RFC 5526

The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application for Infrastructure ENUM ✨

okay bestie, this is RFC 5526 🎀 It's an Informational doc from April 2009, so it's giving "here's some useful info for the community," not an official Internet standard. 🤓 The authors are Jason Livingood (Comcast Cable Communications), Penn Pfautz (AT&T), and Richard Stastny (Unaffiliated). The header doesn't list anything it obsoletes or updates, so it's a brand new vibe 🦋

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Status of This Memo 📮

This memo gives info to the Internet community. It doesn't specify an Internet standard of any kind 🙈 Distribution of this memo is unlimited, so share it with everyone you know 💅

Copyright Notice ©️

Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, because they describe your rights and restrictions with respect to this document 📜

Heads up: this document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of that material outside the IETF Standards Process. Without an adequate license from the person(s) controlling the copyright in those materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Not a vibe to ignore 🥺

Abstract ✨

Okay so this doc defines the use case for Infrastructure ENUM 🧚 and proposes building it as a parallel namespace to "e164.arpa", which is defined in RFC 3761. This is the long-term fix for letting carriers provision DNS records for telephone numbers separately from what end users (number assignees) provision. Iconic, right? 👑

Table of Contents 📚

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Zone Apex for Infrastructure ENUM ...............................3
   4. IANA Considerations .............................................3
   5. Security and Privacy Considerations .............................4
   6. Acknowledgements ................................................4
   7. Normative References ............................................4

1. Introduction 🌸

ENUM (E.164 Number Mapping [1]) is a system that turns E.164 numbers [2] into domain names. Then it uses the DNS (Domain Name Service) [3] to find NAPTR records that say what services are available for a specific domain name. Pretty slick, ngl 🫶

Here's the tea 🍵 ENUM, as originally defined, was built on the end-user opt-in principle. That has great potential to unlock new services and end-user choices long term. BUT the current requirements for IP-based interconnection of Voice over IP (VoIP) domains need a bunch of allocated or served (hosted) numbers from a participating service provider to get provisioned, without each individual user having to opt in. 😤 That way, service providers can provision their own ENUM info, which is separate, distinct, and likely to be different from what an end user would provision. This matters a lot if Infrastructure ENUM is used for number-portability stuff, which an end user would probably never bother with but a service provider would find totally essential 💅

Also, sure, service providers could make users opt into e164.arpa through end-user contract terms and conditions. But there are big downsides to that approach 💀 So, for all these reasons and many others, ENUM for end-user provisioning is ill-suited for service providers using it to interconnect VoIP domains. Not it 🙅‍♀️

As VoIP evolves and becomes pervasive, E.164-addressed telephone calls don't necessarily have to go through the Public Switched Telephone Network (PSTN) anymore 🦋 So VoIP service providers are into using ENUM on a so-called "Infrastructure" basis. The goal is to keep VoIP traffic on IP networks end to end, both inside and between service provider domains. To do that, you need a way to identify a VoIP point of interconnection where calls to a given E.164 number can be delivered, and Infrastructure ENUM provides exactly that 🎯 Calls that can start and end on IP networks, without touching the PSTN, need fewer points of transcoding (or none at all), and they can also use extra IP network services that just aren't possible on the PSTN. Main character energy for sure ✨

Requirements for Infrastructure ENUM are provided in [4] 📖

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 [5]. These are the official requirement-level words, so read them carefully bestie 🔍

3. Zone Apex for Infrastructure ENUM 🧚

This document proposes implementing Infrastructure ENUM as a parallel namespace to e164.arpa, dedicated to Infrastructure ENUM, in a domain that is yet to be determined 🔮 Using a parallel namespace lets carriers and end users control their ENUM registrations independently, without one having to go through the other. Independence era 💖

Infrastructure ENUM Tier 2 resource records in the Infrastructure ENUM tree will be controlled by the service provider that's providing services to a given E.164 number. That provider is generally called the "carrier-of-record" in various countries (see [4]). What counts as a carrier-of-record for a given E.164 number is a national matter, or it's defined by the entity controlling the numbering space 🌍

See also Section 3, "Requirements for Infrastructure ENUM", of [4] 📌

4. IANA Considerations 🌈

IANA has created a registry for Enumservices as originally specified in RFC 2916 and revised in RFC 3761. Enumservices registered with IANA are valid for Infrastructure ENUM as well as end-user ENUM. Both sides eat 🍰

5. Security and Privacy Considerations 🔐

Real talk, this part is serious 😭 This document proposes a new zone apex for ENUM to meet the requirements of Infrastructure ENUM. The over-the-network protocol of ENUM stays unchanged by adding an apex, so the Security Considerations of RFC 3761 [1] still apply. Specific considerations about the security of an Infrastructure ENUM apex are covered in more detail in Section 4, "Security Considerations", of [4]. Go read that one 👀

Infrastructure ENUM registrations proposed by this document should resolve to service provider points-of-interconnection, not to end-user equipment. Service providers need to take appropriate measures to protect their end-user customers from unwanted communications, just like they do with other types of interconnections. Protect your people 🫶🛡️

6. Acknowledgements 💜

The authors want to thank Lawrence Conroy, Patrik Faltstrom, Michael Haberler, Otmar Lendl, Steve Lind, Alexander Mayrhofer, Jim Reid, and Richard Shockey for their helpful discussions of this document and the concept of Infrastructure ENUM. Thank you, queens 👑

7. 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 Number Plan",
    Recommendation E.164, February 2005.

[3] Mockapetris, P., "Domain names - concepts and facilities", STD
    13, RFC 1034, November 1987.

[4] Lind, S. and P. Pfautz, "Infrastructure ENUM Requirements", RFC
    5067, November 2007.

[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
    Levels", BCP 14, RFC 2119, March 1997.

Authors' Addresses 💌

Jason Livingood
Comcast Cable Communications
1500 Market Street
Philadelphia, PA 19102
USA

Phone: +1-215-981-7813
EMail: jason_livingood@cable.comcast.com


Penn Pfautz
AT&T
200 S. Laurel Ave
Middletown, NJ  07748
USA

Phone: +1-732-420-4962
EMail: ppfautz@att.com


Richard Stastny
Anzbachgasse 43
1140 Vienna
Austria

Phone: +43-664-420-4100
EMail: richard.stastny@gmail.com

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That's the whole RFC, bestie 🌈✨ Infrastructure ENUM is basically VoIP keeping its calls on IP networks while carriers manage their own number records 💖