How does DID works?

[renesaure]

hi everybody,

i'd been hearing about this DID numbers in almost all VOiP Forums. what i know about DID is what we have in the office PABX wherein we have direct inward dialing. But i guess that's not the one huh.

How do you set this up in your network? and what kinds of hardware software do you need to make this work? can you do it all your own network or do you need to have a carrier to work with? thanks guys.

[renesaure]

hi everybody,

im a newbie here. i'd been hearing all about this DID numbers. Basically (technically) how does this works? do you need special hardware/software for this? do i need to have a partnership with a local ISP/telco or can i make my own network?

thanks

[humba3]

A DID is a real phone number, one that can be called from anyplace in the world. Some providers incorrectly call these numbers "virtual numbers" but there's nothing virtual about them.
Some IPTSPs also have internal numbers (e.g. FWD). An internal number is a number that only works in the network of your IPTSP.
To better illustrate the difference, here's an example:

You buy a cellphone from Verizon. If Verizon were an IPTSP offering just private numbers, you'd only be able to call other Verizon subscribers. You can't call anybody signed up with AT&T, T-Mobile, etc. You can also not call abroad.

Now suppose Verizon connects their network with the one from T-Mobile. Verizon subscribers can now call T-mobile subscribers by dialling a prefix and the number of the T-mobile subscriber (e.g. 10 + T-mobile number), and T-mobile subscribers can call Verizon subscribers by dialling 20 + Verizon mobile number.

You can see this in the IPTSP world where two or more IPTSPs partner up.. e.g. some IPTSPs allow their subscribers to call FWD.

Now enter DIDs: If Verizon decides to connect their network to the national telephony network (which in turn has international uplinks), people from all over can call you. If you have a DID, people will dial that DID number and be directly connected to you. If you do not have a DID, people wishing to call you will have to call the Verizon operator, and ask to be connected with your Verizon extension (or there's an automated attendant).

In the traditional telephony world, if you sign up with Verizon, T-Mobile, AT&T, etc, you get a DID. In the business world, your company might decide to only get a limited number of DIDs (each number costs a certain amount per month), so if your wife wants to call you, she'll have to call the company front desk, and ask the receptionist to speak to you (extension 1234 or whatnot). If you have a DID at work, your wife can call you directly.

In the IPTSP world, IPTSPs buy DID numbers from exchanges all over the country, then route those to their subscribers.. that's how you can sit in New York and get an LA number. If somebody calls that number, it will be routed to the PSTN gateway of your IPTSP, and from there it gets to you via IP link.

There are IPTSPs that do not even have private numbers, but where calling somebody signed up with the same IPTSP (and he might have a number in another part of the country.. it doesn't matter), will still not cost you anything. That's because when you dial the number, your IPTSP will look at it, then decide where the call has to go. If it's a number that belongs to the provider, it will be routed internally, if it's another number, it goes through the PSTN gateway.

As a end user, if you want VoIP with a DID number, just sign up with a provider that offers one.. that's it takes. For you as a user, there's no difference whatsoever

[eric]

Direct-Inward-Dial (DID) numbers are inbound phone numbers issued by the phone company and can be assigned to one or more trunks.

The idea being that you have X number of connections (POTS or VOIP) in from the phone company and Y phone numbers (DID) assigned to those connections (like one for every employee).

Usually Y > X and so the phone company sends the DID information with the call such that the PBX can figure out how to route the call.

In the consumer VoIP space, most of our forum members are getting single DID numbers near friends and family, so the friends and family can dial a local number (pay local rates) and the call is routed via VoIP anywhere globally.

In the US, the calling party pays for the call, so many VoIP providers and CLEC's offer PSTN DID's to VoIP for free, since they are paid (a really small amount per call) for each call they terminate and convert to VoIP.