Understanding the OSI Model's Layer 3 (Network Layer) and Its Role in IP Addressing

The video explains how the OSI model's Layer 3 (Network Layer) works, in comparison with Layer 2 (Data Link Layer), which uses MAC addresses. Layer 3 relies on IP addresses, a logical addressing system inspired by the postal system, allowing large networks to be segmented into subnets. IP (Internet Protocol), developed by DARPA in the 1970s, is paired with TCP to form the TCP/IP suite. IP addresses are written in dotted-decimal notation (four octets ranging from 0 to 255) and can be assigned manually or via DHCP. Unlike fixed MAC addresses, two devices cannot share the same IP simultaneously. Routers, which connect subnets, use IP addresses to forward packets, which are encapsulated in frames at Layer 2. When a router receives a packet, it removes the frame, analyzes the destination IP address, and re-encapsulates the packet in a new frame for transmission. Upon arrival, the frame is stripped away, and the packet is processed by the upper layers of the OSI model.