Basic principles of the Internet
One of the main reasons for the success of the Internet undoubtedly lies in the efficiency, ease of use, and convenience of its technological bases. We have seen what a computer network in general is and what its structures are or, to put it in computer terminology, its hardware, focusing in particular on the structure of the Internet. But, as is known, in the world of information technology an equally important role is played by the logical level, the software. In this chapter, therefore, we will focus precisely on this logical level of the network, and we will, also from this point of view, take a look at 'inside the box'.
We certainly do not intend to provide all the notions that would find a place in a technical manual on internetworking systems: we will only try to introduce the fundamental principles of technologies that guarantee the Internet to function efficiently and safely.
This introduction, if on the one hand meets the completeness needs that a manual must comply with, nevertheless provides the reader with some notions which should be part of the knowledge base of an 'expert' user of the Internet. Essential baggage to make the most of its potential: knowing how things work, in fact, allows you to identify the causes of any problems or malfunctions, and, if not always to solve them, at least to give precise information to those who will have to intervene.
We certainly do not intend to provide all the notions that would find a place in a technical manual on internetworking systems: we will only try to introduce the fundamental principles of technologies that guarantee the Internet to function efficiently and safely.
This introduction, if on the one hand meets the completeness needs that a manual must comply with, nevertheless provides the reader with some notions which should be part of the knowledge base of an 'expert' user of the Internet. Essential baggage to make the most of its potential: knowing how things work, in fact, allows you to identify the causes of any problems or malfunctions, and, if not always to solve them, at least to give precise information to those who will have to intervene.
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Inevitably, we will be forced to use a number of strange abbreviations, with which network technologies are normally designated. But probably our readers have already got used to this: on the other hand, the Internet lexicon is populated with acronyms and the expert navigator must resign himself to living with it. In any case, reading this chapter, like all the others in this section, is not essential to successfully use the various services that we have already studied in the first part of the manual. If you want you can, therefore, skip it, and maybe come back when you are more familiar with the world of the Internet.
A common language: the TCP / IP protocol
The Internet is a communication tool. A communication tool between computers, and between men who use computers interconnected through the network. Of course, the two players on the field, computers, and men, have different, often conflicting, needs that must be borne in mind in order for communication to be successful. The technologies on which the Internet is based have evolved over the years precisely to respond to these needs with maximum efficiency.
The first problem in any communication process is, of course, the definition of a language that is shared between the different actors who communicate; actors who, in the case of the Internet, are primarily computers. And computers, as is well known, although they all use the same alphabet - the binary code - often 'speak' different and incompatible languages. Metaphorically speaking, different computers use operating systems, character codes, data structures, which can also be very different. To allow communication between one and the other it is necessary to define rules shared by all. This function, in the field of telematics, is carried out by protocols.
In the diplomatic world, 'protocol' means a series of rigidly coded rules of behavior and etiquette, which allow people from different cultural universes to interact without creating dangerous misunderstandings. Protocols are also called international agreements or treaties. These meanings of the term can also be metaphorically accepted in the field of telematics: a communication protocol defines the common rules that a computer must know in order to process and send the bits through a specific medium of physical transmission to another computer. Therefore, a protocol must specify how the signal is to be encoded, how to make the data travel from one node to another, how to make sure that the transmission has been successful, and so on.
In the case of the Internet, which interconnects millions of computers and subnets, based on different operating environments and hardware architectures, these protocols must respond to particularly complex needs. And as we have seen, the history of the network has been marked by the development of its fundamental protocols. The fundamental nucleus, the set of protocols that allow the operation of this complex and multifaceted telematic communication system, is commonly indicated with the abbreviation TCP / IP, which is an acronym for Transmission Control Protocol / Internet Protocol.
We can say that one of the reasons for the Internet's success lies precisely in the characteristics of its communication protocol. First of all, TCP / IP is independent of the way the network is physically created: a TCP / IP network can be supported indifferently on a local Ethernet network, on a telephone line, on a fiber optic cable, on a network of satellite transmission ... and so on. Indeed, it is explicitly designed to easily integrate different hardware technologies into a single logical communication structure.
Secondly, TCP / IP is a communication protocol that solves the technical problems of a heterogeneous geographical network such as the Internet very efficiently:
make the most of the available communication resources;
allow efficient and safe addressing of connected computers, even if these are several million 02 ;
ensure the best possible communication with maximum security;
allow the development of advanced and easily usable network resources and services.
And finally, as mentioned, TCP / IP is an open standard, whose specifications are freely usable by anyone without any copyright limitation. This allowed the rapid spread of implementations for each existing operating system and platform, implementations often distributed free of charge or natively integrated into the system itself.
A layered protocol
What is commonly referred to as TCP / IP, in reality, consists of a real set of communication protocols, each with a specific task, organized in a hierarchical manner 03? In technical terms, it is said that it is 'protocol levels of services' ( layers of services ). To be precise, the TCP / IP architecture is based on a four-level model:
application level, which manages the network services for the user and therefore is the final source and destination of each network transaction;
the transport layer, which manages the organization of data for transmission purposes and has the task of checking that the communication of a certain block of data has been successful, and of retransmitting what has possibly been lost;
the network layer, which manages the addressing of computers and the routing of data;
physical and data link layer, which manages the use of cables and the sending of physical signals over the network (but is not properly part of TCP / IP).
In the TCP / IP architecture, one or more protocols correspond to each level. During the course of a transaction, the sequence of the various levels corresponds to a sequence of operations necessary for data transmission. In the sending phase, the data start from the application level, and pass in sequence through the stack of layers; each protocol receives the data from the upper level, adds the management information that belongs to it in a header), and then switches everything to the lower level, up to the level that sends the signal along the channel. In the receiving phase, the reverse process occurs naturally. The data arrived via the physical layer and the network layer pass to the transport layer that reads the header intended for it, recompose the message, and then pass it all to the application layer. Of course, in reality, things are much more complicated, but this description makes the idea. In short, TCP / IP can be seen as a sort of delivery service based on a Chinese box mechanism: at the time of shipment, the data is 'wrapped' in a box (which will carry some indications on the content outside), this box is placed in another box (with another type of indication on the outside), and so on. Upon receipt, the boxes are 'opened' one after the other, obtaining from each the information reported on it. Each interaction between two computers on the network consists of packaging and sending a series of boxes.
Inevitably, we will be forced to use a number of strange abbreviations, with which network technologies are normally designated. But probably our readers have already got used to this: on the other hand, the Internet lexicon is populated with acronyms and the expert navigator must resign himself to living with it. In any case, reading this chapter, like all the others in this section, is not essential to successfully use the various services that we have already studied in the first part of the manual. If you want you can, therefore, skip it, and maybe come back when you are more familiar with the world of the Internet.
A common language: the TCP / IP protocol
The Internet is a communication tool. A communication tool between computers, and between men who use computers interconnected through the network. Of course, the two players on the field, computers, and men, have different, often conflicting, needs that must be borne in mind in order for communication to be successful. The technologies on which the Internet is based have evolved over the years precisely to respond to these needs with maximum efficiency.
The first problem in any communication process is, of course, the definition of a language that is shared between the different actors who communicate; actors who, in the case of the Internet, are primarily computers. And computers, as is well known, although they all use the same alphabet - the binary code - often 'speak' different and incompatible languages. Metaphorically speaking, different computers use operating systems, character codes, data structures, which can also be very different. To allow communication between one and the other it is necessary to define rules shared by all. This function, in the field of telematics, is carried out by protocols.
In the diplomatic world, 'protocol' means a series of rigidly coded rules of behavior and etiquette, which allow people from different cultural universes to interact without creating dangerous misunderstandings. Protocols are also called international agreements or treaties. These meanings of the term can also be metaphorically accepted in the field of telematics: a communication protocol defines the common rules that a computer must know in order to process and send the bits through a specific medium of physical transmission to another computer. Therefore, a protocol must specify how the signal is to be encoded, how to make the data travel from one node to another, how to make sure that the transmission has been successful, and so on.
In the case of the Internet, which interconnects millions of computers and subnets, based on different operating environments and hardware architectures, these protocols must respond to particularly complex needs. And as we have seen, the history of the network has been marked by the development of its fundamental protocols. The fundamental nucleus, the set of protocols that allow the operation of this complex and multifaceted telematic communication system, is commonly indicated with the abbreviation TCP / IP, which is an acronym for Transmission Control Protocol / Internet Protocol.
We can say that one of the reasons for the Internet's success lies precisely in the characteristics of its communication protocol. First of all, TCP / IP is independent of the way the network is physically created: a TCP / IP network can be supported indifferently on a local Ethernet network, on a telephone line, on a fiber optic cable, on a network of satellite transmission ... and so on. Indeed, it is explicitly designed to easily integrate different hardware technologies into a single logical communication structure.
Secondly, TCP / IP is a communication protocol that solves the technical problems of a heterogeneous geographical network such as the Internet very efficiently:
make the most of the available communication resources;
allow efficient and safe addressing of connected computers, even if these are several million 02 ;
ensure the best possible communication with maximum security;
allow the development of advanced and easily usable network resources and services.
And finally, as mentioned, TCP / IP is an open standard, whose specifications are freely usable by anyone without any copyright limitation. This allowed the rapid spread of implementations for each existing operating system and platform, implementations often distributed free of charge or natively integrated into the system itself.
A layered protocol
What is commonly referred to as TCP / IP, in reality, consists of a real set of communication protocols, each with a specific task, organized in a hierarchical manner 03? In technical terms, it is said that it is 'protocol levels of services' ( layers of services ). To be precise, the TCP / IP architecture is based on a four-level model:
application level, which manages the network services for the user and therefore is the final source and destination of each network transaction;
the transport layer, which manages the organization of data for transmission purposes and has the task of checking that the communication of a certain block of data has been successful, and of retransmitting what has possibly been lost;
the network layer, which manages the addressing of computers and the routing of data;
physical and data link layer, which manages the use of cables and the sending of physical signals over the network (but is not properly part of TCP / IP).
In the TCP / IP architecture, one or more protocols correspond to each level. During the course of a transaction, the sequence of the various levels corresponds to a sequence of operations necessary for data transmission. In the sending phase, the data start from the application level, and pass in sequence through the stack of layers; each protocol receives the data from the upper level, adds the management information that belongs to it in a header), and then switches everything to the lower level, up to the level that sends the signal along the channel. In the receiving phase, the reverse process occurs naturally. The data arrived via the physical layer and the network layer pass to the transport layer that reads the header intended for it, recompose the message, and then pass it all to the application layer. Of course, in reality, things are much more complicated, but this description makes the idea. In short, TCP / IP can be seen as a sort of delivery service based on a Chinese box mechanism: at the time of shipment, the data is 'wrapped' in a box (which will carry some indications on the content outside), this box is placed in another box (with another type of indication on the outside), and so on. Upon receipt, the boxes are 'opened' one after the other, obtaining from each the information reported on it. Each interaction between two computers on the network consists of packaging and sending a series of boxes.
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