour: A one hour period within a specified interval of time (typically 24 hours) in which the traffic load in a network or sub-network is greatest.

Bottleneck: A network element whose input traffic rate tends to be greater than its output rate.

Congestion: A state of a network resource in which the traffic incident on the resource exceeds its output capacity over an interval of time.

Congestion avoidance: An approach to congestion management that attempts to obviate the occurrence of congestion.

Congestion control: An approach to congestion management that attempts to remedy congestion problems that have already occurred.

Constraint based routing: A class of routing protocols that take specified traffic attributes, network constraints, and policy constraints into account when making routing decisions. Constraint-based routing is applicable to traffic aggregates as well as flows. It is a generalization of QoS routing.

Demand side congestion management: A congestion management scheme that addresses congestion problems by regulating or conditioning offered load.

Effective bandwidth: The minimum amount of bandwidth that can be assigned to a flow or traffic aggregate in order to deliver ‘acceptable service quality’ to the flow or traffic aggregate.

Egress traffic: Traffic exiting a network or network element. Hot-spot: A network element or subsystem which is in a state of congestion.

Ingress traffic: Traffic entering a network or network element. Inter-domain traffic: Traffic that originates in one Autonomous system and terminates in another.

Loss network: A network that does not provide adequate buffering for traffic, so that traffic entering a busy resource within the network will be dropped rather than queued.

Metric: A parameter defined in terms of standard units of measurement.

Measurement methodology: A repeatable measurement technique used to derive one or more metrics of interest.

Network survivability: The capability to provide a prescribed level of QoS for existing services after a given number of failures occur within the network.

Offline traffic engineering: A traffic engineering system that exists outside of the network.

Online traffic engineering: A traffic engineering system that exists within the network, typically implemented on or as adjuncts to operational network elements.

Performance measures: Metrics that provide quantitative or qualitative measures of the performance of systems or subsystems of interest.

Performance management: A systematic approach to improving effectiveness in the accomplishment of specific networking goals related to performance improvement.

Performance metric: A performance parameter defined in terms of standard units of measurement.

Provisioning: The process of assigning or configuring network resources to meet certain requests.

QoS routing: Class of routing systems that selects paths to be used by a flow based on the QoS requirements of the flow.

Service Level Agreement (SLA): A contract between a provider and a customer that guarantees specific levels of performance and reliability at a certain cost.

Service Level Objective (SLO): A key element of an SLA between a provider and a customer. SLOs are agreed upon as a means of measuring the performance of the Service Provider and are outlined as a way of avoiding disputes between the two parties based on misunderstanding.

Stability: An operational state in which a network does not oscillate in a disruptive manner from one mode to another mode. Supply-side congestion management: A congestion management scheme that provisions additional network resources to address existing and/or anticipated congestion problems.

Transit traffic: Traffic whose origin and destination are both outside of the network under consideration.

Traffic characteristic: A description of the temporal behavior or a description of the attributes of a given traffic flow or traffic aggregate.

Traffic engineering system: A collection of objects, mechanisms, and protocols that are used conjunctively to accomplish traffic engineering objectives.

Traffic flow: A stream of packets between two end-points that can be characterized in a certain way. A micro-flow has a more specific definition A micro-flow is a stream of packets with the same source and destination addresses, source and destination ports, and protocol ID.

Traffic intensity: A measure of traffic loading with respect to a resource capacity over a specified period of time. In classical telephony systems, traffic intensity is measured in units of Erlangs.

Traffic matrix: A representation of the traffic demand between a set
of origin and destination abstract nodes. An abstract node can
consist of one or more network elements.

Traffic monitoring: The process of observing traffic characteristics at a given point in a network and collecting the traffic information for analysis and further action.

Traffic trunk: An aggregation of traffic flows belonging to the same class which are forwarded through a common path. A traffic trunk may be characterized by an ingress and egress node, and a set of attributes which determine its behavioral characteristics and requirements from the network.

Source: IETF RFC 3272bis