RFC 4355

IANA Registration for Enumservices email, fax, mms, ems, and sms

📅 published January 2006, from ietf

RFC 4355: IANA Registration for Enumservices email, fax, mms, ems, and sms 📮✨

RFC: 4355 Title: IANA Registration for Enumservices email, fax, mms, ems, and sms Authors: R. Brandner (Siemens AG), L. Conroy (Siemens Roke Manor Research), R. Stastny (Oefeg) Category: Standards Track Date: January 2006 Obsoletes / Updates: the title block doesn't list anything it obsoletes or updates 🙌

Okay bestie, this one is all about registering five Enumservices so that phone numbers can point at email, fax, and text-message services. Let's get into it 🧚

Status of This Memo 📜

This document is an Internet standards track protocol for the Internet community, and it's asking for discussion and suggestions for improvements 💬 For the official standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1). Distribution of this memo is unlimited 🌸

Copyright Notice ©️

Copyright (C) The Internet Society (2006).

Abstract 🎀

This document registers the Enumservices "email", "fax", "sms", "ems", and "mms" using the URI schemes 'tel:' and 'mailto:'. It does this through the IANA registration process from the ENUM specification, RFC 3761 💅

Table of Contents 🗂️

1. Introduction ....................................................2
2. Terminology .....................................................3
3. Email Service Registration ......................................4
4. Fax Service Registration ........................................4
5. MMS, EMS, SMS Service ...........................................5
   5.1. Introduction ...............................................5
   5.2. SMS Service Registrations ..................................6
        5.2.1. SMS Service Registration with tel: URI ..............6
        5.2.2. SMS Service Registration with mailto: URI ...........6
   5.3. EMS Service Registrations ..................................7
        5.3.1. EMS Service Registration with tel: URI ..............7
        5.3.2. EMS Service Registration with mailto: URI ...........8
   5.4. MMS Service Registrations ..................................9
        5.4.1. MMS Service Registration with tel: URI ..............9
        5.4.2. MMS Service Registration with mailto: URI ..........10
6. Security Considerations ........................................11
7. Acknowledgements ...............................................13
8. References .....................................................13
   8.1. Normative References ......................................13
   8.2. Informative References ....................................14

1. Introduction ✨

Okay so, ENUM (E.164 Number Mapping, RFC 3761 [2]) is a system that turns E.164 numbers [3] into domain names. Then it uses DNS (Domain Name Service, RFC 1034 [4]) stuff like delegation through NS records and NAPTR records to figure out which services are available for that domain name 📞🔍

This document registers Enumservices following the guidelines in RFC 3761. They go in the services field of a NAPTR [5] resource record, and they tell you what kind of functionality an endpoint offers 🦋 The registration lives inside the DDDS (Dynamic Delegation Discovery System [6][7][5][8][9]) hierarchy, and it's meant for the "E2U" DDDS Application defined in RFC 3761 💜

The Enumservices registered here are "email", "fax", "sms", "ems", and "mms". They're all giving the same vibe: each one says the endpoint and its resources can receive discrete messages, just different types of messages 💌

According to RFC 3761, an Enumservice has to work as a selection mechanism when you're choosing one NAPTR resource record over another. So the registration MUST specify what's expected when you use that exact NAPTR record, plus the Uniform Resource Identifier (URI) scheme that comes out of using it 🫶

So an Enumservice acts like a hint. It tells you what kind of service the URI built from the regexp field is for 🌈 One NAPTR can hold more than one Enumservice, which means there's more than one service you can reach with that same URI scheme ✨

The common thread here is that these definitions reflect the kind of service an end-user hopes to get out of communicating with that URI 🎀

The services in this document are not meant to pin down the protocol or even the connection method used to deliver each service. Instead they describe the kind of interactive behaviour an end-user expects, and the end system decides how to run the service based on policies outside this specification 🧚‍♀️

Here's the thing: the same URI scheme can be used for different services (for example 'tel:'), and the same kind of service can use different URI schemes (for VoIP, 'h323:' and 'tel:' can both be used). So sometimes you do need to name both the service and the URI scheme 💅

The service parameters in RFC 3761 let you specify a "type" and a "subtype". In this set of specs, the "type" is the more generic term and defines the service, while the "subtype" defines the URI scheme 🍓

Even when only one URI scheme is linked to a service right now, you should keep in mind that another URI scheme might get added to that service later. That's why the subtype is needed: it identifies the specific Enumservice you mean 🦄

This document uses two URI schemes across the various services: 'tel:', as specified in RFC 3966 [10], and 'mailto:', as specified in RFC 2368 [11] 📧📱

2. Terminology 📖

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 BCP 14, RFC 2119 [1] 🔥

3. Email Service Registration 💌

Here's the registration template for "email", copied exactly:

Enumservice Name: "email"

Enumservice Type: "email"

Enumservice Subtypes: "mailto"

URI Scheme: 'mailto:'

Functional Specification:

   This Enumservice indicates that the remote resource can be
   addressed by the associated URI scheme in order to send an email.

Security Considerations:

   See Section 6.

Intended Usage: COMMON

Authors:

   Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author
   contact detail, see Authors' Addresses section)

Any other information the author deems interesting:

   None

Put simply, this one means the remote resource can be reached through the 'mailto:' URI scheme so you can send an email to it 📨 Security considerations live in Section 6, so go check there 🔐

4. Fax Service Registration 📠

Here's the registration template for "fax", copied exactly:

Enumservice Name: "fax"

Enumservice Type: "fax"

Enumservice Subtype: "tel"

URI Scheme: 'tel:'

Functional Specification:

   This Enumservice indicates that the resource identified by the
   associated URI scheme is capable of being contacted to provide a
   communication session during which facsimile documents can be
   sent.

   Clients selecting this NAPTR will have support for generating and
   sending facsimile documents to the recipient using the Public
   Switched Telephone Network (PSTN) session and transfer protocols
   specified in [12] and [13].  In short, they will have a fax
   program with a local or shared PSTN access over which they can
   send faxes.

Security Considerations:

   See Section 6.

Intended Usage: COMMON

Authors:

   Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author
   contact detail see Authors' Addresses section)

Any other information the author deems interesting:

   None

So a fax Enumservice means the resource can be contacted over 'tel:' to set up a session where facsimile documents get sent 📠✨ Clients that pick this NAPTR need to be able to generate and send fax documents over the PSTN using the protocols in [12] and [13]. Basically, they need a fax program with local or shared PSTN access to actually send the faxes 🖨️💖

5. MMS, EMS, SMS Service 📱

5.1. Introduction 🌸

An ENUM NAPTR shows that the Subscriber can receive a specified communication service (or services) through the contact address shown in the generated URI 💜

For MMS, EMS, and SMS, the capabilities form a nested superset. So a service that supports MMS can also deliver EMS or SMS message content to a recipient who's receiving a Multimedia Message 🫧 And a service that supports EMS can deliver SMS message content to a recipient who can accept EMS Messages 🦋

So even if a client only wants to generate and send content that could go in an SMS message, the client MAY also consider NAPTRs that hold EMS and/or MMS Enumservices. Those show the destination can accept EMS and/or MMS messages, and those services can deliver SMS content to the recipient address 🌈

It works the other way around too. A client that can send MMS messages MAY also consider NAPTRs that show support for EMS or SMS messages. This only works if the network it's connected to provides those services too (or can gateway to systems that do). If the client makes that choice, it would have to "downgrade" its User Interface so it only allows content that follows the SMS or EMS standards 💅

These client behaviours are purely optional, and they are NOT the subject of any protocol standardisation 🙈

5.2. SMS Service Registrations 💬

5.2.1. SMS Service Registration with tel: URI 📱

Here's the registration template for "sms" with 'tel:', copied exactly:

Enumservice Name: "sms"

Enumservice Type: "sms"

Enumservice Subtypes: "tel"

URI Scheme: 'tel:'

Functional Specification:

   This Enumservice indicates that the resource identified by the
   associated URI scheme is capable of receiving a message using the
   Short Message Service (SMS) [14].

Security Considerations:

   There are no specific security issues with this Enumservice.
   However, the general considerations of Section 6 apply.

Intended Usage: COMMON

Authors:

   Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author
   contact detail, see Authors' Addresses section)

Any other information the author deems interesting:

   None

So this one says the 'tel:' resource can receive an SMS [14] message 💌 There aren't any specific security issues for this Enumservice, but the general considerations in Section 6 still apply 🔐

5.2.2. SMS Service Registration with mailto: URI 💌

Here's the registration template for "sms" with 'mailto:', copied exactly:

Enumservice Name: "sms"

Enumservice Type: "sms"

Enumservice Subtypes: "mailto"
URI Scheme: 'mailto:'

Functional Specification:

   This Enumservice indicates that the resource identified by the
   associated URI scheme is capable of receiving a message using an
   email protocol.

   SMS content is sent over SMTP using the format specified by TS
   23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4, as an MMS
   message.  Within such a message, SMS content is carried as either
   a text or application/octet-stream MIME sub-part (see TS 26.140
   [16] Section 4.1).

Security Considerations:

   There are no specific security issues with this Enumservice.
   However, the general considerations of Section 6 apply.

Intended Usage: COMMON

Authors:

   Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author
   contact detail, see Authors' Addresses section)

Any other information the author deems interesting:

   None

This version says the 'mailto:' resource can receive a message over an email protocol 📧 The SMS content gets sent over SMTP in the format from TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4, as an MMS message 🍓 Inside that message, the SMS content is carried as either a text or application/octet-stream MIME sub-part (see TS 26.140 [16] Section 4.1) 🧚‍♀️ Same deal on security: no specific issues here, but the general considerations in Section 6 still apply 🔐

5.3. EMS Service Registrations 🌟

5.3.1. EMS Service Registration with tel: URI

Enumservice Name: "ems"
Enumservice Type: "ems"
Enumservice Subtype: "tel"
URI Scheme: 'tel:'

Functional Specification: okay so this one says the resource behind the tel: URI is capable of receiving a message using the Enhanced Message Service (EMS) [14]. slay 💖

Security Considerations: there are no specific security issues with this one 🫶 but the general considerations of Section 6 still apply, so don't skip them bestie!

Intended Usage: COMMON ✨

Authors: Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author contact detail, see Authors' Addresses section) 🎀

Any other information the author deems interesting: an indication of EMS can be taken as implying that the recipient is capable of receiving SMS messages at this address as well. no cap, that's a whole bonus 🦋

5.3.2. EMS Service Registration with mailto: URI

Enumservice Name: "ems"
Enumservice Type: "ems"
Enumservice Subtypes: "mailto"
URI Scheme: 'mailto:'

Functional Specification: this one says the resource behind the mailto: URI is capable of receiving a message using an email protocol 📧

EMS content is sent over SMTP using the format specified by TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4, as an MMS message. Inside that message, the EMS content is carried as either a text or application/octet-stream MIME sub-part (see TS 26.140 [16] section 4.1). the packaging is giving very organized 🧚

Security Considerations: there are no specific security issues with this Enumservice 💅 but the general considerations of Section 6 apply, so keep those in your back pocket!

Intended Usage: COMMON

Authors: Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author contact detail, see Authors' Addresses section) 🌸

Any other information the author deems interesting: None 🙈

5.4. MMS Service Registrations 📱

5.4.1. MMS Service Registration with tel: URI

Enumservice Name: "mms"
Enumservice Type: "mms"
Enumservice Subtype: "tel"
URI Scheme: 'tel:'

Functional Specification: this one says the resource behind the tel: URI is capable of receiving a message using the Multimedia Messaging Service (MMS) [15]. main character energy 👑

Security Considerations: there are no specific security issues with this Enumservice 💅 however, the general considerations of Section 6 apply.

Intended Usage: COMMON

Authors: Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author contact detail, see Authors' Addresses section) 🫶

Any other information the author deems interesting: okay this part is lowkey important 👀 MMS can be used as an alternative to deliver an SMS RP-DATA RPDU if, for example, the SMS bearer is not supported. If an entry includes this Enumservice, then in effect this can be taken as implying that the recipient is capable of receiving EMS or SMS messages at this address.

there are two small caveats though. whilst in practice all terminals supporting MMS today support SMS as well, it might not necessarily be the case in the future. and there may be tariff differences in using the MMS rather than using the SMS or EMS 💸

5.4.2. MMS Service Registration with mailto: URI

Enumservice Name: "mms"
Enumservice Type: "mms"
Enumservice Subtypes: "mailto"
URI Scheme: 'mailto:'

Functional Specification: this one says the resource behind the mailto: URI is capable of receiving a message using an email protocol 💌

MMS messages are sent over SMTP using the format specified by TS 23.140 [15] Section 8.4.4 and TS 26.140 [16] Section 4.

Within and between MMS Environments (MMSE, network infrastructures that support the MultiMedia Service), other pieces of state data (for example, charging-significant information) are exchanged between MMS Relay Servers. so even though these servers use SMTP as the "bearer" for their application exchanges, they map their internal state to specialised headers carried in the SMTP message exchanges. the headers used in such MMSE are described in detail in [17] 🧠

Security Considerations: there are no specific security issues with this Enumservice 💅 however, the general considerations of Section 6 apply.

Intended Usage: COMMON

Authors: Rudolf Brandner, Lawrence Conroy, Richard Stastny (for author contact detail see Authors' Addresses section) 🎀

Any other information the author deems interesting: the MMS Architecture describes an interface between the MMSE and "legacy messaging systems" (labelled as MM3) that accepts "standard" SMTP messages. so the MMS Relay Server that supports this interface looks like a standard SMTP server from the view of an Internet-based mail server, but it's actually acting as a gateway and translator, adding the internal state data that gets used within and between the MMS Environments. the whole process is described in [17], which also includes references to the specifications agreed by those bodies responsible for the design of the MMS 🌈

6. Security Considerations 🔐

DNS, as used by ENUM, is a global, distributed database. so any information stored there is visible to anyone, anonymously. ngl, this is not qualitatively different from publication in a Telephone Directory, but it does open data subjects up to having "their" information collected automatically without any indication that this has been done or by whom 👀

Such data harvesting by third parties is often used to generate lists of targets for unrequested information. in short, they are used to address "spam". anyone who uses a Web-archived mailing list is aware that the volume of "spam" email they get goes up when they post to the mailing list 😭 publication of a telephone number in ENUM is no different, and may be used to send "junk faxes" or "junk SMS", for example.

Many mailing list users have more than one email address and use "sacrificial" email accounts when posting to such lists, to help filter out unrequested emails sent to them. this is not so easy with published telephone numbers. the PSTN E.164 number assignment process is much more involved, and usually a single E.164 number (or a fixed range of numbers) is associated with each PSTN access. thus, providing a "sacrificial" phone number in any publication is not possible 📵

Due to the implications of publishing data on a globally accessible database, as a principle, data subjects MUST give their explicit informed consent to data being published in ENUM. this one is non-negotiable, bestie 🚨

In addition, they should be made aware that, due to storage of such data during harvesting by third parties, removal of the data from publication will not remove any copies that have been taken. in effect, any publication may be permanent 💀

However, regulations in many regions will require that data subjects can at any time request that the data is removed from publication, and that their consent for its publication is explicitly confirmed at regular intervals. that's the good news 🌷

When placing a fax call via the PSTN or sending a message via the Public Land Mobile Network, the sender may be charged for this action. in both kinds of network, calling or messaging some numbers is more expensive than sending to others. both networks have "premium rate" services that can charge considerably more than a "normal" call or message destination. so it is important that end-users be asked to confirm sending the message, and that the destination number be presented to them. it is the originating user's choice on whether or not to send a message to this destination number, but end-users SHOULD be shown the destination number so that they can make this decision 💸

Although a fax number, like other E.164 numbers, doesn't appear to reveal as much identity information about a user as a name in the format user@host (e.g., an email or SIP address), 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 [18] to these, is provided in RFC 3761 [2]. a thorough analysis of threats to the DNS itself is covered in RFC 3833 [19] 🧐

An email address is a canonical address by which a user is known. placing this address in ENUM is comparable to placing a SIP or H.323 address in the DNS 🪪

DNS does not make any policy decisions about the records that it shares with an inquirer. All DNS records must be assumed to be available to all inquirers at all times. the information provided within an ENUM NAPTR resource record must, therefore, be considered to be open to the public, which is a cause for some privacy considerations 🙈

Therefore, ENUM Subscribers should be made aware of this risk. since it is within the responsibility of the ENUM Subscriber which data is entered in ENUM, it is within the ENUM Subscriber's control if they enter email addresses:

allowing inference of private data, e.g., his first and last name
at all

it should also be considered that it is the purpose of public communication identifiers to be publicly known. to reduce spam and other unwanted communication, other means should be made available, such as incoming message filtering 🛡️

Some Value Added Service Providers use receipt of a short message to a given special service telephone number as a trigger to start delivery of data messages to the calling number. by sending an SMS (or, in principle, an EMS or MMS) to one of these special service numbers, one is entering into a contract to pay for receipt of a set of messages containing information (e.g., news, sports results, "ring tones") 📲

Thus, it is very important that the end terminal presents the destination number to which any message is to be sent using the "sms: tel", "ems:tel", or "mms:tel" Enumservices, to allow the end-user to cancel any message before it is sent to one of these numbers. this is a big deal, so please double-check your terminal 🚫

At present, these systems use the circuit switched network trusted calling line identifier to identify the destination for the subsequent charged information messages. so it is believed that sending using the "sms:mailto", "ems:mailto", or "mms:mailto" Enumservices does not have this risk currently 🌤️

7. Acknowledgements 💌

Many thanks to Ville Warsta for his close reading of the document and extracting the right references 🙌 thanks also to those who are involved in the parallel effort to specify the requirements for "real world" ENUM trials resulting in TS 102 172 [20], in which this and other Enumservices are referenced 💜

8. References ✨

8.1. Normative References 📚

okay the reference list is where the real receipts live 🧾 these are the docs the spec leans on so hard it literally can't stand without them 💅

[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997.
[2] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM)", RFC 3761, April 2004.
[3] ITU-T, "The International Public Telecommunication Number Plan", Recommendation E.164, May 1997.
[4] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", RFC 1034, November 1987.
[5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Three: The Domain Name System (DNS) Database", RFC 3403, October 2002.
[6] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS", RFC 3401, October 2002.
[7] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Two: The Algorithm", RFC 3402, October 2002.
[8] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Four: The Uniform Resource Identifiers (URI)", RFC 3404, October 2002.
[9] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA Assignment Procedures", RFC 3405, October 2002.
[10] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, December 2004.
[11] Hoffman, P., Masinter, L., and J. Zawinski, "The mailto URL scheme", RFC 2368, July 1998.
[12] ITU-T, "Standardization of Group 3 facsimile terminals for document transmission", Recommendation T.4, April 1999.
[13] ITU-T, "Procedures for document facsimile transmission in the general switched telephone network", Recommendation T.30, April 1999.
[14] 3GPP, "Technical realization of the Short Message Service (SMS); (Release5)", 3GPP TS 23.040.
[15] 3GPP, "Multimedia Messaging Service (MMS); Functional description; Stage 2 (Release 5)", 3GPP TS 23.140.
[16] 3GPP, "Multimedia Messaging Service (MMS); Media formats and codecs; (Release 5)", 3GPP TS 26.140.
[17] Gellens, R., "Mapping Between the Multimedia Messaging Service (MMS) and Internet Mail", RFC 4356, January 2006.

8.2. Informative References 🌸

these ones are more like bonus reading, the main plot is above 🫶

[18] Arends, R. and et al. , "Protocol Modifications for the DNS Security Extensions", RFC 4035, March 2005.
[19] Atkins, D. and R. Austein, "Threat Analysis of the Domain Name System (DNS)", RFC 3833, August 2004.
[20] ETSI, "Minimum Requirements for Interoperability of ENUM Implementations", ETSI TS 102 172, January 2005.

Authors' Addresses 🦋

meet the people who wrote this, bestie 🎀

Rudolf Brandner
Siemens AG
Hofmannstr. 51
81359 Munich
Germany

Phone: +49-89-722-51003
EMail: rudolf.brandner@siemens.com


Lawrence Conroy
Siemens Roke Manor Research
Roke Manor
Romsey
United Kingdom

Phone: +44-1794-833666
EMail: lwc@roke.co.uk


Richard Stastny
Oefeg
Postbox 147
1103 Vienna
Austria

Phone: +43-664-420-4100
EMail: Richard.stastny@oefeg.at

Full Copyright Statement ⚖️

the legal bit, but make it cute ✨ The Internet Society owns the copyright here, and it's dated 2006. This document is subject to the rights, licenses and restrictions in BCP 78, and the authors keep all their rights except as BCP 78 says otherwise. 🔒

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The IETF also invites anyone who knows of copyrights, patents, patent applications, or other proprietary rights that might cover technology needed to implement this standard to flag them. Send that info to the IETF at ietf-ipr@ietf.org. 📬

Acknowledgement 🌈

a little shoutout at the very end 🎉 Funding for the RFC Editor function comes from the IETF Administrative Support Activity (IASA). Thank you, IASA, you're the real MVP 👑🧚

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