[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 rfc7135                      Standards Track
Network Working Group                                            J. Polk
Internet-Draft                                             Cisco Systems
Intended status: Informational                         February 22, 2013
Expires: August 26, 2013

  IANA Registering a SIP Resource Priority Header Field Namespace for
                     Local Emergency Communications


   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header field namespace 'esnet' for local emergency
   session establishment to a public safety answering point (PSAP),
   between PSAPs, and between a PSAP and first responders and their
   organizations, and places this namespace in the IANA registry.

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 August 26, 2013.

Copyright Notice

   Copyright (c) 2013 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

Polk                     Expires August 26, 2013                [Page 1]

Internet-Draft           Emergency RPH Namespace           February 2013

   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Rules of Usage of the Resource Priority Header field . . . . .  4
   3.  "esnet" Namespace Definition . . . . . . . . . . . . . . . . .  7
     3.1.  Namespace Definition Rules and Guidelines  . . . . . . . .  7
     3.2.  The 'esnet' Namespace  . . . . . . . . . . . . . . . . . .  7
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  IANA Resource-Priority Namespace Registration  . . . . . .  8
     4.2.  IANA Priority-Value Registrations  . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  Normative References . . . . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

Polk                     Expires August 26, 2013                [Page 2]

Internet-Draft           Emergency RPH Namespace           February 2013

1.  Introduction

   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header (RPH) field namespace 'esnet' for local
   emergency usage and places this namespace in the IANA registry.  The
   SIP Resource-Priority header field is defined in RFC 4412 [RFC4412].
   The new 'esnet' namespace is to be used for inbound calls towards a
   public safety answering point (PSAP), between PSAPs, and between a
   PSAP and first responders or their organizations within managed IP
   networks.  This namespace is not for use on the open public Internet
   because it can be trivially forged.

   Adding a RPH with the 'esnet' namespace can be differentiated from
   the marking of an emergency call using a service urn as defined in
   RFC 5031 in that the RPH specifically requests preferential treatment
   in networks which honor it, while the marking merely identifies an
   emergency call without necessarily affecting resources allocated to
   it.  It is appropriate to use both where applicable.  RPH with
   'esnet' may also be used within public safety networks for SIP
   sessions that are not emergency calls and thus not marked per RFC

   This new namespace is included in SIP requests to provide an explicit
   priority indication within controlled environments, such as an IMS
   infrastructure or Emergency Services network (ESInet) where misuse
   can be reduced to an acceptable level because these types of networks
   have controls in place.  The function facilitates differing treatment
   of emergency SIP requests according to local policy, or more likely,
   a contractual agreement between the network organizations.  This
   indication is used solely to differentiate certain SIP requests,
   transactions or dialogs, from other SIP requests, transactions or
   dialogs that do not have the need for priority treatment.  If there
   are differing, yet still understandable and valid Resource-Priority
   header values in separate SIP requests, then this indication can be
   used by local policy to determine which SIP request, transaction or
   dialog receives which treatment (likely better or worse than

   Application Service Providers (ASP) securely connected to an ESInet
   may have sufficient controls policing the header, and a trust
   relationship with the entities inside the ESInet.  SIP requests from
   such ASPs could make use of this 'esnet' namespace for appropriate
   treatment when requests are passed from the ASP to the ESInet.

   The 'esnet' namespace may also be used on calls from a PSAP or other
   public safety agency on an ESInet towards a private or public
   network, ASP or UA ("call back") when priority is needed.  Again, the
   request for priority is not for use on the public Internet due to the

Polk                     Expires August 26, 2013                [Page 3]

Internet-Draft           Emergency RPH Namespace           February 2013

   ease of forging the header.

   This document merely creates the namespace, per the rules within
   [RFC4412] as updated by [I-D.rosen-rph-reg-policy], necessitating
   IETF review for IANA registering new RPH namespaces and their
   relative priority-value order.

   There is the possibility that within emergency services networks a
   Multilevel Precedence and Preemption (MLPP)-like behavior can be
   achieved (likely without the 'preemption' part), provided local
   policy supports enabling this function.  For example, calls placed
   between law enforcement agents could be marked similarly to MLPP
   systems used by military networks, and some of those calls could be
   handled with higher priority than an emergency call from an ordinary
   user.  Therefore the 'esnet' namespace is given five priority-levels
   instead of just one.  MLPP-like SIP signaling is not defined in this
   document for 911/112/999 style emergency calling, but it is not
   prevented either.

   Within the ESInet, there will be emergency calls requiring different
   treatments, according to the type of call.  Does a citizen's call to
   a PSAP require the same, a higher or a lower relative priority than a
   PSAP's call to a police department, or the police chief?  What about
   either relative to a call from within the ESInet to a national
   government's department responsible for public safety, disaster
   relief, national security/defense, etc.?  For these additional
   reasons, the 'esnet' namespace was given multiple priority levels.

   This document does not define any of these behaviors, outside of
   reminding readers that the rules of RFC 4412 apply - though examples
   of usage are included for completeness.  This document IANA registers
   the 'esnet' RPH namespace for use within any emergency services
   networks, not just of those from citizens to PSAPs.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2.  Rules of Usage of the Resource Priority Header field

   This document retains the behaviors of the SIP Resource Priority
   header field, defined in [RFC4412], during the treatment options
   surrounding this new 'esnet' namespace.  The usage of the 'esnet'
   namespace does not have a 'normal', or routine call level, given the
   environment this is to be used within (i.e., within an ESInet).  That
   is left for local jurisdictions to define within their respective
   parts of the ESInet, which could be islands of local administration.

Polk                     Expires August 26, 2013                [Page 4]

Internet-Draft           Emergency RPH Namespace           February 2013

   The 'esnet' namespace MUST only be used where at least one end of the
   signaling, setting aside the placement of B2BUAs, is within a local
   emergency organization.  In other words, if either the originating
   human caller's UA, or the destination human callee's UA is part of
   the local emergency organization, this is a valid use of 'esnet'.

   The 'esnet' namespace has 5 priority-values, in a specified relative
   priority order, and is registered as a queue-based namespace in
   compliance with [RFC4412].  SIP entities that support preemption
   treatment (see Section 5 of [RFC4412]) can be configured according to
   local policy.  Display names for the 'esnet' values displayed can
   likewise be set according to local policy.

   The following network diagram provides one example of local policy
   choices for the use of the 'esnet' namespace:

Polk                     Expires August 26, 2013                [Page 5]

Internet-Draft           Emergency RPH Namespace           February 2013

                                                 |<-'esnet' namespace->|
                                                 |        is used      |
   'esnet' namespace                             |        ,-------.
   usage out of scope                            |      ,'         `.
      |<------------>|<---'esnet' namespace ---->|     /             \
   +----+            |       can be used      +-----+ |    ESInet     |
   | UA |---         |    --------------------|Proxy|-+    ------     |
   +----+   \        |   /                    +-----+ |               |
             \  ,-------+           ,-------.    |    |   +------+    |
   +----+     ,'         `.       ,'         `.  |    |   |PSAP-1|    |
   | UA |--- /  User       \     / Application \ |    |   +------+    |
   +----+   (    Network    +---+    Service    )|    |               |
             \             /     \   Provider  / |    |   +------+    |
   +----+    /`.         ,'       `.         .+-----+ |   |PSAP-2|    |
   | UA |----   '-------'           '-------' |Proxy|-+   +------+    |
   +----+            |                        +-----+ |               |
                     |                           |    |               |
   +----+            |                        +-----+ |   +------+    |
   | UA |---         |    --------------------|Proxy|-+   |PSAP-3|    |
   +----+   \        |   /                    +-----+ |   +------+    |
             \  ,-------+           ,-------.    |    |               |
   +----+     ,'         `.       ,'         `.  |    |               |
   | UA |--- /  User       \     / Application \ |    |   +------+    |
   +----+   (    Network    +---+    Service    )|    |   |PSAP-4|    |
             \             /     \   Provider  / |    |   +------+    |
   +----+    /`.         ,'       `.         .+-----+ |               |
   | UA |----   '-------'           '-------' |Proxy|-+    ANY can    |
   +----+            |                        +-----+ |   xfer/call   |
                     |                           |     \    | | |    /
                                                        `.  | | |  ,'
                                                            | | |
                                     Police  <--------------+ | |
                                              Fire <----------+ |
                                        National Agency <-------+

          A possible network architecture using 'esnet' namespace

   In Figure 1., the 'esnet' namespace is used within the ESInet on the
   right side of the diagram.  How it is specifically utilized is out of
   scope for this document, and left to local jurisdictions to define.
   Whether preemption is implemented in the ESInet and the values
   displayed to the ESInet users, is likewise out of scope.  Adjacent
   ASPs to the ESInet may have a trust relationship that includes
   allowing this/these neighboring ASP(s) to use the 'esnet' namespace
   to differentiate SIP requests and dialogs within the ASP's network.
   The exact mapping between the internal and external sides of the edge
   proxy at the ESInet boundaries is out of scope of this document.

Polk                     Expires August 26, 2013                [Page 6]

Internet-Draft           Emergency RPH Namespace           February 2013

3.  "esnet" Namespace Definition

   The 'esnet' namespace is not generic for all emergencies because
   there are a lot of different kinds of emergencies, some on a military
   scale ([RFC4412] defines 3 of these), some on a national scale
   ([RFC4412] defines 2 of these), some on an international scale.  Each
   type of emergency can also have its own namespace(s), and although
   there are many defined for other uses, more are possible - so the
   911/112/999 style of public user emergency calling for police or fire
   or ambulance (etc) does not have a monopoly on the word "emergency".

   The namespace 'esnet' has been chosen, roughly to stand for
   "Emergency Services NETwork", for a citizen's call for help from a
   public authority type of organization.  This namespace will also be
   used for communications between emergency authorities, and MAY be
   used for emergency authorities calling public citizens.  An example
   of the latter is a PSAP operator calling back someone who previously
   called 911/112/999 and the communication was terminated before it -
   in the PSAP operator's judgment - should have been.

   Here is an example of a Resource-Priority header field using the
   'esnet' namespace:

         Resource-Priority: esnet.0

3.1.  Namespace Definition Rules and Guidelines

   This specification defines one unique namespace for emergency calling
   scenarios, 'esnet', constituting its registration with IANA.  This
   IANA registration contains the facets defined in Section 9 of

3.2.  The 'esnet' Namespace

   Per the rules of [RFC4412], each namespace has a finite set of
   relative priority-value(s), listed (below) from lowest priority to
   highest priority.  In an attempt to not limit this namespace's use in
   the future, more than one priority-value is assigned to the 'esnet'
   namespace.  This document does not recommend which Priority-value is
   used where in which situation or scenario.  That is for another
   document to specify.  To be effective, the choice within a national
   jurisdiction needs to be coordinated by all sub-jurisdictions to
   maintain uniform SIP behavior throughout an emergency calling system
   of that nation

   The relative priority order for the 'esnet' namespace is as follows:

Polk                     Expires August 26, 2013                [Page 7]

Internet-Draft           Emergency RPH Namespace           February 2013

         (lowest)  esnet.0
         (highest) esnet.4

   The 'esnet' namespace will have priority queuing registrations for
   these levels per Section 4.5.2 of [RFC4412].  Although no preemption
   is specified in this document for any levels of esnet, local
   jurisdiction(s) MAY configure their SIP infrastructure to use this
   namespace with preemption, as defined in RFC 4412.

   The remaining rules originated in RFC 4412 apply with regard to an RP
   actor who understands more than one namespace, and is must maintain
   its locally significant relative priority order.

4.  IANA Considerations

4.1.  IANA Resource-Priority Namespace Registration

   Within the "Resource-Priority Namespaces" of the sip-parameters
   section of IANA (created by [RFC4412]), the following entries will be
   added to this table:

                          Intended      New warn-   New resp.
     Namespace  Levels    Algorithm     code        code      Reference
     ---------  ------  --------------  ---------   --------- ---------
       esnet      5        queue           no          no     [This doc]

4.2.  IANA Priority-Value Registrations

   Within the Resource-Priority Priority-values registry of the sip-
   parameters section of IANA, the following (below) is to be added to
   the table:

      Namespace: esnet
      Reference: (this document)
      Priority-Values (least to greatest): "0", "1","2", "3", "4"

5.  Security Considerations

   The Security considerations that apply to RFC 4412 [RFC4412] apply

   For networks that act on the SIP Resource-Priority header field,

Polk                     Expires August 26, 2013                [Page 8]

Internet-Draft           Emergency RPH Namespace           February 2013

   incorrect use of namespaces can result in traffic that should have
   been given preferential treatment not be given it and vice versa.
   This document does not define a use case where an endpoint outside
   the ESInet marks its call for preferential treatment.  Protections
   need to be taken to prevent granting preferential treatment to
   unauthorized users not calling for emergency help even if they are in
   the ESInet, as well as to prevent misuse by callers outside the

   A simple means of preventing this usage is to not allow 'esnet'
   marked traffic to get preferential treatment unless the destination
   is towards the local/regional ESInet.  This is not a consideration
   for internetwork traffic within the ESInet, or generated out of the
   ESInet. 911/112/999 type of calling is fairly local in nature, with a
   finite number of URIs that are likely to be considered valid within a
   portion of a network receiving SIP signaling.

   This namespace is not intended for use on the Internet because of the
   difficulty in detecting abuse, specifically, it can trivially be
   forged and used on a non-emergency session to obtain resource
   priority.  Some networks may determine that it can reasonably prevent
   abuse and/or the consequences of undetected abuse is not significant.
   In such cases, use of esnet MAY be allowed.

6.  Acknowledgements

   Thanks to Ken Carlberg, Janet Gunn, Fred Baker and Keith Drage for
   help and encouragement with this effort.  Thanks to Henning
   Schulzrinne, Ted Hardie, Hannes Tschofenig, Janet Gunn and Marc
   Linsner for constructive comments.  A big thanks to Robert Sparks for
   being patient with the author and Brian Rosen for completing the
   final edits.

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource
              Priority for the Session Initiation Protocol (SIP)",
              RFC 4412, February 2006.

Polk                     Expires August 26, 2013                [Page 9]

Internet-Draft           Emergency RPH Namespace           February 2013

   [RFC5031]  H. Schulzrinne, "A Uniform Resource Name (URN) for
              Emergency and Other Well-Known Services", RFC 5031,
              January 2008

              Rosen, B., "Resource Priority Header (RPH) Registry
              Management Policy to IETF Review",
              draft-rosen-rph-reg-policy-00 (work in progress),
              February 2013.

Author's Address

   James Polk
   Cisco Systems
   3913 Treemont Circle
   Colleyville, TX  76034

   Phone: +1-817-271-3552
   Email: jmpolk@cisco.com

Polk                     Expires August 26, 2013               [Page 10]