Definition
SRT (Secure Reliable Transport) is an open-source, low-latency, reliable streaming media transport protocol developed by Haivision. It is implemented based on UDP and adds capabilities such as ARQ (Automatic Repeat reQuest), congestion control, and encryption on top of UDP. SRT is specifically designed for real-time audio and video transmission, with typical end-to-end latency controllable within 120ms to 1 second, far lower than HTTP-based chunked HLS. It is suitable for scenarios that require high real-time performance, such as video return, streaming, remote production, and cross-border live broadcasting.
Compared with RTMP, SRT is based on UDP rather than TCP, resulting in less jitter and lower latency in weak network environments; compared with WebRTC, it is lighter and easier to deploy. When IoT devices (such as in-vehicle cameras, drone video transmission, EV charging station monitoring) perform video streaming over cellular networks, SRT can significantly improve transmission stability under weak network conditions.
Technical Features and Architecture
The SRT technical architecture includes: UDP Transport—based on UDP to avoid TCP head-of-line blocking; ARQ Retransmission—automatically requests retransmission of lost packets to ensure reliable delivery; Encryption—supports AES encryption to ensure transmission security; Congestion Control—dynamically adjusts sending rate according to network conditions; Multiplexing—a single connection can carry multiple streams. SRT uses "Listener" and "Caller" modes and supports NAT traversal and firewall hole punching. Combined with data compression, it can achieve more efficient video transmission in bandwidth-constrained IoT scenarios.
In cross-border scenarios, SRT needs to be used with multi-country IoT SIM cards to ensure that devices can continue to stream stably to the cloud or edge nodes while roaming globally.
Application in IoT and cross-border scenarios
SRT is widely used in: video surveillance — video surveillance cameras and vehicle DVRs stream real-time video to the cloud via SRT; drone video transmission — onboard cameras transmit video back to the ground station in real time via 4G/5G; EV charging station monitoring — charge station on-site monitoring video is sent back via SRT; cross-border live streaming — events and exhibition live streaming achieve low-latency global distribution via SRT. Scenarios such as cross-border video surveillance, global live streaming, and remote operations and maintenance all rely on SRT to achieve low-latency, highly reliable media transmission.
SimtoLink provides connectivity for SRT streaming devices across over 200 countries, supporting stable transmission in weak network environments, helping implement cross-border video surveillance and live streaming scenarios.