TCP (Transmission Control Protocol) is a connection-oriented protocol. It provides reliable, ordered, and error-checked delivery of a stream of bytes between applications running on different hosts.
Key Characteristics of TCP
Here's a breakdown of what "connection-oriented" means in the context of TCP and other important characteristics:
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Connection-Oriented: Before data can be exchanged, TCP establishes a connection between the sender and receiver using a three-way handshake. This ensures both parties are ready and aware of the impending communication. This is in contrast to connectionless protocols like UDP, which send data without establishing a connection first.
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Reliable: TCP ensures that data is delivered to the destination in the correct order and without errors. It uses sequence numbers and acknowledgments to track data segments and retransmits any segments that are lost or corrupted.
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Ordered Delivery: TCP guarantees that data arrives in the same order it was sent. This is crucial for applications that rely on a specific sequence of data, such as file transfers or streaming video.
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Error Checking: TCP incorporates checksums to detect errors during transmission. If an error is detected, the segment is discarded and retransmitted.
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Flow Control: TCP regulates the amount of data that is sent to prevent the receiver from being overwhelmed. This is achieved through a sliding window mechanism.
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Congestion Control: TCP monitors network congestion and adjusts its sending rate accordingly. This helps to prevent network overload and ensures fair sharing of network resources.
TCP vs. UDP
To understand TCP better, it's helpful to compare it to UDP (User Datagram Protocol), another common transport layer protocol:
| Feature | TCP | UDP |
|---|---|---|
| Connection | Connection-oriented | Connectionless |
| Reliability | Reliable | Unreliable |
| Ordering | Ordered | Unordered |
| Error Checking | Yes | Yes (but minimal) |
| Flow Control | Yes | No |
| Congestion Control | Yes | No |
| Speed | Slower (due to overhead) | Faster (less overhead) |
| Use Cases | Web browsing, email, file transfer | Streaming, online gaming, DNS lookup |
Examples
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Web Browsing (HTTP): When you visit a website, your browser uses TCP to establish a connection with the web server. TCP ensures that the web page's HTML, CSS, and JavaScript files are delivered reliably and in the correct order.
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Email (SMTP, IMAP, POP3): Email clients use TCP to send and receive emails. TCP ensures that the email messages are delivered reliably and without errors.
In summary, TCP is a connection-oriented protocol that provides reliable, ordered, and error-checked delivery of data, making it suitable for applications where data integrity is paramount.
