A Simpler Method for Resolving Alert-Info URNs
draft-worley-alert-info-fsm-08

Document Type Active Internet-Draft (individual)
Last updated 2017-05-26
Stream ISE
Intended RFC status Informational
Formats plain text xml pdf html bibtex
Stream ISE state Response to Review Needed
Consensus Boilerplate Unknown
Document shepherd Nevil Brownlee
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to Nevil Brownlee <rfc-ise@rfc-editor.org>
SALUD                                                          D. Worley
Internet-Draft                                                   Ariadne
Intended status: Informational                              May 26, 2017
Expires: November 27, 2017

             A Simpler Method for Resolving Alert-Info URNs
                     draft-worley-alert-info-fsm-08

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.  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 to implement 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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

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

Copyright Notice

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

Worley                  Expires November 27, 2017               [Page 1]
Internet-Draft          Resolving Alert-Info URNs               May 2017

   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.

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  .   6
   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.  Example with "source" and "priority" URNs . . . . . . . . . .  19
   6.  Example 1 of RFC 7462 . . . . . . . . . . . . . . . . . . . .  24
   7.  Examples 2, 3, and 4 of RFC 7462  . . . . . . . . . . . . . .  29
   8.  An Example that Subsets Internal Sources  . . . . . . . . . .  32
   9.  An Example of "alert:service" URNs  . . . . . . . . . . . . .  32
   10. An Example Using Country Codes  . . . . . . . . . . . . . . .  33
   11. Prioritizing Signals  . . . . . . . . . . . . . . . . . . . .  38
   12. Dynamic Sets of Signals . . . . . . . . . . . . . . . . . . .  40
   13. Revision History  . . . . . . . . . . . . . . . . . . . . . .  41
     13.1.  Changes from draft-worley-alert-info-fsm-07 to draft-
            worley-alert-info-fsm-08 . . . . . . . . . . . . . . . .  42
     13.2.  Changes from draft-worley-alert-info-fsm-06 to draft-
            worley-alert-info-fsm-07 . . . . . . . . . . . . . . . .  42
     13.3.  Changes from draft-worley-alert-info-fsm-05 to draft-
            worley-alert-info-fsm-06 . . . . . . . . . . . . . . . .  42
     13.4.  Changes from draft-worley-alert-info-fsm-04 to draft-
            worley-alert-info-fsm-05 . . . . . . . . . . . . . . . .  42
     13.5.  Changes from draft-worley-alert-info-fsm-03 to draft-
Show full document text