A model that organizes communication functions into seven layers: physical, data link, network, transport, session, presentation and application. It serves as a common vocabulary for thinking about each layer's role separately.
Japanese name: OSI参照モデル
OSI reference model appears in 2 practice questions across 1 topic, including Computer Networking Basics.
Field: Computer Networking Basics
The lowest, layer 1 (physical), sends bits as signals over cables or radio. Layer 2 (data link) delivers frames to a neighboring device within the same network using MAC addresses. Layer 3 (network) uses IP addresses to choose routes across networks and relay packets. Layer 4 (transport) handles communication between applications on end hosts; TCP, for example, controls retransmission and ordering. Layers 5–7 (session, presentation and application) manage the start and end of communication, convert data representations and provide application functions.
The internet actually runs on the TCP/IP protocol suite, whose model has four layers: link, internet, transport and application. Roughly, the link layer corresponds to OSI layers 1–2, the internet layer to layer 3, the transport layer to layer 4 and the application layer to layers 5–7. The OSI protocols themselves never caught on, but the model's layer numbers are still used to say where equipment or functions operate, as in "L2 switch," "L3 switch" or "L7 load balancing."
Each layer uses only the services of the layer directly below and provides services to the layer directly above. On the sending side each layer wraps the data with a header (encapsulation), and the receiving side removes them starting from the bottom. As long as the interfaces between layers are respected, the technology of one layer can be replaced without changing the others. Replacing wired LAN with wireless LAN, for example, leaves IP, TCP and web browsers working unchanged.
Answer: B. Network layer (layer 3)
The OSI reference model organizes communication functions into seven layers, from the physical layer up to the application layer. The network layer (layer 3) uses logical addresses such as IP addresses to choose a route across multiple networks and relay packets to the destination. The data link layer below it only delivers frames to a neighboring device within the same network, using MAC addresses. The transport layer handles communication between applications on the end hosts; TCP, for example, manages retransmission and ordering. In terms of equipment, routers operate at layer 3 and L2 switches at layer 2.
Physical, data link, network, transport, session, presentation and application. Routers work mainly at layer 3, L2 switches at layer 2 and hubs at layer 1.
It is best to know how they map to each other. The protocols actually in use are TCP/IP, but the position of equipment and functions is often expressed with OSI layer numbers, such as "layer 3" or "L7."
The OSI reference model organizes communication functions into seven layers, from the physical layer up to the application layer.
In the OSI reference model, which layer uses logical addres…Mapped onto the OSI reference model, the transport layer corresponds to layer 4 and the internet layer to layer 3.
In the four-layer TCP/IP model, which layer do TCP and UDP …As an Amazon Associate I earn from qualifying purchases.
HTTP (Hypertext Transfer Protocol) DNS (Domain Name System) ARP CIDR CSMA/CA Default gateway DHCP MAC address NAT (Network Address Translation) Port number