An IETF view of ENUMAn IETF view of ENUM

Geoff HustonGeoff HustonExecutive Director,Executive Director,

Internet Architecture BoardInternet Architecture Board

Who is the IETF?Who is the IETF?

Internet Engineering Task ForceInternet Engineering Task Force The organization that oversees the The organization that oversees the

standards process for Internet protocols standards process for Internet protocols and technologiesand technologies

Industry-based standards body with broad Industry-based standards body with broad participation from vendors, operators and participation from vendors, operators and researchersresearchers

We make standards that work – how you We make standards that work – how you work them is up to you!work them is up to you!

The Structure of the IETFThe Structure of the IETF

Huh? - Lets see that again!Huh? - Lets see that again!

Internet Society

IESGIAB

RFC Editor IANA Areas (7)

Working Groups

IETF

IRTF

How does the IETF Work?How does the IETF Work?

We do not believe in Kings, Presidents and We do not believe in Kings, Presidents and Voting. We believe in rough consensus and Voting. We believe in rough consensus and running coderunning code

Dave Clark, MIT, Former IAB memberDave Clark, MIT, Former IAB member

The IETF has a focus on developing standards where The IETF has a focus on developing standards where interoperability testing of conformant implementations of the interoperability testing of conformant implementations of the standard, and use of the technology in production contexts form standard, and use of the technology in production contexts form an integral part of the standards processan integral part of the standards process

How Does the IETF Work?How Does the IETF Work?

Proposed work items are aired at a BOF Proposed work items are aired at a BOF sessionsession• Gather interest and supportGather interest and support

A work program is chartered by the IESG A work program is chartered by the IESG • Working Group CharterWorking Group Charter

• WG Chair(s) and Area DirectorWG Chair(s) and Area Director• Working Group statement of activityWorking Group statement of activity• Schedule of milestonesSchedule of milestones

• Periodic IESG review and recharter as Periodic IESG review and recharter as necessarynecessary

IETF DocumentsIETF Documents

Internet DraftsInternet Drafts

• http://www.ietf.org/1id-abstracts.htmlhttp://www.ietf.org/1id-abstracts.html• Individual submissionsIndividual submissions

• draft-<person>-<header>draft-<person>-<header>• Working Group DocumentsWorking Group Documents

• draft-ietf-<working group>-<header>draft-ietf-<working group>-<header>• Working Group documents denote some level of ‘buy-in’ Working Group documents denote some level of ‘buy-in’

from the community of interestfrom the community of interest

IETF DocumentsIETF Documents

RFCsRFCs• InformationalInformational• Best Current PracticeBest Current Practice• Standards TrackStandards Track

• Proposed (good idea, clearly written, Working Group Proposed (good idea, clearly written, Working Group approved, peer reviewed)approved, peer reviewed)

• Draft (interoperability tested, sound idea)Draft (interoperability tested, sound idea)• Full (many people are / were using this technology)Full (many people are / were using this technology)• Historic (no longer that useful)Historic (no longer that useful)

ENUMENUM ENUM is a working group with the IETF Transport AreaENUM is a working group with the IETF Transport Area

ENUM (cont)ENUM (cont)

ENUM (cont)ENUM (cont)

Why ENUM?Why ENUM?

Because tpc.int did not work!Because tpc.int did not work!• tpc.int (c 1992) mapped E.164 numbers to A records (IP tpc.int (c 1992) mapped E.164 numbers to A records (IP

addresses) to emulate fax deliveryaddresses) to emulate fax delivery• Each new service required a new E.164 -> IP address Each new service required a new E.164 -> IP address

mappingmapping• Did not scale to multiple services using a single mappingDid not scale to multiple services using a single mapping

ENUM is part of a broader IETF approach of splitting ENUM is part of a broader IETF approach of splitting out the components of VOIP / PSTN interaction into out the components of VOIP / PSTN interaction into discrete efforts and addressing each component as discrete efforts and addressing each component as a discrete technology standardization efforta discrete technology standardization effort

ENUM is not an end in itselfENUM is not an end in itself

The Good Bits of ENUMThe Good Bits of ENUM

E164.arpaE164.arpa• Single mapping that is service independentSingle mapping that is service independent• Each mapping can be associated with a collection of URIsEach mapping can be associated with a collection of URIs• The mapping may be statically configured or dynamically The mapping may be statically configured or dynamically

generated (or both)generated (or both)• Each end point of the DNS hierarchy populates the entry Each end point of the DNS hierarchy populates the entry

with desired service entrieswith desired service entries• Each application selects compatible service entries from Each application selects compatible service entries from

the setthe set• ENUM is independent of directory, call control, routing ENUM is independent of directory, call control, routing

and transport considerationsand transport considerations• Its just a mapping from the E.164 domain into multiple Its just a mapping from the E.164 domain into multiple

URI service domainsURI service domains

The Not So Good BitThe Not So Good Bit

The DNS is an issue in all this……The DNS is an issue in all this……• DNS is insecureDNS is insecure

• TSIG, DNSSEC, PKI, etc may help, but when and how much?TSIG, DNSSEC, PKI, etc may help, but when and how much?• DNS is variably timedDNS is variably timed• DNS is generally not well maintainedDNS is generally not well maintained• DNS is generally not well synchronizedDNS is generally not well synchronized• There is no “DNS says ‘no’”, only an indistinct timeoutThere is no “DNS says ‘no’”, only an indistinct timeout• Putting regular expressions in the DNS is an fascinating complicationPutting regular expressions in the DNS is an fascinating complication• But we have nothing better in terms of a very large distributed But we have nothing better in terms of a very large distributed

database to poke towards this problem spacedatabase to poke towards this problem space

Remember:Remember:• The DNS is a lousy kitchen sink. We have seen many proposals to The DNS is a lousy kitchen sink. We have seen many proposals to

“just put in in the DNS”. Be very concerned whenever you hear this!“just put in in the DNS”. Be very concerned whenever you hear this!

ENUM is NOT everythingENUM is NOT everything

In particular, ENUM is NOT:In particular, ENUM is NOT:• a directorya directory• a search servicea search service• a transport servicea transport service• a voice encoding methoda voice encoding method• a rendezvous protocola rendezvous protocol

All ENUM is a distributed partial mapping All ENUM is a distributed partial mapping from E.164 addresses into a set of service from E.164 addresses into a set of service points identified via a URI labellingpoints identified via a URI labelling

The VOIP Gateway Model for The VOIP Gateway Model for enumenum

Most IETF work these days assumes a Most IETF work these days assumes a ‘reference architecture’‘reference architecture’

ENUM’s core reference architecture is ENUM’s core reference architecture is VOIP-to-VOIPVOIP-to-VOIP

PSTNPSTN

Internet

VOIP Server

VOIP Served subnet

Enum Service Point

The Gateway VOIP ModelThe Gateway VOIP Model

The single gateway model is simple:The single gateway model is simple:• A PSTN / IP gateway maintains a A PSTN / IP gateway maintains a

mapping between IP and E.164 mapping between IP and E.164 addressesaddresses

VOIPGateway

IP Net

PSTNPSTN

10.0.0.10 1234567810.0.0.11 1234567910.0.0.12 12345680

IP E.164

1. Call “12345678”

2. PSTN routes the call to 12345678 to the VOIP gateway

3. Gateway maps E.164 address “12345678” to IP 10.0.0.10

4. Gateway initiates a SIP session with 10.0.0.10

1234567810.0.0.10

The multi-Gateway VOIP The multi-Gateway VOIP WorldWorld

Use PSTN / VOIP GatewaysUse PSTN / VOIP Gateways• Each Gateway maps a set of telephone numbers Each Gateway maps a set of telephone numbers

to a set of served IP service addressesto a set of served IP service addresses• Each Gateway knows only about locally served Each Gateway knows only about locally served

devicesdevices• Gateway-to-Gateway calls need to be explicitly Gateway-to-Gateway calls need to be explicitly

configured in each gateway to use IP or some configured in each gateway to use IP or some private connection, or use the default of the PSTNprivate connection, or use the default of the PSTN

• The PSTN currently is the glue that allows the The PSTN currently is the glue that allows the VOIP islands to interconnect with each otherVOIP islands to interconnect with each other

The multi-Gateway VOIP The multi-Gateway VOIP WorldWorld

VOIP IslandsVOIP Islands• E.164 numbers are only routable over the PSTNE.164 numbers are only routable over the PSTN• Enterprise or carrier VOIP dialling plans cannot be Enterprise or carrier VOIP dialling plans cannot be

remotely accessed by other VOIP network segmentsremotely accessed by other VOIP network segments

PSTNPSTN

Internet

The Core ENUM ProblemThe Core ENUM Problem

How can a VOIP gateway find out dynamically:How can a VOIP gateway find out dynamically:• If a telephone number is reachable as an Internet If a telephone number is reachable as an Internet

device?device?• And if so, what’s its Internet service address?And if so, what’s its Internet service address?

PSTNPSTN

Internet

Problem statements for ENUM Problem statements for ENUM (1)(1)

1.1. How do network elements How do network elements (gateways, SIP servers etc) find (gateways, SIP servers etc) find services on the Internet if you services on the Internet if you only have a telephone (E.164) only have a telephone (E.164) number?number?

Problem statements for ENUM Problem statements for ENUM (2)(2)

2.2. How can subscribers define their How can subscribers define their preferences for nominating preferences for nominating particular services and servers to particular services and servers to respond to incoming respond to incoming communication requests?communication requests?

The ENUM ObjectiveThe ENUM Objective

Allow any IP device to establish whether Allow any IP device to establish whether an E.164 telephone address is reachable an E.164 telephone address is reachable as an Internet-described Serviceas an Internet-described Service• And … what the preferred Service Point And … what the preferred Service Point

actually isactually is• And if its an Internet-reachable Service And if its an Internet-reachable Service

Point… what IP address, protocol address, Point… what IP address, protocol address, port address and application address should port address and application address should be used to contact the preferred Service be used to contact the preferred Service PointPoint

ENUM ResolutionENUM Resolution

The PSTN is a multi-service platform To emulate this in IP, IP services associated with a

single E.164 may be provided on a collection of different IP service points

An ENUM DNS request should return the entire set of service points and the associated service.

DNS Selection DNS Connection

E.164 address Set of URIs....

URI IP AddressTCP/UDP PortProtocol Address

Why URIs?Why URIs?

URIs represent a generic naming scheme URIs represent a generic naming scheme to describe IP service pointsto describe IP service points• Generic format ofGeneric format of

service:service-specific-addressservice:service-specific-address

A URI in IP context is ultimately resolvable A URI in IP context is ultimately resolvable toto

transport protocol (TCP/UDP) selectiontransport protocol (TCP/UDP) selectionIP addressIP addressPort addressPort addressAddress selector within the application sessionAddress selector within the application session

The Longer TermThe Longer Term

Telephone numbers are well Telephone numbers are well accepted identifiers within their accepted identifiers within their realm of applicationrealm of application

Any collection of service URIs can be Any collection of service URIs can be linked against an ENUM entrylinked against an ENUM entry• mail, www, irc, sms,…mail, www, irc, sms,…

E.164 as a common address E.164 as a common address substrate ?substrate ?

Use this number for any service+61 2 12345678

ENUM

sip:gih@sip.telstra.net

tel:+61 2 62486165

mailto:gih@telstra.net

tel:+61 2 12345678

Practical IssuesPractical Issues

Issues where the IETF has an active Issues where the IETF has an active interest…interest…• Who should manage the e164.arpa zone?Who should manage the e164.arpa zone?• Should there be one root for a single Should there be one root for a single

ENUM database or multiple databases for ENUM database or multiple databases for different functions, number ranges, area different functions, number ranges, area codes or even numbers?codes or even numbers?

• How to secure the DNS to ensure that How to secure the DNS to ensure that ENUM answers are valid, timely and ENUM answers are valid, timely and authoritativeauthoritative

Practical IssuesPractical Issues

Issues where the IETF has a limited (if any) Issues where the IETF has a limited (if any) role to play in ENUMrole to play in ENUM• How to protect the privacy of the ENUM database?How to protect the privacy of the ENUM database?• How to verify changes to the ENUM database?How to verify changes to the ENUM database?• Should telephone number holders ‘opt-in’ or ‘opt-Should telephone number holders ‘opt-in’ or ‘opt-

out’ of the system?out’ of the system?• Portability and ownership of a phone number?Portability and ownership of a phone number?

• Can I cancel all phone services and keep my phone Can I cancel all phone services and keep my phone number?number?

• Compliance with legislative frameworkCompliance with legislative framework• What is a “public telephone call” from a strict regulatory What is a “public telephone call” from a strict regulatory

perspective?perspective?• Is there a valid need for yet another public identity space?Is there a valid need for yet another public identity space?