A Simpler Method for Processing Alert-Info URNs
draft-worley-alert-info-fsm-07

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SALUD                                                          D. Worley
Internet-Draft                                                   Ariadne
Intended status: Informational                         February 23, 2017
Expires: August 27, 2017

            A Simpler Method for Processing Alert-Info URNs
                     draft-worley-alert-info-fsm-07

Abstract

   The "alert" namespace of uniform resource names (URNs) can be used in
   the Alert-Info header field of Session Initiation Protocol (SIP)
   requests and responses to inform a VoIP telephone (user agent) of the
   characteristics of the call that the user agent has originated or
   terminated.  Based on the URNs in the Alert-Info header field, the
   user agent must select the best available signal to present to its
   user to indicate the characteristics of the call.  This document
   describes a method by which a user agent's designer can, based on the
   user agent's signals and their meanings, construct a finite state
   machine (FSM) to process the URNs to select a signal in a way that
   obeys the restrictions given in the definition of the "alert" URN
   namespace.  In many situations, the resulting FSM is simpler and
   faster than the selection algorithm described in [RFC7462].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 27, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Worley                   Expires August 27, 2017                [Page 1]
Internet-Draft         Processing Alert-Info URNs          February 2017

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Selecting the Signals and Their Corresponding "alert" URNs  .   6
   3.  General Considerations for Processing Alert-Info  . . . . . .   8
   4.  Constructing the Finite State Machine for a Very Simple
       Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Listing the Expressed URNs  . . . . . . . . . . . . . . .  10
     4.2.  Constructing the Alphabet . . . . . . . . . . . . . . . .  10
     4.3.  Constructing the States and Transitions . . . . . . . . .  12
     4.4.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .  15
     4.5.  Examples of Processing Alert-Info URNs  . . . . . . . . .  17
   5.  Example with "source" and "priority" URNs . . . . . . . . . .  19
   6.  Example 1 of RFC 7462 . . . . . . . . . . . . . . . . . . . .  23
   7.  Examples 2, 3, and 4 of RFC 7462  . . . . . . . . . . . . . .  28
   8.  An Example that Subsets Internal Sources  . . . . . . . . . .  31
   9.  An Example of "alert:service" URNs  . . . . . . . . . . . . .  32
   10. An Example Using Country Codes  . . . . . . . . . . . . . . .  32
   11. Prioritizing Signals  . . . . . . . . . . . . . . . . . . . .  37
   12. Dynamic Sets of Signals . . . . . . . . . . . . . . . . . . .  39
   13. Revision History  . . . . . . . . . . . . . . . . . . . . . .  40
     13.1.  Changes from draft-worley-alert-info-fsm-06 to draft-
            worley-alert-info-fsm-07 . . . . . . . . . . . . . . . .  41
     13.2.  Changes from draft-worley-alert-info-fsm-05 to draft-
            worley-alert-info-fsm-06 . . . . . . . . . . . . . . . .  41
     13.3.  Changes from draft-worley-alert-info-fsm-04 to draft-
            worley-alert-info-fsm-05 . . . . . . . . . . . . . . . .  41
     13.4.  Changes from draft-worley-alert-info-fsm-03 to draft-
            worley-alert-info-fsm-04 . . . . . . . . . . . . . . . .  41
     13.5.  Changes from draft-worley-alert-info-fsm-02 to draft-
            worley-alert-info-fsm-03 . . . . . . . . . . . . . . . .  41
     13.6.  Changes from draft-worley-alert-info-fsm-01 to draft-
            worley-alert-info-fsm-02 . . . . . . . . . . . . . . . .  41
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