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PROPOSED STANDARD
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Network Working Group                                      J. LivingoodRequest for Comments: 5278                 Comcast Cable CommunicationsCategory: Standards Track                                 D. Troshynski                                                            Acme Packet                                                              July 2008IANA Registration of Enumservices for Voice and Video MessagingStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   This document registers the Enumservice named "vmsg", which is used   to facilitate the real-time routing of voice, video, and unified   communications to a messaging system.  This vmsg Enumservice   registers three Enumservice types: "voicemsg", "videomsg", and   "unifmsg".  Each type also registers the subtypes "sip", "sips",   "http", and "https", as well as the subtype "tel" for the "voicemsg"   type.Livingood & Troshynski      Standards Track                     [Page 1]

RFC 5278                    VMSG Enumservice                   July 2008Table of Contents1. Introduction ....................................................31.1. Selected Use Cases for Illustrative Purposes ...............41.2. Consideration of Other Existing Enumservices ...............52. Distribution of Data ............................................53. Security Considerations .........................................54. ENUM Service Registration for voicemsg ..........................64.1. Registration for "voicemsg" with Subtype "sip" .............64.2. Registration for "voicemsg" with Subtype "sips" ............74.3. Registration for "voicemsg" with Subtype "tel" .............74.4. Registration for "voicemsg" with Subtype "http" ............84.5. Registration for "voicemsg" with Subtype "https" ...........95. ENUM Service Registration for videomsg .........................105.1. Registration for "videomsg" with Subtype "sip" ............105.2. Registration for "videomsg" with Subtype "sips" ...........105.3. Registration for "videomsg" with Subtype "http" ...........115.4. Registration for "videomsg" with Subtype "https" ..........126. ENUM Service Registration for unifmsg ..........................136.1. Registration for "unifmsg" with Subtype "sip" .............136.2. Registration for "unifmsg" with Subtype "sips" ............136.3. Registration for "unifmsg" with Subtype "http" ............146.4. Registration for "unifmsg" with Subtype "https" ...........157. Selected Examples for Illustrative Purposes ....................167.1. Example Using a 'sip' URI .................................167.2. Example Using a 'tel' URI .................................167.3. Example Using a Backreference .............................167.4. Example Using a 'sip' URI without a Telephone Number ......177.5. Example of Failover Using E2U+videomsg:sip ................178. Implementation Recommendations .................................178.1. Call Processing When Multiple Records Are Returned ........178.2. NAPTR Configuration Issues ................................189. IANA Considerations ............................................1810. Acknowledgements ..............................................1811. Contributors ..................................................1912. References ....................................................1912.1. Normative References .....................................1912.2. Informative References ...................................20Livingood & Troshynski      Standards Track                     [Page 2]

RFC 5278                    VMSG Enumservice                   July 20081.  Introduction   ENUM (E.164 Number Mapping,RFC 3761 [1]) is a technology that   transforms E.164 numbers (the International Public Telecommunication   Numbering Plan, ITU-T Recommendation E.164 [2]) into domain names and   then uses DNS (Domain Name System,RFC 1034 [3]) delegation through   NS records and Naming Authority Pointer (NAPTR) records (Dynamic   Delegation Discovery System (DDDS) Part Three: The Domain Name System   (DNS) Database,RFC 3403 [4]) to look up what services are available   for a specific domain name.   This document registers Enumservices according to the guidelines   given inRFC 3761 [1] to be used for provisioning in the services   field of a NAPTR [4] resource record to indicate the types of   functionality associated with an end point and/or telephone number.   The registration is defined within the DDDS (Dynamic Delegation   Discovery System [4][5][6][7][8]) hierarchy, for use with the "E2U"   DDDS Application defined inRFC 3761.   Voice messaging systems are used widely with telephony and voice   communication services.  The need for a voice messaging service type   has become clear in order to provide certain applications with direct   access to various voice messaging services (for example, voicemail),   most typically via the use of SIP.   The authors considered the use of Voice Profile for Internet Mail   (VPIM) [14] but found that VPIM was best suited to the non-real-time   and non-session-based routing of a voice message once it had been   deposited into a voice messaging system.  Thus, VPIM was a good   solution for the non-real-time and non-session-based routing of voice   messages between and within domains, but it did not enable real-time   interaction with a voice messaging system.   Thus, a need has been identified for this voice messaging service   type that would enable, for example, some of the use cases listed in   this section.   Video messaging systems, sometimes called visual voice messaging   systems, are beginning to be used with real-time communication   services.  The need for a video messaging service type has become   clear in order to provide certain applications with direct access to   various video messaging services, most typically via the use of SIP.   Thus, a need has been identified for this video messaging service   type that would enable, for example, some of the use cases listed in   this section.Livingood & Troshynski      Standards Track                     [Page 3]

RFC 5278                    VMSG Enumservice                   July 2008   Finally, several service providers and software developers have   indicated that their system for voice messaging and video messaging   either have been or soon will be unified into a single system.  As   such, they desired to have the option of using an Enumservice type   that represents a subscriber's mailbox as being a so-called unified   messaging repository.  Thus, a need has been identified for this   unified voice and video messaging service type that would enable, for   example, some of the use cases listed in this section.1.1.  Selected Use Cases for Illustrative Purposes   The following is a partial, non-exclusive list of use cases that the   vmsg Enumservice could address:   * A called party is busy or does not answer a call.  A client or     server then determines that a messaging service should be used and     sends the calling party's session to such a service.  The client or     server needs to be able to determine which server to direct this     real-time session to, whether that is within or outside of the     called party's domain.   * Similar to the above use case, a real-time session is attempted to     a messaging system, but that system is currently unavailable.     Since multiple service type records may be returned by the original     ENUM query, the client or server could then attempt to initiate a     session with one or more backup messaging servers in a manner that     is transparent to the calling party and that supports better     overall availability of a messaging service.   * Similar to the above use case, this service type could be used to     balance load across multiple messaging servers, whether those are     in the same or in different physical locations.   * A user with an account on a messaging service needs to connect to     the messaging service in order to retrieve messages.  They initiate     a real-time session, and an ENUM query is performed to discover the     messaging server that holds its mailbox.   * In the process of invoking and supporting a real-time, automated     and interactive session with a user, whether for message deposit or     retrieval, VoiceXML files are referenced and utilized, via either     HTTP or HTTPS.  Multiple VoiceXML servers could be associated with     a user and returned via ENUM query, for the purposes of load     balancing, for example.Livingood & Troshynski      Standards Track                     [Page 4]

RFC 5278                    VMSG Enumservice                   July 20081.2.  Consideration of Other Existing Enumservices   The authors considered whether this service type could simply use the   SIP Enumservice type [19], but found that it does not satisfy their   voice messaging requirements, particularly given the non-SIP URI sub-   types specified herein.  Even with sub-types for SIP URIs, however,   there are challenges to using the SIP Enumservice type.  For example,   a request for access to such a service could be extended to the   requesting SIP client, or User Agent Client (UAC), rather than   relying upon the local policy of a SIP server, or User Agent Server   (UAS), which means that special routing logic within a UAS cannot be   relied upon to solve this problem.  More importantly, however, the   authors have found that without this service type, a UAC or UAS will   be presented with multiple SIP URIs, with no ability other than in   non-standards-based routing rules or application logic to recognize   which one is related to a voice messaging, video messaging, or   unified voice and video messaging service.2.  Distribution of Data   The authors believe that it is more likely that these records will be   distributed on a purely private basis, but they may also be   distributed in public ENUM trees.  Distribution of this NAPTR data   could be either (a) on a private basis within a service provider's   internal network, (b) on a private basis between one or more parties   using a variety of security mechanisms to prohibit general public   access, or (c) openly available.3.  Security Considerations   DNS, as used by ENUM, is a global, distributed database.  Should   implementers of this specification use e164.arpa or any other   publicly available domain as the tree for maintaining voicemsg   Enumservice data, this information would be visible to anyone   anonymously.  While this is not qualitatively different from   publication in a Telephone Directory, it does open or ease access to   such data without any indication that such data has been accessed or   by whom it has been accessed.   Such data harvesting by third parties is often used to generate lists   of targets for unsolicited information.  Thus, a third party could   use this to generate a list that it can use to make unsolicited   telemarketing phone calls, or so-called SPAM over Internet Telephony   (SPIT).  Many countries have do-not-call registries or other legal or   regulatory mechanisms in place to deal with such abuses.Livingood & Troshynski      Standards Track                     [Page 5]

RFC 5278                    VMSG Enumservice                   July 2008   As noted earlier, carriers, service providers, and other users may   simply choose not to publish such information in the public e164.arpa   tree, but may instead simply publish this in their internal ENUM   routing database that is only able to be queried by trusted elements   of their network and/or partner networks, such as softswitches and   SIP proxy servers.  They may also choose to publish such information   in a carrier-only branch of the e164.arpa tree, should one be   created.   Although an E.164 telephone number does not appear to reveal as much   identity information about a user as a name in the format   sip:username@hostname or email:username@hostname, the information is   still publicly available; thus, there is still the risk of unwanted   communication.   An analysis of threats specific to the dependence of ENUM on the DNS   and the applicability of DNSSEC [16] to this is provided inRFC 3761   [1].  A thorough analysis of threats to the DNS itself is covered inRFC 3833 [17].4.  ENUM Service Registration for voicemsg4.1.  Registration for "voicemsg" with Subtype "sip"   Enumservice Name: "voicemsg"   Enumservice Type: "voicemsg"   Enumservice Subtypes: "sip"   URI Schemes: 'sip:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a voice   communication session to a voice messaging system.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)Livingood & Troshynski      Standards Track                     [Page 6]

RFC 5278                    VMSG Enumservice                   July 2008   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.4.2.  Registration for "voicemsg" with Subtype "sips"   Enumservice Name: "voicemsg"   Enumservice Type: "voicemsg"   Enumservice Subtypes: "sips"   URI Schemes: 'sips:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a voice   communication session to a voice messaging system.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.4.3.  Registration for "voicemsg" with Subtype "tel"   Enumservice Name: "voicemsg"   Enumservice Type: "voicemsg"   Enumservice Subtype: "tel"   URI Schemes: 'tel:'Livingood & Troshynski      Standards Track                     [Page 7]

RFC 5278                    VMSG Enumservice                   July 2008   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a voice   communication session to a voice messaging system.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.4.4.  Registration for "voicemsg" with Subtype "http"   Enumservice Name: "voicemsg"   Enumservice Type: "voicemsg"   Enumservice Subtype: "http"   URI Schemes: 'http:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'http:' [11] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even voice message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMONLivingood & Troshynski      Standards Track                     [Page 8]

RFC 5278                    VMSG Enumservice                   July 2008   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.4.5.  Registration for "voicemsg" with Subtype "https"   Enumservice Name: "voicemsg"   Enumservice Type: "voicemsg"   Enumservice Subtype: "https"   URI Schemes: 'https:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information,   which can be contacted using TLS or the Secure Socket Layer protocol.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'https:' [12] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even voice message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.Livingood & Troshynski      Standards Track                     [Page 9]

RFC 5278                    VMSG Enumservice                   July 20085.  ENUM Service Registration for videomsg5.1.  Registration for "videomsg" with Subtype "sip"   Enumservice Name: "videomsg"   Enumservice Type: "videomsg"   Enumservice Subtypes: "sip"   URI Schemes: 'sip:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a video   communication session to a video messaging system.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.5.2.  Registration for "videomsg" with Subtype "sips"   Enumservice Name: "videomsg"   Enumservice Type: "videomsg"   Enumservice Subtypes: "sips"   URI Schemes: 'sips:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a video   communication session to a video messaging system.Livingood & Troshynski      Standards Track                    [Page 10]

RFC 5278                    VMSG Enumservice                   July 2008   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.5.3.  Registration for "videomsg" with Subtype "http"   Enumservice Name: "videomsg"   Enumservice Type: "videomsg"   Enumservice Subtype: "http"   URI Schemes: 'http:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'http:' [11] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even video message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)Livingood & Troshynski      Standards Track                    [Page 11]

RFC 5278                    VMSG Enumservice                   July 2008   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.5.4.  Registration for "videomsg" with Subtype "https"   Enumservice Name: "videomsg"   Enumservice Type: "videomsg"   Enumservice Subtype: "https"   URI Schemes: 'https:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information,   which can be contacted using TLS or the Secure Socket Layer protocol.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'https:' [12] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even video message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.Livingood & Troshynski      Standards Track                    [Page 12]

RFC 5278                    VMSG Enumservice                   July 20086.  ENUM Service Registration for unifmsg6.1.  Registration for "unifmsg" with Subtype "sip"   Enumservice Name: "unifmsg"   Enumservice Type: "unifmsg"   Enumservice Subtypes: "sip"   URI Schemes: 'sip:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a unified   communication session to a unified messaging system.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.6.2.  Registration for "unifmsg" with Subtype "sips"   Enumservice Name: "unifmsg"   Enumservice Type: "unifmsg"   Enumservice Subtypes: "sips"   URI Schemes: 'sips:'   Functional Specification:   This Enumservice indicates that the remote resource identified can be   addressed by the associated URI scheme in order to initiate a unified   communication session to a unified messaging system.Livingood & Troshynski      Standards Track                    [Page 13]

RFC 5278                    VMSG Enumservice                   July 2008   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.6.3.  Registration for "unifmsg" with Subtype "http"   Enumservice Name: "unifmsg"   Enumservice Type: "unifmsg"   Enumservice Subtype: "http"   URI Schemes: 'http:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'http:' [11] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even video message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)Livingood & Troshynski      Standards Track                    [Page 14]

RFC 5278                    VMSG Enumservice                   July 2008   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.6.4.  Registration for "unifmsg" with Subtype "https"   Enumservice Name: "unifmsg"   Enumservice Type: "unifmsg"   Enumservice Subtype: "https"   URI Schemes: 'https:'   Functional Specification:   This Enumservice indicates that the remote resource identified by the   associated URI scheme is capable of being a source of information,   which can be contacted using TLS or the Secure Socket Layer protocol.   Note that the kind of information retrieved can be manifold. Usually,   contacting a resource by an 'https:' [12] URI provides a document.   This document can contain references that will trigger the download   of many different kinds of information, such as text, audio, video,   executable code, or even video message files.  Thus, one cannot be   more specific about the kind of information expected when contacting   the resource.   Security Considerations: SeeSection 3.   Intended Usage: COMMON   Authors:   Jason Livingood (jason_livingood@cable.comcast.com)   Don Troshynski (dtroshynski@acmepacket.com)   Any other information the author deems interesting:   Implementers should review a non-exclusive list of examples below inSection 7.Livingood & Troshynski      Standards Track                    [Page 15]

RFC 5278                    VMSG Enumservice                   July 20087.  Selected Examples for Illustrative Purposes   The following sub-sections document several examples that   implementers may find informative.  These examples shall in no way   limit the various forms that this Enumservice may take.7.1.  Example Using a 'sip' URI      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 100 "u" "E2U+voicemsg:sip"         "!^.*$!sip:12155550123@gw.example.com!".   In this example, a calling party has attempted a session that has   gone unanswered after a certain period of time.  The calling party's   session is sent to the appropriate voice messaging server, a   personalized greeting is played to the calling party, after which it   records a voice message to the called party.7.2.  Example Using a 'tel' URI      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 100 "u" "E2U+voicemsg:tel"         "!^.*$!tel:1-215-555-0123!".   In this example, a calling party has attempted a session that has   gone unanswered after a certain period of time.  The calling party's   session is sent to the appropriate voice messaging server, a   personalized greeting is played to the calling party, after which it   records a voice message to the called party.7.3.  Example Using a Backreference      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 100 "u" "E2U+voicemsg:sip"         "!(^.*)$!sip:\1@example.net!".   In this example, a backreference is used to reduce the size of the   NAPTR record.  The sip URI uses "\1", which would dynamically replace   the expression with the TN, in this case +12155550123.Livingood & Troshynski      Standards Track                    [Page 16]

RFC 5278                    VMSG Enumservice                   July 20087.4.  Example Using a 'sip' URI without a Telephone Number      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 100 "u" "E2U+voicemsg:sip"         "!^.*$!sip:johndoe@gw.example.com!".   In this example, a calling party has attempted a session that has   gone unanswered after a certain period of time.  The calling party's   session is sent to the appropriate voice messaging server, a   personalized greeting is played to the calling party, after which it   records a voice message to the called party.  The URI that this   session is directed to does not include a telephone number, as this   user has multiple service that are not particularly tied to telephone   numbers whereby text, audio, video and other multimedia messages can   be received and accessed.7.5.  Example of Failover Using E2U+videomsg:sip      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 100 "u" "E2U+videomsg:sip"         "!^.*$!sip:12155550123@gw1.example.com!".      $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.         NAPTR 10 200 "u" "E2U+videomsg:sip"         "!^.*$!sip:12155550123@gw2.example.com!".   In this example, the preference indicates that gw1.example.com is   used first (100), and if this is unreachable, then the next higher   preference (200) is used and gw2.example.com is contacted.  While out   of scope for this document, a service provider could thus mirror or   cluster a message store and fail from the primary to secondary using   the DNS in an active-standby mode.8.  Implementation Recommendations8.1.  Call Processing When Multiple Records Are Returned   It is likely that both E2U+sip and E2U+voicemsg, E2U+videomsg, and/or   E2U+unifmsg Enumservice type records will be returned for a given   query.  In this case, this could result in what is essentially   E2U+sip records for real-time communications with an end user, while,   for example, the E2U+voicemsg records will be used for real-time   communications with a voice messaging service, when the called party   is not available or does not wish to be disturbed.  Therefore, the   network element that receives the results of this ENUM query will   need to know enough information in order to select the voicemsg   service type, rather than the sip service type.Livingood & Troshynski      Standards Track                    [Page 17]

RFC 5278                    VMSG Enumservice                   July 2008   In addition, it is likely that multiple E2U+voicemsg, E2U+videomsg,   and/or E2U+unifmsg Enumservice type records will be returned for a   given query.  In this case, multiple records may include order and   preference to allow recursion or load balancing.  Order could be used   to designate a primary and a backup voice, video, or unified voice   and video messaging service.  Preference could be used to load   balance across multiple voice, video, and/or unified voice and video   messaging servers by weight, for example.   Finally, as with multiple records resulting from a typical ENUM query   of the e164.arpa tree, it is up to the application using an ENUM   resolver to determine which record(s) to use and which record(s) to   ignore.  Implementers should take this into consideration and build   logic into their applications that can select appropriately from   multiple records based on business, network, or other rules.8.2.  NAPTR Configuration Issues   Implementers may wish to consider using regular expressions in order   to reduce the size of individual NAPTRs.  This will have a   significant effect on the overall size of the database involved.9.  IANA Considerations   This document registers the 'voicemsg' Enumservice type and the   subtype "tel", "sip", "sips", "http", and "https" under the   Enumservice registry described in the IANA considerations inRFC3761.  Details of this registration are provided inSection 4 of this   document.   This document registers the 'videomsg' Enumservice type and the   subtype "sip", "sips", "http", and "https" under the Enumservice   registry described in the IANA considerations inRFC 3761.  Details   of this registration are provided inSection 5 of this document.   This document registers the 'unifmsg' Enumservice type and the   subtype "sip", "sips", "http", and "https" under the Enumservice   registry described in the IANA considerations inRFC 3761.  Details   of this registration are provided inSection 6 of this document.10.  Acknowledgements   The authors thank Rich Ferrise, Chris Harvey, Tong Zhou, and Hadriel   Kaplan for their detailed assistance in developing the ideas behind   this document in numerous brainstorming sessions, with information   gleaned from their work to solve real application architecture   issues.  The authors also thank Lawrence Conroy and Jean-Francois   Mule for their feedback in developing this document.Livingood & Troshynski      Standards Track                    [Page 18]

RFC 5278                    VMSG Enumservice                   July 200811.  Contributors   Tong Zhou   Comcast Cable Communications   Email: tong_zhou@cable.comcast.com   Richard Ferrise   Comcast Cable Communications   Email: rich_ferrise@cable.comcast.com   Chris Harvey   Comcast Cable Communications   Email: chris_harvey@cable.comcast.com   Hadriel Kaplan   Acme Packet   Email: hkaplan@acmepacket.com12.  References12.1.  Normative References   [1]   Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource         Identifiers (URI) Dynamic Delegation Discovery System (DDDS)         Application (ENUM)",RFC 3761, April 2004.   [2]   ITU-T, "The International Public Telecommunication Numbering         Plan", Recommendation E.164, May 1997.   [3]   Mockapetris, P., "Domain names - concepts and facilities", STD         13,RFC 1034, November 1987.   [4]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part         Three: The Domain Name System (DNS) Database",RFC 3403,         October 2002.   [5]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part         One: The Comprehensive DDDS",RFC 3401, October 2002.   [6]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part         Two: The Algorithm",RFC 3402, October 2002.   [7]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part         Four: The Uniform Resource Identifiers (URI)",RFC 3404,         October 2002.Livingood & Troshynski      Standards Track                    [Page 19]

RFC 5278                    VMSG Enumservice                   July 2008   [8]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part         Five: URI.ARPA Assignment Procedures",BCP 65,RFC 3405,         October 2002.   [9]   Schulzrinne, H., "The tel URI for Telephone Numbers",RFC 3966,         December 2004.   [10]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:         Session Initiation Protocol",RFC 3261, June 2002.   [11]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,         Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --         HTTP/1.1",RFC 2616, June 1999.   [12]  Rescorla, E., "HTTP Over TLS",RFC 2818, May 2000.12.2.  Informative References   [13]  Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164         numbers with the Session Initiation Protocol (SIP)",RFC 3824,         June 2004.   [14]  Vaudreuil, G., "Voice Message Routing Service",RFC 4238,         October 2005.   [15]  Brandner, R., Conroy, L., and R. Stastny, "IANA Registration         for Enumservices email, fax, mms, ems, and sms",RFC 4355,         January 2006.   [16]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,         "Protocol Modifications for the DNS Security Extensions",RFC4035, March 2005.   [17]  Atkins, D. and R. Austein, "Threat Analysis of the Domain Name         System (DNS)",RFC 3833, August 2004.   [18]  Foster, M., McGarry, T., and J. Yu, "Number Portability in the         Global Switched Telephone Network (GSTN): An Overview",RFC3482, February 2003.   [19]  Peterson, J., "enumservice registration for Session Initiation         Protocol (SIP) Addresses-of-Record",RFC 3764, April 2004.Livingood & Troshynski      Standards Track                    [Page 20]

RFC 5278                    VMSG Enumservice                   July 2008Authors' Addresses   Jason Livingood   Comcast Cable Communications   One Comcast Center   1701 John F. Kennedy Boulevard   Philadelphia, PA 19103   USA   EMail: jason_livingood@cable.comcast.com   Donald Troshynski   Acme Packet   EMail: dtroshynski@acmepacket.comLivingood & Troshynski      Standards Track                    [Page 21]

RFC 5278                    VMSG Enumservice                   July 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Livingood & Troshynski      Standards Track                    [Page 22]

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