Intro To LAN and Protocols

Local Area Network i.e. LAN refers to a network of interconnected computers and devices within a limited area, such as a home, office, or campus. Devices in a LAN can communicate with each other directly. There are various protocols associated with it that we will be studying in this lab.

Lab Objectives:-

• Introduction to LAN Topologies.
• Networking Devices Used in Topologies.
• Subnetting
• Address Resolution Protocol(ARP)
• Dynamic Host Configuration Protocol(DHCP)

Introduction To LAN Topologies

Topologies refer to devices' physical or logical layouts and how they are interconnected. Every Topology has its Advantages and Disadvantages.

There are various topologies which are listed below:

1. Star Topology
2. Bus Topology
3. Ring Topology
4. Mesh Topology
5. Tree Topology
6. Hybrid Topology

i) Star Topology

In Star Topology the devices are individually connected via a central networking device such as a switch or hub. This topology is the most commonly used because of its reliability and scalability. Any packet sent to a device in this topology is sent via the central device i.e. switch or hub

Star Topology has a major drawback if the central device fails due to hardware or any other unexpected issue the whole network will stop working.

ii) Bus Topology

Bus Topology relies upon a single connection which is known as a backbone cable. All the other devices are connected to this single connection. This type of topology is similar to the leaves(devices) on the branches(backbone) of the tree. As all the data is sent from a single connection it is prone to get slow or bottlenecked if the devices within the network are sending requests simultaneously

iii)Ring Topology

The ring topology (also known as token topology) boasts some similarities. Devices such as computers are connected directly to each other to form a loop, meaning that there is little cabling required and less dependence on dedicated hardware such as within a star topology. A ring topology works by sending data across the loop until it reaches the destined device, using other devices along the loop to forward the data. But if this loop is broken down due to any failure like a wire cut or device failure the entire network will break.

Other than this there are many more topologies which you can learn about.

Networking Devices Used in Topologies:

Network Switch:

A network switch is a smart device that connects various computers, printers, and other devices within a network. Unlike its predecessor, the hub, a switch operates with a higher level of intelligence. It functions as a bridge, directing data traffic only to the specific devices that need it, which increases the efficiency of the network. Switches can connect a large number of devices by having ports of 4, 8, 16, 24, 32, and 64 for devices to plug into

Router:

Routers are used to connect multiple networks it involves creating a path between networks so that this data can be successfully delivered it routes data across different paths (hence the name router!)

Subnetting:

Subnetting refers to the splitting of the network into smaller parts to maintain efficiency, security, and Full control of the network. Take a College network, for example, a college has multiple departments like finance, Accounting, etc which need to be categorized so the Network administrators use subnetting to categorize and assign specific parts of a network to reflect this. Subnetting is achieved by splitting up the number of hosts that can fit within the network, represented by a number called a subnet mask

Subnets use IP addresses in three different ways:

• Identify the network address
• Identify the host address
• Identify the default gateway

A Network Address is used to identify a network's existence and start of the network For example, a device with the IP Address 192.168.29.31 has a network address 192.168.29.0

A Host Address is used to identify a device in a network or subnet For Example, a device will have the network address 192.168.29.31

A Default Gateway is an address assigned to a device on the network i.e. capable of sending data to another network For Example 192.168.29.254

Address Resolution Protocol(ARP):

The ARP protocol allows a device to associate its MAC address with an IP address on the network. Each device on a network will keep a log of the MAC addresses associated with other devices. When devices wish to communicate with one another, they will send a broadcast to the entire network searching for the specific device. Devices can use the ARP protocol to find the MAC address (and therefore the physical identifier) of a device for communication.

To map these two identifiers together (IP address and MAC address), the ARP protocol sends two types of messages:

1. ARP Request
2. ARP Reply

When an ARP request is sent, a message is broadcasted to every other device found on a network by the device, asking whether or not the device's MAC address matches the requested IP address. If the device does have the requested IP address, an ARP reply is returned to the initial device to acknowledge this. The initial device will now remember this and store it within its cache (an ARP entry).

Dynamic Host Configuration Protocol(DHCP):

IP address can be assigned to devices in a network in two different ways i.e. either manually or automatically with the help of DHCP Server. When a device connects to a network, if it has not already been manually assigned an IP address, it sends out a request (DHCP Discover) to see if any DHCP servers are on the network. The DHCP server then replies with an IP address the device could use (DHCP Offer). The device then sends a reply confirming it wants the offered IP Address (DHCP Request), and then lastly, the DHCP server sends a reply acknowledging this has been completed, and the device can start using the IP Address (DHCP ACK)

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