QoS Flashcards
What layer is the CoS (Class of Service)
OSI Layer 2
What are the range of values for the CoS QoS field?
0-7
What CoS values are reserved for network use?
6 and 7
What is the CoS value for Cisco IP phone traffic?
- 3 for call signaling
- 5 for the voice payload packets
What is the default QoS CoS value
0 = Best Effort
What layer is the DSCP ToS marking?
OSI layer 3
What are the range of values for DSCP markings
0-63
What is the default DSCP ToS value?
0 = Best Effort
What is the DSCP value for Cisco IP phone traffic?
- 24 for call signaling (CS3)
- 46 for the voice payload packets (EF - expedited forwarding)
How do you assign DSCP values to traffic on a router?
- Using a ACL to reconize the traffic based on Layer 3 and Layer 4 information.
- NBAR - Network Based Application Reconition - can look at traffice based on Layer 3 to Layer 7 characteristics
Where should DSCP markings be set in the network?
As close to the source of the traffic as possible.
Does QoS markings alone insure Prioritazation of traffic?
No. Traffic management (queuing) needs to be configured on the routers and/or switches to act of the ToS/DSCP values.
List two types of Congestion Management:
- CBWFQ (Class Based Weighted Fair Queuing) - Gives bandwidth guarantees to to spicified traffic types
- LLQ (Low Latency Queuing) - is CBWFQ with a priority queue added that is send before other traffic that is not priority.
What Cisco CLI Module is used for QoS
MQC
What are the 3 sections of the MQC framwork for QoS
- Class Map - Define the traffic to take an action on
- Policy Map - Action to take on that traffic
- Service Policies - Apply the Policy Map to an interface
What are the time units in the IP SLA function?
seconds
