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ISO/OSI Model. Open Systems Interconnection Developed by the International Organization for Standardization (ISO) Seven layers A theoretical system delivered too late! TCP/IP is the de facto standard.
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ISO/OSI Model • Open Systems Interconnection • Developed by the International Organization for Standardization (ISO) • Seven layers • A theoretical system delivered too late! • TCP/IP is the de facto standard
OSI LayersAll People Seem To Need Data ProcessingPlease Do Not Throw Sausage Pizza Away. • Application • Presentation • Session • Transport • Network • Data Link • Physical
Communications Across Layers • Peer to peer processes • Each layer only sees it’s peer layer • Virtual communication between layers
Communication Between Layers Envelopes – Each layer wraps the information passed to it in an appropriate header and trailer if required. Headers are added to layers 2-6 Trailers added to layer 2
OSI Layers Figure 3-2
Organization of Model • Network Support Layers • Deal with the physical aspects of moving data from one device to another • Layer 1 Bits • Layer 2 Packets and Addressing/Flow control • Layer 3 Logical Addressing/Routing
Organization of Model • Layer 4 – Transport • Reliable delivery of messages • Service point addressing – port address • Segmentation and re-assembly • Connection control • Flow Control • Error Control
Organization of Model • Layer 5 – Session • Dialog Controller • Synchronization • Layer 6 - Presentation • Translation • Encryption • Compression
Organization of Model • Layer 7 – Application • User Access to Network Services • X.400 Message handling – email • X.500 Directory Services • FTAM
An Exchange Using the OSI Model Figure 3-3
Figure 3-4 Physical Layer
Figure 3-5 Data Link Layer
Figure 3-6 Data Link Layer Example
Figure 3-7 Network Layer
Network Layer Example Figure 3-8
Figure 3-8-continued Network Layer Example
Transport Layer Figure 3-9
Figure 3-10 Transport Layer Example
Figure 3-10-continued Transport Layer Example
Figure 3-11 Session Layer
Figure 3-12 Presentation Layer
Figure 3-13 Application Layer
Figure 3-14 Summary of Layer Functions The McGraw-Hill Companies, Inc., 1998 WCB/McGraw-Hill