Intro to LAN

Local Area Network Topology

  • topology refers to the design of network.
  • over years different topologies are experimented and implemented.

Star Topology.

  • the devices are connected through a central device called switch or hub.
  • this topology is reliable and scalable - despite the cost.
  • Any information sent to a device in this topology is sent via the central device to which it connects.

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Bus Topology

  • This type of connection relies upon a single connection which is known as a backbone cable.
  • if data is transferred simultaneously the network will be slow because of this single connection.
  • easier to implement and cost efficient.
  • difficult to debug.
  • breakage of backbone cable result it failure of the whole network.

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Ring Topology

  • also know as token topology
  • devices are connected to each other. means less cabling is required.
  • data is send to a device through other devices.
  • If the device happens to have data to send, it will send its own data first before sending data from another device.
  • fairly easy to troubleshoot.
  • less prone to bottle neck
  • fault in cut cable result in entire network to break.

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Switch

  • dedicated devices within a network.
  • designed to aggregate multiple devices.
  • various devices are plug into switch’s port.
  • used in larger network such as schools and businesses.
  • Switches can connect a large number of devices by having ports of 4, 8, 16, 24, 32, and 64 for devices.
  • Switches keep track of what device is connected to which port.
  • helps in sending packets to intended packets result in less traffic.

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Router

  • router connects networks and pass data between them.
  • does this by routing.
  • Routing is the label given to the process of data travelling across networks.
  • Routing is useful when devices are connected by many paths, such as in the example diagram below

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Sub netting

  • Sub netting is refers to splitting of network into smaller network within itself.
  • No of hosts that can fit in a network is called subnet mask.
  • A subnet mask is also represented as a number of 4 bytes(32 bits). Ranging from 0-255
  • Subnets use IP addresses in three different ways:
    • Identify the network address
    • Identify the host address
    • Identify the default gateway
  • Host Address: An IP address here is used to identify a device on the subnet.
  • Default Gateway Address: The default gateway address is a special address assigned to a device on the network that is capable of sending information to another network
  • Network Address: This address identifies the start of the actual network and is used to identify a network’s existence.

Subnetting provides a range of benefits such as

  • Efficiency
  • Security
  • Full control

ARP

  • Address resolution protocol
  • technology responsible for allowing devices to identify themselves on a network.
  • ARP protocol allows a device to associate it’s mac address to ip address on the network.

How ARP Works?

  • Each device within a network has a ledger to store information on, which is called a cache.
  • this cache stores the identifiers of other devices on the network.
  • In order to map these two identifiers this ARP send two types of signals:
  1. ARP Request
  2. ARP Replay.

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

DHCP Protocol

Ip address can be assigned manually or automatically using DHCP.

  • DHCP is short for Dynamic Host Control Protocol.
  • If the device has not assigned a manual ip address, it sends out a DHCP discover request to find the DHCP servers on the network.a request is send to get an ip address.
  • DHCP server send back an available ip address (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).