Chapter 1-3

Question 1

OSI model intent

Answer 1

• To provide a framework for networking that ensures compatibility in the network hardware and software to accelerate the development of new networking technologies

Question 2

How the OSI model works

Answer 2

• Each layer performs data encapsulation by putting its own message format or header onto the data as it is being passed down from layer 7 to 1
• Then when the data reaches an end device, the inverse process (decapsulation) occurs.
• Each layer reads its layer message format or header and takes it off before passing the data to the upper layers

Question 3

OSI model layers from top down

Answer 3

7. Application
8. Presentation
9. Session
10. Transport
11. Network
12. Data link
13. Physical

Question 4

The physical layer

Answer 4

• Layer 1.
• This layer provides electrical and mechanical connection to the network
• Examples NICs, fiber, wireless, twisted-pair cable

Question 5

The data link layer

Answer 5

• Layer 2
• This layer handles error recovery, flow control (synchronization) and sequencing (which terminals are sending and which are receiving)
• Considered the MAC layer (media access control layer)
• Examples: MAC addresses

Question 6

The network layer

Answer 6

• Layer 3
• This layer accepts outgoing messages and combines messages or segments into packets, adding a header that includes routing information
• Acts as a network controller
• Examples: IP, ICMP

Question 7

The transport layer

Answer 7

• Layer 4
• This layer is responsible for end-to-end delivery between devices
• Concerned with message integrity between source and destination
• Examples: TCP (transmission control protocol) and UDP (user datagram protocol)

Question 8

The session layer

Answer 8

• Layer 5
• This layer provides the functions necessary to establish, manage and terminate connections when needed to satisfy user requests.
• Examples: NFS (network file system) and SQL (structured query language)

Question 9

The presentation layer

Answer 9

• Layer 6
• This layer accepts and structures messages for an application
• Translates the message from one code to another if needed
• Responsible for data encryption and compression
• Examples: ASCII (American standard code for information interchange) and JPEG (joint photographic experts group)

Question 10

The application layer

Answer 10

• Layer 7
• The layer interacts with application programs that incorporate a communication component such as an internet browser and email.
• Responsible for logging in the message, interpreting the request and determining what information is needed to support the request.
• Examples: HTTP (Hypertext transfer protocol) for web browsing, FTP (file transfer protocol), SMTP (simple mail transfer protocol)