OSI Model Basics

Goes througha. brief of each layer and what happens in each such as what protocols are used and PDU?

What does the OSI stand for?

Open System Interconnections model

How many layers is the OSI?

7

What are the layers of the OSI?

application, presentation, session, transport, network, data link, and physical

application layer(7)

describes the interface between two applications on separate computers

what protocols does the application layer have

HTTP, SMTP, POP3, IMAP4, FTP, Telnet, and RDP

what two categories do the programs use in layer 7

application and utility programs

what's a payload

data that is passed between applications/utility programs and the OS

what do application programs do

provide services to a user

What do utility programs do?

providing services to the system

presentation layer

responsible for reformatting, compressing, and/or encrypting data in a way that the receiving application can read

session layer

describes how data between applications is synced/recovered if messages don't arrive intact at the receiving application

transport layer

responsible for transporting layer 7 payloads from one application to another

what are the protocols used in the transport layer

TCP and UDP

What does TCP stand for?

transmission control panel

what is TCP

connection-oriented protocol (requires connection between the communicating nodes before it will transmit)

what does udp stand for

user datagram protocol

what is udp

a connectionless protocol that does not guarantee delivery and is used for broadcasting(streaming video/audio)

what is a header

controls information that is added at the beginning of the payload to create a message ready to be transmitted to the network layer

encapsulation

process of adding a header to the data inherited from the layer above

decapsulation

removing a header and trailer from a layer below

segment

unit of data that results from subdividing a larger protocol data unit

datagram

udp equivalent of a segment

network layer

responsible for moving messages from one node to another until they reach the destination

IP

internet protocol

what is an IP address

assigned to each node on a network

fragmentation

when a packet is divided into smaller packets

ARP

Address Resolution Protocol. Maps a logical IP address and matches it with a hardware/MAC address

ICMP

Internet Control Message Protocol. Sends error messages and operational information regarding the IP Packet processing

port number

Identifies specific processes or services (Example: Port 80 = HTTP)

data link layer

responsible for interfacing with the hardware on a local area network. Protocols are programmed into the firmware of the NIC (Network Interface Card)

trailer

controls information that is attached to the end of the packet

frame

layer 2 message

MAC address

Media Access Control: a hardware address assigned to a NIC(Network Interface Card) on every device

NIC

Network Interface Card: a piece of hardware that connect a device to a network that contains a MC address

physical layer

Responsible for sending bits using the wired/wireless transmission (Bit: Layer 1 message)