S3-OSI Model Flashcards
OSI Model
“Open Systems interconnect”
- A Reference model used to categorize and troubleshoot the functions of a network.
What are the 7 layers of the OSI Model?
1- Physical
2 - Data Link
3 - Network
4 - Transport
5 - Session
6 - Presentation
7 - Application
Transition Modulation
Switching between levels/states to represent 1s and 0s
What are the two Ethernet Wiring Standards?
TIA/EIA - 568A
TIA/EIA - 568B
How does a Layer 1 Device View a network?
From a Physical Topology Perspective
How does Asynchronous communication work?
Start and Stop Bits are used to indicate when transmissions occur from sender to receiver.
How does Synchronous communication work?
A common reference clock is used to coordinate transmissions between sender and receiver.
Define Asynchronous vs Synchronous communication
transmissions happening at different times. (Async.)
vs
transmission happening at the same time or in real time. (Sync)
Broadband
Divides bandwidth into separate channels
Eg. TV, Cable
Baseband
Uses all frequencies on a medium
What is Bandwidth
Network bandwidth is the maximum possible amount of data transfer between two points of a network in a specific time.
Measured in bits per second (bps)
What is Time-Division Multiplexing (TDM)?
Each session is allocated a time slot to share a medium between users.
Define Multiplexing
Utilizing a limited resource more efficiently. Allows simultaneous transmission on a single baseband connection.
What is Statistical Time-Division Multiplexing (StatTDM)?
Time slots are dynamically allocated on an as-needed basis.
What is Frequency division multiplexing (FDM)?
A medium is divided into channels , allowing each session to be transmitted over a different channel.
What are Some Layer 1 devices/media?
Media
- Fiber optic
- Ethernet/Rj-45
- Coaxial
- Blutooth
- Wi-Fi
- Near Field Communication (NFC)
Devices
- Hubs
- Repeaters
- Media Converters
What is the Purpose/function of the Physical Layer (L1)?
Resolves the data signals transmitted through physical mediums like cables and radio signals into BITS.
What is the Purpose/function of the Data link Layer (L2)?
Governs error checking, multiplexing, flow control and physical addressing of devices on a network through sub-layers like MAC & LLC. Additionally, responsible for packing BITS into FRAMES.
MAC Address
“Media Access Control Address”
A means for identifying a device physically.
How many bits are in a Mac address and what does each half represent?
MAC Address is a 48-bit physical addressing system.
-first 24-bits is the vendor/manufacturer code
- last 24-bits is the unique device code
What is a “Logical Link Control” (LLC)
A sublayer within the data link layer responsible for basic error checking, multiplexing and flow control.
What are the 3 different schemes communication can be synchronized across Layer 2?
- Isochronous
- Synchronous
- Asynchronous
Isochronous
Communication on a network is synchronized using a common reference clock and time slots are created for transmission. provides less overhead.
Synchronous
Network Devices utilize the same clocking method and control characters to indicate the beginning and ending frames of a transmission.
Asynchronous
Network Devices reference their own internal clocks and use start and stop bits for synchronization.
What is a CAM Table?
“Content Addressable Memory”
A database on a network switch that stores the MAC Addresses of devices connected to its ports. Allows for network traffic to be forwarded directly to its intended device.
What are some Layer 2 Devices?
- Network Interface (NIC) Cards
- Bridges
- Switches
What is the purpose/function of the Network Layer(L3)?
Handles the logical addressing and path determination for data packet transmission across networks.