QoS Flashcards
What type of delay accounts for the time it takes for a router or switch to take a packet from an input interface and place it in the output queue of the output interface?
Processing delay
What QoS process is responsible for distinguishing one kind of traffic from another by examining the fields in the packet and determining which traffic is to be treated differently?
Classification
What is the relative measure of the number of packets that were not received compared to the total number of packets initially transmitted?
Packet loss
What is the time it takes a packet to reach its destination after being transmitted from the sender?
Delay
What is the time it takes to put all the bits of a packet onto a link? It is a fixed value that depends on the speed of a link.
Serialization delay
What is the time it takes for a packet to travel from a source endpoint to a destination endpoint over a fiber-optic or copper medium?
Propagation delay
What is the amount of time it takes for a router or switch to take a packet from an input interface and place the packet into the output queue of the output interface?
Processing delay
What is the difference in the end-to-end delay between packets?
Jitter
Packet loss can be addressed by using which of the following approaches? (Choose all that apply.)
A. Increasing the speed of the link
B. Implementing QoS congestion-avoidance and congestion-management techniques
C. Implementing traffic policing
D. Avoiding use of traffic shaping
A. Increasing the speed of the link
B. Implementing QoS congestion-avoidance and congestion-management techniques
C. Implementing traffic policing
In what QoS model does the application request a specific kind of service from the network (such as bandwidth reservation) before it sends data onto the network?
Integrated service (IntServ)
What QoS model can be used by applications to signal their QoS requirements to the router?
Resource Reservation Protocol (RSVP)
In what QoS model does the network use QoS specification to classify, mark, shape, and police traffic to perform intelligent queuing?
Differentiated service (DiffServ)
What is the process of distinguishing one kind of traffic from another by examining the fields in the packet and determining which traffic is to be treated differently?
Classification
What are the layer 2 parameters that can be used for classification?
802.1Q class of service (CoS) bits and Multiprotocol Label Switching experimental values (MPLS EXP)
What are the layer 3 parameters that can be used for classification?
IP precedence (IPP), differentiated services code point (DSCP), IP explicit congestion notification (ECN), and source/destination IP address
What are the layer 4 parameters that can be used for classification?
Layer 4 protocol (TCP/UDP) and source/destination ports
What are the layer 7 parameters that can be used for classification?
Application signatures via Network Based Application Recognition (NBAR).
Marking at layer 2 can be done using what field?
802.1Q/p class of service (CoS)
Marking at layer 3 can be done using what field?
IP type of service (ToS) byte. The first 3 bits of the ToS byte are the IPP bits. These first 3 bits combined with the next 3 bits are known collectively as the DSCP bits.
If a session uses more than the allocated bandwidth, traffic can be dropped, which can be configured using what?
A Policier
What are considered traffic-smoothing tools that work in conjunction with buffering mechanisms?
Shapers
What does shaping use to ensure packets are not dropped immediately?
buffer
Which of the following are considered QoS models? (Choose all that apply.)
Best-effort
NBAR
IntServ
DiffServ
Best-effort
IntServ
DiffServ
True or false: Traffic shaping does not drop traffic, so retransmission is not necessary.
True
What provides bandwidth guarantees to given classes of traffic and fairness to discrete traffic flows within these traffic classes?
Class-based weighted fair queuing (CBWFQ)
What provides strict priority servicing and is intended for real-time applications, such as voice traffic?
Low-latency queuing (LLQ)
What command would you use to define a traffic class?
class-map command
What command would you use to create a traffic policy?
policy-map command
What in the QoS config determines how to treat the classified traffic?
policy-map
What command do use to apply the QoS policy on an interface?
service-policy command
True or false: Queuing mechanisms on a device are activated only when there is congestion and deactivated when congestion no longer exists.
True
Which of the following QoS implementation models is most commonly used?
Best-effort
Assured forwarding
IntServ
DiffServ
DiffServ
Which of the following queuing methods provides strict priority servicing and is intended for real-time applications such as voice traffic?
CBWFQ
LLQ
WRED
DWRED
LLQ
What type of QoS policy implementation is coded at the CLI and requires each interface to be individually configured? It is time-consuming.
Traditional CLI
Modular QoS at the Command Line (MQC)
Cisco AutoQoS
Cisco SDM QoS Wizard
Traditional CLI
What type of QoS policy implementation is coded at the CLI and uses configuration modules? It is the best method for QoS fine-tuning.
Traditional CLI
Modular QoS at the Command Line (MQC)
Cisco AutoQoS
Cisco SDM QoS Wizard
Modular QoS at the Command Line (MQC)
What type of QoS policy implementation applies a possible QoS configuration to the interface? It is the fastest way to implement QoS.
Traditional CLI
Modular QoS at the Command Line (MQC)
Cisco AutoQoS
Cisco SDM QoS Wizard
Cisco AutoQoS
What type of QoS policy implementation is an application for simple QoS configurations?
Traditional CLI
Modular QoS at the Command Line (MQC)
Cisco AutoQoS
Cisco SDM QoS Wizard
Cisco SDM QoS Wizard
Refer to the exhibit. Which statement about the last two lines of this policy map configuration is false?
R1(config)# policy-map COPP_policy
R1(config-pmap)# class COPP_class
R1(config-pmap-c)# police 300000 conform-action transmit exceed-action drop
R1(config-pmap-c)# class class-default
R1(config-pmap-c)# police rate 50 pps conform-action transmit exceed-action drop
The class-default class is always automatically placed at the end of every policy map.
It includes an implied match for all packets.
You can reconfigure the match criteria for the class-default class.
Traffic beyond 50 pps will be dropped.
You can reconfigure the match criteria for the class-default class.
