Does Video Streaming Use TCP or UDP?

Yes. In video streaming, both TCP and UDP are used, each serving a specific purpose. Understanding the nuances between these two protocols will provide insights into how video streaming is designed and implemented.

Understanding UDP and TCP

UDP (User Datagram Protocol) is used when timely delivery of datagrams (packets) is more critical than reliability. UDP is a simpler, connectionless protocol that transmits data as quickly as possible without ensuring that the data has arrived at its destination. This makes it ideal for real-time applications like video streaming where lag or latency could be detrimental to the user experience. TCP (Transmission Control Protocol) is used when reliable delivery is essential. TCP ensures that data is delivered in the correct order and without errors, but this comes at the cost of potentially higher latency.

History of Video Streaming

In the late 1990s, one of the simplest ways to share a video on a webpage was to embed it in the homepage and download it over HTTP (which is a TCP-based protocol), unless you used FTP (also TCP-based) to download the video.

The introduction of proprietary streaming protocols like Real Data Transport (RDT) by Real Networks helped in providing a faster and more efficient way to stream media. RDT, which can use either UDP or TCP, was encapsulated over UDP but provided a fallback to TCP if necessary.

Netscape, along with Real Networks, developed Real Time Streaming Protocol (RTSP), which leverages Real-time Transport Protocol (RTP) for streaming media. RTP generally runs over UDP, but can also be made to use TCP if needed. The control protocol for RTP is conveniently named RTCP and runs over UDP.

Modern Streaming Protocols

As streaming technologies evolved, more protocols emerged to support the growing demand for real-time content delivery. Flash (now by Adobe) uses the Real-Time Messaging Protocol (RTMP), which is typically TCP-based, for streaming Flash content to web browsers.

The Multicast Backbone (MBONE), an experimental technology using IP multicasting for optimized media delivery, is another example where UDP is preferred due to its inability to guarantee delivery reliability, which is a key requirement for TCP.

Microsoft's NetShow and later Media Server supported both TCP and UDP, but ultimately shifted to RTSP which can use either protocol. The MPEG transport stream (MPEG-TS) can be encapsulated over both TCP and UDP, although MPEG-H Part 1 standardizes on a newer MPEG media transport (MMT) format for modern implementations.

Contemporary Streaming Protocols

In today's streaming landscape, HTTP Live Streaming (HLS) and MPEG-DASH (Dynamic Adaptive Streaming over HTTP) utilize HTTP (TCP-based), allowing for adaptive bitrate streaming over the internet. These protocols cater to a wide range of devices and network conditions, making them highly versatile.

WebRTC, a project focused on real-time communication, includes a protocol called Stream Control Transmission Protocol (SCTP), which blends the best features of both UDP and TCP. SCTP is designed for two-way video conferencing, rather than one-way streaming, making it a modern alternative that offers better performance and reliability in real-time applications.

Conclusion

In summary, video streaming heavily relies on both TCP and UDP, depending on the specific requirements of the application. UDP provides low-latency, real-time delivery, while TCP ensures reliability and order of data packets. As streaming technologies continue to evolve, understanding the interplay between these protocols is crucial for efficient and effective implementation.