YASKAWA VIPA System SLIO Manual

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YASKAWA VIPA System SLIO Manual Manual pdf 215 page image

9.2 Basics - ISO/OSI reference modelThe ISO/OSI reference model is based on a proposal that was developed by the Interna-tional Standards Organization (ISO). This represents the first step towards an interna-tional standard for the different protocols. It is referred to as the ISO-OSI layer model. OSIis the abbreviation for Open System Interconnection, the communication between opensystems. The ISO/OSI reference model does not represent a network architecture as itdoes not define the services and protocols used by the different layers. The model simplyspecifies the tasks that the different layers must perform. All current communication sys-tems are based on the ISO/OSI reference model, which is defined by the ISO 7498standard. The reference model structures communication systems into 7 layers that coverdifferent communication tasks. In this manner the complexity of the communicationbetween different systems is divided amongst different layers to simplify the task.The following layers have been defined:n Layer 7 - Application Layern Layer 6 - Presentation Layern Layer 5 - Session Layern Layer 4 - Transport Layern Layer 3 - Network Layern Layer 2 - Data Link Layern Layer 1- Physical LayerDepending on the complexity and the requirements of the communication mechanisms acommunication system may use a subset of these layers.The bit communication layer (physical layer) is concerned with the transfer of data bits viathe communication channel. This layer is therefore responsible for the mechanical, elec-trical and the procedural interfaces and the physical communication medium locatedbelow the bit communication layer:n Which voltage represents a logical 0 or a 1?n The minimum time the voltage is present to be recognized as a bit.n The pin assignment of the respective interface.This layer performs error-checking functions for bit strings transferred between two com-municating partners. This includes the recognition and correction or flagging of communi-cation errors and flow control functions. The security layer (data link layer) converts rawcommunication data into a sequence of frames. This is where frame limits are inserted onthe transmitting side and where the receiving side detects them. These limits consist ofspecial bit patterns that are inserted at the beginning and at the end of every frame. Thesecurity layer often also incorporates flow control and error detection functions. The datasecurity layer is divided into two sub-levels, the LLC and the MAC level. The MAC (MediaAccess Control) is the lower level and controls how senders are sharing a single transmitchannel. The LLC (Logical Link Control) is the upper level that establishes the connectionfor transferring the data frames from one device into the other.The network layer is an agency layer. Business of this layer is to control the exchange ofbinary data between stations that are not directly connected. It is responsible for the log-ical connections of layer 2 communications. Layer 3 supports the identification of thesingle network addresses and the establishing and disconnecting of logical communica-tion channels. Additionally, layer 3 manages the prior transfer of data and the error pro-cessing of data packets. IP (Internet Protocol) is based on Layer 3.Layer 4 connects the network structures with the structures of the higher levels bydividing the messages of higher layers into segments and passes them on to the networklayer. Hereby, the transport layer converts the transport addresses into networkaddresses. Common transport protocols are: TCP, SPX, NWLink and NetBEUI.OverviewLayer 1 - Bit communica-tion layer (physical layer)Layer 2 - Security layer(data link layer)Layer 3 - Network layerLayer 4 - Transport layerVIPA System SLIO Deployment PG/OP communication - productiveBasics - ISO/OSI reference modelHB300 | CPU | 013-CCF0R00 | en | 19-30 215