Flow-Based DWFQ Scheduling

Flow-Based DWFQ Scheduling

• Uses calendar queuing (optimized version of scheduling based on finish time; more jitter)
• Weight (IP Precedence) is not used for scheduling purposes (pure fair queuing)

• Flow-Based DWFQ System

• Hardware
• Queuing System

• Queue 1

• DWFQ
• Scheduler
• (Calendar
• Queuing)

• Interface

• Hardware Q

• Queue 2

• Queue N

• Calendar Queue

• Packets are scheduled (ordered) in advance for faster transfer to the hardware queue.

Configuring Flow-Based DWFQ

• fair-queue

• Router(config-if)#

• The command enables DWFQ on an interface connected to a VIP2-40 or newer interface processor.
• For all other interfaces, this command enables RSP-based WFQ.
• DWFQ can be configured on interfaces but not on subinterfaces.
• DWFQ is not supported on Fast EtherChannel, tunnel, or other logical or virtual interfaces (MPPP).

Configuring Flow-Based DWFQ (cont.)

• fair-queue aggregate-limit aggregate-packets

• Router(config)#

• The total number of packets in all output queues before some packets may be dropped

• fair-queue individual-limit individual-packets

• Router(config)#

• The maximum individual per-flow queue size during periods of congestion
• Defaults: Aggregate limit depends on the transmission rate and the available buffer space on the VIP; individual limit is half of the aggregate limit
• Don’t change the defaults unless necessary