Wavetek ANT-20, Operating Manual

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Broadband Analyzer/Generator ANT-20/ANT-20E
TB-8 Technical Background
Fig. TB-5 “Test Setup” dialog for SVC connections with Multiplexer section (a)
1.5 Traffic Shaper
If the “Shape to Contract” option is activated, the instrument shapes the set traffic profile.
Shaping occurs whenever the traffic contract would otherwise be violated. This means that
conformance to the traffic contract is guaranteed when the option is activated.
With traffic shaping, cells that would otherwise violate the traffic contract, e.g. by exceeding the
permitted CDVT or burst tolerance, are pushed back on the time axis until they can be
transmitted without violating the traffic contract. The cells are always transmitted at the earliest
possible moment.
If traffic shaping takes place, it is basically unavoidable that the traffic profile is altered by the
shaper. The shaper algorithm used is designed to keep changes to the traffic profile as small as
possible.
Activation of the traffic shaper may cause cells to be dropped if the traffic contract cannot be met
in any other way.
a
Type of traffic contract Traffic shaper used
CBR Compatible with “Single Leaky Bucket”
DBR Compatible with “Single Leaky Bucket”
VBR Compatible with “Dual Leaky Bucket”
SBR Compatible with “Dual Leaky Bucket”
UBR Compatible with “Single Leaky Bucket”
Table TB-3 Verkehrstypen und zugeordnete “Traffic Shaper”