PDU Data Communication

Question 1

What is PDU?

Answer 1

Protocol Data Unit, or transmission unit

Question 2

Ethernet operates on a ____ of data.

Answer 2

Frame

(It doesn’t care what’s inside)

Question 3

IP operates on a ____ of data.

Answer 3

Packet

Question 4

IP operates on a packet of data, what is inside?

Answer 4

TCP or UDP, IP doesn’t care which.

Question 5

What PDU is on the Physical Layer?

Answer 5

Bit

Question 6

What PDU is on the Data Link Layer?

Answer 6

Frame

Question 7

What PDU is on the Network Layer?

Answer 7

Packet

Question 8

What PDU is on the Transport Layer?

Answer 8

TCP Segment OR UDP Datagram

Question 9

What PDU is on the Session Layer?

Answer 9

Data

Question 10

What PDU is on the Presentation Layer?

Answer 10

Data

Question 11

What PDU is on the Application Layer?

Answer 11

Data

Question 12

At what layer does Application Data exist?

Answer 12

Layers 5, 6, and 7.

5 - Session Layer
6 - Presentation Layer
7 - Application Layer

Question 13

In encapsulation and decapsulation, what is added at layer 4 and what is layer 4?

Answer 13

(4) Transport Layer, a TCP header (or segment header) is added.

Question 14

In encapsulation and decapsulation, what is added at layer 3?

Answer 14

(3) Network Layer, an IP header or packet header is added.

Question 15

In encapsulation and decapsulation, what is added at layer 2?

Answer 15

(2) Data Link Layer, a frame header AND frame trailer are added.

Question 16

Encap/Decap Layers 5-7 Application Data Examples

Answer 16

HTTPS, IMAP, SSH

Question 17

Encap/Decap Layers 2-4 data types

Answer 17

Layer 2 Data Link Layer - MAC
Layer 3 Network Layer - IP
Layer 4 Transport Layer - TCP/UDP

Question 18

In the TCP header, what do the following flags mean?
- SYN
-PSH
-RST
-FIN

Answer 18

SYN Synchronize sequence numbers
PSH push data to application layer without buffering incoming data
RST reset the connection
FIN last packet from the sender

Question 19

What does MTU mean?

Answer 19

Maximum Transmission Unit, it’s the maximum IP packet size that can be transmitted without fragmenting.

Question 20

Why is fragmenting undesireable?

Answer 20

It slows down the flow of traffic.

Question 21

In setting MTU, what is an example of tunneled information and what effect does it have on MTU?

Answer 21

A VPN tunnels information, the tunnel may be smaller than local ethernet segment.

Question 22

What happens if you sent a packet larger than MTU with the DF bit set?

Answer 22

The router will drop the packet, and will likely tell you to fragment and you’ll get an ICMP message.