ENUM Administration Issues

Tony HolmesBTtony.ar.holmes@bt.com

ITU-T ENUM WorkshopGeneva17 January 2001

Some numbering perspectives

Steve Lind AT&Tsdlind@att.com

Agenda

• WP1/2 Liaison to IETF/ISOC

• Some typical call flows

• ENUM DNS structure and Hierarchy

• ENUM Considerations and issues

A glossary of terms used can be found at the end of this slide pack

The Aim of this session

• To help raise awareness and assist administrations in understanding what needs to happen to make ENUM work

• To consider the administration requirements of ENUM

• To identify issues …..not only those that need to be tackled by the

ITU but also by Member States and other parties

WP1/2 Liaison to IETF/ISOC Results of DNS Administrative discussions and Contributions - October 2000

ITU-T WP1/2 Meeting - Berlin. Understandings regarding the method for administering and maintaining the

E.164-based resource data in the DNS. Administration = provision and update of E.164 numerical values, of domain

“e164.arpa”, in the DNS. Example of “e164.arpa” domain name:

1.5.1.5.0.2.0.4.1.3.3.e164.arpa Administrative Zones defined:

e164.arpa = Domain Zone

3.3 = Country Code Zone

1.5.1.5.0.2.0.4.1 = National Zone

Note: Here ‘Zone’ refers to a segment of the domain name

WP1/2 Liaison to IETF/ISOC Agreements regarding the administration of Zones

Domain Zone is outside the scope of the ITU Country Code Zone

• ITU provides assignment data to the DNS Administrator

• ITU Member States authorize/deny the ITU to notify the registrar of E164.arpa to include their Country Code

• No data entry for “spare” or test codes National Zone

• National Matter - determined by each Member State

• Shared Network Codes - each entity determines

• Groups of Countries - the administrative entity for the Group determines, in consultation with participating Member States

WP1/2 Liaison to IETF/ISOC• Other Agreements

Once data input is authorized, each Member State/Administrative Entity is responsible for update and accuracy of data.

Data not authorized for input will not be entered in the DNS.

All Administrative Entities (including the DNS Administrator) will adhere to the tenets of pertinent ITU Recommendations e.g. E.190, E.164 etc.

WP1/2 will provide guidance to assist the Member States and Administrative Entities in the performance of their responsibilities - the purpose of this meeting.

6 DNS returns SIP server IP address

5 Gateway looks up host for

itu@sipservice.foo

Typical call flows PSTN - IP

+41 22 730 58871

+41 22 730 58872( ENUM functionality)

formats url7.8.8.5.0.3.7.2.2.1.4.e164.arpa

3

DNS look up returns NAPTR record withitu@sipservice.foo

4

7 SIP server routes call to user

PSTNGateway

IPNetwork

DNS

+44 1473 123456

+41 22 730 5887

Typical call flows IP - PSTN

1 +44 1473 1234562 Client formats url

+44 1473 123456

+41 22 730 5887

PSTNGateway

IPNetwork

DNS

Locationserver

3 DNS returns record as url

tel:+441473123456

7 Call routed to Gateway IP address

8 Gateway completes call to PSTN

4 SIP Client initiatesINVITE to server

using tel url

5 SIP sever looks up gateway address from LS

6 LS returns IP address of Gateway

ENUM - DNS Structure & Hierarchy

e164.arpaRIPE NCC

Tier 1Registry

Tier 2Service Registrar

Tier 3 Application ServiceProvider

4.4.e164.arpa1.6.e164.arpa

ENUM Considerations - 1 Inserting numbers in the DNS

Tier 1 Registry• Registries will be identified by each participating Member State• Entries will point to the Service Registrar for a number

ITU & IETF position states:ITU has responsibility to provide assignment information.Geographic Country Codes will only be included in the DNS when authorised by the Member State responsible for that code

ISSUE• An agreed process needs to be developed e.g. between

appropriate authorities (participating Member States, potentially ITU-T) and Tier 1 Registries

ENUM Considerations - 2 Inserting numbers in the DNSTier 1 Registry

ITU & IETF position states:Each administration is responsible for ensuring DNS administrators (Registries) are aware of appropriate changes

ISSUES• Maintaining integrity of E.164• Building ENUM integrity • Not all countries have the same regulation or rules of

administration BUT all need to address the same issues for ENUM

• How should Tier 1 Registries be selected?- it’s a national matter

but there are options…….

ENUM Considerations - 3 Inserting numbers in the DNSTier 1 Registry

…could be one or more Tier 1 Registry providers per CC e.g.- integrated number plan could be separated by national

authorities- Tier1 Registry(s) could be separated by number ranges

within a CC but there can only be one Registry per E.164 number

ISSUES• How to determine the most appropriate arrangement?• Who runs national Registries?• An agreed process needs to be developed between

participating Member States and their Tier 1 Registry provider(s) (national matter).

ENUM Considerations - 4 Inserting numbers in the DNSTier 1 Registry

ITU & IETF position states:For national zone resources behind the CC shared by Networks the resource assignee is responsible for providing E.164 assignment information to the DNS Administrator

• Network Code assignees need to be made aware of ENUM rules• ITU Recs may require amendment to embrace this

ITU & IETF position states:For national zone resources behind the CC shared by Groups of Countries the resource assignee is responsible for providing E.164 assignment information to the DNS Administrator

• ITU Recs may require amendment/development to embrace this

ISSUE• In some cases with Number Portability, the name server

must point to a Service Registrar on an individual E164 number basis, not a number block

• The full implications on all methods of NP and associated processes need to be understood

Inserting numbers in the DNSENUM Considerations - 5

Tier 1 Registry

Entries in the Tier 1 Registry point to the Service Registrar for an E164 number

e164.arpa

Tier 1 Registry

Tier 2 Service Registrar

ENUM considerations - 6 Inserting numbers in the DNS

Enables the use of an E.164 number allocated to a Service Provider to be used to deliver calls to another Service Provider

ISSUES

• Network by-pass

• Some countries are moving to single number administration and payment for numbers, does this raise additional issues?

• Rights of ownership?- differences across administrations?- Intellectual Property Rights?

ENUM considerations - 7 Inserting numbers in the DNS

Enables the use of an E.164 number allocated to a Service Provider to be used to deliver calls to another Service Provider

ISSUES• Customer perception where an E.164 number that provides

access to an ISP, other than the one responsible for the number, experiences differing QoS and cost?

• Privacy of information/consumer protection

• Legal intercept?

• Regulatory implicationse.g monitoring of QoS etc?

ISSUE• Determination of who qualifies to be a Service Registrar?

Two alternatives under discussion Model 1 - any accredited domain name/service registrarModel 2 - telephone service provider

ENUM Considerations - 8 Inserting numbers in the DNSTier 2 Service Registrar

e164.arpa

Tier 1 Registry

Tier 2 Service Registrar hosts NAPTR records for E.164 numbers

All records for a given number must be in one name server

points to Registry

points to Service Registrar for an E.164 number

Reference Model I (General)

T1E

T2E E U

TSP ASP

A

BC

F G

ED

New T2E

H

LegendASP Application Service ProviderT1E Tier 1 Entity (Registry)T2E Tier 2 Entity (Registrar)TSP Telephony Service ProviderEU End User

** End User can be the end user itself or an agent authorized to represent the end user.** TSP can offer application services also. The “TSP” entity performs functions specific to the TSP.

T1E

T2E E U

TSP ASP

B

C

G

ED

A

F

New T2E

H

Reference Model I

Model I Pros & Cons

Pros:• EU determines T2E, EU has more control• EU can be T2E (e.g., universities and enterprises) for his/her own E.164 number(s)• Enable competitive T2E service offeringCons: • More complicated interactions among involved entities• More efforts at T2E to manage the NAPTR RRs

ENUM Considerations - 9

Reference Model II (T2E=TSP)T1E

T2E/TSP E U

LegendASP Application Service ProviderT1E Tier 1 EntityT2E Tier 2 EntityTSP Telephony Service ProviderEU End User

ASP

A’

C’

New T2E/TSP

E’

B’

D’

** End User can be the end user itself or an agent authorized to represent the end user.** TSP can offer application services also. The “TSP” entity performs functions specific to the TSP.

T1E

T2E/TSP E U

ASP

A’

C’

New T2E/TSP

E’

B’

D’

Reference Model II

ENUM Considerations - 10Pros:• Fewer interfaces to deal with• Easier to verify End Users’s identity

and ownership of the E.164 Number• More incentives for TSPs to get

involved in ENUM process (e.g., verify End User’s ownership of a

E.164 Number and inform T1E about E.164 number service disconnect)

Cons: • Only TSPs can be T2E, non-competitive if there is only

one TSP in a serving market• Non-TSPs cannot be T2E• End Users cannot be T2E for their own E.164 Numbers• End Users cannot get ENUM service if none of TSPs in

the serving market offers ENUM service

ENUM Considerations - 11

Some Administration issues from the Service Registrar models

• Is one, or a number of different model(s) preferable?

• Who should be Service Registrars?

• How can E.164/DNS integrity be safeguarded if responsibility for number insertion in the DNS lies with the customer?

• How should validation of subscriber identity, data & NAPTR (service records) occur?

• How can number/name hijacking/fraud be prevented?

Inserting numbers in the DNSTier 2 Service Registrar

ENUM Considerations - 12Inserting numbers in the DNS

ISSUES• How will number changes/number churn be handled?

• How will ceased numbers be notified/recovered?

• Could prepaid mobile numbers be inserted?

• If so how will ownership be validated ?

• How will changes/ownership/loss/ theft/cease issues be addressed?

• Who has these responsibilities?

ENUM Considerations - 13Inserting numbers in the DNS

ISSUES

• Geographic numbers would lose location information, will begin to look more like personal numbers

• Impact on number plans/number administration?

• Are additional controls required where numbers are shared?

• Should/could requirements on carriers/third parties be enforced?

• Do ENUM procedures and rules apply if E.164 numbers are inserted in other domain name space (e.g .com/other domains) ?