[VoiceOps] SIP-to-TDM gateway appliance

[Nathan Anderson]

I know this has been a topic of conversation in the past, but things might have changed since the last discussion and I'm wondering what the market is currently like for such devices.

We deliver voice strictly via SIP/RTP, but naturally there are some potential customers out there that still have an older, non-IP-aware PBX that they're not ready to throw out yet.  What are the best and most cost-effective gateway options out there at this time?  We are specifically looking for one that has a single T1 interface that can operate in either CAS or PRI modes.

Special requirements:

1) We need to be able to do DID manipulation between T1 and SIP; I presume this is a rather standard feature in most gateways given that most SIP trunk providers will send at least 10-digit DNIS (in the INVITE and "To" fields) but DNIS on PRI is often only the last 3 or 4 digits of the TN.

2) There may be certain situation where we want to leave the PBX configuration as untouched/unchanged as possible (drop-in replacement service), and where there is no correllation between target DID and the telephone number (e.g., 212-555-1212 is called, PBX is sent 4001).  We'd like a gateway where static mappings like that for DID manipulation are possible, rather than just a general rule that says "strip the first 6 digits off before sending to the PRI".

3) For outgoing calls, the device needs to put the calling DID (the desired Caller-ID/ANI) in the PAI header, and also needs to be able to be configured to override "From" with a static alphanumeric value (so "From" and PAI should not match; "From" will not contain the desired ANI).

4) In T1 CAS singalling modes such as E&M Wink where it is possible to transmit CLID and target DID information via DTMF to the PBX, different PBXes potentially have different formats that they want to see this information in; for example, a Nortel Norstar would expect to see *CALLERID*DNIS* (e.g., *2125550001*1212* where the caller is 212-555-0001 and the destination is 212-555-1212).  Are there any gateways that support this?

5) It needs to have a T.38 gateway mode that can recognize a fax call, either send or accept a re-INVITE with a T.38 SDP as appropriate, and perform the "transcoding" from/to T.38 between the T1 channel and the RTP session.  Just resorting to G.711 for fax passthrough is not desireable...any gateway can do that.

6) If in T1 CAS mode, and the PBX takes a channel "off-hook" to place an outbound call, the gateway should generate an audible dialtone.

...and, of course, it would be nice if we could find such a device < $1,000. :-P

I know I could build one myself with a mini PC and a single-span T1 card that was running Asterisk 10 and easily hit that price point, but I'd rather find a supported, off-the-shelf solution to sell to our customers, if possible.

There are the "usual suspects", of course: AdTran, MediaTrix, AudioCodes, and so forth.  AdTran seems to get talked about a lot here.  Let's say price was no object for a second.  Does anyone know if there is a model amongst any of the ones these manufacturers produce that fulfills the above list of requirements?

Does anybody have any experience with Digium's relatively new line of gateways (G100/G200)?  I think it would support some of these scenarios (#1 and #3) but I'm not sure about the remaining ones.  Unfortunately, although it most certainly runs on an Asterisk core, that core is only exposed to you through a clever but still-limited GUI; with direct access to the dialing plan (extensions.conf) I could accomplish all of these things myself.  The price is certainly right, though.

If only somebody made a reasonably-priced single-board-computer that ran raw, embedded Asterisk and had a single-span T1 interface on it.  Oh wait, somebody does!:

http://switchvoice.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=9&category_id=2&option=com_virtuemart&Itemid=30

http://www.odints.com/pages/prod/completesolutions/alvis-pbx/alvisfs.htm

Only problem is that the first company doesn't have a U.S. distributor, and the second doesn't have a distributor that sells in single-unit quantities.

Would love to hear y'all's thoughts on this subject.

Thanks,

-- 
Nathan Anderson
First Step Internet, LLC
nathana at fsr.com