Telephone Number Mapping

ENUM stands for " E.164 NUmber mapping " and is an application of the Domain Name System to translate telephone numbers into Internet addresses. ENUM is defined in RFC 6116. The need for such a solution arose from the availability of VoIP services (telephone via the Internet) and the needs of the user, both on the Internet as well as in the classic telephone network to be reached under the same number. So it is the declared goal of service developers, all the services that are available can be made available in the future, under a central Internet address (domain ) make available available on the internet or. In fact, however, is the free phone routing, in which a VoIP subscriber under a landline number to another VoIP user directly (ie, bypassing the network provider and therefore less " free " ) can achieve the main use because of the ENUM services.

• 6.1 Alternative services to ENUM

• 7.1 For more information
• 7.2 registries ( registries )
• 7.3 VoIP providers list
• 7.4 Other free ENUM zones ( registries )

Basic Ways of ENUM

The basic goal of ENUM is the resolution ( conversion ) of a classic telephone number in a target name under which, is available to a service on the Internet, for example an Internet phone. For example, the telephone number " 123456789 " be dissolved or converted by an ENUM lookup in the destination name " [email protected] " an Internet phone. In this case, the telephone call is not established after the election of a landline number by the network provider of the participants, but by the devices of the participants themselves, the name " [email protected] " can in principle refer to both a registered phone on the internet, as well as an e - mail address or other services. In this example, an e- mail server is allowed to dissolve an e -mail address by ENUM ( eg pop3: [email protected] ) the entry during an ENUM -capable phone " SIP: [email protected] " processed. There are some providers of complete solutions (DSL, e- mail, phone) that provide such addresses for both e- mail and VoIP services. Ie, they differ only by the protocol used ( mail, phone, other) from each other. Since email addresses are already known in general, there is usually no explicit reason to send e -mails via ENUM -enabled systems.

With ENUM, it is also possible to achieve over the internet both Internet phones, as well as call landline phones and mobile devices, provided at a uniform number several such connections are configured. The actual accessibility configured the connection owner according to established priorities. For example, an ENUM -enabled phone number ( landline, mobile, special number, international, etc.) are configured to first try to reach an Internet phone. If this is not registered with the VoIP provider, a wireless connection is established. If the phone is not registered on the network, the call is forwarded to a landline. The caller is calculated normally the service configured, regardless of whether he has chosen a landline or mobile phone number. Whether the caller or ENUM uses instead an internet phone using the Internet name " [email protected] " calling directly, that is only matter if the target is an internet connection anyway.

It should be noted that so far only a few VoIP telephone numbers are registered. How are telephone numbers that are not registered, by its own service providers as usual on the mandatory telephone gateway ( network gateway ) conducted the telephone network operator to reach the subscriber as usual via the fixed network (PSTN). In the case of an ENUM registration landlines and mobile phones can indeed be ENUM ( and thus from the Internet ) is reached, but must actually continue to be routed via landline or mobile network, unless it is additionally also access the Internet. Although some mobile devices can be configured for Internet telephony, but it is on the network operator if he needed the VoIP protocol (mostly SIP Protocol ) routes or seller mutually blocked.

ENUM and worldwide telephone numbers

Since telephone numbers are created according to country-specific dial plans, they must be integrated in an international format to the global Internet. Here they follow a numbering plan of the International Telecommunication Union ( ITU), which is defined in the Recommendation E.164. Since it is in the ENUM mapping ( mapping) worldwide phone numbers is an Internet resource, as opposed to the phone numbers themselves, which can be considered as a resource under the management of the ITU, but the classic top -level domain was for Internet resources of the Internet Engineering Task Force (IETF ). arpa used. A subdomain was - as it is mapping of E.164 numbering plan - e164 selected. Since ENUM mappings are ultimately nothing more than a simple DNS records, but it is so of course also possible to map its own numbering plans, among other domains.

Implementation and query

The implementation of a telephone number in the corresponding ENUM domain (in this case, the IETF mapping) is done as follows:

This conversion happens automatically in most ENUM - enabled devices so that only is to enter the phone number required. Knowledge of the exact domain plan are therefore neither necessary nor for the caller for the participants, configure a custom ENUM server.

The results from the above implementation of the Domain Name will be searched by the resolver after NAPTR resource records. The evaluation of these resource records results in one or more Uniform Resource Identifier, under the / which the desired service of the specified domain or telephone number can be addressed.

Administration

The international ENUM top level domain e164.arpa is currently administered on behalf of the ITU of Réseaux IP Européens ( RIPE ). At the request of the individual country codes are delegated after consultation with representatives of the ITU to local country organizations. The further design of the national domain space is autonomously determined by the national organization, and this is usually done in close cooperation with the national competent authority.

The allocation and connection of these new domain name has been tested since the beginning of 2002 in some countries in the so-called ENUM Trials. These trials are usually the exploration of ENUM and related technologies as well as the preparation of a possible commercial operation.

In Germany ENUM records under 9.4.e164.arpa are available at some of DENIC - Members as part of the experiment since 2002. The transition to live operation was originally scheduled for December 2005, but was finally taken only on 26 January 2006.

As the world's first country to contract for the commercial operation of ENUM in Austria was signed after a two -year test on 24 August 2004. In this Agreement, the Austrian regulator, Rundfunk und Telekom GmbH delegated regulation ( RTR ), the operation limited until the end of 2007 enum.at. The production plant was taken by enum.at on 9 December 2004.

Expiration

Technical and organizational conditions for the use of ENUM

If you call with an ENUM look-up device, or via a provider of ENUM look-up support, a telephone number, then asks this terminal or the provider using the ENUM domain from the target. Is there an ENUM domain and is another target deposited deposited, eg, VoIP destination, mobile number or landline number, this is preferred for the connection. Also, several targets are deposited that are queried according to priority. Otherwise, the specified telephone number is called. Furthermore, it may also deposited an email address or a website.

To register to a German phone number ENUM domain, several conditions must be met:

• The phone number must be a corresponding German numbering plan have.
• Possess the registrant of ENUM domains has the right to use the number.
• The phone number must originate in Germany an available for ENUM number range: local networks
• Mobile 015, 016, 017
• Freephone 0800
• Personal numbers 0700
• National subscriber numbers (NTR, nomadic use of VoIP) 032

It is not necessary, that its own Gateway and this number is connected to the telephone network. In order to still be accessible over the telephone network, must from the telephone network operator transitional interfaces ( gateways ) to be installed, dominate the ENUM.

In Austria the following number ranges for use are provided with ENUM:

• Geographic numbers
• Telephone numbers for private networks ( 05 ..)
• Mobile numbers ( 0664, 0676, 0699, 0650, 0660 ... )
• Location-independent landline numbers ( 0720 )
• Numbers for convergent services ( 0780 )
• Numbers in the range 0800

A link to an existing telephone number is performed by a registrar. The registrar checks every six months, whether the associated phone number is still current.

Additional costs, which occur by diverting via ENUM, the caller pays. Example: You have chosen a landline number, but by the ENUM lookup a cell phone number or even premium rate number (0900, formerly 0190) routed. But: Since the ENUM lookup is performed on the user side, it is up to the hardware and software of the user, whether such forwarding without notice to the user is performed. ENUM "distributed" only the information which is made ​​of it, is located on the user and its hardware and software.

ENUM and traditional telephone routing between VoIP and landline customers

The most common use of ENUM is the direct call between two communication partners using ENUM to reach using a normal phone number one party directly, bypassing the usual telephone networks, and usually also to save you cost.

• Dark gray are the caller, light gray are the called destination subscriber.
• Light Blue have subscribed Internet or VoIP telephony ( in the examples, a commonly used universal SIP protocol is used), in magenta participants with landline telephony. There are also other protocols besides SIP usable, the usefulness depends on the support area on the subscriber side and on the supplier side.
• Broken lines are the data queries: Resolution of the phone number in a SIP target (thick line) Resolution of the SIP name to IP address of the Internet phone Solid lines are the phone calls
• The numbers in the same colors indicate the order when establishing a connection to

Caller 1 has an ENUM -enabled device ( phone or SIP adapter) and can after dialing a phone number itself requests to the SIP server filters ( Route 1 blue for all compounds ), which resolves those phone numbers into a SIP address there have been configured by the participants before. Only when the SIP server of the target subscriber is reachable in fact under the resolved SIP address, a telephone connection is possible, otherwise must be telephoned about the phone number.

• Way to subscriber B: The phone or SIP Adapter of caller 1 to send a request to the ENUM server (path 1 blue, server is brown), which resolves the phone number in a SIP destination ( ie converts ). About the SIP destination is the SIP server (orange) distance ( path 2 blue) who knows and answers the current IP address of the subscriber. ( The current IP address of the node refers to the SIP server from the terminal of the user at every logon or reconnect the DSL router again.) Only with this IP address is a direct connection between the two parties is established (path 3 blue). If the ENUM server configured incorrectly, the calling device can not obtain an IP address from the SIP server and not reach the subscriber. If the caller aware of the SIP goal and he can dial it directly, then the resolution of the phone number on ENUM ( step 1) omitted. Alternatively, callers 1 subscriber directly via the SIP address to call (eg if ENUM is configured incorrectly, step 1 blue omitted) if they know the SIP address of his interlocutor, or it can dial the phone number without ENUM lookup to the conversation to lead via the telephone network (paths 2b/2c blue, 3 red). In this case, the provider of subscriber B has an internal SIP request (path 4 red), because the target participants in each case only through the Internet ( VoIP) is achievable.

• Way to subscriber A: The SIP server of provider A does not respond to external requests. An ENUM query (path 1 blue) is therefore possible, but pointless. Therefore, the caller must be using the normal telephone landline number on his VoIP provider ( alternative route 2b blue establish a connection via the telephone network (pathway 2c blue ), his VoIP provider chooses the path to VoIP or phone provider of the target subscriber (path 3 red). This provider controlled internal network, the telephone network or the Internet will be, will be routed to the landline rates. The VoIP provider of subscriber A sends a request to its own internal SIP server (path 4 red at target subscriber A), the only answer to these internal requests and forwards the call to the so- resolved IP address on (Route 5 red) that remains hidden from the device of the caller.

• Way to subscriber C: Participant C has a fixed line. A possible ENUM query (path 1 blue) remains inconclusive. The call is routed as in subscriber A to the provider 's internal network (paths 2b/2c blue) and the provider of the participant C directly to its fixed line ( path 3 magenta).

2 caller does not have ENUM -enabled device, but a VoIP provider that provides ENUM queries, ie his device is in any case a connection via your own VoIP provider ago (path 1, green for all connections ). This provider now provides an ENUM query (path 2 green )

• Way to subscriber C: The VoIP provider of the caller 2 is replaced by the ENUM server (path 2 green ) a SIP address back. The VoIP provider the caller is now using SIP address a request to the SIP server of the destination subscriber B ( Route 3 green) and obtains the IP address of the subscriber. The VoIP provider for the caller builds a direct connection to the destination subscriber (path 4 green) and to turn on mediating between caller and 2 target subscriber C. If (green path 2) no entry is found in the ENUM query, it is up to the provider what way he chooses. If an ENUM entry present but incorrectly configured, caller 2 can not reach the target participants in general. His provider adheres to the priority settings suggested to it the ENUM server. If the target subscriber only temporarily accessible via the Internet, he can in the ENUM server a second subordinated way for the dial-up deposit, for example, over the telephone network (route 3 red). All participants (A, B and C) are reachable via the telephone network ( alternative route 2b / c, green, then through the gateway from the Internet to the internal network provider, 3 way red / magenta).

• Way to subscriber A: Although participant A is also accessible via the Internet (path 2b / c green), but only through the gateway of the VoIP provider (path 3 red to A), because the SIP server responds only provider internal requests ( 4 way red).

• Way to subscriber C: Participant C is only accessible via the telephone network (path 2b / c green and after the gateway from the Internet to the telephone network path 4 magenta)

Callers who call from the PSTN have, except via Call -by-call, no influence, in what way and at what rates they reach a target subscriber. The call is routed via the provider 's internal network (path 1 2 magenta) to target nodes ( paths 3 red or magenta) Here, the routing is managed solely by the participating telephone companies, even if an Internet phone (VoIP in participants A and B, red) is called.

Current market acceptance

The number of registered German numbers stagnated since December 2006, approximately 8,000 (as of Sept. 2011). Avoid Many German VoIP provider ENUM, so that customers can make calls free of charge via their landline gateways. Many VoIP providers block even all VoIP calls from other providers, so that the customer will charge the phone and reached via the fixed network. With the flat rate VoIP providers earn additional to the incoming landline calls. So far, only a few VoIP providers provide the opportunity to reach Internet users on ENUM look- ups, but still no phone network operator. Call-by- call providers might in the future seek to cut through ENUM look- ups own expense, in which it cheaper to produce in mixed costing individual compounds. Here, however, they have to face the initial investment in the new technology which is currently still low cost advantage ( by the few ENUM -enabled numbers).

Market providers that offer ENUM services that require differentiated business models for their economic success. For example, some VoIP providers advertise on their websites with cheap line rental and free ENUM -mediated talks, but earn on the other landline, mobile and international calls. Other vendors offer a free VoIP connection and lower rates, but market the fixed telephone number of the customer separately. The latter can take advantage of customers, perform in-depth discussions on the number of a DSL provider and outgoing calls through a separate port. Customers using ENUM services often do so for reasons of cost reduction, so that in the future no -cost marketing and advertising campaigns are to be expected.

Market participants who are interested in ENUM services that require a sophisticated awareness of the possibilities and advantages associated with ENUM available. Thus, for the own benefits mainly due to the fact that as many other telephone customers, or at least their own interlocutors to participate in this system also. Before ENUM services achieve a breakthrough in the mass market, it is in the interest of interested customers, to potential future users virtually to contact " in advance " to use the services in the future even can. For this purpose the DENIC provides the registration of ENUM -enabled landline numbers, at least in Germany are still free and most registrars provide this cost advantage currently to the end customers, so except for the time are no additional costs for setting up the service. If the service charge, tariffs are to be expected, which is expected as the prices of websites forwarding domains correspond, so some euros annually or cents a month.

Alternative services to ENUM

In the field of internet telephony between two VoIP subscribers direct dialing from a VoIP adapter or a so-called softphone ( VoIP-enabled telephone software) is a viable alternative. However, a prerequisite is that the caller of the Internet name of the destination port is known and (usually a SIP server ) answered the VoIP server of the called external customer inquiries. Many SIP servers respond to external incoming requests, however, the associated phone numbers are often not ENUM enabled. If a provider SIP requests not answered, but no ENUM configuration of the IP phone and thus no direct connection is possible because the IP address of the VoIP station is always usually replaced.

Should a phone customer, only the individual configuration of its various terminals, for the conveyance of telephone calls from a single phone number on different terminals, can be installed as previously usual a second telephone line and a telephone system. There are also phone providers that allow you to configure call forwarding on the supply side, for which no second phone line and special equipment is required on the client side. In this case arise for forwarding costs, even with existing telephone flatrate. For these configurations, however, it is also irrelevant uses which telephone service the caller.