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  Layer 3 Network Layer


IPv4/v6; RIP; QoS

The network layer (also packet level) provides a defined benefit services for switching connections and packet-oriented services for the relaying of data packets. The data transmission in both cases will go over the entire communication network and includes the route search (routing) between the network nodes. Because not always a direct communication between the sender and the target is possible, packets must be forwarded by nodes that are on the way. Next mediated packets do not reach the higher layers, but are provided with a new intermediate target and sent to the next node.

The main tasks of the network layer is one of providing cross-network addresses, the routing and the construction and updating of routing tables and the fragmentation of data packets. But the negotiation and ensure a certain quality of service falls within the remit of the network layer.

OSI Layer 3 - Network Layer

In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers, since it knows the address of neighboring network nodes, and it also manages quality of service (QoS), and recognizes and forwards local host domain messages to the Transport layer (layer 4). The data link layer (layer 2) is responsible for media access control, flow control and error checking.

The network layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host via one or more networks, while maintaining the quality of service functions.



  • Connection model
  • Host addressing
  • Message forwarding

Popular Network Layer Protocols

DDPDatagram Delivery Protocol
DVMRPDistance Vector Multicast Routing Protocol
ICMPInternet Control Message Protocol
IGMPInternet Group Management Protocol
IPsecInternet Protocol Security
IPv4/IPv6Internet Protocol
IPXInternetwork Packet Exchange
PIM-DMProtocol Independent Multicast Dense Mode
PIM-SMProtocol Independent Multicast Sparse Mode
RSMLTRouting Information Protocol
Shortest Path Bridging