FIREWALL

Firewall :- Firewall is a network device which controls the incoming and outgoing network traffic based on a applied set of rules. Basically this device is used for authentication purpose, also firewall is just like a barrier used in network. Firewall has two properties I mean we have two conditions in firewall one is Denied and another one is Permit and we can only put one condition in action in a network.

Now as you can see in the diagram there is a device between My computer and Computer A and Computer B. So if Computer A and B want to communicate with My computer they have to get authenticated after that they can communicate with My computer otherwise they are not Permitted to connect to My computer. But in case of Computer C there are no any firewall device used between My computer and Computer C so they can connect and communicate between each other without any authentication. Now I think I have clear myself about firewall. Firewall can hardware as well as a software also.
PIX and ASA are the examples of firewall hardware devices.
First Generation
Packet filter :- Firewall technology was first introduce by engineers of  Digital Equipment Corporation in 1988, They developed filter system known as Packet filter firewall.This system was the first generation and now this system is known as technical Internet security. After that AT & T, Bell Labs were continuing their research in packet filtering and developed their own model.
Second Generation
Stateful filters:- Three colleagues were introduce second gen generation of firewall known as Circuit level gateways. Second generation firewall were almost same as first generation firewalls but they work on layer 4 of the OSI model.
Third Generation
Application Layer:- Application firewall is invented by Wie Xu and Peter churchyard and that was also known as Firewall tool kit.
 

ROUTER

Router :- It is layer 3 device of OSI reference model. Router is used to connect or communicate two or more than two different network each other. Router is also responsible for path selection of data to be travel from source to destination without any kind of trouble. Basically routers work on IP addresses. A router never broadcast at all.

 Router are basically of two types
1) Modular:- These router are dynamic in nature. We can change individual port of dynamic router.
2) Non Modular :- These routers are static in nature and we can not change the port of the router. If any of the port is faulty then we must have to change the whole internal part of the router.

According to functionality routers are of three types:-
1) Core Router :- These are the router which became main backbone of the internet. This router must be able to support multiple telecommunication interfaces of highest speed of the internet. And also must be able to forward IP packets are very high speed.
2) Distributed Router :- These Routers distribute the internet. Means these are the routers which are used by the IPs and X-changes to distribute internet connection all over the world.
3) Access Router :- These Routers are for general public, every normal user access the internet from access router. These Routers are basically used in small organizations and homes. These Routers have less functionality then Distributed router and Core router.

SERIES OF ROUTERS
600, 700, 800, 1200, 1400, 1500, 1700, 1800, 1900, 2100, 2300, 2400, 2500, 2600, 2800, 2900, 3200, 3600, 3700, 4100, 4200, 7100, 7200, 7300, 7400, 7500, 7600, 10000, 12000.
From 600 to 2500 series of Routers these all are outdated. From 2600 to 3700 these Routers are Access Routers. From 4100 to 7400 these Routers are known as Distributed Router, 7500 to 12000 these routers are known as Core Routers. From 2600 to 12000 all series of Routers are also known as Modular Routers rest of the routers are Non Modular Routers accept 1800 and 1900.

FUNDAMENTALS OF ROUTER
1) PANEL :- Routers have two panels front and back panel.
Front :- It has only information about the Router's series.
Back :- All ports of the routers are present at the back panel, power supply too.
2) PORT
LAN PORTS :- Ethernet  10 Mbps speed
Fastethernet  100 Mbps speed , Gigaethernet 1000 Mbps speed, 10-Bt  10 base twisted pair cable, AUI 10 Mbps, DB- 15 port.
WAN PORT :- BRI ports and Serial ports. BRI ports are outdated means not in use now a days. So we should only talk about Serial Ports.
Serial ports have some sub parts like Simple serial 60 pins, WIC IT, NM 4 AS, NM 8AS.
Smart Serial have 13 pins, WIC 2T, WIC 3T, WIC 4T.
CONFIGURATION PORTS :- Consol and AUX ports are the ports using for configuration. AUX port is for telephone. Consol port is used for RJ45 connector's devices.
The combination of LAN ports and WAN ports are known as line.
MEMORY IN ROUTER
1) ROM :- Responsible for POST, mini IOS is here in RAM, compression of IOS is known as mini IOS.
2) RAM :- It is used to store the current configurations.
3) FLASH :- After the decompression the IOS is stored in flash memory.
4) NV RAM :- Where we can store our configuration files is known as NVRAM.
There are two types of IOS are in Router.
CISCO IOS :- this is internetwork O.S based on command line interface.
YATA :- this one is Graphical User Interface based.  

SWITCH

SWITCH :- A network switch is used to connect devices together in a computer network. It increase the number of devices within a network. Maximum ports on a switch could be 128. It is a layer 2 device of OSI reference model, also it is a LAN device, It works on MAC addresses. The internal circuit of the switch is like star topology. Port number start from f0/0 to f0/128.

BRIDGE :- It was layer 2 device also. It joint different network. It was only used in LAN level Organization. This was work on MAC addresses, there were 2 collision domain in Bridge. This device is not in use, this is outdated.

FRAME RELAY :- It is a special kind of switch neither work on IP addresses nor on MAC addresses. It works on virtual links. 

HUB

HUB :- Short name of Hirarical Universal Bus, it works on Physical layer of the OSI model. Basically it is a half duplex device, also some time this device is called duffer device because it doesn't have any memory for storage. It also works like repeater. Hub always does broadcasting only, This is the reason, why it has been stoped using now a days.

There is one collision domain in Hubs.

Hubs are replaced by switches. 

Hub have three major types 

1) Active Hub :- having power supply

2)  Passive Hub :- No power supply

3) Intelligent Hub :- Bother the hubs used in this type.

(Collision Domain:- Maximum numbers of devices which can send data without collision simultaneously. 

Amplifier:- It increase the strength of any network. But it doesn't remove the noise that's why it has been stop using. 

Repeater :- This device is used to regenerate the weak and end aged signals, nor it make any noise neither remove the existed noise from the actual signal.    

DEVICES IN NETWORKING , NIC CARD

NIC CARD :- Short name of Network Interface Controller is also known as Network Interface Card,Network adapter, LAN adapter and Physical Network Interface. It is a networking device which connect our computer with the computer network.

As the image tells us that there are three types of NIC Card USB NIC card, Wireless NIC card and old and normal NIC card. At NIC card there is BNC port, RJ45, SC-ST (Suscriber chanel- Straight tip) and a Antina 

STRAIGHT CABLE & CROSS CABLE

Straight Cable :- This cable is use to connect and communicate different addressing system devices.
Like :-
Switch                        to            PC
Modem, Router          to            PC
Hub                            to            PC
Modem, Router          to            Hub
These cables are designed and identify by their colour coding, so lets see the colour coding of straight cable below
White Orange                             White Orange
Orange                                        Orange
White Green                               White Green
Blue                                            Blue
White Blue                                 White Blue
Green                                          Green
White Brown                              White Brown
Brown                                         Brown

Cross cable:- This cable is used to communicate and connect same addressing system devices.
Like :-
PC                           to              PC
Modem, Router       to             PC
Hub                         to             Hub
Switch                     to             Switch
Modem                    to             Router

Now colour coding of cross cable is given below
White Orange                           Orange
Orange                                      White Orange
White Green                             Green
Blue                                          Blue
White Blue                               White Blue
Green                                        White Green
White Brown                            White Brown
Brown                                       Brown

This was all about cables or we can also say communicating medium. 

TWISTED PAIR CABLE

Twisted pair cable is a type of cable  that consist of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction from external sources. There are  four pairs of wire are in a cable. This cable is invented by Alexander Graham Bell.

TYPES OF TWISTED PAIR CABLE

      Shielded Twisted Pair Cable :- As the name tells us that this is shielded means covered. Each pair of cable is covered by an additional copper braid jacket or foil wrapping. This shielding helps to protect the signals on the cable from external interference. This was used in IBM token ring networks. But this cable is expensive then Unsheilded Twisted Pair.

Speed of this cable is 1000 or 1GBps.

UNSHIELDED TWISTED PAIR CABLE:- This cable is used in many Ethernet network and in 

telephone systems. some subtypes of the cables is given below:-

Cat 1                2-4 Mbps speed

Cat 2                6-8 Mbps speed

Cat 3                10-20 Mbps speed    ETHERNET CABLES 

Cat 4                40-60 Mbps speed 

Cat 5                100 Mbps speed        FASTETHERNET CABLES 

Cat 5 e             150 Mhz speed          GIGAETHERNET CABLES

Cat 6                1000 Mbps speed                            

FIBER OPTICS CABLE

FIBER OPTIC CABLE

In Fiber Optics a technology that uses glass or plastic threads (Fiber) to transmit data. A Fiber cable consist of a bundle of glass threads, each of them is capable of transmitting messages modulates onto light waves.

As shown in the pencil diagram the cable is protected by the outer jacket it protect cable from outer problems. Coating is here to protect the core part of the cable, the core is responsible to data transfer

and receive. The data exchange is done by light in this cable.                                                               

This cable has much greater bandwidth as compare to metal cables, also carry more data then metal cable, much thinner and lighter. Data can be transmitted digitally in this cable                                    

The main disadvantage of fiber optic cable is that cable are expensive to install. In addition they are more fragile then wire and are difficult to splice.                                                                                  

                                                                                                                                            

COAXIAL CABLE

There are many cables used in any network for communication. First of all we will take a look at Coaxial cable.
Coaxial cable is a kind of copper cable used by the cable TV companies between the community antina and user's home. This cable was invented in 1880 and invented by Oliver Heaviside.

As you can see in the diagram the cable is protected by Plastic jacket. Also Dielectric insulator is used here for protecting the inner interference and the electric signals travel through the central core, means the data is exchanged by the central core.

Coaxial Cable is of Two Types
Thin Net Coaxial Cable & Thick Net Coaxial Cable 

Thin Net Coaxial Cable :- The copper wire is Thin as the name says and the wire has less diameter. The range of this wire is 185 Meter, 10 base 2 , means 200 meter long and have 10 Mbps speed.

Thick Net Coaxial Cable:- This wire is Thick and having more diameter then upper discussed cable. This cable is known as 10 base 5 cable ( 500 meter long and 10 Mbps speed) 

HYBRID TOPOLOGY

Hybrid Topology:- The Hybrid topology is nothing it is the combination of two or more topology.

This is the mixture of two topology.

MESH TOPOLOGY

MESH TOPOLOGY                                                                                                                                

Mesh Topology:- As the diagram shows every node is connected to each other and the cable use to connect these nodes is Twisted pair cable. Communication can be slow in this kind of topology, because no such device or technology is used in this network so that can manage the communication channel. According to the design of this topology we can say this is expensive. 

STAR TOPOLOGY

Star topology :- A star topology is designed with each node directly connected to the central device that can be a Switch or could a Hub.

This topology is very easy to install as you can see in the diagram, also easy to detect fault.      

This kind network topology require more wire then Bus topology.                                              

Here is a drawback of this topology is that if the central device stop working by any reason     

than the whole network will stop. This network topology is more expensive than Bus topology.

RING TOPOLOGY

RING TOPOLOGY :- This topology is like ring like design,

In this topology communication takes place through token ring. The token ring can be clock wise or anticlockwise. In this topology we use two token ring primary and secondary, one will be clockwise and other will be anticlockwise. The connecting medium is used here twisted pair cable. 

NETWORK TOPOLOGIES

Topologies means any kind of designs that how we made our design understandable to the user or the people who want to understand our design of anything. Same thing is happening here in the IT world, there are many kind of network topologies.

    BUS TOPOLOGY :-

TERMINATOR:- In bus network topology terminator are used to absorb the signals.

BNC:- Bayonet Neill–Concelman, this connector is used to quick connect or disconnect radio frequency in coaxial cable. 

BACKBONE CABLE:- The central cable is called the backbone cable. 

This topology is very easy to install and also easy for foult finding. If the backbone cable get breaked than whole the network will stop. This is the main disadvantage of this network. 

                  

NETWORK TYPE

I have already told you about network and networking. So now today we are going to understand the different types of Network. 

 

LAN :-  LAN is the short form of Local Area Network. It is a network in which distance matter a lot. In a small organization LAN network is used. As the name says local area network means the network is only used locally. 

There are further many types of LAN 

PAN:- Personal Area Network this network is so much limited its area is only 1 meter to 3 meter. This kind of networks are only used at homes most of the time. 

SAN:- Storage Area Network, Any work performance by the user is stored in the backend is called storage area network. 

WLAN:- Wi-Fi LAN this is a wi-fi and its range is about 50-60 meters usually. 

CAN:- Campus Area Network. This kind of network is used in collages and university campus. 

MAN:- Metropolitan Area Network. This kind of network covered a city, mean the distance of this network is larger than other. Examples of this network is wi-max, cable TV and Bangalore city.

  

WAN :- Wide Area Network, as the name itself says that this network cover all over the world.  

LAN is further divide into two types 

WORKGROUP :- In it connection is point-point and no centralized control is present. 

DOMAIN:- In this kind of network communication takes place by the centralized control, means there are server and client technology used. 

Connection Medium

Medium is any thing that is used to connect two or more devices each other, that can be wired or wireless.
WIRED & WIRELESS MEDIUM :-
Wired medium is secured, faster and also costly than wireless medium. Range of wired medium is more than wireless because wireless devices has limitation of range but wired medium can be spread as our own choice as I mentioned above wired medium is costly this one is also a big reason of to be costly.

the upper on is WIRED and lower one is WIRELESS

I hope  I have make clear myself about wired and wireless mediums.  

How to check your service tag and serial number of your computer without entering into BIOS.

Check this Out...

What is Internet ?

Hello everyone ! In the previous post I have already told you about Computer Networking.
I hope you all enjoy that and learn that. Now today I am going to tell you about Internet.
Internet is the network of networks, means all the networks of the whole world are indirectly or directly connected each other that's exactly called Internet.

 I hope its clear now with the help of this image.

INTERANET :- A network with in an organization or within a company is called the Intranet.
EXTRANET :- A network with in two or more organization is called Extranet.

NETWORKING CONCEPT

Hello everyone !
It was such very long time that we meet today. So friends today our goal will be understanding of computer networking. As you already know in now a days we can not do anything without the help of a computer. Before I start computer networking let me tell you first about networking.
Networking is a term, when two or more than two devices interconnected each other via wired and through wireless and can exchange data between each other is called networking. The most easy and most useful example of networking are roads. Stations are the devices and vehicles are data.
                                                                       In the field of computer networking is same as above, take a look again when two or more computers interconnected each other through wires and wireless and transfer data between each other is called computer networking. Now here a question arise that "why we need computer networking ?"
The answer is pretty simple and easy, with the help of networking we can save our time a lot, we can decrease our expanses, we can control a whole city, state, country, or world from a single place without moving from there. Take a small example of networking, let us consider a bank there are many computers use at bank but all of they uses a single Printer, they can send message to their manager or other worker of the bank without any internet connection.
               This is the little and brief understanding of computer networking concept. Hope you all enjoy learning.