Internet DRAFT - draft-individual-ananda-sip-call-indicator
draft-individual-ananda-sip-call-indicator
IETF A. Somadder
Internet Draft Y. Agarwal
Intended status: RFC April 24, 2015
Expires: October 2015
'Urgent' Call Indicator in the Session Initiation Protocol (SIP)
draft-individual-ananda-sip-call-indicator-00.txt
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. This document may not be modified,
and derivative works of it may not be created, and it may not be
published except as an Internet-Draft.
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. This document may not be modified,
and derivative works of it may not be created, except to publish it
as an RFC and to translate it into languages other than English.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on October 24, 2015.
Somadder Expires October 24, 2015 [Page 1]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
Copyright Notice
Copyright (c) 0000 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Abstract
This document proposes an extension to the Session Initiation
Protocol (SIP). This extension provides the ability for calling SIP
User to specify the call urgency while originating a call and for
called SIP user agent to identify that call is an 'Urgent' call.
Table of Contents
1. Introduction...................................................2
2. Conventions used in this document..............................3
3. Motivation.....................................................3
4. Usage of the sip.callindicator parameter.......................4
5. UAC Behavior...................................................5
6. Example........................................................5
6.1. Registration Example.........................................5
7. Security Considerations........................................8
8. Grammar........................................................9
9. IANA Considerations............................................9
9.1. Media Feature Tag............................................9
10. Conclusions..................................................10
11. References...................................................11
11.1. Normative References.......................................11
11.2. Informative References.....................................11
12. Acknowledgments..............................................11
1. Introduction
Often while using mailing services (like using mail clients such as
Outlook), we mark the mails as "Important" to convey to the end user
that the mail has high priority and should be considered as urgent.
Somadder Expires October 24, 2015 [Page 2]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
In normal SIP call establishment it is not possible to indicate to
the called SIP user agent if caller is trying to reach the
destination UA urgently. This draft recognizes the need of a similar
facility during making SIP calls to enable callers to indicate to the
destination UA that the call is or urgent or important nature to be
answered.
This document defines SIP extension which can be used by calling UA
to mark call as an 'Urgent' and Called Party SIP Agent can possibly
define some different action than for a normal call. Like play
different tone or ring even if in 'silent mode'.
Note: Action of called SIP user agent in case of receiving a call
with call indicator marked as 'Urgent' is informative.
2. 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 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
3. Motivation
In day to day life, we see there is need to make calls to other users
and let them know that the call is urgent based on user's situations.
However as long as there is no differentiation between a normal call
and an urgent or important call, receiving end user cannot make the
decision to answer the call or choose to ignore (not answer). The
draft discusses the concept of a call indicator which can be set
explicitly at the time of initiating a call from a SIP UA.
The objective of the draft is to make possible the following:
o UA originating an SIP call shall be able to indicate that the call
is urgent.
o Called UA shall able to identify incoming call as urgent and take
one of the required actions, even when in a busy state (in
meeting, in driving state, etc):
o Play Special ringing
o Override Mute mode and play special ringing
Somadder Expires October 24, 2015 [Page 3]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
o Display special CLI with Urgent indication
However, the possible actions are not scope of this draft and are
left to the implementation of the SIP application residing on UA.
4. Usage of the sip.callindicator parameter
The "sip.callIndicator" media feature tag is a new string parameter,
defined in this document that allows a call to indicate the 'Urgency'
preference related to the call. A receiving UA includes the
"sip.callIndicator" media feature tag in the Contact header field of
REGISTER messages to indicate that it is "Call Indicator" selection-
capable, and a SIP Registrar includes this tag in the Contact header
field of its 200 OK response to confirm the registration of this
preference, all as per RFC 3840 [RFC3840].
A calling UA SHOULD include the "sip.callIndicator" media feature tag
in the Accept-Contact header of an INVITE request in order to express
its desire for a call to be routed to a "Call Indicator" selection-
capable UA. Otherwise, without this tag, 'Urgent' call determination
is not possible until after the call is connected. If a calling UA
includes the "sip.callIndicator" tag and the SIP network elements
that process the call (including the called UAs) implement the
procedures of RFC 3840 and RFC 3841, the call will be preferentially
routed to UAs that have advertised their support for this feature (by
including it in the Contact header of their REGISTER requests, as
documented above).
It is possible for the calling UA to utilize additional procedures
defined in RFC 3840 and RFC 3841 to express a requirement (instead of
a preference) that its call be delivered to "Urgency" preference
selection-capable UAs. However, the calling UA SHOULD NOT require the
"sip.callIndicator" media type. Doing so could result in call failure
for a number of reasons, not only because there may not be any
receiving UAs registered that have advertised their support for this
feature, but also because one or more SIP network elements that
process the call may not support the processing defined in RFC 3840
and RFC 3841. A calling UA that wishes to express this requirement
should be prepared to relax it to a preference if it receives a
failure response indicating that the requirement mechanism itself is
not supported by the called UAs, their proxies, or other SIP network
elements.
Somadder Expires October 24, 2015 [Page 4]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
When calls do connect through the use of "sip.callIndicator" either
as a preference or a requirement, UAs should follow standard SIP call
negotiation procedures.
5. UAC Behavior
A caller wishing to express preferences for an 'urgent' call request
includes Accept-Contact, Reject-Contact, or Request-Disposition
header fields in the request, depending on their particular
preferences. No additional behavior is required after the request is
sent.
The Accept-Contact, Reject-Contact, and Request-Disposition header
fields in an ACK for a non-2xx final response, or in a CANCEL
request, MUST be equal to the values in the original request being
acknowledged or cancelled. This is to ensure proper operation
through stateless proxies.
6. Example
6.1. Registration Example
Bob registers with the "Call Indicator" media feature tag. The
message flow is shown in Figure 1:
SIP Registrar Bob's SIP UA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| |
| REGISTER F1 |
|<------------------------------|
| |
| 200 OK F2 |
|------------------------------>|
| |
Figure 1: "Call Indicator" Media Feature Tag SIP Registration Example
Somadder Expires October 24, 2015 [Page 5]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
F1 REGISTER Bob -> Registrar
REGISTER sip:example.com SIP/2.0
Via: SIP/2.0/TCP bob-TP.example.com:5060;branch=z9hG4bK309475a2
From: <sip:bob-tp@example.com>;tag=a6c85cf
To: <sip:bob-tp@pexample.com>
Call-ID: a84b4c76e66710
Max-Forwards: 70
CSeq: 116 REGISTER
Contact: <sip:bob-
tp@pc33.example.com;transport=tcp>;+sip.callIndicator="urgent"
Expires: 3600
The registrar responds with a 200 OK:
F2 200 OK Registrar -> Bob
SIP/2.0 200 OK
From: <sip:bob-tp@example.com>;tag=a6c85cf
To: <sip:bob-tp@example.com>;tag=1263390604
Contact: <sip:bob-
tp@example.com;transport=tcp>;+sip.callIndicator="urgent"
Expires: 120
Call-ID: a84b4c76e66710
Somadder Expires October 24, 2015 [Page 6]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
Via: SIP/2.0/TCP bob-TP.example.com:5060;branch=z9hG4bK309475a2
CSeq: 116 REGISTER
Expires: 3600
Callers desiring to express a preference for fax will include the
"sip.callIndicator" media feature tag in the Accept-Contact header
of their
INVITE.
INVITE sip:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TCP
client.atlanta.example.com:5060;branch=z9hG4bK74b43
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: Bob <sip:bob@biloxi.example.com>
Accept-Contact: *;+sip.callIndicator="urgent"
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 1 INVITE
Contact: <sip:alice@client.atlanta.example.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 151
The use cases and the examples of using "Call Indicator" are
described for two scenarios below.
Scenario 1: User A gets into a situation and needs to call a close
friend / family member user B to inform about some urgent issue
Somadder Expires October 24, 2015 [Page 7]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
(accident, car broke down with no support around, etc). But B can be
at some place (like office) where B is in meeting or driving where B
prefers to ignore a normal call from A user - or B can decide to call
back later. This will leave user A helpless in case of URGENCY
without any fault of B user.
Scenario 2: User A calls user B who is busy in another call. If the
call that A needs to make to B is an urgent call and Call Waiting is
not available in network, then there needs to be some method to
indicate the urgency of the call to the B user. However, if call
waiting is available, then there should be some specific notification
tone of altering the Call Waiting for Urgent Calls - so that the
destination may realize the call urgency from A user.
As an existing solution, destination SIP UA can set some special ring
tone in advance for calls from a specific originating SIP UA and can
consider all calls from this specific user as important.
In the scenarios mentioned, destination SIP UA can still ignore the
call from originating user if B is in the middle of some other
activity (in urgent meeting, driving, etc). There are no means for
destination SIP UA to identify the call as URGENT call.
An alternative solution there are evidences of applications on smart
phones and PDAs, where the SIP UA can set one or more of number from
contacts as emergency contacts. If this user gets into an accident,
then anyone can take his/her phone and call the emergency contact
from the phone even if the phone's dial-pad is locked.
However, even in such a scenario, it is not possible for user to
indicate through any means to the destination that the call is
urgent. There are no means for B user to identify the call as URGENT
call.
To address the concern of indicating the outgoing call as an 'Urgent'
call, the "Call Indicator" media feature tag is introduced. This
shall allow the originating user to enable the 'Urgent' indicator
while making the call; in addition, the indicator shall also be used
in the SIP UA of destination user to indicate and perform some
actions to show the call needs to be answered.
7. Security Considerations
This media feature tag can be used in ways which affect application
behaviors for both originating and destination SIP User Agents. For
Somadder Expires October 24, 2015 [Page 8]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
example, the SIP caller preferences extension [RFC3841] allows for
call routing decisions to be based on the values of these parameters.
Therefore, if an attacker can modify the values of this tag, they
might be able to affect the behavior of applications. As a result,
applications that utilize this media feature tag SHOULD provide a
means for ensuring its integrity. Similarly, this feature tag should
only be trusted as valid when it comes from the user or User Agent
described by the tag. As a result, protocols for conveying this
feature tag SHOULD provide a mechanism for guaranteeing authenticity.
8. Grammar
This specification defines a new Contact header field parameter,
"+sip.callIndicator". The grammar includes the definitions from
[RFC3261].
The ABNF [RFC5234] is:
contact-params =/ c-p-callindicator
c-p-callindicator = "+sip.callIndicator" EQUAL
DQUOTE "<" callIndicator-tag ">" DQUOTE
callIndicator-tag = "default" / "urgent" / "promotional"
The value of the callIndicator-tag if not present with the Contact
header shall indicate 'default' call indicator.
9. IANA Considerations
This specification adds a new media feature tag to the SIP Media
Feature Tag Registration Tree per the procedures defined in RFC 2506
[RFC2506] and RFC 3840 [RFC3840].
9.1. Media Feature Tag
This section registers a new media feature tag, per the procedures
defined in [RFC2506]. The tag is placed into the sip tree, which is
defined in [RFC3840]. This media feature tag specifies caller
Somadder Expires October 24, 2015 [Page 9]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
preferences for to mark the call as an 'urgent' call. Its value is a
list of token, each of which specifies a particular directive.
Media feature tag name: sip.callIndicator
Token Values: urgent, promotional, default (Normal).
Default: default
ASN.1 Identifier: <XX>
Summary of the media feature indicated by this tag: This feature tag
contains a token string containing a value that indicates the call
indicator associated with the UA instance registering the Contact.
Values appropriate for use with this feature tag: Token with an
equality relationship. Values are:
urgent: The device supports the 'urgent' call indicator as an
originating UA.
promotional: The device supports the 'urgent' call indicator as an
originating UA.
default: The device supports the 'normal' call indicator to show that
the call is a normal call without any preferences to indicate to
destination UA.
The feature tag is intended primarily for use in the following
applications, protocols, services, or negotiation mechanisms: This
feature tag is most useful in a communications application, for
describing the necessity of an originating SIP UA (device, such as a
phone or PDA) to mark the call as 'urgent' to be answered.
Examples of typical use: Allowing the originating SIP UA to mark the
call as an 'urgent' call and routing a call to a specific device with
the information to display special CLI or play special tone to alert
destination SIP UA about the call urgency.
10. Conclusions
<Add any conclusions>
Somadder Expires October 24, 2015 [Page 10]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
11. References
11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, Internet Mail Consortium and
Demon Internet Ltd., November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
11.2. Informative References
[3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-
1583.
[Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in
TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp.
1573-1583.
12. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
Somadder Expires October 24, 2015 [Page 11]
Internet-Draft draft-individual-ananda-sip-call-indicator-00
Authors' Addresses
Ananda Somadder
Bangalore, India
Phone: +91-9980982520
Email: anandasomadder@gmail.com
Yogendra Agarwal
Bangalore, India
Phone: +91-9900085351
Email: yogendra.agarwal@gmail.com
Somadder Expires October 24, 2015 [Page 12]
