What is the main functionality of screening routers?

Screening routers primarily serve the function of filtering packets as they pass between networks. This filtering is based on predefined criteria, which typically include aspects like service types and port levels associated with the packets. By examining the header information of incoming and outgoing packets, these routers can decide whether to allow or deny traffic based on security policies established for the network.

The effectiveness of screening routers lies in their ability to enforce access controls and protect internal networks from unauthorized access by examining specific protocols and services. This capability makes them a crucial component in maintaining network security, as they mitigate the risks posed by unwanted or potentially harmful traffic.

Other functionalities such as encryption, higher-level protocol analysis, and creating access points relate to different devices or functions in network architecture. Encryption usually involves dedicated devices like VPN gateways, while analysis of packets from higher protocol layers often pertains to intrusion detection systems or firewalls. The creation of multiple access points is typically a function of network architecture rather than the role of screening routers.