Basic idea of a computer network


What is a Network Switch?

To understand basic networking, you first need to answer the question, “What is
a network switch? “Most business networks today use switches to connect
computers, printers and servers within a building or campus. A switch serves as
a controller, enabling networked devices to talk to each other efficiently.
Through information sharing and resource allocation, switches save businesses
money and increase employee productivity.

What is a Network Switch: Unmanaged Switches?

An unmanaged switch works right out of the box. It’s not designed to be
configured, so you don’t have to worry about installing or setting it up correctly.
Unmanaged switches have less network capacity than managed switches. You’ll
usually find unmanaged switches in home networking equipment.

What is a Network Switch: Managed Switches?

A managed network switch is configurable, offering greater flexibility and capacity than an unmanaged switch. You can monitor and adjust a managed switch locally or remotely, to give you greater network control.

What is a Network Switch versus a Router?

Switches create a network. Routers connect networks. A router links computers to the Internet, so users can share the connection. A router acts as a dispatcher, choosing the best path for information to travel so it’s received quickly.

What is a Network Router?

A networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internet work until it reaches its destination node.

What is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

Why is DHCP?

When a computer uses a static IP address, it means that the computer is manually configured to use a specific IP address. One problem with static assignment, which can result from user error or inattention to detail, occurs when two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.

What is an IP Address?

An IP address is a fascinating product of modern computer technology designed to allow one computer (or other digital device) to communicate with another via the Internet. IP addresses allow the location of literally billions of digital devices that are connected to the Internet to be pinpointed and differentiated from other devices. In the same sense that someone needs your mailing address to send you a letter, a remote computer needs your IP address to communicate with your computer.

An IP address consists of four numbers, each of which contains one to three digits, with a single dot (.) separating each number or set of digits. Each of the four numbers can range from 0 to 255. Here’s an example of what an IP address might look like: 78.125.0.209. This innocuous-looking group of four numbers is the key that empowers you and me to send and retrieve data over our Internet connections.

Dynamic IP Address

Dynamic IP addresses are temporary and are assigned each time a computer accesses the Internet. They are, in effect, borrowed from a pool of IP addresses that are shared among various computers. Since a limited number of static IP addresses are available, many ISPs reserve a portion of their assigned addresses for sharing among their subscribers in this way. This lowers costs and allows them to service far more subscribers than they otherwise could.

Static IP Address

Static IP addresses reveal such information as the continent, country, region, and city in which a computer is located; the ISP (Internet Service Provider) that services that particular computer; and such technical information as the precise latitude and longitude of the country, as well as the locale, of the computer. Many websites provide IP address look-up services to their visitors, free of charge. If you’re curious about your own IP address, you can locate these websites by performing a Google search.

Static IP addresses are generally preferable for such uses as VOIP (Voice over Internet Protocol), online gaming, or any other purpose where users need to make it easy for other computers to locate and connect to them. Easy access can also be facilitated when using a dynamic IP address through the use of a dynamic DNS service, which enables other computers to find you even though you may be using a temporary, one-time IP address. This often entails an extra charge, however, so check with your ISP.

Static IP addresses are considered somewhat less secure than dynamic IP addresses, since they are easier to track for data mining purposes. However, following safe Internet practices can help mitigate this potential problem and keep your computer secure no matter what type of IP address you use.

What is a Firewall?

a firewall is a piece of software. This software monitors the network traffic. A firewall has a set of rules which are applied to each packet. The rules decide if a packet can pass, or whether it is discarded. Usually a firewall is placed between a network that is trusted, and one that is less trusted. When a large network needs to be protected, the firewall software often runs on a computer that does nothing else. A firewall protects one part of the network against unauthorized access.

What is Port Mapping?

In computer networking, port forwarding or port mapping is an application of network address translation (NAT) that redirects a communication request from one address and port number combination to another while the packets are traversing a network gateway, such as a router or firewall.

What is a Port?

A network port is a number that identifies one side of a connection between two computers. Computers use port numbers to determine to which process or application a message should be delivered. As network addresses are like street address, port numbers are like suite or room numbers. Any program may use any port, though some port numbers have a standard use and some programs may be limited in which ports they can use for security reasons. Firewalls often block access to ports based on the network address and port of the source or destination computer, or the program using the port (if the firewall is running on the same computer).

What is a Packet?

A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. When any file (e-mail message, HTML file, Graphics Interchange Format file, Uniform Resource Locator request, and so forth) is sent from one place to another on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file intochunks” of an efficient size for routing. Each of these packets is separately numbered and includes the Internet address of the destination.

The individual packets for a given file may travel different routes through the Internet. When they have all arrived, they are reassembled into the original file (by the TCP layer at the receiving end). A packet consists of control information and user data, which is also known as the payload. Control information provides data for delivering the payload, for example: source and destination network addresses, error detection codes, and sequencing information. Typically, control information is found in packet headers and trailers. “Packet” and “datagram” are similar in meaning. A protocol similar to TCP, the User Datagram Protocol(UDP) uses the term datagram.

What is TCP?

Abbreviation of Transmission Control Protocol, and pronounced as separate letters. TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

What is UDP?

UDP (User Datagram Protocol) is an alternative communications protocol to Transmission Control Protocol (TCP) used primarily for establishing low-latency and loss tolerating connections between applications on the Internet. Both UDP and TCP run on top of the Internet Protocol (IP) and are sometimes referred to as UDP/IP or TCP/IP.

Both protocols send short packets of data, called datagrams. UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact. UDP is an ideal protocol for network applications in which perceived latency is critical such as gaming, voice and video communications, which can suffer some data loss without adversely affecting perceived quality. In some cases, forward error correction techniques are used to improve audio and video quality in spite of some loss.

Basic idea of servers and hosting


How the internet works?

What makes the Internet work at all, is something called the Internet Protocol (IP). You may have heard of the term IP Address. Now you know what the IP stands for, but do you know what it is? A protocol is a set method for a way of doing things. Think of an incoming phone call. Typically it goes like this: you hear the phone ring, you pick up, you say “Hello…” and maybe a little more like, “…this is Guy speaking.” Then the person on the other end acknowledges you with something like, “Hey Guy, this is work. Where the heck are you?” Then the lying, I mean conversation, begins. That’s a socially accepted phone call protocol.

URL and DNS

That’s basically how the Internet works. You tell your computer to connect to a resource, let’s say www.example.com is a human readable form for the IP address 216.92.56.91. Who’s going to remember that?  Exactly.

So we have something called a Universal Resource Locator (URL) like www.example.com Something called a Domain Name Server (DNS) which looks up that URL and then figures out the IP address associated with it. each IP is located inside a block that belongs to ARIN: American Registry for Internet Numbers.

How Data are being sent?

each packet carries the intended IP address, a number to determine where the packet fits back into the data sent, how many packets to expect, as well as your IP address. Crazy huh? It has more than that, but that’s the really important stuff. Now, check this out. Each packet doesn’t necessarily go down the same set of wires to its destination. Those packets go out to a device called a router, which then sends the packet to the nearest available router that is closer to that destination, and, hopefully, isn’t too congested. It figures that out based on the numbers in your IP address.

The first three numbers identify a large area, and the rest make it more specific. Yet again, just like a phone number. This is known as ‘best-effort-delivery’. So one packet may get routed through Virginia and another may go through Vancouver on their way to the same server in Hong Kong. This also means that packet A might get there later than packet B, or not at all! When the packets arrive at the destination, the server or computer receiving it compiles it into something cohesive. Now the computer receiving all the packets sends back a message to the originating computer to say, in effect, “Thanks! Good-bye.” Thus the communication ends.

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