< draft-polk-local-emergency-rph-namespace-04.txt   draft-polk-local-emergency-rph-namespace-05.txt >
Network Working Group James Polk Network Working Group J. Polk
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Expires: August 15, 2013 February 15,2013 Intended status: Informational February 22, 2013
Intended Status: Informational Expires: August 26, 2013
IANA Registering a SIP Resource Priority Header Field IANA Registering a SIP Resource Priority Header Field Namespace for
Namespace for Local Emergency Communications Local Emergency Communications
draft-polk-local-emergency-rph-namespace-04 draft-polk-local-emergency-rph-namespace-05.txt
Abstract Abstract
This document creates the new Session Initiation Protocol (SIP) This document creates the new Session Initiation Protocol (SIP)
Resource Priority header field namespace "esnet" for local emergency Resource Priority header field namespace 'esnet' for local emergency
usage in the following cases: to a public safety answering point session establishment to a public safety answering point (PSAP),
(PSAP), between PSAPs, and between a PSAP and first responders and between PSAPs, and between a PSAP and first responders and their
their organizations. The document also puts this namespace into the organizations, and places this namespace in the IANA registry.
IANA registry.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 15, 2013. This Internet-Draft will expire on August 26, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Rules of Usage of the Resource Priority Header . . . . . . . 3 2. Rules of Usage of the Resource Priority Header field . . . . . 4
3. "esnet" Namespace Definition . . . . . . . . . . . . . . . . 5 3. "esnet" Namespace Definition . . . . . . . . . . . . . . . . . 7
3.1 Namespace Definition Rules and Guidelines . . . . . . . . 5 3.1. Namespace Definition Rules and Guidelines . . . . . . . . 7
3.2 The "esnet" Namespace . . . . . . . . . . . . . . . . . . 5 3.2. The 'esnet' Namespace . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1 IANA Resource-Priority Namespace Registration . . . . . . 6 4.1. IANA Resource-Priority Namespace Registration . . . . . . 8
4.2 IANA Priority-Value Registrations . . . . . . . . . . . . 6 4.2. IANA Priority-Value Registrations . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Normative References . . . . . . . . . . . . . . . . . . . . . 9
7.1 Normative References . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.2 Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
This document creates the new Session Initiation Protocol (SIP) This document creates the new Session Initiation Protocol (SIP)
Resource Priority header (RPH) field namespace "esnet" for local Resource Priority header (RPH) field namespace 'esnet' for local
emergency usage and places this namespace in the IANA registry. The emergency usage and places this namespace in the IANA registry. The
SIP Resource-Priority header field is defined in RFC 4412 SIP Resource-Priority header field is defined in RFC 4412 [RFC4412].
[RFC4412]. The new "esnet" namespace is to be used for inbound calls The new 'esnet' namespace is to be used for inbound calls towards a
towards a public safety answering point (PSAP), between PSAPs, and public safety answering point (PSAP), between PSAPs, and between a
between a PSAP and first responders or their organizations within PSAP and first responders or their organizations within managed IP
managed IP networks. This namespace is not for use on the open networks. This namespace is not for use on the open public Internet
public Internet because it can be trivially forged. because it can be trivially forged.
Adding a RPH with the "esnet" namespace can be differentiated from Adding a RPH with the 'esnet' namespace can be differentiated from
the marking of an emergency call using a service urn as defined in the marking of an emergency call using a service urn as defined in
RFC 5031 in that the RPH specifically requests preferential RFC 5031 in that the RPH specifically requests preferential treatment
treatment in networks which honor it, while the marking merely in networks which honor it, while the marking merely identifies an
identifies an emergency call without necessarily affecting resources emergency call without necessarily affecting resources allocated to
allocated to it. It is appropriate to use both where applicable. it. It is appropriate to use both where applicable. RPH with
RPH with "esnet" may also be used within public safety networks for 'esnet' may also be used within public safety networks for SIP
SIP sessions that are not emergency calls and thus not marked per sessions that are not emergency calls and thus not marked per RFC
RFC 5031. 5031.
This new namespace is included in SIP requests to provide an This new namespace is included in SIP requests to provide an explicit
explicit priority indication within controlled environments, such as priority indication within controlled environments, such as an IMS
an IMS infrastructure or Emergency Services network (ESInet) where infrastructure or Emergency Services network (ESInet) where misuse
misuse can be reduced to an acceptable level because these types of can be reduced to an acceptable level because these types of networks
networks have controls in place. The function facilitates differing have controls in place. The function facilitates differing treatment
treatment of emergency SIP requests according to local policy, or of emergency SIP requests according to local policy, or more likely,
more likely, a contractual agreement between the network a contractual agreement between the network organizations. This
organizations. This indication is used solely to differentiate indication is used solely to differentiate certain SIP requests,
certain SIP requests, transactions or dialogs, from other SIP transactions or dialogs, from other SIP requests, transactions or
requests, transactions or dialogs that do not have the need for dialogs that do not have the need for priority treatment. If there
priority treatment. If there are differing, yet still are differing, yet still understandable and valid Resource-Priority
understandable and valid Resource-Priority header values in separate header values in separate SIP requests, then this indication can be
SIP requests, then this indication can be used by local policy to used by local policy to determine which SIP request, transaction or
determine which SIP request, transaction or dialog receives which dialog receives which treatment (likely better or worse than
treatment (likely better or worse than another). another).
Application Service Providers (ASP) and ESInets that interact need Application Service Providers (ASP) securely connected to an ESInet
to specifically trust one another to correctly use this header. 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 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 public safety agency on an ESInet towards a private or public
network, ASP or UA ("call back") when priority is needed. Again, network, ASP or UA ("call back") when priority is needed. Again, the
the request for priority is not for use on the public Internet due request for priority is not for use on the public Internet due to the
to the ease of forging the header. ease of forging the header.
This document merely creates the namespace, per the rules within This document merely creates the namespace, per the rules within
[RFC4412] as updated by [draft-rosen-rph-reg-policy], necessitating [RFC4412] as updated by [I-D.rosen-rph-reg-policy], necessitating
IETF review for IANA registering new RPH namespaces and their IETF review for IANA registering new RPH namespaces and their
relative priority-value order. relative priority-value order.
There is the possibility that within emergency services networks a There is the possibility that within emergency services networks a
Multilevel Precedence and Preemption (MLPP)-like behavior can be Multilevel Precedence and Preemption (MLPP)-like behavior can be
achieved (likely without the 'preemption' part), provided local achieved (likely without the 'preemption' part), provided local
policy supports enabling this function. For example, calls placed policy supports enabling this function. For example, calls placed
between law enforcement agents could be marked similarly to MLPP between law enforcement agents could be marked similarly to MLPP
systems used by military networks, and some of those calls could be systems used by military networks, and some of those calls could be
handled with higher priority than an emergency call from an ordinary handled with higher priority than an emergency call from an ordinary
user. Therefore the "esnet" namespace is given five priority-levels user. Therefore the 'esnet' namespace is given five priority-levels
instead of just one. MLPP-like SIP signaling is not defined in this 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 document for 911/112/999 style emergency calling, but it is not
prevented either. prevented either.
Within the ESInet, there will be emergency calls requiring different Within the ESInet, there will be emergency calls requiring different
treatments, according to the type of call. Does a citizen's call to 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 require the same, a higher or a lower relative priority than a
a PSAP's call to a police department, or the police chief? What PSAP's call to a police department, or the police chief? What about
about either relative to a call from within the ESInet to a national either relative to a call from within the ESInet to a national
government's department responsible for public safety, disaster government's department responsible for public safety, disaster
relief, national security/defense, etc.? For these additional relief, national security/defense, etc.? For these additional
reasons, the "esnet" namespace was given multiple priority levels. reasons, the 'esnet' namespace was given multiple priority levels.
This document does not define any of these behaviors, outside of This document does not define any of these behaviors, outside of
reminding readers that the rules of RFC 4412 apply - though examples reminding readers that the rules of RFC 4412 apply - though examples
of usage are included for completeness. This document IANA of usage are included for completeness. This document IANA registers
registers the "esnet" RPH namespace for use within any emergency the 'esnet' RPH namespace for use within any emergency services
services networks, not just of those from citizens to PSAPs. networks, not just of those from citizens to PSAPs.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
"OPTIONAL" in this document are to be interpreted as described document are to be interpreted as described in [RFC2119].
in [RFC2119].
2. Rules of Usage of the Resource Priority Header field 2. Rules of Usage of the Resource Priority Header field
This document retains the behaviors of the SIP Resource Priority This document retains the behaviors of the SIP Resource Priority
header field, defined in [RFC4412], during the treatment options header field, defined in [RFC4412], during the treatment options
surrounding this new "esnet" namespace. The usage of the "esnet" surrounding this new 'esnet' namespace. The usage of the 'esnet'
namespace does not have a 'normal', or routine call level, given the namespace does not have a 'normal', or routine call level, given the
environment this is to be used within (i.e., within an ESInet). environment this is to be used within (i.e., within an ESInet). That
That is left for local jurisdictions to define within their is left for local jurisdictions to define within their respective
respective parts of the ESInet, which could be islands of local parts of the ESInet, which could be islands of local administration.
administration.
The "esnet" namespace MUST only be used where at least one end of The 'esnet' namespace MUST only be used where at least one end of the
the signaling, setting aside the placement of B2BUAs, is within a signaling, setting aside the placement of B2BUAs, is within a local
local emergency organization. In other words, if either the emergency organization. In other words, if either the originating
originating human caller's UA, or the destination human callee's UA human caller's UA, or the destination human callee's UA is part of
is part of the local emergency organization, this is a valid use of the local emergency organization, this is a valid use of 'esnet'.
"esnet".
The "esnet" namespace has 5 priority-values, in a specified relative The 'esnet' namespace has 5 priority-values, in a specified relative
priority order, and is registered as a queue-based namespace in priority order, and is registered as a queue-based namespace in
compliance with [RFC4412]. SIP entities that support preemption compliance with [RFC4412]. SIP entities that support preemption
treatment (see Section 5 of [RFC4412]) can be configured according treatment (see Section 5 of [RFC4412]) can be configured according to
to local policy. Display names for the "esnet" values displayed can local policy. Display names for the 'esnet' values displayed can
likewise be set according to local policy. likewise be set according to local policy.
The following network diagram provides one example of local policy The following network diagram provides one example of local policy
choices for the use of the "esnet" namespace: choices for the use of the 'esnet' namespace:
|<-"esnet" namespace->| |<-'esnet' namespace->|
| is used | | is used |
"esnet" namespace | ,-------. 'esnet' namespace | ,-------.
usage out of scope | ,' `. usage out of scope | ,' `.
|<------------>|<---"esnet" namespace ---->| / \ |<------------>|<---'esnet' namespace ---->| / \
+----+ | can be used +-----+ | ESInet | +----+ | can be used +-----+ | ESInet |
| UA |--- | --------------------|Proxy|-+ ------ | | UA |--- | --------------------|Proxy|-+ ------ |
+----+ \ | / +-----+ | | +----+ \ | / +-----+ | |
\ ,-------+ ,-------. | | +------+ | \ ,-------+ ,-------. | | +------+ |
+----+ ,' `. ,' `. | | |PSAP-1| | +----+ ,' `. ,' `. | | |PSAP-1| |
| UA |--- / User \ / Application \ | | +------+ | | UA |--- / User \ / Application \ | | +------+ |
+----+ ( Network +---+ Service )| | | +----+ ( Network +---+ Service )| | |
\ / \ Provider / | | +------+ | \ / \ Provider / | | +------+ |
+----+ /`. ,' `. .+-----+ | |PSAP-2| | +----+ /`. ,' `. .+-----+ | |PSAP-2| |
| UA |---- '-------' '-------' |Proxy|-+ +------+ | | UA |---- '-------' '-------' |Proxy|-+ +------+ |
+----+ | +-----+ | | +----+ | +-----+ | |
| | | | | | | |
+----+ | +-----+ | +------+ | +----+ | +-----+ | +------+ |
| UA |--- | --------------------|Proxy|-+ |PSAP-3| | | UA |--- | --------------------|Proxy|-+ |PSAP-3| |
+----+ \ | / +-----+ | +------+ | +----+ \ | / +-----+ | +------+ |
\ ,-------+ ,-------. | | | \ ,-------+ ,-------. | | |
+----+ ,' `. ,' `. | | | +----+ ,' `. ,' `. | | |
| UA |--- / User \ / Application \ | | +------+ | | UA |--- / User \ / Application \ | | +------+ |
+----+ ( Network +---+ Service )| | |PSAP-4| | +----+ ( Network +---+ Service )| | |PSAP-4| |
\ / \ Provider / | | +------+ | \ / \ Provider / | | +------+ |
+----+ /`. ,' `. .+-----+ | | +----+ /`. ,' `. .+-----+ | |
| UA |---- '-------' '-------' |Proxy|-+ ANY can | | UA |---- '-------' '-------' |Proxy|-+ ANY can |
+----+ | +-----+ | xfer/call | +----+ | +-----+ | xfer/call |
| | \ | | | / | | \ | | | /
`. | | | ,' `. | | | ,'
'-|-|-|-' '-|-|-|-'
| | | | | |
Police <--------------+ | | Police <--------------+ | |
Fire <----------+ | Fire <----------+ |
National Agency <-------+ National Agency <-------+
Figure 1: A possible network architecture using "esnet" namespace A possible network architecture using 'esnet' namespace
In Figure 1., the "esnet" namespace is used within the ESInet on the 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 right side of the diagram. How it is specifically utilized is out of
of scope for this document, and left to local jurisdictions to scope for this document, and left to local jurisdictions to define.
define. Whether preemption is implemented in the ESInet and the Whether preemption is implemented in the ESInet and the values
values displayed to the ESInet users, is likewise out of scope. displayed to the ESInet users, is likewise out of scope. Adjacent
Adjacent ASPs to the ESInet may have a trust relationship that ASPs to the ESInet may have a trust relationship that includes
includes allowing this/these neighboring ASP(s) to use the "esnet" allowing this/these neighboring ASP(s) to use the 'esnet' namespace
namespace to differentiate SIP requests and dialogs within the ASP's to differentiate SIP requests and dialogs within the ASP's network.
network. The exact mapping between the internal and external sides The exact mapping between the internal and external sides of the edge
of the edge proxy at the ESInet boundaries is out of scope of this proxy at the ESInet boundaries is out of scope of this document.
document.
3. "esnet" Namespace Definition 3. "esnet" Namespace Definition
The "esnet" namespace is not generic for all emergencies because The 'esnet' namespace is not generic for all emergencies because
there are a lot of different kinds of emergencies, some on a there are a lot of different kinds of emergencies, some on a military
military scale ([RFC4412] defines 3 of these), some on a national scale ([RFC4412] defines 3 of these), some on a national scale
scale ([RFC4412] defines 2 of these), some on an international ([RFC4412] defines 2 of these), some on an international scale. Each
scale. Each type of emergency can also have its own namespace(s), type of emergency can also have its own namespace(s), and although
and although there are 45 defined for other uses (5 in [RFC4412] and there are many defined for other uses, more are possible - so the
40 in [RFC5478]), more are possible - so the 911/112/999 style of 911/112/999 style of public user emergency calling for police or fire
public user emergency calling for police or fire or ambulance (etc) or ambulance (etc) does not have a monopoly on the word "emergency".
does not have a monopoly on the word "emergency".
The namespace "esnet" has been chosen, roughly to stand for The namespace 'esnet' has been chosen, roughly to stand for
"Emergency Services NETwork", for a citizen's call for help from a "Emergency Services NETwork", for a citizen's call for help from a
public authority type of organization. This namespace will also be public authority type of organization. This namespace will also be
used for communications between emergency authorities, and MAY be used for communications between emergency authorities, and MAY be
used for the ESInet to emergency authorities calling public used for emergency authorities calling public citizens. An example
citizens. An example of the latter is a PSAP operator calling back of the latter is a PSAP operator calling back someone who previously
someone who previously called 911/112/999 and the communication was called 911/112/999 and the communication was terminated before it -
terminated before it -in the PSAP operator's judgment - should have in the PSAP operator's judgment - should have been.
been.
Here is an example of a Resource-Priority header field using the Here is an example of a Resource-Priority header field using the
"esnet" namespace: 'esnet' namespace:
Resource-Priority: esnet.0 Resource-Priority: esnet.0
3.1. Namespace Definition Rules and Guidelines 3.1. Namespace Definition Rules and Guidelines
This specification defines one unique namespace for emergency This specification defines one unique namespace for emergency calling
calling scenarios, "esnet", constituting its registration with IANA. scenarios, 'esnet', constituting its registration with IANA. This
This IANA registration contains the facets defined in Section 9 of IANA registration contains the facets defined in Section 9 of
[RFC4412]. [RFC4412].
3.2. The "esnet" Namespace 3.2. The 'esnet' Namespace
Per the rules of [RFC4412], each namespace has a finite set of Per the rules of [RFC4412], each namespace has a finite set of
relative priority-value(s), listed (below) from lowest priority to relative priority-value(s), listed (below) from lowest priority to
highest priority. In an attempt to not limit this namespace's use highest priority. In an attempt to not limit this namespace's use in
in the future, more than one priority-value is assigned to the the future, more than one priority-value is assigned to the 'esnet'
"esnet" namespace. This document does not recommend which namespace. This document does not recommend which Priority-value is
Priority-value is used where in which situation or scenario. That used where in which situation or scenario. That is for another
is for another document to specify. To be effective, the choice document to specify. To be effective, the choice within a national
within a national jurisdiction needs to be coordinated by all jurisdiction needs to be coordinated by all sub-jurisdictions to
sub-jurisdictions to maintain uniform SIP behavior throughout an maintain uniform SIP behavior throughout an emergency calling system
emergency calling system of that nation of that nation
The relative priority order for the "esnet" namespace is as follows: The relative priority order for the 'esnet' namespace is as follows:
(lowest) esnet.0 (lowest) esnet.0
esnet.1 esnet.1
esnet.2 esnet.2
esnet.3 esnet.3
(highest) esnet.4 (highest) esnet.4
The "esnet" namespace will be in the priority queuing algorithm The 'esnet' namespace will have priority queuing registrations for
(Section 4.5.2 of [RFC4412]). Although no preemption is specified these levels per Section 4.5.2 of [RFC4412]. Although no preemption
in this document for any levels of esnet, local jurisdiction(s) MAY is specified in this document for any levels of esnet, local
configure their SIP infrastructure to use this namespace with jurisdiction(s) MAY configure their SIP infrastructure to use this
preemption, as defined in RFC 4412. namespace with preemption, as defined in RFC 4412.
The remaining rules originated in RFC 4412 apply with regard to an The remaining rules originated in RFC 4412 apply with regard to an RP
RP actor who understands more than one namespace, and is must actor who understands more than one namespace, and is must maintain
maintain its locally significant relative priority order. its locally significant relative priority order.
4. IANA Considerations 4. IANA Considerations
4.1 IANA Resource-Priority Namespace Registration 4.1. IANA Resource-Priority Namespace Registration
Within the "Resource-Priority Namespaces" of the sip-parameters Within the "Resource-Priority Namespaces" of the sip-parameters
section of IANA (created by [RFC4412]), the following entries will section of IANA (created by [RFC4412]), the following entries will be
be added to this table: added to this table:
Intended New warn- New resp. Intended New warn- New resp.
Namespace Levels Algorithm code code Reference Namespace Levels Algorithm code code Reference
--------- ------ -------------- --------- --------- --------- --------- ------ -------------- --------- --------- ---------
esnet 5 queue no no [This doc] esnet 5 queue no no [This doc]
4.2 IANA Priority-Value Registrations 4.2. IANA Priority-Value Registrations
Within the Resource-Priority Priority-values registry of the Within the Resource-Priority Priority-values registry of the sip-
sip-parameters section of IANA, the following (below) is to be added parameters section of IANA, the following (below) is to be added to
to the table: the table:
Namespace: esnet Namespace: esnet
Reference: (this document) Reference: (this document)
Priority-Values (least to greatest): "0", "1","2", "3", "4" Priority-Values (least to greatest): "0", "1","2", "3", "4"
5. Security Considerations 5. Security Considerations
The Security considerations that apply to RFC 4412 [RFC4412] apply The Security considerations that apply to RFC 4412 [RFC4412] apply
here. here.
For networks that act on the SIP Resource-Priority header field, For networks that act on the SIP Resource-Priority header field,
an incorrect use of a namespace can result in traffic that should incorrect use of namespaces can result in traffic that should have
have been given preferential treatment not be given it and vice been given preferential treatment not be given it and vice versa.
versa. This document does not define a use case where an endpoint This document does not define a use case where an endpoint outside
outside the ESInet marks its call for preferential treatment. the ESInet marks its call for preferential treatment. Protections
Protections need to be taken to prevent granting preferential need to be taken to prevent granting preferential treatment to
treatment to unauthorized users not calling for emergency help even unauthorized users not calling for emergency help even if they are in
if they are in the ESInet, as well as to prevent misuse by callers the ESInet, as well as to prevent misuse by callers outside the
outside the ESInet. ESInet.
A simple means of preventing this usage in an ESInet is to not A simple means of preventing this usage is to not allow 'esnet'
allow "esnet" marked traffic to get preferential treatment unless marked traffic to get preferential treatment unless the destination
the destination is towards the local/regional ESInet. This is not a is towards the local/regional ESInet. This is not a consideration
consideration for internetwork traffic within the ESInet, or for internetwork traffic within the ESInet, or generated out of the
generated out of the ESInet. 911/112/999 type of calling is fairly ESInet. 911/112/999 type of calling is fairly local in nature, with a
local in nature, with a finite number of URIs that are likely to be finite number of URIs that are likely to be considered valid within a
considered valid within a portion of a network receiving SIP portion of a network receiving SIP signaling.
signaling.
This namespace is not intended for use on the Internet because of This namespace is not intended for use on the Internet because of the
the difficulty in detecting abuse. Some networks may determine that difficulty in detecting abuse, specifically, it can trivially be
it can reasonably prevent abuse and/or the consequences of forged and used on a non-emergency session to obtain resource
undetected abuse is not significant. In such cases, use of esnet priority. Some networks may determine that it can reasonably prevent
MAY be allowed. abuse and/or the consequences of undetected abuse is not significant.
In such cases, use of esnet MAY be allowed.
6. Acknowledgements 6. Acknowledgements
Thanks to Ken Carlberg, Janet Gunn, Fred Baker and Keith Drage for Thanks to Ken Carlberg, Janet Gunn, Fred Baker and Keith Drage for
help and encouragement with this effort. Thanks to Henning help and encouragement with this effort. Thanks to Henning
Schulzrinne, Ted Hardie, Hannes Tschofenig, Brian Rosen, Janet Gunn Schulzrinne, Ted Hardie, Hannes Tschofenig, Janet Gunn and Marc
and Marc Linsner for constructive comments. A big thanks to Robert Linsner for constructive comments. A big thanks to Robert Sparks for
Sparks for being patient with the author. being patient with the author and Brian Rosen for completing the
final edits.
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
4412, Feb 2006
[RFC5031] H. Schulzrinne, "A Uniform Resource Name (URN) for Emergency 7. Normative References
and Other Well-Known Services", RFC 5031, January 2008
[RFC5478] J. Polk, "IANA Registration of New Session Initiation [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Protocol (SIP) Resource-Priority Namespaces", RFC 5478, Requirement Levels", BCP 14, RFC 2119, March 1997.
March 2009
[draft-rosen-rph-reg-policy] Rosen, B, "Resource-Priority Header [RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Registry Policy to IETF Review, draft-rosen-rph-policy-00 Priority for the Session Initiation Protocol (SIP)",
(work in progress), Feb 2013 RFC 4412, February 2006.
7.2 Informative References [RFC5031] H. Schulzrinne, "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
January 2008
none [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 Author's Address
James Polk James Polk
Cisco Systems
3913 Treemont Circle 3913 Treemont Circle
Colleyville, Texas 76034 Colleyville, TX 76034
USA USA
Phone: +1-817-271-3552 Phone: +1-817-271-3552
Email: jmpolk@cisco.com Email: jmpolk@cisco.com
 End of changes. 62 change blocks. 
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