Operational Requirements for ENUM-Based Softswitch Use
RFC 5346
Network Working Group J. Lim
Request for Comments: 5346 W. Kim
Category: Informational C. Park
NIDA
L. Conroy
RMRL
October 2008
Operational Requirements for ENUM-Based Softswitch Use
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Abstract
This document describes experiences of operational requirements and
several considerations for ENUM-based softswitches concerning call
routing between two Korean Voice over IP (VoIP) carriers, gained
during the ENUM pre-commercial trial hosted by the National Internet
Development Agency of Korea (NIDA) in 2006.
These experiences show that an interim solution can maintain the
stability of ongoing commercial softswitch system operations during
the initial stage of ENUM service, where the DNS does not have
sufficient data for the majority of calls.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Call Routing on Softswitch . . . . . . . . . . . . . . . . . . 2
3. Infrastructure ENUM Trial in Korea . . . . . . . . . . . . . . 3
4. Operational Requirements for ENUM-Based Softswitches . . . . . 4
4.1. Call Routing Cases for DNS Response Codes . . . . . . . . 4
4.1.1. Trial Policies . . . . . . . . . . . . . . . . . . . . 4
4.1.2. Trial ENUM Lookup Rules . . . . . . . . . . . . . . . 6
4.2. Call Routing Cases for Domainparts . . . . . . . . . . . . 7
5. Trial Results . . . . . . . . . . . . . . . . . . . . . . . . 9
6. 'e164.arpa' Considerations . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Lim, et al. Informational [Page 1]
RFC 5346 Enum-Based Softswitch Use October 2008
1. Introduction
ENUM [RFC3761] is a mapping system based on DNS [RFC1034] [RFC1035]
that converts from an E.164 [E164] number to a domain name using the
Naming Authority Pointer (NAPTR) [RFC3403] resource record type.
ENUM is able to store different service types (such as fax, email,
homepage, SIP, H.323 and so on) for every E.164 number. It
originally focused on how end-users could gain access to other end-
users' communication contact information through the Internet.
Recently, discussion on the need to update RFC 3761 has begun to
ensure that the standard also works in the "Infrastructure ENUM"
scenario, where ENUM provides routing information between carriers.
This resulted in two documents, the updated ENUM specification
[RFC3761bis] and an Enumservice guide [ENUMSERVICE-GUIDE].
When providing VoIP service, a VoIP carrier that wants to integrate
various protocols typically uses a softswitch. However, such a
system is still inefficient for interconnection, number portability,
and sharing protocol support information among carriers, because each
softswitch does not have complete end-to-end routing information for
all carriers. This information can be stored in DNS, using ENUM.
Therefore, carriers can expect to gain many advantages if they use
ENUM within the call routing functions of their softswitches.
To confirm these benefits and to verify the performance of ENUM-
enabled softswitches, NIDA cooperated with two Korean VoIP service
providers for an Infrastructure ENUM trial in 2006. NIDA is a non-
profit organization with a mandate to manage 2.8.e164.arpa.
(representing the +82 country code of Korea). NIDA promotes and
facilitates technical cooperation on a national scale between
partners, and this includes ENUM. During the trial, NIDA provided a
centralized ENUM DNS to each VoIP service provider for call routing.
The data used in this Infrastructure trial was also accessible to the
public (i.e., it was an Internet-based system, rather than a closed
scheme).
2. Call Routing on Softswitch
In the PSTN (Public Switched Telephone Network), hardware-based
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