2.2.2.7 Packet Pair Summary Message
A sink device automatically sends this message to the initiator device for the last Packet Pair Probe message in a train that it receives from the initiator. The Packet Pair Summary message summarizes all the changes in the sink device's timestamp obtained as each Packet Pair Probe message belonging to the same train is received.
The Packet Pair Summary message MUST contain the following message-specific header following the Handshake header.
|
|
|
|
|
|
|
|
|
|
1 |
|
|
|
|
|
|
|
|
|
2 |
|
|
|
|
|
|
|
|
|
3 |
|
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Sequence_Number |
|||||||||||||||||||||||||||||||
|
Interface_Speed |
|||||||||||||||||||||||||||||||
|
Reserved_1 |
Reserved_2 |
Num_Timestamp_Deltas |
|||||||||||||||||||||||||||||
|
Timestamp_Delta_List (variable) |
|||||||||||||||||||||||||||||||
|
... |
|||||||||||||||||||||||||||||||
Sequence_Number (4 bytes): An unsigned 32-bit integer in network byte order. The value of this field MUST be the value of the Sequence_Number field from the first Packet Pair Probe message in the train that triggered this message. In other words, it is taken from the Packet Pair Probe message wherein the F flag in the Handshake header is set.
Interface_Speed (4 bytes): An unsigned 32-bit integer that identifies the speed of the network interface on the sink device, expressed as bits per second. The value in this field is formatted using network byte order.
Reserved_1 (1 byte): This field MUST be set to 0 and ignored on receipt.
Reserved_2 (1 byte): This field MUST be set to 0 and ignored on receipt.
Num_Timestamp_Deltas (2 bytes): This field is an unsigned 16-bit integer that specifies the count of entries in the Timestamp_Delta_List field, in network byte order. The value in this field MUST be equal to the value of the Train_Size field, minus 1, of the Packet Pair Probe message that triggered this Packet Pair Summary message.
Timestamp_Delta_List (variable): This field specifies a list of Timestamp_Delta items, each describing the change in the sink's receive timestamp between two successive Packet Pair Probe messages in the same train. The change value is calculated by subtracting the older sink receive timestamp from the newer sink receive timestamp. The ordering of Timestamp_Delta items MUST represent the actual receive order of the corresponding Packet Pair Probe messages, going from oldest to latest. Each Timestamp_Delta item MUST have the following 8-byte structure.
-
0
1
2
3
4
5
6
7
8
91
0
1
2
3
4
5
6
7
8
92
0
1
2
3
4
5
6
7
8
93
0
1Value
...
-
Value (8 bytes): This field specifies an unsigned integer representing a timestamp value in network byte order. The unit of measurement MUST be in 100 nanosecond units.