A modem (modulator and demodulator) is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data.
Modems are generally classified by the amount [...]

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Sometimes also referred as Network Information Card, it’s a piece of computer hardware, works at layer 2 of the OSI model, and is designed to allow computers to communicate over a network. In the early days of computer networking, NIC cards relied solely on ethernet cables to connect to another computer on the network. But [...]

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Without the use of a hardware equipment, the existence of a network is unimaginable. In this section we will examine networking hardware devices which are widely used in almost every type of network.
Introduction to networking hardware
On a very high level, there are two types of transmission technology that are in use as of today.

Broadcast based [...]

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EIGRP is a Cisco proprietary routing protocol based on their original IGRP. EIGRP is a distance vector routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and processing power in the router.
Some of the routing optimizations are based on the Diffusing Update Algorithm [...]

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Interior Gateway Routing Protocol (IGRP) is a proprietary distance-vector routing protocol invented by Cisco, used by routers to exchange routing data within an autonomous system.
IGRP was created in part to overcome the limitations of RIP (maximum hop count, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each route, [...]

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It is one of the core routing protocols in the Internet and works by maintaining a table of IP networks or ‘prefixes’ which designate network reachability between autonomous systems (AS). It is described as a path vector protocol. BGP does not use technical metrics, but makes routing decisions based on network policies or rules. The [...]

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OSPF (Open Shortest Path First) is a link state Interior Gateway Routing protocol (IGRP). It uses cost as its routing metric.
Some of the features of OSPF are:-

Support for MD5 based authentication
Support for VLSM – Variable Length Subnet Mask (classless routing)
Tagging of routes

OSPF based network can contain multiple smaller networks. OSPF uses both unicast and multicast [...]

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RIP is one of the most commonly used routing protocol. It is a type of Interior Gateway Protocol used to dynamically adapting to changes on the network and communicating information about the other routers which can be reached by each router.
RIP is a distance-vector routing protocol employing the hop count as a routing metric. The [...]

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A routing protocol is used on a router and allows different computer networks to communicate.
Some of the most popular and commonly used routing protocols are:-

Open Shortest Path First (OSPF)
Routing Information Protocol (RIP)
Interior Gateway Routing Protocol (IGRP)
Enhanced Interior Gateway Routing Protocol (EIGRP)
Border Gateway Protocol (BGP)

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The primary function of DNS is to resolve hostname to IP address. These hostname must be a part of a FQDN (Fully Qualified Domain Name). Example of FQDN are www.google.com, www.microsoft.com, news.google.com, mail.google.com where news and mail might refer to hosts that are a part of google.com domain.
The information about hostname and domains are stored [...]

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