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SRT (Secure Reliable Transport)

SRT (Secure Reliable Transport) is an open-source transport protocol for contribution-grade IP video. Originally developed by Haivision and now maintained by the SRT Alliance (open-source on GitHub), SRT is widely used across the broadcast industry as a low-latency, reliable, encrypted alternative to RTMP for sending live video over unmanaged IP networks.

It is a general-purpose industry standard, not a Netflix-specific technology.

Core properties

  • UDP-based with reliability layered on top. Built on UDT, which adds retransmission + packet reordering + forward error correction over UDP — avoiding TCP's head-of-line blocking.
  • Low latency. Typically sub-second glass-to-glass, tunable via the latency parameter (20-8000ms).
  • AES encryption. Built-in AES-128/256 encryption at the transport layer.
  • Lossy-network resilience. Designed for contribution over unmanaged / congested internet — uses ARQ (automatic repeat request) + FEC to recover from packet loss.
  • Caller / listener / rendezvous handshakes. Supports NAT traversal via rendezvous mode.

Role at Netflix

Per sources/2026-04-17-netflix-the-human-infrastructure-live-operations: SRT is one of the contribution-path legs Netflix uses for show-critical feeds, specifically under the "dedicated enterprise- grade internet and robust SRT contribution systems" tier.

In Netflix's strict contribution hierarchy:

  1. Dedicated video fiber (highest priority)
  2. Single-feed satellite
  3. Dedicated enterprise internet + SRT (the IP-contribution leg)

Also referenced in sources/2026-04-02-netflix-smarter-live-streaming-vbr-at-scale as one of the input protocols accepted by AWS Elemental MediaLive (Netflix's live encoder substrate).

Why SRT specifically

For live contribution over the public internet, the alternative protocols are RTMP (TCP-based, head-of-line blocking, deprecated), RIST (similar profile to SRT, less widely deployed), and WebRTC (peer-to-peer oriented, different design target). SRT has become the de facto industry standard for professional contribution over IP because it provides sub-second latency, built-in encryption, and tolerates the packet loss that inevitably occurs on unmanaged internet paths.

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