Introduction To TCP/IP Protocol

The Transmission Control Protocol/Internet Protocol (TCP/IP) was created by the Department of Defense (DoD) in 1973 to ensure the data integrity and also to identify to correct person during the catastrophic war. In 1983, TCP/IP replaced all the old protocols and got authorized for the any type of communication taking place in ARPAnet.

TCP/IP is the set of rules which contains unique address to identify the particular device connected to the network. Now as TCP/IP protocol suite  was created by DOD, the model which TCP/IP follows for communication is also called DOD Model. Dod Model or the TCP/IP protocol suite is very similar to the OSI Reference Model. DoD Model consists of 4 layer which are as follows:

1. Process/Application Layer
2. Host-to-Host Layer
3. Internet Layer
4. Network Access Layer

The following figure shows the comparison between DoD Model and the OSI Reference Model:

 

The 4 layers of DoD Model does the same thing which is done by the 7 layers of the OSI Reference Model.

The Process/Application layer controls user interface which is done by the above three layers of the OSI Model. The Host-to-Host layer  maintains packet sequencing and data integrity. The Internet layer is similar to the Network layer of the OSI reference Model and does the work of routing the packets among the number of networks. The Network Access layer maintains the data exchange between host and the network which is equivalent to the work done by the DataLink and Physical Layer of the OSI reference Model.

The services provided by the different layer of the Dod model are as follows:

Process/Application Layer

• Telnet - Telnet allows the user to access the resources of another machine remotely
• File Transfer Protocol (FTP) – FTP protocol allows the user to transfer the files from the FTP server to the machine used by the user. It is actually used for the transformation of file.
• Trivial File Transfer Protocol (TFTP) – This protocol is similar to the FTP but has no directory browsing abilities, it can just send and receive a file.
• Network File System (NFS) – This protocol allows the user to share the files between the computers.
• Simple Mail Transfer Protocol (SMTP) – This protocol is used to send and receive a mail and it uses spooled method of mailing system.
• Line Printer Daemon (LPD) – This protocol is used for the printer sharing.
• X Window – Designed for client/server operations.
• Simple Network Management Protocol (SNMP) – Designed for gathering the various important information of the network devices.
• Hypertext Transfer Protocol (HTTP) – Used to view websites and to communicate between server and host.
• Hypertext Transfer Protocol Secure (HTTPS) – It does the same work like HTTP but this protocol uses SSL Secure Sockets Layer.

Host-to-Host Layer

1. Transmission Control Protocol (TCP) – This protocol is used for full duplex communication, and also for small error checking.
2. User Datagram Protocol (UDP) – UDP is used for the transportation of the message or information which doesn't require any delivery.

The Internet Layer

1. Internet Protocol (IP) – It consists of physical address as well as logical addresses to identify the machines.
2. Internet Control Message Protocol (ICMP) – This protocol gives information about network problems.
3. Address Resolution Protocol (ARP) – This protocol finds out the Hardware Address of the host from known IP Address.

The Network Access Layer

1. Ethernet – This protocol is used for the communication taking place between two hosts via Ethernet cables.
2. Fast Ethernet – This protocol is same as Ethernet but provides more speed then the Ethernet.

And Network Access Layer contains information of physical addresses and also it converts data into digital form and transports it.

This was whole introduction about the TCP/IP and its services

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How to Connect Two Computers in LAN to Play games or for data transfer

LAN gaming is more fun than the games played with single player. So if want to play the multiplayer game or to transfer the data through LAN, just need one LAN CABLE such as follows:

Now attach this LAN cable to the LAN ports of both the Computers. To understand better I have one picture to show.

This is the picture of two PC connected in a LAN via LAN cable.

Now you just need to do is to set IP Addresses of both the PC’s as follows:

• Press Windows Button + R to open Run.
• Copy the code from here control.exe /name Microsoft.NetworkAndSharingCenter , which are in red color and just paste it in the Run window opened and press Enter Key.
• Then after another window will get opened, in that window, go forward to Change adapter settings > Local Area Connection
• Now right click on Local Area Connection and go to properties.
• Then after click on Internet Protocol Version 4 (TCP/IPv4), in that choose the radio button named Use the following IP address
• Now enter the IP address and subnet mask as shown in above picture in both the computers.
• If want to connect more number of computers then go on increasing the last digit of IP.
• You can use other IP addresses also. But these are Class C IP they are called fake IP means not used in Commercial Field. So it is better to use this IP.

Important Note:  Firewall of both the computers must be turned off as it blocks some of the connections or some Packets.

How to turn off the Firewall of Computer in Windows 7:

• Open Run and copy the command from here Firewall.cpl with red characters and paste it in the run window and press Enter Key.
• Now click on Turn Windows Firewall ON or OFF in the which got opened.
• Now configure the options as shown in the figure below

Press okay and you are done. Turning off the firewall will allow you to play the games smoothly and also to transfer the data smoothly.

To transfer data from one pc to another pc just type the IP Address of computer from which you want to transfer data to another computer with double slash \\ (backward slash) like \\192.168.10.1. and press Enter. Shared files will be shown in your computer window and you can copy the data you need and transfer it easily with a very nice speed.

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The OSI(Open System Interconnection) Reference Model

The OSI reference model is layered step by step discussion of how to communication process takes place. There are seven layers in OSI reference model, each are made for its own functions. The OSI model isn’t physical, but it guides the developer to create application or hardware devices.

The seven layers of OSI Reference Model are as follows:

Now these seven layers of OSI are divided into two groups according to their functionality.

• The top three layers decide how to communicate with each other and with users
• The bottom four layers decide how data is transferred from host to host

These both group are having different functionality. Upper layer with three layer don’t know anything about Network or Network Address or IP Address because that functionality belongs to the bottom four layers.

Now let us see the functionalities of each layers of OSI Reference Model

Application Layer (layer 7):

Application Layer provides user interface to use the application when needed. Actually application layer comes into picture only when it is needed. For example if a user wants to open a file using HTTP/FTP or any protocol, then Application Layer provides interface (for example say Internet Explorer or any Browser). Similarly it provides interface for sending messages, for database, for application services etc.

The Presentation Layer (layer 6):

The function of Presentation Layer is to present the data to Application Layer and also it is responsible for data translation.

It performs the tasks like compression, encryption, decryption, etc

The session Layer (layer 5):

The Session Layer separates the data of one application from another application. It controls the data. The main work of this layer is to provide Dialog Control between devices and node. It Offers simplex, duplex, half duplex and full duplex services.

The Transport Layer (layer 4):

This layer provides end to end data transport services. TCP/IP protocols works at this layer. This layer also provides services like acknowledgement, flow control and sequencing.

The Network Layer (layer 3):

We saw that routers are called layer 3 devices, because they works on Network Layer Functionality. This layer determines all the addresses on the network. Used to transport traffic between the devices connected. All the routing protocols works at this level. Addresses such as IPv4, IPv6, MAC address are known to the layer 3 devices.

The Data Link Layer (layer 2):

This layer provides data transmission and also detect errors or watches the network topology. So Data Link Layer will ensure that a message are delivered to proper device or not, using MAC Address.

It will also convert the messages into bits for physical layer so that physical layer can transmit further. And the message in pieces are called Data Frames. It also contains MAC address of destination as well as of source.

Switches and Bridges are the example that works at layer 2. Hence they are known as layer 2 devices.

The Physical Layer (layer 1):

The Physical Layer of source transmits the data to the destination physical layer in bit format. The data will be in the form of bits (0 or 1). This layer is also used to know the physical links connected to the network devices such as cables, Ethernet cables etc.

Hub is the example which works at layer 1. That is why it is known as Layer 1 device.

So this was all about OSI layer.

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Internetworking Models(Reference Models) and the Layered Approach

Internetworking Models

Before when networks were new to the computer field, computers of different companies were not able to communicate with each other. Computers of same company was able to communicate but other company cannot communicate. This was a big problem for the manufacturers and the users too. There was no standard of communication devices and how the communication takes place between two computers.

So, after watching all this, ISO(International Organization for Standardization) created one model named as OSI(Open Systems Interconnection) reference model in 1970’s. So all the companies followed this standard and started manufacturing devices based on this standard. So computers from different manufactures were able to communicate. This kind of reference model describes how actually communication takes places and how the data gets transferred between two different networks. Now this OSI models are divided into different layers which we will see in next post. This is called as layered approach.

The Layered Approach

A reference model describes how to data flow from one network to another. Now this reference model is divided into various departments according to the work done by the departments or we can say groups. These groups are known as Layers. There are several processes taking place in transferring data which is handled by different layers of the model. This type of model is known as Layered Architecture.

Developers developed the model in such a way that only one layer don’t need to do whole process of the communication, but it is divided between all the layers. One layer will handle one function and other layer will handle another functions. This is how we can know about communication we study all the layers separately.

Advantages of Internetworking Models(Reference Models)

• It allows devices from different manufacturer’s to communicate
• It divides the process of communication into different layers and make it simpler to understand and to troubleshoot
• If changes are made in one layer other layers are not affected
• It defines the function for each layer and it makes easy for the manufacturer to manufacture the devices according to it

So this was all about the Reference Model and Layered Architecture.

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Router and its Functions

Router is a layer 3 (Network layer) device use to enable communication between two different Networks and to route data from one network to another. Suppose there are different branches of a particular Bank in different Cities. Now if we need all the branches of bank to communicate with each other then routers are used to connect one branch to another with the use of Cables known as lease lines.

Now Cisco became the standard company for the Routers because of its high quality devices and their services. In this world about 80% of the networking companies uses the Routers of Cisco. The following is the image of Cisco Router.

Functions of Router

Router by default blocks the broadcast domain. Now if we want to enable broadcast domain from router than we need to configure it accordingly. And also Router blocks collision domain as well. Routers are used for creating WAN(Wide Area Network). Routers are connected with serial ports with each other for WAN connections.

Routers are used to monitor router traffic. Also its Firewall of the Router is use to filter the data that transfers from the data. Various software's such as Router Monitoring Software are available from which we can know what is bandwidth of your Network.

The Main Function’s of Router are as follows:

• Packet Switching
• Packet Filtering
• Internetwork Communication
• Path Selection

Routers are also used to select the path according the protocol used to configure the router. Various protocols available to configure the Router.

Routers are basically the switches only, and also we can say that Routers are layer 3 switches.

Advantages of Router

Router do not forward packets by default and can filter the various information which is configured accordingly.

Router is more advantageous for creating Internetwork. It allows more bandwidth to the users. Further we will see the protocols of Routers and how to configure it.

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What are Switches and how does communication take place with the help of it?

Switches are Layer 2 (Network Layers) used to connect the hosts in LAN. Generally the main use of switch is to connect multiple number of computers and to enable communication between them in a same network. Now let us take a basic example to understand how does communication take place through switch.

 

As shown in above figure, two computers are connected to a switch(more number of computers can also be connected depends on the number of ports in switch). Now if PC-1 wants to communicate with PC-2, then same like hub, PC-1 don’t know the IP Address or MAC Address of PC-2. So what it will do is it will send one broadcast message to all the hosts connected to switch. But here in our case only two hosts are connected. So, the message sent by PC-1 to switch will be broadcasted by switch to the PC-2. So, PC-2 will come to know the IP Address and MAC Address of PC-1 and it will send ARP to the PC-1. This how they both got the information they needed to communicate with each other and they can start communication.
Now suppose if PC-1 wants to send message for the second time to PC-2, then switch will not broadcast the message to other hosts connected to the switch. So it means that switch creates only one Broadcast Domain.
Now assume that one more host is attached to  the switch after these two hosts and if PC-1 wants to communicate to that new host, then switch will not broadcast the message to PC-2(as it is known to PC-1 by its IP and MAC), but it will directly send message to the new host connected. This is how it breaks the Collision Domain.

Advantages of Switch over Hub

• Switches creates only one broadcast domain and no collision domain while Hub creates one broadcast domain as well as one collision domain for each host.
• Traffic reduces while using switch while it increases while using Hub.
• More number of Host can be connected(Maximum 48).

Important Note: Switches creates only one Broadcast Domain and no Collision Domain

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What is HUB and how do two PC communicates using HUB

A Hub is simple device used to connect two computers or more then two computers to enable communication between them. In other words a Hub is a multiport repeater which sends the data to other network. Now let us understand one basic network to understand the function of hub.

Basic Network using Hub

As shown in the figure two computers lets say Sid and Melly are connected to each other with the help of HUB. Now for example if Sid wants to communicate with Melly then what will he do ? Sid doesn't even know the IP address of Melly then how will he able to communicate? There are lots of question about communication taking place between them.

Now Sid knows only two things, first is IP Address of himself that  is 192.168.10.2 and MAC Address(Hardware Address that is given by the company) of himself that is 00:3b:4c:00:34:cc. IP Address of Melly is 192.168.10.3 and MAC Address is 00:3b:5c:11:as:cc as shown in the figure. But these Addresses of Melly are not seen or known by Sid.

So now what Sid will do is, he will just send message “Hi, Melly” to the HUB. He is actually not knowing that where his data/message is going. Now when the message reaches HUB , and now what is HUB going to do is it will broadcast the message sent by the Sid(Source) to all the Computers attached to its port.

Source                       Destination

192.168.10.2            192.168.10.255

So as shown above Sid’s message will be broadcasted to all the Computers attached to the HUB, because HUB will consider the Destination Address as 192.168.10.255. Now as data is sent to all the computers, Melly will also receive it. And all other computer will also receive the same, but now out of all the person whose name is Melly will send back the Message with its IP Address as well as its MAC Address to the Source.

( Actually Sid’s IP Address and his MAC Address will be broadcasted like follows

source          : 192.168.10.2(00:3b:4c:00:34:cc)
Destination: 192.168.10.255(FF:FF:FF:FF:FF:FF)

)

So in this way Sid can come to know the IP Address of Melly. Melly will send ARP(Address Resolution Protocol) to the Sid, and it will be containing the IP Address of her and also MAC Address. So now the Destination for the Melly will be Sid’s IP Address and MAC Address to send ARP.

Source                                                              Destination
192.168.10.3(00:3b:5c:11:as:cc)             192.168.10.2(00:3b:4c:00:34:cc)

Now both of them are having the things they need to communicate with each other. This is how communication take place in HUB.

Disadvantages of HUB

• It is Layer 1 device
• Cannot break Broadcast Domain as well as Collision Domain
• Low Bandwidth
• High Traffic of data

Reason of Collision and high Traffic while using HUB

Suppose that one network is created using HUB. Assume, in that network 50 computers are connected via HUB. Now if all of them starts sending data at a same time then HUB will broadcast all the data to each of the computer connected to its port. So main reason to this traffic and collision is the broadcast. If the number of computer increases in the network traffic will increase and whole network can go down. That is why Bridges and Switches came in market to resolve this kind of problem of the HUB.

Important Point about HUB: HUB works with one Broadcast Domain as well as one Collision Domain

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