Networks – Network Architecture Network architecture is specification of design principles (including data formats and procedures) for creating a network

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 - NetworkArchitecture 1

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

Networks – Network Architecture


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Upper Layers

Lower Layers

Networks – Network ArchitectureThe 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.



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.



OSI Reference Model



• 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





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.



Implementation of TCP/IP architecture in the network operating system


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


Networks – Network ArchitectureThe 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


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).



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



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)



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)



• 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.


Networks – Network ArchitectureRouting

•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



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.


• Routers (Cisco Systems, Inc.)

• Router logo (Cisco Systems, Inc.)




• Routing path – „the best path“ from source to destination




Routing in the context of the OSI Model

Documents

Networks – Network Architecture Network architecture is specification of design principles (including data formats and procedures) for creating a network