What is OSI Layer 3?

Understanding OSI Layer 3

Network layer. Layer 3 of the OSI model handles routing of data packets between different networks, logical addressing (IP addresses), path determination, and packet forwarding. This layer enables communication across network boundaries and implements logical network topologies. Security at this layer addresses issues like IP spoofing and routing attacks. Network layer security is addressed in standards like NIST SP 800-53, ISO 27001, and various IETF RFCs. Organizations implement Layer 3 security through firewalls, access control lists, IP filtering, secure routing protocols, and network segmentation. For example, an enterprise might implement stateful inspection firewalls at network boundaries with access control lists filtering traffic based on source/destination IP addresses, along with route filtering to prevent bogus routing updates and antispoofing measures to block packets with falsified source addresses. Related terms: IP addressing, Routing, Router, Firewall, Network security, Access control list, Packet filtering, Network segmentation.