A Simpler Method for Resolving Alert-Info URNs
draft-worley-alert-info-fsm-10

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Last updated 2018-06-22 (latest revision 2018-04-20)
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SALUD                                                          D. Worley
Internet-Draft                                                   Ariadne
Intended status: Informational                            April 20, 2018
Expires: October 22, 2018

             A Simpler Method for Resolving Alert-Info URNs
                     draft-worley-alert-info-fsm-10

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.  The user agent must resolve the URNs into a signal, that
   is, it must select the best available signal to present to its user
   to indicate the characteristics of the call.

   RFC 7462 describes a non-normative algorithm for signal selection.
   This document describes a more efficient alternative algorithm: 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.

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 October 22, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Worley                  Expires October 22, 2018                [Page 1]
Internet-Draft          Resolving Alert-Info URNs             April 2018

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   to this document.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Governing Resolution Algorithms  . . . . . .   4
     1.2.  Summary of the New Resolution Algorithm . . . . . . . . .   5
   2.  Selecting the Signals and Their Corresponding "alert" URNs  .   7
   3.  General Considerations for Processing Alert-Info  . . . . . .   9
   4.  Constructing the Finite State Machine for a Very Simple
       Example . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.1.  Listing the Expressed URNs  . . . . . . . . . . . . . . .  11
     4.2.  Constructing the Alphabet . . . . . . . . . . . . . . . .  11
     4.3.  Constructing the States and Transitions . . . . . . . . .  13
     4.4.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.5.  Examples of Processing Alert-Info URNs  . . . . . . . . .  18
   5.  Further Examples  . . . . . . . . . . . . . . . . . . . . . .  19
     5.1.  Example with "source" and "priority" URNs . . . . . . . .  19
     5.2.  Example 1 of RFC 7462 . . . . . . . . . . . . . . . . . .  24
     5.3.  Examples 2, 3, and 4 of RFC 7462  . . . . . . . . . . . .  29
     5.4.  An Example that Subsets Internal Sources  . . . . . . . .  32
     5.5.  An Example of "alert:service" URNs  . . . . . . . . . . .  32
     5.6.  An Example Using Country Codes  . . . . . . . . . . . . .  33
   6.  Prioritizing Signals  . . . . . . . . . . . . . . . . . . . .  38
   7.  Dynamic Sets of Signals . . . . . . . . . . . . . . . . . . .  40
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  41
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  42
   10. Revision History  . . . . . . . . . . . . . . . . . . . . . .  42
     10.1.  Changes from draft-worley-alert-info-fsm-09 to draft-
            worley-alert-info-fsm-10 . . . . . . . . . . . . . . . .  43
     10.2.  Changes from draft-worley-alert-info-fsm-08 to draft-
            worley-alert-info-fsm-09 . . . . . . . . . . . . . . . .  43
     10.3.  Changes from draft-worley-alert-info-fsm-07 to draft-
            worley-alert-info-fsm-08 . . . . . . . . . . . . . . . .  43
     10.4.  Changes from draft-worley-alert-info-fsm-06 to draft-
            worley-alert-info-fsm-07 . . . . . . . . . . . . . . . .  43
     10.5.  Changes from draft-worley-alert-info-fsm-05 to draft-
            worley-alert-info-fsm-06 . . . . . . . . . . . . . . . .  43
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