OSI Model Flashcards
How is data referred to at each layer?
mnemonic device: Don’t Some People Forget Birthdays
Layer 1 Physical -Bits
Layer 2 Data Link- Frames
Layer 3 Network- packets
Layer 4 Transport- Segments
layer 5,6,7 Session, Presentation, Application- Data
What is Layer one of OSI model? What are some examples of layer one devices?
Physical Layer:
Ethernet, Fiber Cables,
Radio frequencies such as WiFi or bluetooth
Also: Hubs, Wireless access points, media converters
What is multiplexing and what does it do?
- Multiplexing is taking a limited amount of resource and using it more efficiently
- Multiplexing allows multiple people to use a baseband connection at the same time
What are the two types of bandwidth? How are they different?
Bandwidth-2 Types : Broadband and Baseband
Broadband divides into separate channels
Baseband uses all frequencies of cable all the time
What is Layer 2 of OSI model? What are some examples of layer 2 devices?
Data Link Layer
Examples of layer 2 devices: NIC, Bridges, Switches, MAC Addresses
What are the 3 types of ways that communication is synchronized
- Isochronous mode
- Synchronous mode
- Asynchronous mode
Describe Isochronous mode of communication synchronization.
Isochronous mode-network devices use a common reference clock source and create time slots for transmission with less overhead than synchronous or asynchronous methods
Describe Synchronous mode of communication synchronization.
Synchronous mode- network devices are on clocking method to indicate beginning and end of frames and can use control characters or separate timing channels.
takes up a lot of networking bandwidth
Describe Asynchronous mode of communication synchronization.
Asynchronous mode- network devices reference their own internal clocks and use start/stop bits. No real control over how devices communicate
What does Logical Link Control (LLC) do?
Logical link Control (LLC)-Provides connection services and allows acknowledgement or receipt of messages. It is also the most basic form of flow control. uses checksum to verify data is not corrupted or missing data
What form are MAC addresses written in?
What do the first 6 letters in a MAC address represent?
What do the last 6 letters represent?
MAC addresses are written hexadecimally where each number or letter = 4 bits
The first 24 bits or 6 letters are the VENDOR code
the last 24 bits or 6 letters is for exact machine
What does the Data Link layer do?
packages data into frames on the network, performing error detection/correction, uniquely identifying network devices with an address (MAC) and providing flow control
What is layer 3 of the OSI model? What are some examples of Layer 3?
Network Layer:
Routers, multilayer switches, IPv4 and IPv6 Protocol, ICMP
What is ICMP and what is it’s function?
Internet Control Message Protocol (ICMP)- Used to send error messages and operational information about an IP destination
What are some examples of routing protocols?
RIP, OSPF, EIGRP,etc..
What are the 2 types of route discovery and selection?
Manually configured as a static route
or
Dynamically through a routing protocol
What is Message Switching?
data is divided into messages similar to packet switching, except these messages may be stored then forwarded
messages are stored and forwarded similar to email
What is Circuit Switching?
Circuit switching is dedicated communication link is established between two devices, uses same path each time
example would be phone call where all data back and forth is traveling through the same path
What is Packet Switching?
packet switching =routing, this is normal how we use internet and is referenced to the mailbox and letters method of delivery
What are the three ways that data can be forwarded or routed?
Packet switching(most commonly used), Circuit switching or Message switching
How many bits in one Byte?
How many Bytes in an IP address?
8 Bits in a Byte
4 Bytes in an IP address
What is layer 3 switching referred to as? What does this get confused with?
Layer 3 switching is ROUTING
Gets confused with physical switches that operate at layer 2
What is Layer 3 on OSI model? What does it do?
Layer 3 Network - Forwards traffic (routing) with logical address (IPv4 or IPv6)
What is Layer 4 of OSI model? What are some examples of layer 4 devices/functions?
Transport Layer
TCP, UDP, WAN accelerators, Load balancers, Firewalls
