Internet DRAFT - draft-polk-local-emergency-rph-namespace
draft-polk-local-emergency-rph-namespace
Network Working Group J. Polk
Internet-Draft Cisco Systems
Intended status: Informational February 22, 2013
Expires: August 26, 2013
IANA 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' 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.
Status of this Memo
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This Internet-Draft will expire on August 26, 2013.
Copyright Notice
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Rules of Usage of the Resource Priority Header field . . . . . 4
3. "esnet" Namespace Definition . . . . . . . . . . . . . . . . . 7
3.1. Namespace Definition Rules and Guidelines . . . . . . . . 7
3.2. The 'esnet' Namespace . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. IANA Resource-Priority Namespace Registration . . . . . . 8
4.2. IANA Priority-Value Registrations . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document creates the new Session Initiation Protocol (SIP)
Resource Priority header (RPH) 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].
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 RPH with the 'esnet' namespace can be differentiated from
the marking of an emergency call using a service urn as defined in
RFC 5031 in that the RPH specifically requests preferential treatment
in networks which 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
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 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).
Application Service Providers (ASP) 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 ("call back") when priority is needed. Again, the
request for priority is not for use on the public Internet due to the
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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 new RPH namespaces and their
relative priority-value order.
There is the possibility that within emergency services networks a
Multilevel Precedence and Preemption (MLPP)-like behavior can be
achieved (likely without the 'preemption' part), provided 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 the 'esnet' namespace is given five priority-levels
instead of just one. 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 national
government's department responsible for public safety, disaster
relief, national security/defense, etc.? For these additional
reasons, the 'esnet' namespace was 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.
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 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 left for local jurisdictions to define within their respective
parts of the ESInet, which could be islands of local administration.
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The 'esnet' namespace MUST only be used where at least one end of the
signaling, setting aside the placement of B2BUAs, is within a local
emergency organization. In other words, if either the originating
human caller's 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 the 'esnet' namespace:
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|<-'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 'esnet' namespace
In Figure 1., 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, and left to local jurisdictions to define.
Whether preemption is implemented in the ESInet and the values
displayed to the ESInet 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 scope of this document.
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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), some on an international scale. Each
type of emergency can also have its own namespace(s), and although
there are many 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 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
The relative priority order for the 'esnet' namespace is as follows:
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(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, local
jurisdiction(s) MAY configure their SIP infrastructure to use this
namespace with preemption, as defined in RFC 4412.
The remaining rules 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 "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.
For networks that act on the SIP Resource-Priority header field,
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incorrect use of namespaces can result in traffic that should have
been given preferential treatment not be given 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
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 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 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, 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 the consequences of undetected abuse is not significant.
In such cases, use of esnet MAY be allowed.
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, 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.
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[RFC5031] H. Schulzrinne, "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
January 2008
[I-D.rosen-rph-reg-policy]
Rosen, B., "Resource Priority Header (RPH) Registry
Management Policy to IETF Review",
draft-rosen-rph-reg-policy-00 (work in progress),
February 2013.
Author's Address
James Polk
Cisco Systems
3913 Treemont Circle
Colleyville, TX 76034
USA
Phone: +1-817-271-3552
Email: jmpolk@cisco.com
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