ECRIT Working Group                                          James Polk
Internet-Draft                                            Cisco Systems
Expires: August 19, 2009                                   Feb 19, 2009
Intended Status: Standards Track (as PS)                   Oct 27, 2008
Expires: April 27, 2009
Updates: RFC4412 (if published as an RFC)

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

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   This document creates and IANA registers 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

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 . . . . . . . .  6  5
     3.2   The "esnet" Namespace . . . . . . . . . . . . . . . . . .  6  5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  7  6
     4.1   IANA Resource-Priority Namespace Registration . . . . . .  7  6
     4.2   IANA Priority-Value Registrations . . . . . . . . . . . .  7  6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  7  6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     7.1   Normative References  . . . . . . . . . . . . . . . . . .  7
     7.2   Informative References  . . . . . . . . . . . . . . . . .  8
       Author's Address  . . . . . . . . . . . . . . . . . . . . . .  8
       Intellectual Property and Copyright Statements  . . . . . . .  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) namespace "esnet" for
   local emergency usage.  The SIP Resource-Priority header is defined
   in RFC 4412 [RFC4412]. This new namespace can be from a caller in
   distress, or added at within the entry server into an emergency services
   managed network, towards a public safety
   answering point (PSAP),
   i.e., the 911 or 112-based emergency services call taker. (PSAP) network ("ESInet").  This new namespace can
   be used for inbound calls to PSAPs, between PSAPs, and between a
   PSAP and first responders and their organizations.

   Within controlled environments, such as an IMS infrastructure or
   Emergency Services network (ESINet), (ESInet), where misuse can be reduced to
   a minimum where possible, providing this namespace is to be to provide an
   explicit priority indication facilitates treatment of emergency SIP
   messages according to local policy.  This indication is used to
   differentiate SIP signaling requests, or dialogs, from other requests or dialogs.
   dialogs that do not have the need for priority treatment.

   It can also be imagined that Voice Service Providers (VSP) 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

   Usage of the "esnet" namespace is to be defined in a future
   document(s). 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.   [RFC4412] further states that modifying the
   order or the number of priority-values to a registered namespace
   SHOULD NOT occur, due to interoperability issues with dissimilar
   Implementations - perhaps separated by timing of each

   From this fact about RFC 4412, and the possibility that within
   emergency services networks, a Multilevel Precedence and Preemption
   (MLPP)-like behavior can be achieved - 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

   This document updates the behaviors of the SIP Resource Priority
   header, defined in [RFC4412], during the treatment options
   surrounding this new "esnet" namespace only. The usage of the
   "esnet" namespace does not have a normal, or routine call level.
   Every use of this namespace will be in times of an emergency, where
   at least one end of the signaling is with 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 is optional, and a local policy

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

                                                |<-"esnet" namespace->|
                                                |    *WILL* be used   |
  "esnet" namespace                             |        ,-------.
       can be used
  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*    ANY can    |
  +----+            |                        +-----+ |  xfer a call   xfer/call   |
                    |                           |     \    | | |    /
                                                       `.  | | |  ,'
                                                           | | |
                                    Police  <--------------+ | |
                                             Fire <----------+ |
                                        Federal Agency <-------+

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

   In Figure 1., UAs connect to service providers that can have SIP
   proxies.  When calling for emergency help, the UAs MAY include a "esnet" namespace in the SIP request.  Use of this new namespace is
   OPTIONAL, and likely is not trustworthy, unless SIP signaling is intended for usage within a managed environment starting at the originating UAC.  This
   namespace, therefore, MAY be overwritten or deleted, contrary to
   ESInet on the
   rules right side of RFC 4412 [RFC4412].  These proxies in the service provider
   MAY either

   o  accept the existing RPH value with "esnet" in it, if one diagram.  How it is
      present, and grant relative preferential treatment utilized is out
   of scope for this document.  Adjacent VSPs to the request
      when forwarding it ESInet MAY have a
   trust relationship that includes allowing this neighboring VSP to
   use the ESINet.

   o  replace any existing RPH value, if one is present, and insert an "esnet" namespace and give relative preferential treatment to the
      request when forwarding it to the ESINet.

   o  insert an "esnet" namespace in a new RPH and give relative
      preferential treatment to the request when forwarding the differentiate SIP
      request towards the ESINet.

   Adjacent service providers can have a trust relationship in regards
   to emergency calling, requests and dialogs
   within the receiving service provider can accept
   the inbound 'esnet' RPH VSP network.  How this namespace value and give preferential
   treatment to the request when forwarding it to the ESINet.

   On the other hand, SPs can choose to process each inbound SIP
   requests with its own policies, based on the type is utilized is out of request it is,
   in addition to
   scope for this document.  Because the nature more important usage of the request.  If the request is
   destined for a PSAP, according to
   "esnet" namespace occurs within the receiving SP, it MAY treat ESInet, the
   request as if it were coming directly from edge proxy, called
   an Emergency Services Routing Proxy (ESRP) can modify or delete this
   namespace. This is a UA, and act according normative change to the 3 bullets above.

   Ultimately, the edge proxy at the ESINet will receive emergency SIP
   request, and process the request according to its rules.  Regardless
   of what RPH indications there are allowed behavior within
   [RFC4412], but MUST only be considered valid in this usage at the message, and what
   treatments the message has received, the ESINet edge proxy will
   ensure there is an RPH with the "esnet"
   ESInet boundary for this one RP namespace in (and associated
   priority-value).  The exact mapping between the request.
   Local policy will dictate sides of the priority-value to be assigned within ESRP at
   the ESINet.  This document makes no recommendations. ESInet boundary are out of scope of this document.

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 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".


   Therefore, the namespace "esnet" has been chosen, as it is most
   recognizable as that of citizen calling 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 and the communication was terminated before it
   should have been (in the operator's judgment).

   Here is an example of a Resource-Priority header using the esnet

      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.  That is for another document to
   specify.  This document does RECOMMEND the choice within a national
   jurisdiction is be coordinated by all sub-jurisdictions to maintain
   uniform SIP behavior throughout an emergency calling system.

   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 can be used where the
   local jurisdiction preferred to preempt normal calls in lieu of
   completing emergency calls.  This document is not RECOMMENDING this
   usage, merely pointing out those behaviors is are a matter of local

   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
   here.  This document introduces no new security issues relative to
   RFC 4412.

   That said, since

   The implications of using this SIP header, used for emergency calling header-value incorrectly can
   have cause a great
   large impact on local communications, providers SHOULD use
   caution when deciding if they want to use a preemption algorithm network - given that this indication is to give
   preferential treatment of marked traffic great preference within the public space
   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 is to not allow marked
   traffic preferential treatment unless the destination is towards the
   local/regional ESInet.  911/112/999 type calling.  As
   potentially already limited communications bandwidth might starve
   out all other types of calls calling is fairly local
   in nature, with a location.  This decision might be
   desired; but this effect might not be desired. 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 and Marc
   Linsner for constructive comments.

7.  References

7.1  Normative References

 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
 [RFC4412] Schulzrinne, H., Polk, J., "Communications Resource
           Priority for the Session Initiation Protocol (SIP)", RFC

7.2  Informative References


Author's Address

   James Polk
   3913 Treemont Circle
   Colleyville, Texas  76034

   Phone: +1-817-271-3552

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