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Local Area Network (LAN)

What is LAN?

LAN stands for “Local Area Network” is a network that is contains within a limited area, such as a single building (school, residence, laboratory, college, university campus, office). Every computer connected to the network (via LAN) is said to be “on the network”. The technical term for a computer that’s on the network is a node. Local Area Network has the two most common technologies such that Ethernet and Wi-Fi.

Types of LAN

There are two types of LAN such that client/server LAN and peer-to-peer LAN. A client/server LAN consists of several devices (the clients) connected to a central server. The server manages file storage, application access, device access, and network traffic. A peer-to-peer LAN doesn't have a central server and cannot handle heavy workloads like a client/server LAN can, and so they're typically smaller. On a peer-to-peer LAN, each device shares equally in the functioning of the network. The devices share resources and data through wired or wireless connections to a switch or router. Most home networks are peer-to-peer.

What is Ethernet?

Ethernet is the most common type of computer network used in local area network (LAN), a wide area network (WAN), and a metropolitan area network (MAN). Therefore the Ethernet has a standard packet format that all packets sent on an Ethernet network must follow. An Ethernet packet contains the following information.

Ethernet Packet Information

  • Preamble: The preamble consists of 56 bits of alternating ones and zeros and is use to synchronize the precise timing required to read packet data.
  • Start-of-frame marker: A start-of-frame marker is a single byte that indicates that the frame is about to begin.
  • Destination MAC address (six bytes).
  • Sender MAC address (six bytes).
  • Tag: The tag, which is use to support virtual local area networks (VLANs), is optional. Therefore a VLAN lets you divide two or more distinct LANs on a shared physical infrastructure.
  • Ethertype (two bytes): This field indicates the specific protocol that is contains in the payload.
  • Payload: The payload contains the actual data being sent by the packet. The payload can be anywhere from 46 to 1,500 bytes. If the information that needs to be sent is longer than 1,500 bytes, the information must be broken into two or more packets, sent separately, and then reassembled when the packets reach their destination. Therefore the tasks of breaking up and reassembling the data are handle by protocols at higher layers in the OSI framework. Ethernet itself has no understanding of what is in the packets it sends.
  • Frame check sequence (four bytes): The frame check sequence (FCS) is used to ensure that the frame data was sent correctly. Basically, the interface that sends the packet uses an algorithm to calculate a four-byte number based on the contents of the frame and saves this number in the FCS field. When the packet is receive, the receiving interface repeats the calculation, and then makes sure that the number recorded in the FCS portion of the packet matches the number it calculated. If the numbers disagree, the packet got garble in transmission and is discards.

What is Wi-Fi?

A Wi-Fi is stands for “Wireless Fidelity” is a common name for wireless networking technology. Wi-Fi Access Point that works with most 802.11 Wi-Fi standards and protocols, including 802.11ac. They are commonly used for local area network of devices and Internet access.

Also learn about IP Routing

 

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