I have taken a course in Coursera to learn the basics of computer networking. I have complete the week 1 assignment which gives a introduction to TCP/IP model and networking devices.
TCP/IP Model
It consists of 5 layers and are Physical layer, Data link layer, Network layer, Transport layer and Application layer. The physical layer deals with the physical device connected to the computer, normally a cable wire which is used to communicate with each other. The data link layer is used to send data between two nodes in a network.
Hubs and Switch
Hubs are used to establish a communication in a Local area network. They receive the data from one node and sends to all node in the LAN. All nodes will receive the data and only the node which is intended to receive the data will accept and other nodes will ignore it. This sometimes results in Collision Domain (When data is sent from multiple nodes, collision of data may occur).
To overcome this, Switch was used. Switch is intelligent device which is used to send the data only for the respective node. Switch uses MAC(Media Access Control) to identify the node which is globally unique address.
Hub is a physical layer device where Switch is a data link layer device.
Unicast, Multicast and Broadcast.
if the LSB(List Significant Bit) of first octet of the destination address is 0, then the ethernet act as Unicast. If the LSB of the first octet of the destination address is 1, then the ethernet act as Multicast. If all the bits are ff, that is ff:ff:ff:ff:ff:ff, the it is Broadcast.
Ethernet
Ethernet is a way of connecting computers in LAN. In order to avoid collision domain, ethernet uses CSMA/CD (Carrier Signal Multiple Access / Collision Detection). This ensure whether the channel is free to send or receive data. Ethernet uses BGP (Border Gateway Protocol) which is used to find the best path between the node. For example, Its likely to a GPS in our mobile which is used to find the best path between two places with respect traffic or other problems.
Ethernet Frame
Normally, all the data in network will be sent as a data packet. A single set of collection of bits is called data packed. In ethernet, it uses ethernet frame to send data. It has few blocks like Preamble, source address, destination address, payload, FCS(Frame Check Sum). FCS is to check whether the data is received without any loss with the help of Cyclic Redundancy .
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