How to get DID local numbers (IP Telephony)

Jay Ashworth jra at
Thu Dec 6 20:10:19 UTC 2012

----- Original Message -----
> From: "Сергей Харламов" <mentax at>

> Can someone explain me how can I get an block of DID (Telephony
> numbers)? For example I need 200 numbers. Is that special organization
> or I must buy it somewhere?
> What the rule for USA (NY) about telephony providing ? Should I have a
> licence to sale ip telephony?

DID numbers are actually E.164 addresses, which are relevant in the context
of the IPSTN.  Because they are addresses on a specific network, in order
to have some assigned to you, you need to have a connection to that network.

Generally, that connection is either via SIP+RTP over IP to a VoIP gateway
provider, who in turn connects to the PSTN using PRI trunks to their
supplier's switch, or who is themselves the operator of a switch which is
connected to the PSTN by SS7... or you yourself do one of those two things,
in (very) roughly increasing order of cost.

We'll assume for the moment, that you do not want to become a CLEC.

(The rest of this message is even more USAdian than the first part.)

To get DID numbers in a given area, you need to purchase connectivity
service from a telco or gateway provider with physical facilities in that
area.  On the VoIP side, it's common for the "DID" to be the actual thing
you purchase, and the transport and minutes (if any) come along with it.

If you're buying a local PRI circuit to a local RBOC/CLEC, then "blocks" 
of DID's are something you buy at extra cost, and you tell the telco how 
to group the channels on your PRIs, and which DIDs to route to which 

In both cases, outbound-only service is possible to buy, so the DID(s)
are actually optional.

In short, though, if you have physical gear in the US somewhere, you
can buy a PRI and put DIDs on it; if you don't, you can contract with
one or more VoIP providers who do, and backhaul the traffic that way.

If you ever decide you have to switch the DIDs to a different carrier,
you will find that this is easier and harder depending on whom you're 
working with; I don't think there's a rule.

Did that help?

-- jra

Jay R. Ashworth                  Baylink                       jra at
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates         2000 Land Rover DII
St Petersburg FL USA               #natog                      +1 727 647 1274

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