Networking Version2 10/27/2015Slide 1 Format Layered models of processes The seven layers OSI Model Network Requirements Network Topology

Networking Version2 10/27/2015Slide 2 ISO OSI Reference Model International Standards Organisation the standards body Open Systems Interconnection seven layer reference model tasks of a communications system broken down into manageable parts organised into a hierarchical architecture.

Networking Version2 10/27/2015Slide 3 OSI model – Why bother? Real-world network protocols don’t implement the OSI seven layer protocol stack model But nearly all network protocols are based on a simplified layered model The layered model helps us think about the many processes involved in communicating over networks A good model provides support for thinking

Networking Version2 10/27/2015Slide 4 Communication Between Two Systems

Networking Version2 10/27/2015Slide 5 ISO OSI Reference Model

Networking Version2 10/27/2015Slide 6 ISO OSI Reference Model Each layer takes data (a Protocol Data Unit(PDU)) from the layer above Each layer processes and encapsulates the data into a new PDU Each layer passes the new PDU to the lower layer

Networking Version2 10/27/2015Slide 7 Data Transformation

Networking Version2 10/27/2015Slide 8 Encapsulation Physical Layer MAC Layer Network Layer (IP) Transport Layer (TCP) ----DATA---- TCP - HEAD ----DATA----TCP - HEADIP - HEAD ----DATA----TCP - HEADIP - HEADMAC - HEAD Data field TCP PDU IP Packet MAC frame CRC

Networking Version2 10/27/2015Slide 9 The Seven Layer Model Please do not throw sausage pizza away! All People Seem To Need Data Processing At the top, the Application layer provides OS services for application software At the bottom, the Physical layer deals with wiring issues Application Presentation Session Transport Network Data link Physical

Networking Version2 10/27/2015Slide 10 TCP / IP Reference model Existed before OSI model Uses TCP - Transmission Control Protocol IP Internet Protocol

Networking Version2 10/27/2015Slide 11 OSI ModelTCP/IP Transmission Control Protocol/Internet Protocol (TCP/IP)

Networking Version2 10/27/2015Slide 12

Networking Network Requirements High data rate ? Bank transaction Web browsing Low delay ? live video/ audio links routine backup Version2 10/27/2015Slide 13

Networking Version2 10/27/2015Slide 14 Network Requirements Low (zero) error rate ? video signal bank account details Guaranteed Connection safety critical control internet phone

Networking Version2 10/27/2015Slide 15 Mesh Topology Fully connected 3 lines : 2 ports per machine

Networking Version2 10/27/2015Slide 16 Mesh Topology Fully connected 6 lines : 3 ports per machine

Networking Version2 10/27/2015Slide 17 Mesh Topology Fully connected 10 lines : 4 ports per machine

Networking Version2 10/27/2015Slide 18 Mesh Topology Fully connected systems use too much wiring. Each computer may need an interface for each connection. Not a practical system.

Networking Version2 10/27/2015Slide 19 Star Topology STAR

Networking Version2 10/27/2015Slide 20 Ring Topology RING

Networking Version2 10/27/2015Slide 21 Bus Topology BUS

Networking Version2 10/27/2015Slide 22 Conclusion We have discussed:- Standard “root concepts” of networking Layered models of processes and layers in our conceptual model of networking Why protocols are required for interoperability Brief of the seven layers of the OSI model and encapsulation Basics of Network Requirements Types of network topologies