What Is Fat, Fit And Cloud AP?

Premier Mellanox Selections: best-selling Mellanox Switches, Network Cards, and Cables

Where do the terms Fit, Fat, and cloud AP come from? Do the names refer to their appearances? How can an AP be “Fit” or “Fat”? Where did these names originate?

First, let’s talk about “Fat” and “Fit”. These two words were originally used to name clients. During the initial client design, designers decide if functions need to be embedded in the device or integrated into the server. These considerations determine client and server costs, as well as the robustness, security, and flexibility of the entire system. Back to the point — what are Fat and Fit clients? An example is when an image is edited. If a Fat client is used, then all images need to be downloaded from the server. After these images are locally edited, the modified images are returned to the server. During this process, the Fat client requires a long time to start up and stop. However, the image edit itself is very quick. In contrast, if a Fit client is used, only visible parts of the images are downloaded at the beginning of the process. During image editing, each change is sent to the server to update the images in real time. In this case, the startup time is very short, but the edit process is slow. This should provide a better understanding of the concepts of “Fat” and “Fit”. In short, a “Fat” device possesses all functions and can work independently, whereas a “Fit” device needs to be connected to the control device (also called the “brain:”) to work.

Second, is the concept of a wireless Access Point (AP). An AP supports wired and wireless signal conversion as well as wireless signal receiving and transmitting functions. This allows them to transmit the wireless signals of mobile devices such as mobile phones and laptops. Fat APs can implement such functions independently, whereas Fit APs must interwork with the WLAN Access Controller (AC). On the flip side, Fat APs need to be deployed and configured one by one, which is inefficient. Now that we have established what Fit and Fat APs are, it is time to discuss a new kind of AP — cloud AP.

From its name, it would appear that a cloud AP is an AP that can be managed by the cloud — which is correct. To be more clear, a cloud AP is an AP that can be managed by the cloud management network. This makes APs plug-and-play and enables flexible AP expansion irrespective of available space. The “cloud AP” is embedded with time-sensitive WLAN AC functions, such as rapid roaming. Other, less time-sensitive WLAN AC functions, such as management, monitoring, and optimization, are deployed on the cloud management platform. This drastically improves the network-wide operation efficiency, security, and stability.

Today, most enterprise APs in the market support the switchover between Fit and Fat modes.

  1. Networking modes

Below are the wireless campus networking diagrams followed by descriptions of the AP working modes:

  1. Fat APs work independently from each other. Each AP needs to be connected to the network and configured one by one. Typically, Fat APs are used only when a small Wi-Fi coverage area is required. However, because managing Fat APs is complex and time-consuming, a growing number of enterprises have opted instead for networking modes that involve Fit APs and cloud APs.
  2. By interworking with the WLAN AC, switches, routers, and firewalls, Fit APs are able to provide Wi-Fi coverage with seamless roaming. When referring to APs in enterprise scenarios, “WLAN AC + Fit AP”networking is usually intended. This is the most-common networking mode for shopping malls, supermarkets, scenic spots, hotels, catering and entertainment establishments, and enterprise offices. For this WLAN, O&M is carried out locally, and the specifications of the WLAN AC deployed depends on the network scale.
  3. Cloud APs interwork with the cloud management platform, to provide a coverage area that reaches tens of thousands of square meters. In cooperation with the cloud management platform, cloud APs can implement plug-and-play deployment and cloud-based remote O&M in small and medium-sized simple networks and large-sized complex networks. In addition, through the open APIs of the cloud management platform, more industry Apps can be developed that leverage the location and IoT capabilities of the APs. The “cloud management platform + cloud AP”networking mode has become the preferred option for enterprises with many branches, such as retail stores, small and medium-sized enterprises (SMEs), and hotels.
  1. Functionality

In addition to wireless access, Fat APs also support security functions such as the DHCP server, DNS, VPN access, and firewall. A Fat AP typically comes with a simple management system and can work independently, to implement functions such as dial-up and routing.

In contrast to Fat APs, Fit APs provide only the wireless access function. Fit APs cannot work alone and need to interwork with the WLAN AC to form a complete network system.

A cloud AP is similar to a Fat AP in terms of functionality, routing support, DHCP server, and other functions. Therefore, the cloud AP is applicable to small-sized networks in SOHO environments. As well as providing the functions of a Fat AP, the cloud AP interoperates with the cloud management platform that manages, monitors, and optimizes the AP status. Cloud APs can also work with switches, routers, and firewalls for large-scale networking. In addition, the openness of the cloud management platform allows network Apps to be developed to further enhance cloud AP functionality.

  1. Wi-Fi network quality and experience

With Fat AP networking, roaming is not supported as each AP works independently. For this reason, a STA needs to be authenticated and obtain an IP address every time it moves between Fat AP coverage areas, even if the SSID does not change. As a result, STAs often disconnect from the network. In addition, load-balancing cannot be automatically performed between multiple Fat APs, to prevent STAs with weak signals from being dynamically switched to APs with a lighter load when many STAs are connected to one AP. The resulting AP heavy load leads to frequent network faults, such as congestion.

In contrast, Fit APs and cloud APs can implement rapid roaming and automatic signal switchover, to ensure STAs are always online. In addition, STAs can be automatically associated with APs with a lighter load based on the load balancing algorithm. SmartRadio, Huawei’s proactive load-balancing technology, helps STAs proactively roam to APs with strong coverage capabilities before user experience is affected, which improves network-wide Wi-Fi performance and ensures Wi-Fi experience of each access STA.

  1. O&M complexity

Fat APs cannot be centrally managed. Instead, each AP needs to be manually configured. With this in mind, imagine how long it would take to deploy hundreds or thousands of Fat APs — the workload is huge.

Fit APs, on the other hand, are centrally managed by the WLAN AC. That is, they do not need to be individually configured. The WLAN AC can manage hundreds or thousands of APs and can centrally deliver configurations in a batch. However, when multiple WLAN ACs are deployed across different physical areas (for example, in different buildings), ACs need to be configured one by one. In this case, the workload can still be huge.

Cloud APs go one step further to simplify O&M. Cloud APs can be deployed on the cloud management platform to implement cloud-based network planning, cloud-based deployment, cloud-based inspection, cloud-based O&M, and centralized full-lifecycle management and O&M, even for large-scale networks with branches distributed in multiple regions throughout China. This is achieved as follows: First, cloud APs are pre-configured on the cloud management platform. During on-site network deployment, all that is needed is to power on the APs, connect the network ports, and scan the QR codes to implement the plug-and-play function of the APs. The pre-configured policy is automatically delivered to the APs, to achieve Zero-Touch Provisioning (ZTP). The cloud management platform can monitor status (network, device, and STA connection) of all sites in a comprehensive and visualized manner.

In addition, many vendors who claim to provide cloud APs are merely deploying the AC or NMS on the VM while the local WLAN AC is still required — this is not a true cloud AP. So, what are the key features of a true cloud?

The Huawei Cloud Managed Network is as an example of how to deploy true cloud APs:

Management channel protocol: The cloud management platform communicates with cloud APs using the latest NETCONF and YANG models instead of traditional SNMP and MIB. This greatly improves efficiency, security, and reliability.

Cloud-based architecture: The cloud management platform uses a true cloud-based architecture that leverages SDN technology. It supports multi-tenant networks, elastic capacity expansion, and on-demand purchase, to greatly reduce deployment costs.

Simplified networking: Cloud APs are deployed locally without the need to deploy the WLAN AC, authentication server, or network management server to provide authentication through the portal, SMS, and social media. This considerably simplifies networking.

Open applications: Cloud APs provide various RESTful APIs through the cloud management platform to interoperate with third-party service systems and provide abundant upper-layer applications.


AP Type Wireless Access Additional Functions (Routing, DHCP) Roaming Load-Balancing Centralized Management and O&M Big Data Analytics and Other Applications
Fat AP × × × ×
Fit AP × √ (AC-based, provides limited centralized management and O&M) ×
Cloud AP √ (Tenant-based, offers network-wide centralized management and O&M)

Fat APs will eventually be phased out. Fit APs are in wide use on the existing traditional networks.

Cloud APs integrate the advantages of Fat and Fit APs. They support the functions of Fat APs, such as routing, dialup, and DHCP, and are applicable to small-sized networking. In addition, cloud APs support the roaming and load balancing functions of Fit APs, to ensure user experiences of large-sized Wi-Fi networks. In addition, the cloud management platform is interoperable with various industry applications that promote rapid digital transformation of enterprises, such as big data analytics-based customer group analysis, IoT-based Electronic Shelf Labels (ESLs), and asset management. Cloud APs and the accompanying cloud management platform are the optimal choice for future enterprise networks.

If you have different opinion about the Fat, Fit And Cloud APs, welcome to leave your comment.

Related Topics:

Why Upgrade to Cisco Catalyst 9100 WiFi 6 Access Point?

4 x 4 MU-MIMO APs And Enterprise Wi-Fi 6 Networks

Buyer Guide: 4 Misunderstandings when choosing an Access Point

12 Questions You Need to Know about Wi-Fi 6

5 Models Comparison of Cisco Catalyst 9100 WiFi 6 AP

Aruba Instant on Series Datasheet: Switch and AP

How to choose the Cisco on-premise access points: Cisco 1800 AP & Cisco 2800 AP

Share This Post

Post Comment