Spirent SmartBits System, Reference Manual

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Chapter 13: Token Ring Cards
Token Ring Operational Detail
180 SmartBits System Reference
Burst Modes
The TR Smartcard supports the Burst and Multiburst modes found on other cards. Users
can specify
Burst Count , Interburst Gap and Number of Frames per Burst parameters.
This translates to four modes of operation:
•
Continuous.
•
A Single Burst of frames.
•
Continuous Bursts of frames with each burst separated by an interburst gap.
•
A fixed number of Bursts of frames with each burst separated by an interburst gap .
The interburst gap can be smaller or larger than the interframe gap.
Users should bear in mind the following:
• The Frames per Token value with its associated inter-frame gap overrides the standard
interframe gap but not the interburst gap.
• The minimum gap time for multiburst modes where the burst count is long (typically
greater than 500 frames) will be restricted to 16 bit clocks, that is 2
µ
Sec on a
16MBits/sec ring.
Ring Statistics
The TR Smartcard collects all counts and computes all rate statistics itself, using the
controller merely as a conduit to get the data back to the user.
There are two sources of counts on the TR Smartcard - information derived from the
descriptors and information derived from MAC REM frames received from other stations
on the ring.
All counts are automatically computed as a rate because counts are accumulated on a
second by second basis before being added to the count totals. Not all of these rate counts
are meaningful to the user so only a subset of the rates are displayed.