Link Layer in the TCP/IP Protocol

Question: 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^[1] card across 10BaseT^[2] wires, or from a serial port^[3], through a modem, and across the phone network. Examples of link-layer protocols are FDDI^[4], 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^[5]. Moving data across wide area networks^[6], 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:

1. Physical addressing: Assigning a unique identifier to each device on a network, such as a MAC address.
2. Frame transmission and reception: Encapsulating data into frames and transmitting it over the physical medium, as well as receiving and decoding frames.
3. Error detection and correction: Checking for errors in transmitted frames and correcting them if necessary.
4. Flow control: Regulating the flow of data to prevent overloading of the network.
5. Access control: Allocating the use of the physical medium among multiple devices.
6. Media access control: Implementing the protocol for controlling access to the shared physical medium, such as Ethernet.
7. 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.

[1]Ethernet: A LAN developed by Xerox in 1976. Ethernet became a widely implemented network from which the IEEE 802.3 standard for contention networks was developed. It uses a bus topology and the original Ethernet relies on CSMA/CD to regulate traffic on the main communication line.

[2]10BaseT: A variant of Ethernet which allows stations to be attached via twisted pair cable.

[3]Serial port: A connector on a computer to which you can attach a serial line connected to peripherals which communicate using a serial (bit-stream) protocol.

[4]Fiber Distributed Data Interface (FDDI) : FDDI is a 100 Mbit/s ANSI standard local area network architecture. It is based on optical fibre (though it can be copper cable, in which case it may be called CDDI).

[5] Point-to-point protocol (PPP): A protocol for connecting to the Internet. PPP provides error checking and compression of the IP and TCP headers.

[6] Local Area Network: A collection of computers and other hardware components linked by physical cabling that permits any device on the network to interact with any other device.

[7]Wide Area Network. A network that extends over distances greater than one mile.