After reading this article you will learn about the definition of protocols.
The word protocol appears very frequently in any discussion about networking. While it has been used very frequently in the discussions, it has not been clearly explained.
Almost all wide area networks utilise TCP/IP and they have become practically synonymous with Wide Area Networks. When we continue the discussions on the development and growth of the Internet, we will note the important part played by these two protocols in this development.
A protocol is defined in the dictionary as “the original copy of a document such as a treaty” or as “diplomatic etiquette“. The meaning of protocols in networking is, expectedly, similar. A protocol is a set of rules according to which a particular service may be used. To take an example, suppose two diplomats, who both speak and understand different languages, wish to discuss an issue.
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Assume they wish to speak through a translator, but the translator does not know either language perfectly. However, each diplomat knows a language that the translator knows. Therefore, each has to express his thoughts in the language that the translator understands, who can then translate the speech into the language that the other diplomat understands.
Thus assume that one diplomat, who normally speaks English, also speaks French and the other diplomat, who normally speaks Spanish, also speaks Italian.
The translator understands both French and Italian but not English or Spanish.
Then the protocols are as follows:
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The English-speaking diplomat may think in English but must speak in French; the Spanish diplomat may think in Spanish but must speak in Italian.
The translator will translate the French, from the English diplomat, to Italian and relay it to the Spanish diplomat and translate the Italian from the Spanish diplomat to French and relay it to the English diplomat. (Sounds like a continental soup; unfortunately all protocols are not as palatable as this continental soup.)
Similarly, in networks, we have defined certain layers above. Each layer provides certain services and the protocols according to which it provides these services are the important protocols that we need to study. Let us, therefore, look at the protocols in some of the layers.
While it will neither be possible nor desirable to present and discuss all the protocols that are present in networks, we can take some example protocols and discuss them briefly. Since we shall be discussing mapping Internet addresses to IP addresses shortly, we may start this discussion on protocols by mentioning the protocols connected with address resolution.
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In the Internet, the addresses used by the users are in text form; for example, univall(dot)com and a URL address could be univall(dot)com/InfoTech/articles.
However, the network does not understand this address in text form. Secondly, even the IP address, which is numeric in form, is not understandable to Ethernet LANs. Therefore, the user’s browser first asks the Domain Name System for the IP address equivalent to the Internet address that is in text form. The resolver, a library program, does this.
This is done using a protocol called ARP or the address resolution protocol. ARP does this by broadcasting a message on the network, asking for the owner of a particular IP address. The format for this query is controlled by the address resolution protocol.
Similarly, the reverse problem may also occur occasionally, that is, given an Ethernet address, what is the equivalent IP address? This problem is solved using RARP or the Reverse Address Resolution Protocol.
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Similarly, two protocols called OSPF (Open Shortest Path First) and BGP (Border Gateway Protocol) are amongst those used for routing on the Internet. Similarly, UDP or User Datagram Protocol is used for packet transfer on the Internet.
But we shall concern ourselves with the two protocols TCP or Transmission Control Protocol and IP or Internet Protocol, which as are very widely used on the Internet—indeed on almost all Wide Area Networks. They are also the most widely discussed protocols and it will not be wrong to say that they form the glue that holds disparate networks on the Internet together.