james.ietf@gmail.com

Applications and Real-Time Multiparty Multimedia Session Control Internet-Draft This document specifies a HTTP header based representation of the Session Description Protocol which can be used in describing media being negotiated or delivered via HTTP. RFC Editor: please remove this section before publication Source code and issues for this draft can be found at https://github.com/fiestajetsam/I-D/tree/main/draft-gruessing-sdp-http.

Services either negotiating or offering media over HTTP may want to express a greater amount of information beyond a MIME type of content and its preference. The Session Description Protocol describes multimedia sessions for the purpose of session announcement and initiation. The Session-Description and Session-Media headers may be used for either a HTTP request or response and may be included as part of any HTTP method.

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 when, and only when, they appear in all capitals, as shown here.

The Session-Description header field conveys the entire session description information, using to describe the structure. Its value MUST be a dictionary containing containing only the following keys, receivers MUST ignore all other values. Dictionary keys MUST be ordered in the order presented in this document, but MAY be omitted where they are explicitly declared as OPTIONAL.

All values within time description fields that represent wall time MUST be values shown as integers which represent NTP timestamps with second resolution. To facilitate ease of parsing, fields that are used to represet a time duration or offset as described in Section 5.10 of MUST NOT use the compact version e.g “1h” instead of “3600”.

The version, represented as an sh-integer that MUST be set 0. The originator of the session, whose value is an sh-list. The order of values present in the list MUST map to the order specified in Section 5.2 of . The name of the SDP, whose values is a string and MUST NOT be empty. An OPTIONAL description of the session, whose value is a string. An OPTIONAL URI reference containing additional information about the session, whose value is a string and SHOULD be represented as . An OPTIONAL email address, whose value is a string and SHOULD be represented using address semantics. An OPTIONAL phone number whose value is a string, which SHOULD be represented as . An OPTIONAL field containing connection data, whose value is an inner-list, and whose elements are each a string type matching the order of elements as defined in Section 5.7 of . This field MUST be set if no media entities in the description contain connection information. An OPTIONAL field containing the proposed bandwidth to be used by the session, whose value is an inner-list with only two elements, the first being a string type whose value corresponds to a bwtype as listed in the IANA registry, or a string prefixed “X-“ to denote an experiemental value. The second element is an integer type and MUST NOT be negative. The key-field field is obsolete and MUST NOT be used. Implementations MUST discard the field if it is received. An OPTIONAL field containing the start and end times of the session, whose value is an inner-list containing two elements - the first being the wall time start time, and the latter being the stopping time. An OPTIONAL field containing the repeat times, whose value is an inner-list containing three elements. The first element contains the repeat interval whose value is an integer, and the second element containing the active duration whose value is an integer. The third element of the offsets from start-time whose value is an inner-list containing two elements containing integer values representing the offsets. An OPTIONAL field containing time zone adjustment information, whose value is an inner-list containing elements where each is an inner-list with two elements; the first element being an integer representing the wall time which the adjustment should take place, and the second element whose value is an integer representing the offset. An OPTIONAL field containing session-level attributes, whose value is an inner-list. Each element may either be a sh-dictionary when representing a value attribute, or a string where it is a property attribute. For value attributes, the contents MUST be a single name/value pair with the name being the attribute name, and the value as a string.

The Session-Media header describes each media element within the session, and at the top level is an sh-list. Each media representation may additionally contain a media title (i), connection information (c), or bandwidth (b).

The Session-Description header MAY be sent at the same time in a response with a HTTP body that also contains the SDP payload for backwards compatibility. In such case the values of the header MUST be identical in semantic meaning to the body payload and not include additional information or redaction. It may also, dependant on implementation be sent in response to a HEAD request - in such cases the body MUST be omitted but the server MUST also send the “application/sdp” Content-Type HTTP header.

TODO: Cover character sets

TODO: Examples

This specification registers the following entry in the Permanent Message Header Field Names registry established by : o Header field name: Session-Description o Applicable protocol: http o Status: standard o Author/Change Controller: IETF o Specification document(s): [this document] o Related information: o Header field name: Session-Media o Applicable protocol: http o Status: standard o Author/Change Controller: IETF o Specification document(s): [this document] o Related information:

TODO: Incorporate things like secure transport (HTTPS), in addition to considerations raised in the structured header draft.

In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This specification defines registration procedures for the message header fields used by Internet mail, HTTP, Netnews and other applications. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] This document specifies the Internet Message Format (IMF), a syntax for text messages that are sent between computer users, within the framework of "electronic mail" messages. This specification is a revision of Request For Comments (RFC) 2822, which itself superseded Request For Comments (RFC) 822, "Standard for the Format of ARPA Internet Text Messages", updating it to reflect current practice and incorporating incremental changes that were specified in other RFCs. [STANDARDS-TRACK] RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This memo defines the Session Description Protocol (SDP). SDP is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. This document obsoletes RFC 4566. This document describes a set of data types and associated algorithms that are intended to make it easier and safer to define and handle HTTP header and trailer fields, known as "Structured Fields", "Structured Headers", or "Structured Trailers". It is intended for use by specifications of new HTTP fields that wish to use a common syntax that is more restrictive than traditional HTTP field values.

The author would like to thank Colin Perkins for very early feedback on this document.