Post on 27-Mar-2015
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) ?