Cisco QoS FAQ: Call Admission Control and QoS Signaling
Q1. Why is CAC needed in an environment where LLQ has been properly implemented?
Figure: Legacy VoIP Network with CAC
Q2. Name four possible measures that a CAC mechanism can take in the event that the resources are not available to proceed with the call.
• Reroute call to alternate LAN/WAN link.
• Reroute call to alternate PSTN link.
• Return call to originating PBX for rerouting.
• Return a reorder tone, or fast-busy, to the caller.
Q3. How does a common channel signaling circuit, such as PRI, react to CAC?
Q4. How does a channel-associated signaling circuit, such as E&M or T1 CAS, react to CAC?
Q5. What is the difference between payload bandwidth and the bandwidth per call required for a voice conversation?
Q6. What is the definition of local-based CAC?
Q7. Name three of the five available local-based CAC mechanisms.
• Physical DS0 limitation
• Max-Connections dial-peer configuration
• VoFR, Voice-Bandwidth configuration
• Trunking condition
• Local Voice Busyout
Q8. What Cisco IOS command is used to enable physical DS0 limitation?
Q9. What Cisco IOS command is used to enable CAC on a VoFR network?
10 What type of circuit, CAS or CSS, will Local Voice Busyout (LVB) be most beneficial for?
Q11. What is the definition of measurement-based CAC?
Q12. What is the difference between LVBO and Advanced LVBO?
Q13. What is the difference between an SAA packet and a ping packet?
Q14. What measurements are gathered by SSA probes for PSTN fallback?
Q15. What Cisco IOS command is used to allow the destination node to participate in measurement based CAC
Q16. What is the definition of resource-based CAC?
Q17. Which resources can resource availability indication (RAI) currently monitor?
Q18. Which Cisco CallManager call-processing model utilizes location-based CAC?
Q19. For a gatekeeper to provide CAC, what must be configured for each link that requires protection?
Q20. What is IntServ and how does it work?
Q21. Name the messages used by RSVP to provide resource reservation and CAC.
Q22. What level of service must be in place to provide CAC?
23 Which RSVP profile should be configured to classify traffic for the priority queue within LLQ?