SYLLABUS
Networking Concepts
o Basic Introduction to Network
o TCP/IP Introduction
o Communication between two systems
o Domain registration, DNS mapping, ISP
o Security
Its really tough to explain the whole networking module in one single post. It is a huge concept and it is divided into layers to simplify our understanding which we will see later.
First we need to start with the basic concepts of networking .
Network is a group of computers or nodes connected by some medium i.e ethernet , wifi or infrared . This group of computer within a network is known as domain and we can share data , exchange files or perform some other activities in this network.
We can further find different types of networks depending upon the number of nodes present on it or the interaction between the nodes.
On the basis of number of nodes in a network , we generally come across three different networks
LAN , MAN and WAN
LAN is a small scale group of nodes which is generally found in colleges or small companies where computers are connected directly with the help of ethernet wire (optical cable ) or wifi .
MAN is a group of nodes in a particular range or space , where computers may or may not be connected directly eg two office buildings connected together .
WAN is used for global prospects i.e when we talk about world wide web . We are basically talking about this kind of network.
On the basis of interaction between the nodes , the network can be divided into intra-network and inter-network .
Intra-network - When two different nodes within the same network interact with each other , then it is known as intra-network, When a person of company A tries to send a file to its colleague working in the same company then both of them uses same network A.
Inter-network - When two nodes from different network interact with each other , we call it as inter-network. Eg . when a person of company A tries to send a file to another person of company B , it uses two different networks i.e . network A and network B . So we call it as inter-network.
Network Topology is the structure of the network i.e. arrangement in which the nodes are connected with each other. Star , Mesh , Bus and ring topology are few examples of network topology.
Networking devices
There are few networking devices which have some specific work to perform while transferring or receiving a message from a node. Here are few networking devices which we use .
Repeaters are used in the physical layer and there work is to increase the signal strength and does not add anything to it. Actually data is transferred in signals which after going to certain distance through the wire looses its strength . Therefore, we use repeater to increase signal strength so that data which we want to send does not get lost somewhere in the cable.
Switch is used to connect two or more networks and helps to control the flow of data in some particular domain . Example - Suppose our switch connects 4 different networks lets say A ,B ,C and D . If I want to send data from network A to D then , switch will help me to broadcast my data only in network D and not in any other networks like B and C.
Hub is used to connect several ethernet(cables) together and make them look like one. While broadcasting some data , unlike switch it transfers data to all the networks that are connected with the help of hub.
Bridge also helps to connect different networks but it brings out some different features. It maintains a table which helps to avoid looping while sending data i.e if our packet of data travels in a network and come across a loop of nodes , it will circulate there only . Thus , prevent the actual receiver to get the message.
Router is a networking device which not only helps to connect two or more network but helps to find the optimal path i.e the shortest path for reaching one node to another. It forms a routing table based on some routing algorithm and it also helps in the packet formation also.
Gateway is used to connect two different networks following similar or different network protocols .
Addresses
In computer networks , we come across three types of addresses .
(i) Logical address / IP address - assigned by the ISP (internet service provider)
(ii) MAC address/Physical address - Network interface card has a unique 48 bit address provided by the manufacturer.
(iii) Service Port Address - each process running on our system is assigned a unique port address which helps to communicate at the process level.
TCP/IP protocol
Prior to this protocol (set of rules) OSI model was passed , which forms the base for all networking protocols. It consist of 7 layers which plays a huge role while transferring data. Below diagrams tells us about the OSI layers.
Lets go into brief detail about each layer of OSI model :
Physical Layer :: ensures a safe and efficient travel of data in the form of bits , consists of electronic circuits for data transmission.
Data Link Layer :: in charge of data encapsulation under the form of frames and their interpretation at the physical level. It is also responsible for hop to hop transmission of data .
Networking Layer :: in this layer , routing algorithm is followed to find the shortest path and is responsible for packet formation and node to node transmission of data.
Transport Layer :: It is responsible for process to process communication with help of service port address , and formation of segments from the message is done.
Session Layer :: it creates a dialog box where the two computer system communicate on some protocol which later helps for efficient data transmission.
Presentation Layer :: determines the format of data transferred to application , data compression / decompression and encryption .
Application Layer :: it deals with the application interface which helps to interact with the user.
After this TCP/IP was introduced which are more reliable and hardware based architecture. It was found more efficient than the OSI model. Below diagram shows different layers of tcp/ip protocol
Network Layer :: has same functionality like physical layer , data link layer and networking layer.
packet formation and ip and physical address mapping is done.
Internet Layer :: Based on internet protocol (ip) which provides the frame for transmitting data from place A to place B
Transport Layer :: mainly depends on two protocol TCP and UDP .
TCP is a connection oriented protocol i.e process to process or end to end connectivity is done using the ip and service port address . Thus forming a logical path between two process also known a virtual circuit or tunnel . Data flows in a stream of packets while using this protocol .
UDP is a connection less protocol i.e no virtual network or tunnel is made prior to data transferring. Unlike to TCP protocol , data are sent in discrete packets and one packet is independent of other packets .
Application Layer :: comprises the work of session , presentation and application layer of the OSI model . HTTP , FTP , SNMP are some protocols of application layer
DOMAIN NAME SERVICE
It is very difficult to remember the ip address of each system connected in a network . So , the best and the easy way to remember them is to name them . eg . www.atos.net , which is nothing but a sub network of .net domain , and a specific name atos is given to it.
IP address and its corresponding names are maintained in the dns server located in various parts of the network . Whenever , we type an URL , then the name is resolved by checking the tables present at the dns server . If the corresponding name is found , it returns the ip address and then it redirects the packets to that specific host.
SECURITY :: cryptography , firewall , antivirus etc are some security methods adopted by the network administrator to provide security .
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