About the OSI and TCP / IP

OSI (Open Systems Interconnection)

OSI is a conceptual model consisting of seven layers, each layer has a different function. OSI was developed by the international agency that is ISO (International Organization for Standardization) in 1977.

The function of each layer of the OSI:

     1. Physical Layer

Physical Layer is the layer that very simple, relating to electrical (and optical) connections between devices. This layer Serves to define the network transmission media, signaling method, synchronization bits, network architecture (such as Ethernet or Token Ring), network topology and pengabelan. In addition, this level also defines how the Network Interface Card (NIC) can interact with the media cable or radio.

2. Data-link Layer

Data link layer is responsible at the end of the package binary data derived from a higher level into discrete packets before the physical layer. Will send frames (block of data) via a network. Protocol on the data-link layer is Ethernet (802.2 & 802.3), Tokenbus (802.4) and Tokenring (802.5).

3.      Network Layer

Network layer provides routing functionality so that packets can be sent out from the local network segment to a destination that is on a network other.

Some network layer functions:
- Divide the binary data stream into discrete packets with a certain length
- Detect Error
- Fix error with resend the corrupted packet
- Controlling the flow

4. Transport Layer
Transport layer is the center of the fashion-OSI. Serves to break down data into packets of data and provide the serial number of the packages that can be rearranged on the side of the goal as it arrives.

5. Session Layer
This layer coordinates communication between the layer entities they represent. Serves to define how the connection can be established, maintained, or destroyed. In addition, at this level also performed name resolution. Some of the protocol at this layer: NETBIOS: a session interfaces and protocols, developed by IBM, which provides service to the presentation layer and application layer. NETBEUI, (NETBIOS Extended User Interface), a development of NETBIOS used in micro ** oft networking products, such as Windows NT and LAN Manager. ADSP (AppleTalk Data Stream Protocol). PAP (Printer Access Protocol), which is found on a Postscript printer to access the AppleTalk network.

6. Presentation Layer
Serves to translate the data to be transmitted by the application into a format that can be transmitted over the network. The protocols are in this level is redirektor software (redirector software), such as Workstation service (in Windows NT) and Network shell (a sort of virtual network computing (VNC) or Remote Desktop Protocol (RDP).

7. Application Layer
Application Layer is the primary interface between applications running on one computer and network resources that require access to it. Application layer is the layer where the user will operate it, protocols such as FTP, telnet, SMTP, HTTP, POP3 is the Application layer.

TCP / IP (Transmission Control Protocol / Internet Protocol)

TCP / IP is a data communications standard used by the Internet community in the process of exchanging data from one computer to another computer on the network the Internet. TCP / IP is an open networking standard that is independent of physical network transport mechanism used, so it can be used anywhere.

The function of each layer in the TCP / IP:
- Physical Layer
Bottom layer is a layer that defines the physical quantities such as the communication medium, voltage, current, etc.. TCP / IP is flexible so it can integrate the various networks with the physical medium is different.

- Network Access Layer
Has the distribution function set data frames on the physical media used reliably. This layer usually provide service for the detection and correction of errors of data transmitted. Some examples of protocols used at this layer is X.25 public networks, Ethernet for networking Etehernet, AX.25 for packet radio networks, etc..

- Internet Layer
Having such a function at the Network Layer of the OSI that defines how the relationship can occur between two parties who are on different networks. In this layer duty to ensure that a packet is sent to find the goal wherever located. Therefore, this layer has a particularly important role in realizing the vast territory covering internetworking (Internet worldwide).

Some of the important tasks at the Internet layer are:
• Addressing
which complement each datagram to the Internet address of the
purposes. This protocol addresses the known IP Address.
• Routing
Determine to which datagram will be sent in order to achieve the desired goals. This function is the most important functions of the Internet Protocol (IP). Routers on the network TCP / IP is very crucial in the delivery of datagrams from the receiver to the destination.

- Transport Layer
Function in defining the ways to perform data transmission between end to end in a reliable host. This layer ensures that the data received with the data that is sent to the sender.

Some essential functions include:
Flow Control
Delivery of data that has been broken down into packets must be arranged in such a way so that the sender not to transmit data at speeds that exceed the ability of recipients to receive the data.
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 found errors in the received data packet, the receiver will not receive the data. Sender will retransmit data packets that contain errors earlier.

- Application Layer
Serves to define applications that run on the network. Protocols at this layer example is SMTP (Simple Mail Transfer Protocol) for sending e-mail and FTP (File Transfer Protocol) to transfer files.