Weighted Fair Queuing Voice and Data Integration

Weighted Fair Queuing Voice and Data Integration

• WAN link speed 128 kbps
• Voice requirements 30 kbps
• VoIP is Precedence 5 (counts as 6 data sessions)
• 1 VoIP session, 5 data sessions
• Voice gets up to 6/(6+5)*128 = 69 kbps (enough)
• 1 VoIP session, 20 data sessions
• Voice gets up to 6/(6+20)*128 = 29 kbps (problem)

Benefits and Drawbacks of Weighted Fair Queuing

• Benefits
• Simple configuration (classification does not have to be configured)
• Guarantees throughput to all flows
• Drops packets of most aggressive flows
• Supported on most platforms
• Supported in all IOS versions (above 11.0)
• Drawbacks
• All drawbacks of FIFO queuing within a single queue
• Multiple flows can end up in one queue
• Does not support the configuration of classification
• Can not provide fixed bandwidth guarantees
• Performance limitations due to complex classification and scheduling mechanisms

Weighted Fair Queuing Configuration

• Congestive discard threshold (CDT)
• Number of messages allowed in the WFQ system before the router starts dropping new packets for the longest queue
• Value can range from 1 to 4096 (default is 64)

• fair-queue [cdt [dynamic-queues [reservable-queues]]]

• Router(config-intf)#

Weighted Fair Queuing Configuration (cont.)

• dynamic-queues
• Number of dynamic queues used for best-effort conversations (values are: 16, 32, 64, 128, 256, 512, 1024, 2048, and 4096–the default is 256)
• reservable-queues
• Number of reservable queues used for reserved conversations in the range 0 to 1000 (used for interfaces configured for features such as RSVP - the default is 0)

• fair-queue [cdt [dynamic-queues [reservable-queues]]]

• Router(config-intf)#