The topic of ENUM came up last night at the Manitoba Asterisk User’s group meeting. I find the discussion interesting because there are a couple of people there who are involved with the ENUM efforts by CIRA. After discussing the problems and status of ENUM-Canada efforts, I started to wonder, “Do we really need ENUM?”

ENUM is a method for mapping PSTN style phone numbers to a URI, such as SIP or a mailto, through the global DNS. My office phone, 204.975.5987, would then become 7.8.9.5.5.7.9.4.0.2.1.e164.arpa by reversing the digits, adding the top level country code of 1, and looking within the e164.arpa zone. Simplifying greatly, the response might either be nothing, meaning I can’t be reached by IP, or it might be something like sip:seanwalberg@ceridian.ca, meaning that I can be reached via SIP through that address.

One consumer of this information would be telecos. Rather than paying my carrier (MTS/Allstream) for terminating the call, they could use the sip URI to call me over the Internet and pocket the difference. The other would be regular people who are replacing their phones with either computers or smarter IP phones, and want to make the query themselves to avoid paying long distance.

Almost two years ago I wrote Either you’ve got a SIP address, or you’re not worth talking to to point out that the eventual goal will be phasing out of PSTN style numbers in favour of SIP URIs, which are basically email addresses.

Since telephones with their 12 buttons aren’t too good at entering SIP URIs such as “seanwalberg@ceridian.ca”, ENUM is one transition mechanism. But involve telecos and large committees, and you get delay and disagreements. Already there are two types of ENUM being proposed, one for carriers, one for the public. And since DNS is delegated differently than PSTN numbers, how does a regular person like me update my records securely (while making sure that an evil person can’t update my records?)

So this led me to think, “Why do we even need ENUM?”. Why not put a SIP address on your business card along with all the other numbers people put there? (Don’t quote me, but I remember Nortel did this) People who want to use SIP will use SIP. People who can’t won’t.

From the carrier perspective, if they’re so interested in saving money by offloading calls to the Internet, why not let them come up with their own transition mechanism? They’ve done this before for toll free and local number portability.

I suppose what I’m really saying is that the problem isn’t so much technical as it is marketing. How many people have some form of instant messaging client, or even several? What would it take people to move to a SIP based client? If people started using SIP based instant messaging, or even if it were supported under popular IM clients (didn’t MSN support it for a brief period), wouldn’t vendors have incentive to make hard phones capable of dialing SIP? (I pointed out last night that a small keypad was no impediment to the adoption of SMS messaging)

While I applaud the efforts of those involved with ENUM, I wonder if it wouldn’t be easier just to draw a line in the sand and not try and integrate the two networks. Instead, focus on promoting the SIP network, and let the benefits and features draw people in.