In planning the wireless network, we will have to determine which wireless network architecture to adopt in the network environment. There are two architectures available, namely standalone and centrally coordinated wireless network.
Standalone architecture (Ad hoc mode)
By using ad hoc mode, all devices in the wireless network are directly communicating with each other in peer to peer communication mode. No access point (routers/switches) is required for communication between devices.
For setting up ad hoc mode, we need to manually configure the wireless adaptors of all devices to be at ad hoc mode instead of infrastructure mode, and all adaptors must use the same channel name and same SSID for making the connection active.
Ad hoc mode is most suitable for small group of devices and all of these devices must be physically present in close proximity with each other. The performance of network suffers while the number of devices grows. Disconnections of random device may occur frequently and also, ad hoc mode can be a tough job for network administrator to manage the network. Ad hoc mode has another limitation is that, ad hoc mode networks cannot bridge to wired local area network and also cannot access internet if without the installation of special gateways.
However, Ad hoc mode works fine in small environment. Because ad hoc mode does not need any extra access point (routers/switches), therefore it reduces the cost. Ad hoc can be very useful as a backup option for time being if network based on centrally coordinated wireless network (infrastructure mode) and access points are malfunctioning.
An ad hoc mode uses the integrated functionality of each adaptor to enable wireless services and security authentication. The characteristics of an Ad hoc wireless network are listed as below:
• All access points in the network operate independently and has own configuration file.
• Access point is responsible for the encryption and decryption.
• The network configuration is static and does not respond to changing network conditions.
Centrally Coordinated Architecture (Infrastructure mode)
The other architecture in wireless network is centrally coordinated (infrastructure mode). All devices are connected to wireless network with the help of Access Point (AP). Wireless APs are usually routers or switches which are connected to internet by broadband modem.
Infrastructure mode deployments are more suitable for larger organizations or facility. This kind of deployment helps to simplify network management, and allows the facility to address operational concerns. And resiliency is also assured while more users can get connected to the network subsequently.
The infrastructure mode provides improved security, ease of management, and much more scalability and stability. However, the infrastructure mode incurs extra cost in deploying access points such as routers or switches.
An infrastructure mode wireless network has the characteristics as below:
- The wireless centralized controller coordinates the activity of access point.
- The controller is able to monitor and control the wireless network by automatically reconfiguring the access point parameters in order to maintain the health of the network.
- The wireless network can be easily expanded or reduced by adding or removing access points and the network can be reconfigured by the controller based on the changes in RF footprint.
- Tasks such as user authentication, fault tolerance, control of configuration, policy enforcement and expansion of network are done by the wireless network controller.
- Redundant access points can be deployed in separate locations to maintain control in the event of an access point or switch failure.
