Network Working Group P. Jones
Request for Comments: 4102 Cisco Systems, Inc.
Category: Standards Track June 2005
Registration of the text/red MIME Sub-Type
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (2005).
This document defines the text/red MIME sub-type. "Red" is short for
redundant. The actual RTP packetization for this MIME type is
specified in RFC 2198.
Text is an important component of any multimedia communication
system. Like audio, the transport of text can benefit from the use
of redundancy in order to improve reliability and end-user
RFC 2198  defines an RTP  payload format for redundant audio
data. The format defined in that document is quite suitable for
providing redundancy for text, as well as audio.
RFC 4103  specifies one usage of RFC 2198 and the text/red MIME
type for the transport of redundant text data.
This memo provides the MIME sub-type registration information for
text/red. While this document focuses on the use of this MIME sub-
type in SDP , the application of this MIME sub-type is not
restricted to SDP.
Jones Standards Track [Page 1]RFC 4102 text/red MIME Sub-Type June 20052. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 .
3. IANA Considerations
One new MIME sub-type has been registered by the IANA, as described
MIME media type name: text
MIME subtype name: RED
rate: the RTP clock rate of the payload carried within the RTP
packet. Typically, this rate is 1000, but other rates MAY be
specified. This parameter MUST be set equal to the clock rate of
the text payload format carried as the primary encoding.
pt: a comma-separated ordered list of RTP payload types
enumerating the primary, secondary, etc., in accordance with RFC
2198. Because comma is a special character, the list MUST be a
quoted-string (enclosed in double quotes). For static payload
types, each list element is simply the type number. For dynamic
payload types, each list element is a mapping of the dynamic
payload type number to an embedded MIME content-type specification
for the payload format corresponding to the dynamic payload type.
The format of the mapping is:
dynamic-payload-type "=" content-type
If the content-type string includes a comma, then the content-
type string MUST be a quoted-string. If the content-type string
does not include a comma, it MAY still be quoted. Because it is
part of the list, which must itself be a quoted-string, the
quotation marks MUST be quoted with backslash quoting as specified
in RFC 2045 . If the content-type string itself contains a
quoted-string, then the requirement for backslash quoting is
Optional parameters: ptime, maxptime (these attributes are originally
defined in RFC 2327  and RFC 3267 , respectively)
Restrictions on Usage:
This type is defined only for transfer via RTP.
It shall not be defined for a storage format.
Jones Standards Track [Page 2]RFC 4102 text/red MIME Sub-Type June 2005
See restrictions on Usage above; this section is included per
the requirements in RFC 3555 .
Security considerations: Refer to section 5 of RFC 4102.
Interoperability considerations: none
Published specification: RFC 2198
Applications which use this media type:
Text streaming and conferencing tools.
Additional information: none
Person & email address to contact for further information:
Paul E. Jones