Flow-Based DWFQ Classification

Flow-Based DWFQ Classification

• IP TCP Payload

• Src.
• Addr.

• Dest.
• Addr.

• Protocol

• Src.
• Port

• Dest.
• Port

• Hash Algorithm

• #queue (9-bit index of the queue)

• The number of queues is 512 (not tunable).
• ToS is not used for classification (except in IOS version 11.1CC).

• WFQ classification uses these parameters:
• Source IP address
• Destination IP address
• Source TCP or UDP port
• Destination TCP or UDP port
• Transport protocol

• A hash algorithm is used to produce the index of the queue where the packet is enqueued.

DWFQ Insertion and Drop Policy

• DWFQ drops packets when both the individual queue limit and aggregate queue limit are reached.
• DWFQ is not as strict with aggressive flows as nondistributed WFQ.
• This insertion and drop policy is the same for all three versions of DWFQ (flow-based, ToS-based, and QoS-group-based).

DWFQ Insertion and Drop Policy (cont.)

• M>IQL?

• N>AQL?

• Enqueue
• packet

• Nth packet

• No

• No

• Yes

• Yes

• QL (queue limit) is the maximum number of packets the selected queue can hold.
• AQL (aggregate queue limit) is the maximum number of packets that the DWFQ system can hold.
• IQL (individual queue limit) is the maximum number of packets that an individual queue of a congested DWFQ system can hold.
• N is the number of packets in the DWFQ system when the Nth packet arrives.
• M is the number of packets in the queue into which the packet is classified.

• M>QL?

• Yes

• No