Answers to the Chapter 10 Q&A Section 431
2
When should queuing be considered a viable implementation?
Queuing should be considered a solution when the router experiences more than
occasional congestion. If the existing traffic flow is having problems getting through the
router on a regular basis, queuing should be considered.
3
Should a queuing strategy be implemented on all WAN interfaces?
No. Queuing should be implemented on low-speed serial interfaces that experience
regular congestive conditions. If there is no congestion, queuing is not needed.
4
When is WFQ enabled by default?
WFQ is enabled by default on all serial interfaces with speeds of 2.048 Mpbs or lower.
Some technologies disable WFQ when the encapsulation is set on the interface.
5
What is the configurable parameter of WFQ?
The configurable parameter in WFQ is the congestive discard threshold. This is the
number of records that can exist in the queue at a given time.
6
What type of traffic gets the highest priority with WFQ?
Low-volume, interactive traffic gets the priority on a WFQ-enabled link.
7
How many queues are available in priority queuing?
There are four queues: high, medium, normal, and low.
8
If a default queue is not specified in the configuration, in which queue are traffic types not
defined in the priority list placed?
Unspecified traffic defaults to the normal queue unless configured otherwise. A default
queue should be defined in all queue lists.
9
What happens to traffic in a low-priority queue if there is always traffic in the high-priority
queue?
The TTL for the traffic can expire and the traffic can be dropped. Also, the low-priority
queue could fill up and overflow, causing dropped traffic.
10
How many queues are available in custom queuing?
There are 17 queues in custom queuing, 016. Only 116 are user-configurable.
11
How is traffic dispatched in a custom queuing implementation?
Traffic is dispatched on a round-robin basis. Each queue is serviced until its service
threshold is reached.
12
How can a higher priority be assigned to a particular queue?
The service thresholds for a particular queue can be expanded to give it a higher
percentage of the overall bandwidth.