Cisco Queuing Techniques

Some basic queuing techniques available on cisco devices:

1. FIFO - this is the simplest algorithm; basically "First-In, First-Out"

2. PQ - Priority Queuing allows for the prioritization of traffic but can cause queue starvation because the top priority queue is always serviced first.

3. RR - Round-robin uses multiple queues to provide equal access to all queues but offers no prioritization.

4. WRR - Weighted-round-robin is a round-robin queue that allows for priority queues. however, but some implementations don't provide the correct bandwidth allocation because of the way bytes are counted. In cisco terms, CQ (custom queuing) is an implementation of WRR, allowing for up to 16 queues for traffic classification

5. DRR - Deficit round robin solves the problem of WRR by keeping a "deficit" county that subtracts during the following cycle any extra bytes received during the previous cycle. This is only available on the cisco 12000 series routers.