An IETF view of ENUMAn IETF view of ENUM

Geoff HustonGeoff HustonExecutive Director,Executive Director,

Internet Architecture BoardInternet Architecture Board

PresentedPresented at ICANN, Rio de at ICANN, Rio de JanieroJaniero, 2003, 2003byby Richard StastnyRichard Stastny

Who is the IETF?Who is the IETF?

Internet Engineering Task ForceInternet Engineering Task ForceThe organization that oversees the standards The organization that oversees the standards process for Internet protocols and technologiesprocess for Internet protocols and technologiesIndustryIndustry--based standards body with broad based standards body with broad participation from vendors, operators and participation from vendors, operators and researchersresearchersWe make standards that work We make standards that work –– how you work how you work them is up to you!them is up to you!

The Structure of the IETFThe Structure of the IETF

Huh? Huh? -- Lets see that again!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 interoperabilThe IETF has a focus on developing standards where interoperability testing ity testing of conformant implementations of the standard, and use of the teof conformant implementations of the standard, and use of the technology chnology in production contexts form an integral part of the standards prin production contexts form an integral part of the standards processocess

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

Proposed work items are aired at a BOF sessionProposed work items are aired at a BOF session•• 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 WG Chair(sChair(s) and Area Director) and Area Director•• Working Group statement of activityWorking Group statement of activity•• Schedule of milestonesSchedule of milestones

•• Periodic IESG review and Periodic IESG review and recharterrecharter as necessaryas necessary

IETF DocumentsIETF Documents

Internet DraftsInternet Drafts

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

•• draftdraft--<person><person>--<header><header>

•• Working Group DocumentsWorking Group Documents•• draftdraft--ietfietf--<working group><working group>--<header><header>•• Working Group documents denote some level of Working Group documents denote some level of ‘‘buybuy--inin’’ from the from the

community of interestcommunity of interest

IETF DocumentsIETF Documents

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

•• Proposed (good idea, clearly written, Working Group approved, Proposed (good idea, clearly written, Working Group approved, peer reviewed)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 Because tpc.inttpc.int did not work!did not work!•• tpc.inttpc.int (c 1992) mapped E.164 numbers to A records (IP (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 Each new service required a new E.164 --> IP address mapping> IP address mapping•• 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 out ENUM is part of a broader IETF approach of splitting out the components of VOIP / PSTN interaction into discrete the components of VOIP / PSTN interaction into discrete efforts and addressing each component as a discrete efforts and addressing each component as a discrete technology standardization efforttechnology standardization effortENUM 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 Each mapping can be associated with a collection of URIsURIs•• 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 with Each end point of the DNS hierarchy populates the entry with

desired service entriesdesired service entries•• Each application selects compatible service entries from the setEach application selects compatible service entries from the set•• ENUM is independent of directory, call control, routing and ENUM is independent of directory, call control, routing and

transport considerationstransport considerations•• Its just a mapping from the E.164 domain into multiple URI Its just a mapping from the E.164 domain into multiple URI

service domainsservice domains

The Not So Good BitThe Not So Good Bit

The DNS is an issue in The DNS is an issue in itselfitself…………•• 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 There is no ““DNS says DNS says ‘‘nono’”’”, only an indistinct timeout, only an indistinct timeout•• Putting regular expressions in the DNS is an fascinating complicPutting regular expressions in the DNS is an fascinating complicationation•• 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 spaceRemember: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 it in the DNSjust put it in the DNS””. Be very concerned whenever you hear this!. 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 from All ENUM is a distributed partial mapping from E.164 addresses into a set of service points E.164 addresses into a set of service points identified via a URI identified via a URI labellinglabelling

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 architecturereference architecture’’ENUMENUM’’ss core reference architecture is VOIPcore reference architecture is VOIP--toto--VOIPVOIP

PSTNPSTN

Internet

VOIP Server

VOIP Served subnet

EnumService 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 mapping A PSTN / IP gateway maintains a mapping

between IP and E.164 addressesbetween IP and E.164 addresses

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 multiThe multi--Gateway VOIP WorldGateway VOIP World

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

set of served IP service addressesset of served IP service addresses•• Each Gateway knows only about locally served Each Gateway knows only about locally served

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

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

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

The multiThe multi--Gateway VOIP WorldGateway VOIP World

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

accessed by other VOIP network segmentsaccessed 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 device?If a telephone number is reachable as an Internet device?•• And if so, whatAnd if so, what’’s its Internet service address?s its Internet service address?

PSTNPSTN

Internet

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

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

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

2.2. How can subscribers define their How can subscribers define their preferences for nominating particular preferences for nominating particular services and servers to respond to services and servers to respond to incoming communication requests?incoming 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 Internetas an Internet--described Servicedescribed Service•• And And …… what the preferred Service Point what the preferred Service Point

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

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

ENUM ResolutionENUM Resolution

The PSTN is a multi-service platformTo emulate this in IP, IP services associated with a single E.164 may be provided on a collection of different IP service pointsAn 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 Why URIsURIs??

URIsURIs represent a generic naming scheme to represent a generic naming scheme to describe IP service pointsdescribe IP service points•• Generic format ofGeneric format of

service:serviceservice:service--specificspecific--addressaddress

A URI in IP context is ultimately resolvable toA URI in IP context is ultimately resolvable totransport 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 accepted Telephone numbers are well accepted identifiers within their realm of applicationidentifiers within their realm of applicationAny collection of service Any collection of service URIsURIs can be can be linked against an ENUM entrylinked against an ENUM entry•• mail, www, mail, www, ircirc, , smssms,,……

E.164 as a common address substrate ?E.164 as a common address 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 interestinterest……•• Who should manage the e164.arpa zone?Who should manage the e164.arpa zone?•• Should there be one root for a single ENUM Should there be one root for a single ENUM

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

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

Practical IssuesPractical Issues

Issues where the IETF has a limited (if any) role Issues where the IETF has a limited (if any) role to play in ENUMto 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 Should telephone number holders ‘‘optopt--inin’’ or or ‘‘optopt--outout’’

of the system?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 number?Can I cancel all phone services and keep my phone number?

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