OSI Layers
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Transcript of OSI Layers
OSI LAYERS
Kashif Latif
OSI - THE MODEL A layer model (Open Systems
Interconnection) Each layer performs a subset of the
required communication functions Each layer relies on the next lower layer
to perform more primitive functions Each layer provides services to the next
higher layer Changes in one layer should not require
changes in other layers
LAYERS- MODEL
WHY LAYERS…?
A layered architecture allows us to discuss a well-defined ,specific part of a large and complex system.
Breaks down the complex operation of networking into simple elements.
Helps developers in developing software. It is also much easier to change the implementation
of the service provided by the layer. Helps in troubleshooting and identifying the problem. It provides a way to understand how an internet work
operates. Task broken into subtasks
REAL TIME EXAMPLE
PHYSICAL LAYER The physical layer is responsible for transmitting
individual bits from one node to the next. The physical layer defines Media type ,Connector
type and Signaling type . Physical layer defines the following characteristics of
interface between data transmission device (e.g. computer) and transmission medium or network.
Mechanical Electrical Functional Procedural
Representation of bits Data rates
PHYSICAL LAYER
DATA LINK LAYER Data link layer is responsible for activating,
maintaining and deactivating a reliable link between two nodes.
The data link layer is responsible for transmitting frames from one node to another. 1. Framing2. Physical Addressing3. Flow control4. Error control5. Access control
DATA LINK LAYER
NETWORK LAYER
The network layer is responsible for the delivery of packets from the original source to the final destination.
1. Data is in the form of Packets2. Logical (IP) Addressing 3. Routing4. Main protocols at this layer are IP ,ICMP ,ARP
NOTE
The network layer is responsible for the source to destination delivery of a packet possibly across multiple networks.
Where as the data link layer oversees the delivery of the packet between two systems on the same network.
NETWORK LAYER
TRANSPORT LAYER
The transport layer is responsible for delivery of a message from one process to another.
It defines:1. Reliable delivery of data2. Ordering of delivery3. Port addressing4. Segmentation and reassembly5. Connection control6. Flow control and Error control7. Main protocols are TCP and UDP
TRANSPORT LAYER
TRANSPORT LAYER
SESSION LAYER
This OSI layer, as the name implies:1. Establishes2. Maintains3. Ends sessions between nodes4. Manage transmit data
Dialog controller i.e. whether connection is half duplex or full duplex.
PRESENTATION LAYER
Defines the format of data being sent The presentation layer is designed to handle the
syntax and semantics of the information exchanged between two systems
Main functions of this layer are 1. Compression2. Encryption and Decryption
Some Examples of services used are listed below: 1. HTML (Hyper Text Markup Language)2. GIF (Graphics Interchange Format )3. JPEG (Joint Photographic Experts Group)4. ASCII (American Standard Code for Information
Interchange)
APPLICATION LAYER The application layer is responsible for
providing services to the user. The application layer enables the user to
access the network.1. Mail services2. File transfer and access3. Remote log-in4. Accessing the world wide web5. Main protocols at this layer are HTTP, SMTP,
SNMP, FTP, TELNET
APPLICATION LAYER
THANK YOU…!
Kashif Latif