1. Networks – Network Architecture Network architecture is specification of design principles (including data formats and procedures) for creating a network configuration to ensure the reliable transfer of information Network architecture is represented as a set of network protocols Protocol is a set of definitions and rules used for communication between function units in different system (in the general sense) Protocol is „the speech in the same language“ enabling variable function modules to communicate each to other Networks - NetworkArchitecture1

2. Networks – Network Architecture The basic standard for network architectures is Open Systems Interconnection Reference Model (OSI) The OSI Model defines internetworking in terms of a vertical stack of seven layers. –The upper layers (7 to 4) of the OSI model represent software that implements network services like file transfer, mail service, connection and remote session management and so on. –The lower layers (3 to 1) of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control 2Networks - NetworkArchitecture OSI model remains a practical framework that use many of today's key network technologies

3. Networks – Network Architecture 3Networks - NetworkArchitecture 76543217654321 Upper Layers Lower Layers

4. Networks – Network Architecture The layers functionality description (upper layers) Layer 7 (The Application layer) is the layer at which communication partners are identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Application layer enables clients the access to the network services. Layer 6 (The Presentation layer) converts incoming and outgoing data from one presentation format to another Layer 5 (The Session layer) sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. Layer 4 (The Transport layer) manages the end-to-end control (for example, determining whether all packets have arrived) and error checking. It ensures complete data transfer. 4Networks - NetworkArchitecture

5. Networks – Network Architecture The layers functionality description (lower layers) Layer 3 (The Network layer) handles the routing of the data, i.e. sending packets in the right direction toward the right destination. Layer 2 (The Data-link layer) provides error control and synchronization for the physical level. Layer 1 (The Physical layer) conveys the bit stream through the network as the signals. It provides the hardware means of sending and receiving data. 5Networks - NetworkArchitecture

6. Networks – Network Architecture OSI Reference Model 6Networks - NetworkArchitecture

7. Networks – Network Architecture In network protocols, two concepts are fundamental –Messages –Encapsulation Messages between entities consit of two parts: header and payload. Data from upper layer are put into the payload. The header contains control information used to synchronize with the remote peer. The header contains “instructions” that tell the remote peer what to do with the message. Encapsulation is sending a data packet in one format within a packet of another format 7Networks - NetworkArchitecture

8. 8 Networks – Network Architecture

9. TCP/IP (Transmission Control Protocol/Internet Protocol) Architecture TCP/IP is the favorite communication protocol suite of the worldwide network Internet TCP/IP protocol can be used also for communications via private networks called intranets and in extranets too. Each computer on Internet is provided with TCP/IP implementation operation system. The TCP/IP protocol implementation is the first requirement for enabling an access to the Internet from any computer. 9Networks - NetworkArchitecture

10. Networks – Network Architecture Implementation of TCP/IP architecture in the network operating system 10Networks - NetworkArchitecture

11. Networks – Network Architecture TCP/IP Protocol Suit is a four-layered protocol suite Relation TCP/IP to the OSI Reference Model Location of the important protocols inthe TCP/IP layers 11Networks - NetworkArchitecture

12. Networks – Network Architecture The TCP/IP protocols functionality Network interface provides the access to the transmission media and the control of the data links. IP protocol supports communication between network devices and provides routing facilities based on the implementation of a global addressing scheme. Transport layer provides data transport services between two end-user processes. The transport layer includes two transport protocols: –TCP protocol –UDP protocol 12Networks - NetworkArchitecture

13. Networks – Network Architecture Application layer provides the users access to the Internet services –There are many different protocols belonging to the application layer. Some of them use the TCP transport service and others use the UDP transport service –Most of application protocols are based on the client/server communication model. –The client/server model of communication is that, in which a one computer (a client) requests and is provided with a service (such as sending a Web page) by another computer (by a server). 13Networks - NetworkArchitecture

14. Networks – Network Architecture Examples of user application layer protocols, which enable us to use the Internet services The World Wide Web's Hypertext Transfer Protocol (HTTP) enabling users access to WWW information system The File Transfer Protocol (FTP) for files transfer from one file system to another one The Telnet Protocol which lets users to logon to remote computers The Simple Mail Transfer Protocol (SMTP) supporting electronic mail service The Internet Message Access Protocol (IMAP) and Post Office Protocol (POP) enabling users access to mailboxes from remote machines 14Networks - NetworkArchitecture

15. Networks – Network Architecture The addressing scheme implemented in TCP/IP IP addressing schema allows for over a billion devices to be uniquely identified and contacted across a network IP address is a 32-bit number that identifies both unique network number and a host number, which is unique within the network (123.56.118.1, 195.178.82.112……) Since networks vary in size, there are 3 different address formats or classes –Class A – for very large networks (up to 16 M nodes) –Class B – for large networks (up to 65 k nodes) –Class C – for middle to small networks (up to 250 nodes) 15Networks - NetworkArchitecture

16. Networks – Network Architecture Internet Domain Name System The numerical IP address is usually represented by a name or series of names called the domain name A domain name locates an organization or other entity on the Internet. For example, the domain name akela.mendelu.cz locates an Internet address for "mendelu.cz" and a particular host server named „akela" at Internet point 195.113.194.135 All domain names binding to IP addresses create hierarchical administrative name space supporting Internet domain name service (DNS) 16Networks - NetworkArchitecture

17. Networks – Network Architecture Domain names need to be converted to IP addresses, as this is required by lower layer protocols (IP protocol). The conversion of domain names to IP addresses is performed by function implementing DNS (Domain Name System) protocol. Since an implementation of the DNS protocol is built into every network application program, the conversion is fully transparent to end users. 17Networks - NetworkArchitecture

18. Networks – Network Architecture Routing Routing is the process of moving information across an Internet from the source to destination. Along the way, at least one intermediate device is typically encountered. Such a device is called a router 18Networks - NetworkArchitecture

19. Networks – Network Architecture Router Router is a device, which connects two physically different segments of the particular network or two or more different networks. Router is usually a specific device. If a router joins n different networks, it has n different network interfaces and forwards data packets between them. A router takes routing information from the routing table. It has entry for each identified route within common network. 19Networks - NetworkArchitecture

20. Routers (Cisco Systems, Inc.) Router logo (Cisco Systems, Inc.) Networks - NetworkArchitecture20 Networks – Network Architecture

21. Networks - NetworkArchitecture21 Routing path – „the best path“ from source to destination Networks – Network Architecture

22. 22Networks - NetworkArchitecture Routing in the context of the OSI Model