rtmp-errata-addenda

RTMP Family URI Schemes

Adobe’s Real-Time Messaging Protocol (RTMP) comprises a family of network protocols for transporting streams of time-oriented video, audio, and data messages over IP networks. The URI schemes that are used to identify, locate, and access streaming resources in the RTMP family follow the URI Generic Syntax of RFC 3986, with constraints. This memo describes the syntax constraints and the access semantics for RTMP family URIs.

Copyright © 2023 Michael Thornburgh. All rights reserved.

SPDX-License-Identifier: MIT

Background

RTMP and its TCP-based transport (the RTMP Chunk Stream) are described in the RTMP Specification of December 2012. Errors, omissions, and ambiguities in that specification are addressed in RTMP Errata and Addenda. Coordinated interoperable enhancements to RTMP are described in Enhancing RTMP, FLV With Additional Video Codecs and HDR Support. Transporting RTMP messages over the Secure Real-Time Media Flow Protocol (RTMFP) [RFC7016] is described in Adobe’s RTMFP Profile for Flash Communication [RFC7425].

This memo does not address private or undocumented extensions to the RTMP family for which interoperation is not desired by the extending parties.

The primary operation for dereferencing an RTMP family URI is to connect to the indicated origin server and its abstract target resource. Neither the connection itself nor the target resource have a “representation” or a “media type” in the senses described in RFC 3986, nor is a “retrieval” performed by connecting.

The target resource can have secondary resources, such as streams, shared objects, and remote procedures, that can be accessed according their kinds via the connection. For example, streams may be published or played, shared objects updated or observed, and remote procedures called.

Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

The terms “client”, “server”, “origin server”, “resource”, “secondary resource”, “dereference”, “representation”, and “media type” in this document are to be interpreted as used or described in RFC 3986.

Syntax

RTMP family URIs follow the Generic Syntax of RFC 3986, with constraints. Their syntax is described here using the Augmented Backus-Naur Form (ABNF) [RFC5234] rules from RFC 3986, which are incorporated by reference as though fully set forth here. The host rule is also reproduced here for clarity in the following sections. Note that the rtmp-authority rule defined here is compatible with the authority rule, and rtmp-userinfo is compatible with the userinfo rule.

rtmp-URI  = "rtmp://" rtmp-authority path-abempty [ "?" query ] [ "#" fragment ]

rtmps-URI = "rtmps://" rtmp-authority path-abempty [ "?" query ] [ "#" fragment ]

rtmfp-URI = "rtmfp:"
          / "rtmfp://" rtmp-authority path-abempty [ "?" query ] [ "#" fragment ]


rtmp-authority   = [ rtmp-userinfo "@" ] host [ ":" port ]

rtmp-userinfo    = rtmp-connect-arg *( ":" rtmp-connect-arg )

rtmp-connect-arg = *( unreserved / pct-encoded / sub-delims )

host = IP-literal / IPv4address / reg-name

Authority

The rtmp-authority component, when present, identifies the location of an RTMP origin server which governs a namespace of target and secondary resources.

Note: The bare RTMFP URI form “rtmfp:” does not have an rtmp-authority component (or any other components). All of the other URI forms do. The bare “rtmfp:” URI is used in the APIs of some implementations to indicate instantiation of an RTMFP client according to RFC 7425, but without connecting to a server. Such an instantiation might be used for pure peer-to-peer communication.

Host and Port

The host and optional port components identify the origin server in the network. The host component of the rtmp-authority MUST NOT be empty.

For an rtmp-URI, the host and optional port identify a potential origin server listening for TCP connections, over which RTMP messages are to be sent using the RTMP Chunk Stream as described in the RTMP Specification. If the port is empty or not given, TCP port 1935 is the default.

For an rtmps-URI, the host and optional port identify a potential origin server listening for TCP connections and capable of establishing a TLS connection secured for RTMP Chunk Stream communication. “Secured” means a connection that is authenticated, confidential, and integrity-protected in a manner acceptable to both the client and server. If the port is empty or not given, TCP port 443 is the default.

For an rtmfp-URI where the rtmp-authority is present, the host and optional port identify one or more initial candidate addresses with which to initiate an RTMFP connection according to RFC 7425. The UDP port for the initial candidate addresses, if empty or not specified, is 1935. If host is a reg-name, the initial candidate address set SHOULD comprise all IPv4 and IPv6 addresses to which reg-name resolves.

Userinfo

When connecting to an RTMP server, the connect command can accept or expect additional arguments following the Command Object. The number and types of the additional arguments, their interpretation, and whether they are expected is implementation-specific and is the prerogative of the server.

Often the server expects one or more string arguments to the connect command following the Command Object, for example a developer key, a user name and password, or implementation-specific connection properties.

If the rtmp-authority contains an rtmp-userinfo component, and in the absence of other arrangements between the client and server, the rtmp-userinfo SHOULD be interpreted as a “:” (COLON) separated sequence of potentially empty rtmp-connect-arg strings (as illustrated in the ABNF) to be sent as string arguments to the connect command following the Command Object. Each rtmp-connect-arg SHOULD be percent-decoded before being sent.

Clients SHOULD remove the rtmp-userinfo component from the URI when sending it as the tcUrl property of the connect command’s Command Object or in the Ancillary Data option of an RTMFP Endpoint Discriminator.

Path and Query

The path-abempty and query components identify the abstract target resource within the origin server’s namespace. The meaning of “target resource” is implementation-specific and is the prerogative of the origin server.

Interoperability Note: Some client implementations incorrectly presume the server’s interpretation of the path-abempty component of the URI, specifically by presuming the number of path segments that identify the target resource. These clients then incorrectly interpret the remaining path segments of the original URI as identifying a secondary resource (such the name of a stream to play or publish via the connection to the target resource). This behavior is not in keeping with the spirit of generic URIs (particularly that the authority governs its namespace), is not interoperable, and is NOT RECOMMENDED. Such secondary resources, when encoded in a URI, should instead be identified by the fragment identifier as described in the next section.

Fragment Identifier

Section 3.5 of RFC 3986 describes the fragment component of a generic URI as allowing “indirect identification of a secondary resource by reference to a primary resource and additional identifying information”.

Since an RTMP connection to a target resource has neither a “representation” nor a “media type”, the semantics of the fragment component are unconstrained according to that section.

Often an RTMP client connects to a server to perform a specific operation on a specific secondary resource, such as to publish to or play from a named stream. In cases where the kind of secondary resource and the intended operation are unambiguous, and in the absence of other arrangements between the client and server, the secondary resource MAY be identified by the fragment component. The fragment SHOULD be percent-decoded before being used in secondary resource APIs (for example in a stream play command).

Clients SHOULD remove the fragment component from the URI when sending it as the tcUrl property of the connect command’s Command Object or in the Ancillary Data option of an RTMFP Endpoint Discriminator.

Examples

rtmp://server.example/three/segment/path
rtmp://server.example/three/segment/path#BigBuckBunny
rtmp://[2001:db8:1::2]:19350/something?else
rtmps://server.example/something?else#CosmosLaundromat?aFlag
rtmps://arg1:arg2::arg4@server.example:1943
rtmps://name=Mike;pri=5;exi=3600:7c412a7b6e5892f9c@server.example/path#Caves
rtmfp://:arg2@redirectors.example/two/segments?key=value&flag
rtmfp://arg%3Aone:arg2@redirectors.example/something#BigBuck%42unny
rtmfp:

IANA Considerations

A future version of this memo will request the IANA to update the URI Scheme Registry for the following schemes.

rtmp

This section will request an update to the rtmp provisional scheme registration.

URI scheme name:  rtmp

Status:  provisional

URI scheme syntax:

  rtmp-URI  = "rtmp://" authority path-abempty [ "?" query ] [ "#" fragment ]

URI scheme semantics: This provides location information for the RTMP
   server to which to connect, and identifies a target resource and
   an optional secondary resource in the namespace of the server.  The
   host component of the authority MUST NOT be empty.  The host and
   port components of the authority identify a potential origin server
   listening for TCP connections, over which RTMP messages are to be
   sent using the RTMP Chunk Stream as described in the RTMP Specification
   (as amended).  If port is empty or not given, TCP port 1935 is the
   default.

   See the RTMP Family URI Schemes memo for more specific information
   regarding the semantics of this URI scheme.

Encoding considerations:  The userinfo, path-abempty, query, and fragment
   components represent textual data consisting of characters from
   the Universal Character Set. These components SHOULD be encoded
   according to Section 2.5 of RFC 3986.

Applications/protocols that use this URI scheme name:  The Flash
   runtime (including Flash Player) from Adobe, communication servers
   such as Adobe Media Server, and interoperable clients and servers
   provided by other parties.

Interoperability considerations:  This scheme requires use of RTMP
   and the RTMP Chunk Stream as defined by the RTMP Specification (as
   amended).

Security considerations:  See Security Considerations sections in
   RTMP Errata and Addenda and in RTMP Family URI Schemes.

Contact:  Michael Thornburgh, <zenomt@zenomt.com>.

Author/Change controller:  Michael Thornburgh, <zenomt@zenomt.com>.

References:
   Parmar, H., Ed. and M. Thornburgh, Ed., "Adobe’s Real Time Messaging
   Protocol" ("RTMP Specification"), December 2012,
   <https://rtmp.veriskope.com/docs/spec/>.

   Thornburgh, M., "RTMP Errata and Addenda", September 2023,
   <https://zenomt.github.io/rtmp-errata-addenda/>.

   Thornburgh, M., "RTMP Family URI Schemes", September 2023,
   <TBD>.

rtmps

This section will request provisional registration of the rtmps scheme.

URI scheme name:  rtmps

Status:  provisional

URI scheme syntax:

  rtmps-URI = "rtmps://" authority path-abempty [ "?" query ] [ "#" fragment ]

URI scheme semantics: This provides location information for the secure
   RTMP server to which to connect, and identifies a target resource
   and an optional secondary resource in the namespace of the server.
   The host component of the authority MUST NOT be empty.  The host
   and optional port components of the authority identify a potential
   origin server listening for TCP connections and capable of establishing
   a TLS connection secured for RTMP Chunk Stream communication, over
   which RTMP messages are to be sent using RTMP Chunk Stream as
   described in the RTMP Specification (as amended).  If port is empty
   or not given, TCP port 443 is the default.

   See the RTMP Family URI Schemes memo for more specific information
   regarding the semantics of this URI scheme.

Encoding considerations:  The userinfo, path-abempty, query, and fragment
   components represent textual data consisting of characters from
   the Universal Character Set. These components SHOULD be encoded
   according to Section 2.5 of RFC 3986.

Applications/protocols that use this URI scheme name:  The Flash
   runtime (including Flash Player) from Adobe, communication servers
   such as Adobe Media Server, and interoperable clients and servers
   provided by other parties.

Interoperability considerations:  This scheme requires use of RTMP
   and the RTMP Chunk Stream as defined by the RTMP Specification (as
   amended).

Security considerations:  See Security Considerations sections in
   RTMP Errata and Addenda and in RTMP Family URI Schemes.

Contact:  Michael Thornburgh, <zenomt@zenomt.com>.

Author/Change controller:  Michael Thornburgh, <zenomt@zenomt.com>.

References:
   Parmar, H., Ed. and M. Thornburgh, Ed., "Adobe’s Real Time Messaging
   Protocol" ("RTMP Specification"), December 2012,
   <https://rtmp.veriskope.com/docs/spec/>.

   Thornburgh, M., "RTMP Errata and Addenda", September 2023,
   <https://zenomt.github.io/rtmp-errata-addenda/>.

   Thornburgh, M., "RTMP Family URI Schemes", September 2023,
   <TBD>.

rtmfp

This section will request an update to the rtmfp provisional scheme registration.

URI scheme name:  rtmfp

Status:  provisional

URI scheme syntax:

  rtmfp-URI = "rtmfp:"
            / "rtmfp://" authority path-abempty [ "?" query ] [ "#" fragment ]

URI scheme semantics:  The first form is used in the APIs of some
   implementations to indicate instantiation of an RTMFP client
   according to RFC 7425, but without connecting to a server.  Such
   an instantiation might be used for pure peer-to-peer communication.
   
   The second form provides location information for the server to
   which to connect, and identifies a target resource and an optional
   secondary resource in the namespace of the server.  Connections are
   made using RTMFP (RFC 7016) as described by RFC 7425.  The host
   component of the authority MUST NOT be empty.  If host is a reg-name,
   the initial candidate address set SHOULD comprise all IPv4 and IPv6
   addresses to which reg-name resolves.  The UDP port for the initial
   candidate addresses for the server, if not specified, is 1935.

   See the RTMP Family URI Schemes memo for more specific information
   regarding the semantics of this URI scheme.

Encoding considerations:  The userinfo, path-abempty, query, and fragment
   components represent textual data consisting of characters from
   the Universal Character Set. These components SHOULD be encoded
   according to Section 2.5 of RFC 3986.

Applications/protocols that use this URI scheme name:  The Flash
   runtime (including Flash Player) from Adobe, communication servers
   such as Adobe Media Server, and interoperable clients and servers
   provided by other parties, using RTMFP according to RFC 7425.

Interoperability considerations:  This scheme requires use of RTMFP
   as defined by RFC 7016 in the manner described by RFC 7425.

Security considerations:  See Security Considerations (Section 7) in
   RFC 7425, and Section 9 of RTMP Errata and Addenda.

Contact:  Michael Thornburgh, <zenomt@zenomt.com>.

Author/Change controller:  Michael Thornburgh, <zenomt@zenomt.com>.

References:
   Thornburgh, M., "Adobe's Secure Real-Time Media Flow Protocol",
   RFC 7016, November 2013.

   Thornburgh, M., "Adobe's RTMFP Profile for Flash Communication", 
   RFC 7425, December 2014.

   Thornburgh, M., "RTMP Errata and Addenda", September 2023,
   <https://zenomt.github.io/rtmp-errata-addenda/>.

   Thornburgh, M., "RTMP Family URI Schemes", September 2023,
   <TBD>.

Security Considerations

Several. See the Security Considerations sections of RFC 7016, RFC 7425, and RTMP Errata and Addenda.

Many of the security considerations of RFC 9110 also apply to RTMP.

Author’s Address

Michael C. Thornburgh
Santa Cruz, CA 95060-1950
United States of America
Email: zenomt@zenomt.com
URI: https://zenomt.zenomt.com/card#me