pace-it: the osi networking reference model

The OSI networking reference model.

Instructor, PACE-IT Program – Edmonds Community College

Areas of Expertise Industry Certifications

PC Hardware

Network Administration

IT Project Management

Network Design

User Training

IT Troubleshooting

Qualifications Summary

Education

M.B.A., IT Management, Western Governor’s University

B.S., IT Security, Western Governor’s University

Entrepreneur, executive leader, and proven manger with 10+ years of experience turning complex issues into efficient and effective solutions.

Strengths include developing and mentoring diverse workforces, improving processes, analyzing business needs and creating the solutions required— with a focus on technology.

Brian K. Ferrill, M.B.A.

The OSI networking reference model.PACE IT.

– A brief history.

– Networking reference models.

– OSI and TCP/IP comparison.

A brief history.The OSI networking reference model.

The OSI (Open Systems Interconnection) reference model is a conceptual model with two major components.

The first main component of the OSI networking reference model is an abstract model of networking—a seven layer model. The second is a set of specific protocols, which allow differing computing systems to communicate with one another despite their different architectures.



– Why a networking model was required.

» Early networks communicated using proprietary languages.

» Early networks could only communicate with like systems (e.g., IBM to IBM and DEC to DEC).

» The U.S. government desired a robust computer communications system that could survive disasters.

– TCP/IP reference model.» The Transmission Control Protocol/Internet Protocol

(TCP/IP) was published as the U.S. DoD standard in 1982.

» Adopted by the big players beginning in 1984.• AT&T moved the UNIX implementation to open source

in 1989.

– OSI reference model.» Published in 1983.» Defines the relationships between differing protocols. » Defines the relationships between differing protocols

and hardware.

Networking reference models.The OSI networking reference model.


– The OSI reference model.» Layer 1, the physical layer: standardizes the

electrical signal that networks use; also defines cable standards and how bits are placed on the physical media.

• Network cables and hubs are part of Layer 1.» Layer 2, the data link layer: responsible for

identifying the individual nodes (both sending and receiving); it also introduces an error correction method known as frame check sequence (FCS). It is composed of two sub-layers:

• The logical link control (LLC) layer is mainly responsible for flow control and error correction.

• The media access control (MAC) layer is mainly responsible for node addressing.

• Switches and bridges are Layer 2 devices.» Layer 3, the network layer: responsible for routing

functions between networks. It identifies nodes and networks.

• Routers are Layer 3 devices.


– OSI reference model continued.» Layer 4, the transport layer: responsible for

breaking the data into smaller pieces for the lower layers and for the actual data transport protocols—TCP and UDP (Transmission Control Protocol and User Datagram Protocol); the transport layer may be required to confirm the actual delivery of the data stream and error correction.

» Layer 5, the session layer: responsible for establishing the initial parameters between two systems. Sets up and tears down the communication channels.

» Layer 6, the presentation layer: responsible for taking data and converting it from a machine dependent language to a machine independent language. This is also the layer that has the main responsibility for encryption between networks.

» Layer 7, the application layer: responsible for the protocols that request services or functions from other systems. They may not be the actual application; for instance, IE is an application that uses HTTP (Hypertext Transfer Protocol) at Layer 7 to request Web pages.


– TCP/IP reference model.» Network interface layer (a.k.a. Link layer):

handles electrical signaling, flow control, error detection, and node addressing.

» Internet layer: handles routing functions and identifies network systems and nodes.

» Transport layer: handles breaking the data into more manageable chunks for lower layers; it is the layer responsible for the delivery method, either reliable or unreliable, and error correction for reliable delivery.

» Application layer: handles requests for services from applications, translation to machine independent languages and encryption. It also sets up and tears down sessions.

OSI and TCP/IP comparison.The OSI networking reference model.

While TCP/IP is the dominant model, most technicians communicate issues using the OSI model because it is more specific.

When problems occur—and they will—it is easier to resolve them with a more highly defined set of specifications (e.g., Layer 5 of the OSI model vs. the Application layer of the TCP/IP model).


Both the OSI and TCP/IP models are references only. It is not mandatory that they be followed.

Each developer and manufacturer determines its own method of implementing the reference model. While, in theory, there will never be a problem in communication between devices and systems, it is only a theory.


The OSI and TCP/IP networking models were created to allow disparate systems and networks to communicate easily between each other.

Topic

A brief history.

Summary

The OSI reference model has seven layers: physical, data link, network, transport, session, presentation, and application. The TCP/IP reference model has four layers: Network interface, Internet, Transport, and Application.

Networking reference models.

TCP/IP is the dominant model in use; however, the OSI model is more commonly used when discussing problems. Both models are references only; developers and manufacturers determine their own methods of implementing network models.

OSI and TCP/IP comparison.

What was covered.The OSI networking reference model.

THANK YOU!

This workforce solution was 100 percent funded by a $3 million grant awarded by the U.S. Department of Labor's Employment and Training Administration. The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability or ownership. Funded by the Department of Labor, Employment and Training Administration, Grant #TC-23745-12-60-A-53.

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pace-it: the osi networking reference model

Education

layer model

osi reference model

networking model

osi networking reference

tcpip reference model

network layer

transport layer

conceptual model