ECRIT Working Group James Polk
Internet-Draft Cisco Systems
Expires: September 7, 2010 March 7, 2010
Intended Status: Standards Track
IANA Registering a SIP Resource Priority Header Field
Namespace for Local Emergency Communications
draft-ietf-ecrit-local-emergency-rph-namespace-04
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 . . . . . . . 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
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 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, 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 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, which will always be a matter
of local policy, and 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 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 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
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organization.
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. This is OPTIONAL, subject to local policy
decisions.
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
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jurisdictions to define. 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.
To be clear, specifically for the use of an edge proxy in any
network, 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 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", 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 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
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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 coordinated by all sub-jurisdictions to maintain
uniform SIP behavior throughout an emergency calling system of that
country.
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 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
policy.
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.
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
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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.
The implications of using this 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
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
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Author's Address
James Polk
3913 Treemont Circle
Colleyville, Texas 76034
USA
Phone: +1-817-271-3552
Email: jmpolk@cisco.com
Polk Expires Sept 7, 2010 [Page 8]
