Asynchronous Transfer Mode – ATM
Acterna ANT-5 Page 103
Three bits are available for the Payload Type Identifier. The PTI identifies cells
belonging to different types of flow and indicates impending congestion in the network.
See section 6.12.1, PTI coding for reference.
Cell Loss Priority CLP allows cells to be classified as high priority CLP-0 or low priority
CLP-1. In the event of congestion, cells that are set to CLP-1 will be discarded first.
Click on OK when you have set the parameters.
6.4.3 ATM Service Contract Attributes Tx
Sets the parameters for the Service Contract. A
Constant Bit Rate CBR or a Variable Bit Rate
VBR can be selected as the Profile Type. In this
example a CBR has been selected.
A CBR is a class of service that guarantees the
transmission at a constant bit rate, thus
emulating a dedicated transmission link.
In this example a Peak Cell Rate PCR of 25 cells
per second will be sent.
Note: Cells sent at a rate close to 100% of the maximum cell rate will be rounded-up.
In this example a VBR has been selected as the
Profile Type. The user can define the PCR and
the Sustainable Cell Rate SRC. In this example a
repeated pattern of 100 PCR cells will be sent
during T1, where T1 in this example = 1 second.
This will be followed by 50 SCR cells during T2,
where T2 = 1 second (100x10ms)
6.5 Configuring the Adaptation Layer
6.5.1 ATM SDU Setup Tx
Sets the Service Data Units SDU for the device
under test. In this example the Payload Type
has been set to 0.191.
O.191 describes a diagnostic model for
performance analysis in which test cells are
transported over an agreed virtual connection.
The O.191 measurement tests performance on
a cell-by-cell basis in the ATM layer.
The function and performance of other payload types must be considered separately.
For example, the payload type for Channel B will be fixed.
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