OSI Model

Question 1

The 7 Layers of the OSI Model

Answer 1

Application (Data)
Presentation (Data)
Session (Data)
Transport (Segments)
Network (Packets)
Data Link (Frames)
Physical (Bits)

Question 2

Layer of the OSI model where transmission of bits across the network occurs and includes physical and electrical network characteristics.

This layer’s devices are essentially repeaters, passing along whatever is received

Answer 2

Physical Layer – Layer 1

Question 3

Examples of Physical – Layer 1 devices

Answer 3

Wired:
- Fiber optic cable
- Ethernet cable
- Coaxial cable

Wireless:
- Bluetooth
- Wi-Fi
- Near Field Communication (NFC)

Infrastructure:
- Hubs
- Access points
- Media converters

Question 4

Layer of the OSI model that packages data into frames and transmits those frames on the the network

This layer’s devices view networks logically through mac addresses

Answer 4

Data Link Layer – Layer 2

Question 5

Examples of Layer 2 – Data Link Layer devices

Answer 5

• Network Interface Cards (NICs)
• Bridges
• Switches

Question 6

Examples of Layer 3 – Network Layer devices/protocols

Answer 6

• Routers & Multi-Layer Switches
• IPv4 & IPv6
• ICMP (Internet Control Message Protocol)

Question 7

1) A connection-orientated protocol that i a reliable way to transport segments across the network (sends and verifies received) (hint: Segments)

2) A connectionless protocol that is an unreliable way to transport segments across the network (no verification of received) (hint: Datagram)

Answer 7

1) TCP (Transmission Control Protocol)

2) UDP (User Datagram Protocol)

Question 8

What is UDP good for?

Answer 8

Audio and visual streaming

(because a lot of data it sent and there’s a lot less overhead (acknowledgment) – no three-way-handshake

Question 9

Notes:
Layer 4 – Main Differences between TCP vs. UDP

Answer 9

TCP
- Reliable
- Connection-orientated
- Segment retransmission and flow control through windowing (windowing allows the clients to adjust the amount of data in each segment)
- Segment sequencing (in-order)
- Acknowledges segments

UDP
- Unreliable
- Connectionless
- No windowing or retransmission
- No sequencing
- No acknowledgement

Question 10

Examples of Layer 4 devices/protocols

Answer 10

• TCP and UDP protocols
• Load balancers and firewalls

Question 11

Layer that keeps conversation separate to prevent intermingling/cross-contamination of data

Answer 11

Session Layer – Layer 5

Question 12

Three aspects of a Session in Layer 5

Answer 12

1) Set Up session
- Checking of user credentials and assigning numbers to sessions to help identify them

2) Maintain session
- Where data transfers back and forth across the network

3) Tear Down session
- Ending of a session after the transfer is done or when the other party disconnects

Question 13

Examples of Session – Layer 5 Protocols

Answer 13

• H.323
  (Used to set up, maintain, and tear down voice and video connections
• RTP (Real-time Transport Protocol)
  (Streaming audio/video (phone call or FaceTime session)
• NetBIOS
  (Used to share files over a network)

Question 14

Layer that formats data to be exchanged and secures that data with proper encryption (Hint: Data Formatting and Encryption)

Answer 14

Layer 6 – Presentation Layer

Question 15

Examples of Layer 6 – Presentation Layer

Answer 15

• Scripting languages (like HTML or JavaScript)
• Standard text (like ASCII or Unicode)
• Pictures and Movie files (like GIFs or PNGs and MOV files)
• Encryption algorithms (like TLS or SSL)

Question 16

Examples of Layer 7 – Application Layer

Answer 16

• Email applications (like SMTP, POP3, IMAP)
• Web browsing (like HTTP or HTTPS)
• DNS
• FTP
• Remote access (like RDP, telnet, ssh)