1. UNDERSTANDING THE HOST-TO-HOST COMMUNICATIONS MODEL - OSI LAYER & TCP/IP MODEL 1

2. Understanding Host-to-Host Communications – Older model Proprietary Application and combinations software controlled by one vendor – Standards-based model Multivendor software Layered approach

3. Using Layers to Describe Data Communication

4. OSI Model ( Open System Interconnect ) The OSI model is a layered model that describes how information moves from an application program running on one networked computer to an application program running on another networked computer. In essence, the OSI model prescribes the steps to be used to transfer data over a transmission medium from one networked device to another. The OSI model is a seven-layer model

5. The Physical Layer :- defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems Wires – (Coaxial, Twisted Pair, Cat5/6 or Fiber), Connectors – ( RJ11,45 etc ), Voltage & Date Rates etc.

6. Hubs Operate at Physical layer ABCD Physical All devices in the same collision domain All devices in the same broadcast domain Devices share the same bandwidth

7. Hubs: One Collision Domain More end stations means more collisions CSMA/CD is used

8. The Data Link Layer :- defines how data is formatted for transmission and how access to the physical media is controlled. Provides Connectivity and path selection between two host, No error correction.

9. Each segment has its own collision domain All segments are in the same broadcast domain Data Link Switches and Bridges Operate at Data Link Layer OR 123124

10. Switches Each segment has its own collision domain Broadcasts are forwarded to all segments Memory Switch

11. The Network Layer :- provides connectivity and path selection between two host systems that may be located on geographically separated networks. Reliable Transfer of Data across media, Network Topology, Error Notification, Flow Control

12. Routers: Operate at the Network Layer Broadcast control Multicast control Optimal path determination Traffic management Logical addressing Connects to WAN services

13. The Transport Layer :- segments data from the system of the sending host and reassembles the data into a data stream on the system of the receiving host.

14. The Session Layer :- establishes, manages, and terminates sessions between two communicating hosts

15. The Presentation Layer :- ensures that the information sent by the application layer of one system is readable by the application layer of another system.

16. The Application Layer :- provides network services to the applications of the user, such as e-mail, file transfer, and terminal emulation.

17. Data Encapsulation :- The information sent on a network is referred to as data or data packets. If one computer wants to send data to another computer, the data must first be packaged by a process called encapsulation.

18. Data De-Encapsulation :- When the remote device receives a sequence of bits, the physical layer at the remote device passes the bits to the data link layer for manipulation. This process is referred to as de-encapsulation.

19. Names for Data at Each Layer

20. Peer-to-Peer Communication

21. Introduction to TCP/IP 21

22. History and Future of TCP/IP The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions. Some of the layers in the TCP/IP model have the same name as layers in the OSI model.

23. TCP/IP Model

24. Application Layer Handles high-level protocols, issues of representation, encoding, and dialog control. The TCP/IP protocol suite combines all application related issues into one layer and ensures this data is properly packaged before passing it on to the next layer.

25. Application Layer Examples

26. Transport Layer Five basic services: Segmenting upper-layer application data Establishing end-to-end operations- Connection Oriented Sending segments from one end host to another end host Ensuring data reliability Providing flow control

27. Transport Layer Protocols

28. Reliable vs. Best-Effort Comparison

29. UDP Characteristics – Operates at transport layer of OSI and TCP/IP models – Provides applications with access to the network layer without the overhead of reliability mechanisms – Is a connectionless protocol – Provides limited error checking – Provides best-effort delivery – Has no data-recovery features

30. TCP Characteristics – Transport layer of the TCP/IP stack – Access to the network layer for applications – Connection-oriented protocol – Full-duplex mode operation – Error checking – Sequencing of data packets – Acknowledgement of receipt – Data-recovery features

31. Mapping Layer 4 to Applications

32. Establishing a Connection

33. Three-Way Handshake CTL = Which control bits in the TCP header are set to 1

34. TCP Acknowledgment

35. TCP Sequence and Acknowledgment Numbers

36. Flow Control

37. Fixed Windowing

38. TCP Sliding Windowing

39. Internet Layer The purpose of the Internet layer is to send packets from a network node and have them arrive at the destination node independent of the path taken.

40. Network Access Layer The network access layer is concerned with all of the issues that an IP packet requires to actually make a physical link to the network media. It includes the LAN and WAN technology details, and all the details contained in the OSI physical and data link layers.

41. Comparing the OSI Model and TCP/IP Model

42. Similarities of the OSI and TCP/IP Models Both have layers. Both have application layers, though they include very different services. Both have comparable transport and network layers. Packet-switched, not circuit-switched, technology is assumed. Networking professionals need to know both models.

43. Differences of the OSI and TCP/IP Models TCP/IP combines the presentation and session layer into its application layer. TCP/IP combines the OSI data link and physical layers into one layer. TCP/IP appears simpler because it has fewer layers. TCP/IP transport layer using UDP does not always guarantee reliable delivery of packets as the transport layer in the OSI model does.