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Unread 01-03-2008, 08:52 PM   #1
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Default Issues with toll free numbers

Recently I found that I could not dial toll free numbers in The Netherlands (for example +31-800-0429). Voxalot does an ENUM lookup for this number and returns But the call failed. I got an error "503 Service Unavailable", "No route to destination".

It turns out that routes every toll free number in The Netherlands to Same thing for other countries. UK toll free numbers for example are routed through 3 providers:, and But only the last one worked for me. This means that companies like and offer to route toll free calls but they do not live up to their promises.

I exchanged a couple of mails with Duane (aka evilbunny) of Here are some of my observations:
  • Being able to call toll free numbers through SIP is a great benefit to people living outside those particular countries. Voxalot and make this an almost transparent procedure.
  • Unfortunately some providers do not live up to their promises. This makes it a bit less transparent and it could result in a bad Voxalot/ user experience (I had to add an extra rule to my dial plan disabling ENUM for toll free numbers in The Netherlands).
  • A solution would be to regularly check if providers are still routing toll free traffic as they originally promised. already sends "SIP probes" to weed out problematic entries from its database. I can only assume that toll free providers are currently exempt from these probes.
  • According to the FAQ, "providers offering toll free calls get paid per minute to terminate your calls to the phone network". So it is in their best interest to provide a good service. (Temporarily) dropping them from the database will probably speed this up.
  • Technically these providers are not the real owners of the toll free numbers. The numbers have probably not been verified like the other numbers in the database. A couple of days ago MarkosJal wanted to know how to register hundreds of numbers on There was no reply but I think it is a similar situation as with the toll free providers.
  • So here is a fundamental question: who decides who is authorative for these numbers? What if there are providers with more nefarious intentions? For example, Airbus could start a provider and offer to route calls to Boeing "for free". And the United States could do the same for calls to Iran. (Ok, these are far fetched examples but you get my idea).
  • Owners of toll free numbers can actually add their own SIP address to the database, overriding the route to the default provider(s). I don't know if there are toll free number owners who do this. It would save them some money, although it is probably small change considering the current number of users.
  • could offer an optional "strict" mode in which only numbers that have actually been verified are resolved. I assume that this is the method used by the other ENUM roots (,, etc.).
  • Your VoIP service provider such as Voxalot or Pennytel could decide to route toll free calls itself, for example using SIPbroker instead of ENUM. A call to +44-800-xxxx would then go to *883844800xxxx. ENUM has the advantage that it is based on DNS so it is more distributed than a SIPbroker lookup.

Any other thoughts on this?
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