What is router architecture?

A router is a network device that forwards data packets between computer networks. Router architecture is designed to perform two essential functions: processing routable protocols and using routing protocols to determine the optimal path for data transmission.

Architecture of Router

A router consists of four fundamental components that work together to enable efficient packet forwarding and routing decisions.

Input Port

The input port performs multiple critical functions in packet processing. It handles physical layer functionality by terminating incoming physical links and manages data link layer operations to interoperate with the other side of the link. Most importantly, it performs lookup and forwarding functions to determine the appropriate output port for each incoming datagram.

Output Port

Output ports store packets received from the switching fabric and transmit them on outgoing links. They perform the reverse operations of input ports, handling both link-layer and physical-layer functions to ensure proper packet transmission to the next network node.

Switching Fabric

The switching fabric is a combination of hardware and software that moves incoming data to the correct output port. It acts as the internal highway of the router, connecting input ports to output ports based on forwarding decisions made by the input ports.

Routing Processor

The routing processor executes routing protocols, maintains routing information and forwarding tables, and performs network management functions. It operates on a slower timescale (milliseconds to seconds) compared to the data plane components and is implemented in software.

Components of Router

Internal Components

• Read-only memory (ROM) − Stores the router's bootstrap details and basic startup instructions.

• Flash memory − Holds the operating system images and can be electrically erased and reprogrammed.

• Random-access memory (RAM) − Stores routing tables, ARP cache, and buffered data during operation.

• Nonvolatile random-access memory (NVRAM) − Stores the router's startup configuration files that persist after power cycles.

• Network interfaces − Physical connections that link the router to different networks.

External Components

• Virtual terminals − Provide remote access capabilities for router configuration and management.

• Network management stations − External systems used for monitoring and managing router performance.

Data Plane vs Control Plane

Conclusion

Router architecture separates packet forwarding (data plane) from routing control (control plane) to achieve high-performance packet processing. The combination of specialized hardware components and intelligent software enables routers to efficiently direct network traffic along optimal paths.