Скачать или смотреть The network layer in the OSI model

Devices Operating at Layer 3:

Routers: Specialized devices that perform routing and forwarding of packets between different networks.
Layer 3 Switches: Combine switching and routing capabilities, offering enhanced performance and flexibility.

Key Functions:

Routing: Determines the optimal path for data packets to traverse across multiple networks to reach their destination.
Addressing: Assigns unique IP addresses to devices, enabling them to be identified and located within the network.
Packet Fragmentation and Reassembly: Breaks down large data packets into smaller units (fragments) for transmission, and reassembles them at the destination to ensure efficient delivery.
Key Protocols:

IP (Internet Protocol): The foundation of internet communication, responsible for addressing and routing packets.
ICMP (Internet Control Message Protocol): Provides error reporting and diagnostic information for IP networks.
IGMP (Internet Group Management Protocol): Manages multicast group membership for efficient delivery of data to multiple recipients.