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.[1]

Functions

The network layer provides the means of transferring variable-length network packets from a source to a destination host via one or more networks. Within the service layering semantics of the OSI network architecture, the network layer responds to service requests from the transport layer and issues service requests to the data link layer.

Functions of the network layer include:

Connectionless communication
For example, IP is connectionless, in that a data packet can travel from a sender to a recipient without the recipient having to send an acknowledgement. Connection-oriented protocols exist at other, higher layers of the OSI model.
Host addressing
Every host in the network must have a unique address that determines where it is. This address is normally assigned from a hierarchical system. For example, you can be :
"Fred Murphy" to people in your house,
"Fred Murphy, 1 Main Street" to Dubliners,
"Fred Murphy, 1 Main Street, Dublin" to people in Ireland,
"Fred Murphy, 1 Main Street, Dublin, Ireland" to people anywhere in the world.
On the Internet, addresses are known as IP addresses(Internet Protocol).
Message forwarding
Since many networks are partitioned into subnetworks and connect to other networks for wide-area communications, networks use specialized hosts, called gateways or routers, to forward packets between networks.
Other Languages
العربية: طبقة الشبكة
català: Capa de xarxa
čeština: Síťová vrstva
español: Capa de red
euskara: Sare geruza
فارسی: لایه شبکه
français: Couche réseau
हिन्दी: लेयर 3
Bahasa Indonesia: Lapisan jaringan
italiano: Livello di rete
latviešu: Tīkla slānis
Bahasa Melayu: Lapisan rangkaian
монгол: Network layer
Nederlands: Netwerklaag
norsk nynorsk: Nettverkslaget
português: Camada de rede
slovenčina: Sieťová vrstva
slovenščina: Omrežna plast
српски / srpski: Слој мреже
srpskohrvatski / српскохрватски: Sloj mreže
Türkçe: Ağ katmanı
українська: Мережевий рівень
Tiếng Việt: Tầng mạng
吴语: 网络层
中文: 网络层