Data flow format
An RP can add CN tags to outgoing Ethernet frames to distinguish between CCFs. A CN tag defines a CCF.
As shown in Figure 31, the CN tag contains the following fields:
EtherType—Indicates the Ethernet type of the data packet, 2 bytes in length and assigned a value of 0x22E9.
RPID—Locally assigned and 2 bytes in length. When receiving a CNM, the RP uses this field to identify the CCF that causes congestion and then rate limits that CCF.
When only one CCF exists, the RP may not add a CN tag to packets. In this case, the triggered CNM carries a CN tag with the RPID as 0.
A CN tag is confined within its CND. When a packet leaves a CND, the CN tag is stripped off.
Figure 31: Data flow format
