Group A Ad-Hoc
of NeuStar, Inc.
Friday, March 23, 2001
A number of questions regarding the implementation of
ENUM services in the United States were raised during the meeting of the
ENUM Study Group A Ad-Hoc, which took place on February 12-13, 2001, in
McLean, Virginia. NeuStar submits this document in order to answer the
questions raised during that meeting.
NeuStar believes that the United States Government
needs to act quickly to create a process for establishing a single Tier 1
registry for ENUM services in the United States and to support the ENUM
technical solution described in IETF RFC2916.
Because the Domain Name System (DNS) protocol requires that there
be only one authoritative root for each node in the DNS tree, establishing
a single registry for the United States portions of the NANP is of utmost
importance for efficient administration of ENUM in the United States.
The technical principles for the importance of a single
authoritative root are well understood within the Internet Community and
have been described by the Internet Architecture Board in IETF RFC 2826.
NeuStar does not believe that it would prove technically and
administratively workable to implement ENUM in multiple domains.
In implementing ENUM in the United States, NeuStar
believes that the US should adopt a global approach, coordinating with
industry representatives, the International Telecommunication Union (ITU),
the Internet Engineering Task Force (IETF), and other standards and
regulatory bodies in its implementation of ENUM.
The ITU and the IETF have taken a number of positive steps to
coordinate their work in ENUM as outlined in IETF RFC 3026.
The United States should encourage these efforts on an ongoing
basis. ENUM in the United
States must be compatible with ENUM globally in order for the protocol to
perform as intended and to ensure maximum opportunity for industry to
For the promise of ENUM to be fully recognized, it
must be carefully and thoughtfully implemented to ensure the integrity,
reliability, and stability not only of the developing ENUM infrastructure,
but also the existing global telephone numbering system.
Moreover, there remain significant potential policy concerns
relating to the provision of ENUM services.
Therefore, ENUM cannot be allowed to develop entirely on its own.
Because of the mission critical nature of both these
infrastructures, the United States Government must work closely with
industry and the international community to get ENUM properly underway.
Should the US participate in a common global approach with the
implementation of ENUM in the US.?
Yes. The US
should work with the ITU, the ITEF, and other standards and regulatory
bodies in the development of coordinated Internet telephony–related
protocols. In order to
operate as intended, ENUM must work within existing telephone numbering
administrative contexts to facilitate a wide range of applications using
phone numbers as Internet addresses.
ENUM must be coordinated with rules and provisions set forth
internationally and nationally for number administration to ensure that
the integrity of both ENUM and the E.164 numbering plan is maintained.
Absent such international coordination, there will be no assurance
that a US implementation of ENUM would be compatible with other
international implementations, nor could an end user of ENUM services be
assured that a number used corresponded with an existing E.164 number or
was simply a telephone number knock off.
Moreover, a coordinated international implementation will ensure
that US companies are able to develop global market strategies for ENUM on
the global Internet.
If not, what are the other options?
NeuStar believes that a coordinated implementation of
ENUM is the most responsible manner in which to proceed.
Therefore, if at all possible, the US should participate in a
global approach. If, however,
a global approach is unreasonably delayed, the US could move forward with
a controlled, measured implementation of ENUM designed to remain
compatible with any international coordinated effort.
The ability to migrate into a future global implementation must be
Will the US populate some of its NANP resources into e164.arpa?
Are there any anti-trust issues?
In the event that e164.arpa is selected as the
international ENUM root, the US should populate the root with its
designated numbering resources. NANP
resources populated into the e164.arpa root will be appropriate fully
qualified domain names for assigned E.164 numbers.
There are no anti-trust issues introduced by the
implementation of ENUM itself.
Should the US industry work at developing implementation procedures
for other zones, e.g., .com?
As noted above, NeuStar submits that there should not be
alternate implementations of a public ENUM resource on the Internet.
To the extent, however, that private (enterprise) ENUM
implementations make sense within industry and could be implemented in a
manner that does not conflict with a coordinated international ENUM
implementation, development of procedures for ENUM implementations in
other zones would be reasonable.
What are the implications for other countries in the NANP?
Because of potentially complex issues related to
coordination of NANP resources in ENUM, joint understandings between the
members of the NANP would lead to improved efficiencies and lower costs
while preserving both the basis of the NANP and the relevant aspects of
national sovereignty in telecommunications.
Is there an ongoing role for ITU bodies in the manner in which the
US implements ENUM?
is a clear need to establish and maintain an effective working
relationship between the ITU, the IETF and US agencies and entities
responsible for ENUM implementation.
At the very least, the US will continue to work with the ITU and
the IETF regarding issues related to the ongoing maintenance of the
international ENUM root and the relationship between ENUM and E.164.
Moreover, though not directly related to a US implementation of
ENUM, the ITU has a valuable role in educating its Member States on
technical and policy related issues regarding ENUM and assisting all
nations in understanding its implications.
The United States should continue to encourage such activities.
Tier One Registries
Should there be competitive Tier One Registries?
advocates that both technical administrative and policy concerns require
the competitive selection of a single Tier 1 Registry for US NANP
The DNS protocol fundamentally requires that there be
one and only one authoritative root for each node in the DNS tree, see
IETF RFC 2826. Thus, there
should only be one Tier 1 Registry for the NANP, i.e., a single registry
authoritative for country code 1 itself.
Moreover, ENUM clients and the E.164 numbers they attempt to
resolve have no geographic significance in the DNS.
The reason Tier 1 is sub-divided from the global to the national
level reflects the inherent hierarchy of administrative policy areas, not
geographic areas. It is incidental to DNS and ENUM that these national policy
areas map to national boundaries. There
is no way to further sub-divide the ENUM root for US NANP resources based
on geography (e.g., region) in a way that would allow the core
administrative functions of the Tier 1 registry to retain their integrity
and to be performed uniformly and consistently across all users.
Registries inherently require uniqueness relative to their
respective administrative policy areas, hence there is a single .com
registry from which to obtain a new .com domain name, and there is a
single NANPA from which to obtain new NANP resources.
Likewise, there should be one and only one Tier 1 registry for each
national regulatory authority (NRA) area in E.164, sub-divided where
necessary to address NRA boundaries below the country code level.
If so, how many?
As discussed above, one single Tier 1 Registry is
appropriate for the ENUM “root” of E.164 country code 1.
Joint Collaborative effort?
To the extent that a joint-collaborative effort is
consistent with the requirements discussed in the answers above, such
efforts may be considered.
What is the selection process?
A selection process for the Tier 1 ENUM registry should
be a competitive procurement for a single Tier 1 operator handled by the
US government agency identified to implement ENUM in the United States.
The request for proposals for ENUM must address both technical and
policy concerns and likely will require input from both agencies
interested in the Internet and agencies with responsibility for the NANP.
Sole industry responsibility or what amount of Regulatory
The resources to be registered in the Tier 1 registry
(i.e., E.164 telephone numbers) are subject to inherit requirements
stemming from both E.164/PSTN and IP-based/Internet infrastructures.
Regulatory involvement in US Tier 1 is appropriate to the degree
that it is necessary to shape the appropriate uses and policies of the
ENUM service with respect to current regulatory treatments of telephone
numbers and domain names. Such
regulatory efforts will not constitute regulation of the Internet as a
whole, but rather appropriate streamlined safeguards to ensure the
continued integrity of the NANP and the DNS.
What is the overall architecture/hierarchy?
The overall architecture of ENUM consists of functions
grouped into several major categories.
This categorization is useful in describing the service hierarchies
within an ENUM implementation.
The major groups of functions for ENUM are:
IP-based application services,
DNS-based services, and
Grouping functions by these categories renders certain
terms more clear in meaning and scope, and provides a framework for
underlying assumptions regarding ENUM implementation.
Moreover, discussion of ENUM in terms of service categories rather
than operational entities avoids potential confusion when a single entity
performs multiple different functions.
IP-based Application Services are the ENUM functions related
to IP services that allow end users to, for example, send and receive
email, view web pages, send and receive faxes over the Internet, and use
voice over IP.
A specific service may be
provided by one or more Application Service Providers (ASPs) chosen by the
user. Associated with that
service will typically be a service-specific address.
ENUM itself is not an
IP-based Application Service given that it does not carry any user
addresses reside in the Tier 2 level of ENUM DNS-based functions.
DNS-based services are the functions related to the
maintenance and provision of information about domain names and associated
information such as service-specific addresses.
ENUM is a DNS-based service.
The domain names are “ENUM names” for telephone numbers.
The “ENUM Service” itself is the ability for an ENUM subscriber
(known as the “End User” of the ENUM Service) to make certain
information available for retrieval through DNS queries.
The information retrieved based on the End User’s telephone
number is one or more service‑specific addresses.
The DNS provisioning of
telephone numbers for ENUM is divided into two primary sets of functions
(Tier 1 and Tier 2). Country
codes reside at the “Tier 0” level.
An additional level of service-specific information (Tier 3) may be
provisioned depending on the specific service.
Tier 0 is sometimes
used to refer to DNS functions that manage ENUM root-level information and
the ENUM names for E.164 country codes.
Tier 1 refers to DNS
functions that manage the ENUM name for an E.164 country code and to the
DNS functions that manage the ENUM names for telephone numbers within that
Tier 2 refers to DNS
functions that manage the ENUM name for a telephone number and the End
User’s choices of NAPTR records for service-specific addresses, which
would all be returned in the response to any DNS queries about the End
User’s telephone number. The End User can choose a Tier 2 entity by subscribing to its
ENUM service offering.
PSTN-based services are functions for non-IP based telephony
services, telephone numbers for those services, and non-telephony services
necessary to support such non-IP based telephony services.
A telephone number is assigned in conjunction with a telephony
service. Telephone numbers in ENUM are E.164 numbers assigned for
telephony services. ENUM
names for telephone numbers reside in the Tier 1 level of ENUM’s
DNS-based functions. ENUM
names for country codes are located in the Tier 0 level.
With multiple providers what are the functions, definitions,
relationships, and flows between the various service entities?
In order to ensure the integrity of E.164 and ENUM, the
ITU and the IETF have established agreements that address the
administrative aspects of ENUM, see IETF RFC 3026.
It has been agreed that all administrative entities, including the
DNS administrators of ENUM resources, will adhere to pertinent ITU
Recommendations, e.g., E.164, E.164.1, and E.190, as well as applicable
ITU principles and procedures.
For all E.164 Country Codes, the ITU will provide
assignment information to the DNS administrator of the E.164/ENUM root
Thus, whenever an NRA, such as the United States
government, determines that E.164 numbers under its jurisdiction should be
placed in the DNS, it will inform the ITU.
The ITU will then authorize the inclusion of the appropriate
specific country code as a Country Code zone of DNS authority.
This action includes the delegation of authority for DNS
administration of that Country Code zone to the NRA(s) to whom the E.164
country code is assigned.
The following tables describe the relationships and
roles of the various ENUM functions and the entities providing those
functions. The first table
illustrates some basic attributes of the DNS Tiers for E.164 numbering in
ENUM, and is based on an example taken from RFC 3026, which contains the
Liaison Statement on ENUM from the October 2000 meeting of ITU-T Working
Party 1 of Study Group 2 in Berlin.
DNS Tiers for E.164 Numbering in ENUM
Type of Tier
Authority for the Domain
The NRA(s) (from the ITU perspective):
via DNS delegation from the ITU, and
consistent with the E.164 country code assignment.
A national matter:
delegation of authority from the country’s Administration,
consistent with the E.164 number assignment, and
based on the assignee of the number subscribing to ENUM.
Administrator/ Operator of the Domain
As designated by the ITU.
As designated by the NRA.
A national matter:
as designated by the entity with delegated DNS authority.
DNS Record(s) within the Domain
A record points to the sub-domain 3.3 of [ENUM.Root].
A record points to the sub-domain 188.8.131.52.0.2.0.4.1 of
Records contain URIs with address information for
(IP-based) specific services:
the assignee of the number subscribes to each specific
the assignee of the number chooses to have each
service-specific URI be in DNS for ENUM, and
the URIs are associated with the assigned number.
Type of Tier
The next three tables describe the roles of functional
entities involved in ENUM services, and contain additional information on
relationships between these entities.
Table 2 looks at the four levels of ENUM Tiers.
Users and Service Providers are described in Tables 3 and 4
respectively. These groupings
help clarify how the different roles need to interact in order to provide
Functional Entities - DNS Tiers for ENUM
[E.164/ENUM DNS Root]/
“Tier 0” Entity
Operates the DNS ENUM Root.
Holds ENUM information about E.164 country codes.
NS records point to Name Servers for the DNS Registry for
each E.164 country code in ENUM.
Tier 1 Entity
The DNS Registry for a country code level ENUM domain.
Holds ENUM information about E.164 numbers.
NS records point to Name Servers for the DNS Registrars
within the E.164 country code in ENUM.
Tier 2 Entity
A DNS Registrar of E.164 numbers for ENUM within a country
Holds ENUM information about service-specific addressing that
is associated with an E.164 number.
NAPTR records hold service-specific address information for
the Registrants of E.164 numbers for ENUM with the DNS Registrar.
Tier 3 Entity (may or may
not exist for a specific (IP-based) service)
Contains service-specific information for client software to
use after performing its ENUM query.
Depends on the specific service.
Depends on the specific service.
Functional Entities - End Users and Calling Users for ENUM
ENUM End User/ ENUM
Subscriber/ Called User
The DNS Registrant of an assigned E.164 number for ENUM.
Is a subscriber to at least one (IP-based) specific service.
Is the authority for using ENUM to associate information for
that specific service with the E.164 number.
Provides information on an E.164 number assignment and on
Specifies preferences for the association of specific
services with the E.164 number.
Intends that calling users could contact the End User by
using ENUM information.
An End User
has three types of subscription:
as assignee of an E.164 number [for a telephony service].
as subscriber to one or more (IP-based) specific services.
as party responsible for specifying how ENUM associates the
number with service-specific URIs.
Is a calling user who queries DNS to retrieve
service-specific information associated with the E.164 number of an
ENUM End User.
May or may not use the service-specific addressing
information to “call” the ENUM End User.
Intends to contact an ENUM End User via a specific service
but addressed with an E.164 number.
Uses ENUM-enabled client software to discover End User’s
May or may not choose a specific service to contact the End
A calling user chooses to contact an ENUM End User.
ENUM-enabled software performs the ENUM query.
Service-specific software makes the “call” using
service-specific address information resulting from an ENUM query of
Functional Entities - Service Providers for ENUM
Telephony Service Provider
The provider of telephony service to an End User (Subscriber)
of that service.
Is authorized by the End User to provide current information
about the assigned E.164 number to the Service Registry.
The E.164 number is assigned to an End User for the
subscribed telephony service.
The provider of a specific IP-based service to an End User
(Subscriber) of that service.
May be authorized by the End User to provide current
information about the service-specific URI to the Service Registrar.
The ASP may be authorized by the End User to add, change, or
delete the service-specific NAPTR held by the Service Registrar.
How can interconnection between multiple entities be efficiently
The structure described above is essentially one of a
Registry handling Tier 1 functions and a Registrar responsible for Tier 2.
This model is well known in the Internet Community.
It is clear that policy relating to the appropriate roles and
responsibilities of the various entities described above need to be
developed and documented.
What kinds of tools and mechanisms are necessary?
With the proper documentation of appropriate roles and
responsibilities of the various entities involved in the ENUM process,
functional and secure software can be developed that can facilitate these
transactions. NeuStar believes that the development of such software
should follow well-established principles of open protocol development by
the technical community. Because ENUM is a DNS-based service, many of the appropriate
tools already exist or are being developed for other DNS operations.
4 Tier 2 Service
What are the criteria for Tier 2 service providers?
Tier 2 service providers must be technically capable of
interconnecting with the Tier 1 service provider for the purpose of
registration of E.164-based “ENUM Names.”
Providers must be prepared to verify this capability through
testing procedures established by the Tier 1 operator.
In addition, a Tier 2 service provider must be prepared
and capable of adhering to specific policies and requirements established
by the Tier 1 operator and the National Administration responsible for
telephone numbers within a given country code.
The requirements and policies will be designed to protect the
integrity of both the national telephone numbering plan (the NANP in the
case of country code 1) and the DNS.
These requirements and policies will be established in the future,
but include such concerns as line status and assignment verification,
number slamming and hijacking, privacy, and DNS security protocols.
This model presumes multiple competitive Tier 2 entities
much like in the existing DNS industry.
What is the definition and scope of Tier 2?
Consistent with the discussion above, a Tier 2 provider
provides the DNS functions that manage the ENUM name for a telephone
number and the End User’s choices of NAPTR records for service-specific
addresses, which would all be returned in the response to any DNS queries
about the End User’s telephone number.
The End User can choose a Tier 2 entity by subscribing to its ENUM
Should there be a qualification process?
Yes, there must be a process to ensure that a Tier 2
entity meets the criteria discussed above.
Moreover, in order to address concerns over implementation of
policy matters and service restrictions, the National Administration may
seek to establish a separate or additional process for determining the
suitability of a Tier 2 provider.
5 General Issues
What is the appropriate role of US government agencies, and/or
industry self-regulating bodies?
An effective implementation of ENUM will require that
both sets of bodies work together to address the issues and challenges
related to ENUM services. Industry
self-regulating bodies must work to establish appropriate standards and
policies to effectively govern certain aspects of the ENUM industry.
Likewise, US agencies will monitor ENUM implementation with the
sphere of their respective jurisdictions and take any action deemed
necessary and appropriate. In
the final analysis, a properly structured ENUM implementation can minimize
necessary government involvement.
Industry testing of ENUM?
Testing of ENUM is critical.
Visible aspects to be tested are operational issues including
performance (e.g., response time and variance, volume and distribution of
queries), protocol correctness (values in queries and responses, values in
DNS records), and DNS structure. Other
aspects such as zone administration, subscriber information handling, and
privacy also require testing.
Industry must be able to perform testing at the earliest
possible stages so that experience and results can guide further
development and operable implementation.
Industry also must begin to define testing procedures that would be
appropriate for maintenance and fault resolution when ENUM is operational.
How is authentication and validation of subscriber choice and right
to use an E.164 number achieved?
It is essential that authentication and validation of a
subscriber’s right to populate their ENUM resources as well as
authentication and validation of their choice of services be a paramount
consideration of ENUM operators. ENUM
cannot and will not succeed if consumer confidence in the integrity of the
system, end to end, is not maintained.
On the question of validating the subscribers right to populate
their ENUM resources in the ENUM system, NeuStar submits that there are
sufficient authoritative databases within the United States
telecommunications industry to support the development of an effective
mechanism for validation of subscribers seeking registration of a given
telephone number. In addition
those databases can facilitate the verification of the line status
(whether a particular number has been disconnected from the PSTN) to
determine when ENUM resources associated with a number should be
disconnected. It is critical
that ENUM in the United States be implemented in a manner that prevents,
from the outset, number hijacking, slamming and cramming.
How are NAPTR records zones administered and discovered?
There are significant policy considerations in the
administration of Tier 2 entities, especially if those Tier 2 entities are
service providers acting on behalf of consumers.
The purpose of ENUM is to create not only competition in the
creation of new services but to permit multiple service providers to
compete through equal access to NAPTR records for the purpose of service
creation. Considerable care and consideration will have to be given to the
roles and responsibilities of Tier 2 providers.
As for the actual method by which NAPTR records are Added, Modified
or Deleted, a variety of tools exist or can be created and implemented by
Tier 2 providers that permit authentication and validation of NAPTR record
What is the disconnect notification process between TSPs and the
As noted above, sufficient authoritative database
resources exist within the United States to provide timely notification of
telephone number disconnection. Access
to these database resources can be legally acquired in order to assist
ENUM service providers in properly disconnecting ENUM resources at the
time PSTN service is disconnected.
What types of NANP resources should not be populated in ENUM, e.g.,
In general, NANP Resources that are not both assigned
and in service should not be populated in ENUM.
Certain other specific non-geographic NPAs and US‑assigned
N11 NPAs should not be populated without further study to determine their
feasibility and suitability with respect to ENUM implementation.
NPAs requiring additional consideration include:
Personal Communication Service
Interexchange Carrier Services
N11 - abbr
- Community Information and Referral Services (US)
N11 - abbr 311
US - Non-Emergency Police and Other Governmental Services (US)
N11 - abbr
- Traffic and Transportation Information (US); Reserved (Canada)
N11 - abbr
- Telecommunications Relay Service (TRS)
The unassigned N11 NPAs should not be populated in any case
since they are not assigned.
N11 - abbr
- Local Directory Assistance
N11 - abbr
- Repair Service
N11 - abbr
- Business Office
N11 - abbr
Would there be a need for additional NANP assignments to ENUM?
current view of ENUM requires that numbers can only be eligible for ENUM
if (among other criteria) they are assigned specifically for legitimate
telecommunications use via appropriate processes.
In fact, it is quite possible that a well-managed ENUM environment
will lessen the pressure on the need for new numbers, and could, as a
result, extend the viability of current NANP assignments.
What are the effects of ENUM on NANP utilization?
ENUM will have no necessary direct effects upon NANP
utilization. ENUM works with
numbers that already are assigned to a telephony service subscriber under
existing number assignment rules. Numbers
will not be assigned solely for use with ENUM.
As noted above, however, ENUM reduces the number of separate
telephone numbers needed for different functions (such as voice,
voice-mail, and facsimile). In
this manner, ENUM actually may reduce utilization pressures on the NANP.
Criteria for transaction security?
Two primary types of transaction security must be
considered in an ENUM implementation.
First is the transaction security between the various service
entities in the ENUM process, and second is the transaction security
between zones within the DNS for the purpose of updating records and zone
files. In both cases,
significant work has been done on secure mechanisms for handling secure
processing in the DNS. This
work will be applied in the implementation of ENUM.
How are consumer protection and privacy maintained?
It must be understood from the outset that the global
Domain Name System is completely open.
That is why the Internet works.
The information stored in the ENUM should be relevant only to the
making of connections between end points and not personal data.
It is therefore useful to view ENUM as a “Service Control
Point” within that context. It
is therefore useful to view ENUM as a “Service Control Point” within
that context. Personal data
of an End User should not be exposed in the DNS.
Rather, such information should only exist within the service
context itself at a Tier 2 or Tier 3 level.
For example, for a SIP or Voice Profile for Internet Mail service
offering, the DNS portion of the ENUM implementation only stores the
pointer to the proxy or server where actual personal data or service logic
exists to support the service. Therefore,
the primary consumer protection and privacy concerns exist at the service
provision level. In many
service contexts, existing laws, regulations, and policies serve to
protect consumers. Where such
protections do not exist or are not effective, the ENUM industry must work
together and with public interest advocates and agencies to address any
issues. As noted above, the
necessity to implement sound and sufficient policies and procedures in the
ENUM registration process in order to insure consumer protection is of
paramount concern. NeuStar
believes that sufficient resources and processes exist to address most
What is the Conflict Resolution process?
As with any DNS implementation, potential for disputes
exists between the various entities providing the relevant service, as
well as between those service providers and the users of the service.
There has been significant work to date in developing dispute
resolution mechanisms relating to DNS services in the Internet Community.
ENUM providers must draw on this experience to propose and develop
similar mechanisms for ENUM specific disputes.
For example, disputes regarding authority to register a telephone
number could be addressed by a process to the Uniform Dispute Resolution
Process established by the Internet Corporation for Assigned Names and
Numbers (ICANN). Other
mechanisms, no doubt, will have to be considered.
What are the effects of ENUM on DNS performance?
Some ENUM participants have voiced concern with respect
to the possible effects of ENUM on DNS performance.
This concern is particularly strong in relation to the possible
need to implement DNS Security (DNSSEC) at some point in time in order to
maintain the integrity and authoritative nature of the ENUM zone files.
NeuStar believes that there is no doubt that the ENUM
root will be able to scale sufficiently to meet the requirements of
handling the resources required by Recommendation E.164.
Each digit in the ENUM Fully Qualified Domain Name represents a
discrete and potentially distributed zone in DNS terms.
DNS zone management is a well-understood technical art in the
Internet Community. The
highly distributed and global nature of the DNS itself clearly indicates
that ENUM will be capable of scaling appropriately.
In addition, NeuStar strongly believes that any
potential negative impact, if any, on the DNS can be addressed by
technical standards bodies, such as the IETF, through the development of a
series of Best Current Practices and other documentation to instruct ENUM
zone administrations on proper operation and configuration of their
The Internet Community has spent many years developing a
variety of tools and protocols for implementing security within the DNS
itself. NeuStar believes that the emerging United States ENUM
community must study the implications of DNSSEC on ENUM operations and be
prepared to implement DNSSEC within the United States ENUM implementation
once it is clear that these protocols and tools have reached a sufficient
level of maturity and stability. It
is hoped that the US government will continue to actively support ongoing
research and development in these areas.
Finally, it will be a necessary aspect of the
qualifications of all ENUM service providers that they ensure that they
provision sufficient scalable capacity within their service systems to
handle the level of traffic for the telephone numbers