1.1 Understanding the OSI Model

What is the acrynoym to remember the OSI Model?

Please Do Not Throw Sausage Pizza Away

or

All People Seem To Need Data Processing

What are the 7 layers of the OSI Model from 1>7

Physical

Data Link

Network

Transport

Session

Presentation

Application

What does OSI stand for?

Open Systems Interconnection reference model

what does the OSI model do?

describes how traffic moves from one side of the network to another, it is a common way for all IT people to communicate how data is moving

Layer 1 is which layer?

The Physical Layer

the physical layer is responsible for what?

sending bits via a wired or wireless transmission

bits can be transmitted as what 3 things?

wavelengths in the air

voltage on a copper wire

light ( via a fiber-optic cable)

what does PDU stand for?

protocol data unit

what is a PDU?

a group of bits as it moves from one layer to the next

which layer consists of signaling, cabling, connectors ( cables, NIC, HUB)

layer 1 - physical

if you have a physical layer problem you need to do what (5)?

fix your cabling, punch downs, run loopback tests, test/replace cables, swap adapter cards

layer 2 is called what layer?

data link layer

layer 2 - data layer is also called the what ?

the switching layer

which layer consists of frames, mac addresses, EUI-48, EUI-64, switches

layer 2 - data link layer

mac addresses are also called what (4)?

layer 2 addresses, physical address, hardware address, or data link layer addrress

what does MAC stand for in MAC address?

Media Access Control

switches make forewarding decisions based on —— addresses so its called the switching layer

mac

mac addresses are found on what?

NIC ( Network Interface Cards )

the type of networking hardware or technology used on a network determines the data link layer ——- used. Ethernet and Wifi are examples

protocol

the data link layer puts control information in the —— and the —- of the packet

header and trailer

once the data link layer has placed control info in the header and trailer, the entire data link layer message is called a —-

frame

what is layer 3 known as ?

the network layer

layer 3 the network layer is also called the what?

“routing” layer

layer 3 the network layer makes forwarding decisions based on the what?

Internet protocol (IP)

the network layer is responsible for moving messages from one —- to another until they reach the destination host

node

data on the physical layer is known as ?

bits

data on the data link layer is known as

frames

data on the network layer is known as a

packet

what does the network layer consist of (3)

IP addresses, routers, and packets

the principal protocol used in the network layer ( layer 3 ) is the ?

IP ( internet protocol)

what does the network layer add to the datagram?

it’s own header

the entire network layer message is called a ?

packet

the ip address is an addres that is assigned to each —- on a network

node

the network layer uses the ip address to uniquely identify each ——

host

the ip relies on several —— protocols to find the best route for a packet to take to reach destination. ICMP and ARP are examples

routing

network layer protocol will divide large packets into smaller packets in a process called ——

fragmentation

layer 4 is also called the what layer

transport layer

the transport layer is responsible for transporting ——- layer payloads from one application to another

application

what are the two main transport layer protocols found at the transport layer

UDP & TCP

what is the difference between the two transport protocols TCP & UDP?

TCP guarntees delivery while UDP does not

tcp stands for ?

transmission control protocol

tcp is connection-oriented true or false?

true

UDP is connectionless true or false

true

protocols add control information in an area at the beginning of the payload called the —- ?

header

the proces of adding a header to the data inherited from the layer above is called what?

encapsulation

if a message is too large the TCP divides it into smaller messages called

segments

when udp divides a message into smaller messages its called a

datagram

what things are found at the transport layer 4?

tcp segments, udp datagram, port numbers

what three layers of the OSI model are typically intertwined making it difficult to distinguish between them?

application, presentation, and session

this layer of the OSI model describes how data between applications is synched and recovered if messages don’t arrive intact at the receiving application. communication between one end point and another

layer 5 session layer

what types of protocols are found in the session layer 5

control protocols , and tunneling protocols

which 3 layers are often intertrwined making them difficult to distinguish between

application, presentation, and session

what does API stand for?

application programming interface

this call is the method an application uses when it makes a request to the OS

API call

layer 6 is also called the —— layer

prsentation

this layer is responsible for reformatting, compresing, and/or encrypting data in a way that the receiving application can read

presentation layer

character encoding, encryption, (SSL/TLS) is found at this layer

presentation layer 6

layer 7 is also known as the —— layer

applicatation

this layer describes the interface between two applications, on seperate computers, the layer we get to see

layer 7 application layer