Middle
Rääkige TCP/IP mudeli sidemekihist (Link Layer).
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Link Layer, also known as the network access layer, is responsible for data transfer between neighboring nodes in a network. It ensures reliable frame transmission over a local communication channel.
Main functions of the link layer:
- Data framing: Converting network layer packets into frames, adding headers and trailers necessary for transmission over the physical channel.
- Media access control (MAC): Defining rules for access to shared transmission media, if used by multiple devices (e.g., Ethernet). It prevents collisions.
- Error detection and correction: Adding checksums (e.g., CRC) to detect data damage during transmission. Some link layer protocols may also perform error correction.
- Physical addressing: Using MAC addresses for unique device identification within a local network.
- Flow control: Regulating data transfer speed between neighboring nodes to prevent sender overload.
Examples of link layer protocols:
- Ethernet: The most common protocol for wired LANs.
- Wi-Fi (IEEE 802.11): Protocol for wireless local area networks.
- PPP (Point-to-Point Protocol): Used to establish a direct connection between two nodes (e.g., via modem).
- ATM (Asynchronous Transfer Mode): Protocol using fixed-size cells, popular in telecommunications.
- Frame Relay: Protocol with variable packet length, used in WAN networks.
Differences from other layers:
- From the physical layer: The link layer works with frames and provides logical link between nodes, while the physical layer transmits bits over the physical medium.
- From the network layer: The network layer (IP) handles routing packets between networks using IP addresses. The link layer transmits frames only within a single local network segment, using MAC addresses.