Test Payload

Each Xena test packet contains a special proprietary data area called the Test Payload Data (TPLD), which contains various information about the packet and is identified by a Test Payload ID (TID). The TPLD is located just before the Ethernet FCS and consists of the following sections:

Table 3.1 Default TPLD (20 or 22 bytes)
Field	Length	Explanation
Payload Integrity Checksum (optional)	2 bytes	See the note.
Sequence Number	3 bytes	Packet sequence number used for loss and misordering detection.
Timestamp	4 bytes	Timestamp value used for latency measurements.
Test Payload ID (TID)	2 bytes	Test payload identifier used to identify the sending stream.
Payload Integrity Offset	1 byte	Offset in packet from where to calculate payload integrity.
First Packet Flag	1 bit	Set if this is the first packet after traffic is started.
Checksum Enabled	1 bit	Set if payload integrity checksum is used.
<reserved>	7 bits
Payload Integrity Offset (MSB)	3 bits	Offset in packet from where to calculate payload integrity, MSB (bits 10:9:8)
Timestamp Decimals	4 bits	Additional decimals for the timestamp.
Checksum	8 bytes	TPLD integrity checksum (CRC-32)
Total TPLD Size	20 or 22 bytes

Note

If the ../profile/ (Payload Checksum Offset) is enabled on the parent port (value > 0) , then an additional 2-byte checksum field is inserted in the beginning of the TPLD, just before the Sequence Number. This increases the total size of the TPLD to 22 bytes.

Table 3.2 Micro-TPLD (6 bytes)
Field	Length	Explanation
First Packet Flag	1 bit	Packet sequence number used for loss and misordering detection.
<reserved>	1 bit
Test Payload ID (TID)	10 bits	Test payload identifier used to identify the sending stream.
Timestamp	28 bits	Timestamp value used for latency measurements.
Checksum	8 bits	TPLD integrity checksum (CRC-32)
Total Micro-TPLD Size	6 bytes