Real Time Messaging Protocol

Real Time Messaging Protocol
Name	Real Time Messaging Protocol
Acronyms	RTMP
Introduced	2000
Developer	Adobe Systems
Status	Deprecated for live delivery; still used for ingestion
Website	Adobe

Real Time Messaging Protocol

The Real Time Messaging Protocol is a proprietary network protocol originally developed for low-latency transmission of audio, video, and data between clients and servers. It was created to support rich media delivery and interactive streaming with codecs and container formats used by popular platforms and products. The protocol influenced and interoperated with a range of technologies, standards, and services across broadcasting, content delivery, and live events.

History

The protocol was released during an era of rapid multimedia innovation involving companies and projects such as Adobe Systems, Macromedia, Apple Inc., Microsoft, Sun Microsystems, RealNetworks, Streaming Media vendors, Akamai Technologies, Level 3 Communications, and Netflix. It evolved alongside formats and standards like Flash Player, H.264, VP8, MPEG-TS, MPEG-DASH, ISO/IEC 14496-12, and initiatives from Moving Picture Experts Group, Internet Engineering Task Force, World Wide Web Consortium, and European Broadcasting Union. The protocol’s lifecycle intersected with events and products such as the launch of YouTube, the growth of Twitch (service), the deployment of iOS, the rise of Android (operating system), and strategic shifts by Adobe Flash Player publishers. Adoption and critique occurred in the context of legal, technical, and market moves involving Federal Communications Commission, European Commission, and major broadcasters like BBC, CNN, Fox Broadcasting Company, and NBCUniversal.

Protocol Overview

The protocol defines a multiplexed, chunked message format and handshake procedure used by servers and clients produced by vendors including Adobe Systems, Wowza Media Systems, NGINX, Inc., Red5, and Librtmp contributors. Designers considered interoperation with container workstreams from QuickTime, Windows Media, RealPlayer, and tuner technologies used by Hulu, Vimeo, Periscope (service), and Ustream. It provides support for command invocation, event notification, and timed media delivery with references to codec identifiers used by Fraunhofer Society and codec implementations from x264, x265, FFmpeg, and proprietary stacks from Cisco Systems and Broadcom.

Architecture and Components

Architectural roles include publishers, edge servers, origin servers, and playback clients implemented by projects such as NGINX Unit, Apache HTTP Server, Lighttpd, JBoss, Node.js, and Go (programming language)-based servers. Components include a handshake mechanism, chunking layer, message layer, and application-layer commands used by media servers like Wowza, Red5, Adobe Media Server, and cloud offerings from Amazon Web Services, Google Cloud Platform, and Microsoft Azure. Interoperability considerations linked to CDN providers such as Akamai Technologies, Cloudflare, and Fastly influenced deployment topologies and peering strategies similar to those of Level 3 Communications and Limelight Networks.

Message Types and Encoding

Messages are typed and framed to carry AMF-encoded commands, audio, video, and data payloads compatible with codec suites from MPEG, ITU-T, H.264/MPEG-4 AVC, AAC, MP3, and Opus. Encodings and serialization interacted with implementations like AMF0, AMF3, and serialization libraries in Flash Player, Flex (software), ActionScript, Java, C++, Python, Ruby on Rails, PHP, and Perl. Media payloads were often packaged with timestamps and sample metadata similar to techniques used by Matroska, MP4, and MPEG-TS containers.

Security and Authentication

Security models for the protocol relied on transport-layer protections and application-layer tokens comparable to patterns used by OAuth 2.0, JWT, TLS, SSL, and mechanisms deployed by Google, Facebook, Twitter, and LinkedIn. Authentication and access control were implemented using API keys, signed URLs, and RTMP-aware modules in server products from Wowza Media Systems and Adobe Systems, integrating with identity providers such as Okta, Auth0, and enterprise directories like Active Directory. Operational security considerations overlapped with standards and regulations enforced by bodies including NIST, ISO/IEC, and regional regulators like Ofcom.

Implementations and Client Support

Open-source and commercial implementations include Red5, nginx-rtmp-module, Librtmp, FFmpeg, GStreamer, and proprietary stacks from Adobe Systems and Wowza. Client support historically centered on Adobe Flash Player and later shifted toward ingest-capable SDKs in OBS Studio, Wirecast, XSplit, vMix, mobile SDKs by Akamai Technologies and cloud SDKs by Amazon Web Services and Microsoft Azure. Integration with ecosystem tools such as VLC media player, Kodi, FFplay, and browser-based players influenced toolchains used by producers at platforms including YouTube Live, Facebook Live, Twitch (service), and broadcasters like Sky Group.

Performance and Scalability

Performance tuning involved chunk size, multiplexing strategies, connection pooling, and server clustering as practiced by CDNs and platforms such as Akamai Technologies, Cloudflare, Amazon CloudFront, and Fastly. Scalability patterns mirrored those in distributed systems research from Google, Twitter, Facebook, and Netflix with techniques like horizontal scaling, load balancing via HAProxy, NGINX, Inc., and autoscaling on Amazon EC2 or Google Compute Engine. Latency, jitter, and packet-loss mitigation borrowed techniques common in streaming stacks used by Twitch (service), YouTube, and live sports broadcasters such as Sky Sports and ESPN.

Extensions and Successors

Successor technologies and extensions include protocols and formats like HTTP Live Streaming, MPEG-DASH, CMAF, WebRTC, and transport innovations such as QUIC and SRT (protocol). Industry migration toward standards was driven by browser vendors including Google, Mozilla Foundation, Apple Inc., and Microsoft and by content platforms including Netflix, YouTube, Amazon Prime Video, and broadcasters like BBC and NHK. Academic and standards communities at IEEE, IETF, and W3C continue to influence low-latency streaming evolution through projects and drafts adopted by vendors and services across the media ecosystem.

Category:Application layer protocols