1. ENUM Administration Issues
Some numbering perspectives
ITU-T ENUM Workshop
Geneva
17 January 2001
Tony Holmes BT
Steve Lind
AT&T

2. 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

3. 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

4. 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:
e164.arpa
Administrative Zones defined:
e164.arpa = Domain Zone
3.3 = Country Code Zone
= National Zone
Note: Here ‘Zone’ refers to a segment of the domain name

5. 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

6. 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.

7. Typical call flows PSTN - IP
Gateway IP
Network
DNS
DNS look up returns
NAPTR record with 4 6
DNS returns SIP server IP address 5
Gateway looks up host for 7
SIP server routes call to user 1 2
( ENUM functionality)
formats url
e164.arpa 3

8. Typical call flows IP - PSTN3
DNS returns record as url
tel:
PSTN
Gateway IP
Network
DNS
Location
server 1 2
Client formats url 4
SIP Client initiates
INVITE to server using tel url 6
LS returns IP address of Gateway 5
SIP sever looks up gateway address from LS 7
Call routed to Gateway
IP address 8
Gateway completes call to PSTN

9. ENUM - DNS Structure & Hierarchy
e164.arpa
RIPE NCC
Tier 1
Registry
4.4.e164.arpa
Tier 2
Service Registrar
1.6.e164.arpa
Tier 3
Application Service
Provider

10. 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

11. ENUM Considerations - 2 Inserting numbers in the DNS Tier 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…….

12. ENUM Considerations - 3 Inserting numbers in the DNS Tier 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).

13. ENUM Considerations - 4 Inserting numbers in the DNS Tier 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

14. ENUM Considerations - 5 Inserting numbers in the DNS Tier 1 Registry
Entries in the Tier 1 Registry point to the Service Registrar for an E164 number
e164.arpa
Tier 2 Service
Registrar
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

15. 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?

16. 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 implications
e.g monitoring of QoS etc?

17. ENUM Considerations - 8 Inserting numbers in the DNS
Tier 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
ISSUE
Determination of who qualifies to be a Service Registrar?
Two alternatives under discussion
Model 1 - any accredited domain name/service registrar
Model 2 - telephone service provider

18. Reference Model I (General)
Legend
ASP Application Service Provider
T1E Tier 1 Entity (Registry)
T2E Tier 2 Entity (Registrar)
TSP Telephony Service Provider
EU End User
T1E
New T2E A H
** 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. B C
T2E
E U F G E D
TSP
ASP

19. ENUM Considerations - 9 Model I Pros & Cons Pros:
Reference Model I
T1E
New T2E
Model I Pros & Cons A H C
T2E
E U B G F E D
TSP
ASP
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 offering
Cons:
More complicated interactions among involved entities
More efforts at T2E to manage the NAPTR RRs

20. Reference Model II (T2E=TSP)
Legend
ASP Application Service Provider
T1E Tier 1 Entity
T2E Tier 2 Entity
TSP Telephony Service Provider
EU End User A’ B’
T2E/TSP
E U
** 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. E’ C’ D’
New T2E/TSP
ASP

21. ENUM Considerations - 10 Pros: Fewer interfaces to deal with
Reference Model II
Pros:
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)
T1E B’ A’
T2E/TSP
E U E’ C’ D’
New T2E/TSP
ASP
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

22. ENUM Considerations - 11 Inserting numbers in the DNS
Tier 2 Service Registrar
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?

23. ENUM Considerations - 12 Inserting 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?

24. ENUM Considerations - 13 Inserting 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) ?