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Human Language Modality Grouping Semantics in Session Description Protocol

Document Type Replaced Internet-Draft (individual)
Author Gunnar Hellstrom
Last updated 2017-06-11
Replaced by draft-hellstrom-slim-modality-grouping
Stream (None)
Intended RFC status (None)
Expired & archived
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Replaced by draft-hellstrom-slim-modality-grouping
Telechat date (None)
Responsible AD (None)
Send notices to (None)
This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at:


In a real-time communication session, there may be a need or preference for receiving the same content in two or more simultaneous modalities. There may also be a need to prioritize which media to use for language communications. This document defines the semantics for grouping media in the Session Description Protocol (SDP) containing human languages in order to assign their relative priority and also grouping media that are desired to be received together. The semantics defined in this document are to be used with the SDP Grouping Framework. Applications are for example a possibility to indicate when a sign language is most desired, but written language an acceptable lower rated alternative, offered for the other party to select between. Applications are also for indication of need for both spoken and written content in a real-time call (captioning) together, or provision of both spoken language original and sign language interpretation of the original language together in a real- time session. These indications are specified for the sending and receiving direction separately.


Gunnar Hellstrom

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)