1. CHAPTER 2
THE OSI MODEL

2. 2.1 General Model of Communication
CHAPTER 2
2.1 General Model of Communication

3. 2.1.1 Using layers to analyze problems in a flow of materials
Analyzing Network in Layers
What is flowing?
What different forms flow?
What rules govern flow
Where does the flow occur?

4. 2.1.1 Using layers to analyze problems in a flow of materials

5. 2.1.2 Source, Destination, and Data Packets
PC PLATFORM
SOURCE
MACINTOSH PLATFORM
DESTINATION
Data Packet
A data packet is a logically grouped unit of information that moves between computer systems. It includes the source information along with other elements that are necessary in order to make communication possible and reliable with the destination device.
The source address in a packet specifies the identity of the computer that sends the packet.
The destination address specifies the identity of the computer that finally receives the packet.

6. 2.1.3 MEDIA
The plural form of medium is media. In networking, a medium is a material through which data packets travel. It could be any of the following materials:
Telephone wires
Category 5 UTP (used for 10BASE-T Ethernet)
Coaxial cables (used for cable TV)
Optical fibers (thin glass fibers that carry light)

7. 2.1.3 MEDIA

8. 2.1.3 MEDIA

9. 2.1.3 MEDIA

10. 2.1.3 MEDIA

11. 2.1.3 MEDIA
Communication without some type of wires or cables is called wireless or free-space communication. This is possible using electromagnetic (EM) waves.

12. 2.1.4 PROTOCOL
A Protocol is a set of rules that make communication on a network more efficient.
Protocol is a set of rules, or an agreement, that determines the format and transmission of data.

13. 2.1.5 The Evolution of ISO Networking Standards
The early 1980's saw tremendous increases in the numbers and sizes of networks.
By the mid-1980's, these companies began to experience growing pains from all the expansions they had made. It became harder for networks that used different specifications and implementations to communicate with each other. They realized that they needed to move away from proprietary networking systems.

14. 2.1.5 The Evolution of ISO Networking Standards
Proprietary systems are privately developed, owned, and controlled. In the computer industry, proprietary is the opposite of open. Proprietary means that one or a small group of companies controls all usage of the technology. Open means that free usage of the technology is available to the public.

15. 2.1.5 The Evolution of ISO Networking Standards
To address the problem of networks being incompatible and unable to communicate with each other, the International Organization for Standardization (ISO) researched network schemes
As a result of this research, the ISO created a network model that would help vendors create networks that would be compatible with, and operate with, other networks.

16. 2.1.5 The Evolution of ISO Networking Standards
The OSI reference model released in 1984, was the descriptive scheme they created. It provided vendors with a set of standards that ensured greater compatibility and interoperability between the various types of network technologies that were produced by the many companies around the world.

17. 2.1.5 The Evolution of ISO Networking Standards
The OSI model is like a blue print for the building of a car: it specifies the functions of each layer

18. 2.2 The OSI REFERENCE MODEL
CHAPTER 2
2.2 The OSI REFERENCE MODEL

19. 2.2.1 The purpose of the OSI reference Model
This separation of networking functions is called layering.

20. 2.2.2 The seven layers of the OSI reference model
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Host layers: Provide accurate data delivery between computers
Media layers: Control Physical delivery of messages over the network

21. 2.2.2 The seven layers of the OSI reference model
All
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
People
Seem To
Need
Data
Processing

22. 2.2.2 The seven layers of the OSI reference model
Networks processes to applications
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Data representation
Interhost communication
End-to-end connections
Addresses and best path
Access to media
Binary Transmission

23. 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 7: The Application Layer     The application layer is the OSI layer that is closest to the user; it provides network services to the user's applications. It differs from the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model.
BROWSER

24. 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 6: The Presentation Layer
The presentation layer ensures that the information that the application layer of one system sends out is readable by the application layer of another system. Responsible for compression and encryption
DATA FORMAT

25. 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 5: The Session Layer
the session layer establishes, manages, and terminates sessions between two communicating hosts.
DIALOGUES

26. 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 4: The Transport Layer The transport layer segments data from the sending host's system and reassembles the data into a data stream on the receiving host's system.
QUALITY OF SERVICE
RELIABILITY

27. 2 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 3: The Network Layer The network layer is a complex layer that provides connectivity and path selection between two host systems that may be located on geographically separated networks.
ADDRESSING
PATH SELECTION

28. 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 2: The Data Link Layer The data link layer provides reliable transit of data across a physical link. In so doing, the data link layer is concerned with physical (as opposed to logical) addressing, network topology, network access, error notification, ordered delivery of frames, and flow control.
FRAMES
MEDIA ACCESS CONTROL

29. 2 2.2.3 The functions of each layer
Application
Presentation
Session
Transport
Network
Data Link
Physical 7 6 5 4 3 2 1
Layer 1: The Physical Layer The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.
SIGNALS
MEDIA

30. Analogy 2.2.4 Encapsulation 1 2 3 4 5
Encapsulation wraps data with the necessary protocol information before network transit.
Analogy 1 2 3 4 5

31. 2.2.4 Encapsulation
Header – Control Information placed before the data. It tells the network where to send the data packet.
Trailer – Control Information added after the data when encapsulation data for network transmission

32. Five Conversion Steps:
Build the data
Package the data for end-to-end transport
Add the network address to the header
Add the local address to the data link header
Convert to bits for transmission

33. 2.2.4 Names for data at each layer of the OSI model
In order for data packets to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination. This form of communication is referred to as Peer-to-Peer Communications.

34. 2.2.4 Names for data at each layer of the OSI model
Protocol data unit. In the OSI model, the generic name for the structure of data (messages) sent between peer layers of communicating network devices.

35. 2.3 Comparison of the OSI Model and the TCP/IP Model
CHAPTER 2
2.3 Comparison of the OSI Model and the TCP/IP Model

36. 2.3.1 The TCP/IP reference model
Transmission Control Protocol/Internet Protocol (TCP/IP). The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light.

37. 2.3.2 The Layers of the TCP/IP reference model
The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions, even a nuclear war.
The TCP/IP Model
Application
Transport
Internet
Network Access

38. 2.3.2 The Layers of the TCP/IP reference model
The TCP/IP Model
Application Layer The designers of TCP/IP felt that the higher level protocols should include the session and presentation layer details. They simply created an application layer that handles high-level protocols, issues of representation, encoding, and dialog control. The TCP/IP combines all application-related issues into one layer, and assures this data is properly packaged for the next layer. This is also referred to as the process layer.
Application
Transport
Internet
Network Access

39. 2.3.2 The Layers of the TCP/IP reference model
The TCP/IP Model
Application
Transport Layer The transport layer deals with the quality-of-service issues of reliability, flow control, and error correction.
Transport
Internet
TCP
Network Access

40. 2.3.2 The Layers of the TCP/IP reference model
The TCP/IP Model
Application
Internet Layer The purpose of the Internet layer is to send source packets from any network on the internetwork and have them arrive at the destination independent of the path and networks they took to get there.
Transport
Internet
Network Access IP

41. 2.3.2 The Layers of the TCP/IP reference model
The TCP/IP Model
Application
Network Access Layer
It is also called the host-to-network layer. It is the layer that is concerned with all of the issues that an IP packet requires to actually make a physical link, and then to make another physical link. It includes the LAN and WAN technology details, and all the details in the OSI physical and data link layers.
Transport
Internet
Network Access

42. 2.3.3 TCP/IP Protocol Graph

43. 2.3.4 Comparison of the OSI model and the TCP/IP model

44. 2.3.4 Comparison of the OSI model and the TCP/IP model
SIMILIRATIES
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
DIFFERENCES
TCP/IP combines the presentation and session layer issues 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 protocols are the standards around which the Internet developed