OSI model

the OSI model (open systems interconnection)

used to show the theory of networking and its levels; in a simple way

• starts at layer 7 to layer 1

• at each layer pieces of inforamtion is added (aka encapsulation)

OSI layers

1. application

2. presentation

3. session

4. transport

5. network

6. data link

7. physical

application layer

provides interfaces/platforms (browser, email, etc) where applications can transmit data

presentation layer

takes data from application layer and translates into a standardized format

• done thru decryption, compression, etc

session layer

takes translated data and tries to open a connection in the network

• if unsucessful, it sends back an error

• otherwise, it makes a session between the computers and maintains it

transport layer

when the session is made, a signal is sent to transport layer, who chooses which protocol to use to transmit data

• TCP (Transmission Control Protocol): accuracy over speed

• UDP (user datagram protocol): speed over accuracy

network layer

• uses IP address to find the best route to the destination and puts it into an info packet

• uses the OSPF (open shortests path first) and RIP (routing information protocol) methods

• factors: which path is shortest, most reliabel, and faster physical connection

data link layer

takes the info packet and adds a physical address (MAC), which holds the actual destination

• also checks for data corruption and translates into hardware understanding for the next layer

• the MAC is found in the NIC (netwrok interface card) of every computer

physical layer

• sends signals to computers to show the connection is successful; focuses on the hardware part

• devices use binary to send data to each other

which layer transmits and receives data

physical layer; it sends and receives signals between computers in the network

which layer tracks communications between the host and destination computers

network layer; it provides the interface/platform to do so

which layer handles logical addressing

network layer; it uses IP addresses to find the best route

when send data using TCP, what’re the pieces of data called

segments

FTP (file transfer protocol)

used to transfer files between a client and a server with a TCP network

which layer would FTP communicate with

application layer; it deals with user requests

which protocol is best for live video

UDP since it will favor speed; you want the live video to be in real-time regardless of if it cuts out sometimes