Network Working Group
Internet Engineering Task Force (IETF)                           J. Polk
Internet-Draft
Request for Comments: 7135                                 Cisco Systems
Intended status:
Category: Informational                         February 22, 2013
Expires: August 26, 2013

  IANA                                         May 2014
ISSN: 2070-1721

     Registering a SIP Resource Priority Header Field Namespace for
                     Local Emergency Communications
            draft-polk-local-emergency-rph-namespace-05.txt

Abstract

   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header field namespace 'esnet' and registers this
   namespace with IANA.  The new header field namespace allows 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. organizations.

Status of this This Memo

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   This Internet-Draft will expire on August 26, 2013.
   http://www.rfc-editor.org/info/rfc7135.

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Table of Contents

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

1.  Introduction

   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header (RPH) field namespace 'esnet' for local
   emergency usage and places registers this namespace in the IANA registry. with IANA.  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 an RPH with the 'esnet' namespace can be differentiated from
   the marking of an emergency call using a service urn URN as defined in
   RFC 5031
   [RFC5031] in that the RPH specifically requests preferential
   treatment in networks which that 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
   5031.

   This new namespace is included in SIP requests to provide an explicit
   priority indication within controlled environments, such as an IMS IP
   Multimedia Subsystem (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 transactions, or dialogs, dialogs from
   other SIP requests, transactions 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 transaction, or dialog receives which
   treatment (likely better or worse than another).

   Application Service Providers (ASP) (ASPs) that are 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 User Agent ("call back") when priority is needed.
   Again, the request for priority is not for use on the public Internet
   due to the 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 [RFC7134], which necessitates that new RPH
   namespaces and their relative priority-value order. order be IETF reviewed
   before being registered with IANA.

   There is the possibility that within emergency services networks a networks,
   Multilevel Precedence and Preemption (MLPP)-like behavior can be
   achieved (likely without the 'preemption' part), provided the 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  Therefore, the 'esnet' namespace is given five priority-levels
   instead of just one.  This document does not define MLPP-like SIP
   signaling is not defined in this
   document for 911/112/999 style emergency calling, calls like those using 911/112/999, 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 higher, or a lower relative priority than
   a PSAP's call to a police department, 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 has 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 with IANA 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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   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 when choosing between the
   treatment options surrounding this new 'esnet' namespace.  The  Given the
   environment this is to be used within (i.e., within an ESInet), the
   usage of the 'esnet' namespace does not have a 'normal', 'normal' or routine
   call level, given the
   environment this is to be used within (i.e., within an ESInet).  That level; that is left for local jurisdictions to define within
   their respective parts of the ESInet, which could be islands of local
   administration.

   The 'esnet' namespace MUST only be used where at least one end of the
   signaling, setting aside the placement of B2BUAs, B2BUAs (Back-to-Back User
   Agents), is within a local emergency organization.  In other words,
   if either the originating human caller's UA, User Agent (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 when using the 'esnet' namespace:

                                                 |<-'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 Possible Network Architecture Using the 'esnet' namespace Namespace

   In Figure 1., the figure, 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, document and is left to local jurisdictions to define.
   Whether preemption is implemented in the ESInet and the values
   displayed to the ESInet users, 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 the scope of this document.

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), and some on an international scale.
   Each type of emergency can also have its own namespace(s), and namespace(s); although
   there are many defined for other uses, more are possible - -- so the
   911/112/999 style
   911-/112-/999-style of public user emergency calling for police
   officers, firefighters, or fire
   or ambulance (etc) emergency medical technicians (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 it MAY be
   used for by emergency authorities calling to call 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

   Below 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 'esnet' and registers this namespace with IANA.  This IANA
   registration contains the facets defined in Section 9 of [RFC4412].

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 nation.

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

         (lowest)  esnet.0
                   esnet.1
                   esnet.2
                   esnet.3
         (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, 'esnet', local
   jurisdiction(s) MAY configure their SIP infrastructure to use this
   namespace with preemption, as defined in RFC 4412.

   The remaining rules that 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 following entry has been added to the "Resource-Priority
   Namespaces" registry of the sip-parameters section of IANA (created
   by [RFC4412]), the following entries will be
   added to this table: [RFC4412]):

                                       Intended       New warn-     New resp.
      Namespace  Levels   Algorithm     code        code     Code      warn-code   Reference
      ---------  ------  --------------  -----------  ---------   ---------   ---------
        esnet      5       queue         no          no     [This doc]       RFC 7135

4.2.  IANA Priority-Value Registrations

   Within

   The following entry has been added to the Resource-Priority Priority-values "Resource-Priority
   Priority-values" registry of the sip-
   parameters sip-parameters section of IANA, the following (below) is to be added to
   the table: IANA:

      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
   here.

   For networks that act on the SIP Resource-Priority header field,
   incorrect use of namespaces can result in traffic that should have
   been given preferential treatment not be given it receiving 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  Precautions
   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
   ESInet.

   A simple means of preventing this usage is to not allow 'esnet'
   marked traffic
   marked 'esnet' 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  911-/112-/999-type 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, 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 that the consequences of undetected abuse is not
   significant.  In such cases, use of esnet 'esnet' on the Internet MAY be
   allowed.

6.  Acknowledgements

   Thanks to Ken Carlberg, Janet Gunn, Fred Baker 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.

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

   [I-D.rosen-rph-reg-policy] 2008.

   [RFC7134]  Rosen, B., "Resource "The Management Policy of the Resource Priority
              Header (RPH) Registry
              Management Policy Changed to IETF Review",
              draft-rosen-rph-reg-policy-00 (work in progress),
              February 2013. "IETF Review"", RFC 7134,
              March 2014.

Author's Address

   James Polk
   Cisco Systems
   3913 Treemont Circle
   Colleyville, TX  76034
   USA

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