The architecture of a router

This article describes the router architecture in detail and describes the router structure. What are its routing protocols and router input ports? The following article will give you a detailed answer.

Router Architecture

From the perspective of architecture, routers can be divided into the first generation single-CPU Single-structure router, the second generation single-bus master-slave CPU Structure router, and the third generation single-bus symmetric multi-CPU Structure router; the fourth generation multi-bus multi-CPU Structure router, the fifth generation shared-memory structure router, the sixth generation cross-Switch Architecture router, and the vro Based on the cluster system.

Router Composition

A vro has four elements: the input port, the output port, the switch, and the route processor.

The input port is the entrance of the physical link and input package. A port is usually provided by a line card. A line card generally supports 4, 8, or 16 ports. An input port has many functions. The first function is to encapsulate and deencapsulate the data link layer. The second function is to find the destination address of the input package in the forwarding table to determine that the destination port is called a route query). Routing Query can be implemented using common hardware, alternatively, you can embed a microprocessor into each line card. Third, in order to provide QoS service quality), the port should divide the received packet into several predefined service levels. Fourth, ports may need to run network-level protocols such as the SLIP Serial Line Internet protocol and the PPP Point-to-Point Protocol) or the PPTP Point-to-Point Tunneling Protocol. Once the route query is complete, you must use the switch to send the packet to its output port. If a router is added to a queue at the input end, several inputs share the same switch. In this way, the last function of the input port is to participate in the arbitration agreement for public resources such as the switch.

The switch can be implemented using different technologies. So far, the most widely used switch technology is bus, cross switch and shared storage. The simplest switch uses a bus to connect all input and output ports. The disadvantage of the bus switch is that its switching capacity is limited by the capacity of the bus and the additional overhead for shared bus arbitration. The crossover switch provides multiple data paths through the switch. A crossover switch with N × N intersections can be considered to have 2N buses. If a crossover is closed, the data on the input bus is available on the output bus; otherwise, the data is unavailable. The scheduler controls the closing and opening of intersections. Therefore, the scheduler limits the switching speed. In the shared Storage Router, the incoming package is stored in the shared storage, and only the packet pointer is exchanged, which improves the switching capacity. However, the switch speed is limited by the storage device access speed. Although the storage capacity can double every 18 months, the storage access time is reduced by only 5% each year, which is an inherent limitation of the shared storage switch.

The output port stores packets before the packets are sent to the output link. complex scheduling algorithms can be implemented to support priorities and other requirements. Like the input port, the output port must also support encapsulation and encapsulation of the data link layer, as well as many advanced protocols.

Router Architecture, Route Processor computing forwarding table to implement the routing protocol, and run the software for configuring and managing the router. At the same time, It also processes packages whose destination addresses are not in the wire adapter forwarding table.