From the perspective of architecture, WiFi routers can be divided into the first generation of single-bus single-CPU structure WiFi routers, the second generation of single-bus master-slave CPU structure WiFi routers, the third generation of single-bus symmetrical multi-CPU structure WiFi routers; the fourth generation of WiFi routers Multi-bus and multi-CPU structure WiFi routers, fifth-generation shared memory structure WiFi routers, sixth-generation cross-switch architecture WiFi routers, and cluster system-based WiFi routers.
A WiFi router has four elements: input ports, output ports, switches, route processors, and other ports.
The input port is the physical link and the entry point of the input packet. Ports are usually provided by line cards, a line card typically supports 4, 8 or 16 ports, and one input port has many functions. The first function is to perform data link layer encapsulation and decapsulation. The second function is to look up the destination address of the incoming packet in the forwarding table to determine the destination port (called route lookup). The route lookup can be implemented using general hardware, or by embedding a microprocessor on each line card. . Third, in order to provide QoS (Quality of Service), the port classifies the received packets into several predefined service levels. Fourth, the ports may need to run data link-level protocols such as SLIP (Serial Wire Internet Protocol) and PPP (Point-to-Point Protocol) or network-level protocols such as PPTP (Point-to-Point Tunneling Protocol). Once the route lookup is complete, a switch must be used to route the packet to its output port. If the WiFi router is input-queued, there are several inputs that share the same switch. The final function of such an input port is to participate in an arbitration agreement on a common resource such as a switch.
Swap switches can be implemented using a number of different techniques. By far the most used switch technology is bus, crossbar and shared memory. The simplest switches use a single bus to connect all input and output ports. The disadvantage of bus switches is that their switching capacity is limited by the capacity of the bus and the additional overhead of arbitration for a shared bus. Crossbars provide multiple data paths through switches, and a crossbar with N×N crosspoints can be thought of as having 2N buses. If a cross is closed, the data on the input bus is available on the output bus, otherwise it is not available. The closing and opening of the intersection is controlled by the scheduler, therefore, the scheduler limits the speed at which the switches can be exchanged. In shared memory WiFi routers, incoming packets are stored in shared memory, and only pointers to the packets are exchanged, which increases the switching capacity, but the speed of switching is limited by the memory capacity Take speed. Although memory capacity can double every 18 months, memory access time decreases by only 5% per year, an inherent limitation of the shared memory switch.
The output port stores packets before they are sent to the output link, and can implement complex scheduling algorithms to support requirements such as priority. Like input ports, output ports must also support data link layer encapsulation and decapsulation, as well as many higher-level protocols.
The routing processor computes the forwarding table to implement the routing protocol and runs the software that configures and manages the WiFi router. At the same time, it also handles those packets whose destination address is not in the forwarding table of the line card.
Other ports generally refer to the control port. Since the WiFi router itself does not have input and terminal display devices, but it needs to be configured properly before it can be used normally, so the general WiFi router has a control port "Console", which is used to communicate with Connect a computer or terminal device, and configure the WiFi router through specific software. All WiFi routers are equipped with a console port, which enables users or administrators to use the terminal to communicate with the WiFi router and complete the WiFi router configuration. This port provides an EIA/TIA-232 asynchronous serial interface for local configuration of the WiFi router (first configuration must be done through the console port).
The Console port is directly connected to the serial port of the computer using a dedicated connection for configuration, and a terminal emulation program (such as "Hyper Terminal" under Windows) is used to configure the WiFi router locally. Most of the console ports of WiFi routers are RJ-45 ports.