Sip ALerting for User Devices

Document Charter Sip ALerting for User Devices WG (salud)
Title Sip ALerting for User Devices
Last updated 2010-07-13
State Approved
WG State Concluded
IESG Responsible AD Richard Barnes
Charter Edit AD (None)
Send notices to (None)


The SALUD (Sip ALerting for User Devices) working group is chartered
  to define a new URN namespace that allows SIP to convey a particular
  alert indication using a name instead of a referenced URI. The
  Alert-Info URN namespace addresses issues encountered in current
  systems that use the Alert-Info header field. It is expected that this
  group will collaborate with the Applications area on the definition of
  the URN namespace.
  RFC 3261 allows a user agent server to provide a specific ringing
  tone, which can be played to the calling user, as a reference (e.g.,
  an HTTP URI) in the Alert-Info header. In some situations, the calling
  user may not be able to understand the meaning of the ringing tone
  being played. For example, a user from a given country may not be
  familiar with the tone used to indicate call waiting in another
  country. Similarly, a hearing impaired person may prefer to get a
  visual call waiting indication instead of a call waiting tone.
  RFC 3261 also allows a user agent client to provide a reference to a
  specific alerting tone, which can be played to the called user (e.g.,
  tones for emergency announcements sent over PBX systems or over the
  local telephone network). As in the previous examples, in some
  situations, the calling user may not be able to understand the meaning
  of the alerting tone being played.
  These issues can be resolved with a mechanism for user agents to
  exchange this type of alerting information in a semantic way. In this
  way, different user agents can use different renderings for the same
  semantics. For example, a user agent client instructed to inform its
  user about a call waiting service being provided can use the
  personalized tones that were previously configured by the user.
  Traditionally, SIP has used status codes to encode session state
  information (e.g., 180 Ringing). Status codes are used by SIP entities
  in an automatic fashion. The information this working group is
  concerned with is related to rendering and may not represent the state
  of the session. Additionally, the exchange of this information does
  not affect the way SIP entities process the session. That is why
  status codes are not an appropriate vehicle to encode this type of
  information. This working group will work on encoding this information
  in URNs.
  In addition to defining URNs that are associated to particular events
  (e.g., a call waiting service is being applied), this working group
  will also define URNs that describe the characteristics of the
  alerting to be applied (e.g., play a short tone followed by a long
  There are a variety of non-interoperable URI conventions and
  proprietary Alert-Info header field parameters to provide this type of
  information today. A standardized set of Alert-Info URNs will increase
  SIP interoperability for this header field by replacing proprietary
  The group will produce a specification that:
  * describes the problem statement.
  * describes requirements and use cases.
  * defines an Alert-Info URN-scheme which allows to resolve the
    interoperability problems described in the use cases.
  * defines the specific Alert-Info URNs identifiers for some of the use
    cases above.
  The Alert-Info URN namespace must be open, so that additional
  Alert-Info URNs can be defined later if necessary.