Queuing Mechanisms Objectives

Summary

• Upon completing this lesson, you should be able to:
• Describe FIFO queuing
• Describe the drawbacks of FIFO queuing
• Configure FIFO queuing on Cisco routers
• Monitor and troubleshoot FIFO queuing

Lesson Review

• Why is FIFO the fastest queuing mechanism?
• Describe the classification and scheduling of FIFO queuing.
• List the drawbacks of FIFO queuing.

• © 2001, Cisco Systems, Inc.

• Priority Queuing

• QOS v1.0—3-

Objectives

• Upon completing this lesson, you will be able to:
• Describe priority queuing
• Describe the benefits and drawbacks of priority queuing
• Configure priority queuing on Cisco routers
• Monitor and troubleshoot priority queuing

Priority Queuing

• Priority queuing (PQ) uses four FIFO queues.

• Priority Queuing System

• Hardware
• Queuing System

• High?

• Queue 1

• Pre-emptive
• Scheduler

• Interface

• Forwarded Packets

• Hardware Q

• Tail-drop

• Medium?

• Queue 2

• Tail-drop

• Normal?

• Queue 3

• Tail-drop

• Low?

• Queue 4

• Tail-drop

Priority Queuing Classification

• Priority queuing classification for IP supports these options:
• Source interface
• IP access list (standard and extended)
• Packet size (greater or smaller than specified)
• Fragments
• TCP source or destination port numbers
• UDP source or destination port numbers