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Friday, February 7, 2014

What are the steps for Call Admission Control (CAC) implementation on CUBE ?

What is CAC and What are the steps involved for Call Admission Control (CAC) implementation on CUBE ?

CAC is nothing but Call Admission Control which
  1. Controls number of calls  based on resources & bandwidth
  2. Proactively reserve resources  for good quality video calls
  3. Ensure traffic adheres to QoS policies  within each network

CUBE can provide six different CAC mechanisms based on,

  • Total calls
  • CPU
  • Memory
  • IP call capacity
  • Max-connections
  • Call Spike detection
  • Dial-peer / Interface bandwidth
  • RSVP

CAC mechanisms ensure good QoS for video and voice calls and help meet the SLA

CAC Implementation

1. CAC Based on Total Calls, CPU or Memory


Configuration Example

call threshold  global [total/mem/cpu] calls low xx high yy
call treatment  on

Global Command

call   threshold global [total-calls | cpu-5sec | cpu-avg |   total-mem |  low  high 

call treatment on

call treatment cause-code ?

busy     Insert cause code   indicating the GW is busy (17)
no-QoS Insert cause code indicating the  GW can't provide QOS (49)
no-resource Insert cause  code indicating the GW has no resource  (47)

  • Call threshold values for total concurrent calls or CPU or memory to be handled by CUBE can be defined
  • Call treatment can be turned on to handle the call once the CAC limit is reached

2. CAC Based on IP Call Capacity

Configuration Example

endpoint circuit-id h323id CUBE1 AA  max-calls 500


voice  service voip
allow-connections h323 to h323
ip circuit max-calls 1500
ip circuit carrier-id AA  reserved-calls 1000  

  • IP call capacity on CUBE works in conjunction with the Cisco Gatekeeper (GK)
  • Call counting mechanism does not take into account the codec type used – this is taken into account by enabling bandwidth management on the Cisco GK
  • This only works if at least 1 call leg on CUBE is using H.323

3. CAC Based on Max Connections per destination

Configuration Example

dial-peer voice 1 voip
max-conn 2

  • Restricting the number of concurrent calls that can be active on a VoIP dial peer
  • Max-Conn works on individual dial-peers, does not provide CAC for the entire gateway

4. CAC based on Call Spike detection

CUBE rejects calls if call spike is detected


Configuration Example

call spike call-number [steps number-of-steps size milliseconds]
call spike 10 steps 5 size 200

5. CAC based Dial-peer or interface bandwidth


Configuration Example

dial-peer voice 1 voip
   max-bandwidth 160

6. CAC based on RSVP


Configuration Example

interface FastEthernet0/0
ip rsvp bandwidth 1000 1000

dial-peer voice 10 voip
destination-pattern 2...
session target ras
req-qos guaranteed-delay audio
req-qos guaranteed-delay video
acc-qos guaranteed-delay audio
acc-qos guaranteed-delay video

  • Synchronization of RSVP with H.323 signaling to ensure that the bandwidth reservation is established
  • RSVP ensures that bandwidth is reserved before the far end phone rings

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.


  1. You made a great point here. Thanks for sharing your thoughts.

  2. This comment has been removed by the author.

  3. With the VoIP phone service, users avail the add-on benefits like easy transfer of images, videos and texts on the same network. This service is gaining momentum in different spheres of industry from big corporate houses to small enterprises.


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