Dell S6000–ON Configuration Manual page 239

Figure 28. Illustration of Traffic Congestion
The system supports loading two DCB_Config files:
• FCoE converged traffic with priority 3.
• iSCSI storage traffic with priority 4.
In the Dell Networking OS, PFC is implemented as follows:
• PFC is supported on specified 802.1p priority traffic (dot1p 0 to 7) and is configured per interface.
However, only two lossless queues are supported on an interface: one for FCoE converged traffic
with priority 3 and one for iSCSI storage traffic with priority 4. You must configure the same lossless
queues on all ports.
• PFC delay constraints place an upper limit on the transmit time of a queue after receiving a message
to pause a specified priority.
• By default, PFC is enabled on an interface with no dot1p priorities configured. You can configure the
PFC priorities if the switch negotiates with a remote peer using DCBx
• During DCBx negotiation with a remote peer:
• DCBx communicates with the remote peer by LLDP TLV to determine current policies, such as PFC
support and ETS bandwidth allocation.
• If DCBx negotiation is not successful (for example, a version or TLV mismatch), DCBx is disabled and
PFC or ETS cannot be enabled.
• PFC supports buffering to receive data that continues to arrive on an interface while the remote
system reacts to the PFC operation.
• PFC uses DCB MIB IEEE 802.1azd2.5 and PFC MIB IEEE 802.1bb-d2.2
• PFC supports buffering to receive data that continues to arrive on an interface while the remote
system reacts to the PFC operation.
• PFC uses DCB MIB IEEE 802.1azd2.5 and PFC MIB IEEE 802.1bb-d2.2.
• PFC uses DCB MIB IEEE 802.1azd2.5 and PFC MIB IEEE 802.1bb-d2.2.
• PFC is supported on specified 802.1p priority traffic (dot1p 0 to 7) and is configured per interface.
However, only four lossless queues are supported on an interface: one for Fibre Channel over
Ethernet (FCoE) converged traffic and one for Internet Small Computer System Interface (iSCSI)
storage traffic. Configure the same lossless queues on all ports.
• A dynamic threshold handles intermittent traffic bursts and varies based on the number of PFC
priorities contending for buffers, while a static threshold places an upper limit on the transmit time of
a queue after receiving a message to pause a specified priority. PFC traffic is paused only after
surpassing both static and dynamic thresholds for the priority specified for the port.
Data Center Bridging (DCB)
239