The TCP/IP protocol suite

TCP/IP is the collection of protocols that makes the internet work, named after its two most important members, the Transmission Control Protocol and the Internet Protocol. It is organised as a stack of layers, each responsible for one aspect of communication and building on the one below. This layered design lets very different networks and applications interoperate, because each layer only needs to cooperate with the matching layer on the other machine, while lower layers handle the details of moving the data.

The Internet Protocol (IP) handles addressing and routing. Every device on the network has an IP address, and IP wraps data into packets that carry source and destination addresses so that routers along the way can forward each packet toward its target, possibly across many intermediate networks. IP itself does not guarantee that packets arrive, that they arrive in order, or that none are duplicated; it simply makes a best effort to deliver them.

The Transmission Control Protocol (TCP) adds the reliability that many applications need. It splits a stream of data into segments, numbers them, and uses acknowledgements and retransmission to ensure every segment arrives correctly and in order, reassembling them at the destination. Other protocols in the suite serve different needs, and higher-level services such as the web, email, and the Domain Name System run on top of TCP/IP. Concepts like port numbers, URLs, and APIs all depend on this underlying addressing and delivery machinery.

Frequently asked questions

What is the difference between TCP and IP?

IP handles addressing and routing, getting packets toward the right destination, while TCP runs on top of it to guarantee that the data arrives complete and in the correct order.

Why is TCP/IP arranged in layers?

Layering separates the job of communication into independent levels, so different networks and applications can interoperate as long as each cooperates with the matching layer on the other end.

Does IP guarantee delivery?

No. IP makes only a best effort to deliver packets and does not ensure they arrive, arrive in order, or are not duplicated; TCP adds those reliability guarantees.