S3-OSI Model Flashcards

1
Q

OSI Model

A

“Open Systems interconnect”

  • A Reference model used to categorize and troubleshoot the functions of a network.
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2
Q

What are the 7 layers of the OSI Model?

A

1- Physical
2 - Data Link
3 - Network
4 - Transport
5 - Session
6 - Presentation
7 - Application

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3
Q

Transition Modulation

A

Switching between levels/states to represent 1s and 0s

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4
Q

What are the two Ethernet Wiring Standards?

A

TIA/EIA - 568A

TIA/EIA - 568B

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5
Q

How does a Layer 1 Device View a network?

A

From a Physical Topology Perspective

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6
Q

How does Asynchronous communication work?

A

Start and Stop Bits are used to indicate when transmissions occur from sender to receiver.

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7
Q

How does Synchronous communication work?

A

A common reference clock is used to coordinate transmissions between sender and receiver.

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8
Q

Define Asynchronous vs Synchronous communication

A

transmissions happening at different times. (Async.)
vs
transmission happening at the same time or in real time. (Sync)

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9
Q

Broadband

A

Divides bandwidth into separate channels
Eg. TV, Cable

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10
Q

Baseband

A

Uses all frequencies on a medium

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11
Q

What is Bandwidth

A

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)

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12
Q

What is Time-Division Multiplexing (TDM)?

A

Each session is allocated a time slot to share a medium between users.

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13
Q

Define Multiplexing

A

Utilizing a limited resource more efficiently. Allows simultaneous transmission on a single baseband connection.

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14
Q

What is Statistical Time-Division Multiplexing (StatTDM)?

A

Time slots are dynamically allocated on an as-needed basis.

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15
Q

What is Frequency division multiplexing (FDM)?

A

A medium is divided into channels , allowing each session to be transmitted over a different channel.

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16
Q

What are Some Layer 1 devices/media?

A

Media
- Fiber optic
- Ethernet/Rj-45
- Coaxial
- Blutooth
- Wi-Fi
- Near Field Communication (NFC)

Devices
- Hubs
- Repeaters
- Media Converters

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17
Q

What is the Purpose/function of the Physical Layer (L1)?

A

Resolves the data signals transmitted through physical mediums like cables and radio signals into BITS.

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18
Q

What is the Purpose/function of the Data link Layer (L2)?

A

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.

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19
Q

MAC Address

A

“Media Access Control Address”
A means for identifying a device physically.

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20
Q

How many bits are in a Mac address and what does each half represent?

A

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
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21
Q

What is a “Logical Link Control” (LLC)

A

A sublayer within the data link layer responsible for basic error checking, multiplexing and flow control.

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22
Q

What are the 3 different schemes communication can be synchronized across Layer 2?

A
  • Isochronous
  • Synchronous
  • Asynchronous
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23
Q

Isochronous

A

Communication on a network is synchronized using a common reference clock and time slots are created for transmission. provides less overhead.

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24
Q

Synchronous

A

Network Devices utilize the same clocking method and control characters to indicate the beginning and ending frames of a transmission.

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25
Q

Asynchronous

A

Network Devices reference their own internal clocks and use start and stop bits for synchronization.

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26
Q

What is a CAM Table?

A

“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.

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27
Q

What are some Layer 2 Devices?

A
  • Network Interface (NIC) Cards
  • Bridges
  • Switches
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28
Q

What is the purpose/function of the Network Layer(L3)?

A

Handles the logical addressing and path determination for data packet transmission across networks.

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29
Q

What are three methods of forwarding data across a Network?

A
  • Packet Switching (Routing)
  • Circuit Switching
  • Message Switching
30
Q

What is Packet Switching?

A

Data is divided into packets and then forwarded
-multi-path

31
Q

what is Circuit Switching?

A

Dedicated communication link is established between 2 devices.
-single path

32
Q

Message Switching

A

Data is divided into messages which may be stored and forwarded.

33
Q

What are Routing protocols?

A

Protocols that help decide how data will flow across a network and how routers are going to communicate that information.

34
Q

What do layer 3 Connection services do?

A

Augment layer 2 connection services to improve reliability.
- flow Control
- Packet reordering

35
Q

What is ICMP?

A

“internet control message protocol”
- Sends error messages and operational info to an IP about transmission issues.

36
Q

What does Ping do?

A

ICMP utility that sends out a packet to a destination and reports how long it took.

37
Q

What does Traceroute do?

A

ICMP utility that Traces the route of a packet through the network.

38
Q

What are some layer 3 devices?

A
  • Routers
  • Multi-Layer switches
39
Q

What are Protocols found at Layer 3?

A
  • ICMP
  • IPv4
  • IPv6
40
Q

What is the Function/purpose of the Transport layer (L4)?

A

Ensures that data reaches its destination accurately and completely.

41
Q

What are the 2 Layer 4 Protocols?

A
  • Transmission Control Protocol (TCP)
  • User Datagram Protocol (UDP)
42
Q

What is TCP?

A

Provides reliable, connection-oriented communication with features like flow control and error detection, and 3-way Handshake.
- Segments

43
Q

What is UDP?

A

Offers unreliable, connectionless communication, prioritizing speed over guaranteed delivery.
- Datagrams

44
Q

Three - Way- Handshake

A

Back and forth communication between 2 devices that ensure a transmission was successfully sent and received. Used by TCP.

45
Q

Define Windowing

A

Optimizes the throughput and bandwidth of a transmission by adjusting the amount of data in each segment during transmission. Functions by opening or closing the window dynamically according to incoming data flow.

46
Q

What is Buffering?

A

Devices allocating memory to store segments if bandwidth is not readily available.

47
Q

What are some Layer 4 devices?

A
  • WAN accelerators
  • Load Balancers
  • Firewalls
48
Q

What is the purpose/function of the Session Layer (L5)?

A

responsible for establishing, managing, and terminating communication sessions between devices

49
Q

What are some Layer 5 devices/protocols?

A
  • H.323
  • NetBIOs
50
Q

H.323

A

Used to setup, maintain and tear down voice and video connection.

51
Q

What is RTP?

A

“Real-time transport protocol”
- streaming audio/video

52
Q

what is NetBIOS?

A

A standard used by computers to share files over a network.

53
Q

What is the purpose/function of the Presentation Layer (L6)?

A

Formats and translates the data to be exchanged and secures it with proper encryption.

54
Q

Data Formatting

A

Ensures data is presented in a standardized format that the receiving application can understand.

55
Q

whats is ASCII?

A

“American Standard Code for Information Interchange”

It’s a character encoding standard that assigns a unique number to each letter, digit, and symbol.

56
Q

What is Encryption?

A

Method of securing data by scrambling it using mathematical algorithms that can only be decrypted with the proper key.

57
Q

what is TLS?

A

“Transport Layer Security”
A commonly used cryptographic protocol that protects data from being intercepted by hackers while it travels online.

58
Q

What are some Layer 6 components?

A

Scripting Languages
- Html
- Xml
- Java Script

Standard Text
- ASCII
- Unicode
- ECDBIC

Picture & Video Formats
- Jpeg
- PNG
- GIF
- MPEG
- MP4

Encryption Algorithms
- TLS
- SSL

59
Q

What is the purpose/function of the Application Layer (L7)?

A

Handles the communication between applications on different devices across a network, making network services accessible to users.

60
Q

Application Services

A

Unites communicating components from more than one network application

61
Q

Service Advertisement

A

Applications can announce the services they offer to other devices on the network.

62
Q

What are some Layer 7 Services?

A

Email Protocols
- POP3
- IMAP
- SMTP
Web Browsing
- Https
- Http
File Transfer Protocols
- FTP
- FTPS
- SFTP
Remote Access
- Telnet
- SSH
- SNMP

Domain Name Service (DNS)

63
Q

What is a PDU?

A

“Protocol Data Unit”
- A single unit of data transmitted in a computer network.

64
Q

What are the six TCP header flags and their meaning?

A

SYN - (Synchronization) Synchronize a connection during a 3-way handshake

ACK - (Acknowledgement) Acknowledges successful receipt of packets

FIN - (Finish) Terminates the virtual connection created by the 3-way handshake

RST - (Reset) used when a client/server receives an unexpected packet

PSH - (Push) ensures that data is given priority

URG - (Urgent) identifies incoming data as urgent

65
Q

what is EtherType?

A

The protocol encapsulated in the payload of a frame.
Eg. IPv4, Ipv6 etc.

66
Q

What is the minimum size payload that can be sent over ethernet with and w/o VLANs?

A

42 bytes w/ VLANs

46 bytes w/o VLANs

67
Q

What is the maximum size (MTU) payload that can be sent over ethernet?

A

1500 MTU

68
Q

What is a Jumbo Frame?

A

A frame configured to be larger than 1500 bytes.

69
Q

When is Data encapsulated?

A

when moving from Layer 7 - Layer 1

70
Q

When is Data decapsulated?

A

when moving from layer 1 - Layer 7