IANA Registering a SIP Resource Priority Header Field Namespace for Local Emergency Communications
Author(s): James Polk
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...
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 This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 26, 2013. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Polk Expires August 26, 2013 [Page 1] Internet-Draft Emergency RPH Namespace February 2013 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 Polk Expires August 26, 2013 [Page 2] Internet-Draft Emergency RPH Namespace February 2013 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 [RFC 4412]. 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 Polk Expires August 26, 2013 [Page 3] Internet-Draft Emergency RPH Namespace February 2013 ease of forging the header. This document merely creates the namespace, per the rules within [RFC 4412] 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 [RFC 2119]. 2. Rules of Usage of the Resource Priority Header field This document retains the behaviors of the SIP Resource Priority header field, defined in [RFC 4412], 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. Polk Expires August 26, 2013 [Page 4] Internet-Draft Emergency RPH Namespace February 2013 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 [RFC 4412]. SIP entities that support preemption treatment (see Section 5 of [RFC 4412]) 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: Polk Expires August 26, 2013 [Page 5] Internet-Draft Emergency RPH Namespace February 2013 |<-'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. Polk Expires August 26, 2013 [Page 6] Internet-Draft Emergency RPH Namespace February 2013 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 ([RFC 4412] defines 3 of these), some on a national scale ([RFC 4412] 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 [RFC 4412]. 3.2. The 'esnet' Namespace Per the rules of [RFC 4412], 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: Polk Expires August 26, 2013 [Page 7] Internet-Draft Emergency RPH Namespace February 2013 (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 [RFC 4412]. 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 [RFC 4412]), 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 [RFC 4412] apply here. For networks that act on the SIP Resource-Priority header field, Polk Expires August 26, 2013 [Page 8] Internet-Draft Emergency RPH Namespace February 2013 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 [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 4412] Schulzrinne, H. and J. Polk, "Communications Resource Priority for the Session Initiation Protocol (SIP)", RFC 4412, February 2006. Polk Expires August 26, 2013 [Page 9] Internet-Draft Emergency RPH Namespace February 2013 [RFC 5031] 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: email@example.com Polk Expires August 26, 2013 [Page 10]