Protocol Overview

In information technology context, protocol means a communications standard between systems or computer in a network. With existence of protocol hence a data can be transmission to destination node and after that, hence the data is acceptable truly. This communications procedures is very complex, include of errors way to overcome, way of sending data, way of the source gives information that data was transmitted successfully and also how the destination knows that data was accepted.

Protocol can be divided two kinds, that is:
1.Low-level of protocol
This protocol determines data transmission rule from electronic side and physical, for example rule about bit and byte ordering, mechanism of error detection and corrective of errors. Example of this protocol is TCP/IP (Transfer Control Protocol/Internet Protocol).
2.High-level of protocol
This protocol is responsible with data format, for example like syntax from message sent, message sequence sent (handshaking) and set character applied. Examples from this protocol are SMTP and POP3 for e-mail, HTTP for web browsing and FTP for transfer file and others.

Protocol should have the character of standard that can be applied by all sides. At internet community is recognized which named RFC (Request For Comment). RFC is a kind of documents containing rule protocol, which has become standard and or which still in phase experiment or draft. All protocol standards in internet always is written documentary of RFC and given by certain number.


In general communications protocols of Open System Interconnection applied is divisible in seven protocols, there are:
a)Physical layer.
The lowest layer in the form of communications channel hardware applied. This peripheral cans be in the form of telephone channel, communications radio-set, modem peripheral and computer.
b)Data Link layer.
This layer is arranging the communications between two computers. This protocol only arranges delivery of data between two computers through the physical layer.
c)Network layer.
This protocol controls the relationship between computers in network which connected many computers. For example, find the route relation between one computer to other computer assisted by this protocol.
d)Transport layer.
This protocol is responsible of delivery reliability of data out of one computer to other computer in network.
e)Session layer
The session layer establishes, manages and synchronizes the communication between two communicating computers
f)Presentation layer
This layer encodes and decodes data in a mutually agreeable format. This layer also compresses and decompresses data packets.
g)Application layer
Application layer provides an interface between the user and the network. Some of the common application on this layer is Telnet, file transfer of protocol (FTP).

Although theoretically there are seven protocol layer, practically not always all levels applied by network. At some a real computer network techniques complicated protocol layer layer simple generally is not applied, and application program directly joined with others at physical layer.
By : Ferdinan