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Chapter 9
“Do I Know This Already?” Quiz
QoS Management Tools
1What do the following acronyms stand for? IPM, QPM, SAA, QDM
Internetwork Performance Monitor, QoS Policy Manager, Service Assurance Agent, and QoS Device Manager.
2What QoS management tool(s) enables you to define QoS policies, after which it creates the appropriate configurations, and deploys the configurations to identified network devices?
QPM
3Which QoS management tool(s) includes as a primary feature the capability to graph realtime information about bit/byte/packet rates and packet loss?
QDM, IPM, and QPM
4What QoS management tool(s) generates packets, called probes, and measures various performance attributes, such as delay and jitter?
SAA
5What QoS management tool(s) includes as a primary function the capability to troubleshoot and isolate network-wide performance issues by viewing the individual components in a complete end-to-end path through the network?
IPM
6What QoS management tool(s) is embedded into a router?
QDM
QoS Design
7List Step 1 in the QoS design process, and give a short summary of what the step includes.
Step 1 is to “determine customer priorities/QoS policy.” It includes discussions with appropriate personnel to determine what level of quality each type of traffic should get.
820 Appendix A: Answers to the “Do I Know This Already?” Quizzes and Q&A Sections
8List Step 3 in the QoS design process, and give a short summary of what the step includes.
Step 3 is to “implement policy.” It includes actual choices of QoS tools, and then the configuration of the tools.
9What are the ITU G.114 and Cisco recommendations for maximum one-way delay for voice calls?
The ITU recommends 150 ms, with Cisco stating it can be as high as 200 ms.
10Summarize the Cisco recommendations for marked values for voice and video traffic.
Cisco suggests that voice payload be marked with DSCP EF, CoS 5, and/or precedence 5; video payload with DSCP AF41, CoS 4, and/or precedence 4; and voice and video signaling with DSCP AF31, CoS 3, and/or precedence 3.
11Describe the Cisco recommendation for queuing voice and video traffic.
Cisco recommends using LLQ, placing the voice payload into the low-latency queue, and the video payload into a separate low-latency queue. If the IOS does not support LLQ, Cisco suggests enabling IP RTP Priority.
12List Step 4 in the QoS design process, and give a short summary of what the step includes.
Step 4 is to “monitor the network.” It includes using the QoS management tools to see historical trends, and the process of reviewing the reports versus policies to allow the four-step process to repeat, improving the quality of the QoS implementation over time.
Q&A
QoS Management
1What do the following acronyms stand for? IPM, QPM, SAA, QDM
Internetwork Performance Monitor, QoS Policy Manager, Service Assurance Agent, and QoS Device Manager.
2What QoS Management tool is actually a component of the CiscoWorks2000 Routed WAN Management Solution?
IPM.
3What QoS management tool is free?
QDM.
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4What QoS management tool(s) enables you to define QoS policies, after which it creates the appropriate configurations, and deploys the configurations to identified network devices?
QPM.
5Which QoS management tool(s) includes as a primary feature the capability to graph realtime information about bit/byte/packet rates and packet loss?
QDM, IPM, and QPM.
6Describe the two primary components of SMS and their general roles.
SMS includes the Service Level Manager, to which the user connects. The SMS Collection Managers (CMs) actually collect the statistics, which are then asynchronously fed back to the SLM.
7What QoS management tool(s) generates packets, called probes, and measures various performance attributes, such as delay and jitter?
SAA.
8What QoS management tool(s) includes as a primary function the capability to produce historical performance reports as compared to service-level agreements?
SMS.
9What QoS management tool(s) includes as a primary function the capability to troubleshoot and isolate network-wide performance issues by viewing the individual components in a complete end-to-end path through the network?
IPM.
10Does QDM or QPM support more devices?
QPM.
11Among QPM, QDM, SMS, and IPM, which tool(s) originally had a limited capability to create real-time or historical graphs of performance?
QPM.
12What QoS management tool(s) is embedded into a router?
QDM.
13Which QoS management tools are available in CiscoWorks2000 bundles?
IPM and SMS.
822 Appendix A: Answers to the “Do I Know This Already?” Quizzes and Q&A Sections
QoS Design
14List Step 1 in the QoS design process, and give a short summary of what the step includes.
Step 1 is to “determine customer priorities/QoS policy.” It includes discussions with appropriate personnel to determine what level of quality each type of traffic should get.
15List Step 2 in the QoS design process, and give a short summary of what the step includes.
Step 2 is to “characterize the network.” It includes a network audit, which is used to plan any needed upgrades of bandwidth, and to determine all the details needed in order to successfully classify the traffic in that particular network.
16List Step 3 in the QoS design process, and give a short summary of what the step includes.
Step 3 is to “implement policy.” It includes actual choices of QoS tools, and then the configuration of the tools.
17List Step 4 in the QoS design process, and give a short summary of what the step includes.
Step 4 is to “monitor the network”. It includes using the QoS management tools to see historical trends, and the process of reviewing the reports versus policies to allow the four-step process to repeat, improving the quality of the QoS implementation over time.
18What are the ITU G.114 and Cisco recommendations for maximum one-way delay for voice calls?
The ITU recommends 150 ms, with Cisco stating it can be as high as 200 ms.
19What delay component represents the most controllable variable delay in a voice call?
Queuing delay.
20How much bandwidth does a G.729 call require if ignoring the Layer 2 header/trailer? How much bandwidth does it require if using Frame Relay?
The call requires 24 kbps discounting the data-link framing; adding the Frame Relay headers and trailers, the call takes 26.4 kbps.
21Summarize the Cisco recommendations for marked values for voice and video traffic.
Cisco suggests that voice payload be marked with DSCP EF, CoS 5, and/or precedence 5; video payload with DSCP AF41, CoS 4, and/or precedence 4; and voice and video signaling with DSCP AF31, CoS 3, and/or precedence 3.
22Describe the Cisco recommendation for queuing voice and video traffic.
Cisco recommends using LLQ, placing the voice payload into the low-latency queue, and the video payload into a separate queue. If the IOS does not support LLQ, Cisco suggests enabling IP RTP Priority.
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23Summarize the Cisco recommendations for tuning shaping parameters when shaping must be enabled on VCs carrying voice.
Cisco suggests choosing configuration settings such that Bc is equal to CIR / 100, which will make Tc equal to 10 ms. Be is equal to zero to prevent bursting over the CIR. If adaptive shaping is used, Cisco suggests that the mincir be set equal to
the CIR value with no adaptive shaping being used.
Chapter 10
“Do I Know This Already?” Quiz
1What is instantaneous buffer overrun?
Instantaneous buffer overrun occurs when a switch port TX queue fills for an instant in time causing packet loss, which can adversely affect real-time applications.
2What is meant by the term “1p1q4t?”
This term denotes an interface that has a priority queue, a standard queue, and four drop thresholds in the standard queue.
3What packet or frame marking(s) can a Layer 2 switch use to prioritize traffic?
CoS only.
4What must be done for a Layer 2 switch to properly classify a packet received from a host across the WAN?
The router must map the IP precedence or IP DCSP value on the packet into a CoS value for the Layer 2 switch to properly classify the packet.
5What is a drop threshold?
Drop thresholds define the amount of the total Layer 2 buffer use that must be reached before a specified class of traffic is dropped.
6What is a trust boundary, and where should it be set?
A trust boundary is the first point in your network where you trust the CoS or ToS markings. Typically this point is on the IP Phones or access layer switches.
7Explain why the first packet in a flow may not retain the proper CoS values when a Catalyst 6500 is configured with a PFC.
If this flow is not in the flow cache of the PFC or the CEF FIB of the PFC2, the first packet of the flow is forwarded to the MSFC for a routing decision. After a routing decision has been made, the fist packet in the flow is routed to the correct interface.
