OSI Model

Question 1

What are the layers of the osi model?

Answer 1

Application, presentation, session, transport, network, data link, hardware

Question 2

What does the application layer do?

Answer 2

It is the interface between two applications that provide services to a user , such as a browser and web server using HTTP application layer protocol.

Question 3

What is SNMP?

Answer 3

Simple network management protocol - monitor and gather information about network traffic and can alert network administrators about adverse conditions that need attention

Question 4

What does the presentation layer do?

Answer 4

It is responsible for reformatting, compressing, and/or encrypting data in a way that the application on the receiving end can read

Question 5

What does the session layer do?

Answer 5

How data between applications is synced and recovered if messages do not arrive intact at the receiving application

Question 6

What does the transport layer do?

Answer 6

Transporting application layer payloads from one application to another,

Question 7

What are the two main transport layer protocols ?

Answer 7

TCP and UDP

Question 8

What does the network layer do?

Answer 8

Aka Internet layer, is responsible for moving messages from one node to another until they reach the destination host.

Question 9

What is the principal protocol used in the network layer?

Answer 9

Ip - adds its own network layer header to the segment o datagram, and the entire network layer message is now called a packet

Question 10

What do network layer headers do?

Answer 10

Identifies the sending and receiving hosts by their ip addresses.

Question 11

What does the data link layer do?

Answer 11

It is the interface with the physical hardware only on the local network. They are programmed into the firmware of a computer’s nic and other networking hardware.

Question 12

What is the name of the data link layer message?

Answer 12

Frame

Question 13

What does the physical layer do?

Answer 13

Sending bits via a wired or wireless transmission

Question 14

What are the steps involved from the sending host?

Answer 14

1. The browser creates an http message on source computer → passes to transport layer [ the browser involves all 3 layers]
2. TCP encapsulates the message by adding its own header and passes the segment→ to network layer
3. Ip and network layer in the os receive segment, adds a header, and passes the packet → data link layer
4. Data link layer on the nic firmware receives the packet, adds its header and trailer, and passes the frame → physical layer
5. Physical layer on the nic hardware puts bits on the network.

Question 15

What are the steps involved from sending host to the switch?

Answer 15

6. The network transmission is received by switch, which passes the frame up to data link layer { firmware on switch} looks at the destination MAC address, and decides where to send frame
7. The frame is sent to the correct port on the switch to the router.

Question 16

What are the steps involved from switch to router?

Answer 16

8. The water has two nic, one for each of the two networks to which it belongs. The physical layer of the first nic receives the frame and it passes to the data junk layer [nic firmwares] which removes the frame header and trailer and passes the packet up to Ip at network layer[firmware program or other software] on the router
9. The ip program looks at destination ip address. Determines the next node en route for the packet, and passes the packet
   Back down to the data link on the second NIC. Data link adds a new frame header and trailer appropriate for this second nic LAN, including MAC address of the next destination node.it passes the frame to its physical layer [nic hardware] which sends the bits on their way.

Question 17

What steps are involved from router to distortion host?

Answer 17

10. When frame reaches the destination host nic, the data link layer nic firmware, receives it. Removes the frame header and trailer, and passes the packet up to ip at the network layer, which removes its header and passes the segment up to TCP at the transport layer.
11. TCP removes its header and passes the payload up to http at the application layer. HTTP presents the message to the web server.