PDU Data Communication Flashcards
What is PDU?
Protocol Data Unit, or transmission unit
Ethernet operates on a ____ of data.
Frame
(It doesn’t care what’s inside)
IP operates on a ____ of data.
Packet
IP operates on a packet of data, what is inside?
TCP or UDP, IP doesn’t care which.
What PDU is on the Physical Layer?
Bit
What PDU is on the Data Link Layer?
Frame
What PDU is on the Network Layer?
Packet
What PDU is on the Transport Layer?
TCP Segment OR UDP Datagram
What PDU is on the Session Layer?
Data
What PDU is on the Presentation Layer?
Data
What PDU is on the Application Layer?
Data
At what layer does Application Data exist?
Layers 5, 6, and 7.
5 - Session Layer
6 - Presentation Layer
7 - Application Layer
In encapsulation and decapsulation, what is added at layer 4 and what is layer 4?
(4) Transport Layer, a TCP header (or segment header) is added.
In encapsulation and decapsulation, what is added at layer 3?
(3) Network Layer, an IP header or packet header is added.
In encapsulation and decapsulation, what is added at layer 2?
(2) Data Link Layer, a frame header AND frame trailer are added.
Encap/Decap Layers 5-7 Application Data Examples
HTTPS, IMAP, SSH
Encap/Decap Layers 2-4 data types
Layer 2 Data Link Layer - MAC
Layer 3 Network Layer - IP
Layer 4 Transport Layer - TCP/UDP
In the TCP header, what do the following flags mean?
- SYN
-PSH
-RST
-FIN
SYN Synchronize sequence numbers
PSH push data to application layer without buffering incoming data
RST reset the connection
FIN last packet from the sender
What does MTU mean?
Maximum Transmission Unit, it’s the maximum IP packet size that can be transmitted without fragmenting.
Why is fragmenting undesireable?
It slows down the flow of traffic.
In setting MTU, what is an example of tunneled information and what effect does it have on MTU?
A VPN tunnels information, the tunnel may be smaller than local ethernet segment.
What happens if you sent a packet larger than MTU with the DF bit set?
The router will drop the packet, and will likely tell you to fragment and you’ll get an ICMP message.
