Osi Reference Model
Network Models
2.1
THE OSI MODEL
•Established in 1947, the International Standards 1947, Organization (ISO) is a multinational body dedicated to ISO) worldwide agreement on international standards. standards. •An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. OSI) model. 1970s • the open system is the set of protocols that allows any two different systems to communicate without regarding of their underlying architecutre(h/w and s/w). architecutre(h/w s/w).
2.2
Note
ISO is the organization. OSI is the model.
2.3
Figure 2.2 Seven layers of the OSI model
2.4
Figure : The interaction between layers in the OSI model
2.5
Figure 2.4 An exchange of data using the OSI model
2.6
LAYERS IN THE OSI MODEL
In this section we briefly describe the functions of each layer in the OSI model. model.
Topics discussed in this section:
Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer
2.7
Physical layer The physical layer is responsible for movements of individual bits from one hop (node) to the next.
2.8
Physical Layer
The major functionalities of physical layer are:
• Physical characteristics of interfaces and medium • Representation of bits • Data rate • Synchronization of bits • Line configuration • Physical Topology • Transmission mode
2.9
Data link layer The data link layer is responsible for moving/sending frames from one hop (node) to the next.
2.10
Data Link Layer
The major functionalities of data link layer are:
• • • • • Framming Physical addressing Flow control Error control Access control
2.11
Figure : example of Hop-to-hop delivery
2.12
Example 1
In Following Figure a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the
2.1
THE OSI MODEL
•Established in 1947, the International Standards 1947, Organization (ISO) is a multinational body dedicated to ISO) worldwide agreement on international standards. standards. •An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. OSI) model. 1970s • the open system is the set of protocols that allows any two different systems to communicate without regarding of their underlying architecutre(h/w and s/w). architecutre(h/w s/w).
2.2
Note
ISO is the organization. OSI is the model.
2.3
Figure 2.2 Seven layers of the OSI model
2.4
Figure : The interaction between layers in the OSI model
2.5
Figure 2.4 An exchange of data using the OSI model
2.6
LAYERS IN THE OSI MODEL
In this section we briefly describe the functions of each layer in the OSI model. model.
Topics discussed in this section:
Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer
2.7
Physical layer The physical layer is responsible for movements of individual bits from one hop (node) to the next.
2.8
Physical Layer
The major functionalities of physical layer are:
• Physical characteristics of interfaces and medium • Representation of bits • Data rate • Synchronization of bits • Line configuration • Physical Topology • Transmission mode
2.9
Data link layer The data link layer is responsible for moving/sending frames from one hop (node) to the next.
2.10
Data Link Layer
The major functionalities of data link layer are:
• • • • • Framming Physical addressing Flow control Error control Access control
2.11
Figure : example of Hop-to-hop delivery
2.12
Example 1
In Following Figure a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the