Committed Access Rate

Definition of Committed Access Rate

Committed Access Rate (CAR) is a networking term that refers to the guaranteed minimum data transfer rate offered by an Internet Service Provider (ISP) to its customers. It ensures that a specific amount of bandwidth will always be available to the customer, regardless of network congestion or other factors. CAR is a crucial parameter for service-level agreements (SLAs) between ISPs and clients, as it affects the quality and consistency of the internet service provided.


The phonetic pronunciation of “Committed Access Rate” is: kəˈmɪtəd (Committed)ˈæk.sɛs (Access)reɪt (Rate)

Key Takeaways

  1. Committed Access Rate (CAR) is a traffic management mechanism provided by network devices, such as routers, to ensure bandwidth allocation for specific types of traffic by setting a limit on the data rate that these traffic types can use.
  2. CAR operates by monitoring and classifying incoming traffic, based on predefined criteria, such as source and destination IP addresses, protocol types, and port numbers. Traffic that exceeds the CAR limit is either dropped or marked for selective priority treatment, helping to maintain network performance and avoid congestion.
  3. Using CAR effectively helps administrators maintain Quality of Service (QoS) for critical traffic and applications, ensuring that important data streams receive the required bandwidth, while potentially limiting non-critical or malicious traffic.

Importance of Committed Access Rate

Committed Access Rate (CAR) is an important technology term because it ensures a guaranteed level of network performance and bandwidth allocation for users and applications.

By defining a specific rate at which the network devices, such as routers or switches, commit to providing data transfer, CAR allows service providers and network administrators to manage resources effectively, prioritize crucial applications, and prevent network congestion.

This pre-defined allocation of bandwidth leads to improved overall network stability, enabling the network to deliver consistent and reliable services, and providing users with a higher Quality of Experience (QoE).


Committed Access Rate (CAR) serves as a crucial element in the management of network resources, particularly in optimizing the overall performance of a network. One of its primary purposes is to ensure consistent and efficient allocation of bandwidth to different users or devices connected to the network, thereby preventing bandwidth-hogging issues and providing fair distribution to all users. CAR is mostly employed by the Internet Service Providers (ISPs) as well as businesses that want to maintain streamlined network operations.

By implementing CAR, network administrators are able to establish traffic policies, set rate limits, and prioritize data packets based on their importance, allowing them to maintain a required level of service quality for critical applications even during peak data usage periods. Besides regulating bandwidth allocation, CAR is instrumental in ensuring enhanced network security. By applying this technique, a network can effectively manage, identify, and control undesired or harmful traffic.

In doing so, it restricts potential threats such as Denial of Service (DoS) attacks and other malicious activities on the network. Additionally, using CAR allows organizations to reinforce their Service Level Agreements (SLAs) with customers, guaranteeing that the provided services meet the agreed-upon performance standards. Furthermore, in cases of congestion, CAR can be employed to throttle or drop packets, thus reducing the interference with high-priority data transmissions.

Overall, Committed Access Rate contributes significantly to maintaining an organized and resilient network infrastructure that supports the demands of users and services alike.

Examples of Committed Access Rate

Committed Access Rate (CAR) is a traffic policing and shaping mechanism used in networking to limit the rate of incoming and outgoing traffic on a network, ensuring that data traffic adheres to the predefined service level agreements (SLAs). Here are three real-world examples of CAR technology usage:

Internet Service Providers (ISPs): ISPs use CAR technology to manage bandwidth allocation for their customers. They set up individual CAR rules for each customer to ensure that each user gets the subscribed bandwidth while preventing the network from getting overloaded. For example, if a customer has a 100 Mbps plan, the ISP implements CAR rules that limit the maximum traffic rate to 100 Mbps for that particular connection. This way, each customer receives the service quality they paid for, and the ISP can maintain a stable network.

Enterprise Networks: Companies with large networks may use CAR to manage and allocate bandwidth across different departments and applications. For example, in a multi-departmental organization, the IT department may set Committed Access Rates to ensure that critical applications, such as video conferencing or business applications, have guaranteed levels of bandwidth. This is done to prevent network congestion and ensure optimal performance for mission-critical services.

Data Centers: In data centers, where multiple clients host their servers and applications, network administrators implement CAR to regulate traffic between the servers and the clients’ networks. By implementing CAR rules based on the clients’ subscription plans, data centers can allocate the required bandwidth to each client, ensuring that all clients receive their committed resources, while avoiding network congestion and maintaining performance.Overall, Committed Access Rate is a valuable technology to guarantee service quality, avoid network congestion, and ensure optimal resource allocation across different users and services.

FAQ: Committed Access Rate

What is Committed Access Rate (CAR)?

Committed Access Rate (CAR) is a network bandwidth management method implemented on network devices, such as routers, to control the rate at which traffic is sent and received. It ensures that network resources are fairly allocated and provides congestion control over high traffic loads.

How does Committed Access Rate work?

CAR works by using a token bucket algorithm that manages traffic flow according to a set of predefined parameters, such as the committed information rate (CIR), the committed burst size (Bc), and the excess burst size (Be). These parameters help in shaping the traffic, allowing network administrators to limit or prioritize specific types of data traffic, ensuring optimal performance and fair resource allocation.

What are the benefits of using Committed Access Rate?

Implementing CAR provides several benefits, including better traffic management, improved network performance, and reduced congestion during peak periods. Additionally, it enables network administrators to prioritize essential services over less critical data, ensuring that critical applications and services get the bandwidth they need for optimal performance, and preventing the abuse of network resources by excessive data usage.

What is the difference between Committed Access Rate and Committed Information Rate?

Committed Access Rate (CAR) is a traffic shaping mechanism, while Committed Information Rate (CIR) is one of the parameters used in CAR. The CIR is the guaranteed bandwidth that a service provider commits to providing the user, and it is measured in bits per second (bps). CAR utilizes the CIR parameter to manage the traffic flow by limiting or prioritizing specific types of data traffic.

How do I configure Committed Access Rate on a router?

To configure Committed Access Rate on a router, you’ll need to access the router’s command-line interface (CLI) and navigate to the appropriate interface configuration mode. From there, you can use traffic-shaping commands to define the CAR parameters, such as CIR, Bc, and Be. Specific configuration steps may vary depending on the router’s manufacturer and model, so it’s essential to refer to the router’s documentation for precise instructions.

Related Technology Terms


  • Bandwidth Allocation
  • Quality of Service (QoS)
  • Traffic Shaping
  • Service Level Agreement (SLA)
  • Congestion Management


Sources for More Information

  • Cisco Systems –
  • Juniper Networks –
  • Techopedia –
  • –

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