OSI Model 2

Question 1

Application

Answer 1

Application
Network process to application
Closest to end user Protocols: 
-smtp, http
https, DNS,
etc

Question 2

Presentation

Answer 2

Presentation
Encryption & compression
Converts to machine-readable language (binary, ASCII,
jpeg, png, etc

Question 3

Session

Answer 3

Session
Inter-host communication
Begins, maintains, & ends data transfer

Question 4

Transport

Answer 4

Transport
Reliability & flow control
Addressing: Port numbers
PDU: Segments
Protocols: 
TCP (connection-oriented
UDP (connectionless)/best effort/no 
 acknowledgments

Question 5

Network

Answer 5

Network
Path determination & packet switching
Addressing: IP (logical) 
Devices: Routers & Layer 3 switches 
Function of Router: connect networks
Protocols: IP, ICMP (ping & tracert), ARP
PDU: Packets
Best Path: Shortest or fastest?
Packet Switching:
• Data enters the router on one 
interface of a router (ingress) and 
leaves out of another interface 
(egress).

Question 6

Data Link

Answer 6

Data Link
Converts 0s & 1s to electricity, light, waves, etc.
Addressing: mac (physical, adapter, BIA,
hardware)
Device: Layer 2 Switch, NIC
(Network Access)
Protocols: CDP, lldp, ppp, frame relay, HDLC
PDU: Frames
-Only layer that adds both a header

Question 7

Physical

Answer 7

Physical
Media, signal, & binary transmission
Physical topology

Question 8

Encapsulation De-encapsulation

Answer 8

Encapsulation – headers are added as data travels downward through model (sending)
• De-encapsulation – headers are removed as data travels upward through the model (receiving)