2.2.5.4 QosProbe Upper-Level Header Format
A controller sends a QosProbe frame to a sink and by a sink back to a controller. It carries time stamp values that an application can use on the controller to calculate network bandwidth.
The QosProbe header that follows the Base header MUST have the following format.
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Controller_Transmit_Timestamp |
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Sink_Receive_Timestamp |
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Sink_Transmit_Timestamp |
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Test_Type |
Packet ID |
T |
802.1p Value |
Payload |
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Controller_Transmit_Timestamp (8 bytes): This field specifies the time stamp, in network byte order, of the controller on transmission, in units per Performance Counter Frequency (as specified in section 2.2.1.1.11).
Sink_Receive_Timestamp (8 bytes): This field specifies the time stamp, in network byte order, of the sink on receipt in units per Performance Counter Frequency (as specified in section 2.2.1.1.11). This field MUST be set to zero in a timed probe test. In a probegap test, this field MUST be set to zero on transmission from the controller.
Sink_Transmit_Timestamp (8 bytes): This field specifies the time stamp, in network byte order, of the sink on transmission in units per Performance Counter Frequency (as specified in section 2.2.1.1.11). This field MUST be set to zero in a timed probe test. In a probegap test, this field MUST be set to zero on transmission from the controller.
Test_Type (1 byte): This field specifies the test type in which this packet is involved. The following table shows the possible values.
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Value
Meaning
0x00
Timed probe.
0x01
probegap originating from the controller.
0x02
probegap originating from the sink.
Packet ID (1 byte): The controller MUST assign an ID to the packet so it can be uniquely identified when it is returned in either a QoSProbe or QosQueryResp.
T (1 bit): This bit indicates whether or not the encapsulating Ethernet frame for the QueryProbe frame returned by a sink contains a tag header as specified in [IEEE802.1Q] section 9. The Tag Control Information portion of the tag header is set to all zeros except the user_priority field, whose value is set from the 802.1p value. This value is only valid for probegap tests (Test_Type = 0x01), and otherwise MUST be set to zero when sent and ignored on receipt.
802.1p Value (7 bits): If the T flag is set, this field contains the value to be set as the user_priority field of the Tag Contol Information portion of the tag header as specified in [IEEE802.1Q] section 9 for each QosProbe packet that is reflected to the controller in the case of a probegap test. If the T flag is not set, this field MUST be set to zero when sent and MUST be ignored on receipt.
Payload (5 bytes): This field specifies arbitrary data that is used to pad the frame to the correct frame size. In a probegap experiment, the payload content that a sink receives MUST be duplicated on the sink's send path.