ECRIT Working Group                                          James Polk
Internet-Draft                                            Cisco Systems
Expires: September 24, 2009                                Mar 24, 2009 7, 2010                                March 7, 2010
Intended Status: Standards Track (as PS)

          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
   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.

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   This document creates and IANA registers without
   warranty as described in the new Session Initiation
   Protocol (SIP) Resource Priority header (RPH) 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. BSD License.

Table of Contents

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

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

1.  Introduction

   This document creates and IANA registers the new Session Initiation Protocol (SIP)
   Resource Priority header (RPH) field namespace "esnet" for local emergency usage.
   usage and places this namespace in the IANA registry.  The SIP
   Resource-Priority header field is defined in RFC 4412 [RFC4412].
   This new namespace is to be used within public safety answering
   point  (PSAP) networks.  This new namespace can be used for inbound
   calls towards PSAPs, between PSAPs, and between a PSAP and first
   responders or their organizations.

   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, this namespace can be to provide an explicit priority
   indication that facilitates differing treatment of emergency SIP
   messages according to local policy, or more likely, a contractual
   agreement between the network organizations.  This indication is
   used solely to differentiate SIP requests, transactions or dialogs,
   from other requests requests, transactions or dialogs that do not have the
   need for priority treatment.  If there are differing, yet still
   valid Resource-Priority header values between SIP requests in a
   network, 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 Voice Application Service Providers (VSP) (ASP)
   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.

   Usage of the "esnet" namespace is to be defined in a future

   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 a the possibility that within emergency services networks, networks -
   provided local policy supports enabling this function - a Multilevel
   Precedence and Preemption (MLPP)-like behavior can be achieved
   (likely without the 'preemption' part, which will always be a matter
   of local policy, and not defined here) - ensuring more important calls
   are established or retained, 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 emergency
   services networks, not just of those from citizens to PSAPs.

2.  Rules of Usage of the Resource Priority Header field

   This document updates retains the behaviors of the SIP Resource Priority
   header field, defined in [RFC4412], during the treatment options
   surrounding this new "esnet" namespace only. 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 is not
   recommended across the same administrative domain, due to
   interoperability issues with dissimilar implementations.

   Every use of this namespace will be in times of an emergency, where
   at least one end of the signaling is within a local emergency

   The "esnet" namespace has 5 priority-values, in a specified relative
   priority order, and is a queue-based treatment namespace [RFC4412].
   Individual jurisdictions MAY configure their SIP entities for
   preemption treatment, but this treatment. This is optional, and a OPTIONAL, subject to local policy

   Conceivably, this could be an example network diagram where the
   "esnet" namespace is used:

                                                |<-"esnet" namespace->|
                                                |    *WILL* be used   |
  "esnet" namespace                             |        ,-------.
  usage out of scope                            |      ,'         `.
     |<------------>|<---"esnet" namespace ---->|     /             \
  +----+            |       can be used      +-----+ |    ESINet     |
  | UA |---         |    --------------------|Proxy|-+    ------     |
  +----+   \        |   /                    +-----+ |               |
            \  ,-------+           ,-------.    |    |   +------+    |
  +----+     ,'         `.       ,'         `.  |    |   |PSAP-1|    |
  | UA |--- /  User       \     /   Service   \ |    |   +------+    |
  +----+   (    Network    +---+    Network    )|    |               |
            \             /     \             / |    |   +------+    |
  +----+    /`.         ,'       `.         .+-----+ |   |PSAP-2|    |
  | UA |----   '-------'           '-------' |Proxy|-+   +------+    |
  +----+            |                        +-----+ |               |
                    |                           |    |               |
  +----+            |                        +-----+ |   +------+    |
  | UA |---         |    --------------------|Proxy|-+   |PSAP-3|    |
  +----+   \        |   /                    +-----+ |   +------+    |
            \  ,-------+           ,-------.    |    |               |
  +----+     ,'         `.       ,'         `.  |    |               |
  | UA |--- /  User       \     /   Service   \ |    |   +------+    |
  +----+   (    Network    +---+    Network    )|    |   |PSAP-4|    |
            \             /     \             / |    |   +------+    |
  +----+    /`.         ,'       `.         .+-----+ |               |
  | UA |----   '-------'           '-------' |Proxy|-+    ANY can    |
  +----+            |                        +-----+ |   xfer/call   |
                    |                           |     \    | | |    /
                                                       `.  | | |  ,'
                                                           | | |
                                    Police  <--------------+ | |
                                             Fire <----------+ |
                                   to a Federal Agency <-------+

       Figure 1: Where 'esnet' Namespace Can or Will be used

   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 VSPs 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 VSP's 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.

   To be clear, specifically for the use of an edge proxy in any
   network, the rules
   within the document that create a (i.e., each) namespace apply, and because the "esnet" namespace is allowed to be modified or
   deleted at the edge proxy of the ESInet does not allow any edge
   proxy to modify or delete any other Resource-Priority namespace.
   This document's target market is for the "esnet" namespace only.

3.  "esnet" Namespace Definition

   One thing to keep in mind for now is the fact that this namespace
   is not to be considered just "EMERGENCY" 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.  These types of
   emergencies can also have their own namespaces, and although there
   are 5 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

   Therefore, the

   The namespace "esnet" has been chosen, chosen - roughly to stand for
   "Emergency Services NETwork", as it is most recognizable as that of
   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 later is a
   PSAP operator calling back someone who previously called 9111/112/999 911/112/999
   and the communication was terminated before it
   should have been (in - in the PSAP
   operator's judgment). judgment - should have been.

   Here is an example of a Resource-Priority header field using the esnet
   "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 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 is coordinated by all sub-jurisdictions to maintain
   uniform SIP behavior throughout an emergency calling system. system of that

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

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

   The "esnet" namespace will be assigned into the priority queuing
   algorithm (Section 4.5.2 of [RFC4412]) from the public user to the
   PSAP.  This does not limit its usage to only the priority queue
   algorithm; meaning the preemption algorithm is a policy decision for
   local jurisdictions.  This document is not RECOMMENDING this
   usage, merely pointing out those behaviors is a matter of local

   The rules originated in RFC 4412 remain with regard to an RP actor,
   who understands more than one namespace, MUST maintain its locally
   significant relative priority order.

   NOTE: at this time, there has not been sufficient discussion about
   whether or not preemption will be used for communications between
   PSAPs or between PSAPs and First responders (and their

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

   The implications of using this header-value namespace within the
   Resource-Priority header field incorrectly can cause a large impact
   on a network - given that this indication is to give preferential
   treatment of marked traffic great preference within the network than
   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

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


Author's Address

   James Polk
   3913 Treemont Circle
   Colleyville, Texas  76034
   Phone: +1-817-271-3552