The OSI model

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what is the OSI model and why is it important in understanding network
*OSI model is a concept way that is broken down into segments that discuss the complex process of sending data over the network.

*understanding the model is important because its a widely used model that talks about network communication.
what are the advantages of using a theoretical model to describe networking ?
* it give a common language and reference point for network professionals.

* It divides networking task into logical layers that are easy to understand.

* has different features at different levels

* Easier to troubleshooting

*promotes standards of interoperability (healthcare) networks and devices
what is the name Of layer 3 in the OSI model ? layer 5?
*Layer 3 is called Network

* Layer 5 is called Session
which Osl model layers typically correspond to the network architecture?
The physical Layer
How does the session ID differ from the port number ?
*Session ID keep data streams separate.

* Port numbers identifies the process of where a network message should be forwarded on a server.
At which OSI model layer would YOU find a frame?
Data link layer (2)
what is the difference between connectionless and Connection-oriented services?
Difference between Connection oriented service and Connectionless service

1.In connection oriented service authentication is needed while connectionless service does not need any authentication.

2.Connection oriented protocol makes a connection and checks whether message is received or not and sends again if an error occurs connectionless service protocol does not guarantees a delivery.

3.Connection oriented service is more reliable than connectionless service.

4.Connection oriented service interface is stream based and connectionless is message based.
Limitation of OSI Model
* The layer models are a concept and don't actually perform functions

*some function do not spread across to other layers

* industry rarely have correspondence with the layers
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data link
1. Physical
1. Physical
2. Data Link
3. Network
4.Transport
5.Session
6. Presentation
7.Application
Application (layer 7)
combines network functionality into the host(device) OS and enable network services.
Presentation(Layer 6)
formats data into compatible form for receiving by the application layer or the destination center

* This layer ensures formatting and translation of data between systems

* converting character sets to the correct format

* Enclose data into a message envelope by encryption and compression.

* Restoration of data by decryption and decompression.
Session(Layer 5)
the session layer manages the session in the way that data is transferred

*manage multiple sessions (each client connect is called a session) A server can manage thousands of sessions.

* it manages by setting up, maintenance , and tearing down of communication sessions.
Transport(Layer 4)
The transport layer provides a transition b/w the upper and lower layers of the OSI model

(function include the following below)
* End-to-end flow control
*port and socket numbers
*Segmentation, sequencing, and combinations
*connecting services(connection-oriented) or (connectionless) delivery data
Data at the transport layer is referred to as
Segments
Network(Layer3)
this layer describes data is traces or routed across the network and on to the destination

(functions are)
* Identifying host and networks by using logical address

*Maintaining a list of known networks and neighboring routers.

* determines where the next access point to where the data should be sent.
Data at the network layer is referred to as
packets
Routers
use a routing protocol pays attention to the hops in paths ,link speed, and link reliability
Data Link (layer 2)
this link defines the rules and procedures for host as they access the physical layer.

(The Define procedures)

* How host on the network are identified (physical or MAC address)

* How and when devices transmit on the network medium

*How to verify that the data received from the physical layer are error free(Parity CRC)

*How devices control the rate of data transmission between hosts (flow Control)
Data in the data link layer is referred to as
Frames
Physical (layer 1)
This layer set standards for sending and receiving electrical signals between devices.

*protocols are identified at this layer:

* How digital data (bits) are converted to electrical pulses, radio waves, or pulses of light.

*Specifications for cables and connectors
Data at the physical layer is referred to as
bits
TCP/IP model
includes the general concepts and structure of the OSI model.
TCP/IP model layers
1. Application
2.Host-to-Host
3.Internet
4. Network Access
TCP/IP (Application)
this layer corresponds to the session , presentation, and Application layer of the OSI model
TCP/IP (Host-to-Host)
this layer is comparable to the transport layer

*it is responsible for error checking and reliable packet delivery .

* data stream is broken in to segments that must be assign sequence numbers so they can reform correctly on the remote side after they are transported.

* TCP(transport control layer ) and UDP(User Datagram protocol) are included in this layer
TCP/IP(Internet)
This layer is similar to the network layer

*Its responsible for moving packets

*Address host and make routing decision to identify how packets move across the network.

* This layer protocols include ARP(address resolution protocol), ICMP (internet control messages protocol) and , IGMP (Internet group management protocol)
TCP/IP(Network Access)
This layer corresponds to the physical and data link layer

* Its responsible for explaining the physical layout of the network and how messages are formatted on the transmission medium.
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