Routers are the primary node devices of the internet. Routers determine data forwarding through routing. The forwarding strategy is called route selection, which is also the origin of the router’s name. The router’s position and role in the network dictate that it must be capable of interconnecting multiple different types of networks. Multiple different networks mean different network links, different network ports, and different network protocols.
1. Address Mapping: This function enables the mapping between network layer addresses and the physical addresses of network devices, such as the mutual mapping between IP addresses and MAC addresses. This is a critical foundation for routers to send protocol packets.
2. Packet Fragmentation and Reassembly: Since routers connect multiple different types of networks, and these different network types have varying MTU specifications, routers need to perform packet fragmentation and reassembly operations.
3. Support for Multiple Routing Protocols: The route selection function is the most fundamental function of a router and the basis for achieving network interconnection. However, because different types of networks may use different routing protocols, routers must have the capability to support multiple routing protocols to ensure the correct routing and forwarding of packets between different networks.
4. Protocol Conversion: This is a function that multi-protocol routers must possess. Routers need to complete the mutual conversion of different network layer protocols, for example, the mutual conversion between IP packets and IPX packets.
5. Routers enable the interconnection of different networks. With the development of networks and the deepening of applications, there is an increasing need to impose certain restrictions on such network interconnection, meaning that routers are expected to achieve network interconnection with a certain degree of isolation capability to enhance network security. Access control technology is a simple and practical network isolation technique. It filters and controls packet forwarding by defining access control lists, allowing only packets permitted in the access control list to be forwarded through the router.
6. Currently, the access control lists used in routers can perform access control on packets based on various methods such as MAC addresses, protocol types, and network addresses to achieve network isolation. Some routers also feature context-aware access control based on packet content, a function similar to that of a firewall.
7. Access control technology achieves network isolation, restricts the mutual access capabilities between interconnected networks, and improves network security鈥攖his is the positive side. However, extensive use of access control lists and firewall technologies can significantly impact the speed and capacity of a router’s packet forwarding.
8. Since routers are typically used for connecting LANs to WANs, routers often become the bottleneck in overall data communication when there is substantial data traffic between LAN and W