OSI (Open Systems Interconnection) Model The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The OSI Model is a conceptual, seven-layered model of how networks work. It tells us that how data is going through one computer to another computer, and also it simplifies to troubleshoot the network issues. A reference model to make sure products of different vendors would work together. HISTORY In the late 1970s, two projects began independently, with the same goal: to define a unifying standard for the architecture of networking systems. One was administered by the International Organization for Standardization (ISO), while the other was undertaken by the International Telegraph and Telephone Consultative Committee, or CCITT (the abbreviation is from the French version of the name). These two international standards bodies each developed a document that defined similar networking models. OSI (Open Source Interconnection) 7 Layer Model
The Open Systems Interconnection Model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The OSI Model is a conceptual, seven-layered model of how networks work. It tells us that how data is going through one computer to another computer, and also it simplifies to troubleshoot the network issues.
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OSI (Open Systems Interconnection) Model
The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and
standardizes the internal functions of a communication system by partitioning it into abstraction layers.
The OSI Model is a conceptual, seven-layered model of how networks work. It tells us that how data is
going through one computer to another computer, and also it simplifies to troubleshoot the network
issues.
A reference model to make sure products of different vendors would work together.
HISTORY
In the late 1970s, two projects began independently, with the same goal: to define a unifying standard
for the architecture of networking systems. One was administered by the International Organization for
Standardization (ISO), while the other was undertaken by the International Telegraph and Telephone
Consultative Committee, or CCITT (the abbreviation is from the French version of the name). These two
international standards bodies each developed a document that defined similar networking models.
OSI (Open Source Interconnection) 7 Layer Model
OSI (Open Systems Interconnection) Model
In 1983, these two documents were merged together to form a standard called The Basic Reference
Model for Open Systems Interconnection. That's a mouthful, so the standard is usually referred to as the
Open Systems Interconnection Reference Model, the OSI Reference Model, or even just the OSI Model.
It was published in 1984 by both the ISO, as standard ISO 7498, and the renamed CCITT (now called the
Telecommunications Standardization Sector of the International Telecommunication Union or ITU-T) as
standard X.200.
The concept of a seven-layer model was provided by the work of Charles Bachman, Honeywell
Information Services.
Network Layer Interaction
Network Layer Interconnection
OSI (Open Systems Interconnection) Model
Packet Structure
OSI LAYER
1. Physical Layer
Packet Description
Physical Layer
OSI (Open Systems Interconnection) Model
Function of Layer 1
It defines the electrical and physical specifications of the data connection. It defines the
relationship between a device and a physical transmission medium (e.g., a copper or fiber
optical cable). This includes the layout of pins, voltages, line impedance, cable
specifications, signal timing, hubs, repeaters, network adapters, host bus adapters (HBA
used in storage area networks) and more.
It defines the protocol to establish and terminate a connection between two directly
connected nodes over a communications medium.
It may define the protocol for flow control.
It defines transmission mode i.e. simplex, half & full duplex.
It defines topology.
It defines a protocol for the provision of a (not necessarily reliable) connection between
two directly connected nodes, and the modulation or conversion between the
representation of digital data in user equipment and the corresponding signals
transmitted over the physical communications channel. This channel can involve physical
cabling (such as copper and optical fiber) or a wireless radio link.
Protocol
Telephone network modems- V.92
IRDA physical layer
USB physical layer
EIA RS-232, EIA-422, EIA-423, RS-449, RS-485
Ethernet physical layer Including 10BASE-T, 10BASE2, 10BASE5, 100BASE-TX, 100BASE-FX,
100BASE-T, 1000BASE-T, 1000BASE-SX and other varieties
Varieties of 802.11 Wi-Fi physical layers
DSL
ISDN
T1 and other T-carrier links, and E1 and other E-carrier links
SONET/SDH
Optical Transport Network (OTN)
GSM Um air interface physical layer
Bluetooth physical layer
ITU Recommendations: see ITU-T
IEEE 1394 interface
TransferJet physical layer
Etherloop
ARINC 818 Avionics Digital Video Bus
OSI (Open Systems Interconnection) Model
G.hn/G.9960 physical layer
CAN bus (controller area network) physical layer
Mobile Industry Processor Interface physical layer
2. Data Link Layer
The Data-Link layer contains two sub layers that are described in the IEEE-802 LAN standards:
Media Access Control (MAC) layer- responsible for controlling how computers in the
network gain access to data and permission to transmit it.
Logical Link Control (LLC) layer- control error checking and packet synchronization.
Data Link Layer
OSI (Open Systems Interconnection) Model
Function of Layer 2
Link establishment and termination: establishes and terminates the logical link between
two nodes.
Frame traffic control: tells the transmitting node to "back-off" when no frame buffers are