What are the responsibilities of the link layer in the TCP/IP protocol?
The link layer is responsible for establishing communication between machines at the level of a physical connection.
For example, the link-layer protocols move data from an ethernet
card across 10BaseT
wires, or from a serial port
, through a modem, and across the phone network. Examples of link-layer protocols are FDDI
, which is used for fiber optics networks; the familiar ethernet protocol; and PPP
, which is used across phone lines and other types of point-to-point connections. Link-layer protocols are typically concerned only with the local network
. Moving data across wide area networks
, or between different types of physical networks, requires the capabilities of the network layer.
The link layer in the TCP/IP protocol suite is responsible for the following tasks:
- Physical addressing: Assigning a unique identifier to each device on a network, such as a MAC address.
- Frame transmission and reception: Encapsulating data into frames and transmitting it over the physical medium, as well as receiving and decoding frames.
- Error detection and correction: Checking for errors in transmitted frames and correcting them if necessary.
- Flow control: Regulating the flow of data to prevent overloading of the network.
- Access control: Allocating the use of the physical medium among multiple devices.
- Media access control: Implementing the protocol for controlling access to the shared physical medium, such as Ethernet.
- Link-layer switching: Forwarding frames based on the physical address, allowing for communication between devices on different segments of the network.
The link layer is the second layer in the OSI (Open Systems Interconnection) model, and it operates below the network layer.