Workshop on Numbering Plan Policies

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Introduction to ENUM
Abdelfattah ABUQAYYAS CoE/ARB
Coordinator abuqayyas_at_itu.int ITU - BDT
2
What is E.164

• ITU-T Recommendation E.164 The international
  public telecommunication numbering plan
• Tied to treaty obligations (specific roles and
  obligations defined for ITU Member States and
  ITU-T TSB Director)
• Defines number structure and functionality for
  principal categories of numbers

3
What is DNS

• The Domain Name System (DNS) is a distributed
  hierarchical lookup service
• DNS is a system of names that enables domain
  names to be translated into IP addresses and
  vice-versa.
• Although the Internet operates on the basis of
  IP addresses, the DNS enables us to use
  easy-to-remember domain names.\

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What is DNS?

• To understand the DNS hierarchy, it is helpful to
  examine the structure of Internet host names
• The last portion of a host name, such as .int, in
  the case of the www.itu.int (the ITUs web site),
  is the top level domain (TLD) to which a host
  belongs.
• There are currently a set of generic top level
  domains (gTLDs), such as .com, .net, and .org,
  as well as country code top level domains
  (ccTLDs), such as .be for Belgium, Other top
  level domains, such as .int, .gov, .mil and .edu
  do not fit into either of the classifications
  above they form a set of chartered TLDs with
  registration entrance requirements.

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What is DNS?

• The root node of the Internet name space consists
  of a single file, the root zone file. The root
  zone file contains pointers to the master
  (primary) and slave (secondary) servers for all
  Internet top level domains (e.g., gTLDs, ccTLDs).
• At the top of the DNS database tree are 13 root
  name servers consisting of a primary server,
  a.root-servers.net, and 12 secondary name
  servers.
• The location of the 13 root name servers is shown
  in next slide. Ten of these are in the United
  States, while the remaining three are located in
  Japan, Sweden, and the United Kingdom.
• Currently, the primary root server,
  a.root-servers.net, is maintained by Verisign
  Global Registry Services.
• As a specific example, the root zone file
  contains pointers to the name servers for the
  .com, .net, and .org gTLDs, also managed by
  Verisign Global Registry Services.

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Location of DNS Root Name Servers
7
Distribution of Current gTLD Name Servers
8
What is ENUM?

• ENUM is an IETF standard (RFC 2916)  for mapping
  the public telephone number address space into
  the Domain Name System (DNS).
• The ENUM protocol involves associating telephone
  numbers with network resources or services in the
  DNS.
• For example, a specific E.164 number can be
  coupled with, inter alia, other E.164 numbers,
  such as fax and mobile numbers, voice mail
  systems, an IP telephony address, an email
  address, a web site or any other resources or
  services that can be identified through a
  widely-used Internet addressing scheme called
  Uniform Resource Identifiers (URIs) 
• The ENUM protocol requires that related services
  be looked up through a convention of one-to-one
  reverse mapping of digits in an ITU-T
  Recommendation E.164 number into separate DNS
  zones which are then concatenated with
  another domain.

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How are E.164 Numbers Mapped into the DNS?

• The Internet Architecture Board (IAB), has
  proposed that this domain be e164.arpa.
• As an example, lets construct the related DNS
  domain to look up NAPTR resource records
  associated with the number 33 1 40 20 51 51
  which corresponds to the information desk at the
  Louvre Museum in Paris, France
• Write the E.164 number in its full form,
  including the country code, then remove all
  non-digit characters with the exception of the
  leading .
• Example 33140205151
• Remove all characters with the exception of the
  digits and put dots (.) between each digit
  Example 3.3.1.4.0.2.0.5.1.5.1
• Reverse the order of the digits and append the
  ENUM Tier-0 zone to the end. Example
  1.5.1.5.0.2.0.4.1.3.3.e164.arpa
• If the Louvre Museum had chosen to provision its
  number in the DNS for ENUM services, the client
  application could now perform a lookup on this
  name and, for example, retrieve the NAPTR records
  for a corresponding fax number, email address or
  any other URI for the E.164 number 33 1 40 20 51
  51.

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NAPTR-Records (Naming Authority Pointer)

• Defined in RFC2915
• Horribly complex
• Define preferences and order to reach services
• Can include regular-expressions and substitutions
  
• Ultimately identify URIs
• Example
• NAPTR 100 10 "u" "sipE2U "!.!sipjim_at_sip.nomi
  num.com!"
• How to reach a SIP gateway for some phone number
• Order and Preference fields allow intelligent
  selections of services protocols to be made
• Send email if the SIP gateway is unable to
  process fax now
• Dont call my cell phone when Im overseas
• Divert to voicemail if busy

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What ENUM Is And Is Not

• ENUM IS NOTa directory a search service a
  transport service a telephony service or voice
  encoding method.
• ENUM IS NOT just about SIP (Session Initiation
  Protocol) SIP gateways are often the targets of
  NAPTR records
• Or just Voice over IP (VoIP) Not just voice
  traffic and Not just about IP-based services
• ENUM ISA partial mapping of E.164 numbers to
  domain names that define a set of services
  identified by a URI labels
• ENUM IS an Enabler of IP Telephony
• The same ITU-T E.164 telephone number would reach
  a subscriber regardless of whether IP-based or
  PSTN network technologies are used.
• ENUM can be used for other telephony (like)
  services Fax SMS, MMS Paging Instant
  Messaging

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E.164 as a common address substrate ?
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ENUM Potential

• Convergence between telephony and Internet worlds
• i.e. one network for everything
• Smarter devices
• Routing diverting telephone calls
• Integrated Messaging Services multi-media
• E.164 number becomes the only thing to remember
• An ENUM DNS lookup could return the users email
  address(es), web site, IRC identifier, SIP
  gateway, etc
• ENUM also being considered by telephone companies
  to simplify call routing and number portability
• One phone number for life?

14
ENUM Jargon

• Tier-0
• The registry operator for e164.arpa and its name
  servers
• Tier-1
• Registry for a country e.g. 4.4.e164.arpa
• Codes are not just for countries satellite
  operators, multinational telcos, international
  free phone numbers
• Tier-2
• Registrars who process registration requests
• Not area code level delegations as the
  terminology might suggest
• What happens at Tier-1 becomes a national
  matter
• Its up to each country to decide
• How its registry is chosen and operated
• How any sub-delegations (if necessary) are done
• What rules and policies apply nationally
• Whether it participates in ENUM or not

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The Golden Tree

• Simply follows the Tier-0, Tier-1 national
  numbering hierarchy under e164.arpa
• Widely accepted by the industry regulators
• Regulators need to control their national
  telephone numbering plans and how they are used
• Telephone companies wont stray from E.164 and
  ITU recommendations
• Golden tree is sparsely populated today
• Various efforts to set up rival trees
• Currently not credible, but could be significant
• Typically attempts to gain commercial advantage
  by pre-empting the market
• Unlikely to succeed unless a major vendor forces
  a universal, de-facto solution

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Alternate ENUM Trees

• Other ENUM-like trees exist
• Far worse than Alternate Roots in the DNS
• Dont just fragment the name space
• Jeopardizes the integrity of E.164 numbering
• Causes user confusion which tree is someones
  number registered?
• Creates serious impersonation and domain name
  disputes
• What if your number is registered in another tree
  by someone else?
• What if that tree is owned by a company that
  doesnt operate in your country?
• Or that company ignores your national telcom
  regulator?
• What about national privacy, data protection or
  consumer protection considerations?
• Cant be ENUM if its not anchored under
  e164.arpa

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Integrated Numbering Plans

• Essentially only a problem for North America
• Many countries use 1 USA, Canada, Jamaica, etc
• Also 7 for the former Soviet Union
• In DNS this implies one delegation for
  1.e164.arpa
• Obvious sovereignty considerations
• Different legislation and regulation in each
  country
• Current thinking is to delegate every area code
  for each country to the recognised national
  authority
• Technically clumsy and messy
• But far easier to solve than the political
  problems

18
Legal Considerations

• Data privacy protection
• ENUM names (numbers) usually identify people
• Restrictions on how that data is stored and
  processed
• What about unlisted phone numbers?
• What about a household with 1 phone number?
• Competition legislation
• Is there fair and free competition?
• By definition, domain names are a monopoly
• Potential for telephone by-pass
• Use SIP gateways and VoIP wheres the phone
  call?

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The Politics of ENUM

• Many players
• Internet Engineering Task Force (IETF)
• Define the ENUM protocol NAPTR record format
• Also define related protocols SIP, VoIP, etc
• Internet Architecture Board (IAB)
• Steering body for IETF
• Tasked with making the Internet work
• International Telecommunications Union (ITU)
• International institution (part of United
  Nations)
• Define telephony radio standards
• Owns the E.164 telephone numbering standard

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Potential ENUM Political Problems

• Integrity of E.164 numbering plan
• Critical for worlds telephone system
• Phone companies need this for billing, routing,
  etc
• National Identity
• What is and isnt a country
• National Sovereignty
• Who controls what happens to a countrys national
  resources? i.e. its E.164 numbers?
• E.164 national codes
• What codes are valid and who owns them?

21
Pragmatic Solution

• IAB selected RIPE NCC to operate Tier-0 registry
• Delegation requests checked by ITU
• ITU determines what is and isnt a country and
  what is and isnt a valid E.164 country code
• ITU has diplomatic immunity
• Also used to dealing with sovereign states,
  national telco regulators, governments, etc
• Delegations only proceed if ITU says so
• ITU has effective administrative control over the
  contents of e164.arpa

22
ITU Interim Procedure

• Anyone can submit a delegation request
• To ITU or RIPE NCC or both
• ITU sends request to official government contact
  for the country concerned
• Government says yes or no
• Response is relayed to RIPE NCC
• Delegation made or rejected as appropriate
• Result is no delegations get made without
  government approval
• National interests safeguarded
• E.164 integrity protected

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ENUM at ITU - 1

• IAB/IETF Tier-0 domain name is not endorsed by
  ITU
• Other TLDs under consideration
• Some countries perceive .arpa to be controlled by
  the US Government
• Cant have an international resource under the
  control of one state as a matter of principle
• On-going discussion within ITU
• ITU documents on ENUM deliberately do not mention
  the name of the ENUM root domain
• Will do so once consensus is reached inside ITU
• Hopefully that will be e164.arpa, but this cant
  be assumed
• Some member states want Tier-0 to be totally
  under the control of ITU

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ENUM at ITU - 2

• General acceptance of a golden tree
• Some ITU member states just dont want that
  golden tree to be under e164.arpa
• Current ITU process is an interim procedure
• Allow ITU more time to reach consensus
• Enables those countries wanting to carry out
  trials
• Pragmatic approach
• Trials can proceed for those who want them
• Final decision from ITU can be deferred until
  consensus is reached

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Getting an ENUM Delegation

• Follow the advice on the RIPE web site
• http//www.ripe.net/enum/instructions.html
• Submit the request to RIPE NCC
• Published on their web site and mailing list
• Forwarded to ITU for checking and government
  approval
• Response from ITU also published by RIPE NCC
• If approved, submit required templates to get the
  delegation from e164.arpa

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Introduction to ENUM
THANK YOU abuqayyas_at_itu.int ITU BDT