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Versions: 00 01 02 03 04 05 RFC 7135

Network Working Group                                        James Polk
Internet-Draft                                            Cisco Systems
Expires: December 6, 2011                                  June 6, 2011
Intended Status: Standards Track

          IANA Registering a SIP Resource Priority Header Field
              Namespace for Local Emergency Communications
               draft-polk-local-emergency-rph-namespace-01

Abstract

   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header field namespace "esnet" for local emergency
   usage 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

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Table of Contents

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



   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].


1.  Introduction

   This document creates the new Session Initiation Protocol (SIP)
   Resource Priority header 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].
   This new namespace can be used for inbound calls towards a public
   safety answering point (PSAP), between PSAPs, and between a PSAP and
   first responders or their organizations.

   This new namespace can be 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 a minimum because these types of networks
   have great controls in place.  The function is to facilitate
   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 another).

   It can also be imagined that Application Service Providers (ASP)


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   directly attached to an ESInet can have a trust relationship with
   the ESInet such that within these networks, SIP requests (thereby
   the session they establish) make use of this "esnet" namespace for
   appropriate treatment.

   This document merely creates the namespace, per the rules within
   [RFC4412], necessitating a Standards Track RFC for IANA registering
   new RPH namespaces and their relative priority-value order.

   There is the possibility that within emergency services networks,
   provided local policy supports enabling this function, a Multilevel
   Precedence and Preemption (MLPP)-like behavior can be achieved
   (likely without the 'preemption' part). This will ensure more the
   important calls are established or retained; therefore the "esnet"
   namespace is given 5 priority-levels.  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
   federal government's department of national security, such as the US
   Department of Homeland Security?  For this reason, the "esnet"
   namespace is 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.


2.  Rules of Usage of the Resource Priority Header field

   This document retains the behaviours 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 for local jurisdictions to define within their respective
   parts of the ESInet- which could be islands of local administration.

   RFC 4412 states that modifying the relative priority ordering or the
   number of priority-values to a registered namespace SHOULD NOT occur
   within the same administrative domain due to interoperability issues
   with dissimilar implementations.

   The "esnet" namespace SHOULD only be used in times of an emergency,
   where at least one end of the signaling is within a local emergency
   organization.


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   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]. Individual jurisdictions MAY configure
   their SIP entities for preemption treatment. This is OPTIONAL,
   subject to local policy decisions.

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

                                                |<-"esnet" namespace->|
                                                |    *WILL* be 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 <----------+ |
                                   to a Federal Agency <-------+

   Figure 1: A possible network architecture using "esnet" namespace

   In Figure 1., the "esnet" namespace is intended for usage 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.  Adjacent ASPs to the ESInet MAY have a


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   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.


3.  "esnet" Namespace Definition

   The "esnet" namespace should not to be considered 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 45 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
   [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.  That is for another document to
   specify.  This document does RECOMMEND the choice within a national
   jurisdiction be coordinated by all sub-jurisdictions to maintain
   uniform SIP behavior throughout an emergency calling system of that
   country.



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   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 be designated into the priority queuing
   algorithm (Section 4.5.2 of [RFC4412]).  However, as a policy
   decision, local jurisdiction(s) MAY configure their SIP
   infrastructure to use the this namespace in a preemption algorithm
   way, defined in RFC 4412. This document does not recommend this
   usage, but it is permissible according to this specification.

   The remaining rules originated in RFC 4412 apply with regard to an
   RP actor, who understands more than one namespace, and 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
   here.

   Within a network that is enabled to act on the Resource-Priority
   header field within SIP requests, the implications of using this


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   namespace within the field incorrectly can potentially cause a large
   impact on a network, given that this indication is to give
   preferential treatment of marked traffic great preference within the
   network verses other traffic.  This document does not indicate this
   marking is intended for use by endpoints, yet protections need to be
   taken to prevent granting preferential treatment to unauthorized
   users not calling for emergency help.

   A simple means of preventing this usage into an ESInet 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 considered
   valid.


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, Brian Rosen, Janet Gunn
   and Marc Linsner for constructive comments.


7.  References

7.1  Normative References

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

 [RFC4412] Schulzrinne, H., Polk, J., "Communications Resource
           Priority for the Session Initiation Protocol (SIP)", RFC
           4411, Feb 2006

7.2  Informative References

   none



Author's Address

   James Polk
   3913 Treemont Circle
   Colleyville, Texas  76034
   USA
   Phone: +1-817-271-3552
   Email: jmpolk@cisco.com




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