Selected Sections of Applied Informatics

Transcription

1 Selected Sections of Applied Informatics M.Sc. Marcin Koniak Based on lecture: Dr inż. Andrzej Czerepicki 2018

2 Lecture 1: Concept and IT departments. Java programming language, computer networks. IP addresses. Network architecture. Internet - Global Network. 2

3 Computer Science Computer Science science on methods and technologies of information acquisition, storage and data processing Computer Science Theoretical (methods) Applied (technologies) 3

4 IT applied Applied IT sections Development Programming Administration Desktop applications Mobile applications Network services Web applications Computer Science I, II SSAI Graphics. Networks Security 4

5 Computer networks architecture, protocols, communication 5

6 Computer Network Computer network - a group of computers connected through communication channels and cooperating with each other in order to: more efficient processing of data increased reliability of the overall system to increase the security of data storage, collaborative and remote work on objects facilitate communication between users 6

7 Computer network elements Data network media (physical connections) Devices protocols Software

8 Data transmission network medium Coaxial cable twisted-pair cable WiFi optical fiber 8

9 Classification of networks by topology How to connect computers to a network at physical level (data connection) Bus Ring Star 9

10 Classification of networks by range PAN Personal Area Network LAN Local Area Network CAN Campus Area Network WAN Wide Area Network MAN Metropolitan Area Network VPN Virtual Private Network The classification is approximate, e. g. local networks may have a large physical scope (e. g. settlement network) 10

11 Classification of networks according to the method of communication between nodes Peer-to-peer Network (P2P) Serwer-based network 11

12 Network communication layers User A User B Hello! Application layer > A: Hello! App App Transport layer (protocol) Computer Computer link link Network card Data link layer (physical) Network card 12

13 Network communication layers Physical layer: Provides a network connection between the recipient and the sender (data link) Transport layer: provides the transfer of information packets between users' computers (sender/receiver) Application layer: provides a way and interface for communication between users (service, website, dialogue, downloads etc.). 13

14 TCP/IP protocol layer Network communication layers Network layer Protocols Application Applications using the network to provide services (HTTP, FTP, SMTP, POP3, DNS,...) Transport Network Data link Methods of providing information from the recipient to the addressee (TCP, UDP) Address of computers in the network (IP, ARP, ICMP, RARP) Implementation of message transmission on physical connections(ethernet, WiFi) 14

15 Data link layer Network Interface Card converts logical signals from a computer into electrical signals transmitted via data links and vice versa Network adapter on the desktop, PCI interface Wireless USB network card 15

16 MAC address of the network card The physical address of the network card is used to uniquely identify the sender/receiver at network link level. Each network card in the world should have its own unique address Structure of the MAC address: [manufacturer][type and number of the network card] Example: E8-2A-EA-04-2F producer serial number 16

17 Transport layer? Problem adresacji w sieci Transmission Control Protocol (TCP/IP) - basic protocol of modern computer networks. TCP (Transportation layer) is responsible for the "dialogue" between sender and recipient during the exchange of information (the connection can be interrupted at any time, the TCP is responsible for continuous querying of both parties to ensure data delivery). IP (Internet layer) organises data exchange over the Internet 17

18 IP address IP address = Network address + Device address IPv4 (classic version) uses 4 bytes to store the IP address. IPv6 (Extended version) uses 6 bytes

19 IP address of the network The first 1,2 or 3 bytes in the IP address store the network address The number of bytes per network address specifies network class: A, B or C

20 IP network mask How to determine the distribution of IP address between network address and device address? Network mask = number of bytes in the IP address of the network address Network address (3 bytes) Address of the device on the network (1 byte)

21 Network mask network class network mask network address Address range Number of bits per network address Number of networks Number of bits per host address Number of hosts in the network A B C X ^ X.X ^ 16 2 X.X.X ^ 8 2 = 254

22 IP address - an example of a simple network Network mask: Router address: Desktop address: Laptop address: Address of the network printer: Network address: Router Stationary WiFi comp Laptop Printer

23 Allocation of IP addresses IP addresses within one network cannot be repeated - each device should have its own IP address Methods of allocating IP addresses: Static - a fixed IP address is assigned to each host (e. g. by the network administrator) Simple method for small networks Speed of operation Dynamic - the address is automatically sent when the host is connected to the network Requires an additional device in the network: address server The host receives an IP address from the pool of free addresses each time DHCP protocol

24 DHCP Dynamic Host Configuration Protokol network protocol for configuring the addresses of computers in the network DHCP Server - the computer on which the DHCP service software is installed DHCP Client - computer or other network device using the services of a DHCP server Protocol does not depend on platform (!)

25 IP address translation Computer-orientated computer address (IP addresses) Man uses mnemonic host names DNS (Domain Name System) - protocol for translating hostnames in the network into IP addresses (and vice versa)

26 Static address translation Each device on the network has a fixed IP address Each computer stores a file with the addresses and names of the other hosts Each time you change the network configuration, you must change all files. Own computer name: localhost = Adres IP Hostname NetGear My Comp SCX4300printer

27 DNS protocol - dynamic address translation DNS Server: an additional device whose purpose is: Collection of address and host IP data on the network Retention of such data Provision of data on request: IP Search by host name Search for hostname after IP address (less frequently) Registration of the computer on the DNS server

28 Network resources Network equipment Computers, printers, streamers, plotters, scanners, cameras, etc. Folders of files shared over the network Services provided by servers HTTP, FTP, FTP, DNS, DHCP, SMTP, etc. directory services User login accounts, user data, resource search engine, etc.

29 Permissions to network resources Permissions allow users to use specific network resources Permissions are assigned to the object - the privilege holder (user, group, computer) Permissions are relates to a specific resource - an entity of allowances Permissions may apply locally or throughout the network (domain)

30 Network services File sharing Network printing Start-up of network applications Internet access Electronic mail Communication Remote work Directory services Problem: 1 computer, 1 network card, 1 IP address - can you provide/use multiple services? 30

31 Protocol ports Port - virtual service number of the service provided by the computer Ports solve the problem of multi-service interoperability on one IP address 16-bit integer number (2 bytes) = Standard ports: (well known ports) 21 - transfer of FTP files 80 - Web service IMAP mail, POP3 mail 443 HTTPS SQL Server 31

32 Ports (c.d.) Port 21 Port 80 Client application IP Server 32

33 Network software Network software - a type of computer software that enables the user to work in a group (network, domain) for the purpose: File sharing Communicating with other users Printer sharing Distributed calculations performed Internet access Remote operation 33

34 Network (server) operating system Functionality: Management of multiple resources and networked devices via protocols Management of users and their rights Network security assurance (privileges + security copies + access control) Management of network applications Network OS creates a virtual workstation for the user by providing him with applications and remote services (as opposed to locally run programs) 34

35 Network OS families Microsoft Windows Server 2003, 2008, 2012, 2016,. Linux / Unix There are many varieties (distribution) SUSE Linux Enterprise Server Ubuntu Server Red Hat Enterprise Linux Oracle Linux Server Etc. Nowell Network The 1990s of the 20th century. It now works in conjunction with Linux as an Open Enterprise Server 35

36 Requirements for network OS Reliability Operation for a long time without system restarting Resistance to application and user errors Maintenance-free operation Security Authorisation, audit, authentication of users Expansion Adapting to changing environments (new devices, protocols, hardware, standards and applications) Compatibility Support for multiple client systems (Windows, Linux, etc.) and different versions of the same system High performance and expandability 36

37 Popularity of networks OS * Data from

38 Network application Network application - a type of software running on a network, enabling the user to use selected network services The network application uses the specified protocol Depending on the architecture of interactivity with other computers in the network, they characterize network application architecture. 38

39 Network application architectures Architecture determines how network applications interact, how to offer and use services Peer-to-Peer Architecture Client-Server Architecture Multilayer architecture 39

40 Peer-to-Peer Architecture No central element exists Each computer may provide and use services and services The same service can be provided by multiple computers (or not at all) Error-resistant single computer Management problems Security issues 40

41 Client-Server Architecture It is based on the distribution of information processing tasks between service providers (servers) and service consumers (customers) Customers and servers can be both physical devices and also a software The method of communication between the server and the client is defined by the protocol 41

42 Client-server architecture: advantages Centralised management of network services Changes to server configurations do not require changes to workstations Centralised sharing and processing of data Joint multi-user access to network resources Server-based network configuration management Security Data on the server is better protected than on workstations Possibility of storing user data on the server with regular backups Central authentication of network users Combines multiple platforms and operational systems 42

43 Client-server architecture: disadvantages Server failure can block the entire network Server management requires highly qualified personnel. High server performance results in high purchase and maintenance costs. 43

44 Multi-layer architecture Multi-layer architecture is an extension of clientserver architecture in which data processing is performed on separate servers (layers). The most commonly used architecture is threelayer architecture. 44

45 Multi-layer architecture Presentation layers - application interface for the end user Authorisation of users Validation of customer input data Presentation of data received from the server and their processing, which does not require referencing of data to the server (simple sorting, searching, summarizing, etc.). Layer of business logic Conversion of the data entered by the user into queries to the database Transfer BD data to the presentation layer Implementation of complex data transformation algorithms Data layers Retention and processing of data It takes place on the server side of the database. 45

46 Multi-layer architecture - advantages and disadvantages Advantages of three-layer architecture Scalability Independence of component configurations of the different layers High safety High reliability Low customer requirements Disadvantages of three-layer architecture Higher cost of application development More complex installation and application configuration High cost of hardware and software 46