An Acronym

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Bob Leafloor TSACC October 23th, 2001
ENUM
An Acronym?
An important integrator of the PSTN and the
Internet, or even all Networks
Definitely!
An Abbreviation?
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What is ENUM?

• What is ENUM
• How ENUM Works
• How ENUM is being Implemented
• Canadian Solution

• What is ENUM

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What is ENUM?

• ENUM is a protocol developed by the IETF (RFC
  2916) that enables
• network elements to find services on the Internet
  using only a telephone number
• telephone services which have typically only 12
  input keys (0 through 9, plus and the
  sign) to access Internet services
• subscriber defined preferences for incoming
  communications

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How ENUM Works

• What is ENUM
• How ENUM Works
• How ENUM is being Implemented
• Canadian Solution

• How ENUM Works

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ENUM 3 Step Process

• Transform the telephone number into an ENUM DNS
  name
• Query the DNS to resolve that name and retrieve
  information (NAPTR RRs) that have been associated
  with the telephone number
• Choose a service from the DNS NAPTR response on
  the various types of services (including order
  preference) associated with the telephone number

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1. Transform the telephone number into a DNS name

• To transfer an E.164 number into a ENUM DNS name
• Reverse the digits
• Separate the digits with dots, i.e., .
• Add the ENUM domain name at the right end

• For example, for the TSACC Secretariat

1-613-946-1379
9.7.3.1.6.4.9.3.1.6.1.e164.tld
(e164.tld is a generic representation of the ENUM
domain)
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2. Query the DNS using that name
Suppose I want to email Dave Clemis while on
travel status but cant remember if his address
is clemis.dave_at_ic.gc.ca or clemis.david_at_ic.gc.ca
Assume my Outlook has an ENUM add-on, I
just send the email to his phone number 1 613
990-4236 The ENUM add-on queries the DNS ENUM
database for the NAPTR records associated with
Daves phone number
1 613 946-1379
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3. Choose a service from the DNS response
The ultimate choice of contact rests with the
sender
Choose
Choice
Query
ENUM Database
NAPTR
The result of an ENUM DNS query is the NAPTR
records, which specify the alternative methods of
contact with their order of processing and
preference
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How ENUM is being Implemented

• What is ENUM
• How ENUM Works
• How ENUM is being Implemented
• Canadian Solution

• How ENUM is being Implemented

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Global-Tree vs. Competitive-Tree

• The ITU and the Internet Society (ISOC) are
  working on a global-tree implementation of ENUM
  using a tiered architecture that will provide for
  a competitive implementation
• There will be other private and perhaps global
  competitive-tree implementations such as
  NetNumbers ENUM, see http//www.netnumber.com/n
  ews/10-9-01Verisign.pdf

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Global-Tree

• The ITU/ISOC Global-Tree will be a top rooted,
  global DNS distributed and delegated, ENUM
  implementation
• Member States would have the choice of opting in
  or out of this implementation
• Each ITU Member State may administer their
  portion of E.164 resources mapped into DNS as
  they see fit

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Global-Tree Tier-0

• The Global-Tree domain name space will be
  organized in tiers, likely three tiers 0, 1, and
  2
• Tier-0, the ENUM domain name space root, would be
  administered by the ITU-TSB
• The ITU-TSB would delegate operational control of
  Tier-0 to some other entity
• Countries would opt-in or opt-out at the Tier-0
  level
• The Tier-0 name server would have NS records
  for the Tier-1 name servers of the opted-in
  countries

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Global-Tree Tier-0

• To support geographically dispersed national
  resources, the ENUM root zone (e164.tld) for the
  Global-Tree requires a DNS backbone dispersed
  around the world
• Main ENUM name servers (e.g., root zone CC) may
  need to be capable of sustaining loads probably
  comparable to that carried by current root name
  servers

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Global-Tree Tier-0
e164.arpa is rooted in all the gtld.servers
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Global-Tree Tier-1/Tier-2

• The organization below Tier-0 for countries
  opting-in would be their responsibility
• This would include
• Administration
• Operation
• Competition
• Privacy/Security, etc.

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Global-Tree Tier-1/Tier-2

• Country Code 1 (CC 1) being integrated is a
  special case
• If the NS delegation from Tier-0 for CC 1 is at
  the 1 level then it needs to point to a single
  Tier-1 name server for all of CC 1
• This would require agreement of all CC 1 members
• The 1 approach allows geographic and
  non-geographic NPAs to be treated the same way

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Global-Tree Tier-1/Tier-2

• If the NS delegation from Tier-0 for CC 1 is at
  the 1NPA level then there can be multiple
  Tier-1 name servers, each responsible for one or
  more NPAs (area codes)
• The 1NPA approach could facilitate national
  ENUM control of assigned geographic area codes,
  but non-geographic such as 1800 , 1888
  would require special consideration

An example of 1NPA.
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Global-Tree Tiered Structure
9 . 7 . 3 . 1 . 6 . 4 . 9 . 3 .1 . 6 . 1 . e164 .
tld
Registry
Registry
Provider
Tier-0
Tier-1
Tier-2
Directs the DNS query to the countries Tier-1
registries An NS record is provided for each
Tier-1 1NPA registry
Stores a list of service specific internet
addresses in the form of URIs in a DNS resource
record called NAPTR for each subscriber Returns
the full list of Internet addresses associated
with the E.164 number being queried.
Directs the DNS query to the customers Tier-2
providers An NS record is provided for each
subscribers telephone number
National
ITU
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Global-Tree Tiered Structure
ENUM Tier-0
Specific 1NPA Delegations


ENUM Tier-1 Registry for specific NPAs
of Country Code 1
ENUM Tier-1 Registry for specific NPAs
of Country Code 1
Tier-2 Provider
Tier-2 Provider
Tier-2 Provider
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Global-Tree US Approach

• The US supports both the Global-Tree and
  Competitive-Tree approaches
• The US ENUM Forum will be recommending the US
  approach to the ENUM Global-Tree implementation
• US ENUM Forum includes groups on
• Architectural Infrastructure
• Provisioning
• Applications
• Security Privacy
• Interworking (with other trees)
• Legal Experts

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ENUM

• What is ENUM
• How ENUM Works
• How ENUM is being Implemented
• Canadian Solution

• Canadian Solution

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Canadian Solution

• There is a need to participate in ITU-T SG2 ENUM
  activities and develop opinions and contributions
  as required on
• Draft Recommendation E.A-ENUM (Tier-0)
• Draft ENUM Supplement (Tier-1/2 Guidelines)
• Selection of the ENUM Domain

In addition effort is required on . .
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Canadian Solution

• Determining and recommending how ENUM should be
  implemented in Canada including
• The Tier-1/2 structure, administration, and
  operation Location requirements (if any) for
  Tier-1/2 operators
• Interfacing with other members of CC 1 on
  implementation
• How 1800 etc., for Country Code 1 should be
  handled
• How to keep ENUM transparent to NANP/NANPA
  issues and vise versa
• DNS security requirements for ENUM
• Privacy, Confidentiality, Integrity,
  Availability, and Identification and
  Authentication requirements for ENUM
• What threats and vulnerabilities may ENUM be
  subject to
• Considerations concerning competitive-trees

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Canadian Solution

• Agreed Interested Parties Approach
• Establish a dual-role single-group under TSACC
  which would
• Determine and recommend to TSACC on how ENUM
  should be implemented in Canada
• Report to the CNO/ITU Steering Committee on SG2
  matters including ENUM

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Thank You

• References and resources
• One-Stop Shopping at

http//tsacc.ca/enum.htm
An annex follows with additional information
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ENUM
Annex
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Terminology
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Terminology
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Terminology
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NAPTR format
Query 6.3.2.4.0.9.9.3.1.6.1.e164.tld
ResponseORIGIN 6.3.2.4.0.9.9.3.1.6.1.e164.tld
IN NAPTR 10 10 "u" "mailtoE2U
!.!mailtoleafloor.bob_at_ic.gc.ca!

• IN NAPTR Internet class, NAPTR type
• 10 10 Order and Preference are both equal and
  low value. Low numbers are processed before high
  numbers. Preference is subordinate to Order
• u This flag states that the Rule is terminal
  and that the output is a URI which contains the
  contact information
• "mailtoE2U The service is E.164 to URI, the
  access protocol is SMTP mail
• URI is mailtoleafloor.bob_at_ic.gc.ca

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NAPTR format
Query 6.3.2.4.0.9.9.3.1.6.1.e164.tld Response
ORIGIN 6.3.2.4.0.9.9.3.1.6.1.e164.tld
IN NAPTR 10 20 "u" "mailtoE2U
!.!mailtoleafloor.bob_at_ic.gc.ca! IN NAPTR 50
10 "u" telE2U !.!tel[phone]! IN
NAPTR 50 50 "u" telE2U !.!tel[phone]!

• Extraction
• Email to leafloor.bob_at_ic,gc,ca has highest order
  and is therefore the recipients first choice
  overall
• Office phone number 1 613 990-4236 and cell phone
  number 1 613 220-9890 have the same order. This
  order is lower than the email order and is
  therefore the recipients second choice
• The office phone number has a higher preference
  to the cell phone number and should be selected
  first

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NAPTR format

• Choice
• The recipient has indicated three methods of
  contact, in the following prefered order
• Email leafloor.bob_at_ic,gc,ca
• Phone [phone]
• Phone [phone]
• The ultimate choice rests with the originator,
  for example if the originator wanted to use a
  phone the choice should be 2.

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Names versus Addresses

• An address is how you get to an endpoint
• Typically, hierarchical (for scaling)
• 300 Slater Street, Ottawa, Ontario K1A 0C8
• 204.152.187.11, 1-613-946-1379
• A name is how an endpoint is referenced
• Typically, no structurally significant hierarchy
• David, Ottawa, tsacc.ca

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The DNS is

• Comprised of three components
• The name space
• Name Servers
• Resolvers which query the name servers about the
  name space

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The Name Spaceor Domain
ca domain

• A potential ca domain and ca zone for Canada.
  Note that in the example the sub-domains for
  British Columbia and Saskatchewan are not
  delegated, and those for Alberta, Ontario and
  Quebec are.

ca zone
ab.ca zone
qc.ca zone
on.ca zone
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Name Servers

• Name server act as
• A database server, answering queries about the
  parts of the name space it knows about
• A cache, temporarily storing data it learns from
  other name servers, and
• An agent, helping resolvers and other name
  servers find data that other name servers know
  about

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Name Resolution

• Name resolution is the process by which resolvers
  and name servers find data in the name space
• A name server knowing only the names and IP
  addresses of the root name servers can find
  information anywhere in the name space
• The root name servers know about the top-level
  zones and can tell other name servers whom to
  contact next

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Name Resolution

• A DNS query has three parameters
• A domain name (e.g., www.ic.gc.ca),
• A class (e.g., IN for Internet), and
• A type (e.g., A for Address)
• A name server receiving a query from a resolver
  looks for the answer in its authoritative data
  and its cache
• If the answer isnt in the cache and the server
  isnt authoritative for the answer, the answer
  must be looked up

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What can be Resolved?

• Any name in the name space
• Class
• Internet (IN), Chaos (CH), Hesiod (HS)
• Type
• Address (A, AAAA, A6)
• Pointer (PTR, NAPTR)
• Aliases (CNAME, DNAME)
• Security related (TSIG, SIG, NXT, KEY)
• Etc.

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Registries, Registrars, and Registrants

• Registry
• the name spaces database
• the organization which has control of that
  database for editing, dispute resolution,
  policies, etc.
• the organization which operates or delegates the
  authoritative name servers for that name space
• Registrar
• an agent which submits change requests to the
  registry on behalf of the registrant
• Registrant
• the entity which makes use of the domain name

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Registries, Registrars, and Registrants
Zone DB