Chapter 3 - OSI Layers Flashcards
OSI
Open Systems Interconnection
Layer 1?
2 main points
Physical Layer
Defines the method of moving data (bits - 1s and 0s) between computers.
copper/fiber-optic cabling. network topology(the way the cabling is physically laid out), Signal(voltage, light and even radio waves). Hubs and Repeaters are also part of Layer 1.
Which is the last Layer that deals with hardware?
Layer 3 the Network layer is the last layer to deal with hardware. layer 4-7 deal strictly with software.
Layer 2?
What does the NIC do here?
more…
Data Link Layer
- Is where the NIC creates frames, adds recipients & senders MAC addresses, FCS.
- is the only layer with 2 sublayers. LLC layer and MAC layer.
Explain FCS and CRC
Frame Check Sequence uses binary math called Cycle Redundancy Check to verify that the data arrived intact.
What Layer has 2 sublayers?
And Explain what they do.
Data Link layer has the 2 sublayers LLC & MAC
Logical Link Control - identifies the Network Layer protocols and encapsulates them.
provides flow control
Media Access Control - Adds or Checks FCS and adds addresses to frames.
Layer 3?
Network Layer
Manages logical device (devices with IP address) addressing, tracks the location of these devices on the network and determines the best way to move data.
packets are created here with destination and source IP addresses.
Layer 4?
3 main points.
Transport Layer
Assemble or Disassemble data into chunks called TCP segments or UDP datagrams.
Transmission Control Protocol segments get sequence numbers to confirm completion . and is a connection-oriented communication.
User Datagram Protocol is a connectionless communication and gets No sequence numbers.
Layer 5?
Session Layer
Establishes, Manages and Terminates connections between computers and applications.
Checks if the connection is simplex, half duplex or full duplex.
Explain the difference between Simplex, Half Duplex and Full Duplex.
Simplex is unidirectional, meaning the sender can send data but not receive. like a keyboard or monitor.
Half Duplex is two directional, meaning the it can send and receive data, but NOT at the same time. like a walkie talkie
Full Duplex is also two directional, but Can send and receive data at the Same time. like a telephone
Layer 6?
Presentation Layer
Translates data from lower layers to a format usable by the application layer. and vice versa.
Encryption and decryption like SSL / TLS also happen here.
Layer 7?
Application Layer
Enables the application to access the network. It provides user interface
Allows network-aware applications to get online.
