Spirent SmartBits System, Reference Manual

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Chapter 2: System Architecture
Traffic Generation and Performance Analysis
SmartBits System Reference 23
SmartMetrics Cards and Traffic
The SmartMetrics processors are located on each card instead of on the chassis controller.
They offer Traditional mode as well as SmartMetrics mode performance analysis.
For a summary of SmartMetrics card features, please refer to Table 2-5 on page 25 . For
details on individual cards, please refer to Chapter 9, “Ethernet Cards” .
The SmartMetrics mode offers extensive sequence and latency tracking, histograms, and
analysis for every frame via a time-stamped signature field inserted into each transmitted
SmartMetrics frame; this capability is also offered on TeraMetrics cards.
SmartMetrics Frame Blueprints
Hundreds of IP streams (frame blueprints), per port, feed into a sequenced, time-stamped
individually tracked series of frames (see
Figure 2-7 ).
Within each stream, there can be thousands of “SmartFlows” per port. Each SmartFlow
within a stream carries the same protocol format but offers a number of variables which
are individually time-stamped and tracked according to the test configuration.
Figure 2-7. SmartMetrics Frame Blueprints
SmartMetrics Signature Field
SmartMetrics mode, streams, and measurements support the use of an embedded Signature
field specific to each frame. The Signature field is used by the receiving card to analyze
network traffic and to display the results in spreadsheets and/or histograms.
The SmartMetrics Signature field resides in the last 18 bytes of the payload of each frame
and contains the following:
•
Stream ID based on stream number, chassis, card slot, and port #.
•
Frame sequence number.
•
Transmit timestamp.
Important: If enabled, the Signature field overwrites the last 18 bytes of data at the end
of payload of each frame, therefore, do not insert significant data into that area.