Download ENUM Technical Issues/DNS, Mr. Patrik Fältström

ENUM
Technical issues / DNS
Patrik Fältström
Area Director, Applications Area, IETF
[email protected]
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Agenda
• Background
• Problem we want to solve
• Technical solution
• Conclusion
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Background
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The Domain Name System
• It is a distributed database
• It is a protocol
• Often the two get mixed up
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DNS as distributed database
Central server,
“root server”
Server for
“com”
Server for
“se”
Local
resolver
Client
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Server for
“jp”
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Recursion
Root-server
Query
a.paf.se?
Query
a.paf.se?
Server
“se”
Query
a.paf.se?
Ask “paf.se”!
Query
a.paf.se?
192.168.1.11
Local
resolver
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Ask “se”!
192.168.1.11
Server
“paf.se”
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Domains and zones
"root"
se
c
ns
zone "a.se."
b
domain "a.se."
domain/zone "b.a.se."
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a
ns
ns
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Delegations
Root server
se. IN NS ns.nic-se.se
ns.nic-se.se. IN A 192.168.0.1
ns.nic-se.se
ns.se. IN NS ns.nic-se.se.
a.se. IN NS ns.a.se.
c.se. IN NS ns.c.se.
ns.nic-se.se. IN A 192.168.0.1
ns.a.se. IN A 192.168.1.1
ns.c.se. IN A 192.168.3.1
ns.a.se
a.se. IN NS ns.c.se.
b.a.se. IN NS ns.b.se.
ns.a.se. IN A 192.168.1.1
ns.b.se. IN A 192.168.2.1
ns.c.se.
c.se. IN NS ns.c.se.
ns.c.se. IN A 192.168.3.1
ns.b.a.se.
b.a.se. IN N S ns.b.a.se.
ns.b.a.se. IN A 192.168.3.1
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E.164 numbers
• Allocation at CC level by the ITU,
SG2/WP1/2 (from an IETF perspective)
• E.164 provides the number structure and
functionality of numbers used for
international public
• telecommunicationsHierarchically
allocated
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Structure of E.164
• Structure to use for geographic areas
CC
NDC
SN
1-3 digits
N digits
Max (15-N) digits
National (significant) number
International public telecommunication
Number for geographical areas
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Problem we want to solve
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Problem statements 1(2)
• How do network elements find services on
the Internet if you only have a telephone
(E.164) number?
• How can subscribers (as opposed to
carriers) define their preferences for
incoming communications?
• How can we (IETF/ITU) enable new
services while enabling competition,
consumer choice and consumer
protection?
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Problem statements 2(2)
• How can consumers, carriers and
new players have equal access to
these new opportunities?
• How do we (IETF/ITU) make this
simple and easy to use without
reinventing the wheel?
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Technical solution
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Solution in short
• Put telephone numbers* in the global
domain name system, DNS
• ENUM Working Group created to solve the
problem of using the DNS for:
Domainname in
[Numbers reformatted as domain names]
URI out
[mailto, sip, tel, http or other URI scheme]
• Solution was to use NAPTR records
* Maybe not in the original E.164 format
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Example
• $ORIGIN 4.3.2.1.7.9.8.6.4.e164.arpa.
IN NAPTR 10 10 "U" "sip+E2U"
"!^.*$!sip:[email protected]!"
IN NAPTR 20 10 "U" "ldap+E2U"
"!^.*$!mailto:[email protected]!"
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Why DNS?
• It’s there
It works… It’s global… It scales… It’s fast… It’s
open…
• Grandfather existing DNS delegation
mechanisms, which looks like delegation
in E.164 world
• ENUM enabled DNS provides a low cost,
shared SCP-like infrastructure for IP
infrastructure
• ENUM facilitates PSTN/IP convergence
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Step 1
• Take an E.164 number and create a fully
qualified domain name in a single highly
defined and structured domain
• +46-8-971234
• +468971234
The input to the
NAPTR algorithm
• 4.3.2.1.7.9.8.6.4.e164.arpa.
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Step 1 Explanation
• Each digit becomes a definable and
distributed “zone” in DNS terms
• Delegation can (doesn’t have to) happen
at every digit, including at last digit
• Zones such as country codes, area codes
or primary delegated blocks of numbers
can be delegated as well as individual
numbers
• DNS defines authoritative nameservers for
NAPTR/service resource records (RR’s)
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Step 2
• Lookup NAPTR RR’s in DNS, and apply
NAPTR/ENUM algorithm
• 4.3.2.1.7.9.8.6.4.e164.arpa.
• !^.*$!mailto:[email protected]!
!^+46(.*)$!ldap://ldap.telco.se/cn=0\1!
• Use rewrite rules using regular
expressions which operate on the E.164
number (+468971234)
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Regular expressions
• For ENUM, the NAPTR regexp field
may yield an (unchanged) URL
• !<regexp>!<string>!
“Match <regexp> on original E.164, and
apply rewrite rule <string>”
^ - Match beginning
$ - Match end
. - Match any character
.* - Match any number of any character
() - Grouping, \n in <string> is replaced
with group number ‘n’ in <regexp>
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Step 2 in detail
• $ORIGIN 4.3.2.1.7.9.8.6.4.e164.arpa.
• IN NAPTR 10 10 “U” “mailto+E2U”
“!^.*$!mailto:[email protected]!”
• IN NAPTR 20 10 “U” “ldap+E2U”
“!^+46(.*)$!ldap://ldap.telco.se/cn=0\1”
• Note that no line break should be in the
records
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ENUM DNS Hierarchy
Alternative 2
1
e164.arpa
6.4.e164.arpa
7.9.8.6.4.e164.arpa
4.3.2.1.7.9.8.6.4.e164.arpa
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+46-8-976123
Root server
e164.arpa. IN NS. ns.ripe.net
ns.ripe.net. IN A 193.0.0.193
ns.ripe.net
e164.arpa. IN NS ns.ripe.net.
6.4.e164.arpa. IN NS ns.e164.se.
ns.ns.e164.se. IN A 192.168.0.1
ns.e164.se
6.4.e164.arpa IN NS ns.e164.se.
7.9.8.6.4.e164.se. IN NS e164.telco.se.
e164.telia.se. IN A 192.168.1.1
e164.telco.se.
7.9.8.6.4.e164.se. IN NS e164.telco.se.
3.2.1.6.7.9.8.6.4.e164.arpa. IN NS ns.eservice.net.
ns.eservice.net.
3.2.1.6.7.9.8.6.4.e164.arpa. IN NS eservice.net.
3.2.1.6.7.9.8.6.4.e164.arpa. IN NAPTR …….
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DNS Hierarchy
• Strictly delegated
• One authoritative server for each
name, and only one
Have led to the registry/registrar model
• One responsible registry, but many
registrars which talk with customers
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Registry/registrar
Root server
Server for .com
Verisign Global Registry
Server for .se
NIC-SE AB
Registrar for .com
interQ Incorporated
Registrar for .se
Tele2
Registrars for .se
Today 227
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Registrar for .com
Network Solutions
Registrar for .com
Active ISP
Registrars for .com
Today 77
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Conclusion
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ENUM example flow/usage
DNS-Server
Query
4.3.2.1.7.9.8.6.4.e164.arpa?
Response
sip:[email protected]
“Call setup”
Dial
+468971234
Sip
sip:[email protected]
Sip proxy
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Sip proxy
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ENUM and VoIP
• ENUM allows VoIP proxies and servers to
find each other
Intra and inter domain call setup
Only for declaring ability to accept certain
applications
• ENUM is an opt-in system (also on country
code level)
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ENUM in Universal Messaging
• IETF Voice Profile for Internet Mail
• ENUM enables carrier and enterprise voice
mail systems to find each other,
interoperate and exchange messages
• Linkage to directory gives access to
“spoken name” as well as authenticated
access to sensitive information (privacy)
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ENUM in Internet Fax
• IETF RFC 2305 / ITU-T Rec. T.37
• ENUM enables internet aware fax
machines to find each other,
interoperate and exchange messages
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Detailed example of Fax
• Person X wants to send a fax to Person Y; she knows Y's E.164
number.
• Person Y has many IP applications tied to her own (Y's) E.164
number.
• Device C became responsible for delivering the fax. Device C is
Internet Aware, is ENUM-enhanced, can do SMTP and SIP, but
can't do H.323 yet.
• Device C does a DNS query on the E.164 number. Device C
discovers from the response that Person Y prefers real-time to
store-and-forward fax delivery, likes SIP and H.323 equally, and
has SMTP, too.
• Device C tries SIP first. If SIP fails, Device C does not try H.323.
Instead, Device C then tries SMTP.
• Note: Device C uses ENUM in its application selection logic.
ENUM is an enabler and not the same sort of thing as SMTP, SIP,
H.323, voice/fax/data, etc.
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From RFC 2916
• 4. IANA Considerations
• This memo requests that the IANA delegate the
E164.ARPA domain following instructions to be
provided by the IAB. Names within this zone are to be
delegated to parties according to the ITU
recommendation E.164. The names allocated should
be hierarchic in accordance with ITU Recommendation
E.164, and the codes should assigned in accordance
with that Recommendation.
• Delegations in the zone e164.arpa (not delegations in
delegated domains of e164.arpa) should be done after
Expert Review, and the IESG will appoint a designated
expert.
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Status as of Jan 10, 2001 (done)
• Base spec published as RFC 2916
• e164.arpa delegated to RIPE-NCC
• ITU SG2/WP1/2 liaison statement:
Member state can inform ITU on entry of
numbers in DNS, provision of E.164
information
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Status as of Jan 10, 2001 (not done)
• Delegation of domains below
e164.arpa to managing entities that
are appointed by member states
• National issues
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Resources
• NAPTR Resource Records (RFC 2915)
http://www.ietf.org/rfc/rfc2915.txt
• ENUM Specification (RFC 2916)
http://www.ietf.org/rfc/rfc2916.txt
• Liaison Statement (RFC 3026)
http://www.ietf.org/rfc/rfc3026.txt
• IAB on need for unique root (RFC 2826)
http://www.ietf.org/rfc/rfc2826.txt
• IAB Statement on ARPA
http://www.iab.org/iab/DOCUMENTS/statement-on-infrastructuredomains.txt
• My email address: [email protected]
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