User Manual

Enterasys X-Pedition User Reference Manual 471
Flow Accounting
be met with reasonable technical effort. NetFlow applications are not limited to the
implementations described here.
Since requirement details and weighting differ for specific implementations, NetFlow derives this
information from the general functionality of the application. Furthermore, the application itself
should lead to a better understanding of the requirements—particularly when designing or
implementing a traffic flow measuring device.
Usage Accounting
NetFlow data provides fine-grained metering for highly flexible, detailed resource utilization
accounting (e.g., flow data includes IP addresses, packet and byte counts, timestamps, type-of-
service, and application ports). Service providers can utilize this information to migrate away from
single-fee or flat-rate billing to more flexible charging mechanisms based on time of day,
bandwidth usage, application usage, quality of service, or volume. Enterprise customers may use
the information to establish a departmental charge-back or cost allocation for resource utilization.
Traffic Profiling
Traffic profiling is the process of characterizing IP flows and flow aggregates through a model used
to represent key flow parameters (e.g., flow duration and volume). It is a prerequisite to network
planning and dimensioning, trend analysis, developing business models, and other activities.
Traffic profiling relies heavily on the particular traffic profiling objective(s)—what statistics and
level of accuracy are required from the measurements. Typical information needed for traffic
profiling includes the distribution of used network services and protocols, the amount of specific
packet types, and flow profiles. Since objectives for traffic profiling vary, this application requires a
highly flexible measurement infrastructure—especially with regard to the options for measurement
configuration and packet classification. NetFlow provides this infrastructure.
Traffic Engineering
NetFlow enables network managers to gain a detailed, time-based view of application usage over
the network. NetFlow data provides key information necessary to optimize strategic network
planning and tactical network engineering decisions—whom to peer with, backbone upgrade
planning, and routing policy planning. With this data, content and service providers can plan and
allocate network and application resources (e.g., Web server sizing and location) to responsively
meet customer demands. This will minimize the total cost of network operations and maximize
network performance, capacity, and reliability.
Traffic Engineering (TE) is composed of methods for measurement, modeling, characterization,
and network control. The goal of TE is to optimize network resource utilization and traffic
performance [RFC2702]. Since control and administrative reaction to measurement results requires
access to the involved network nodes, TE mechanisms and the required measurement function are
usually performed within one administrative domain. Typical parameters required for TE are link
utilization, load between specific network nodes, number, size and entry/exit points of the active
flows, and routing information.