4. Transport Layer
IMPORTANT In the simplest form, content is sent over the network using protocols like TCP, UDP, or QUIC. These transport layer protocols ensure that data is transmitted between devices, with each having its specific characteristics:
- TCP: Ensures reliable, ordered delivery of data.
- UDP: Sends data without guaranteeing delivery or order, for faster transmission.
- QUIC: A newer protocol that combines the best aspects of TCP and UDP, offering low latency and improved performance, especially for secure communications.
These protocols help manage the flow of data between systems, whether it's for file transfers, browsing, or real-time applications.
| Protocol Name | Description | Common Usage |
|---|---|---|
| TCP (Transmission Control Protocol) | A connection-oriented, reliable transport protocol that ensures error-free delivery of data between devices. | Used for reliable communication in applications like HTTP, FTP, SMTP, and email. |
| UDP (User Datagram Protocol) | A connectionless, lightweight protocol that sends data without ensuring reliability or order. | Used in applications where speed is more important than reliability, such as streaming and VoIP. |
| SCTP (Stream Control Transmission Protocol) | A transport layer protocol that provides reliable, message-oriented communication with multi-homing and multi-streaming capabilities. | Used for applications needing high reliability and resilience, such as in telecommunications. |
| DCCP (Datagram Congestion Control Protocol) | A connection-oriented protocol designed for applications that require timely delivery of data but can tolerate some loss. | Used in multimedia streaming and real-time data applications. |
| RUDP (Reliable User Datagram Protocol) | A variant of UDP that introduces some reliability mechanisms while maintaining the lightweight nature of UDP. | Used in applications that require a combination of low overhead and reliability. |
| FCP (Fibre Channel Protocol) | A transport protocol used in Fibre Channel networks for encapsulating SCSI commands over Fibre Channel. | Used in storage area networks (SANs) for high-speed data transfers between storage devices. |
| iSCSI (Internet Small Computer Systems Interface) | A transport protocol used to link data storage devices over a network using the IP protocol, enabling remote storage access. | Widely used in storage networks to connect servers to storage arrays over IP networks. |
| AEP (Asynchronous Event Protocol) | A protocol for managing communication between devices in distributed systems, often for monitoring or controlling asynchronous events. | Used in specialized applications requiring event notification and control, such as in industrial IoT. |
| QUIC (Quick UDP Internet Connections) | A transport layer protocol developed by Google, designed to improve web performance by reducing connection and transport latency. | Used in modern web applications for faster load times and secure, low-latency communication, especially by services like Google and YouTube. |
| MPTCP (Multipath TCP) | An extension of TCP that enables multiple paths for data transmission, providing fault tolerance and improved bandwidth utilization. | Used in mobile networks and applications requiring high resilience and bandwidth, like cloud services and mobile devices. |
| SPX (Sequenced Packet Exchange) | A transport protocol used by older Novell NetWare systems, similar to TCP but designed specifically for NetWare's networking stack. | Rarely used today but was once a standard protocol in legacy Novell networks. |
| TCP/UDP over IP | Refers to the standard way that TCP and UDP are implemented over the Internet Protocol (IP) in transport layer communications. | Basic for all internet communication across applications that use TCP or UDP. |
These transport protocols facilitate the reliable, efficient, or low-latency communication necessary for diverse applications across different types of networks.
QUIC is becoming increasingly popular, especially with HTTP/3 using QUIC as its foundation to enhance web performance by minimizing connection setup times and providing better security (built-in encryption).