A protocol is a set of rules that define how two networked computers should talk to each other.
When information is sent from one computer to another guidelines and rules that both computers follow must be in place. Without guidelines and rules, the computer receiving the information won't be able to process and understand it. Protocols can be thought of as the guidelines and rules that dictate the specific ways that information is to be broken down, packaged, addressed, and transported by a sender, and how the receiver should unpack, reassemble, and interpret the information received.
There are different kinds of protocols used for different purposes over the Internet. The different types of protocols are seperated into four different layers called the application, transport, internet, and link layers. The complete stack of protocols is used every time information moves across the Internet.
- Application layer protocols: The application layer includes protocols used by computer applications to talk to eachother. A few examples of application layer protocols used over the Internet include HTTP, FTP, SMTP, POP3, Telnet, and TLS/SSL.
- Transport layer protocols: Protocols operating at the transport layer determine how information should be packetized, and ensure that the information is delivered in the right order and that no information is lost along the way. TCP is the transport layer protocol used to transfer information across the Internet. Other networks may use TCP or other transport layer protocols.
- Internet layer protocols: Internet layer protocols dictate how information is moved from between network boundaries. IP is protocol used to communicate over the Internet, but other internet layer protocols are used for other types of Wide Area Networks. IP is the protocol your Internet Service Provider (ISP) uses to communicate with other ISPs, hosts, and any other connected networks.
- Link layer protocols: Protocols such as PPP, Ethernet, and DSL operate at the link layer. Think of the link layer as the standards and methods used to establish a network connection and move information between two computers in a local network.
Frequently Asked Questions
What protocols are used when I visit a website?
When you visit a website, such as Learn the Net all four protocol layers come into play.
- Application layer:Your browser uses HTTP to communication with the web server. It may also use SSL/TLS to encrypt communication between your browser and the web server. Browser's are capable of using several other application layer protocols, but HTTP and SSL/TLS are the two used most frequently.
- Transport layer: TCP defines how information should be packetized for transport, and helps ensure that the packets are received in the right order, and that no packets are lost in transmission.
- Internet layer: IP protocols come into play as the packets move for your ISP across the Internet. All of the network connections that the packets move through operate according to IP protocols.
- Link layer: Your network connection to your ISP is negotiated by a link layer protocol such as DSL or Ethernet.
No matter what device you use to access the Internet, the resource you access, or where you get your Internet connection, the entire stack of all four layers will come into play every time you use the Internet. The amazing thing is, all of this happens completely seamlessly and with shocking speed.