Service Manual

Default dot1p to queue conguration is as follows:
Table 19. Dot1p to Queue Mapping
Packet-
Dot1p
0 1 2 3 4 5 6 7
Queue
2 0 1 3 4 5 6 7
PFC and ETS Conguration Examples
This section contains examples of how to congure and apply DCB policies on an interface.
Using PFC to Manage Converged Ethernet Trac
To use PFC for managing converged Ethernet trac, use the following command:
dcb-map stack-unit all dcb-map-name
Operations on Untagged Packets
The below is example for enabling PFC for priority 2 for tagged packets. Priority (Packet Dot1p) 2 will be mapped to PG6 on PRIO2PG
setting. All other Priorities for which PFC is not enabled are mapped to default PG – PG7.
Classication rules on ingress (Ingress FP CAM region) matches incoming packet-dot1p and assigns an internal priority (to select queue as
per Table 1 and Table 2).
The internal Priority assigned for the packet by Ingress FP is used by the memory management unit (MMU) to assign the packet to right
queue by indexing the internal-priority to queue map table (TABLE 1) in hardware.
PRIO2COS setting for honoring the PFC protocol packets from the Peer switches is as per above Packet-Dot1p->queue table (Table 2).
The packets that come in with packet-dot1p 2 alone will be assigned to PG6 on ingress.
The packets that come in with packet-dot1p 2 alone will use Q1 (as per dot1p to Queue classication – Table 2) on the egress port.
• When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 1 is halted.
• Queue 1 starts buering the packets with Dot1p 2. This causes PG6 buer counter to increase on the ingress, since P-dot1p 2 is
mapped to PG6.
• As the PG6 watermark threshold is reached, PFC will be generated for dot1p 2.
Generation of PFC for a Priority for Untagged Packets
In order to generate PFC for a particular priority for untagged packets, and conguring PFC for that priority, you should nd the queue
number associated with priority from TABLE 1 and Associate a DCB map to forward the matched DSCP packet to that queue. PFC frames
gets generated with PFC priority associated with the queue when the queue gets congested.
Congure Enhanced Transmission Selection
ETS provides a way to optimize bandwidth allocation to outbound 802.1p classes of converged Ethernet trac.
Dierent trac types have dierent service needs. Using ETS, you can create groups within an 802.1p priority class to congure dierent
treatment for trac with dierent bandwidth, latency, and best-eort needs.
For example, storage trac is sensitive to frame loss; interprocess communication (IPC) trac is latency-sensitive. ETS allows dierent
trac types to coexist without interruption in the same converged link by:
• Allocating a guaranteed share of bandwidth to each priority group.
Data Center Bridging (DCB)
235