What is Ethernet?

Ethernet refers to the local area networks and devices that was defined by the Institute for Electrical and Electronic Engineers (IEEE) under the IEEE 802.3 standard that defines the CSMA / CD protocol.

Ethernet is popular because it allows a good balance between speed, cost and ease of installation.

This is currently used for approximately 85% of LAN-connected PCs and work sites in the world because its protocol has the following characteristics:

  • It is easy to understand, implement, manage, and maintain
  • Allows cheap network implementations
  • Provides extensive topological flexibility for network installation
  • Guarantees successful interconnection and operation of standard-compliant products, regardless of manufacturer

Ethernet architecture:

The elements of an Ethernet network are: the network nodes and the interconnection medium. The network nodes can be classified into two large groups: Data Terminal Equipment (DTE) and Data Communication Equipment (DCE).

DTEs are network devices that generate or are the destination of data: such as PCs, workstations, file servers, print servers; they are all part of the group of end stations

The DCEs are the intermediate network devices that receive and retransmit the frames within the network; can be: routers, switches (switch), hubs, repeaters or communication interfaces, eg: a modem or an interface card

NIC, or Network Interface Card :

Adapter – allows a computer to access a local network. Each card has a unique MAC address that identifies it in the network. A computer connected to a network is called a node.

The Ethernet architecture can be defined as a packet-switched network with multiple access (shared media) and broad broadcast (“Broadcast”), which uses a passive medium and without any central control. Provides error detection, but not correction.

The access to the medium (transmission) is governed from the stations themselves through a statistical arbitration scheme.

The data packets transmitted reach all stations (broad dissemination), with each station responsible for recognizing the address contained in each package and accept those that are addressed to it

Ethernet performs several functions that include datagram packaging and unpacking; handling of the link; coding and decoding of data, and access to the channel.

The link handler is responsible for monitoring the collision mechanism, listening until the transmission medium is free before starting a transmission (only one user uses the transmission every time – baseband-).

The handling of collisions is done by stopping the transmission and waiting a certain time before trying again.

There is a mechanism by which packets are sent at non-standard intervals, which prevents other stations from communicating. This is what is called channel capture.

Ethernet Architecture Functions:

Data encapsulation:

  • Formation of the plot establishing the corresponding delimitation
  • Addressing the source and destination node
  • Error detection in the transmission channel

Link Management

  • Channel assignment
  • Resolution of contention, handling collisions Coding of the data
  • Generation and extraction of the preamble for synchronization purposes
  • Bit coding and decoding

Access to the Canal

  • Transmission / reception of the encoded bits.
  • Carrier sensitivity, indicating traffic on the channel
  • Collision detection, indicating containment on the channel

Frame Format

  • In an ethernet network each element of the system has a unique address of 48 bits, and the information is transmitted serially in groups of bits called frames.
  • Each ethernet interface monitors the transmission medium before a transmission to ensure it is not in use and during transmission to detect any interference.
  • In case of any interference during the transmission, the frames are sent again when the medium is available.
  • The allowed frame size without including the preamble can be from 64 to 1518 octets. Frames outside this range are considered invalid

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