1. Internet and Intranet Fundamentals Class 1 Sessions A & B

2. Topics Background Material –Open Systems Interconnection (OSI) Networking Model

3. Open Systems Interconnection Model Develop in early 80s –ISO - International Organization for Standardization ISO 7498 –ITU-T - International Telecommunications Union, Telecommunications Standards Sector CCITT Recommendation X.200 http://www.itu.int/ Layered Model

4. Open Systems Interconnection Model Seven Layers –Application (S/W) –Presentation (S/W) –Session (S/W) –Transport (S/W) –Network (S/W and H/W) –Data Link (F/W and H/W) –Physical (H/W)

5. Open Systems Interconnection Model Each layer should –represent a different level of abstraction –perform a well-defined function –be developed with internationalization in mind –minimize information flow across its boundaries to other layers –optimal number: enough layers to partition functions well but small enough to remain tractable

6. OSI Application Layer Application and User Interfaces File Transfer E-Mail Database Access Program to Program Communication http, ftp, gopher, smtp, telnet

7. OSI Presentation Layer Data Transformations Data Syntax Syntax Conversion Data Structure Text Compression SSL –secure sockets layer –straddles this and next lower layer

8. OSI Session Layer Application Interface to Network Establishing Connections Session Control Sometimes Merged with Transport Layer

9. OSI Transport Layer Host-to-Host Layer Error Free End-to-End Connections –virtual connections –doesn’t know about intervening routers TCP in TCP/IP Often Implemented in Operating System

10. OSI Network Layer Communications Subnet Layer Network Routing Packets Congestion and Flow Control Accounting IP in TCP/IP Typically Implemented as I/O Driver

11. OSI Data Link Layer Breaks Up Input Data from Network Layer and Transmits as Data Frames Typically an Interface Card with Firmware –Ethernet card Acknowledgement Error Handling –Retransmission Flow Control

12. OSI Physical Layer Transmits Raw Bits Includes Communication Channel –copper wire –fiber –microwave Signaling Levels –voltages, timing Pin Configurations

13. OSI Reference Model Application Presentation Session Network Transport Data Link Physical Application Presentation Session Network Transport Data Link Physical Network Data Link Physical

14. OSI vs. TCP/IP Models Application Presentation Session Network Transport Data Link Physical Application Network Transport Network Interface OSITCP/IP