The OSI Model Networking Basics Marty Rubenstein Presales Application Engineer [email protected] AutomaTech Solution Brief What is a network? • We all use networks in our everyday lives – Facebook – Linkedin – Internet • Getting data from one point to another efficiently and effectively • Networks include two or more intelligent devices connected to a communication system • Networks tend to grow with time as more and more capabilities are required and more endpoints are added. SB-XYZ-000A Month YEAR AutomaTech Solution Brief Basic Networking • As networks begin to be more integrated security becomes an issue. – Some communications we want to allow – Others we do not. • When networks get larger they become harder and more complex to manage. • More protocols required, and greater networking knowledge required to maintain. • Having a good foundation on the basics will help you understand the more complicated topics in the future. SB-XYZ-000A Month YEAR The OSI Model FTP, SNMP 7 ,SMTP, HTTP 6 5 4 3 2 1 Ethernet Rj-45/ Fiber/ Wireless The primary purpose is to allow different vendors networks to interoperate. Benefits of the OSI Model • It divides the network communication processes into smaller and simpler components, aiding component design and troubleshooting. • It allows for multivendor development through standardization of network components. • It encourages industry standardization by defining what functions occur at each layer of the model. • It allows various network hardware and software to communicate. • It prevents changes in one layer from effecting the other layers simplifying development. Data Encapsulation Layer Functions Data 7. Application Provide Network Process to applications Header Data 6. Presentation Format conversion, encryption/decryption Header Data 5. Session Interhost communication, logon/off 4. Transport Reliability, Error check, flow control 3. Network Logical Addressing, Routing 2. Data Link Physical Addressing, link error check 1. Physical Electrical signaling, cabling Data SB-XYZ-000A Month YEAR Host and Media Layers 7 Application 6 Presentation • Host Layers – These layers exist in the source 5 Session and destination host devices 4 Transport 3 Network • Media Layers 2 Data Link – These layers manage the information in the LAN or WAN 1 Physical between the source and destination devices SB-XYZ-000A Month YEAR Host to Host Flow Host 1 Host 2 7 Application 7 Application 6 Presentation 6 Presentation 5 Session 5 Session 4 Transport 4 Transport 3 Network Networking Device 3 Network L2 Switch 2 Data Link 2 Data Link 2 Data Link 1 Physical 1 Physical 1 Physical 10110110101 10110110101 SB-XYZ-000A Month YEAR Layer 7 - The Application Layer 7 Application Responsibilities: . This layer deals with networking 6 Presentation applications. Application Services like ftp, tftp, etc . Establishes availability of 5 Session communication partner . Where users actually communicate 4 Transport with the device 3 Network Used for applications specially written to run over the network 2 Data Link Examples: Email, Web browsers 1 Physical Telnet Protocol Data Unit: User Data SB-XYZ-000A Month YEAR OSI 7 Layers: Application Layer in Automation PROFInet FF HSE MODBUS/TCP BACNet/IP EtherNet/IP EIBNet/IP SB-XYZ-000A Month YEAR Presentation & Session Layers 7 Application • Presentation 6 Presentation – Responsible for protocol conversion, character conversions, data 5 Session encryption / decryption, and data compression 4 Transport • Session 3 Network – Establishes, maintains and ends sessions across the network 2 Data Link – Manages who can transmit data when and for how long 1 Physical SB-XYZ-000A Month YEAR Layer 4 -The Transport Layer 7 Application Responsibilities: • Provides virtual end-to-end links 6 Presentation between peer processes. • Fragmentation & Reassembly 5 Session • End-to-end flow control 4 Transport Provides: • TCP/UDP headers 3 Network • Error detection • Reliable communication 2 Data Link PDU 1 Physical • Protocol data unit is called a ‘Segment’ SB-XYZ-000A Month YEAR Layer 3 - The Network Layer 7 Application Responsibilities: • “Best Path Determination” based on 6 Presentation logical addresses (Routing) • Subnet flow control. (IP) 5 Session • Translation between different network types. 4 Transport Provides: 3 Network • IP packet headers • Virtual circuits 2 Data Link Example: Router 1 Physical PDU • Protocol data unit is the ‘Packet’ SB-XYZ-000A Month YEAR Layer 2 - The Data Link Layer 7 Application Responsibilities: • This layer provides reliable transit of 6 Presentation data across a physical link. • Makes decisions based on physical 5 Session addresses (usually MAC addresses). Provides: 4 Transport • Physical Addressing 3 Network • Data link control Example: Switch 2 Data Link PDU 1 Physical • Protocol data unit is a ‘Frame’ SB-XYZ-000A Month YEAR The Data Link Layer - The MAC sub-layer • Provides addressing and channel control mechanisms that make it possible for network nodes to communicate over a shared medium • Unique hardware Identifier MAC Address 0 0 : 9 0 : E 8 SB-XYZ-000A Month YEAR Layer 1 - The Physical Layer 7 Application Responsibility: 6 Presentation • Transmission of raw bits over a communication channel. 5 Session Provides: 4 Transport • Mechanical and Electrical interfaces • Maintains link between systems 3 Network • Timing Examples: Cat-5, Fiber 2 Data Link PDU – ‘Bits’ 1 Physical SB-XYZ-000A Month YEAR OSI Model vs TCP/IP Model 7 Application 6 Presentation Application 5 Session 4 Transport Transport 3 Network Internet 2 Data Link Network Access 1 Physical SB-XYZ-000A Month YEAR Thank you! 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