Connection Admission Control


Connection Admission Control (CAC) is a networking concept focused on preventing network congestion. It is a method of controlling or limiting network access to ensure a high level of service for those already connected. Essentially, CAC can either admit or reject a connection request based on the network’s ability to provide sufficient resources.


The phonetic pronunciation of “Connection Admission Control” is: kəˈnekSH(ə)n – ədˈmiSHən – kənˈtrōl

Key Takeaways

  1. Network Resource Management: Connection Admission Control (CAC) is a traffic management concept primarily used in telecommunication networks to maintain a high quality of service. It plays a crucial role in avoiding network congestion by limiting the number of connections allowed into a network or between networks.
  2. Quality of Service (QoS): CAC is an essential component for maintaining a good Quality of Service (QoS). By controlling the traffic entering a network, it ensures that the network can serve each client without suffering from overuse or congestion. If a proposed connection cannot be served adequately, it will be refused by the CAC mechanism.
  3. Dynamic and Reactive: CAC algorithms can be dynamic and reactive to the changing conditions of the network. They continuously monitor the state of the network and make real-time decisions to grant or deny connection requests based on the current traffic flow and network capacity.


Connection Admission Control (CAC) is an important term in technology as it plays a critical role in managing the network resources in telecommunication scenarios. This term essentially refers to the set of protocols and procedures that are used to determine and evaluate whether a new call or transmission request can be accommodated without adversely affecting the existing Quality of Service (QoS).

In other words, CAC helps in avoiding network congestion and ensuring that all existing connections maintain a specific level of performance, which is crucial in systems like IP telephony and video conferencing. As a result, proper implementation of CAC contributes to optimal network utilization, better user experience, and overall efficiency.


Connection Admission Control (CAC) is vital for enhancing the quality of service in networks, particularly those that carry real-time traffic. It is employed to optimize the use of available bandwidth and to limit network congestion, both critical in maintaining the quality of service. Primarily, it regulates the acceptance of traffic over a network by evaluating the network’s capacity and the current resources available prior to approving any new connection requests. This way, it ensures that an optimal performance level persists, providing smooth and uninterrupted flow of data.

The fundamental function of CAC is to prevent oversubscription of available bandwidth. Oversubscription could result in data packet loss and low-grade overall performance of the network. It plays a significant role in contexts where the transmission of packets is time-sensitive, such as in VoIP (Voice over Internet Protocol), video conferencing, and real-time online gaming.

By denying new connection requests when the network lacks resources, CAC helps maintain the quality of current operational connections, avoiding service degradation. Thus, it can handle network traffic efficiently and assures users of maximum connectivity.


Connection Admission Control (CAC) is an important concept for telecommunication networks, used to prevent network congestion by limiting the amount of traffic allowed into a network.

Here are three real-world examples:

1. Telecommunication Networks: Telecommunication providers like AT&T, Verizon, or Vodafone use CAC to manage their bandwidth and prevent network congestion that could lead to call or data transfer failure. Their systems check the network’s capacity before establishing any communication to ensure it can handle the expected traffic.

2. Video Conferencing Systems: In platforms like Zoom, Microsoft Teams, or Cisco WebEx, CAC is applied to ensure the system can handle the number of video calls at any given time. Before a new call is admitted, the system checks whether there is enough bandwidth available to support the new connection without affecting existing connections.

3. Internet Service Providers (ISPs): ISPs, such as Comcast, Time Warner, or Cox, use CAC to manage their bandwidth among clients. When a customer tries to connect to the internet, the ISP verifies its resources to ensure the rest of the network won’t be negatively affected by admitting the new connection.

Frequently Asked Questions(FAQ)

Q: What is Connection Admission Control (CAC)?

A: Connection Admission Control (CAC) is a network feature that is used to prevent network congestion by limiting the number of connections or flows accepted into a network or network segment.

Q: Why is Connection Admission Control important in a network?

A: CAC plays a crucial role in maintaining the quality of service in networks, particularly in real-time communication networks where data packet delay can significantly affect the quality of service.

Q: How does Connection Admission Control work?

A: When a connection request is made, the CAC evaluates whether the network or the specific segment has enough resources to handle the new connection without degrading the quality of the existing connections. If the network can handle it, the connection is admitted. If not, the connection is denied.

Q: Does Connection Admission Control prioritize connections?

A: Yes, certain types of CACs can prioritize connections based on the type of service, the protocol being used, or other specified parameters. This is especially useful in networks where certain types of data flow are more important than others.

Q: Which types of networks use Connection Admission Control?

A: CAC is commonly used in telephone and broadband networks, as well as in Internet Service Provider (ISP) networks, and it is especially important in real-time communication networks where maintaining data packet delivery times is crucial.

Q: Is Connection Admission Control dependent on the network’s bandwidth?

A: Yes, the primary resource that CAC takes into account before admitting a connection is the available network bandwidth. However, it may also consider other factors like CPU usage, the number of connections already present, and more.

Q: Can Connection Admission Control be bypassed?

A: Theoretically, attempting to bypass CAC can lead to network congestion and degradation of the quality of service. It is advisable to adhere to the established CAC protocols to maintain optimal network performance. **

Q: How is Connection Admission Control related to Quality of Service (QoS)?

A: CAC is one aspect of a wider Quality of Service strategy. While QoS encompasses various techniques that aim to guarantee certain performance levels for different types of traffic, CAC specifically aims to prevent network congestion or overload.

Related Finance Terms

  • Quality of Service (QoS)
  • Bandwidth Allocation
  • Network Congestion
  • Packet Loss
  • Traffic Engineering

Sources for More Information


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