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Flashcards in QoS Deck (18)
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1
Q

What layer is the CoS (Class of Service)

A

OSI Layer 2

2
Q

What are the range of values for the CoS QoS field?

A

0-7

3
Q

What CoS values are reserved for network use?

A

6 and 7

4
Q

What is the CoS value for Cisco IP phone traffic?

A
  • 3 for call signaling
  • 5 for the voice payload packets
5
Q

What is the default QoS CoS value

A

0 = Best Effort

6
Q

What layer is the DSCP ToS marking?

A

OSI layer 3

7
Q

What are the range of values for DSCP markings

A

0-63

8
Q

What is the default DSCP ToS value?

A

0 = Best Effort

9
Q

What is the DSCP value for Cisco IP phone traffic?

A
  • 24 for call signaling (CS3)
  • 46 for the voice payload packets (EF - expedited forwarding)
10
Q

How do you assign DSCP values to traffic on a router?

A
  1. Using a ACL to reconize the traffic based on Layer 3 and Layer 4 information.
  2. NBAR - Network Based Application Reconition - can look at traffice based on Layer 3 to Layer 7 characteristics
11
Q

Where should DSCP markings be set in the network?

A

As close to the source of the traffic as possible.

12
Q

Does QoS markings alone insure Prioritazation of traffic?

A

No. Traffic management (queuing) needs to be configured on the routers and/or switches to act of the ToS/DSCP values.

13
Q

List two types of Congestion Management:

A
  1. CBWFQ (Class Based Weighted Fair Queuing) - Gives bandwidth guarantees to to spicified traffic types
  2. LLQ (Low Latency Queuing) - is CBWFQ with a priority queue added that is send before other traffic that is not priority.
14
Q

What Cisco CLI Module is used for QoS

A

MQC

15
Q

What are the 3 sections of the MQC framwork for QoS

A
  1. Class Map - Define the traffic to take an action on
  2. Policy Map - Action to take on that traffic
  3. Service Policies - Apply the Policy Map to an interface
16
Q

What is the difference between traffic shaping and traffic policing

A

Traffic Shaping - Buffers traffic so traffic stays within the desired rate limit

Traffic Policing - Drops or re-marks excess traffic to enforce the specified rate. (more agressive form of management than shaping)

17
Q
A
18
Q

What are the time units in the IP SLA function?

A

seconds