OSI Flashcards
What are the seven layers of OSI model?
Application, Presentation, Session, Transport, Network, Data Link, Physical
What runs in Application Layer?
Network applications for file transfer, web surfing, emails and virtual terminals
Protocol for file transfer
FTP
Protocol for web surfing
HTTP/S
Protocol for emails
SMTP
Protocol for virtual terminals
Telnet
What is the Presentation Layer responsible for?
Translation, Data Compression, Encryption
What is SSL?
Secure Socket Layer
What is Session Layer responsible for?
Authentication, Authorization, Session Management
What type of data runs in Session Layer?
Data Packets
What is Transport Layer responsible for?
Segmentation, Flow Control, Error Control, Connection and Connectionless Transactions
What is the difference between UDP and TCP?
UDP does not give feedback, hence is faster than TCP. However, it is less reliable.
How can TCP recover lost/corrupted data?
By using the checksum methods to find corrupted data and by checking the sequence number to find lost segments
What layers run on the web browser?
Application, Presentation and Session
What type of data runs in Transport Layer?
Segments
What information does a segment has?
Port number and sequence number
What for are port numbers used in a segment?
It helps to direct each segment to the correct application
What for are segment numbers used in a segment?
It helps to disassemble segments in the correct order to form the correct message at the receiver
What happens in flow control in transport layer?
The amount of data being transmitted is controlled (bandwidth)
What happens in error control in transport layer?
Loss and corrupted data are retransmitted by using automatic repeated requests schemes
What is checksum?
A group of bits added to each segment by the transport layer to find out the received corrupted segment
What protocols run on transport layer?
Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)
Where is UDP used?
Where data loss does not matter. VoIP apps, Video, Music, Games, DNS, TFTP
Where is TCP used?
Where full data is necessary. WWW, Emails, FTP
What does network layer do?
Transmits data segments from one computer to another in different networks
What is Network Layer responsible for?
Logical Addressing (IPv4 & IPv6 + Mask), Routing, Path Determination
How are data units called in Network Layer?
Packets
How is a IP Packet formed?
Network layer assigns the IP number of source and destination to a segment
What is routing?
Method of moving a data packet from source to destination and it is based on the logical IP format of IPv4 or IPv6
How does the masking work in Network Layer?
It masks the IP where the numbers masked by 255 represent the network address and the number masked by 0 represents the computer ID inside a local network
What is path determination
Is choosing the best possible path for data delivery from source to destination
What protocols can determine the best path for data delivery?
OSPF: open shortest path first, BGP: border gateway protocol, IS-IS: intermediate system to intermediate system
What are the types of addressing?
Logical addressing (network layer - assigning IPs to segment to form data packets) & Physical addressing (data link layer - MAC addresses are assigned to each segment to form a frame)
Where and how is a data frame formed?
At data link layer. MAC1 + MAC2 + IP1 + IP2 + Segment + Tail
Where and how is a data packet formed?
At network layer. IP1 + IP2 + Segment
What is a MAC address?
A 12-digit alphanumeric number embedded in the network interface card (NIC) of a computer
How are data units called in data link layer?
Frame
Where is data link layer located and what does it do?
The data link layer is a software embedded int the network card of a computer and provide means to transfer data from one computer to another via local media
What are the functions of data link layer?
Access the media (framing) and control how data is placed and received from the media (media access control and error detection)
What is CSMA?
Carrier Sense Multiple Access. It controls when the media will be accessed on data link layer to avoid conflicts when multiple computers on the same network send/receive data at the same time
What is the tail of each contained of and responsible for?
It contains bit to detect errors in the received frame
How does the physical layer work?
it transforms the bits (frames) received from data link layer into signals to transmit over local media (electrical signals - coper cable, light signal - optical fiber, radio signal - wi-fi)
