Why bother with ENUM? {see [Stastny 2004]}

In order for PSTN/IDSN user to call VoIP users, there must be a way of translating an E.164 number to some way of reach the VoIP user.
- Since the PSTN user only has a telephone dialing pad - this limits what they can enter (for example ‘+’ entered as ‘*’).
- However, due to ITU-T Rec. E.105 -- this means that VoIP become a part of the global public telephony service -- hence this translation has to follow at least some of the ITU rules
- Which gateway should be used?
For VoIP users to call a PSTN/ISDN user, caller needs to do an ENUM lookup and utilize a VoIP to PSTN/ISDN gateway
- Which gateway? Can the called user opt-in or opt-out of having calls from the Internet?
VoIP caller to VoIP callee when the caller dials an E.164 number
- Does it get routed to the PSTN and back? {I.e., going through two VoIP gateways!}
Use of Geographic numbers for fixed VoIP terminals
- easily enables 911 like services for their terminals too
(Global | National) [non-geographic] personal numbers
- A personal or global or national number - which can be your single number
…

One problem is that IP communications is not simply IP Telephony, it is VoIP + Chat + Instant Messaging + Video + … .

Slide Notes

R. Stastny, “Numbering for VoIP and other IP Communications”, IETF IETF-Draft, October 2003, Expired: April 2004 http://www.ietf.org/internet-drafts/draft-stastny-enum-numbering-voip-00.txt Links to an external site.

ITU-T,"InternationalTelephoneService",ITU-T recommendation E.105, August 1992

Transcript

[slide220] So the first question, of course, is why... Yes? [student ask: You see some numbers from the United States and they have alphabets. So how do they translate numbers to/from the alphabet?] Because there's basically a mapping. The numbers on the keypad have letters above them. The different letters are simply the particular number associated with that triple of letters. [Student asks: But I haven't seen another country except there. It's only in the United States?] No, there are other countries that had alphabetic labels on their phone number pads. It's just that few other places use it. They just use the digits. But the main reason they were used in the U.S. a lot was because of vanity numbers. You'd have an easy-to-remember number, so you would have your name in your phone number, and you would go to the phone company and say, I'll pay you extra if you assign me this number because it happens to spell out whatever. Free food, whatever. Right? But back to this problem about ENUM. The first question that people ask (or at least I would ask) is, why should I ever want to receive a call from anyone who has a telephone? If they can't send me an e-mail, I don't want to talk to them in any case. So why should I make myself visible in the telephony world and make it available for people to now be able to reach me? You all know that you can have phone numbers that aren't publicly in a directory. But if we have a mapping system, what's to prevent someone from now mechanically with their voice over IP dialing system trying all of those numbers, looking them all up, and finding the translation between numbers and SIP URIs, and now flooding you with phone calls - Wouldn't you like to buy our easy peeler potato peeler or whatever. So there is a problem of privacy here. There is a question about what gateway I Right? Because just because I have a phone number and I now have a mapping to a SIP URI, it doesn't tell me the best way to get to that SIP URI. How do we do the routing when it goes to and from the PSTN? So I might have an entry for both the PSTN telephone and my SIP user agent running for instance in my laptop- Which one do I want the call to go to? Can I control that? Geographic numbers. Right? We know about geographic numbers. They're to a particular place. So services like emergency services, 112 in Sweden, 911 in the U.S., it's important that when you call it, it knows your location so they can dispatch the emergency service to where you are. But does your SIP URI have a geography associated with it? No. So how do you handle those? And then how do you handle non-geographic numbers? And you need some way of being able to specify those. And I should say one of the things that really changed tremendously was the regulators in the state of Illinois in the U.S. looked at the statistics of how often non-geographic numbers were used -- free phone numbers. And when those numbers are dialed, what has to happen? You need to look in a database to see where do you really route that call. And what they found out was half of all telephone calls were made to those type of numbers. And they basically told the operators, hey, if can look up half of them then look the other half and then we can have complete number portability. Right? So if you have to do a database lookup to figure out where to route the call, just do it for every call that's dialed.