Introduction to Networks

Internet uses packet switching technology to move data between two points. On a packet-switched network, files and email messages are broken down into small pieces or packets, that are electronically labeled with their origins, sequences, & destination addresses. Packets travel from one computer to another along the interconnected networks untill they reach their destinations. Each packet can take a different path through the interconnected networks, & the packets may arrive out of order. The destination computer collects the packets & reassembles the original file or email message from the pieces in each packet.
Routers: When an individual packet travels from one network to another, the computers through which the packet travels determine the best possible route for getting the packet to its destination. The computers that decide how best to forward each packet are called routers or gateway computers.  The programs on routers that determine the best possible path on which to send each packet are called routing algorithms.The routing algorithms use the information they have stored in routing tables. This information includes (1)list of connections that lead to particular groups of other routers, (2)rules that specify which connections to use first, & (3)rules for handling instances of heavy packet traffic and network congestion.
Individual networks use a variety of rules and standards for creating packets within their networks. The network devices that transmit packets from one part of a network to another are called hubs, switches, & bridges.

Routers are used to connect one network to another. When packets leave a network to travel on the internet, they must be translated into a standard format, & this translation function is usually made by the routers. When an online company launches its website, it must connect at least one router of internet to the other routers of the company, & that make up the internet access. The following figure shows a router-based internet architecture.
The internet has routers that handle packet traffic along the main connecting points of it. These routers and the telecom lines connecting them are collectively called as the backbone of the internet. These routers are actually very large computers that can each handle more than 50 million packets per second. A router connected to the internet has always more than one path to which it can direct a packet. This multiple packet paths create a degree of redundancy in the internet system that allows it to keep moving packets even if one or more of the routers or connecting lines fail.

Protocols: A protocol is a set of rules for formatting, ordering, & error-checking data sent across a network. Current internet architecture includes (1)the use of a common protocol for all computers connected in the internet, & (2)basic rules for data handling. These data handling rules are: (a) LANs or WANs should not require any internal changes to be connected to the network, (b) data packets that do not arrive at their destinations must be retransmitted from their source network, (c) routers should act as receive-forward devices, & they cannot retain data they handle, & (d) zero global control should exist over the network. Each LAN or WAN can use its own protocols for packet traffic within the private network, but must use a router to transmit packets onto the internet in its standard format.  

TCP/IP: Vinton Cerf & Robert Kahn developed 'Transmission Control Protocol', & 'Internet Protocol', which are the rules that govern internet data handling, & how network connections are established and terminated. The TCP controls the disassembly of a file or message or data into packets before it is transmitted over the internet, & it controls the reassembly of those packets into their original formats when they reach their destinations. The IP specifies the addressing details for each packet, labeling each with the packet's origination and destination addresses. 
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