ENUM Report · 2015-10-05 · of ENUM and is indeed difficult to come up with a good answer. Most probably, ENUM will initially be used for simple E.164 number to SIP address mapping

Norid report Page 1 (16)

Authors: Jakob Fredriksson & Jakob Schlyter (Guide) GUIDE/NOS/NORID-ENUM-2/REPORT/001Approved: Hilde Thunem 2003-10-20 Rev. B Reference:

This report is a subset of a complete ENUM report that was originally produced forNorid by Jakob Fredriksson & Jakob Schlyter, Guide Konsult Göteborg AB.

This subset contains information that is assumed to be useful for anyone interested inENUM in Norway. Among other things, it describes relevant areas of work if a moreextensive field test should follow from the current test project.

ENUM Report

Authors:Jakob Fredriksson & Jakob Schlyter (Guide)

Copyright © 2003, UNINETT Norid AS

Guide Konsult Göteborg ABOlof Asklunds gata 10SE-421 30 Västra FrölundaSwedenTelephone +46 31 709 59 00url: http://www.guide.se



Contents

1Introduction........................................................................................................................32The Model of ENUM.........................................................................................................4

2.1ENUM Roles...............................................................................................................42.2Organizing ENUM......................................................................................................4

2.2.1One ENUM Registry............................................................................................52.2.2ENUM Registry Tasks.........................................................................................62.2.3Validation.............................................................................................................62.2.4Organizing Competition.......................................................................................72.2.5Organizing Registrars..........................................................................................72.2.6Supervision..........................................................................................................7

3The ENUM Framework.....................................................................................................73.1The Market for ENUM...............................................................................................7

3.1.1ENUM Customers and Users...............................................................................73.1.2Amount of ENUM Users.....................................................................................83.1.3ENUM Registry Customers.................................................................................93.1.4A Fair Competition..............................................................................................9

3.2Liabilities and Regulations........................................................................................103.3Relations to E.164 Actors.........................................................................................113.4Business Models and Payment Schemes..................................................................11

3.4.1The Value of ENUM for the End Users.............................................................113.4.2Termination Fees...............................................................................................113.4.3The Costs of ENUM..........................................................................................123.4.4Conclusions and Recommendations..................................................................14

3.5Security Considerations............................................................................................154References........................................................................................................................16



1 Introduction

ENUM is best described as a protocol and a database enabling a service which translatesan E.164 (PSTN) number to a URI (Uniform Resource Identifier). A URI canpoint to various types of resources such as a mail address (mailto:[email protected]),a web page (http://www.example.com/) or a SIP address (sip:[email protected]).The purpose is that, if you know a person’s normal telephone number (the E.164number), you should be able to look up the ways in which you can communicate withthis person. This enables various ways of communication, but the focus has beenon services that enables voice communication over the Internet (VoIP). One of theprotocols enabling such services are SIP (Session Initiation Protocol).

Even though ENUM services are fairly small in scope and easy to implement intoan existing DNS service, it is a topic that arises a lot of questions and is believed tohave a large impact on the cost-benefit calculations for the competitors on the PSTNmarket. This leaves us with a difficult problem regarding strong actors and low levelon knowledge regarding ENUM.

ENUM is defined in RFC 2916 and is revised in a Internet draft also known as2916bis. The relationship between IETF and ITU was resolved at ITU-T WorkingParty 1/2 meeting held in Berlin, 19-26 October 2000 (the liaison is documented inLiaison to IETF/ISOC on ENUM [WP1-2] and RFC3026 [RFC3026]).

ENUM isn’t necessarily about telephone communication over the Internet. This isa common misconception often heard from the telecom industry and leads to themisunderstanding that telecom industry will loose profits if ENUM is implemented.ENUM is just a database and a specification of how to get the data in the database.The only formal connection between the telecom industry and ENUM is that ENUMutilizes the E.164 number plan. If ENUM hadn’t used that number plan, it would havebeen a matter only for the Internet community. But, since the E.164 number plan waschosen the telecom industry and all its regulations must be taken into account.

Many people ask what application that would be envisioned as the killer applicationof ENUM and is indeed difficult to come up with a good answer. Most probably,ENUM will initially be used for simple E.164 number to SIP address mapping forVoIP or E.164 number to email address mapping for SMS/MMS. As the usage ofENUM increases and the comprehension of how ENUM can be used grows, otherapplications will join the simple, but yet very useful, voice application.



2 The Model of ENUM

2.1 ENUM RolesThe main roles of ENUM are:

Registry The entity that is responsible for operating ENUM in a country and have receivedthe delegation of the ENUM domain corresponding to the E.164 countrycode (for Norway .7.4.e164.arpa) from RIPE NCC (evaluation and approval ismade by ITU-T TSB). The registry ensures that reference is made to the serversin which the ENUM information is located.

Registrar The party who manages the registrant´s access information and ensuresthat it is publicly available on the Internet.

Registrant The registrant is the person who makes his access information availableto others through ENUM.

DNS Provider The actor that operates the servers on which the ENUM informationis stored and made available to the public. The actual ENUM information isstored in DNS using NAPTR records.

The government It is only a country’s representative in ITU-T that can request adelegation of the ENUM domain to the country’s ENUM registry. The governmentmight want to be involved in ENUM of several reasons, mainly basedon the fact that telephony is a very important service to the public and thatvoice over IP applications (VoIP, IP telephony) is regarded as the killer applicationfor ENUM implementations. Norway’s representative in ITU-T is Postogteletilsynet (www.npt.no).

Other actors with a direct interest in ENUM can be the number holders that have beenauthorized to hold a part of the country’s number plan for their customers. They willperhaps be involved regarding the issue of who owns a number and the authorizationof the registrant. The issue is made even more complex by the fact that a numberportability scheme has been adopted. The issue of who actually owns a number is agreat challenge to be resolved.

2.2 Organizing ENUMSince ENUM data is offered through DNS, it is tempting to state that ENUM shouldbe organized in the same manner as the ccTLD and the subdomains are organized.Unfortunately, this is to simplify the reality too much. ENUM is not only aboutproviding a database for access information, but will affect the communication marketsubstantially. Depending on how ENUM will be used different issues stands out, butthe following is a list of the most important issues:

Operation The operation of ENUM is decisive and should be conducted as to satisfythe requirements of the users of ENUM. This might seem to be an obviousstatement, but rises several important questions:



Should the administration of ENUM be designed to fit the telecom industry’s currentprocedures regarding billing, registration, subscription, etc?

Should ENUM be organized as to promote cooperation with current usages of means forcommunication, or should it be structured as to promote creation of new technologiesand applications? The problem becomes practical if ENUM should be organized to fitcurrent applications and perhaps divided into one range for fixed telephony and anotherfor mobile phones.

Competition The purpose of promoting competition could be twofold: robustnessof services and adequate prices.

Security ENUM depend on the quality of ENUM services (robustness, performance,etc.) and the level of security.

Cost and benefits ENUM could be considered as a resource for the society as awhole, in the same manner as infrastructure is considered to be.

Regulations Depending on how ENUM is organized, different measures (regulations,supervision requirements, etc.) must be taken to ensure that the goalsof ENUM are fulfilled of all parts that compose the ENUM implementation inNorway.

2.2.1 One ENUM RegistryAs might be understood from this section’s heading, we believe that there should bebut one ENUM registry. Apart from that we believe that the organization of ccTLD’sin Norway (and their subdomains) also would fit ENUM in Norway, we find reasonsfor a single registry when investigating cost, competence, quality and administrativeissues.

Since the usage of ENUM is to be defined by emerging technologies it is utterlyimportant for the organization of ENUM not to thwart any usage of ENUM so thebusiness opportunities can be made profitable. The organization of DNS have provento be efficient in not preventing business opportunities that where unforeseen. DNShave also scaled far beyond it’s original design in respect of size and usage. We believethat this are very good reasons to implement a similar organization for ENUM.

The implementation of DNS in Norway have today a reliable and thorough testedorganization which have been accepted by and earned respect from all DNS actors(ISP’s, DNS operators, registry, registrars, registrants). Supervision procedures andregulations are being revised and modernized. ENUM should be organized to takeadvantage of the experience from the organization of DNS, and can be organized ina similar way. The only aspect that differs is that ENUM needs different means forvalidation of the applicant. The validation can however be defined as an independentprocedure in the organization of ENUM, with a well defined interface toward theother parts of the ENUM organization. This render it possible to organize ENUM isa way that are similar to DNS, and to take advantage of the experience that have beenaggregated over the years.

We believe that the cost of having several ENUM registries would be larger than havinga monopoly. The tasks are (or can be) very strictly defined so there are not much



to gain from having competition between different registries. Even more, the definitionof ENUM as a database incorporated in DNS makes it impossible to implementtrue competition since there cannot be two registry’s that answers questions about thesame ENUM record (the ENUM representation of the E.164 number). In the case ofseveral registry’s, the ENUM namespace had to be divided for each of the registry’s.This would lead to implications regarding how such division should be done, andcould affect the pace at what emerging technologies and new applications could useENUM.

Several ENUM registries does not guarantee that the quality of the ENUM registryservices are kept at the same level. It will also be harder and more costly to superviseand handle complaints.

Accreditation of registrars, the administration of agreements, delegation procedures,self-supervision, and other administrative tasks would be more costly with severalENUM registries than it would be with a single one.

To conclude: There are no benefits from implementing competition at the ENUM registry level. It

would even be more costly and the quality of ENUM services would suffer. Several ENUM registries should lead to a complicated organization that might even

oppose the emergence of new applications that uses ENUM. Several administrative tasks would be more costly to perform in the case of several

ENUM registries.

We strongly recommends that ENUM is organized with a single registry.

2.2.2 ENUM Registry Tasks

The following items is a list of the ENUM registry tasks.

DNS functions The registry provides zone files for the domain 7.4.e164.arpa. It isimportant to understand that the registry is not a distribution mechanism, but aprovider of zone files.

Registry services The registry offers registry services to ENUM registrars and DNSoperators.

Information The registry informs the ENUM actors about rules, regulations andadministrative procedures used to manage the registry. The registry also keepsinformation about the requirements put on the registrars publicly available.

Competition The registry manages and develops its organization is such way that allENUM actors receives fair treatment.

Accreditation of registrars The registry accredits ENUM registrars through registraragreements.

2.2.3 ValidationWe believe that validation of ENUM registrations and other changes of the ENUM



databases should be put on the registrars (and partly on the DNS operators). Thismitigates the administrative effort needed to perform validation of requests. Thiswill however put requirements on the relation between the registrar and the registry.The registry must be able to trust that the registrar has performed the validation in atrustworthy way.

The ENUM actors and potential actors must be involved in the planning of the validationprocedures, since it might inflict upon their calculations of how profitable certainbusiness opportunities are. We recommend that this issue is resolved as a part of afield test.

2.2.4 Organizing CompetitionAs described in section 3.1.4, competition is organized (promoted) through an agreement.Since this is enough for the DNS registrar market, it should be enough for theENUM market as well.

2.2.5 Organizing RegistrarsThe ENUM Registrars should be organized and controlled through registrar agreements.The registrars must conclude that agreement with the registry before they areaccredited as ENUM Registrars.

.no is using these kind of agreements today to organize and control DNS registrars(see Registraravtale [REGAVTALE]). This agreement need to be revised to be usefulin the ENUM case, but is a very good starting point. We recommend that the currentregistrar agreement is copied and revised to be useful in the ENUM organization. Wealso recommend that the agreement is tested during a field test of ENUM.

We have no recommendation today as to what the agreement should contain, but itshould at least regulate the DNS issues and how validation should be conducted (sothe registry can be assured that it is done in a trustworthy manner).

2.2.6 SupervisionAs well as the organization and management of the domain .no, the organization andmanagement of the ENUM domain 7.4.e164.arpa need supervision. The organizationand management of the registry for .no is supervised by PT. The same would beappropriate for ENUM since ENUM render access to communication informationpossible.

3 The ENUM Framework

3.1 The Market for ENUMThis section defines and discusses the actors that must be a part of the ENUM workand the actors that have an interest in the ENUM work (or non-work). It also discussesthe customers to the ENUM registry and how to promote fair competition betweenthem. Finally it estimates the usage of ENUM in Norway.

3.1.1 ENUM Customers and UsersIt is not obvious who the customers and users of access information derived from anENUM database (NAPTR records) are. The person making the call might not even be



aware of the fact that ENUM is utilized to obtain the necessary information to reachthe called person. This is the fact for PSTN (the normal telephone network) callswhere routing information etc. is derived from a source of information that almost noend users of telephones are aware of.

Whether the end user is the customer and/or user of ENUM is a matter of how thenumber plan and the number portability plan is implemented. The end users areprobably the same as the subscribers of a telephone line (and number) and in a sensethe user of access information derived from an ENUM database.

The “natural” user of access information derived from ENUM is the applicationsin need of it. The entity that offers the services that such applications uses wouldtherefore be the users of ENUM.

The customer of ENUM is the entity providing the end user with a “package” ofservices, of which the services of ENUM might be a part. IP telephony, often putforward as the killer application for ENUM, might be a service utilizing ENUM toprovide telephony services to the public.

The provider of the applications that derive access information from the ENUMdatabases is the “natural” customer of ENUM. Such providers might be the currentproviders of telephony or Internet services. The user of ENUM is probably not theend user, but it is information about and originating from the end user that will com-pose the ENUM database. The providers of applications using ENUM will perhapsuse ENUM to offer added value to their services. Regarding telephony, it could forexample be redirection of incoming calls to the preferred application (mobile phone,stationary phone, etc.) in an order set by the end user.

As you probably have understood at this point, the term “user” not very useful in theENUM framework and we define it as the end user of the access information derivedfrom an ENUM database.

The term “customer” is mostly applicable when discussing billing. The end user isoften the customer of a customer of ENUM services. For larger implementationshowever this is not the case. A large company or organization might want to runits own ENUM services to be able to take full advantage of ENUM. Thus, the customerof ENUM is the entity providing the user with services or applications utilizingENUM.

3.1.2 Amount of ENUM UsersThe amount of ENUM users is hard to estimate and depend on several issues:

Larger organizations’ and companys’ need for improved or new access applications. The cost of administering PBX/PSTN telephones at larger installations. Some Swedish

organizations have already seen the possible efficiency gain by limiting the need forcompetence to one area: IP networking. By moving toward using IP telephony their needfor resources regarding PBX/PSTN is eliminated and the IT departments skills can beutilized instead.

How and at what scale the deployment of broadband VoIP telephony is implemented.



Norwegian telephone customers seems to be rather apt to adopt new means of makingtheir telephone bills a bit smaller. According to Post- og teletilsynet’s (PT) compilationof telecom market statistics of the first 6 months of year 2002 [TELESTAT2002],the introduction of carrier preselection was a success. Almost 25% of the fixed networktelephone customers chose carrier preselection during the first years (1998-2001). Some 25% of them have returned to Telenor since. The figures are not importantas such, but shows us that Norwegian people are interested in opportunities andperhaps even new technologies.

Even though the public seems to be apt to adopt the concept of carrier preselection,it is a larger step to convert to using IP telephony. In the short term it is very hardto estimate the public’s interest in applications using ENUM, but in the long term webelieve that ENUM will be a part of almost all access applications. The amount ofusers will then consequently be almost all persons that hold some means of communication.

Even though an estimation of ENUM users amongst the public is far fetched, thefollowing show that the amount of users can be very large. If about 5% of the fixednetwork telephone customers would move toward using IP telephony when introduced,that would result in about 120.000 users of ENUM services. This figures arealso unimportant since they depend on how the telecom market offers ENUM servicesand at what price level such offerings would be.

The number of users that reside within organizations and companies is more meaningfulto estimate. In Sweden the interest of IP telephony services and applicationsincreases every time the companys’ or organizations’ PBX is to be updated or replaced.One example is Stockholm University that are in progress to migrate itsabout 6000 extensions to VoIP using ENUM. This example shows that the amount ofENUM users will increase in a rather abrupt way, when whole organizations are deployingENUM. However, the amount of customers for the registry has increased bya single entity. We believe that a field test of ENUM, that we recommend should beconducted prior to public deployment, should contain activities that asks the marketand potential users if they find ENUM useful and interesting. Any other estimationsare pointless.

3.1.3 ENUM Registry CustomersAs we have defined earlier in this report, the registry only has two types of customers:the registrars and the DNS operators. The number of registry customers will thereforein both long and short term be few.

3.1.4 A Fair CompetitionFirstly we would like to point out that the Norwegian telecom and Internet market isdominated by a single actor: Telenor. Telenor holds (according to PT’s statistics onthe telecom market in Norway [TELESTAT2002]):

about 75% of the market for fixed network telephones, about 60% of the market for mobile phones, 100% of the market for analog leased lines, about 50% of the Internet service provider market (60% of the broadband market, and

30% of the cable modems).

It is only in the cable modems market that a competitor comes even close to the same



market share as Telenor. UPC holds 60% of the cable modems market.

The dominant position of Telenor might lead to difficulties regarding developing practicesfor ENUM promoting the ENUM service and not some old legacy of the telecommarket. It will be very interesting to follow how PT’s project “SMP (Markedsanalyser)”will be received by the market.

As we propose to organize ENUM in Norway, it is amongst the registrars and DNSproviders that competition will take place. But, since the market for telecom in Norwayis dominated by a single company, the organization of ENUM might prove to beof no significance for creating a fair competition on the markets that will use ENUMin Norway.

However, what can be done should be done. The regulations that apply in the DNSmarket in Norway seems to us as a good model for regulating ENUM as well. Aswe have stated before: ENUM is information through DNS. We recommend that itis tested if the regulations that apply to the DNS market today would work for anENUM market as well. This test should be conducted as a part of an ENUM trialperiod.

3.2 Liabilities and RegulationsCommunication security and telecommunication security has attracted attention inNorway lately. The new “Nasjonal sikkerhetsmyndigheten” (NSM) that were establishedat the beginning of 2003 is a direct consequence of the new “Sikkerhetsloven”.PT has been given (by the “Stortinget”) the responsibility to create rules and regulationsfor electronic communication.

These are but two examples of important actors and work in progress. During anENUM field test, a commitment must be made to do a thorough investigation regardingregulations and liabilities, as well as the relation to the governing agencies andtheir work.

The following list is an outline of the possible issues that should be considered andthe laws and regulations that should be investigated.

Laws The Norwegian Teleloven is an important law that must be examined and it’simpact on ENUM identified. There are also several laws pertaining to telecommunications that must be adhered, and their impact on ENUM should alsobe revised.

Public authorities Implementation and operation of ENUM services might needsupport from public authorities, amongst which PT is the most important sincethey can enforce needed measures regarding E.164 issues that is necessary foran implementation of ENUM. PT is also Norway’s representative in ITU andthe authority that can request the delegation of 7.4.e164.arpa.

Legislative Security Issues The new governing agency “Nasjonal sikkerhetsmyndighet”is an important actor regarding the security issues in Norway. It mightprove that they do not embrace security issues of ENUM since ENUM mightonly be related to personal privacy and telecommunications. Then it is PT thatis the important authority.



Field test We recommend that a field test of ENUM in Norway also comply of athorough investigation of liabilities and regulations pertaining to ENUM.

3.3 Relations to E.164 ActorsThe primary goal must be to keep the E.164 number plan and ENUM unanimous.This means that the valid holder of a number from the E.164 number plan also shallbe the end user pointed out by ENUM.

This will however give rise to the question of who owns the number. In the case ofdomain names within the .no domain, it is only one part that can offer the ownershipof a domain name (Norid). In the ENUM case it is a bit more complicated. In orderto apply for delegation of the ENUM name corresponding to the E.164 number, theapplicant must be the valid “owner” of that number. The applicant must therefore bethe holder of a telephone subscription. What will happen if the subscription is ended?Will the registrant still be a valid owner of the ENUM name? These issues must beresolved prior to providing ENUM services to the public. We recommend that thisdiscussion should be conducted during a field study since it is a matter much betterdiscussed if it can be put into context.

The issue of ownership of a number is only one of the issues that could lead to conflictbetween the ENUM organization at one side and the E.164 actors at the other side.We recommend that means and measures for handling conflicts regarding the relationbetween ENUM and E.164 actors is established as soon as possible. Otherwise willthese conflicts have a potential to paralyze an implementation of ENUM.

3.4 Business Models and Payment SchemesThe money issues must not overshadow the primary issue: ENUM should be an informationservice to the Internet community that enables business opportunities on anew market segment. ENUM is therefore an important part of the development of newtelecom services and technologies. ENUM should be organized and implemented topromote fair competition at the same time as it provides business opportunities.

3.4.1 The Value of ENUM for the End UsersWhen discussing business models, costs and payment schemes it is essential to understandthat ENUM itself only is a database containing access information aboutend users. It does not provide the end user with an application or anything that theend user might find valuable. ENUM services must be wrapped in some product orapplication before the end user is willing to pay for it.

The value of ENUM might be compared to the value of the SS7 routing tables. ThePSTN user don’t care about the routing information services that a PSTN networkneed to be able to route a call, but are willing to pay for the service as a whole.The difference is however that ENUM might be used for so much more than routinginformation.

3.4.2 Termination FeesIt is also important to realize that the structure of the PSTN network, in respect of how



payment is realized in it, will affect the business models of ENUM implementationsand how ENUM is payed for. Take into consideration the following case.

1. A call is initiated from a PSTN network to an IP telephone.2. The call reaches the IP telephony service provider and is, in PSTN respect, terminated

there.3. The call is routed on an IP network and reaches the called number.

The interesting part is that the IP telephony service provider will get the terminationfee from the callers’ PSTN service provider. In the case of the IP telephone user callinga PSTN user, the IP telephony service provider will have to pay the terminationfee.

With ENUM, two IP telephony service providers can interconnect using IP withoutany prior relationship since all necessary call routing information can be found inDNS.

The termination fees are therefore not in themselves an incentive for getting payed forENUM services. But, if the IP telephony service can be offered to the end users forfree, then the cost of the ENUM services that are needed must be covered by billingthe end user for them.

3.4.3 The Costs of ENUM

ENUM DNS Operators’ Costs

ENUM, like other DNS based services, is not free, even though any user might freelyimplement a DNS service. The major part of the Internet community does not implementtheir own DNS services and will probably not do it with ENUM.

An ISP often provide its customers with a DNS service as a part of the Internet connectionservice or as an add-on to the connection service. A potential ISP customermight even consider a solid DNS service to to be a requirement for he or she to buythe services provided by the ISP. The DNS service is regarded as a natural part of theInternet connection services. Payment for the DNS service is not specified but, as apart of the Internet connection services package, it is included.

In the same way will ENUM services most likely be a natural part of an access application,e.g. IP telephony. The cost of providing ENUM services might therefore notbe the object of billing and must be covered with other strategies. ENUM services beseen as a part of the basis that some other application that the end user is willing topay for, e.g IP telephony.

Registrars’ Costs

The Registrars only has administrative costs, mainly originating from registrationsand validations. To promote fair competition between large and small organizationswe suggest that the validation services should be strictly regulated (to keep the costand quality of it at the same level). The alternative is to establish some kind ofpublic authority or governmental agency that carry out validations on a non-profit



basis. This will however diminish the opportunity to decrease the costs of validationsthrough skill and optimization of number of personnel. It would also eliminate theadvantage that the telecom service providers have since they already have a validationprocedure for the PSTN telephone services.

We recommend that this issue is discussed at length before any decision is made aboutthe validation procedure.

Registry’s Costs

The registry’s costs are mainly administrative, if the actor responsible for it alreadyis a registry for DNS. The administrative part might even be the same as for DNS ifthe validation process is placed elsewhere.

The real work with ENUM is done at the registrar and DNS operator level. It is theywho gets the requests, validates and runs the DNS servers containing the NAPTRrecords (the ENUM databases). The registrar only points out the DNS servers thatholds the NAPTR record for a given number.

The ENUM registry is burdened with costs that probably are at the same level asrunning a ccTLD registry. There might even be some possibilities for optimizationsince the services are similar in respect of organization and relations to registrars andother actors.

The cost of billing might be lesser for the ENUM services than for general DNSservices, since the end user most likely will not pay for the ENUM services to theregistry. The registry might limit its costs for billing considerable if it where to billthe registrars and ENUM DNS operators only.



3.4.4 Conclusions and RecommendationsIt is far to early to draw any conclusions about which business models and paymentschemes that would fit the ENUM market. We have however noted the followingissues that could be worthwhile to consider when discussing such topics:

Since ENUM is an enabler for emerging telecom technologies and services, anyorganization and implementation must not oppose the possible business opportunitiesutilizing ENUM.

ENUM services will probably be sold to end users as a part of a service or applicationthat the end user finds worthwhile to pay for. If this is accurate, payment for specifiedENUM services will only be made by the registrars and ENUM DNS operators to theregistry.

The ENUM DNS operators and the registrars costs for ENUM can be covered in severalways. We have noted some aspects of which the issues of termination fees and packagingis the most important. This is however a matter that will be resolved by the commercialactors and need not be addressed in an ENUM study.

Validation must however be discussed and regulated. We suggests that the proceduresthat is used in the PSTN services market is used for ENUM as well, provided it promotesfair competition in an acceptable way.

Since the registry only takes care of the registrations and pointers to ENUM entries(NAPTR records) their costs for the ENUM registry needs not to be different from thecosts of running the ccTLD registry.



3.5 Security ConsiderationsThis section is primarily about security as in “preventing security breaches” and notsecurity as a quality of service, even though many attacks have a negative impact onthe quality of service.

As described in the security considerations of [RFC2916bis], the security model forENUM is basically the same as for any other DNS service.

When discussing ENUM security in a VoIP context , it is also important to know whatsecurity mechanisms are in use in PSTN today and how/if these mechanisms can bemapped to Internet technologies.

We recommend that the DNS security considerations are investigated further by theregistry and that the ENUM application security considerations are revised duringa field test. Note that DNS security and ENUM application security are different inmany ways. The former should be addressed by the DNS infrastructure and the latterby the ENUM application implementors and users.

Correct number validation is essential in the PSTN and also for ENUM. If validationfails, “hijacking” end-user communication could, as in the PSTN, become an easytask. It is therefore essential that the validation procedures for ENUM match thecorresponding procedure for PSTN.



4 References[TELESTAT2002 ] Det norske telemarkedet - første halvår 2002. Post- og teletilsynet. 2003-03-20. http://www.npt.no/pt_internet/venstremeny/publikasjoner/telestatistikk/statistikk2002/halvar/index.html

[REGAVTALE ] Registraravtale. http://www.norid.no/registrar/regavtale.html

[RFC2916 ] E.164 number and DNS. Request for comments: 2916. Patrik Fältström.September 2000. www.ietf.org/rfc/rfc2916.txt.

[RFC2916bis ] The E.164 to URI DDDS Application. Internet Draft, work in progress.Patrik Fältström. April 2003. http://www.ietf.org/internetdrafts/draftietfenumrfc2916bis05.txt.

[RFC3026 ] Liaison to IETF/ISOC on ENUM. Request for comments: 3026. R.Blane. January 2001. www.ietf.org/rfc/rfc3026.txt.

[WP1-2 ] Liaison to IETF/ISOC on ENUM. ITU-TWorking Party 1/2, Berlin, 19-26October 2000. www.itu.int/osg/spu/enum/wp139_rev1.html

ENUM Report · 2015-10-05 · of ENUM and is indeed difficult to come up with a good answer. Most probably, ENUM will initially be used for simple E.164 number to SIP address mapping

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