Day 3 - OSI model and TCP/IP Suite

Question 1

What does a networking model do?

Answer 1

Categorizes and provides a structure for networking protocols and standards

Question 2

What is a networking protocol?

Answer 2

A set of logical rules defining how network devices and software should work

Question 3

OSI model

Answer 3

Open Systems Interconnection model
Open (not proprietary)
Conceptual model that categorizes and standardizes the different funtions in a network
Created by ISO (late 70s early 80s)
Network functions (protocols) are divided into 7 layers
*Not in use but influences thinking of engineers

Question 4

Application Layer

Answer 4

Layer 7
Closest to the end user
Interacts with software applications
ex - https
Functions: identifying communication partners/synchronizing communication

Question 5

Presentation Layer

Answer 5

Layer 6
Data is in an “application format” (must be ‘translated’ to different format to be sent over the network
Translates between app and network formats

Question 6

Session Layer

Answer 6

Controls dialogues (sessions) between communicating hosts
Establishes, manages, terminates connections between the local app and the remote app

Question 7

Transport Layer

Answer 7

Layer 4
Segments/reassembles data for comms between hosts (smaller data segments are less likely to cause tranmission problems)
Provides host to host communication

Question 8

Network Layer

Answer 8

Layer 3
Provides connectivity between end hosts on different networks
Provides logical addressing (IP)
Provides path selection between source and destination

Question 9

Data Link Layer

Answer 9

Layer 2
Provides node-to-node connectivity and data transfer
Defines how data is formatted for transmission over a physical medium
Detects and (possibly) corrects Physical layer errors
Uses addressing (seperate from Layer 3 addressing)

Question 10

Physical Layer

Answer 10

Layer 1
Defines physical characteristics of the medium used to transfer data between devices (eg - voltage levels, max transmission dist, physical connectors, etc.)
Digital bits are converted into electrical signals or radio

Question 11

Data encapsulation process

Answer 11

Last 3 layers prepare data (application layers)
Layer 4 header is added to make a segment
Layer 3 header is added to make a packet (IP addressing)
Layer 2 header/trailer added to make a frame
Data is transmitted over Layer 1

Question 12

PDUs

Answer 12

Protocol Data Units
Refers to the terms data, segment, packet, frame (a layer 2 PDU)
*At Layer 1 the PDU is a bit

Question 13

TCP/IP suite

Answer 13

Conceptual model and set of communications protocols used across networks
Developed by DOD through DARPA
The model actually in use in modern networks

Question 14

Adjacent Layer Interaction

Answer 14

Interaction between different layers of the OSI model