Friday, January 20, 2012

Acquainted with the TCP / IP


History of TCP / IP commencement of the birth of the ARPANET packet switching network is digital, funded by DARPA (Defense Advanced Research Projects Agency) in 1969. Meanwhile, the ARPANET continued to increase in size so that the protocol used at that time could no longer accommodate the number of nodes is more and more. Therefore, DARPA funded the creation of the more common communication protocols, namely TCP / IP. He was adopted into the standard ARPANET in 1983.

To facilitate the process of conversion, DARPA is also funding a project that implements this protocol into BSD UNIX, so began the marriage of UNIX and TCP / IP .. At first the internet is used to refer to networks that use internet protocol (IP) but with the development of networks, the term is now a generic term used for all classes of networks. Internet is used to refer to communities worldwide computer networks that are interconnected with TCP / IP.


The development of TCP / IP is widely accepted and practically become de-facto standard computer network-related traits contained in the protocol itself, which is keunggulun of TCP / IP, namely:

• The development of TCP / IP uses an open protocol standard that is widely available. Everyone can develop software to be able to communicate using this protocol. This makes use of TCP / IP extends very quickly, especially in terms of adoption by a variety of operating systems and network applications.
• Not dependent on the hardware or operating system specific network so TCP / IP suitable for bringing together a wide range of networks, eg Ethernet, token ring, dial-up line, X-25 net and others.
• How the addressing is unique on a global scale, allowing the computer to uniquely identify the other computers in the entire network, even though its network of worldwide Internet network. Every computer connected to a TCP / IP (Internet) will have an address that belongs only to him.
• TCP / IP routing has the facilities and other types of services that enable applied to the internetwork.

Architecture and Network Protocol TCP / IP

In a computer network architecture, there is a layer-layer (layer) which has a specific task and has its own protocol. ISO (International Standards Organization) has issued a standard for computer network architecture known as the Open Systems Interconnection (OSI).

Comparison of Architecture OSI and TCP / IP
Although the numbers vary, but all the functions of the layers of the OSI architecture are covered by the architecture of TCP / IP. The details of the function of each layer architecture of TCP / IP is as follows:

• Physical Layer (physical layer)
Is the lowest layer that defines the physical quantities such as media communications, voltages, currents, etc.. This layer may vary depending on the medium of communication on the network in question. TCP / IP is flexible so it can integrate the integration of various networks with physical media is different.

• Network Access Layer
function similar to the OSI Data Link layer. These layers organize the distribution of data frames on the physical medium is reliable. This layer usually provides services for error detection and correction of data transmitted. Some examples of protocols used at this layer is X.25 public network, Ethernet for networking Etehernet, Package Radio AX.25 networks and so on.

• Internet Layer
defining how the relationship can occur between two parties that are on different networks such as the Network Layer of the OSI. On the Internet network that consists of tens of millions of hosts and hundreds of thousands of local networks, this layer is responsible for ensuring that a packet that is sent to find the goal wherever located. Therefore, this layer has a particularly important role in realizing internetworking covering large areas (worldwide Internet). Some of the important task at this layer are:
1. Addressing, which complement each datagram with the Internet address of the destination. Addresses on this protocol known as Internet Protocol Address (IP Address). Because the addressing (addressing) on ​​the network TCP / IP is at this level (software), then the TCP / IP network independent of the type of media and computer use.
2. Routing, which determines where the datagram will be sent in order to achieve the desired goal. This function is the most important functions of the Internet Protocol (IP). As a protocol that is connectionless, the routing process is fully determined by the network. Sender has no control over it sends packets to reach the goal. Routers on the network TCP / IP is very crucial in the delivery of datagrams from the receivers to a destination.

• Transport Layer
define the ways to perform data transmission between end to end hosted reliably. This layer ensures that the information
received at the receiver side is equal to the information submitted to the sender. To that end, this layer has several important functions, among others:

1. Flow Control. Delivery of data that has been broken down into packets must be so arranged so that the sender not to transmit data at speeds that exceed the ability of recipients to receive the data.

2. Error Detection. Sender and receiver also complement the data with some information that could be used to check the data transmitted is free from error. If you found an error in the received data packet, the receiver will not accept data. Sender will retransmit the data packets that contain errors earlier. However, this can cause significant delay.

In the TCP / IP, the protocol used is the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP). TCP is used for applications that require reliability data, whereas UDP is used for applications that require short packet length and does not demand high reliability. TCP has a function of flow control and error detection and connection-oriented nature. In contrast to the UDP which is connectionless there is no mechanism to check data and flow control, so called unreliable UDP protocol. For some matters relating to the efficiency and simplification, some applications choose to use UDP as the transport protocol. An example is a database application that merely query and response, or other applications that are highly sensitive to delay such as video conferencing. Such applications can tolerate a bit error (image or sound can still be understood), but would be uncomfortable to be seen if there is a significant delay.

• Application Layer
is the last layer in the architecture of TCP / IP that serves to define the applications that run on the network. Therefore, there are many protocols in this layer, in accordance with the number of TCP / IP applications that can be run. Examples are SMTP (Simple Mail Transfer Protocol) for sending e-mail, FTP (File Transfer
Protocol) for file transfer, HTTP (Hyper Text Transfer Protocol) for web applications, NNTP (Network News Transfer Protocol) for the distribution of news group and others. Each application generally uses TCP and IP protocols, so the whole family is named after the protocol with TCP / IP.

Delivery and Acceptance Data Package

Layers and protocols contained in the network architecture of TCP / IP describes the functions in communication between two computers. Each layer receives data from the layers above or below it, then process the data according to the protocol functions they have and forward it to the next layer. When two computers communicate, there is the flow of data between sender and receiver through the layers above. At the sender, the data flow is from top to bottom. Data from the user or an application sent to the Transport Layer in the form of packets with a certain length. The protocol adds a number of bits in each packet as a header that contains information about the sequence of segmentation to maintain data integrity and pariti bits for error detection and correction.
From the Transport layer, which has given the header data is forwarded to the Layer Network / Internet. In this layer occurs by the addition of protocol header that contains the destination address information, the sender address and other information needed to perform routing. Then there was the direction of routing data, ie to the network and the interface where the data will be sent, if more than one interface on the host. In this layer can also occur segmentation data, because the length of the package to be delivered must be adapted to the conditions of communication media on a network that will be traversed.

Final data will arrive at the Physical Layer which sends the data in the form of electrical magnitudes / physical such as voltage, current, radio waves or light, according to media used.

At the receiver, the data processing is similar as above only in the opposite sequence (from bawqah upwards). Received signal at the physical layer to be changed in the data. The protocol will examine the integrity and if not found error t header that is added will be removed.

Furthermore, the data passed to the network layer. In this layer, the destination address of the packet data received will be checked. If the destination address is the address given host, then the network layer header will be removed and the data will be forwarded to the layer above it. But if not, the data will be forwarded to the destination network, in accordance with routing information owned.

At the Transport layer, the truth of the data will be examined again, using the header information sent by the sender. If no error, the data packets received will be rearranged in this order at the time will be sent and forwarded to the application layer at the receiver.

The process is carried out each layer is known as data encapsulation. Encapsulation is transparent in nature. That is, a layer does not need to know how many layers above it and below it. Each one is only doing his job. At the sender, this task is to receive data from the layer above, processing such data in accordance with the protocol functions, adds protocol headers and forwarding to the layer below.

At the receiver, this task is to receive data from the layer below it, according to the data processing functions of the protocol, the protocol headers are removed and continue to layer on top of it.

Internet Protocol

Internet Protocol (IP) functions delivering data packets to the correct address. Therefore, the Internet Protocol plays a very important part of the network TCP / IP. Because all applications are TCP / IP must be based on Internet Protocol in order to run properly.

IP is a protocol at the network layer are:
1. Connectionless, ie, every packet of data sent at one time going through the route independently. IP packet (datagram) is going through a route that is determined by each router through which the datagram. This allows the entire datagram arrives at its destination in a different order for different route anyway.
2. Or unreliability unreliable IP protocol does not guarantee that the datagram must be sent to the destination. He will only do a best effort delivery that is doing their best so that the packets sent to its destination.

A datagram may not arrive safely to its destination because of the following:
• The bit error during transmission of a datagram to a medium
• The router is skipped mendiscard datagram due to congestion and lack of buffer memory space
• The breakdown in route to a destination for a while due to the router is down
The occurrence of chaos routing, so the datagram looping

IP is also designed to be able to pass through various media of communication that has the characteristics and different speeds. On Ethernet networks, the length of a datagram will be greater than the length of the datagram to the public network that uses the telephone network media, or on the wireless network. This difference is solely to achieve a good throughput on each medium. In general, the faster data transfer capabilities in the media, the greater the maximum datagram length is used. As a result of these differences, the IP datagram can be fragmented when switching from medium to high speed low speed (eg from 10 Mbps Ethernet LAN to a leased line using Point-to-Point Protocol with a speed of 64 kbps). At the router / host recipients, the datagram this fragment that were to be put together again before passing to the next router, or to the transport layer on the destination host. This adds processing time on the router and cause delay.

The whole nature described in the above is the result of the protocol efficiency is sacrificed as a consequence of the superiority IP protocol. These advantages combine the capabilities of the various media of communication with different characteristics, with the development of flexible network, able to change the routing automatically if a route fails, and so on. For example, to be able to dynamically change the routing, the routing mechanism chosen is determined by network conditions and network elements (routers). In addition, the routing process should also be made for each datagram, not only at the beginning of a relationship. Let us consider the structure of the header of the IP protocols and their respective functions.

Each protocol has extra bits beyond the information / data it carries. In addition to information, these bits also serve as a tool of control. In terms of efficiency, the greater the number of these extra bits, the smaller the efficiency of communication that run. Conversely the smaller the amount of these extra bits, the higher the efficiency of communication that are running. Here is done the trade-off between reliability and efficiency datagram. For example, the IP datagram in order to find the goal, it needs additional information to be included in this header.


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