Ethernet in Networking and Ethernet frame

Ethernet

Ethernet is a part of the Local Area Networks (LAN) products and works as per the specifications of IEEE 802.3

standards. It is responsible for transmitting the data from one network to the other. The most commonly used Ethernet types is the Fast Ethernet (100 Mbps) and Gigabit Ethernet (1000 Mbps).

Full and Half Duplex Ethernet

In Half Duplex Ethernet, only one wire is used to connect the networks and transmit the data. Sometimes, if the transmission rate in the Half Duplex Ethernet in a 10BaseT network is around 30 to 40 percent, which is around 3 to 4 Mbps, collision may occur if the client and the server transmit data at the same time. So, to avoid collision, half duplex Ethernet uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.

In Full Duplex Ethernet, two wires are used for communication between the networks. In Full Duplex Ethernet, individual wires are dedicated for transmitting and receiving data. In full duplex, CSMA/CD protocol is not required as there is no threat of collision. This also allows 100 percent transmission rate and hence the overall transmission rate is 200 Mbps for a Fast Ethernet.

Data link layer for Ethernet

Ethernet in the data link layer is responsible for assigning physical source and destination address to the frames. In addition, it is also responsible for converting the packets into frames and transmitting to the Network Layer.

Ethernet Addressing

Ethernet addresses are the physical addresses of the devices in a LAN. Every LAN card is identified as a Unicast Ethernet address. The LAN addresses are as per the IEEE standards. The IEEE 802.3 MAC protocol characterizes the addressing details. The length of each LAN address is 6 bytes and a valid Ethernet address is written with periods separating each set of four hex digits, for example, 0047:5e7f:9236. To every organization who manufactures the LAN card, IEEE assigns a distinctive organization uniquely identifier (OUI).

Ethernet Frames

Frames are used by the Data Link layer to transfer the packets of data from the Network layer. These are made at the Data Link layer. Frames perform a data security check and ensure that the data is not corrupted.

Figure shows the Ethernet Frame format.

Preamble - Revived the information that a packet is synchronized and frame will be sent.

Destination Address - Defines the destination address of the device.

Source address - This is the address of the source device from where the frame was dispatched.  If the Frame is not delivered at the destination, the network will inform the sender and will try again to send the frame.

Type or Length - Identifies the type of protocol used.
Data- The implies the size of packet sent from the network layer to the data link layer. 

Frame Check Sequence - It performs the cycle redundancy check, which guarantees that the frame received is without any errors.