| Date of Issue: 05-01-2023 | Rate this Study Guide |
Question 1.
What is the only outbound queuing discipline used by generic traffic shaping (GTS)?
| a) | Priority queuing (PQ) |
| b) | Custom queuing (CQ) |
| c) | Low latency queuing (LLQ) |
| d) | Weighted fair queuing (WFQ) |
Question 2.
What queuing mechanism is invoked by ip rtp priority as well as an explicit QoS command?
| a) | Weighted fair queuing (WFQ) |
| b) | Class-based weighted fair queuing (CBWFQ) |
| c) | Weighted Random Early Detection (WRED) |
| d) | Low latency queuing (LLQ) |
Question 3.
For what kinds of applications is latency, especially variable latency, more important than throughput or loss?
| a) | Telnet |
| b) | Web browsing |
| c) | VoIP |
| d) | FTP |
Answers
Question 1.
What is the only outbound queuing discipline used by generic traffic shaping (GTS)?
| a) | Priority queuing (PQ) |
| b) | Custom queuing (CQ) |
| c) | Low latency queuing (LLQ) |
| d) | Weighted fair queuing (WFQ) |
| d) | Weighted fair queuing (WFQ) |
Explanation
GTS and class-based shaping use weighted fair queueing, while DTS and FRTS can use one of several configurable queuing schemes.
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Question 2.
What queuing mechanism is invoked by ip rtp priority as well as an explicit QoS command?
| a) | Weighted fair queuing (WFQ) |
| b) | Class-based weighted fair queuing (CBWFQ) |
| c) | Weighted Random Early Detection (WRED) |
| d) | Low latency queuing (LLQ) |
| d) | Low latency queuing (LLQ) |
Explanation
There are actually two ways to configure LLQ, one of which is outside the set of QoS commands. If you configure the IP Real-Time Protocol (RTP), you can use the ip rtp priority commands to identify a range of UDP ports that will carry high-priority voice. If, however, you configure LLQ within a policy-map command, you get more flexibility. No longer are you limited to port numbers, but you can use all the match criteria that access lists provide.
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Question 3.
For what kinds of applications is latency, especially variable latency, more important than throughput or loss?
| a) | Telnet |
| b) | Web browsing |
| c) | VoIP |
| d) | FTP |
| c) | VoIP |
Explanation
VoIP cannot tolerate significant variability of delay, but can tolerate a surprising amount of packet loss. It does not require a large amount of bandwidth, but the bandwidth must be there when needed.
With real-time multimedia applications, retransmission is usually impossible because it either increases the delay beyond acceptable limits or causes out-of-order packets (e.g., "If in Force so strong is Yoda, why can not words in right order he put?")
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