Key words Flashcards
(95 cards)
What is Layer 1 of the OSI model?
Physical layer - Signalling, Cabling, Connectors
What happens at Layer 1 (Physical layer) of the OSI model?
Packets are converted into electrical, radio, or optical pulses and transmitted as bits (the smallest possible units of information) over wires, radio waves or cables
What does a layer 1 (Physical) issue look like?
Issues with cabling, Punch downs, Electrical signals, Bad ports - Solutions can involve replacing cables, Swapping adapter cards
What is Layer 2 of the OSI model?
Data link Layer - The basic network ‘language’ - Foundation layer of connection - Uses MAC address on ethernet
What happens at Layer 2 (Data link) of the OSI model?
Handles communications between devices on the same network. If Layer 3 is like the address on a piece of mail, then layer 2 is like indicating the office number or apartment of that address. Ethernet is the protocol most used here.
What is DLC protocol and what does it do?
Data link control protocol - Provides functions such as flow control, error detection and error control
What is Layer 3 of the OSI model?
Network layer
What happens at Layer 3 of the OSI model?
Handles the routing and sending of data between different networks. The most important protocols at this layer are IP and ICMP. IP addresses (Logical Address) operates at this layer.
What is Layer 4 of the OSI model?
Transport Layer
What happens at Layer 4 of the OSI model?
Provides the means for transmitting data between the two connected parties, as well as controlling the quality of service. The main protocols used are TCP and UDP - Assembling and Disassembling data happens here
What is TCP?
What is the connection type?
Does it sequence data?
Does it allow for data retransmission?
Is delivery guaranteed?
Does it check for errors?
Does it support broadcasting?
Is it fast or slow?
Transmission Control Protocol:
Connection type - Requires an established connection before transmitting data
Data Sequence - Can sequence data (send in a specific order)
Data retransmission - Can retransmit data if packets fail to arrive
Delivery - Delivery is guranteed
Check for errors - Thorough error-checking guarantees data arrives in its intended state
Broadcasting - Not supported
Speed - Slow but complete data delivery
TCP is the only protocol that can retransmit lost data packets - When reliability is critical, TCP is the best option.
What is UDP?
What is the connection type?
Does it sequence data?
Does it allow for data retransmission?
Is delivery guaranteed?
Does it check for errors?
Does it support broadcasting?
Is it fast or slow?
User Datagram Protocol:
Connection type - No connection is needed to start and end a data transfer
Data Sequence - Cannot sequence or arrange data
Data retransmission - No data retransmitting. Loss data can’t be retrieved
Delivery - Delivery is not guaranteed
Check for errors - Minimal error-checking covers the basics but may not prevent all errors
Broadcasting - Supported
Speed - Fast, but at risk on incomplete data delivery
Name some use cases that TCP is better suited to?
Email or Texting
File transfers
Web browsing
Remote device or network administration
Name some use cases that UDP is better suited to?
Live streaming
Online gaming
Video chatting/ Conferencing
VOIP
Domain Name Systems
How does TCP work?
Uses the 3 way hand shake
Client device initiating contact will send a sequence number (SYN) to the server. Tells the server the number that the data packet transfer should begin with.
The server acknowledges the client SYN and sends its own SYN number. This step is referred to as SYN-ACK (SYN acknowledgement)
The client then acknowledges(ACK) the server’s SYN-ACK, which forms a direct connection and begins the data transfer.
The connection between the sender and receiver is maintained until the transfer is successful. Every time a data packet is sent, it requires an acknowledgment from the receiver. So, if no acknowledgment is received, the data is resent.
If an error is acknowledged, the faulty packet is discarded and the sender delivers a new one. Heavy traffic or other issues may also prevent data from being sent. In that case, the transmission is delayed (without breaking the connection).Thanks to these controls, successful data delivery is guaranteed with TCP.
How does UDP work?
UDP works by sending data immediately to the receiver who made a transmission request until the transmission is completed or terminated. Sometimes called a “fire and forget” protocol, UDP fires data at a recipient without confirming delivery or checking if packets arrived as intended.
Does not perform a handshake. Speeds up transfer data by sending packets without making an agreement with a receiver.
What is layer 5 of the OSI model?
Session Layer
What happens at layer 5 of the OSI model?
Controls connections between computers (this can also be handled at layer 4 by the TCP protocol) - Part of the host that makes connection to the remote host i.e. a web browser to a web server or an email client to to an email server.
What is layer 6 of the OSI model?
Presentation Layer
What is EMI?
Electromagnetic Interference
What is CSMA/CD?
Carrier Sense Multiple Access/Collision Detection Is a technology used for devices to listen and see who is communicating. Collision detection
What is ARP?
Address resolution protocol - ARP is a method used to get the MAC address of hosts
What is full duplex?
Is a communication mode where two devices can talk at the same time
What is CSMA/CA?
Is for collision avoidance rather than detection
