Protocols ⇒ In a computer network, machines talk to each other using protocols

Packets ⇒ Are nothing but streams of bits running as electric signals on physicals.

It consists of :

• Header

  ⇒ has a Protocol-specific and has receiving host

• Payload

  ⇒ The actual information (in layer 3)

Open System Interconnection(OSI)

consists of seven layers and is used as a reference for the implementation of actual protocols

• Physical Layer - The actual hardware.
• Data Link Layer - Data transfer method (802x ethernet). Puts data in frames and ensures error free transmission. Also controls the timing of the network transmission. Adds frame type, address, and error control information. IEEE divided this layer into the two following sublayers.
• Network Layer - IP network protocol. Routes messages using the best path available.
• Transport Layer - TCP, UDP. Ensures properly sequenced and error free transmission.
• Session Layer - The user's interface to the network. Determines when the session is begun or opened, how long it is used, and when it is closed. Controls the transmission of data during the session. Supports security and name lookup enabling computers to locate each other.
• Presentation Layer - ASCII or EBCDEC data syntax. Makes the type of data transparent to the layers around it. Used to translate date to computer specific format such as byte ordering. It may include compression. It prepares the data, either for the network or the application depending on the direction it is going.
• Application Layer - Provides services software applications need. Provides the ability for user applications to interact with the network

Encapsulation

Encapsulation is adding extra protocols along with data to send it from one point to another via a network. Encapsulation always takes place at the sender's side to send data properly.

TCP/IP model

is a real-world implementation of a networking stack and is the protocol stack used on the Internet