Introduction to ENUM Technical and Operational Aspects

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Introduction to ENUM Technical and Operational
Aspects

• Austrian ENUM Forum February 11, 2002
• Richard STASTNY
• ÖFEG, Postfach 147, 1103-Wien
• Tel [phone]Fax [phone]E-Mail
  richard.stastny_at_oefeg.atrichard_at_stastny.com

ÖFEG
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Was ist ENUM?
Die letzte Entscheidung liegt beim Sender
Wahl
Auswahl
Nummer
ENUM DNS
Kontakte
Das Ergebnis einer ENUM DNS Abfrage sind Daten,
die alternative Kontaktmethoden und die
bevorzugte Reihenfolge angeben
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Contents

• What is ENUM?
• Convergence between IP and E.164 based networks
• Introduction to DNS
• ENUM technical aspects
• ENUM architectural/operational aspects
• ENUM alternative implementations
• International Status

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The Starting Point Questions ENUM looked to
answer

• How do you find services on the Internet if you
  only have a telephone number E.164?
• How to enable new IP services while creating new
  competitive markets and protect consumer
  choice,etc?
• How can consumers and carriers have equal access
  to these new opportunities?
• How do we create a trusted TN based resource for
  information about those services?
• How do you make this simple, easy to use, without
  reinventing the wheel?

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Some early answers from the IETF

• Use the DNS it works... Its global...It
  scales..etc.
• Telephone Number in URI out
• RFC2916 was developed by the IETF to define the
  use of DNS resource records to find optional
• E-mail addresses
• Voice over IP SIP / H.323 servers
• Voice Mail servers
• Fax Machines
• New and yet undefined services !

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ENUM in the context of convergence (I)

• ENUM is an enabler of the convergence process
  between E.164 based networks (PSTN, GSM, ect.)
  and IP based networks providing interoperability
  between different naming/addressing schemes
  across different networks
• ENUM offers the possibility to have a single
  contact point (E.164 number) for different
  services across different networks

ENUM

• 350 Million Internet users worldwide

• 1.2 Billion telephone numbers worldwide

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ENUM in the context of convergence (II)

• ENUM is.
• A bearer capability that allows the mapping an
  E.164 number into a set of IP terminations and
  associated protocols by using DNS technology
• ENUM is not .
• A telecommunication service/application
• A carrier selection mechanism
• A directory service
• A threat/replacement of existing E.164 numbering
  plans

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Introduction to Domain Name System (DNS)

• DNS is the mechanism that allows to translate
  user-friendly names (e.g. neustar.biz) into
  network oriented addresses (e.g. 192.23.23.193)
  and vice versa
• Address and name have different functions. An
  address is a locator and name is an identifier
• DNS is a world-wide distributed, scalable,
  reliable, dynamic database
• Data are stored locally but can be retrieved
  globally
• Domain name (neustar.biz, 1.2.3.4.5.67.4.4
  .e164.arpa) is the key to retrieve data
• DNS is composed of three main elements
• Domain name space
• Name servers
• Resolvers

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The Domain Namespace (I)

• The namespace is the skeleton of DNS database
• An inverted tree with the root node at the top
• Each node has a label. The root has an empty
  label
• A domain name is the sequence of labels from a
  node to the root separated by .
• A domain name is unique and identifies the
  position of the correspondent node in the
  namespace

trial.enum.neustar.biz
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The Domain Namespace (II)

• A subdomain is a portion of a domain
• Ex enum.neustar.biz is a subdomain of
  neustar.biz
• A domain can be split in a number of
  administrative independent subdomains called
  zones
• Delegation is the process to create zones that is
  a mechanism to decentralize control

Below neustar.biz there are two (child) zones
enum.neustar.biz (orange) and us.neustar.biz
(green)
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Name Servers and Resolvers (I)

• Name resolution is a server/client mechanism to
  find data in the DNS
• Name server is the server half of the
  mechanism. The resolver is the client half
• Name server is a program storing information
  about a zone (zone file)
• The name server that stores a complete zone is
  authoritative for the zone
• More than one name server are authoritative for
  the same zone
• redundancy and robustness
• In addition to authoritative name servers there
  are also caching name servers that store only
  part of zone file data

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Name Servers and Resolvers (II)

• Resolver is a program running on a host that
  queries from information
• A name server receives a query from a resolver
  and looks for the answer
• 1) search starts from authoritative data and then
  its cache
• 2) if the name server doesnt have the requested
  data and is not authoritative for that domain,
  the request is passed to other name servers with
  a recursion process

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Whats ENUM (I)
ENUM is about E.164 numbers into DNS by using a
single, authoritative structured domain -
e164.arpa

• E.164 numbers because
• They have been used for years in telephony, are
  authoritatively managed and well accepted by
  users
• Other numbers/identifiers (E.212, car number
  plate) could be used as entries for DNS look up
  but its not ENUM
• DNS because.
• Its available, global, cheap, reliable, scalable

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Whats ENUM (II)

• A single, authoritative structured domain
  because
• Its crucial to ensure the integrity of the E.164
  numbering plan
• Its vital to protect customers from traffic
  hijacking and privacy violation
• DNS is not a directory service. Consistency of
  the information retrieved by DNS look up (the
  same information irrespective of the location of
  the DNS query)
• E164.arpa because.
• .arpa is the TLD designated by the IAB for
  Internet Infrastructure issues e.g. in-addr.arpa
  (reverse IP address look up)
• .arpa is available today, well managed, stable
  and secure with operational environment under
  IAB/IETF supervision

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ENUM technical description (I)

• ENUM is a protocol defined in IETF RFC 2916 that
  allows
• Mapping of a E.164 number into a fully qualified
  domain name belonging to a single, authoritative
  and structured subdomain (e164.arpa)
• Retrieval of URIs in DNS by using E.164 fully
  qualified domain name as entry
• Mapping E.164 international number into DNS
• Remove all characters with exception of the
  digits (e.g. )
• Insert a . between each digit
• Reverse the order of the digits and append
  .e164.arpa to the end
• Example 44207868-8581 ?1.8.5.8.8.6.8.7.0.2.4.4.e1
  64.arpa

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ENUM technical description (II)

• NAPTR Records
• NAPTR Records are DNS resource records (defined
  in IETF RFC 2915) that indicate the
  protocols/services associated to the E.164 domain
  name
• One or more URIs as result of the DNS look up.
  Order and preferences can be indicated
• Example
• ORIGIN 4.3.2.1.6.7.9.8.6.4.e164.arpa.
• IN NAPTR 100 10 "u" "sipE2U"
  "!.!sipinfo_at_tele2.se!" .
• IN NAPTR 102 10 "u" "mailtoE2U"
  "!.!mailtoinfo_at_tele2.se!" .

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ENUM architecture (I)

• ENUM is a based on a layered architecture to
  follow DNS hierarchy and ensure proper
  competition
• Three layers Tier0, Tier1 and Tier2
• Tier0 functions ltgt Administration and technical
  management of ENUM domain
• Tier 0 Registry is an international registry
  containing pointers to authoritative national
  registries (Tier1 Registries)
• Tier1 functions ltgt Management and operation of
  ENUM in the country (or portion of it) identified
  by a Country Code
• Tier1 Registry is a national registry containing
  pointers to authoritative name servers where
  NAPTR records are stored (Tier2 Registries)

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ENUM architecture (II)

• Tier2 functionsltgt Provision of ENUM service
• Tier2 Registry stores the NAPTR records
  associated to an E.164 number
• Tier2 Registrar is the commercial interface with
  the ENUM subscriber and it is involved in the
  validation process (E.164 number, user identity)
• Tier0 and Tier1 are natural monopolies, Tier2 is
  open to competition
• How Tier1 and Tier2 functions are implemented is
  a national matter

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ENUM architecture (III)
Tier0
Tier0 Registry e164.arpa
DNS zone delegation for CC
Tier1
Tier 1 Registry CC.e164.arpa
DNS zone delegation for individual number
serviced by Tier2 Registry
Tier2

• Its not a business model

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ENUM Alternative implementations (I)

• Ongoing discussions between ITU and IAB/IETF to
  agree upon the ENUM TLD and delegation model
• Crucial that ENUM implementations follow the
  ITU/IAB/IETF agreement
• Today ENUM-like alternative implementations are
  already available
• Creation of multiple conflicting trees (e164.com,
  e164.net, ..)
• Threats/challenges posed by multiple conflicting
  trees
• Integrity of E.164 numbering plans
• Lack of consistency of data in ENUM databases
• Search in multiple branches
• Lack of common rules to protect E.164 customers
  and network operators rights
• Privacy, data protection, QoS, traffic hijacking

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ENUM Alternative implementations (II)

• Multiple conflicting ENUM trees must not
  encouraged
• ENUM developments cannot be only left to market
  forces

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What is still at issue?

• Not the technical underpinnings
• No substantial argument with the technology
  identified in RFC 2916
• At issue are the implementation details
• These are now being addressed by
• - IETF/ITU
• - various regions/countries

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Some agreements

• Agreement on delegation model that completely
  follows the ITU-T E.164 plan for inclusion in the
  agreed zone
• E164. geographic zones controlled by appropriate
  Member State.
• ITU will insure that Member States have
  authorized the inclusion of their Country Code in
  ENUM DNS zone
• ITU will coordinate with the agreed Root
  Administrator

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Background of ITU ETSI documents
Timing has dictated
SG2 Genv
1 2 3 4 5 6 7 8
9 10 11 12 1 2 3 4
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2001
2002
US SG-A
US ENUM FORUM
Sweden
France
UK
NL
A
Some examples of national activities
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ITU-T Supplement

• Supplements are
• purely informative
• not an integral part of any Recommendation
• they do not imply agreement

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ITU-T Supplement on operational and
administrative issues associated with ENUM

• Provides an overview of concepts
• Describes issues that need to be addressed by
  Administrations as they consider the inclusion of
  numbers within the DNS which are under their
  jurisdiction
• Also covers issues that need to be addressed by
  stakeholders of shared country codes e.g. codes
  for Networks and Global Services

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ITU Draft Recommendation Principles Procedures
for Administration of E.164 CCs

• ITU has responsibility for Administrative
  control of CCs
• Recommendation defines principles procedures
  for assignee to register a CC domain at the ENUM
  root level in the DNS
• Recognises Subsequent levels are national matters
  (guidance on this will be in the ITU Supplement)
• Doesnt cover technical operation of the DNS

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ETSI Technical Specification
Aim To provide basic set of principles that
should be adhered to in order to maximise
potential benefits from publicly available ENUM
implementations within Europe Efforts at drawing
together a a co-ordinated approach should not
only result in a firm foundation for ENUM
activities within the European environment but
should also assist in enhancing the competitive
communications environment
The importance of gaining the support or all
relevant parties was recognised as a prime
requirement
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Emerging principles within Europe

• E.164 integrity must be maintained
• Compliance with Data Protection Directives
• Adherence to ITU Recommendations and IETF
  Specifications
• Compliance with National Regulatory requirements
• Must facilitate a competitive environment
• Must be user Opt in
• Existing network functions must not be
  compromised e.g. Number Portability, Carrier
  Selection

All provide good safeguards
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Major Issues of concern

• Provisioning based on false information by users
• Authentication and validation requirements
• Abuse of data stored
• Regulatory requirements
• Alternative ENUM implementations
• .and more!

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What still needs to be done?

• Administrations must be encouraged to actively
  consider national implementation aspects
• The ETSI Framework document needs to be completed
  and formally agreed
• Issues surrounding the choice of gTLD must be
  resolved URGENTLY!
• All effort must be put into completion of the ITU
  studies to facilitate the insertion of Country
  Codes within the DNS
• A better understanding of ENUM needs to be
  promulgated through the ONP Experts Committee

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Acronyms
ARPA Advanced Research Project
Administration DNS Domain Name
Server ENUM Electronic NUMbering IAB Internet
Architecture Board IETF Internet Engineering
Task Force IP Internet Protocol ITU Internationa
l Telecommunication Union NAPTR Naming Authority
Pointer Record in a DNS RFC Request For
Comments PSTN Public Switched Telephone
Network SIP Session Initiation Protocol TLD Top
Level Domain URI Uniform Resource Identifier
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Weitere Informationen

• IETF www.ietf.org
• ITU-T www.itu.int
• ETSI www.etsi.org
• ENUM Forum www.enumf.org
• Neustar www.enum.org
• teleDNS www.enumworld.com
• Netnumber.com www.netnumber.com

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Ende

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