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diff --git a/doc/rfc/rfc7135.txt b/doc/rfc/rfc7135.txt new file mode 100644 index 0000000..854e912 --- /dev/null +++ b/doc/rfc/rfc7135.txt @@ -0,0 +1,507 @@ + + + + + + +Internet Engineering Task Force (IETF) J. Polk +Request for Comments: 7135 Cisco Systems +Category: Informational May 2014 +ISSN: 2070-1721 + + + Registering a SIP Resource Priority Header Field Namespace for + Local Emergency Communications + +Abstract + + This document creates the new Session Initiation Protocol (SIP) + Resource Priority header field namespace 'esnet' and registers this + namespace with IANA. The new header field namespace allows for local + emergency session establishment to a public safety answering point + (PSAP), between PSAPs, and between a PSAP and first responders and + their organizations. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7135. + +Copyright Notice + + Copyright (c) 2014 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 + described in the Simplified BSD License. + + + +Polk Informational [Page 1] + +RFC 7135 Emergency RPH Namespace May 2014 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 + 2. Rules of Usage of the Resource Priority Header Field . . . . . 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. Normative References . . . . . . . . . . . . . . . . . . . . . 9 + +1. Introduction + + This document creates the new Session Initiation Protocol (SIP) + Resource Priority header (RPH) field namespace 'esnet' for local + emergency usage and registers this namespace with IANA. 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 an RPH with the 'esnet' namespace can be differentiated from + the marking of an emergency call using a service URN as defined in + [RFC5031] in that the RPH specifically requests preferential + treatment in networks that 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 IP + Multimedia Subsystem (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 + + + +Polk Informational [Page 2] + +RFC 7135 Emergency RPH Namespace May 2014 + + + 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 (ASPs) that are 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 User Agent ("call back") when priority is needed. + Again, the request for priority is not for use on the public Internet + due to the ease of forging the header. + + This document merely creates the namespace, per the rules within + [RFC4412] as updated by [RFC7134], which necessitates that new RPH + namespaces and their relative priority-value order be IETF reviewed + before being registered with IANA. + + There is the possibility that within emergency services networks, + Multilevel Precedence and Preemption (MLPP)-like behavior can be + achieved (likely without the 'preemption' part), provided the 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. This document does not define MLPP-like SIP + signaling for emergency calls like those using emergency service + numbers (such as 911, 112, and 999), 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 has 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 registers the + 'esnet' RPH namespace with IANA for use within any emergency services + networks, not just of those from citizens to PSAPs. + + + +Polk Informational [Page 3] + +RFC 7135 Emergency RPH Namespace May 2014 + + + 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], when choosing between the + treatment options surrounding this new 'esnet' namespace. Given the + environment this is to be used within (i.e., within an ESInet), the + usage of the 'esnet' namespace does not have a 'normal' or routine + call level; that is left for local jurisdictions to define within + their respective parts of the ESInet, which could be islands of local + administration. + + The 'esnet' namespace MUST only be used where at least one end of the + signaling, setting aside the placement of B2BUAs (Back-to-Back User + Agents), is within a local emergency organization. In other words, + if either the originating human caller's User Agent (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. + + + + + + + + + + + + + + + + + + + + + + + +Polk Informational [Page 4] + +RFC 7135 Emergency RPH Namespace May 2014 + + + The following network diagram provides one example of local policy + choices when using the 'esnet' namespace: + + |<-'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 the 'esnet' Namespace + + In the figure, 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 is 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 + + + +Polk Informational [Page 5] + +RFC 7135 Emergency RPH Namespace May 2014 + + + 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 the scope of this document. + +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), and some on an international scale. + Each type of emergency can also have its own namespace(s); although + there are many defined for other uses, more are possible -- so using + the public emergency service number (such as 911, 112, or 999) to + call for police officers, firefighters, or emergency medical + technicians (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 it MAY be + used by emergency authorities to call public citizens. An example of + the latter is a PSAP operator calling back someone who previously + called an emergency service number (such as 911, 112, or 999) and the + communication was terminated before it -- in the PSAP operator's + judgment -- should have been. + + Below 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' and registers this namespace 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 + + + + + +Polk Informational [Page 6] + +RFC 7135 Emergency RPH Namespace May 2014 + + + 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: + + (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 that originated in RFC 4412 apply with regard to + an RP actor who understands more than one namespace, and must + maintain its locally significant relative priority order. + +4. IANA Considerations + +4.1. IANA Resource-Priority Namespace Registration + + The following entry has been added to the "Resource-Priority + Namespaces" registry of the sip-parameters section of IANA (created + by [RFC4412]): + + Intended New New resp. + Namespace Levels Algorithm Code warn-code Reference + --------- ------ ----------- --------- --------- --------- + esnet 5 queue no no RFC 7135 + +4.2. IANA Priority-Value Registrations + + The following entry has been added to the "Resource-Priority + Priority-values" registry of the sip-parameters section of IANA: + + Namespace: esnet + Reference: (this document) + Priority-Values (least to greatest): "0", "1","2", "3", "4" + + + + + + + + +Polk Informational [Page 7] + +RFC 7135 Emergency RPH Namespace May 2014 + + +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, + incorrect use of namespaces can result in traffic that should have + been given preferential treatment not receiving it, and vice versa. + This document does not define a use case where an endpoint outside + the ESInet marks its call for preferential treatment. Precautions + 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 traffic + marked 'esnet' 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. Calling an emergency service number (such as 911, 112, or + 999) 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 that the consequences of undetected abuse is not + significant. In such cases, use of 'esnet' on the Internet 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, 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. + + + + + + + + + + + +Polk Informational [Page 8] + +RFC 7135 Emergency RPH Namespace May 2014 + + +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. + + [RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for + Emergency and Other Well-Known Services", RFC 5031, + January 2008. + + [RFC7134] Rosen, B., "The Management Policy of the Resource Priority + Header (RPH) Registry Changed to "IETF Review"", RFC 7134, + March 2014. + +Author's Address + + James Polk + Cisco Systems + 3913 Treemont Circle + Colleyville, TX 76034 + USA + + Phone: +1-817-271-3552 + EMail: jmpolk@cisco.com + + + + + + + + + + + + + + + + + + + + + + + + +Polk Informational [Page 9] + |