OSI MODELS Flashcards
(18 cards)
What does OSI stand for in networking?
OSI stands for Open Systems Interconnection. It is a conceptual model developed by the ISO to standardize the functions of a telecommunication or computing system into seven abstract layers.
Why is the OSI model important in networking?
The OSI model helps different network devices and software communicate by providing a universal set of standards for networking protocols and interactions across seven layers. It also aids troubleshooting and understanding data flow.
List all seven layers of the OSI model from top to bottom.
- Application
- Presentation
- Session
- Transport
- Network
- Data Link
- Physical
Which layer of the OSI model handles encryption and compression?
The Presentation Layer (Layer 6) handles encryption, decryption, data compression, and translation between different data formats.
What is the main role of the Application Layer in the OSI model?
The Application Layer (Layer 7) provides services directly to user applications such as web browsing, email, and file transfer. It enables user interaction with the network.
What does the Session Layer (Layer 5) do?
The Session Layer establishes, manages, and terminates sessions between applications. It handles dialog control and synchronization between communicating systems.
What are the responsibilities of the Transport Layer (Layer 4)?
The Transport Layer provides reliable or unreliable data delivery, error correction, and flow control. It manages segmentation and reassembly of data and uses TCP or UDP protocols.
Which layer is responsible for routing data across networks?
The Network Layer (Layer 3) is responsible for logical addressing and routing data packets across different networks. It uses IP addresses and protocols like IP and ICMP.
What is the role of the Data Link Layer (Layer 2)?
The Data Link Layer ensures reliable transmission of data across a physical link. It handles error detection, MAC addressing, and framing. It includes sublayers: MAC and LLC.
Which layer of the OSI model transmits raw bits over a physical medium?
The Physical Layer (Layer 1) is responsible for the actual transmission of raw bits over a network medium, such as electrical signals over cables or radio waves in wireless networks.
What is encapsulation in the context of the OSI model?
Encapsulation is the process of adding headers (and sometimes trailers) to data as it moves down through the OSI layers before transmission. Each layer adds relevant control information.
What is the difference between TCP and UDP in relation to the OSI model?
TCP and UDP are both Transport Layer protocols. TCP provides reliable, connection-oriented communication, while UDP offers fast, connectionless transmission without guaranteed delivery.
How do the OSI and TCP/IP models differ?
The OSI model has seven layers, while the TCP/IP model has four layers: Application, Transport, Internet, and Network Access. OSI is theoretical; TCP/IP is used in real-world implementations.
Which OSI layer is responsible for segmenting large messages?
The Transport Layer (Layer 4) segments large messages into smaller units called segments for transmission, and reassembles them at the destination.
At which OSI layer do switches operate?
Switches operate at the Data Link Layer (Layer 2), where they forward frames based on MAC addresses.
At which OSI layer do routers operate?
Routers operate at the Network Layer (Layer 3), where they forward packets based on IP addresses.
What is a protocol data unit (PDU) and how does it relate to OSI layers?
A PDU is the form data takes at each OSI layer. For example, Layer 4 uses segments, Layer 3 uses packets, Layer 2 uses frames, and Layer 1 uses bits.
What is flow control and which OSI layer handles it?
Flow control is the process of managing the rate of data transmission to prevent overwhelming the receiver. It is handled by the Transport Layer (Layer 4).
