Spirent SmartBits System, Reference Manual

Page: 136 / 278

Chapter 9: Ethernet Cards
Standard Ethernet Features
128 SmartBits System Reference
Frame Arrival Time Variation
This is the period of time between the first bit of an arriving packet and the first bit of the
next arriving packet. This time includes the media access, preamble, interpacket gap, and
packet transmission time. The following measurements are made per stream: port #, VTE
(stream) #, total frames, frames arriving within each of 16 user-definable time intervals.
Speed
Wire rate(s) of the card.
Traffic Rates
Wire rates of each port.
Triggers and Errored Frames
A trigger is a pattern tracking tool that identifies any packet with a specific pattern located
inside any of the packets received by a receiving SmartBits card. The receiving card then
counts the number of triggers received with the specific pattern.
In SmartWindow, SmartLib, and some applications, two 6-byte triggers can be specified
using the bit offset or using a pattern and mask. The trigger counter can be set to: Trigger
1,Trigger 2; Trigger 1 or Trigger 2; Trigger 1 and Trigger 2.
In Ethernet, WAN and POS cards, the transmit trigger pattern is added to the frame
content through VFDs (Variable Field Definitions) or automatically in streams. Triggers
are used in two ways:
•
Ethernet/WAN/POS cards. Increment the trigger counter if the desired pattern is in
the packet, regardless of whether the packet is valid or not. The packet is labeled as
Mode E counters (errored triggers counted) in Figure 9-3 on page 129 .
•
To maximize processing power for hundreds of streams, the following SmartMetrics
cards do not increment the trigger counter if the packet is invalid, even if the pattern is
in the packet. In
Figure 9-3 on page 129 , this is labeled Mode N (errored trigger
frames NOT counted) cards:
– ML-5710.
– ML-7710.
– ML-7711.
– LAN-3101A.
Figure 9-4 on page 129 describes how triggers and errored traffic are displayed in
counters available in SmartBits applications.