431_ppt_V1_Computer Systems and Information Security

describe network components (nodes, routers, switches) and their purpose;
explain the purpose and representation of an IP address; explain the purpose of a domain name system (DNS); explain the purpose of a private virtual network
explain the meaning "information security", "confidentiality", "integrity" and " accessibility»;
Assess the need for data encryption and mirroring;
explain the user data security measures: passwords, accounts, authentication, biometric authentication
argue the use of different methods of identification.

IP-address - is the main type of addresses on the basis of which the network layer transmits packets between networks. These addresses consist of 4 bytes. They are assigned by the administrator during the configuration of the computers and the router. It consists of two parts:
a) Network number — chosen by the administrator arbitrarily or assigned by the InterNic service;
b) Node number in the network - assigned independently of the local node address.

IP address. In order for the computers to find each other in the information exchange process, there is a single addressing system on the Internet based on the use of an IP address.
Each computer connected to the Internet has its own unique 32-bit (in binary) IP address, which uniquely identifies the computer.

For software and hardware devices, an IP address is just an integer to store which is allocated exactly 4 bytes of memory. Those. a number in the range from 0 to 4294967295. It is difficult for a person to memorize such bulky numbers. Therefore, for clarity, the IP address is recorded as a sequence of four numbers separated by dots in the range from 0.0.0.0 to 255.255.255.255. Each of these four numbers corresponds to the value of each byte of the four, in which the whole number is stored.

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Four pieces of paper were found at the scene. The investigation found that they recorded fragments of one IP address. Criminologists have identified these pieces with the letters A, B, C and D.
Restore the IP address.
In the answer, specify the sequence of letters denoting the fragments in the order corresponding to the IP address.

Decision:
the most important thing is to remember that each of the 4 numbers in the IP address must be in the range from 0 to 255
therefore, we immediately determine that fragment A is the most recent, because otherwise one of the numbers is greater than 255 (643 or 6420)
G fragment (number 20) can only be the first, since variants 3.1320 and 3.13320 give a number greater than 255
of fragments B and C first must be B, otherwise we get 3.1333.13 (1333> 255)
thus, the correct answer is GBVA.

DNS (Domain Name System) – domain name system
A domain is a set of hosts joined into a logical group.
DNS is a distributed database that supports a hierarchical name system and is designed to determine the IP address by a known symbolic host name (and Vice versa).
one.example.com – relative domain name
one.example.com ahhh! – absolute domain name
. – root domain
com. – first (top) level domain
example.com ahhh! – second level domain
one.example.com ahhh! – third-level domain 2

DNS (Domain Name System) – domain name system
DNS converts the digital IP address of the host (computer) into a character set. Domain - a group of network resources that has its own name and is managed by its network station.
The address of a resource of the world wide web, recorded in the DNS standard, is divided into several components, separated from each other by a point. These elements are called "domains". This designation is called URL (Uniform Resource Locator), which can be translated into Russian as "universal resource locator".

Distributed DNS database
First level:
generic name:
com – commercial organizations
edu – educational institutions
gov – governmental organizations
org – non-profit organizations
net – the organization that supports network 

State domains:
Kz – Kazakhstan
ru – Russia
am – Armenia
at – Austria
tv – Tuvalu
io – British Indian ocean territory
me – Montenegro

The working principle of DNS:
To find the desired computer on the Internet custom machines help DNS servers, which are programs that are accessed to seek out the correct IP address for the URL.