2. Cisco – Semester 1 – Chapter 2 Network Fundamentals And The OSI Model

3. Types of Networks LANs WANs MANs SANs Internet Intranet Extranet VPNs

4. History <50Semiconductor made smaller, more reliable computers possible 50sIC combined many transistors on one piece of semiconductor 60sMainframes and terminals were norm 70sSmaller computers; introduction of PC 80sIBM PC and shared data files

5. Network Protocols Protocols – rules for communication Organizations that set Protocols –IEEE –ANSI –TIA –EA –ITU formerly CCITT

6. LANS Cover limited geographic areas called campuses Provide many users access to high- bandwidth media Provide full-time connectivity Connect adjacent devices Types –Ethernet, Token Ring, FDDI

7. WANS Operate in wide geographic areas Allow end users to communicate real time Provide full-time remote services connected to local services Provide e-mail, WWW, FTP, and e-Commerce services Technologies –Modem, ISDN, DSL, Frame Relay, T1, E1, Sonet

8. MANS Not too important Area covered is larger than a campus Interconnect several LANs

9. SANs High-performance network that moves data between servers and storage resources Features –Performance –Availability –Scalability

10. VPN Builds a secure tunnel to enable two branch offices to communicate across Internet Types –Access VPNs – SOHO –Internet – link regional and remote office to headquarters –Extranet – link business partners to headquarters

11. VPN Advantages Provide privacy for TCP/IP applications Provides encryption services between clients and servers Provides mobility to employees with secure network access

12. International Standards Organization Interoperability The ISO recognized that there was a need to create a network model that would help network builders implement networks that could communicate and work together Released model in 1984 OSI reference model is networking scheme that supports networking standards

13. The 7 Layers 7Application 6Presentation 5Session 4Transport 3Network 2Data Layer 1Physical

14. Why Layers? Reduces complexity Standardizes interface Facilitates modular engineering Ensures interoperability Accelerates evolution Easier to teach and learn (or so they say)

15. Physical Layer – Layer 1 Defines the electrical and functional specifications for the link between end systems Defines voltage levels, physical data rates, maximum transmission distance, physical connections THINK MEDIA AND SIGNALS

16. Layer 2 – Data Link Provides reliable transit of data across a physical link Concerned with physical addressing (MAC) address), network topology, and media access, error notification, delivery of frames, and flow control THINK FRAMES AND MEDIA ACCESS CONTROL

17. Layer 3 – Network Layer Provides connectivity and path selection between two host systems THINK PATH SELECTION, ROUTING, AND ADDRESSING (logical or IP)

18. Layer 4 - Transport Provides a data transport service that shields the upper layers from transport implementation details Concerned with reliable transport between two hosts Establishes, maintains, and properly terminates virtual circuits Uses error detection-and-recovery and information flow control THINK QUALITY OF SERVICE AND RELIABILITY

19. Layer 5 - Session Establishes, manages, and terminates sessions between two communicating hosts. Provides its services to the presentation layer Synchronizes dialogue between the two hosts' presentation layers and manages their data exchange Provides data expedition, class of service, and exception reporting THINK DIALOG AND CONVERSATIONS

20. Layer 6 - Presentation Ensures the information sent is readable by receiving host Concerned with data structures & syntax Translates between multiple formats by using a common format Encodes, encrypts, and compresses THINK COMMON DATA FORMAT

21. Layer 7 - Application Provides network services to user applications DOES NOT provide services to any other OSI layer Provides services to applications outside the OSI model THINK BROWSERS

22. Layer Information In general each layer communicates with three other layers –The layer above –The layer below –The same layer in the peer host Know specifics of each layer –E.g. NetBuei – operates at layer 5

23. Encapsulation Wraps data with the necessary protocol information before sending to next layer and for network transit. Data receives headers (control information), trailers, and other information Data – Segments – Packets – Frames – Bits –THIS IS IMPORTANT (defines datagram at each layer)

24. Headers Control information placed before the data Adds address information, et. al. Exact format depends on layer

25. Layers and Encapsulation Presentation – Data Transport – Segments Network – Packets Data Link – Frames Physical - Bits

26. Protocols Set of rules that determines format and transmission of data; aka standards Different protocols for different layers PDU – Protocol Data Unit – exchange between peer layers

27. TCP/IP Transmission Control Protocol/Internet Protocol Makes data communication possible between any two computers, anywhere in the world Speed approaches speed of light WWW and Internet protocol – defacto standard

28. TCP/IP Layers Application Layer –Combines Application, Presentation, & Session Transport Layer –Same as OSI Transport Layer Internet Layer –Same as OSI Network Layer Network Access Layer –Includes Physical & Data Link; Includes LAN and WAN details

29. TCP/IP Protocols Application Layer –FTP, TFTP, HTTP, SMPT, DNS, TFTP, Telnet, Redirector Transport Layer –UDP and TCP Internet Layer –IP Network Access Layer –LAN and WAN technology used

30. Model Similarities Network professionals need to know both Both use layers Both are packet switched (not circuit switched) Both have similar transport and network layers

31. Model Differences TCP/IP application layer includes OSI presentation and session layers TCP/IP network access layer includes OSI data link and physical layers TCP/IP protocols are standards used to build Internet No networks are built around OSI protocols TCP/IP APPEARS simpler

32. Cisco Uses OSI Because Generic and protocol independent More details which makes it useful for teaching and learning More details which makes it useful for troubleshooting USE OSI MODEL but use TCP/IP PROTOCOLS