Cnm Format - HP FlexFabric 5700 series Configuration Manual

Figure 29 Data flow format

CNM format

When a CP detects the congestion state by sampling frames, it sends CNMs to the RPs.
The CP constructs a CNM as follows:
Uses the source MAC address of the sampled frame as the destination MAC address.
•
• Uses the destination MAC address of the sampled frame as the source MAC addresses.
Copies the VLAN tag and CN tag of the sampled frame.
•
Places the data as shown in
•
PDU EtherType—2 bytes in length. It indicates the Ethernet type of the PDU and has a value of
0x22E7.
CNM PDU—24 to 88 bytes of payload of the PDU.
Figure 30 CNM PDU format
As shown in
Field
Version
ReserverV
Quantized Feedback
CPID
cnmQoffset
cnmQdelta
Encapsulated priority
Encapsulated destination MAC
address
Encapsulated MSDU length
Encapsulated MSDU
Figure
Figure 31, a payload contains the following fields:
Length
4 bits
6 bits
6 bits
8 bytes
2 bytes
2 bytes
2 bytes
6 bytes
2 bytes
0 to 64 bytes
30.
Description
Its value is fixed at 0.
Its value is fixed at 0.
Quantized value indicating the extent of congestion.
Identifies the CP where congestion occurs.
Indicates the difference between instantaneous queue
size at the sampling point and desired queue length.
Indicates the difference between instantaneous queue
sizes at the current sampling point and at the previous
sampling point.
Priority of the sampled frame that triggered the CNM.
Destination MAC address of the sampled frame that
triggered the CNM.
Number of bytes in the Encapsulated MSDU field of the
sampled frame that triggered the CNM.
Initial bytes of the Encapsulated MSDU field of the
sampled frame that triggered the CNM.
96