Data Encapsulation

It is the process of breaking a message into packets, adding info to those packets, and then sending them off through the transmission medium

Transmission Control Protocol (TCP)

• Protocol that allows devices to communicate over a network

Address Resolution Protocol (ARP)

• Protocol used to determine the MAC address of the host using the destination IP

Maximum Transmission Unit (MTU)

• Term for the largest size of data that can be transmitted through the given network

Encapsulation

• Process of breaking a message into packets, adding controls and other information, and then transmitting the message through the medium

The TCP IP Model can be broken up into 4 parts, each part adding something to the message until it is ready to be able to be sent to the corresponding PC. 

The Application Layer is the one that prepares the data to be formatted into the frame.

Application Layer = Data

The Transport Layer breaks the data into segments, and adds sequencing and control information. 

• This includes the source and destination ports, along with the TCP/UDP header.

Transport Layer = Segment

The Internet Layer converts these segments into packets, and adds network and device addresses.

• This includes the source and destination IP's, along with the IP header.

Internet Layer = Packets

The Link Layer converts these packets into frames, and adds physical device information.

• This includes the source and destination MAC's, along with the Frame header

• This also includes a frame check sequence for error detection

• This also includes converting the frames into zeros and ones for transmission across the network.

Link Layer = Frames

Application Layer prepares the data to be sent

Transport Layer breaks the data into pieces

Internet Layer adds logical addresses

Link Layer adds physical addresses.

This process happens in reverse on the receiving device, starting from the Link Layer and going up to the Application Layer. It builds the packets up instead of breaking them down.

Note that the OSI model uses the term protocol data unit (PDU) instead of the terms frame, packet, and segment. Also known as a Payload.  

TCP uses a three-way handshake in order to establish connection with a systems port. Examining a TCP packet would reveal flag indicators

In the routing process, ARP is used by computers to get the destination devices MAC address. A computer will send out an ARP packet with the destination device's IP address and it will be requesting a MAC address.

ARP uses Dest. IP to get Dest. MAC
(Both source and destination IP's have to be on the same network)

Computer A and computer B are trying to communicate.

The frame created by computer A contains 4 addresses
Layer 2 Source Address (MAC address of Computer 1)
(003482348)
Layer 2 Destination Address (MAC address of Router)
(045342jksfhsb)

Layer 3 Source Address (IP of Computer 1)
(192.168.0.1)
Layer 3 Source Address (IP of Computer 2)

This frame gets sent to router 1. Router 1 then removes the MAC address header and changes it to this:
Source MAC address being that of the router
Destination MAC address being that of Computer 2

*Note that all IP addresses and MAC addresses aren't real and are only imitations of real MAC and IP addresses