6. Introduction to Networking (cont'd)

Introduction to Data Communications
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6b. Telecommunications Components of The Big Picture

ISDN Integrated Services Digital Network
Private Branch Exchanges PBXs, Key Systems
Telcos AT&T, Bell Telephone, Sprint, Telus
DataPac & DataRoute packet switching and analog switching WAN protocols
Cell Relay Digital packet switching WAN protocol
Frame Relay Digital packet switching WAN protocol
X.25 Analog packet switching WAN protocol
ATM Asynchronous Transfer Mode WAN protocol
World Wide Web Hypertext based multimedia system
ADSL Asymmetrical digital subscriber line

6c. ISO OSI

The International Standards Organization (ISO) Open Systems Interconnect (OSI) is a standard set of rules describing the transfer of data between each layer. Each layer has a specific function. For example the Physical layer deals with the electrical and cable specifications.

The OSI Model clearly defines the interfaces between each layer. This allows different network operating systems and protocols to work together by having each manufacturere adhere to the standard interfaces. The application of the ISO OSI model has allowed the modern multiprotocol networks that exist today. There are 7 Layers of the OSI model:

7. Application Layer (Top Layer)
6. Presentation Layer
5. Session Layer
4. Transport Layer
3. Network Layer
2. Data Link Layer
1. Physical Layer (Bottom Layer)

The OSI model provides the basic rules that allow multiprotocol networks to operate. Understanding the OSI model is instrument in understanding how the many different protocols fit into the networking jigsaw puzzle. The OSI model is discussed in detail in Introduction to the ISO - OSI Model.

Introduction to Data Communications
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