VoIP DID

[flipperza]

Hi

Does anybody know what the legitimacy is in the following scenario:

A company is interconnected, receives a 087....... call from ITSP (interconnected party), company then takes this 087 ... number, manipulates this number to an extension number e.g. 1234 on a PBX, routes this call to the VoIP Gateway where the VoIP Gateway would route the call to the PBX and the extension nr 1234 would ring although 087 ... was dialed.

Has anyone actually done something like this? I guess the invite would look something like this:

INVITE: 087 [email protected]
TO: [email protected]
FROM: [email protected]

 

[s0lar]

Yes, the scenario is legitimate and used extensively daily by many a company.

 

[flipperza]

And the SIP Invite would look something like this:

INVITE: 087 [email protected]
TO: [email protected]
FROM: [email protected]

 

[s0lar]

Yes, if you gateway is in the call-path and doesn't issue a re-invite.

 

[gmza]

This sounds like the exact definition of DID -- Directed Inward Dialling. i.e. Directing the call to the appropriate internal extension.

I can't speak for other ITSPs, but with Switch Telecom if you have more than one DID number associated with the VoIP Trunk, the DID number information is sent through in this sort of manner so that the switchboard can determine which DID was called. No need for special manipulation.

E.g. On Trixbox or 3CX systems, you'd just configure incoming routes for each DID number associated with the trunk.

If you wanted to match to an extension, you'll just tell it to strip the first few digits. e.g. If you have 100 numbers from 0875501200 to 99, just tell it to strip 0875501 to map to extensions 200 through 299.

Off hand, I know Switch Telecom customers doing this with Asterisk (including Trixbox & Elastix), Epygi and 3CX systems. I've also implemented it with a PRI gateway. i.e. We mapped the VoIP DDI's to four digit DID numbers on the gateway and sent these to a traditional switchboard through E1/PRI interface. Similarly this can be done with a BRI gateway, since both ISDN BRI and PRI support DDI.