Term
| What is processing delay? |
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Definition
| Processing delay is the time it takes for a device such as a router to perform all the tasks necessary to move a packet from the input (ingress) interface to the output (egress) interface |
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Term
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Definition
| Queuing delay is the amount of time that a packet spends in the output queue of a router interface. |
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Term
| What is serialization delay? |
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Definition
| Serialization delay is the time it takes to send all the bits of a frame to the physical meduim for transmission across the physical layer. |
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Term
| What is propagation delay? |
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Definition
| Propagation delay is the time it takes for the bits of a frame to cross the physical link from end to end. |
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Term
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Definition
| Delay variation or jitter, is the variation in delays experianced by the packets of the same flow. |
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Term
| Implementing QoS involved what three major steps? |
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Definition
1. Identifying traffic types and their requirements. 2. Classifying traffic based on the requirements identified 3. Defining policies for each traffic class. |
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Term
| Describe the Best-Effort QoS model. |
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Definition
| The best-effort model means that no QoS policy is implemented. Within this model, packets belonging to voice calls, emails, file transfers, and so on are treated as equally important. |
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Term
| Describe the Integrated Services QoS model. |
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Definition
| The Integrated Services (IntServ) model is based on explicit signaling and managing/reserving network resources for the applications that need it and demand it. IntServ is ofter referred to as Hard-QoS, because it guarantees characteristics such as bandwidth, delay, and packet loss, thereby providing a predictable service level. |
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Term
| Describe how the Integrated Services model used Resource Reservation Protocol (RSVP) as its signaling protocol. |
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Definition
| An application that has a specific bandwidth requirement must wait for RSVP to run along the path from source to destination, and request bandwidth reservation for the application flow. If the RSVP attempt to reserve bandwidth along the path succeeds, the application can begin operating. If RSVP fails to successfully reserve the bandwidth hop by hop all the way from source to destinationm the application cannot begin operating. |
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Term
| Describe the basic concept of the Differentiated Services QoS model |
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Definition
| Differentiated Services (DiffServ) has been called the "Soft QoS" model, since it is not a guaranteed QoS model, but a highly scalable one. Pure DiffServ does not use signaling, but is based on a per-hop behavior (PHB), meaning that each hop in a network must be preprogrammed to provide a specific level of service for each class of traffic. |
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Term
| What are the three major steps involved when implementing QoS with Modular QoS Command-Line Interface (MQC)? |
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Definition
1. Define traffic classes using the class-map command. 2. Define QoS policies for the defined traffic classes using the policy-map command 3. Apply the defined policies in the inbound or outbound direction to each intended interface using the service-policy command, |
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Term
| What type of match statements are used when defining a class map? |
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Definition
| Class maps are composed of one or more match statements, depending on whether the class map contrains the match-any or the match-all command (match-all being the default). |
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Term
| Describe what a policy map is used for. |
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Definition
| With policy maps, you create traffic policies by associating required QoS features to traffic classes defined by class maps |
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Term
| What is the class-default statement used for in a class map? |
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Definition
| The class-default gets no QoS guarantees and can use a FIFO or a WFQ. Any traffic that the defined classes do not match will still be treated as class-default |
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Term
| What command applies a policy map to a specific interface? |
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Definition
| service-policy {input | output} policy-map |
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Term
| What command displays all the configured class maps? |
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Definition
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Term
| What command displays all the configured policy maps? |
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Definition
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Term
| What command displays QoS interface statistics? |
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Definition
| show policy-map interface interface |
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Term
| How does AutoQoS handle traffic classification when enabled? |
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Definition
| AutoQoS automatically discovers applications and protocols (Using Network Based Application Recognition, or NBAR). It also used Cisco Discovery Protocol (CDP) to check whether an IP phone is attached to a switch port. |
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Term
| How does AutoQoS handle policy generation when enabled? |
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Definition
| It checks interface encapsulations, and accordingly, it considers usage of features such as fragmentation, compression, and traffic shaping. Access lists, class maps, and policy maps are automatically generated. |
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Term
| How is QoS configured when you enable AutoQoS on a router? |
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Definition
| It is enabled by entering only one command, auto qos, at the interface. The proper commands to classify, mark, prioritize, preempt packets, and so on are added to the configuration appropriately. |
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Term
| How does AutoQoS handle monitoring and reporting when enabled? |
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Definition
| It generates system logging messages, SNMP traps, and summary reports. |
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Term
| What kind of functions are performed by AutoQoS when enabled on a WAN device or interface? |
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Definition
| It creates a traffic class for voice payload (RTP), and it builds another class for voice signaling (Skinny, H.323, or MGCP). Service policies for voice bearer and voice signaling are created and deployed using LLQ with bandwidth guarantees. Voice traffic is assigned to the priority queue. |
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Term
| What are some prerequisites that must be met before AutoQoS is enabled on an interface? |
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Definition
1. Cisco Express Forwarding (CEF) must be enabled. CEF is a prerequisite for NBAR 2. NBAR must be enabled. AutoQoS for the Enterprise uses NBAR for traffic discovery and classification. 3. The correct bandwidth on the interface must be configured. AutoQoS configures LLQ, cRTP, and LFI based on the interface type and the interface bandwidth. |
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Term
| What command allows the router to discover and analyze network traffic entering an interface using NBAR? |
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Definition
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Term
| What command builds class maps and then creates and applies a policy map on an interface? |
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Definition
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